SIST ISO 10849:2023
(Main)Stationary source emissions - Determination of the mass concentration of nitrogen oxides in flue gas - Performance characteristics of automated measuring systems
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
Emisije nepremičnih virov - Določanje masne koncentracije dušikovih oksidov v dimnih plinih - Delovne karakteristike avtomatskih merilnih sistemov
Ta dokument določa metodo za določanje dušikovih oksidov (NOx) v dimnih plinih iz nepremičnih virov ter opisuje temeljno strukturo in ključne delovne karakteristike avtomatskih merilnih sistemov.
Metoda omogoča neprekinjen nadzor s trajno vgrajenimi sistemi za merjenje emisij NOx.
Ta dokument opisuje ekstraktivne sisteme ter sisteme in situ (ne ekstraktivne) v povezavi z analizatorji, ki delujejo na primer z naslednjimi načeli:
– kemoluminiscenca (CL);
– infrardeča absorpcija (NDIR);
– infrardeča spektroskopija s Fourierjevo transformacijo (FTIR);
– infrardeča absorpcija (NDUV);
– diferencialna optična absorpcijska spektroskopija (DOAS).
Uporabiti je mogoče tudi druge instrumentalne metode, kot so tehnike laserske spektroskopije, če izpolnjujejo minimalne zahteve glede delovanja, določene v tem dokumentu. Merilni sistem je mogoče potrditi z referenčnim gradivom v skladu s tem dokumentom ali s primerljivimi metodami.
V tej aplikaciji se za uporabo merilnih območij uspešno uporabljajo avtomatski merilni sistemi (AMS), ki temeljijo na zgornjih načelih, kot je prikazano v dodatku F.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-september-2023
Nadomešča:
SIST ISO 10849:1996
Emisije nepremičnih virov - Določanje masne koncentracije dušikovih oksidov v
dimnih plinih - Delovne karakteristike avtomatskih merilnih sistemov
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
Ta slovenski standard je istoveten z: ISO 10849:2022
ICS:
13.040.40 Emisije nepremičnih virov Stationary source emissions
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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 2022
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Published in Switzerland
ii
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
x
Annex G (informative) Calculation of uncertainty of measurement of NO and/NO or NO .41
2 x
Bibliography .47
iii
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.
iv
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.
v
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
x
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
x
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
— 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.]
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.
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
i
K Coverage factor
N Number of measurements
s Standard deviation of repeatability
r
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)
M
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)
x
Average of the measured values x
i
x ith measured value
i
x Average of the measured value at level i
i
x Value estimated by the regression line at level i
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
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
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
— 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 reference conditions.
If the NO concentration is provided as a volume fraction, Formula (1) shall be used to convert volume
−6
fraction of NO (10 ), φ , to NO mass concentrations, γ ,:
NO NO
γ =φ · M / V (1)
NO NO NO M
where
γ is the NO mass concentration at standard conditions in mg/m (273,15 K; 101,325 kPa);
NO
−6
φ is the volume fraction of NO (by volume, 10 );
NO
M is the molar mass of NO (= 30,0 g/mol);
NO
V is the molar volume (= 22,4 l/mol at 273,15 K and 101,325 kPa).
M
If necessary, the NO concentration measured in the wet gas should be corrected to the NO concentration
at standard conditions (dry gas), using Formula (2):
100 %
γγ= ⋅ (2)
RNO
100 %− h
where
γ is the NO mass concentration at standard conditions in mg/m (273,15 K; 101,325 kPa; H O
R 2
corrected);
h is the absolute water vapour content (by volume) (%).
The concentration of NO measured in the wet gas can be corrected to the NO concentration at
2 2
standard conditions (dry gas), by using the Formula (2) by substituting NO for γ .
2 NO
8.3.2 Calculation of NO and NO concentrations
2 x
By using analytical instruments such as NDUV and FTIR, both NO and NO can independently be
measured.
When a sample gas flows through a converter (NO to NO) to analytical instruments such as CL and
NDIR, the total quantity of nitrogen oxides is obtained as:
[NO ] = [NO] + [NO]
x NO2
where [NO] represents the concentration of NO originated from NO in the sample gas. The
NO2 2
concentration of NO is often described as that of NO, since NO in flue gases from conventional boiler
x x
combustion systems consist of approximately 95 % NO.
When the converter is bypassed, only [NO] is obtained. The amount of NO thus can be calculated as:
[NO ] – [NO] = [NO ]
x 2
where [NO ] is derived from [NO] · (M /M ).
2 NO2 NO2 NO
9 Quality assurance and quality control procedures
9.1 General
Quality assurance and quality control (QA/QC) are important in order to ensure that the uncertainty
of the measured values for NO or NO is kept within the limits specified for the measurement task. The
results of the QA/QC procedures shall be documented.
9.2 Frequency of checks
AMS shall be adjusted and checked after the installation and then during continuous operation. Table 2
shows the minimum required test procedures and frequency of checks. The user shall implement the
relevant procedures for determination of performance characteristics or procedures described in this
clause and Annex D. The results of the QA/QC procedures shall be documented.
Table 2 — Minimum checks and minimum frequency of checks for QA/QC during the operation
Minimum frequency for perma-
Check Test procedure
nently installed AMS
Response time Once a year E.2
Standard deviation of repeatability at zero Once a year E.3.2
point
Standard deviation of repeatability at span Once a year E.3.3
point
Lack-of-fit Once a year and after any major E.4
changes or repair to the AMS, which
will influence the results obtained
significantly
Sampling system and leakage check Once a year E.12 and E.13
Beam alignment (in situ AMS only) Once a year According to manufac-
turer’s manual
a
Analysers can be checked with internal gas cells or optical filters for this determination.
Table 2 (continued)
Minimum frequency for perma-
Check Test procedure
nently installed AMS
Light intensity attenuation through cleanli- According to manufacturer’s require- According to manufac-
ness and dust load (in situ AMS only) ments or period specified by national turer’s manual
standard
Cleaning or changing of particulate filters at The particulate filters shall be According to manufac-
the sampling inlet and at the monitor inlet changed periodically depending on turer’s manual
the dust load at the sampling site.
During this filter change the filter
housing shall be cleaned.
a
Zero drift Once in the period of unattended E.6
operation or period specified by
national standard
a
Span drift Once in the period of unattended E.6
operation or period specified by
national standard
Regular maintenance of the analyser According to manufacturer’s require- According to manufac-
ments turer’s manual
a
Analysers can be checked with internal gas cells or optical filters for this determination.
The user shall implement a procedure to guarantee that the reference materials used meet the
uncertainty requirement specified in Annex D, e.g. by comparison with a reference gas of higher quality.
9.3 Calibration, validation and measurement uncertainty
The calibration and validation of the AMS shall be performed annually and after repair of the analyser
in accordance with applicable national or international standards.
Permanently installed AMS for continuous monitoring shall be calibrated by comparison with
a) an independent method of measurement or
b) a reference material.
In either case, the validation of an automated measuring system shall include the determination
of uncertainty of the measured value obtained by calibrating the AMS. Calculation of uncertainty of
measurement of NO and NO or NO is described in Annex G. The AMS shall be subject to adjustments
2 x
and functional tests in accordance with 9.2 before each calibration. This ensures that the measurement
uncertainty is representative of the application at the specific plant.
The validation shall include the determination of the uncertainty of measured values obtained by
comparison between reference gas or reference material with the AMS.
NOTE The determination of the uncertainty of measured values obtained by permanently installed AMS for
continuous monitoring on the basis of a comparison with an independent method of measurement is described,
e.g. in ISO 20988.
The uncertainty of the measured values shall meet the uncertainty criterion specified for the
measurement objective.
10 Test report
If not specified otherwise, it shall include at least the following information:
a) a reference to this document;
b) description of the measurement objective;
c) principle of gas sampling;
d) information about the analyser and description of the sampling and conditioning line;
e) identification of the analyser used, and the performance characteristics of the analyser, listed in
Table 1;
f) operating range;
g) sample gas temperature, sample gas pressure and optical path length through an optical cell (it is
needed for only in situ measurement);
h) details of the quality, purity and uncertainty in the concentration of the span gases used;
i) description of plant and process; concentration range of pollutants and potential interferences;
j) the identification and location of the sampling plane;
k) the actions taken to achieve representative samples;
l) a description of the location of the sampling point(s) in the sampling plane;
m) a description of the operating conditions of the plant process;
n) the changes in the plant operations during sampling;
o) the sampling date, time, and duration;
p) the time averaging on relevant periods;
q) the measured values;
r) the measurement uncertainty;
s) the results of any QA/QC checks conducted arising from Table 2;
t) any deviations from this document.
Annex A
(informative)
Extractive NO, NO or NO measurement systems
2 x
A.1 General
A.1.1 Cold-dry extractive system
Many variants of this exist and Figure A.1 a) is just an example of a typical arrangement of a complete
measuring system for NO. This system is suitable for use with all the analysers that are described in
6.2. When NO should be measured with a NO analyser, NO to NO converter is to be used as shown in
2 2
Figure A.1 b).
The sampling of gas shall be representative, that is, the sampling location shall be typical of the entire
duct with the guidelines given in ISO 10396. The sampling points for the measurement require a check
for homogeneity. Prior to installation the uniformity of the gas stream should be checked.
a) NO type
b) NO-NO type
Key
1 gas sampling probe 9 flow meter
2 primary filter 10 analyser
3 heating (for use as necessary) 11 outlet
4 sampling line (heated as necessary) 12 inlet for zero and span gas (preferably in front of the nozzle)
to check the complete system
5 sample cooler with condensate separator 13 inlet for zero and span gas to check the conditioning system
and the analyser
6 sampling pump 14 inlet for zero and span gas to check the analyser
7 secondary filter 15 valve
8 needle valve 16 NO /NO converter
Figure A.1 — Cold-dry extractive system (example)
The components described in A.1.2.1 to A.1.2.8 have, for example, proven to be successful for
measurements at gas-, oil- and coal-fired plants (precautions need be observed because of the high
corrosiveness of condensable acid gases, e.g. HCI, SO or NO ).
3 2
A.1.2 Components for cold-dry extractive system
A.1.2.1 Sampling probe
The sampling probe shall be made of suitable, corrosion-resistant material. For gas temperatures up to
190 °C, polytetrafluoroethylene (PTFE) is an acceptable material. At temperatures higher than 250 °C,
stainless steel and certain other materials can alter the ratio of NO: NO . In this case, ceramic or glass
material is required, if it is necessary to determine the ratio. Cooling may be considered necessary in
order to maintain the gas concentrations in the flue gas.
A.1.2.2 Filter
The filter is needed to remove the particulate matter, in order to protect the sampling system and the
analyser. The filter shall be made of ceramic, borosilicate glass or sintered metal. The filter shall be
heated above the water or acid dew-point whichever is the higher. A filter that retains particles greater
than 2 μm is recommended. The size of the filter shall be determined from the sample flow required
and the manufacturer's data on the flow rate per unit area.
The temperature of the sampling probe and the filter shall be higher by at least 10 K to 20 K than the
water or acid dew-point of the gases.
A.1.2.3 Sampling line
The sampling line shall be made of PTFE, PFA or stainless steel. The lines shall be operated at 15 K above
the dew-point of condensable substances (generally the water or acid dew-point). The tube diameter
should be appropriately sized to provide a flow rate that meets the requirements of the analysers,
under selected line length and the degree of pressure drop in the line as well as the performance of the
sampling pump used.
A.1.2.4 Moisture removal system (Sample cooler or permeation dryer)
The moisture removal system shall be used to separate water vapour from the flue gas. The dew
point shall be sufficiently below the ambient temperature to ensure that ambient air temperatures do
not affect the separation of water from the gases. A cooling temperature of 2 °C to 5 °C is suggested.
Sufficient cooling is required for the volume of gas being sampled and the amount of water vapour that
it contains.
The design of the sample gas cooler shall be such that absorption of NO in the condensate is restricted
to a minimum. This ensures that loss of NO dissolved in the condensate, which is drained from the
sample cooler, is at a minimum. The use of a permeation dryer can ensure that NO losses are minimal.
A.1.2.5 Sampling pump (corrosion-resistant)
A sampling pump is used to withdraw a continuous sample from the duct through the sampling system.
This may be a diaphragm pump, a metal bellows pump, an ejector pump, or other pump types. The
pump shall be constructed of corrosion-resistant material. The performance of the pump shall be such
that it can supply the analyser with the gas flow required. In order to reduce the transport time in the
measuring system and the risk of physicochemical transformation of the sample, the gas flow can be
greater than that required for the analytical units, and should be pulseless to ensure constant and even
flow.
For the hot-wet extractive system (A.1.3), the pump shall be operated at a minimum of 180 °C, or 10 K to
15 K above the acid dew-point of the gases.
A.1.2.6 Secondary filter
The secondary filter is needed to remove the remaining particulate material, in order to protect the
pump and the analyser. A filter that retains particles greater than 1 μm is recommended. Acceptable
materials are PTFE, borosilicate glass or sintered metals. The size of the filter shall be determined from
the sample flow required and the manufacturer's data on the flow rate per unit area.
A.1.2.7 Flow controller and flow meter
The flow controller and flow meter are used to set the required flow rate. They shall be constructed of
corrosion resistant material.
A.1.2.8 NO /NO converter
The NO /NO converter is necessary if NO shall be measured with an NO analyser (only possible in
2 2
combination with extractive system
...
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 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
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
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
x
Annex G (informative) Calculation of uncertainty of measurement of NO and/NO or NO .41
2 x
Bibliography .47
iii
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.
iv
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.
v
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
x
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
x
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
— 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.]
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.
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
i
K Coverage factor
N Number of measurements
s Standard deviation of repeatability
r
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)
M
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)
x
Average of the measured values x
i
x ith measured value
i
x Average of the measured value at level i
i
x Value estimated by the regression line at level i
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
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
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
— 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 reference conditions.
If the NO concentration is provided as a volume fraction, Formula (1) shall be used to convert volume
−6
fraction of NO (10 ), φ , to NO mass concentrations, γ ,:
NO NO
γ =φ · M / V (1)
NO NO NO M
where
γ is the NO mass concentration at standard conditions in mg/m (273,15 K; 101,325 kPa);
NO
−6
φ is the volume fraction of NO (by volume, 10 );
NO
M is the molar mass of NO (= 30,0 g/mol);
NO
V is the molar volume (= 22,4 l/mol at 273,15 K and 101,325 kPa).
M
If necessary, the NO concentration measured in the wet gas should be corrected to the NO concentration
at standard conditions (dry gas), using Formula (2):
100 %
γγ= ⋅ (2)
RNO
100 %− h
where
γ is the NO mass concentration at standard conditions in mg/m (273,15 K; 101,325 kPa; H O
R 2
corrected);
h is the absolute water vapour content (by volume) (%).
The concentration of NO measured in the wet gas can be corrected to the NO concentration at
2 2
standard conditions (dry gas), by using the Formula (2) by substituting NO for γ .
2 NO
8.3.2 Calculation of NO and NO concentrations
2 x
By using analytical instruments such as NDUV and FTIR, both NO and NO can independently be
measured.
When a sample gas flows through a converter (NO to NO) to analytical instruments such as CL and
NDIR, the total quantity of nitrogen oxides is obtained as:
[NO ] = [NO] + [NO]
x NO2
where [NO] represents the concentration of NO originated from NO in the sample gas. The
NO2 2
concentration of NO is often described as that of NO, since NO in flue gases from conventional boiler
x x
combustion systems consist of approximately 95 % NO.
When the converter is bypassed, only [NO] is obtained. The amount of NO thus can be calculated as:
[NO ] – [NO] = [NO ]
x 2
where [NO ] is derived from [NO] · (M /M ).
2 NO2 NO2 NO
9 Quality assurance and quality control procedures
9.1 General
Quality assurance and quality control (QA/QC) are important in order to ensure that the uncertainty
of the measured values for NO or NO is kept within the limits specified for the measurement task. The
results of the QA/QC procedures shall be documented.
9.2 Frequency of checks
AMS shall be adjusted and checked after the installation and then during continuous operation. Table 2
shows the minimum required test procedures and frequency of checks. The user shall implement the
relevant procedures for determination of performance characteristics or procedures described in this
clause and Annex D. The results of the QA/QC procedures shall be documented.
Table 2 — Minimum checks and minimum frequency of checks for QA/QC during the operation
Minimum frequency for perma-
Check Test procedure
nently installed AMS
Response time Once a year E.2
Standard deviation of repeatability at zero Once a year E.3.2
point
Standard deviation of repeatability at span Once a year E.3.3
point
Lack-of-fit Once a year and after any major E.4
changes or repair to the AMS, which
will influence the results obtained
significantly
Sampling system and leakage check Once a year E.12 and E.13
Beam alignment (in situ AMS only) Once a year According to manufac-
turer’s manual
a
Analysers can be checked with internal gas cells or optical filters for this determination.
Table 2 (continued)
Minimum frequency for perma-
Check Test procedure
nently installed AMS
Light intensity attenuation through cleanli- According to manufacturer’s require- According to manufac-
ness and dust load (in situ AMS only) ments or period specified by national turer’s manual
standard
Cleaning or changing of particulate filters at The particulate filters shall be According to manufac-
the sampling inlet and at the monitor inlet changed periodically depending on turer’s manual
the dust load at the sampling site.
During this filter change the filter
housing shall be cleaned.
a
Zero drift Once in the period of unattended E.6
operation or period specified by
national standard
a
Span drift Once in the period of unattended E.6
operation or period specified by
national standard
Regular maintenance of the analyser According to manufacturer’s require- According to manufac-
ments turer’s manual
a
Analysers can be checked with internal gas cells or optical filters for this determination.
The user shall implement a procedure to guarantee that the reference materials used meet the
uncertainty requirement specified in Annex D, e.g. by comparison with a reference gas of higher quality.
9.3 Calibration, validation and measurement uncertainty
The calibration and validation of the AMS shall be performed annually and after repair of the analyser
in accordance with applicable national or international standards.
Permanently installed AMS for continuous monitoring shall be calibrated by comparison with
a) an independent method of measurement or
b) a reference material.
In either case, the validation of an automated measuring system shall include the determination
of uncertainty of the measured value obtained by calibrating the AMS. Calculation of uncertainty of
measurement of NO and NO or NO is described in Annex G. The AMS shall be subject to adjustments
2 x
and functional tests in accordance with 9.2 before each calibration. This ensures that the measurement
uncertainty is representative of the application at the specific plant.
The validation shall include the determination of the uncertainty of measured values obtained by
comparison between reference gas or reference material with the AMS.
NOTE The determination of the uncertainty of measured values obtained by permanently installed AMS for
continuous monitoring on the basis of a comparison with an independent method of measurement is described,
e.g. in ISO 20988.
The uncertainty of the measured values shall meet the uncertainty criterion specified for the
measurement objective.
10 Test report
If not specified otherwise, it shall include at least the following information:
a) a reference to this document;
b) description of the measurement objective;
c) principle of gas sampling;
d) information about the analyser and description of the sampling and conditioning line;
e) identification of the analyser used, and the performance characteristics of the analyser, listed in
Table 1;
f) operating range;
g) sample gas temperature, sample gas pressure and optical path length through an optical cell (it is
needed for only in situ measurement);
h) details of the quality, purity and uncertainty in the concentration of the span gases used;
i) description of plant and process; concentration range of pollutants and potential interferences;
j) the identification and location of the sampling plane;
k) the actions taken to achieve representative samples;
l) a description of the location of the sampling point(s) in the sampling plane;
m) a description of the operating conditions of the plant process;
n) the changes in the plant operations during sampling;
o) the sampling date, time, and duration;
p) the time averaging on relevant periods;
q) the measured values;
r) the measurement uncertainty;
s) the results of any QA/QC checks conducted arising from Table 2;
t) any deviations from this document.
Annex A
(informative)
Extractive NO, NO or NO measurement systems
2 x
A.1 General
A.1.1 Cold-dry extractive system
Many variants of this exist and Figure A.1 a) is just an example of a typical arrangement of a complete
measuring system for NO. This system is suitable for use with all the analysers that are described in
6.2. When NO should be measured with a NO analyser, NO to NO converter is to be used as shown in
2 2
Figure A.1 b).
The sampling of gas shall be representative, that is, the sampling location shall be typical of the entire
duct with the guidelines given in ISO 10396. The sampling points for the measurement require a check
for homogeneity. Prior to installation the uniformity of the gas stream should be checked.
a) NO type
b) NO-NO type
Key
1 gas sampling probe 9 flow meter
2 primary filter 10 analyser
3 heating (for use as necessary) 11 outlet
4 sampling line (heated as necessary) 12 inlet for zero and span gas (preferably in front of the nozzle)
to check the complete system
5 sample cooler with condensate separator 13 inlet for zero and span gas to check the conditioning system
and the analyser
6 sampling pump 14 inlet for zero and span gas to check the analyser
7 secondary filter 15 valve
8 needle valve 16 NO /NO converter
Figure A.1 — Cold-dry extractive system (example)
The components described in A.1.2.1 to A.1.2.8 have, for example, proven to be successful for
measurements at gas-, oil- and coal-fired plants (precautions need be observed because of the high
corrosiveness of condensable acid gases, e.g. HCI, SO or NO ).
3 2
A.1.2 Components for cold-dry extractive system
A.1.2.1 Sampling probe
The sampling probe shall be made of suitable, corrosion-resistant material. For gas temperatures up to
190 °C, polytetrafluoroethylene (PTFE) is an acceptable material. At temperatures higher than 250 °C,
stainless steel and certain other materials can alter the ratio of NO: NO . In this case, ceramic or glass
material is required, if it is necessary to determine the ratio. Cooling may be considered necessary in
order to maintain the gas concentrations in the flue gas.
A.1.2.2 Filter
The filter is needed to remove the particulate matter, in order to protect the sampling system and the
analyser. The filter shall be made of ceramic, borosilicate glass or sintered metal. The filter shall be
heated above the water or acid dew-point whichever is the higher. A filter that retains particles greater
than 2 μm is recommended. The size of the filter shall be determined from the sample flow required
and the manufacturer's data on the flow rate per unit area.
The temperature of the sampling probe and the filter shall be higher by at least 10 K to 20 K than the
water or acid dew-point of the gases.
A.1.2.3 Sampling line
The sampling line shall be made of PTFE, PFA or stainless steel. The lines shall be operated at 15 K above
the dew-point of condensable substances (generally the water or acid dew-point). The tube diameter
should be appropriately sized to provide a flow rate that meets the requirements of the analysers,
under selected line length and the degree of pressure drop in the line as well as the performance of the
sampling pump used.
A.1.2.4 Moisture removal system (Sample cooler or permeation dryer)
The moisture removal system shall be used to separate water vapour from the flue gas. The dew
point shall be sufficiently below the ambient temperature to ensure that ambient air temperatures do
not affect the separation of water from the gases. A cooling temperature of 2 °C to 5 °C is suggested.
Sufficient cooling is required for the volume of gas being sampled and the amount of water vapour that
it contains.
The design of the sample gas cooler shall be such that absorption of NO in the condensate is restricted
to a minimum. This ensures that loss of NO dissolved in the condensate, which is drained from the
sample cooler, is at a minimum. The use of a permeation dryer can ensure that NO losses are minimal.
A.1.2.5 Sampling pump (corrosion-resistant)
A sampling pump is used to withdraw a continuous sample from the duct through the sampling system.
This may be a diaphragm pump, a metal bellows pump, an ejector pump, or other pump types. The
pump shall be constructed of corrosion-resistant material. The performance of the pump shall be such
that it can supply the analyser with the gas flow required. In order to reduce the transport time in the
measuring system and the risk of physicochemical transformation of the sample, the gas flow can be
greater than that required for the analytical units, and should be pulseless to ensure constant and even
flow.
For the hot-wet extractive system (A.1.3), the pump shall be operated at a minimum of 180 °C, or 10 K to
15 K above the acid dew-point of the gases.
A.1.2.6 Secondary filter
The secondary filter is needed to remove the remaining particulate material, in order to protect the
pump and the analyser. A filter that retains particles greater than 1 μm is recommended. Acceptable
materials are PTFE, borosilicate glass or sintered metals. The size of the filter shall be determined from
the sample flow required and the manufacturer's data on the flow rate per unit area.
A.1.2.7 Flow controller and flow meter
The flow controller and flow meter are used to set the required flow rate. They shall be constructed of
corrosion resistant material.
A.1.2.8 NO /NO converter
The NO /NO converter is necessary if NO shall be measured with an NO analyser (only possible 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.
A.1.3 Hot-wet extractive system
When analysers with a hot sample cell are used, the automated measuring system as shown in
Figure A.2 is often applied.
In addition to the cold-dry extractive system, there is also automated measuring system for the NO
x
measurement that heats the sample gas to above water and acid dew-points (or the dew-point of other
condensable substances) to avoid losses of NO . In this case, the system can be simplified. It is important
that all the components carrying the sample gas to the analyser are also heated above water and acid
dew-points.
Key
1 sampling probe, heated (if necessary)
2 particle filter (in-stack or out-stack)
3 zero and span gas inlet
4 heated sampling line
5 sampling pump, heated
6 analyser with heated sample cell
Figure A.2 — Diagram of the hot optical measuring system (example: Hot-wet type)
A.1.4 Dilution extractive system
The dilution technique is an alternative to hot gas monitoring or sample gas drying. The flue gas is
[3]
diluted with a dilution gas which shall be free from the species being measured .
The dilution ratio shall be chosen according to the objectives of the measurement and shall be compatible
with the range of the analytical unit. It shall remain constant throughout the period of the test, because
the calibration frequency of the measurement unit depends,
...
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