Stationary source emissions -- Sampling and determination of mercury compounds in flue gas using gold amalgamation trap

This document describes a method for the sampling and measurement of mercury of both vapour and solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg0) and oxidized (Hg2+) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous) mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures only gaseous elemental mercury, the oxidized mercury (Hg2+) in the vapour phase is converted to elemental mercury (Hg0) prior to the gold amalgamation trap. The concentration of gaseous mercury is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS) after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold vapour AFS after dissolving the particulate mercury into solution. The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate mercury concentrations. The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury ranging from 0,01 μg/m3 to 100 μg/m3 with sampling volumes from 0,005 m3 to 0,1 m3 and sample gas flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically from 0,01 μg/m3 to 100 μg/m3 with sampling volume from 0,05 m3 to 1 m3.

Émissions de sources fixes -- Échantillonnage et détermination de la teneur en mercure dans les gaz de combustion en utilisant un piège d’amalgamation avec de l’or

Le présent document décrit une méthode de prélčvement et de mesurage du mercure en phase vapeur et en phase solide dans les effluents gazeux des sources fixes. Le mercure existe généralement sous forme élémentaire (Hg0) et oxydée (Hg2+), ŕ la fois en phase vapeur et en phase solide, dans les effluents gazeux. Le mercure en phase vapeur (gazeux) est collecté par échantillonnage isocinétique ou non isocinétique avec un pičge d'amalgamation composé d'or aprčs élimination du mercure en phase solide (particulaire) ŕ l'aide d'un filtre. Le pičge d'amalgamation avec de l'or collectant uniquement le mercure élémentaire gazeux, le mercure oxydé (Hg2+) est converti en mercure élémentaire (Hg0) en phase vapeur, avant le pičge d'amalgamation. La concentration en mercure gazeux est déterminée par spectrométrie d'absorption atomique (AAS) ou par spectrométrie de fluorescence atomique (AFS) aprčs relargage du mercure par chauffage du pičge d'amalgamation avec de l'or. Parallčlement, le mercure particulaire est collecté par échantillonnage isocinétique sur un filtre et sa concentration est déterminée par spectrométrie d'absorption atomique ŕ vapeur froide (CVAAS) ou par spectrométrie de fluorescence atomique ŕ vapeur froide (CVAFS) aprčs mise en solution du mercure particulaire. La concentration totale en mercure dans l'effluent gazeux est exprimée sous forme de somme des concentrations en mercure gazeux et en mercure particulaire. La méthode d'amalgamation avec de l'or est destinée aux mesurages ŕ court terme (périodiques) du mercure gazeux dans une plage de concentration de 0,01 μg/m3 ŕ 100 μg/m3 avec des volumes de prélčvement compris entre 0,005 m3 et 0,1 m3 et un débit de gaz prélevé compris entre 0,2 l/min et 1 l/min. La plage de mesurage du mercure particulaire s'étend généralement de 0,01 μg/m3 ŕ 100 μg/m3 avec des volumes de prélčvement compris entre 0,05 m3 et 1 m3.

Emisije nepremičnih virov - Vzorčenje in določevanje živosrebrovih spojin v odpadnih plinih z amalgamacijo na zlatih pasteh

General Information

Status
Published
Publication Date
18-Nov-2020
Current Stage
5060 - Close of voting Proof returned by Secretariat
Start Date
14-Oct-2020
Completion Date
13-Oct-2020

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SLOVENSKI STANDARD
SIST ISO 21741:2021
01-maj-2021
Emisije nepremičnih virov - Vzorčenje in določevanje živosrebrovih spojin v
odpadnih plinih z amalgamacijo na zlatih pasteh

Stationary source emissions - Sampling and determination of mercury compounds in flue

gas using gold amalgamation trap

Émissions de sources fixes - Échantillonnage et détermination de la teneur en mercure

dans les gaz de combustion en utilisant un piège d’amalgamation de l’or
Ta slovenski standard je istoveten z: ISO 21741:2020
ICS:
13.040.40 Emisije nepremičnih virov Stationary source emissions
SIST ISO 21741:2021 en,fr

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
SIST ISO 21741:2021
---------------------- Page: 2 ----------------------
SIST ISO 21741:2021
INTERNATIONAL ISO
STANDARD 21741
First edition
2020-11
Stationary source emissions —
Sampling and determination of
mercury compounds in flue gas using
gold amalgamation trap
Émissions de sources fixes — Échantillonnage et détermination de la
teneur en mercure dans les gaz de combustion en utilisant un piège
d’amalgamation de l’or
Reference number
ISO 21741:2020(E)
ISO 2020
---------------------- Page: 3 ----------------------
SIST ISO 21741:2021
ISO 21741:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
SIST ISO 21741:2021
ISO 21741:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 4

5 Principle ........................................................................................................................................................................................................................ 4

6 Reagents ........................................................................................................................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Water ............................................................................................................................................................................................................... 5

6.3 Nitric acid .................................................................................................................................................................................................... 5

6.4 Sulfuric acid ............................................................................................................................................................................................... 5

6.5 Stannous chloride solution ........................................................................................................................................................... 5

6.6 Phosphate buffer solution ............................................................................................................................................................. 5

6.7 Hydrofluoric acid .................................................................................................................................................................................. 5

6.8 Hydrochloric acid .................................................................................................................................................................................. 5

6.9 Mercury stock solution .................................................................................................................................................................... 5

6.10 Rinse solution .......................................................................................................................................................................................... 5

6.11 Sample gas drying agent ................................................................................................................................................................. 5

6.12 Trapping agent of mercury ........................................................................................................................................................... 6

7 Apparatus ..................................................................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.1.1 Main-stream sampling ................................................................................................................................................ 6

7.1.2 Side-stream sampling .................................................................................................................................................. 8

7.2 Nozzle.............................................................................................................................................................................................................. 9

7.3 Filter and filter housing ................................................................................................................................................................... 9

7.4 Transfer line ...........................................................................................................................................................................................10

7.5 Pretreatment unit ..............................................................................................................................................................................10

7.6 Gold amalgamation trap...............................................................................................................................................................11

7.7 Drying unit ...............................................................................................................................................................................................11

7.8 Suction unit .............................................................................................................................................................................................11

7.9 Thermometer ........................................................................................................................................................................................11

7.10 Manometer ..............................................................................................................................................................................................12

7.11 Gas meter ..................................................................................................................................................................................................12

7.12 Flowmeter ................................................................................................................................................................................................12

7.13 Barometer ................................................................................................................................................................................................12

8 Sampling .....................................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling position and sampling point ............................................................................................................................12

8.3 Sampling duration and sample volume ..........................................................................................................................12

8.4 Other measurements to be made prior to sampling ...........................................................................................13

8.4.1 Volumetric gas flow through duct at the sampling plane ..........................................................13

8.4.2 Moisture content of gas ...........................................................................................................................................13

8.4.3 Oxygen content of gas ...............................................................................................................................................13

8.5 Assembly of sampling apparatus .........................................................................................................................................13

8.6 Sampling ....................................................................................................................................................................................................13

8.7 Checking for leaks .............................................................................................................................................................................14

8.8 Quality assurance...............................................................................................................................................................................14

8.9 Sample recovery .................................................................................................................................................................................14

© ISO 2020 – All rights reserved iii
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SIST ISO 21741:2021
ISO 21741:2020(E)

8.10 Reagent blank........................................................................................................................................................................................15

8.11 Field blank ...............................................................................................................................................................................................15

9 Sample preparation ........................................................................................................................................................................................15

9.1 General ........................................................................................................................................................................................................15

9.2 Sample preparation for particulate mercury analysis .......................................................................................15

10 Analytical procedure .....................................................................................................................................................................................16

10.1 Analytical procedure for mercury collected with gold amalgamation trap ....................................16

10.2 Analytical procedure for mercury in rinse solution and digested solution .....................................17

11 Expression of results .....................................................................................................................................................................................17

11.1 Calculation of the volume of dry flue gas sampled at sampling conditions ....................................17

11.2 Calculation of the volume of dry flue gas sample normalized to standard

temperature and pressure .........................................................................................................................................................18

11.3 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP ...............................................................................................................................................................................18

11.4 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP and reference oxygen volume fraction ..............................................................................20

11.5 Rate of mass discharge of mercury expressed as elemental mercury .................................................20

11.6 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP ..............................................................................................................................................................................20

11.7 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP and reference oxygen concentration ..................................................................................21

12 Performance characteristics .................................................................................................................................................................21

12.1 Detection limits ...................................................................................................................................................................................21

12.2 Evaluation of measurement uncertainty .......................................................................................................................21

13 Test report ................................................................................................................................................................................................................22

Annex A (informative) Preparation of mercury reference gas ...............................................................................................24

Annex B (informative) Results of evaluation of measurement uncertainties.........................................................27

Annex C (informative) Comparison of analytical results obtained with heated solid catalytic

reduction unit and stannous chloride solution unit ....................................................................................................29

Annex D (informative) Comparison of analytical results obtained with this method and

EN 13211 ....................................................................................................................................................................................................................31

Annex E (informative) Interference from sulfur dioxide (SO ) on the recovery of elemental

mercury and oxidized mercury ..........................................................................................................................................................33

Bibliography .............................................................................................................................................................................................................................35

iv © ISO 2020 – All rights reserved
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SIST ISO 21741:2021
ISO 21741:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 1,

Stationary source emissions.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2020 – All rights reserved v
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SIST ISO 21741:2021
ISO 21741:2020(E)
Introduction

Because mercury is exhausted from stationary sources such as coal combustion plants, cement kilns,

non-ferrous metal smelting operations and roasting plants, and waste incineration facilities, the

monitoring of the stationary source mercury mass emissions is increasingly important for preventing

global environmental pollution and health damage caused by mercury.

This document describes a method for the sampling and determination of mercury concentrations

in a flue gas passing through ducts or chimney stacks. Mercury generally exists as elemental (Hg )

and oxidized (Hg ) forms, both in vapour and in solid phases in flue gases, this method allows the

determination of both total vapour-phase mercury and total solid-phase mercury concentrations in

flue gases.
vi © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
SIST ISO 21741:2021
INTERNATIONAL STANDARD ISO 21741:2020(E)
Stationary source emissions — Sampling and
determination of mercury compounds in flue gas using
gold amalgamation trap
1 Scope

This document describes a method for the sampling and measurement of mercury of both vapour and

solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg ) and

oxidized (Hg ) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous)

mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after

removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures

only gaseous elemental mercury, the oxidized mercury (Hg ) in the vapour phase is converted to

elemental mercury (Hg ) prior to the gold amalgamation trap. The concentration of gaseous mercury

is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS)

after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is

collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold

vapour AFS after dissolving the particulate mercury into solution.

The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate

mercury concentrations.

The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury

3 3 3 3

ranging from 0,01 μg/m to 100 μg/m with sampling volumes from 0,005 m to 0,1 m and sample gas

flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically

3 3 3 3
from 0,01 μg/m to 100 μg/m with sampling volume from 0,05 m to 1 m .
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 9096, Stationary source emissions — Manual determination of mass concentration of particulate matter

ISO 10396, Stationary source emissions — Sampling for the automated determination of gas emission

concentrations for permanently-installed monitoring systems

ISO 12141, Stationary source emissions — Determination of mass concentration of particulate matter

(dust) at low concentrations — Manual gravimetric method

ISO 12846:2012, Water quality — Determination of mercury — Method using atomic absorption

spectrometry (AAS) with and without enrichment

ISO 16911-1, Stationary source emissions — Manual and automatic determination of velocity and volume

flow rate in ducts — Part 1: Manual reference method

ISO 17852:2006, Water quality — Determination of mercury — Method using atomic fluorescence

spectrometry
ISO 20988, Air quality — Guidelines for estimating measurement uncertainty
© ISO 2020 – All rights reserved 1
---------------------- Page: 9 ----------------------
SIST ISO 21741:2021
ISO 21741:2020(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gaseous mercury

mercury existing both as elemental and oxidized forms passing through a filter having at least 99,5 %

collection efficiency for 0,3 μm diameter particles
3.2
particulate mercury

mercury existing both as elemental and oxidized forms contained in a solid phase particle collected by

a filter having at least 99,5 % collection efficiency for 0,3 μm diameter particles

3.3
isokinetic sampling

sampling at a flow rate such that the velocity and direction of the gas entering the sampling nozzle are

the same as those of the gas in the duct at the sampling point (3.4)
3.4
sampling point
specific position on the sampling section at which a sample is extracted
3.5
STP
standard conditions for temperature, 273,15 K, and pressure, 101,325 kPa
4 Symbols and abbreviated terms
4.1 Symbols
M amounts of mercury in the first gold amalgamation trap (μg)
A1,Hg
M amounts of mercury in the second gold amalgamation trap (μg)
A2,Hg

C concentration of mercury in a prepared sample of rinse solution that washed the transfer

R,Hg

line from the filter housing to the impinger nozzle of stannous chloride solution or the inlet

of catalytic reduction unit in main-stream sampling (μg/ml). Ref. Figure 1 and 2.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R1,Hg

from the filter housing to the T-piece in side-stream sampling (μg/ml). Ref. Figure 3.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R2,Hg

after the T-piece to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in side-stream sampling (μg/ml). Ref. Figure 3.
C concentration of mercury in a prepared sample solution for particulate mercury
S,Hg
analysis (μg/ml)
d density of reagent solution (g/ml)
p atmospheric pressure (kPa)
atm
2 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
SIST ISO 21741:2021
ISO 21741:2020(E)

p average pressure difference between the sample gas before the gas meter and the

atmosphere (kPa)
q rate of mass discharge of mercury expressed as elemental mercury (mg/s)
m,Hg

q volume flow rate of flue gas through the sampling plane at conditions i of temperature,

V,fg,i
pressure, moisture and oxygen content (m /s)
T average temperature of the sample gas before the gas meter (K)
u(y) standard uncertainty (μg/m )
V volume of dry flue gas sample normalized to STP (m )
V final gas meter reading at the end of sampling (m )

V volume of dry flue gas sample for gaseous mercury analysis normalized to STP (m )

G,d
V initial gas meter reading at the beginning of sampling (m )

V volume of air drawn through the gas meter during any intermediate leak tests (m )

V volume of dry flue gas sample (m )

V volume of dry flue gas sample in main stream, normalized to STP, in side-stream

main,d
sampling (m )

V volume of dry flue gas sample for particulate mercury analysis normalized to STP (m )

S,d

V volume of dry flue gas sampled in side stream, normalized to STP, in side-stream

side,d
sampling (m )

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in main-stream sampling (ml). Ref. Figure 1 and 2.

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the T-piece in side-stream sampling (ml). Ref. Figure 3.

v volume of a recovered sample of rinse solution that washed transfer line after the T-piece to

the impinger nozzle of stannous chloride solution or the inlet of catalytic reduction unit in

side-stream sampling (ml). Ref. Figure 3.
v volume of a prepared sample solution for particulate mercury analysis (ml)

w average moisture content of the flue gas at the sampling plane during the sampling period (%)

y j th concentration value of the first measuring system (μg/m )
1,j
y j th concentration value of the second measuring system (μg/m )
2,j

ρ mass concentration of gaseous mercury expressed as elemental mercury in the flue gas on a

G,Hg,dry
dry basis at STP (μg/m )

ρ mass concentration of particulate mercury expressed as elemental mercury in the flue gas

S,Hg,dry
on a dry basis at STP (μg/m )

ρ mass concentration of total mercury expressed as elemental mercury in the flue gas on

Hg,dry
a dry basis at STP (μg/m )
© ISO 2020 – All rights reserved 3
---------------------- Page: 11 ----------------------
SIST ISO 21741:2021
ISO 21741:2020(E)

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a dry

Hg,dry,O
basis at STP and reference oxygen concentration (μg/m )

ρ mass concentration of mercury expressed as elemental mercury at conditions i of

Hg,i
temperature, pressure, oxygen and moisture conditions (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet
basis at STP (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet,O
basis at STP and reference oxygen concentration (μg/m )
φ volume fraction of the oxygen on a dry basis measured during the
...

SLOVENSKI STANDARD
oSIST ISO 21741:2021
01-februar-2021
Emisije nepremičnih virov - Vzorčenje in določevanje živosrebrovih spojin v
odpadnih plinih z amalgamacijo na zlatih pasteh

Stationary source emissions - Sampling and determination of mercury compounds in flue

gas using gold amalgamation trap

Émissions de sources fixes - Échantillonnage et détermination de la teneur en mercure

dans les gaz de combustion en utilisant un piège d’amalgamation de l’or
Ta slovenski standard je istoveten z: ISO 21741:2020
ICS:
13.040.40 Emisije nepremičnih virov Stationary source emissions
oSIST ISO 21741:2021 en,fr

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------
oSIST ISO 21741:2021
---------------------- Page: 2 ----------------------
oSIST ISO 21741:2021
INTERNATIONAL ISO
STANDARD 21741
First edition
2020-11
Stationary source emissions —
Sampling and determination of
mercury compounds in flue gas using
gold amalgamation trap
Émissions de sources fixes — Échantillonnage et détermination de la
teneur en mercure dans les gaz de combustion en utilisant un piège
d’amalgamation de l’or
Reference number
ISO 21741:2020(E)
ISO 2020
---------------------- Page: 3 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 4

5 Principle ........................................................................................................................................................................................................................ 4

6 Reagents ........................................................................................................................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Water ............................................................................................................................................................................................................... 5

6.3 Nitric acid .................................................................................................................................................................................................... 5

6.4 Sulfuric acid ............................................................................................................................................................................................... 5

6.5 Stannous chloride solution ........................................................................................................................................................... 5

6.6 Phosphate buffer solution ............................................................................................................................................................. 5

6.7 Hydrofluoric acid .................................................................................................................................................................................. 5

6.8 Hydrochloric acid .................................................................................................................................................................................. 5

6.9 Mercury stock solution .................................................................................................................................................................... 5

6.10 Rinse solution .......................................................................................................................................................................................... 5

6.11 Sample gas drying agent ................................................................................................................................................................. 5

6.12 Trapping agent of mercury ........................................................................................................................................................... 6

7 Apparatus ..................................................................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.1.1 Main-stream sampling ................................................................................................................................................ 6

7.1.2 Side-stream sampling .................................................................................................................................................. 8

7.2 Nozzle.............................................................................................................................................................................................................. 9

7.3 Filter and filter housing ................................................................................................................................................................... 9

7.4 Transfer line ...........................................................................................................................................................................................10

7.5 Pretreatment unit ..............................................................................................................................................................................10

7.6 Gold amalgamation trap...............................................................................................................................................................11

7.7 Drying unit ...............................................................................................................................................................................................11

7.8 Suction unit .............................................................................................................................................................................................11

7.9 Thermometer ........................................................................................................................................................................................11

7.10 Manometer ..............................................................................................................................................................................................12

7.11 Gas meter ..................................................................................................................................................................................................12

7.12 Flowmeter ................................................................................................................................................................................................12

7.13 Barometer ................................................................................................................................................................................................12

8 Sampling .....................................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling position and sampling point ............................................................................................................................12

8.3 Sampling duration and sample volume ..........................................................................................................................12

8.4 Other measurements to be made prior to sampling ...........................................................................................13

8.4.1 Volumetric gas flow through duct at the sampling plane ..........................................................13

8.4.2 Moisture content of gas ...........................................................................................................................................13

8.4.3 Oxygen content of gas ...............................................................................................................................................13

8.5 Assembly of sampling apparatus .........................................................................................................................................13

8.6 Sampling ....................................................................................................................................................................................................13

8.7 Checking for leaks .............................................................................................................................................................................14

8.8 Quality assurance...............................................................................................................................................................................14

8.9 Sample recovery .................................................................................................................................................................................14

© ISO 2020 – All rights reserved iii
---------------------- Page: 5 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)

8.10 Reagent blank........................................................................................................................................................................................15

8.11 Field blank ...............................................................................................................................................................................................15

9 Sample preparation ........................................................................................................................................................................................15

9.1 General ........................................................................................................................................................................................................15

9.2 Sample preparation for particulate mercury analysis .......................................................................................15

10 Analytical procedure .....................................................................................................................................................................................16

10.1 Analytical procedure for mercury collected with gold amalgamation trap ....................................16

10.2 Analytical procedure for mercury in rinse solution and digested solution .....................................17

11 Expression of results .....................................................................................................................................................................................17

11.1 Calculation of the volume of dry flue gas sampled at sampling conditions ....................................17

11.2 Calculation of the volume of dry flue gas sample normalized to standard

temperature and pressure .........................................................................................................................................................18

11.3 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP ...............................................................................................................................................................................18

11.4 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP and reference oxygen volume fraction ..............................................................................20

11.5 Rate of mass discharge of mercury expressed as elemental mercury .................................................20

11.6 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP ..............................................................................................................................................................................20

11.7 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP and reference oxygen concentration ..................................................................................21

12 Performance characteristics .................................................................................................................................................................21

12.1 Detection limits ...................................................................................................................................................................................21

12.2 Evaluation of measurement uncertainty .......................................................................................................................21

13 Test report ................................................................................................................................................................................................................22

Annex A (informative) Preparation of mercury reference gas ...............................................................................................24

Annex B (informative) Results of evaluation of measurement uncertainties.........................................................27

Annex C (informative) Comparison of analytical results obtained with heated solid catalytic

reduction unit and stannous chloride solution unit ....................................................................................................29

Annex D (informative) Comparison of analytical results obtained with this method and

EN 13211 ....................................................................................................................................................................................................................31

Annex E (informative) Interference from sulfur dioxide (SO ) on the recovery of elemental

mercury and oxidized mercury ..........................................................................................................................................................33

Bibliography .............................................................................................................................................................................................................................35

iv © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 1,

Stationary source emissions.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2020 – All rights reserved v
---------------------- Page: 7 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)
Introduction

Because mercury is exhausted from stationary sources such as coal combustion plants, cement kilns,

non-ferrous metal smelting operations and roasting plants, and waste incineration facilities, the

monitoring of the stationary source mercury mass emissions is increasingly important for preventing

global environmental pollution and health damage caused by mercury.

This document describes a method for the sampling and determination of mercury concentrations

in a flue gas passing through ducts or chimney stacks. Mercury generally exists as elemental (Hg )

and oxidized (Hg ) forms, both in vapour and in solid phases in flue gases, this method allows the

determination of both total vapour-phase mercury and total solid-phase mercury concentrations in

flue gases.
vi © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
oSIST ISO 21741:2021
INTERNATIONAL STANDARD ISO 21741:2020(E)
Stationary source emissions — Sampling and
determination of mercury compounds in flue gas using
gold amalgamation trap
1 Scope

This document describes a method for the sampling and measurement of mercury of both vapour and

solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg ) and

oxidized (Hg ) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous)

mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after

removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures

only gaseous elemental mercury, the oxidized mercury (Hg ) in the vapour phase is converted to

elemental mercury (Hg ) prior to the gold amalgamation trap. The concentration of gaseous mercury

is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS)

after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is

collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold

vapour AFS after dissolving the particulate mercury into solution.

The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate

mercury concentrations.

The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury

3 3 3 3

ranging from 0,01 μg/m to 100 μg/m with sampling volumes from 0,005 m to 0,1 m and sample gas

flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically

3 3 3 3
from 0,01 μg/m to 100 μg/m with sampling volume from 0,05 m to 1 m .
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 9096, Stationary source emissions — Manual determination of mass concentration of particulate matter

ISO 10396, Stationary source emissions — Sampling for the automated determination of gas emission

concentrations for permanently-installed monitoring systems

ISO 12141, Stationary source emissions — Determination of mass concentration of particulate matter

(dust) at low concentrations — Manual gravimetric method

ISO 12846:2012, Water quality — Determination of mercury — Method using atomic absorption

spectrometry (AAS) with and without enrichment

ISO 16911-1, Stationary source emissions — Manual and automatic determination of velocity and volume

flow rate in ducts — Part 1: Manual reference method

ISO 17852:2006, Water quality — Determination of mercury — Method using atomic fluorescence

spectrometry
ISO 20988, Air quality — Guidelines for estimating measurement uncertainty
© ISO 2020 – All rights reserved 1
---------------------- Page: 9 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gaseous mercury

mercury existing both as elemental and oxidized forms passing through a filter having at least 99,5 %

collection efficiency for 0,3 μm diameter particles
3.2
particulate mercury

mercury existing both as elemental and oxidized forms contained in a solid phase particle collected by

a filter having at least 99,5 % collection efficiency for 0,3 μm diameter particles

3.3
isokinetic sampling

sampling at a flow rate such that the velocity and direction of the gas entering the sampling nozzle are

the same as those of the gas in the duct at the sampling point (3.4)
3.4
sampling point
specific position on the sampling section at which a sample is extracted
3.5
STP
standard conditions for temperature, 273,15 K, and pressure, 101,325 kPa
4 Symbols and abbreviated terms
4.1 Symbols
M amounts of mercury in the first gold amalgamation trap (μg)
A1,Hg
M amounts of mercury in the second gold amalgamation trap (μg)
A2,Hg

C concentration of mercury in a prepared sample of rinse solution that washed the transfer

R,Hg

line from the filter housing to the impinger nozzle of stannous chloride solution or the inlet

of catalytic reduction unit in main-stream sampling (μg/ml). Ref. Figure 1 and 2.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R1,Hg

from the filter housing to the T-piece in side-stream sampling (μg/ml). Ref. Figure 3.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R2,Hg

after the T-piece to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in side-stream sampling (μg/ml). Ref. Figure 3.
C concentration of mercury in a prepared sample solution for particulate mercury
S,Hg
analysis (μg/ml)
d density of reagent solution (g/ml)
p atmospheric pressure (kPa)
atm
2 © ISO 2020 – All rights reserved
---------------------- Page: 10 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)

p average pressure difference between the sample gas before the gas meter and the

atmosphere (kPa)
q rate of mass discharge of mercury expressed as elemental mercury (mg/s)
m,Hg

q volume flow rate of flue gas through the sampling plane at conditions i of temperature,

V,fg,i
pressure, moisture and oxygen content (m /s)
T average temperature of the sample gas before the gas meter (K)
u(y) standard uncertainty (μg/m )
V volume of dry flue gas sample normalized to STP (m )
V final gas meter reading at the end of sampling (m )

V volume of dry flue gas sample for gaseous mercury analysis normalized to STP (m )

G,d
V initial gas meter reading at the beginning of sampling (m )

V volume of air drawn through the gas meter during any intermediate leak tests (m )

V volume of dry flue gas sample (m )

V volume of dry flue gas sample in main stream, normalized to STP, in side-stream

main,d
sampling (m )

V volume of dry flue gas sample for particulate mercury analysis normalized to STP (m )

S,d

V volume of dry flue gas sampled in side stream, normalized to STP, in side-stream

side,d
sampling (m )

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in main-stream sampling (ml). Ref. Figure 1 and 2.

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the T-piece in side-stream sampling (ml). Ref. Figure 3.

v volume of a recovered sample of rinse solution that washed transfer line after the T-piece to

the impinger nozzle of stannous chloride solution or the inlet of catalytic reduction unit in

side-stream sampling (ml). Ref. Figure 3.
v volume of a prepared sample solution for particulate mercury analysis (ml)

w average moisture content of the flue gas at the sampling plane during the sampling period (%)

y j th concentration value of the first measuring system (μg/m )
1,j
y j th concentration value of the second measuring system (μg/m )
2,j

ρ mass concentration of gaseous mercury expressed as elemental mercury in the flue gas on a

G,Hg,dry
dry basis at STP (μg/m )

ρ mass concentration of particulate mercury expressed as elemental mercury in the flue gas

S,Hg,dry
on a dry basis at STP (μg/m )

ρ mass concentration of total mercury expressed as elemental mercury in the flue gas on

Hg,dry
a dry basis at STP (μg/m )
© ISO 2020 – All rights reserved 3
---------------------- Page: 11 ----------------------
oSIST ISO 21741:2021
ISO 21741:2020(E)

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a dry

Hg,dry,O
basis at STP and reference oxygen concentration (μg/m )

ρ mass concentration of mercury expressed as elemental mercury at conditions i of

Hg,i
temperature, pressure, oxygen and moisture conditions (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet
basis at STP (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet,O
basis at STP and reference oxygen concentration (μg/m )
φ volume fraction of the oxygen on a dry basis me
...

INTERNATIONAL ISO
STANDARD 21741
First edition
2020-11
Stationary source emissions —
Sampling and determination of
mercury compounds in flue gas using
gold amalgamation trap
Émissions de sources fixes — Échantillonnage et détermination de la
teneur en mercure dans les gaz de combustion en utilisant un piège
d’amalgamation de l’or
Reference number
ISO 21741:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 21741:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 21741:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 4

5 Principle ........................................................................................................................................................................................................................ 4

6 Reagents ........................................................................................................................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Water ............................................................................................................................................................................................................... 5

6.3 Nitric acid .................................................................................................................................................................................................... 5

6.4 Sulfuric acid ............................................................................................................................................................................................... 5

6.5 Stannous chloride solution ........................................................................................................................................................... 5

6.6 Phosphate buffer solution ............................................................................................................................................................. 5

6.7 Hydrofluoric acid .................................................................................................................................................................................. 5

6.8 Hydrochloric acid .................................................................................................................................................................................. 5

6.9 Mercury stock solution .................................................................................................................................................................... 5

6.10 Rinse solution .......................................................................................................................................................................................... 5

6.11 Sample gas drying agent ................................................................................................................................................................. 5

6.12 Trapping agent of mercury ........................................................................................................................................................... 6

7 Apparatus ..................................................................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.1.1 Main-stream sampling ................................................................................................................................................ 6

7.1.2 Side-stream sampling .................................................................................................................................................. 8

7.2 Nozzle.............................................................................................................................................................................................................. 9

7.3 Filter and filter housing ................................................................................................................................................................... 9

7.4 Transfer line ...........................................................................................................................................................................................10

7.5 Pretreatment unit ..............................................................................................................................................................................10

7.6 Gold amalgamation trap...............................................................................................................................................................11

7.7 Drying unit ...............................................................................................................................................................................................11

7.8 Suction unit .............................................................................................................................................................................................11

7.9 Thermometer ........................................................................................................................................................................................11

7.10 Manometer ..............................................................................................................................................................................................12

7.11 Gas meter ..................................................................................................................................................................................................12

7.12 Flowmeter ................................................................................................................................................................................................12

7.13 Barometer ................................................................................................................................................................................................12

8 Sampling .....................................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling position and sampling point ............................................................................................................................12

8.3 Sampling duration and sample volume ..........................................................................................................................12

8.4 Other measurements to be made prior to sampling ...........................................................................................13

8.4.1 Volumetric gas flow through duct at the sampling plane ..........................................................13

8.4.2 Moisture content of gas ...........................................................................................................................................13

8.4.3 Oxygen content of gas ...............................................................................................................................................13

8.5 Assembly of sampling apparatus .........................................................................................................................................13

8.6 Sampling ....................................................................................................................................................................................................13

8.7 Checking for leaks .............................................................................................................................................................................14

8.8 Quality assurance...............................................................................................................................................................................14

8.9 Sample recovery .................................................................................................................................................................................14

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 21741:2020(E)

8.10 Reagent blank........................................................................................................................................................................................15

8.11 Field blank ...............................................................................................................................................................................................15

9 Sample preparation ........................................................................................................................................................................................15

9.1 General ........................................................................................................................................................................................................15

9.2 Sample preparation for particulate mercury analysis .......................................................................................15

10 Analytical procedure .....................................................................................................................................................................................16

10.1 Analytical procedure for mercury collected with gold amalgamation trap ....................................16

10.2 Analytical procedure for mercury in rinse solution and digested solution .....................................17

11 Expression of results .....................................................................................................................................................................................17

11.1 Calculation of the volume of dry flue gas sampled at sampling conditions ....................................17

11.2 Calculation of the volume of dry flue gas sample normalized to standard

temperature and pressure .........................................................................................................................................................18

11.3 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP ...............................................................................................................................................................................18

11.4 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP and reference oxygen volume fraction ..............................................................................20

11.5 Rate of mass discharge of mercury expressed as elemental mercury .................................................20

11.6 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP ..............................................................................................................................................................................20

11.7 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP and reference oxygen concentration ..................................................................................21

12 Performance characteristics .................................................................................................................................................................21

12.1 Detection limits ...................................................................................................................................................................................21

12.2 Evaluation of measurement uncertainty .......................................................................................................................21

13 Test report ................................................................................................................................................................................................................22

Annex A (informative) Preparation of mercury reference gas ...............................................................................................24

Annex B (informative) Results of evaluation of measurement uncertainties.........................................................27

Annex C (informative) Comparison of analytical results obtained with heated solid catalytic

reduction unit and stannous chloride solution unit ....................................................................................................29

Annex D (informative) Comparison of analytical results obtained with this method and

EN 13211 ....................................................................................................................................................................................................................31

Annex E (informative) Interference from sulfur dioxide (SO ) on the recovery of elemental

mercury and oxidized mercury ..........................................................................................................................................................33

Bibliography .............................................................................................................................................................................................................................35

iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 21741:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 1,

Stationary source emissions.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
ISO 21741:2020(E)
Introduction

Because mercury is exhausted from stationary sources such as coal combustion plants, cement kilns,

non-ferrous metal smelting operations and roasting plants, and waste incineration facilities, the

monitoring of the stationary source mercury mass emissions is increasingly important for preventing

global environmental pollution and health damage caused by mercury.

This document describes a method for the sampling and determination of mercury concentrations

in a flue gas passing through ducts or chimney stacks. Mercury generally exists as elemental (Hg )

and oxidized (Hg ) forms, both in vapour and in solid phases in flue gases, this method allows the

determination of both total vapour-phase mercury and total solid-phase mercury concentrations in

flue gases.
vi © ISO 2020 – All rights reserved
---------------------- Page: 6 ----------------------
INTERNATIONAL STANDARD ISO 21741:2020(E)
Stationary source emissions — Sampling and
determination of mercury compounds in flue gas using
gold amalgamation trap
1 Scope

This document describes a method for the sampling and measurement of mercury of both vapour and

solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg ) and

oxidized (Hg ) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous)

mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after

removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures

only gaseous elemental mercury, the oxidized mercury (Hg ) in the vapour phase is converted to

elemental mercury (Hg ) prior to the gold amalgamation trap. The concentration of gaseous mercury

is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS)

after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is

collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold

vapour AFS after dissolving the particulate mercury into solution.

The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate

mercury concentrations.

The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury

3 3 3 3

ranging from 0,01 μg/m to 100 μg/m with sampling volumes from 0,005 m to 0,1 m and sample gas

flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically

3 3 3 3
from 0,01 μg/m to 100 μg/m with sampling volume from 0,05 m to 1 m .
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 9096, Stationary source emissions — Manual determination of mass concentration of particulate matter

ISO 10396, Stationary source emissions — Sampling for the automated determination of gas emission

concentrations for permanently-installed monitoring systems

ISO 12141, Stationary source emissions — Determination of mass concentration of particulate matter

(dust) at low concentrations — Manual gravimetric method

ISO 12846:2012, Water quality — Determination of mercury — Method using atomic absorption

spectrometry (AAS) with and without enrichment

ISO 16911-1, Stationary source emissions — Manual and automatic determination of velocity and volume

flow rate in ducts — Part 1: Manual reference method

ISO 17852:2006, Water quality — Determination of mercury — Method using atomic fluorescence

spectrometry
ISO 20988, Air quality — Guidelines for estimating measurement uncertainty
© ISO 2020 – All rights reserved 1
---------------------- Page: 7 ----------------------
ISO 21741:2020(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gaseous mercury

mercury existing both as elemental and oxidized forms passing through a filter having at least 99,5 %

collection efficiency for 0,3 μm diameter particles
3.2
particulate mercury

mercury existing both as elemental and oxidized forms contained in a solid phase particle collected by

a filter having at least 99,5 % collection efficiency for 0,3 μm diameter particles

3.3
isokinetic sampling

sampling at a flow rate such that the velocity and direction of the gas entering the sampling nozzle are

the same as those of the gas in the duct at the sampling point (3.4)
3.4
sampling point
specific position on the sampling section at which a sample is extracted
3.5
STP
standard conditions for temperature, 273,15 K, and pressure, 101,325 kPa
4 Symbols and abbreviated terms
4.1 Symbols
M amounts of mercury in the first gold amalgamation trap (μg)
A1,Hg
M amounts of mercury in the second gold amalgamation trap (μg)
A2,Hg

C concentration of mercury in a prepared sample of rinse solution that washed the transfer

R,Hg

line from the filter housing to the impinger nozzle of stannous chloride solution or the inlet

of catalytic reduction unit in main-stream sampling (μg/ml). Ref. Figure 1 and 2.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R1,Hg

from the filter housing to the T-piece in side-stream sampling (μg/ml). Ref. Figure 3.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R2,Hg

after the T-piece to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in side-stream sampling (μg/ml). Ref. Figure 3.
C concentration of mercury in a prepared sample solution for particulate mercury
S,Hg
analysis (μg/ml)
d density of reagent solution (g/ml)
p atmospheric pressure (kPa)
atm
2 © ISO 2020 – All rights reserved
---------------------- Page: 8 ----------------------
ISO 21741:2020(E)

p average pressure difference between the sample gas before the gas meter and the

atmosphere (kPa)
q rate of mass discharge of mercury expressed as elemental mercury (mg/s)
m,Hg

q volume flow rate of flue gas through the sampling plane at conditions i of temperature,

V,fg,i
pressure, moisture and oxygen content (m /s)
T average temperature of the sample gas before the gas meter (K)
u(y) standard uncertainty (μg/m )
V volume of dry flue gas sample normalized to STP (m )
V final gas meter reading at the end of sampling (m )

V volume of dry flue gas sample for gaseous mercury analysis normalized to STP (m )

G,d
V initial gas meter reading at the beginning of sampling (m )

V volume of air drawn through the gas meter during any intermediate leak tests (m )

V volume of dry flue gas sample (m )

V volume of dry flue gas sample in main stream, normalized to STP, in side-stream

main,d
sampling (m )

V volume of dry flue gas sample for particulate mercury analysis normalized to STP (m )

S,d

V volume of dry flue gas sampled in side stream, normalized to STP, in side-stream

side,d
sampling (m )

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in main-stream sampling (ml). Ref. Figure 1 and 2.

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the T-piece in side-stream sampling (ml). Ref. Figure 3.

v volume of a recovered sample of rinse solution that washed transfer line after the T-piece to

the impinger nozzle of stannous chloride solution or the inlet of catalytic reduction unit in

side-stream sampling (ml). Ref. Figure 3.
v volume of a prepared sample solution for particulate mercury analysis (ml)

w average moisture content of the flue gas at the sampling plane during the sampling period (%)

y j th concentration value of the first measuring system (μg/m )
1,j
y j th concentration value of the second measuring system (μg/m )
2,j

ρ mass concentration of gaseous mercury expressed as elemental mercury in the flue gas on a

G,Hg,dry
dry basis at STP (μg/m )

ρ mass concentration of particulate mercury expressed as elemental mercury in the flue gas

S,Hg,dry
on a dry basis at STP (μg/m )

ρ mass concentration of total mercury expressed as elemental mercury in the flue gas on

Hg,dry
a dry basis at STP (μg/m )
© ISO 2020 – All rights reserved 3
---------------------- Page: 9 ----------------------
ISO 21741:2020(E)

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a dry

Hg,dry,O
basis at STP and reference oxygen concentration (μg/m )

ρ mass concentration of mercury expressed as elemental mercury at conditions i of

Hg,i
temperature, pressure, oxygen and moisture conditions (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet
basis at STP (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet,O
basis at STP and reference oxygen concentration (μg/m )
φ volume fraction of the oxygen on a dry basis measured during the sampling (%)
O, d
φ volume fraction of the reference oxygen for the process (%)
O, ref
4.2 Abbreviated terms
AAS atomic absorption spectrometry
AFS atomic fluorescence spectrometry
FEP perfluoro(ethylene/propylene), tetrafluoroethylene/hexafluoropropylene
PFA perfluoroalkoxy alkane
PTFE polytetrafluoroethylene
5 Principle

In flue gases, mercury commonly exists in both the vapour phase and solid phase. In this method,

particulate mercury is captured on a filter, and gaseous mercury is captured on a gold amalgamation

trap. The total concentration of mercury in a flue gas is expressed as the sum of both concentrations.

To determine particulate mercury contents in a flue gas, a sample is taken isokinetically and particles

are collected on a filter in accordance with ISO 9096 or ISO 12141. The particulate mercury on the filter

is dissolved into solution from the filter and the mercury concentration is determined using cold vapour

atomic absorption spectrometry (CV AAS, ISO 12846) or cold vapour atomic fluorescence spectrometry

(CV A
...

NORME ISO
INTERNATIONALE 21741
Première édition
2020-11
Émissions de sources fixes —
Échantillonnage et détermination
de la teneur en mercure dans les gaz
de combustion en utilisant un piège
d’amalgamation avec de l’or
Stationary source emissions — Sampling and determination of
mercury compounds in flue gas using gold amalgamation trap
Numéro de référence
ISO 21741:2020(F)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 21741:2020(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2020

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y compris la photocopie, ou la diffusion sur l’internet ou sur un intranet, sans autorisation écrite préalable. Une autorisation peut

être demandée à l’ISO à l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.

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Publié en Suisse
ii © ISO 2020 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO 21741:2020(F)
Sommaire Page

Avant-propos ................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Domaine d’application ................................................................................................................................................................................... 1

2 Références normatives ................................................................................................................................................................................... 1

3 Termes et définitions ....................................................................................................................................................................................... 2

4 Symboles et termes abrégés ..................................................................................................................................................................... 2

4.1 Symboles ...................................................................................................................................................................................................... 2

4.2 Abréviations .............................................................................................................................................................................................. 4

5 Principe .......................................................................................................................................................................................................................... 4

6 Réactifs ........................................................................................................................................................................................................................... 5

6.1 Généralités .................................................................................................................................................................................................. 5

6.2 Eau ..................................................................................................................................................................................................................... 5

6.3 Acide nitrique ........................................................................................................................................................................................... 5

6.4 Acide sulfurique ..................................................................................................................................................................................... 5

6.5 Solution de chlorure stanneux .................................................................................................................................................. 5

6.6 Solution tampon phosphatée ...................................................................................................................................................... 5

6.7 Acide fluorhydrique ............................................................................................................................................................................ 6

6.8 Acide chlorhydrique ........................................................................................................................................................................... 6

6.9 Solution mère de mercure ............................................................................................................................................................. 6

6.10 Solution de rinçage .............................................................................................................................................................................. 6

6.11 Agent de déshydratation du gaz prélevé........................................................................................................................... 6

6.12 Agent de piégeage du mercure .................................................................................................................................................. 6

7 Appareillage .............................................................................................................................................................................................................. 6

7.1 Généralités .................................................................................................................................................................................................. 6

7.1.1 Système de prélèvement sans ligne secondaire .................................................................................... 7

7.1.2 Système de prélèvement avec ligne secondaire .................................................................................... 8

7.2 Buse .................................................................................................................................................................................................................. 9

7.3 Filtre et porte-filtre ..........................................................................................................................................................................10

7.4 Ligne de transfert...............................................................................................................................................................................10

7.5 Unité de prétraitement..................................................................................................................................................................10

7.6 Piège d’amalgamation avec de l’or ......................................................................................................................................11

7.7 Unité de séchage .................................................................................................................................................................................11

7.8 Pompe de prélèvement .................................................................................................................................................................12

7.9 Thermomètre ........................................................................................................................................................................................12

7.10 Manomètre ..............................................................................................................................................................................................12

7.11 Compteur à gaz ....................................................................................................................................................................................12

7.12 Débitmètre ...............................................................................................................................................................................................12

7.13 Baromètre ................................................................................................................................................................................................12

8 Prélèvement ...........................................................................................................................................................................................................12

8.1 Généralités ...............................................................................................................................................................................................12

8.2 Position et point de prélèvement .........................................................................................................................................12

8.3 Durée de prélèvement et volume prélevé .....................................................................................................................13

8.4 Autres mesurages à effectuer avant le prélèvement............................................................................................13

8.4.1 Débit-volume du gaz au niveau de la section de mesurage du conduit .........................13

8.4.2 Teneur en vapeur d’eau du gaz .........................................................................................................................13

8.4.3 Teneur en oxygène du gaz .....................................................................................................................................13

8.5 Assemblage de l’appareillage de prélèvement .........................................................................................................13

8.6 Prélèvement ......... ...................................................................................................................................................................................14

8.7 Contrôle d’étanchéité .....................................................................................................................................................................14

8.8 Assurance de la qualité .................................................................................................................................................................14

8.9 Récupération de l’échantillon .................................................................................................................................................15

© ISO 2020 – Tous droits réservés iii
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ISO 21741:2020(F)

8.10 Blanc de réactif ....................................................................................................................................................................................15

8.11 Blanc de site ............................................................................................................................................................................................16

9 Préparation de l’échantillon .................................................................................................................................................................16

9.1 Généralités ...............................................................................................................................................................................................16

9.2 Préparation de l’échantillon en vue de l’analyse du mercure particulaire.......................................16

10 Mode opératoire d’analyse ......................................................................................................................................................................16

10.1 Mode opératoire d’analyse applicable au mercure collecté avec le piège

d’amalgamation avec de l’or .....................................................................................................................................................16

10.2 Mode opératoire d’analyse pour le mercure présent dans la solution de rinçage et

la solution digérée .............................................................................................................................................................................18

11 Expression des résultats............................................................................................................................................................................18

11.1 Calcul du volume d’effluent gazeux sec prélevé dans les conditions de prélèvement ...........18

11.2 Calcul du volume de l’échantillon sec d’effluent gazeux normalisé en fonction

d’une température normale et d’une pression normale ..................................................................................19

11.3 Concentration massique de mercure gazeux dans l’effluent gazeux exprimé en

mercure élémentaire sur une base sèche et dans les conditions NTP .................................................19

11.4 Concentration massique de mercure dans l’effluent gazeux exprimé en mercure
élémentaire, sur une base sèche, dans les conditions NTP et avec une teneur en

oxygène de référence ......................................................................................................................................................................21

11.5 Flux massique du mercure exprimé en mercure élémentaire ....................................................................21

11.6 Concentration massique de mercure de l’effluent gazeux exprimé en mercure

élémentaire sur une base humide dans les conditions NTP .........................................................................22

11.7 Concentration massique de mercure de l’effluent gazeux exprimé en mercure
élémentaire de, sur une base humide dans les conditions NTP et avec une teneur

en oxygène de référence ..............................................................................................................................................................22

12 Caractéristiques de performances ..................................................................................................................................................22

12.1 Limites de détection ........................................................................................................................................................................22

12.2 Évaluation de l’incertitude de mesure .............................................................................................................................22

13 Rapport d’essai ....................................................................................................................................................................................................23

Annexe A (informative) Préparation du mercure gazeux de référence ........................................................................25

Annexe B (informative) Résultats de l’évaluation de l’incertitude de mesure ......................................................28

Annexe C (informative) Comparaison des résultats analytiques obtenus en utilisant

une unité de réduction catalytique chauffée et une unité de solution de chlorure

stanneux .....................................................................................................................................................................................................................30

Annexe D (informative) Comparaison des résultats analytiques obtenus en utilisant la

présente méthode et l’EN 13211 .......................................................................................................................................................32

Bibliographie ...........................................................................................................................................................................................................................37

iv © ISO 2020 – Tous droits réservés
---------------------- Page: 4 ----------------------
ISO 21741:2020(F)
Avant-propos

L’ISO (Organisation internationale de normalisation) est une fédération mondiale d’organismes

nationaux de normalisation (comités membres de l’ISO). L’élaboration des Normes internationales est

en général confiée aux comités techniques de l’ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l’ISO participent également aux travaux.

L’ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. Il convient, en particulier de prendre note des différents

critères d’approbation requis pour les différents types de documents ISO. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir www

.iso .org/ directives).

L’attention est attirée sur le fait que certains des éléments du présent document peuvent faire l’objet de

droits de propriété intellectuelle ou de droits analogues. L’ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l’élaboration du document sont indiqués dans l’Introduction et/ou dans la liste des déclarations de

brevets reçues par l’ISO (voir www .iso .org/ brevets).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l’intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l’ISO liés à l’évaluation de la conformité, ou pour toute information au sujet de l’adhésion

de l’ISO aux principes de l’Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir le lien suivant: www .iso .org/ iso/ fr/ avant -propos.

Le présent document a été élaboré par le comité technique ISO/TC 146, Qualité de l’air, sous-comité SC 1,

Émissions de sources fixes.

Il convient que l’utilisateur adresse tout retour d’information ou toute question concernant le présent

document à l’organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l’adresse www .iso .org/ fr/ members .html.
© ISO 2020 – Tous droits réservés v
---------------------- Page: 5 ----------------------
ISO 21741:2020(F)
Introduction

Les sources fixes telles que les installations de combustion à charbon, les fours de cimenterie, les

activités de fonderie de métaux non ferreux, les installations de calcination et les installations

d’incinération de déchets émettent du mercure. Il est donc de plus en plus important de contrôler les

émissions massiques de mercure des sources fixes afin de prévenir la pollution environnementale et les

effets néfastes du mercure sur la santé.

Le présent document décrit une méthode de prélèvement et de détermination des concentrations

en mercure des effluents gazeux dans les conduits ou émis en cheminées d’usine. Le mercure existe

0 2+

généralement sous forme élémentaire (Hg ) et oxydée (Hg ), à la fois en phase vapeur et en phase solide,

dans les effluents gazeux. Cette méthode permet de déterminer les concentrations totales en mercure

en phase vapeur et les concentrations totales en mercure en phase solide dans les effluents gazeux.

vi © ISO 2020 – Tous droits réservés
---------------------- Page: 6 ----------------------
NORME INTERNATIONALE ISO 21741:2020(F)
Émissions de sources fixes — Échantillonnage et
détermination de la teneur en mercure dans les gaz de
combustion en utilisant un piège d’amalgamation avec de
l’or
1 Domaine d’application

Le présent document décrit une méthode de prélèvement et de mesurage du mercure en phase vapeur

et en phase solide dans les effluents gazeux des sources fixes. Le mercure existe généralement sous

0 2+

forme élémentaire (Hg ) et oxydée (Hg ), à la fois en phase vapeur et en phase solide, dans les

effluents gazeux. Le mercure en phase vapeur (gazeux) est collecté par échantillonnage isocinétique

ou non isocinétique avec un piège d’amalgamation composé d’or après élimination du mercure en phase

solide (particulaire) à l’aide d’un filtre. Le piège d’amalgamation avec de l’or collectant uniquement

2+ 0

le mercure élémentaire gazeux, le mercure oxydé (Hg ) est converti en mercure élémentaire (Hg )

en phase vapeur, avant le piège d’amalgamation. La concentration en mercure gazeux est déterminée

par spectrométrie d’absorption atomique (AAS) ou par spectrométrie de fluorescence atomique (AFS)

après relargage du mercure par chauffage du piège d’amalgamation avec de l’or. Parallèlement, le

mercure particulaire est collecté par échantillonnage isocinétique sur un filtre et sa concentration est

déterminée par spectrométrie d’absorption atomique à vapeur froide (CVAAS) ou par spectrométrie de

fluorescence atomique à vapeur froide (CVAFS) après mise en solution du mercure particulaire.

La concentration totale en mercure dans l’effluent gazeux est exprimée sous forme de somme des

concentrations en mercure gazeux et en mercure particulaire.

La méthode d’amalgamation avec de l’or est destinée aux mesurages à court terme (périodiques) du

3 3

mercure gazeux dans une plage de concentration de 0,01 μg/m à 100 μg/m avec des volumes de

3 3

prélèvement compris entre 0,005 m et 0,1 m et un débit de gaz prélevé compris entre 0,2 l/min et 1 l/

3 3

min. La plage de mesurage du mercure particulaire s’étend généralement de 0,01 μg/m à 100 μg/m

3 3
avec des volumes de prélèvement compris entre 0,05 m et 1 m .
2 Références normatives

Les documents ci-après, dans leur intégralité ou non, sont des références normatives indispensables à

l’application du présent document. Pour les références datées, seule l’édition citée s’applique. Pour les

références non datées, la dernière édition du document de référence s’applique (y compris les éventuels

amendements).

ISO 3696, Eau pour laboratoire à usage analytique — Spécification et méthodes d'essai

ISO 9096, Émissions de sources fixes — Détermination manuelle de la concentration en masse de poussières

ISO 10396, Émissions de sources fixes — Échantillonnage pour la détermination automatisée des

concentrations d'émission de gaz pour des systèmes fixes de surveillance

ISO 12141, Émissions de sources fixes — Détermination d'une faible concentration en masse de matières

particulaires (poussières) — Méthode gravimétrique manuelle

ISO 12846:2012, Qualité de l'eau — Dosage du mercure — Méthode par spectrométrie d'absorption

atomique (SAA) avec et sans enrichissement

ISO 16911-1, Émissions de sources fixes — Détermination manuelle et automatique de la vitesse et du débit-

volume d'écoulement dans les conduits — Partie 1: Méthode de référence manuelle
© ISO 2020 – Tous droits réservés 1
---------------------- Page: 7 ----------------------
ISO 21741:2020(F)

ISO 17852:2006, Qualité de l'eau — Dosage du mercure — Méthode par spectrométrie de fluorescence

atomique

ISO 20988, Qualité de l'air — Lignes directrices pour estimer l'incertitude de mesure

3 Termes et définitions

Pour les besoins du présent document, les termes et définitions suivants s’appliquent.

L’ISO et l’IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en

normalisation, consultables aux adresses suivantes:

— ISO Online browsing platform: disponible à l’adresse https:// www .iso .org/ obp

— IEC Electropedia: disponible à l’adresse http:// www .electropedia .org/
3.1
mercure gazeux

mercure existant à la fois sous forme élémentaire et oxydée, traversant un filtre ayant un rendement de

collecte d’au moins 99,5 % pour des particules de 0,3 μm de diamètre
3.2
mercure particulaire

mercure existant à la fois sous forme élémentaire et oxydée, contenu dans une particule en phase solide

captée par un filtre ayant un rendement de collecte d’au moins 99,5 % pour des particules de 0,3 μm de

diamètre
3.3
échantillonnage isocinétique

prélèvement effectué à un débit tel que la vitesse et la direction du gaz entrant dans la buse de

prélèvement sont les mêmes que celles du gaz dans le conduit au niveau du point de prélèvement (3.4)

3.4
point de prélèvement

position spécifique sur la section de mesurage au niveau de laquelle un échantillon est extrait

3.5
NTP
conditions normales de température (273,15 K) et de pression (101,325 kPa)
4 Symboles et termes abrégés
4.1 Symboles
M quantités de mercure dans le premier piège d’amalgamation avec de l’or (µg)
A1,Hg
M quantités de mercure dans le second piège d’amalgamation avec de l’or (µg)
A2,Hg

C concentration en mercure de la solution de rinçage ayant servi à rincer la ligne de transfert

R,Hg

entre le porte-filtre et le tube plongeur de l’impinger contenant la solution de chlorure stan-

neux, ou l’entrée de l’unité de réduction catalytique, dans le cas d’un système de prélèvement

sans ligne secondaire (μg/ml). Voir Figures 1 et 2.

C concentration en mercure de la solution de rinçage ayant servi à rincer la ligne de transfert

R1,Hg

entre le porte-filtre et la pièce en T, dans le cas d’un prélèvement avec ligne secondaire (µg/

ml). Voir Figure 3.
2 © ISO 2020 – Tous droits réservés
---------------------- Page: 8 ----------------------
ISO 21741:2020(F)

C concentration en mercure de la solution de rinçage ayant servi à rincer la ligne de transfert

R2,Hg

après la pièce en T jusqu’au tube plongeur de l’impinger contenant la solution de chlorure

stanneux, ou l’entrée de l’unité de réduction catalytique, dans le cas d’un prélèvement avec

ligne secondaire (μg/ml). Voir Figure 3.

C concentration en mercure de la solution préparée pour l’analyse du mercure particulaire (µg/ml)

S,Hg
d masse volumique de la solution de réactif (g/ml)
p pression atmosphérique (kPa)
atm

p différence de pression moyenne entre le gaz entrant dans le compteur à gaz et l’atmosphère (kPa)

q flux massique du mercure exprimé en mercure élémentaire (mg/s)
m,Hg

q débit-volume d’effluent gazeux au niveau de la section de mesurage dans les conditions i de

V,fg,i
température, de pression, de teneur en vapeur d’eau et en oxygène (m /s)
T température moyenne du gaz prélevé avant le compteur de gaz (K)
u incertitude-type (μg/m )
(y)

V volume de l’échantillon sec d’effluent gazeux normalisé dans les conditions NTP (m )

V valeur finale affichée par le compteur à gaz à la fin du prélèvement (m )

V volume de l’échantillon sec d’effluent gazeux destiné à l’analyse du mercure gazeux, normalisé

G,d
dans les conditions NTP (m )
V valeur initiale affichée par le compteur à gaz au début du prélèvement (m )

V volume d’air aspiré à travers le compteur à gaz pendant les essais intermédiaires d’étanchéité (m )

V volume de l’échantillon sec d’effluent gazeux (m )

V volume de l’échantillon sec d’effluent gazeux de la ligne principale, normalisé dans les condi-

principal,d
tions NTP, dans le cas d’un prélèvement avec ligne secondaire (m )

V volume de l’échantillon sec d’effluent gazeux prélevé pour l’analyse du mercure particulaire,

S,d
normalisé dans les conditions NTP (m )

V volume de l’échantillon sec d’effluent gazeux de la ligne secondaire, normalisé dans les condi-

secondaire,d
tions NTP, dans le cas d’un prélèvement avec ligne secondaire (m )

v volume récupéré de solution de rinçage ayant servi à rincer la ligne de transfert entre le

porte-filtre et le tube plongeur de l’impinger contenant la solution de chlorure stanneux, ou

l’entrée de l’unité de réduction catalytique, dans le cas d’un prélèvement sans ligne secondaire

(ml). Voir Figures 1 et 2.

v volume récupéré de solution de rinçage ayant servi à rincer la ligne de transfert entre le porte-

filtre et la pièce en T dans le cas d’un prélèvement avec ligne secondaire (ml). Voir Figure 3.

v volume récupéré de solution de rinçage ayant servi à rincer la ligne de transfert après la

pièce en T jusqu’au tube plongeur de l’impinger contenant la solution de chlorure stanneux,

ou l’entrée de l’unité de réduction catalytique, dans le cas d’un prélèvement avec ligne secon-

daire (ml). Voir Figure 3.
v volume de la solution préparée pour l’analyse du mercure particulaire (ml)
© ISO 2020 – Tous droits réservés 3
---------------------- Page: 9 ----------------------
ISO 21741:2020(F)

w teneur en vapeur d’eau moyenne de l’effluent gazeux au niveau de la section de mesurage

pendant la période de prélèvement (%)
ième 3
y j concentration du premier système de mesure (μg/m )
1,j
ème 3
y j concentration du second système de mesure (μg/m )
2,j

ρ concentration massique en mercure gazeux de l’effluent gazeux exprimé en mercure élémen-

G,Hg,sec
taire, sur une base sèche dans les co
...

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 21741
ISO/TC 146/SC 1
Stationary source emissions —
Secretariat: BIS
Sampling and determination of
Voting begins on:
2020­08­18 mercury compounds in flue gas using
gold amalgamation trap
Voting terminates on:
2020­10­13
Émissions de sources fixes — Échantillonnage et détermination de la
teneur en mercure dans les gaz de combustion en utilisant un piège
d’amalgamation de l’or
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
THEY ARE AWARE AND TO PROVIDE SUPPOR TING
DOCUMENTATION.
IN ADDITION TO THEIR EVALUATION AS
Reference number
BEING ACCEPTABLE FOR INDUSTRIAL, TECHNO­
ISO/FDIS 21741:2020(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
OCCASION HAVE TO BE CONSIDERED IN THE
LIGHT OF THEIR POTENTIAL TO BECOME STAN­
DARDS TO WHICH REFERENCE MAY BE MADE IN
NATIONAL REGULATIONS. ISO 2020
---------------------- Page: 1 ----------------------
ISO/FDIS 21741:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH­1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/FDIS 21741:2020(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Clause title ................................................................................................................................................................................................................... 2

4.1 Symbols ......................................................................................................................................................................................................... 2

4.2 Abbreviated terms ............................................................................................................................................................................... 4

5 Principle ........................................................................................................................................................................................................................ 4

6 Reagents ........................................................................................................................................................................................................................ 4

6.1 General ........................................................................................................................................................................................................... 4

6.2 Water ............................................................................................................................................................................................................... 5

6.3 Nitric acid .................................................................................................................................................................................................... 5

6.4 Sulfuric acid ............................................................................................................................................................................................... 5

6.5 Stannous chloride solution ........................................................................................................................................................... 5

6.6 Phosphate buffer solution ............................................................................................................................................................. 5

6.7 Hydrofluoric acid .................................................................................................................................................................................. 5

6.8 Hydrochloric acid .................................................................................................................................................................................. 5

6.9 Mercury stock solution .................................................................................................................................................................... 5

6.10 Rinse solution .......................................................................................................................................................................................... 5

6.11 Sample gas drying agent ................................................................................................................................................................. 5

6.12 Trapping agent of mercury ........................................................................................................................................................... 6

7 Apparatus ..................................................................................................................................................................................................................... 6

7.1 General ........................................................................................................................................................................................................... 6

7.1.1 Main­stream sampling ................................................................................................................................................ 6

7.1.2 Side­stream sampling .................................................................................................................................................. 8

7.2 Nozzle.............................................................................................................................................................................................................. 9

7.3 Filter and filter housing ................................................................................................................................................................... 9

7.4 Transfer line ...........................................................................................................................................................................................10

7.5 Pretreatment unit ..............................................................................................................................................................................10

7.6 Gold amalgamation trap...............................................................................................................................................................11

7.7 Drying unit ...............................................................................................................................................................................................11

7.8 Suction unit .............................................................................................................................................................................................11

7.9 Thermometer ........................................................................................................................................................................................11

7.10 Manometer ..............................................................................................................................................................................................12

7.11 Gas meter ..................................................................................................................................................................................................12

7.12 Flowmeter ................................................................................................................................................................................................12

7.13 Barometer ................................................................................................................................................................................................12

8 Sampling .....................................................................................................................................................................................................................12

8.1 General ........................................................................................................................................................................................................12

8.2 Sampling position and sampling point ............................................................................................................................12

8.3 Sampling duration and sample volume ..........................................................................................................................12

8.4 Other measurements to be made prior to sampling ...........................................................................................13

8.4.1 Volumetric gas flow through duct at the sampling plane ..........................................................13

8.4.2 Moisture content of gas ...........................................................................................................................................13

8.4.3 Oxygen content of gas ...............................................................................................................................................13

8.5 Assembly of sampling apparatus .........................................................................................................................................13

8.6 Sampling ....................................................................................................................................................................................................13

8.7 Checking for leaks .............................................................................................................................................................................14

8.8 Quality assurance...............................................................................................................................................................................14

8.9 Sample recovery .................................................................................................................................................................................14

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ISO/FDIS 21741:2020(E)

8.10 Reagent blank........................................................................................................................................................................................15

8.11 Field blank ...............................................................................................................................................................................................15

9 Sample preparation ........................................................................................................................................................................................15

9.1 General ........................................................................................................................................................................................................15

9.2 Sample preparation for particulate mercury analysis .......................................................................................15

10 Analytical procedure .....................................................................................................................................................................................16

10.1 Analytical procedure for mercury collected with gold amalgamation trap ....................................16

10.2 Analytical procedure for mercury in rinse solution and digested solution .....................................17

11 Expression of results .....................................................................................................................................................................................17

11.1 Calculation of the volume of dry flue gas sampled at sampling conditions ....................................17

11.2 Calculation of the volume of dry flue gas sample normalized to standard

temperature and pressure .........................................................................................................................................................18

11.3 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP ...............................................................................................................................................................................18

11.4 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a dry basis at STP and reference oxygen volume fraction ..............................................................................20

11.5 Rate of mass discharge of mercury expressed as elemental mercury .................................................20

11.6 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP ..............................................................................................................................................................................20

11.7 Mass concentration of mercury expressed as elemental mercury in the flue gas on

a wet basis at STP and reference oxygen concentration ..................................................................................21

12 Performance characteristics .................................................................................................................................................................21

12.1 Detection limits ...................................................................................................................................................................................21

12.2 Evaluation of measurement uncertainty .......................................................................................................................21

13 Test report ................................................................................................................................................................................................................22

Annex A (informative) Preparation of mercury reference gas ...............................................................................................24

Annex B (informative) Results of evaluation of measurement uncertainties.........................................................27

Annex C (informative) Comparison of analytical results obtained with heated solid catalytic

reduction unit and stannous chloride solution unit ....................................................................................................29

Annex D (informative) Comparison of analytical results obtained with this method and

EN 13211 ....................................................................................................................................................................................................................31

Annex E (informative) Interference from sulfur dioxide (SO ) on the recovery of elemental

mercury and oxidized mercury ..........................................................................................................................................................33

Bibliography .............................................................................................................................................................................................................................35

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ISO/FDIS 21741:2020(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to

the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 146, Air quality, Subcommittee SC 1,

Stationary source emissions.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 21741:2020(E)
Introduction

Because mercury is exhausted from stationary sources such as coal combustion plants, cement kilns,

non­ferrous metal smelting operations and roasting plants, and waste incineration facilities, the

monitoring of the stationary source mercury mass emissions is increasingly important for preventing

global environmental pollution and health damage caused by mercury.

This document describes a method for the sampling and determination of mercury concentrations

in a flue gas passing through ducts or chimney stacks. Mercury generally exists as elemental (Hg )

and oxidized (Hg ) forms, both in vapour and in solid phases in flue gases, this method allows the

determination of both total vapour-phase mercury and total solid-phase mercury concentrations in

flue gases.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 21741:2020(E)
Stationary source emissions — Sampling and
determination of mercury compounds in flue gas using
gold amalgamation trap
1 Scope

This document describes a method for the sampling and measurement of mercury of both vapour and

solid phases on stationary source flue gas streams. Mercury generally exists as elemental (Hg ) and

oxidized (Hg ) forms, both in the vapour and solid phases in flue gases. The vapour-phase (gaseous)

mercury is captured either isokinetically or non-isokinetically with a gold amalgamation trap after

removing solid-phase (particulate) mercury with a filter. Because gold amalgamation trap captures

only gaseous elemental mercury, the oxidized mercury (Hg ) in the vapour phase is converted to

elemental mercury (Hg ) prior to the gold amalgamation trap. The concentration of gaseous mercury

is determined using atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS)

after releasing mercury by heating the gold amalgamation trap. Separately, particulate mercury is

collected isokinetically on a filter and the concentration is determined using cold vapour AAS or cold

vapour AFS after dissolving the particulate mercury into solution.

The total concentration of mercury in flue gas is expressed as the sum of both gaseous and particulate

mercury concentrations.

The gold amalgamation method is intended for short-term (periodic) measurements of gaseous mercury

3 3 3 3

ranging from 0,01 μg/m to 100 μg/m with sampling volumes from 0,005 m to 0,1 m and sample gas

flow rate between 0,2 l/min to 1 l/min. The measurement range of particulate mercury is typically

3 3 3 3
from 0,01 μg/m to 100 μg/m with sampling volume from 0,05 m to 1 m .
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and are

indispensable for its application. For dated references, only the edition cited applies. For undated

references, the latest edition of the referenced document (including any amendments) applies.

ISO 3696, Water for analytical laboratory use — Specification and test methods

ISO 9096, Stationary source emissions — Manual determination of mass concentration of particulate matter

ISO 10396, Stationary source emissions — Sampling for the automated determination of gas emission

concentrations for permanently-installed monitoring systems

ISO 12141, Stationary source emissions — Determination of mass concentration of particulate matter

(dust) at low concentrations — Manual gravimetric method

ISO 16911­1, Stationary source emissions — Manual and automatic determination of velocity and volume

flow rate in ducts — Part 1: Manual reference method

ISO 12846:2012, Water quality — Determination of mercury — Method using atomic absorption

spectrometry (AAS) with and without enrichment

ISO 17852:2006, Water quality — Determination of mercury — Method using atomic fluorescence

spectrometry
ISO 20988, Air quality — Guidelines for estimating measurement uncertainty
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ISO/FDIS 21741:2020(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
gaseous mercury

mercury existing both as elemental and oxidized forms passing through a filter having at least 99,5 %

collection efficiency for 0,3 μm diameter particles
3.2
particulate mercury

mercury existing both as elemental and oxidized forms contained in a solid phase particle collected by

a filter having at least 99,5 % collection efficiency for 0,3 μm diameter particles

3.3
isokinetic sampling

sampling at a flow rate such that the velocity and direction of the gas entering the sampling nozzle are

the same as those of the gas in the duct at the sampling point (3.4)
3.4
sampling point
specific position on the sampling section at which a sample is extracted
3.5
STP
standard conditions for temperature, 273,15 K, and pressure, 101,325 kPa
4 Clause title
4.1 Symbols
M amounts of mercury in the first gold amalgamation trap (μg)
A1,Hg
M amounts of mercury in the second gold amalgamation trap (μg)
A2,Hg

C concentration of mercury in a prepared sample of rinse solution that washed the transfer

R,Hg

line from the filter housing to the impinger nozzle of stannous chloride solution or the inlet

of catalytic reduction unit in main-stream sampling (μg/ml). Ref. Figure 1 and 2.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R1,Hg

from the filter housing to the T-piece in side-stream sampling (μg/ml). Ref. Figure 3.

C concentration of mercury in a prepared sample of rinse solution that washed transfer line

R2,Hg

after the T-piece to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in side-stream sampling (μg/ml). Ref. Figure 3.
C concentration of mercury in a prepared sample solution for particulate mercury
S,Hg
analysis (μg/ml)
d density of reagent solution (g/ml)
p atmospheric pressure (kPa)
atm
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ISO/FDIS 21741:2020(E)

p average pressure difference between the sample gas before the gas meter and the

atmosphere (kPa)
q rate of mass discharge of mercury expressed as elemental mercury (mg/s)
m,Hg

q volume flow rate of flue gas through the sampling plane at conditions i of temperature,

V,fg,i
pressure, moisture and oxygen content (m /s)
T average temperature of the sample gas before the gas meter (K)
u standard uncertainty (μg/m )
(y)
V volume of dry flue gas sample normalized to STP (m )
V final gas meter reading at the end of sampling (m )

V volume of dry flue gas sample for gaseous mercury analysis normalized to STP (m )

G,d
V initial gas meter reading at the beginning of sampling (m )

V volume of air drawn through the gas meter during any intermediate leak tests (m )

V volume of dry flue gas sample (m )

V volume of dry flue gas sample in main stream, normalized to STP, in side-stream

main,d
sampling (m )

V volume of dry flue gas sample for particulate mercury analysis normalized to STP (m )

S,d

V volume of dry flue gas sampled in side stream, normalized to STP, in side-stream

side,d
sampling (m )

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the impinger nozzle of stannous chloride solution or the inlet of catalytic

reduction unit in main­stream sampling (ml). Ref. Figure 1 and 2.

v volume of a recovered sample of rinse solution that washed transfer line from the filter

housing to the T­piece in side­stream sampling (ml). Ref. Figure 3.

v volume of a recovered sample of rinse solution that washed transfer line after the T­piece to

the impinger nozzle of stannous chloride solution or the inlet of catalytic reduction unit in

side­stream sampling (ml). Ref. Figure 3.
v volume of a prepared sample solution for particulate mercury analysis (ml)

w average moisture content of the flue gas at the sampling plane during the sampling period (%)

y j th concentration value of the first measuring system (μg/m )
1,j
y j th concentration value of the second measuring system (μg/m )
2,j

ρ mass concentration of gaseous mercury expressed as elemental mercury in the flue gas on a

G,Hg,dry
dry basis at STP (μg/m )

ρ mass concentration of particulate mercury expressed as elemental mercury in the flue gas

S,Hg,dry
on a dry basis at STP (μg/m )

ρ mass concentration of total mercury expressed as elemental mercury in the flue gas on

Hg,dry
a dry basis at STP (μg/m )
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ISO/FDIS 21741:2020(E)

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a dry

Hg,dry,O
basis at STP and reference oxygen concentration (μg/m )

ρ mass concentration of mercury expressed as elemental mercury at conditions i of

Hg,i
temperature, pressure, oxygen and moisture conditions (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet
basis at STP (μg/m )

ρ mass concentration of mercury expressed as elemental mercury in the flue gas on a wet

Hg,wet,O
basis at STP and reference oxygen concentration (μg/m )
φ volume fraction of the oxygen on a dry basis measured during the sampling (%)
O, d
φ volume fraction of the reference oxygen for the process (%)
O, ref
4.2 Abbreviated terms
AAS atomic absorption spectrometry
AFS atomic fluorescence spectrometry
FEP Perfluoro(ethylene/propylene), tetrafluoroethylene/hexafluoropropylene
PFA perfluoroalkoxy alkane
PTFE polytetrafluoroethylene
5 Principle
In flue gases, mercury commonly exists in both the vapour phase and
...

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