Stationary source emissions — Determination of the mass concentration of nitrogen oxides in flue gas — Performance characteristics of automated measuring systems

This document specifies a method for the determination of nitrogen oxides (NOx) in flue gas of stationary sources and describes the fundamental structure and the key performance characteristics of automated measuring systems. The method allows continuous monitoring with permanently installed measuring systems of NOx emissions. This document describes extractive systems and in situ (non-extractive) systems in connection with a range of analysers that operate using, for example, the following principles: — chemiluminescence (CL); — infrared absorption (NDIR); — Fourier transform infrared (FTIR) spectroscopy; — ultraviolet absorption (NDUV); — differential optical absorption spectroscopy (DOAS); Other equivalent instrumental methods such as laser spectroscopic techniques can be used provided they meet the minimum performance requirements specified in this document. The measuring system can be validated with reference materials, in accordance with this document, or comparable methods. Automated measuring system (AMS) based on the principles listed above has been used successfully in this application for the measuring ranges as shown in Annex F.

Émissions de sources fixes — Détermination de la concentration en masse des oxydes d'azote dans les effluents gazeux — Caractéristiques de performance des systèmes de mesurage automatiques

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Publication Date
06-Sep-2022
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6060 - International Standard published
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06-Nov-2022
Completion Date
07-Sep-2022
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INTERNATIONAL ISO
STANDARD 10849
Second edition
2022-09
Stationary source emissions —
Determination of the mass
concentration of nitrogen oxides
in flue gas — Performance
characteristics of automated
measuring systems
Émissions de sources fixes — Détermination de la concentration en
masse des oxydes d'azote dans les effluents gazeux — Caractéristiques
de performance des systèmes de mesurage automatiques
Reference number
ISO 10849:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 10849:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

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
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Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 10849:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

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

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

3 Terms and definitions .................................................................................................................................................................................... 1

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

5 Principle ........................................................................................................................................................................................................................ 5

6 Description of the automated measuring systems .......................................................................................................... 5

6.1 Sampling and sample gas conditioning systems ...................................................................................................... 5

6.2 Analyser equipment ........................................................................................................................................................................... 6

7 Performance characteristics and criteria ................................................................................................................................ 6

7.1 Performance criteria ......................................................................................................................................................................... 6

7.2 Determination of the performance characteristics ............................................................................................... 7

7.2.1 Performance test ................................................................................................................................................................ 7

7.2.2 Ongoing quality control ............................................................................................................................................... 7

8 Selection and installation procedure ............................................................................................................................................ 7

8.1 Choice of the measuring system ............................................................................................................................................. 7

8.2 Sampling ....................................................................................................................................................................................................... 8

8.2.1 Sampling location .............................................................................................................................................................. 8

8.2.2 Representative sampling ............................................................................................................................................ 8

8.3 Calculation .................................................................................................................................................................................................. 8

8.3.1 Conversion from volume to mass concentration for NO ................................................................. 8

8.3.2 Calculation of NO and NO concentrations ............................................................................................... 9

2 x

9 Quality assurance and quality control procedures ........................................................................................................ 9

9.1 General ........................................................................................................................................................................................................... 9

9.2 Frequency of checks........................................................................................................................................................................... 9

9.3 Calibration, validation and measurement uncertainty ................................................................................... 10

10 Test report ...............................................................................................................................................................................................................10

Annex A (informative) Extractive NO, NO or NO measurement systems ..............................................................12

2 x

Annex B (informative) In situ NO and NO measurement systems ..................................................................................22

Annex C (normative) NO -NO converter ........................................................................................................................................................26

Annex D (normative) Operational gases ........................................................................................................................................... ............28

Annex E (normative) Procedures for determination of the performance characteristics .....................29

Annex F (informative) Examples of results for the validation of NO AMS ..............................................................37

Annex G (informative) Calculation of uncertainty of measurement of NO and/NO or NO .................41

2 x

Bibliography .............................................................................................................................................................................................................................47

iii
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ISO 10849:2022(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.

This second edition cancels and replaces the first edition (ISO 10849:1996), which has been technically

revised.
The main changes are as follows:

— the structure and the components have been updated to be similar to the latest editions of e.g.

ISO 12039 (measurement of CO, CO and O ), ISO 17179 (measurement of NH ), ISO 13199

2 2 3

(measurement of total VOC), ISO 25140 (measurement of CH ), ISO 21258 (measurement of N O);

4 2

— Clause 3 has been updated (addition or deletion and change in terms and definitions);

— a new analytical technique has been added (Fourier transform infrared spectroscopy) for

measurement of NO and NO or NO ;
2 x

— the performance characteristics and criteria as well as QA/QC procedures have been changed to

harmonize with latest ISO standards;

— examples of performance test results and the results of uncertainty calculation have been added for

NO and NO or NO measurement.
2 x

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 2022 – All rights reserved
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ISO 10849:2022(E)
Introduction

Nitrogen oxides are produced during most combustion processes. In fossil fuel combustion, nitrogen

oxides are produced from nitrogen contained in the fuel and from the oxidation of nitrogen in the air

used for combustion. The quantity of nitrogen oxides produced depends upon the nitrogen content of

the fuel, the combustor design, and the combustor operating conditions.

In flue gases from conventional boiler combustion systems, the nitrogen oxides consist of approximately

95 % nitrogen monoxide (NO). The remaining oxide is predominantly nitrogen dioxide (NO ) formed

from the oxidation of NO when the flue gas temperature decreases. These two oxides (NO + NO ) are

generally designated as NO . It should be noted that in other processes the ratio of NO to NO , may be

x 2
different and other nitrogen oxides may be present.

There are numerous ways of determining nitrogen oxides in the gases of combustion plants, both wet

chemical/analytical methods and instrumental techniques.
© ISO 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO 10849:2022(E)
Stationary source emissions — Determination of the
mass concentration of nitrogen oxides in flue gas —
Performance characteristics of automated measuring
systems
1 Scope

This document specifies a method for the determination of nitrogen oxides (NO ) in flue gas of

stationary sources and describes the fundamental structure and the key performance characteristics

of automated measuring systems.

The method allows continuous monitoring with permanently installed measuring systems of NO

emissions.

This document describes extractive systems and in situ (non-extractive) systems in connection with a

range of analysers that operate using, for example, the following principles:
— chemiluminescence (CL);
— infrared absorption (NDIR);
— Fourier transform infrared (FTIR) spectroscopy;
— ultraviolet absorption (NDUV);
— differential optical absorption spectroscopy (DOAS);

Other equivalent instrumental methods such as laser spectroscopic techniques can be used provided

they meet the minimum performance requirements specified in this document. The measuring system

can be validated with reference materials, in accordance with this document, or comparable methods.

Automated measuring system (AMS) based on the principles listed above has been used successfully in

this application for the measuring ranges as shown in Annex F.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

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

ISO 9169, Air quality — Definition and determination of performance characteristics of an automatic

measuring system

ISO 14956, Air quality — Evaluation of the suitability of a measurement procedure by comparison with a

required measurement uncertainty
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

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

— ISO Online browsing platform: available at https:// www .iso .org/ obp
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ISO 10849:2022(E)
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
analyser
analytical part in an extractive or in situ automated measuring system (3.2)
[SOURCE: ISO 12039:2019, 3.1]
3.2
automated measuring system
AMS

measuring system interacting with the flue gas under investigation, returning an output signal

proportional to the physical unit of the measurand (3.9) in unattended operation
[SOURCE: ISO 9169:2006, 2.1.2, modified — Note is removed]

Note 1 to entry: For the purposes of this document, an AMS is a system that can be attached to a duct or stack to

continuously or intermittently measure the mass concentration of NO, NO or NO passing through the duct.

2 x
3.3
in situ AMS

non-extractive system that measures the concentration directly in the duct or stack

Note 1 to entry: In situ systems measure either across the stack or duct or at a point within the duct or stack.

3.4
parallel measurements

measurements taken on the same duct in the same sampling plane for the same period of time with the

AMS under test and with the reference method at points a short distance from each other, providing

pairs of measured values
Note 1 to entry: See 3.21.
3.5
independent reading

reading that is not influenced by a previous individual reading by separating two individual readings

by at least four response times
3.6
interference
cross-sensitivity

negative or positive effect upon the response of the measuring system, due to a component of the

sample that is not the measurand
3.7
interferent
interfering substance

substance present in the air mass under investigation, other than the measurand (3.9), that affects the

response of AMS (3.2)
3.8
lack-of-fit

systematic deviation within the range of application, between the accepted value of a reference

material applied to the measuring system and the corresponding result of measurement produced by

the measuring system
Note 1 to entry: Lack-of-fit can be a function of the result of measurement.

Note 2 to entry: The expression “lack-of-fit” is often replaced in everyday language for linear relations by

“linearity” or “deviation from linearity”.
[SOURCE: ISO 9169:2006, 2.2.9, modified —Note 2 is removed.]
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ISO 10849:2022(E)
3.9
measurand
particular quantity subject to measurement
[SOURCE: ISO/IEC Guide 98-3:2008, B.2.9, modified— Example and Note is removed.]
3.10
NO /NO converter efficiency
ratio with which the converter device of a NO analyser reduces NO to NO
x 2
3.11
performance characteristic
one of the quantities assigned to equipment in order to define its performance

Note 1 to entry: Performance characteristics can be described by values, tolerances, or ranges.

3.12
period of unattended operation

maximum interval of time for which the performance characteristics remain within a predefined range

without external servicing, e.g. refill, adjustment
[SOURCE: ISO 9169:2006, 2.2.11]

Note 1 to entry: The period of unattended operation is often called maintenance interval.

3.13
reference material

substance or mixture of substances with a known concentration within specified limits, or a device of

known characteristics

Note 1 to entry: Normally calibration gases, gas cells, gratings or filters are used.

[SOURCE: ISO 14385-1:2014, 3.20]
3.14
reference method

measurement method taken as a reference by convention, which gives the accepted reference value of

the measurand
Note 1 to entry: See 3.4.
3.15
transport time in the measuring system

time period for transportation of the sampled gas from the inlet of the probe to the inlet of the

measurement instrument
3.16
response time

time interval between the instant when a stimulus is subjected to bring about a specified abrupt change

and the instant when the response reaches and remains within specified limits around its final stable

value, determined as the sum of the lag time and the rise time in the rising mode, and the sum of the lag

time and the fall time in the falling mode
[SOURCE: ISO 9169:2006, 2.2.4]
Note 1 to entry: Lag time, rise time and fall time are defined in ISO 9169:2006.
3.17
span gas

gas or gas mixture used to adjust and check the span point on the response line of the measuring system

Note 1 to entry: The concentration is often chosen around 70 % to 90 % of full scale.

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ISO 10849:2022(E)
3.18
span point

value of the output quantity (measured signal) of the automated measuring system for the purpose of

calibration, adjustment, etc. that represents a correct measured value generated by reference gas

3.19
standard uncertainty
uncertainty of the result of a measurement expressed as a standard deviation
[SOURCE: ISO/IEC Guide 98-3:2008, 2.3.1]
3.20
uncertainty

parameter associated with the result of a measurement, that characterizes the dispersion of the values

that could reasonably be attributed to the measurand
[SOURCE: ISO/IEC Guide 98-3: 2008, 2.2.3 modified — Note 1, 2 and 3 removed.]
3.21
validation of an automated measuring system

procedure to check the statistical relationship between values of the measurand indicated by

the automated measuring system and the corresponding values given by parallel measurements

implemented simultaneously at the same measuring point
3.22
zero gas

gas or gas mixture used to establish the zero point (3.23) on a calibration curve within a given

concentration range
[SOURCE: ISO 12039:2019, 3.20]
3.23
zero point

specified value of the output quantity (measured signal) of the AMS and which, in the absence of the

measured component, represents the zero crossing of the calibration line
4 Symbols and abbreviated terms
e Residual (lack-of-fit) at level i
K Coverage factor
N Number of measurements
s Standard deviation of repeatability
u(γ ) Combined uncertainty of X (NO or NO ) mass concentration
X 2
U(γ ) Expanded uncertainty of X (NO or NO ) mass concentration
X 2
M Molar mass of X (NO or NO , g/mol)
x 2
V Molar volume (22,4 l/mol at standard conditions, 273,15 K; 101,325 kPa)
φ Volume fraction of X (NO or NO )
X 2

γ X (NO or NO ) mass concentration at standard conditions in mg/m (273,15 K; 101,325 kPa)

X 2

γ NO or NO mass concentration at reference conditions in mg/m (273,15 K; 101,325 kPa; H O

R 2 2
corrected)
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ISO 10849:2022(E)
Average of the measured values x
x ith measured value
x Average of the measured value at level i
x Value estimated by the regression line at level i
AMS Automated measuring system
FTIR Fourier transform infrared
NDIR Non-dispersive infrared
NDUV Non-dispersive ultraviolet
DOAS Differential optical absorption spectroscopy
QA Quality assurance
QC Quality control
5 Principle

This document describes automated measurement systems for sampling, sample conditioning, and

determining NO and NO or NO content in flue gas using instrumental methods (analysers).

2 x
There are two types of automated measuring systems:
— extractive systems;
— in situ systems.

With extractive systems, a representative sample of gas is taken from the stack with a sampling probe

and conveyed to the analyser through the sample line and sample gas conditioning system.

In situ systems do not require any sampling transfers out of the stack. For the installation of these

systems, a representative place in the stack is to be chosen.

The systems described in this document measure NO and NO or NO concentrations using instrumental

2 x
methods that shall meet the minimum performance specifications given.

In most of the cases, it is considered that only NO is measured, because the NO content is much smaller

than NO. However, in some cases NO may exist in large quantities and shall be taken into account,

either by direct measurement or by using a converter of NO to NO. The sampling is more complex.

6 Description of the automated measuring systems
6.1 Sampling and sample gas conditioning systems

Sampling and sample gas conditioning systems for extractive and in situ methods shall conform to

ISO 10396.

In extractive sampling, these gases are conditioned to remove aerosols, particulate matter and other

interfering substances before being conveyed to the instruments. Three kinds of extractive systems as

well as non-extractive systems are described in ISO 10396:
a) Cold-dry,
b) Hot-wet and
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ISO 10849:2022(E)

c) Dilution. In non-extractive sampling, the measurements are made in situ; therefore, no sample

conditioning is required.

The details of the extractive sampling and sample gas conditioning systems are described in Annex A

and two kinds of in situ system are illustrated in Annex B.
6.2 Analyser equipment

Examples of the typical analytical methods available are described in Annex A and Annex B.

The NO to NO converter is necessary if NO is measured with an NO analyser (only required in

2 2

combination with extractive systems). The details of the converter and the test method for the

performance characteristics are described in Annex C.
AMS shall meet the performance characteristics as described in Clause 7.
7 Performance characteristics and criteria
7.1 Performance criteria

Table 1 gives the performance characteristics and performance criteria of the analyser and measurement

system to be evaluated during performance test, by means of ongoing QA/QC in the laboratory and

during field operation. Test procedures for the performance test are specified in Annex E.

Table 1 — Performance characteristics and criteria of AMS for measurement of NO and NO

Performance characteristic Performance criterion Test procedure
Response time ≤ 200 s E.2

Standard deviation of repeatability in ≤ 2,0 % of the upper limit of the lowest meas-

E.3.2
laboratory at zero point uring range used

Standard deviation of repeatability (NO ≤ 2,0 % of the upper limit of the lowest meas-

E.3.3
or NO ) in laboratory at span point uring range used
≤ 2,0 % of the upper limit of the lowest meas-
Lack-of-fit E.4
uring range used
≤ 2,0 % of the upper limit of the lowest meas-
Zero drift within 24 h E.5
uring range used
≤ 2,0 % of the upper limit of the lowest meas-
Span drift within 24 h E.5
uring range used

Zero drift within the period of unattend- ≤ 3,0 % of the upper limit of the lowest meas-

E.6
ed operation uring range used

Span drift within the period of unattend- ≤ 3,0 % of the upper limit of the lowest meas-

E.6
ed operation uring range used
Sensitivity to ambient temperature, for a
≤ 5,0 % of the upper limit of the lowest meas-
change of 20 K in the temperature range E.7
uring range used
specified by the manufacturer

Sensitivity to sample gas pressure, for a ≤ 2,0 % of the upper limit of the lowest meas-

E.8
pressure change of 3 kPa uring range used

Sensitivity to sample gas flow for an ≤ 2,0 % of the upper limit of the lowest meas-

E.9
extractive AMS uring range used
Sensitivity to electric voltage in the

range -15 % below or +10 % above from ≤ 2,0 % of the upper limit of the lowest meas-

E.10
the nominal voltage stated by the manu- uring range used
facturer
≤ 4,0 % of the upper limit of the lowest meas-
Cross-sensitivity E.11
uring range used
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ISO 10849:2022(E)
Table 1 (continued)
Performance characteristic Performance criterion Test procedure
Losses and leakage in the sampling line
≤ 2,0 % of the measured value E.12 and E.13
and conditioning system
Excursion of the measurement beam of ≤ 2 % of the measured value of the lowest
E.14
cross-stack in situ AMS measuring range used
NO /NO converter efficiency if applicable ≥ 95,0 % Annex C
7.2 Determination of the performance characteristics
7.2.1 Performance test

The performance characteristics of the AMS shall be determined during the performance test. The

values of the performance characteristics determined shall meet the performance criteria specified in

Table 1. The procedures for the determination of these performance characteristics are specified in

Annex E.

The ambient conditions applied during the general performance test shall be documented.

The measurement uncertainty of the AMS measured values shall be calculated in accordance with

ISO 14956 on the basis of the performance characteristics determined during the performance test

and shall meet the level of uncertainty appropriate for the intended use. These characteristics may be

determined either by the manufacturer or by the user.
7.2.2 Ongoing quality control

The user shall check specific performance characteristics during ongoing operation of the measuring

system with a periodicity specified in Table 2.

The measurement uncertainty during field application shall be determined by the user of the measuring

system in accordance with applicable international or national standards. For process monitoring,

the level of uncertainty shall be appropriate for the intended use. It can be determined by a direct or

an indirect approach for uncertainty estimation as described in ISO 20988. The uncertainty of the

measured values under field operation is not only influenced by the performance characteristics of the

analyser itself but also by uncertainty contributions due to:
— the sampling line and conditioning system,
— the site specific conditions, and
— the reference materials used.
8 Selection and installation procedure
8.1 Choice of the measuring system

To choose an appropriate analyser, sampling line and conditioning unit, the following characteristics of

flue gases should be known before the field operation:
— ambient temperature range;
— temperature range of the flue gas;
— water vapour content of the flue gas;
— dust loading of the flue gas;
— expected concentration range of NO, NO or NO ;
2 x
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ISO 10849:2022(E)
— expected concentration of potentially interfering substances.

To avoid long response time and memory effects, the sampling line should be as short as possible. If

necessary, a bypass pump should be used. If there is a high dust loading in the sample gas, an appropriate

heated filter shall be used.

Before monitoring emissions, the user shall verify that the necessary QA/QC procedures have been

performed.
NOTE Information on QA/QC procedures is provided in ISO 14385-1 and ISO 14385-2.
8.2 Sampling
8.2.1 Sampling location

The sampling site shall be in an accessible location where a representative measurement can be made.

In addition, the sampling location shall be chosen with regard to the safety of the personnel involved.

8.2.2 Representative sampling

It is necessary to ensure that the gas concentrations measured are representative of the average

conditions inside the flue gas duct.

NOTE The selection of sampling points for representative sampling is described e.g. in ISO 10396, where gas

stratification, fluctuations in gas velocity, temperature and others are discussed.

8.3 Calculation
8.3.1 Conversion from volume to mass concentration for NO

Results of the measurement for NO shall be expressed as mass concentrations at refere

...

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