ISO/TR 17910:2024

Technical
Report
ISO/TR 17910
First edition
Natural gas — Coal-based synthetic
2024-01
natural gas quality designation
and the applicability of ISO/TC 193
standards
Gaz naturel — Désignation de la qualité du gaz naturel
synthétique à base de charbon et applicabilité des normes de
l'ISO/TC 193
Reference number
© ISO 2024
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and units. 4
5 Brief introduction to CBSNG . 4
5.1 The production progress of CBSNG .4
5.2 The distribution of CBSNG .5
5.3 Components and composition range of typical CBSNG .6
6 Applicability of sampling standard . 6
7 Applicability of test and calculation standard . 7
7.1 General .7
7.2 Gas composition .7
7.2.1 General .7
7.2.2 Major components .7
7.2.3 Minor components .9
7.2.4 Trace constituents .11
7.3 Gas properties . 12
7.3.1 General . 12
7.3.2 Physical properties. 12
7.4 Solid particulate matter .14
Annex A (informative) Technical requirements and test methods for CBSNG .15
Annex B (informative) Test methods for hydrogen .16
Annex C (informative) Test methods for ammonia . 17
Annex D (informative) Applicability of interchangeability .18
Bibliography .21

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 193, Natural gas, Subcommittee SC 1, Analysis
of natural gas.
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
Coal-based synthetic natural gas (CBSNG) is a natural gas substitute. It refers to a natural gas-like mixture
that is synthesized from coal. After gasification or coking, the coal releases gas that mainly contains CO, CO
and H . Then after the gas cleaning, the water gas shift and methanation process consecutively, the final
product is coal based synthetic natural gas.
During the production process, the sulphur, CO , particle and NO emission can be controlled to a very low
2 x
level compared to the direct utilization of coal. So the CBSNG can be considered as a clean energy resource.
At present, the production of CBSNG is mainly in the United States and China. There are plans of CBSNG
projects also in South Korea, Ukraine, and Brazil.
Typical CBSNG contains more than 90 % methane and up to 5 % hydrogen, as well as a small portion of
nitrogen and carbon dioxide, minor ethane, propane and traces of ammonia. This document aims to promote
communication and coordination among countries, and to support the smooth progress of natural gas
substitute development, production and custody transfer.

v
Technical Report ISO/TR 17910:2024(en)
Natural gas — Coal-based synthetic natural gas quality
designation and the applicability of ISO/TC 193 standards
1 Scope
This document introduces the production process, the distribution and quality designation of coal-based
synthetic natural gas (CBSNG) in many places around the world, and examines whether ISO/TC 193
standards for sampling, test and calculation methods are applicable to the CBSNG product.
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 14532, Natural gas — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14532 and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
natural gas
NG
complex gaseous mixture of hydrocarbons, primarily methane, but generally includes ethane, propane and
higher hydrocarbons, and some non-combustible gases such as nitrogen and carbon dioxide
Note 1 to entry: Natural gas can also contain components or containments such as sulfur compounds and/or other
chemical species.
[SOURCE: ISO 14532:2014, 2.1.1.1]
3.2
indirect sampling
sampling in situations where there is no direct connection between the natural gas to be sampled and the
analytical unit
[SOURCE: ISO 14532:2014, 2.3.1.2]
3.3
representative sample
sample having the same composition as the natural gas sample when the latter is considered as a
homogeneous whole
[SOURCE: ISO 14532:2014, 2.3.4.2]

3.4
electrochemical detector
ED
detector consisting of an electrochemical cell that responds to certain substances contained in the carrier
gas eluting from the column
Note 1 to entry: The electrochemical process can be an oxidation, reduction, or a change in conductivity. The detection
can be very specific depending on the electrochemical process involved.
[SOURCE: ISO 14532:2014, 2.4.7]
3.5
main component
major component
component whose content influences physical properties
[SOURCE: ISO 14532:2014, 2.5.2.2.1]
3.6
minor component
component whose content does not significantly influence the calculation of physical properties
[SOURCE: ISO 14532:2014, 2.5.2.2.2]
3.7
trace constituent
component present at very low levels
[SOURCE: ISO 14532:2014, 2.5.2.2.3]
3.8
total sulfur
total amount of sulfur found in coal bed methane
[SOURCE: ISO 14532:2014, 2.5.2.3.14]
3.9
compression factor
ratio of the volume of an arbitrary mass of gas at a specified pressure and temperature to the volume of the
same mass of gas under the same conditions as calculated from the ideal-gas law
[SOURCE: ISO 14532:2014, 2.6.2.2]
3.10
density
mass of gas divided by its volume at specified conditions of pressure and temperature
[SOURCE: ISO 14532:2014, 2.6.3.1]
3.11
relative density
ratio of the mass of a gas contained within an arbitrary volume to the mass of dry air of standard composition
that would be contained in the same volume at the same reference conditions
[SOURCE: ISO 14532:2014, 2.6.3.2]
Note 1 to entry: The dry air of standard composition is defined in ISO 6976.

3.12
Wobbe index
calorific value on a volumetric basis at specified reference conditions, divided by the square root of the
relative density at the same specified metering reference conditions
[SOURCE: ISO 14532:2014, 2.6.4.3]
3.13
water dew point
temperature at a specified pressure at which water vapour condensation initiates
Note 1 to entry: For any pressure lower than the specified pressure, there is no condensation of water vapours at this
water dew point temperature.
[SOURCE: ISO 14532:2014, 2.6.5.1.1]
3.14
water content
mass concentration of the total amount of water contained in a gas
Note 1 to entry: Water content is expressed in units of mass per unit volume.
Note 2 to entry: For gas below the water dew point, this means water in the form of both liquid and vapour; but for gas
above the water dew point, this means only water vapour.
Note 3 to entry: Water content can be also expressed as mole or volume fraction.
[SOURCE: ISO 14532:2014, 2.6.5.1.2]
3.15
hydrocarbon dew point
HCDP
temperature at a specified pressure at which hydrocarbon vapour condensation initiates
Note 1 to entry: In chemical thermodynamics, the “true” hydrocarbon dew point is the temperature (at a stated
pressure) at which the fugacity of the gas and liquid phases is identical. Since measurement of the dew point involves
reduction of the system temperature, this equates to the temperature at which the first appearance of the liquid phase
occurs. At this point, the quantity of liquid phase is infinitesimally small. Since no instrument or observer is able to
detect this infinitesimally small amount, the measured value by a chilled mirror instrument (measured hydrocarbon
dew point) differs from the “true” hydrocarbon dew point. Depending on the gas composition and the sensitivity of the
detection system of the automatic hydrocarbon-dew-point chilled-mirror instrument or the observer (manual chilled
mirror instrument), the measured hydrocarbon dew point can be considerably lower than the “true” hydrocarbon dew
point.
[SOURCE: ISO 14532:2014, 2.6.5.2.1]
3.16
potential hydrocarbon liquid content
PHLC
property of natural gas defined as the amount of the condensable liquid (in milligrams) at the pressure,
p, and temperature, T, per unit volume of gas at normal conditions, that is, at a temperature of 0 °C and a
pressure of 101,325 kPa obtained by passing a representative sample of the gas through an apparatus where
it is first brought to the pressure, p, and then cooled to the temperature, T
Note 1 to entry: It is necessary to take care that only gas, not a two-phase mixture, has been withdrawn from the
pipeline.
[SOURCE: ISO 14532:2014, 2.6.5.2.3]

3.17
interchangeability
measure of the degree to which the combustion characteristics of one gas resemble those of another gas
Note 1 to entry: Two gases are said to be interchangeable when one gas may be substituted for the other without
affecting the operation of gas burning appliances or equipment.
[SOURCE: ISO 14532:2014, 2.7.1]
3.18
coal based synthetic natural gas
CBSNG
gaseous mixture synthesized from coal, primarily methane and hydrogen, but generally includes ethane and
some non-combustible gases such as nitrogen and carbon dioxide
4 Symbols and units
Symbol Meaning and units
D Density (kg/m )
G Relative density
H Molar basis calorific value (kJ/mol)
c
H Mass basis calorific value (MJ/kg)
m
H Volumetric basis calorific value (MJ/m )
v
M molar mass (kg/kmol)
p (Absolute) pressure (kPa)
t Celsius temperature (°C)
T Thermodynamic (absolute) temperature (K)
V (Gas) volume (m )
W Wobbe index (MJ/m )
Z Compression factor
5 Brief introduction to CBSNG
5.1 The production progress of CBSNG
CBSNG is a natural gas (NG) substitute, the main component of which is methane. Through gasification, the
water gas shift, gas cleaning and methanation, CBSNG can be produced from coal and water.
The production process of CBSNG is shown in Figure 1 and as follows: after the raw coal is broken and
screened, it enters the coal gasification unit to produce raw syngas. The vaporizing agent in the gasifier is
the medium pressure steam and oxygen produced by the air separation unit. After passing through the gas
cleaning unit to remove particulate and tar, the raw syngas then enters into the water-gas shift unit to shift
the gas to meet the H /CO ratio requirement of the methanation process, and a stream of steam is used to
recover the reaction energy of water-gas shift process.
The shift syngas exiting the water-gas shift unit goes into the gas cleaning unit to remove most of the acid
gas. The clean shift gas from the gas cleaning unit is mainly CO and H , which enters into the methanation
unit to produce synthetic natural gas. After the dehydration and compression, the final gas is the CBSNG
product.
The typical mole fraction of intermediate gases in the CBSNG production process is listed in Table 2.

Key
1 raw syngas
2 shift syngas
3 clean shift syngas
NOTE 1,2,3 represent intermediate gases in Table 1.
Figure 1 — The CBSNG production process diagram
Typical methanation process has four reactors. The CH mole fraction in cleaning syngas gradually increases
to more than 90 percent when the gas is moving forward in these methanation reactors.
Table 1 — Typical mole fraction of intermediate gases and CBSNG in the CBSNG production process
Mole fraction
%
Component
1 2 3 CBSNG
O 0,20 0,06 0,09 0,012
N 0,06 0,04 0,06 0,13
CH 12,51 11,54 18,05 98,37
CO 34,60 36,10 1,06 0,60
CO 14,70 12,98 20,34 —
C H 0,43 0,07 0,11 —
2 6
C H 0,10 0,01 0,01 —
3 8
H 37,50 39,20 61,30 0,88
5.2 The distribution of CBSNG
There are five CBSNG projects in production globally which have a production of 6,867 billion cubic meters
per year. These projects are mainly distributed in Neimenggu and Xinjiang in China and North Dakota in the
U.S.A. More detailed information of these five projects is as follows.
There are four production lines that have been put into use in China. The designed production is about two
billion cubic meters a year per project, and are being put to use step-by-step. Until 2020, the total production
that has been put to use is 5,12 billion cubic meters per year in China.
There is a CBSNG project in the USA which has been working since 1984 and has a production of 1,76 billion
cubic meters a year.
All the CBSNG product from the five projects in production enter pipelines to mix with natural gas to be
transported and consumed.
Table 2 — Information of five projects in production globally
Location Production since Designed production Real production
1,335 billion m /y
Neimenggu, China 2013 4,0 billion m /y
(first step)
1,375 billion m /y
Xinjiang, China 2013 5,5 billion m /y
(first step)
0,4 billion m /y
Neimenggu, China 2014 2,0 billion m /y
(first step)
3 3
Xinjiang, China 2017 2,0 billion m /y 2,0 billion m /y
3 3
North Dakota, United States 1984 7,0 million m /d 1,757 billion m /y
There are also four projects under construction with a total capacity about 6,5 billion cubic meters per
year. There are 18 planned CBSNG projects with a total capacity about 72,3 billion cubic meters per year.
Except one project under construction from South Korea and one project in the planning from Mongolia, the
projects under construction and in planning are mainly in China.
5.3 Components and composition range of typical CBSNG
The CBSNG composition from the five projects in production has been studied. The results are shown in
Table 3.
Table 3 — Components and range of composition of CBSNG product of 5 projects in operation
Components and range of composition
mol%
Location
CH H CO N CO O C H
4 2 2 2 2 2 6
Qinghua, Xinjiang, China 98,10 1,16 0,64 0,10 — — 0,012 9
Datang, Neimenggu,
97,86 0,83 0,7 0,18 — — —
China
Xingtian, Xinjiang, China <94 <2,2 <2 <2 <0,01 <0,2 —
Huineng, Neimenggu,
95,4~98,6 0,26~2,07 0,036~0,319 — 0,001~0,143 — —
China
The Great Plains, North
94,8~96,1 2,4~3,98 0,41~1,26 0,03~0,35 0~0,03 — —
Dakota, United States
The three conclusions that can be drawn on the gas quality of CBSNG from Table 3 are:
1) There will be more than 90 % CH and small percentage of H in CBSNG. The content of CO in CBSNG is
4 2 2
similar to that in natural gas.
2) The CO in CBSNG is at trace level.
3) There is no hydrocarbon higher than ethane in CBSNG.
6 Applicability of sampling standard
ISO 10715 provides concise guidelines for the collection, conditioning and handling of representative
samples of processed natural gas streams. It also contains guidelines for sampling strategy, probing the
location and the handling and designing of the sampling equipment. According to ISO 10715, the factors
affecting sampling representativeness include: sampling material and equipment, sample containers,
sampling method, heavy hydrocarbon condensate and flow characteristics of gas sources.
For the final product, CBSNG is a kind of synthetic natural gas, which falls into the category of a natural
gas substitute in the scope of ISO/TC 193. It is basically free of heavy hydrocarbon and organic sulfur
compounds. The composition of CBSNG is simpler than that of natural gas.

Therefore, ISO 10715 is applicable to the direct and indirect sampling of CBSNG.
7 Applicability of test and calculation standard
7.1 General
This clause deals with the various parameters which may be referred to in the designation of the quality of
CBSNG according to ISO 13686. The parameters actually selected will depend upon the purpose for which
the designation is required and it is unlikely that all the parameters listed in this technical report will be
used.
7.2 Gas composition
7.2.1 General
CBSNG is composed primarily of methane and hydrogen with smaller amounts of ethane and of the
noncombustible gases carbon dioxide and nitrogen - the approximate content of each component is shown
in Table 4. The relevant ISO/TC 193 test standards for major and minor components and trace constituents,
and whether these standards are applicable to CBSNG, are shown in Tables 5, 10 and 14.
This document does not give requirements of CBSNG. For requirements, one can refer to Chinese national
[34]
standard GB/T 33445 (see Annex A).
Table 4 — Approximate content of each component of CBSNG
Component Unit Approximate content range
Methane cmol/mol >90,0
Hydrogen cmol/mol 0 to 5,0
Nitrogen cmol/mol 0 to 3,0
Carbon dioxide cmol/mol 0,1 to 2,0
Ethane cmol/mol 0 to 0,2
Propane cmol/mol 0 to 0,1
Oxygen cmol/mol 0 to 0,2
Carbon monoxide cmol/mol 0 to 0,1
Argon cmol/mol 0 to 0,1
Ammonia mg/m 0 to 50,0
Sulfur hydrogen mg/m 0 to 20,0
Total sulfur mg/m 0 to 50,0
7.2.2 Major components
Table 5 — Major components of CBSNG
Whether applicable
Component Relevant ISO/TC 193 standards
to CBSNG
Methane ISO 6974-1 to ISO 6974-6, ISO 23978 Yes
Hydrogen ISO 6974-3, ISO 6974-6, ISO 6975 Not exactly
Nitrogen ISO 6974-1 to ISO 6974-6, ISO 23978 Yes
Carbon dioxide ISO 6974-1 to ISO 6974-6, ISO 6975, ISO 23978 Yes

7.2.2.1 Methane
ISO 6974-4, ISO 6974-5, ISO 6974-6 and ISO 23978 are suitable for the determination of methane in the
range of 75 % to 100 %, 34 % to 100 %, 40 % to 100 %, and 50 % to 100 %, respectively, see Table 6.
Generally, the methane content in CBSNG is basically above 90 %.
Therefore, ISO 6974-4, ISO 6974-5, ISO 6974-6 and ISO 23978 are applicable to the determination of
methane content in CBSNG. ISO 6974-1, ISO 6974-2, and ISO 6974-3 are also applicable in the determination
of methane content in CBSNG.
Table 6 — Summary of determination range of CH by relevant ISO/TC 193 standards
Relevant ISO/TC 193 Suitable determination Whether applicable to
Content in CBSNG
standards range CBSNG
ISO 6974-4 75 % to 100 % Yes
ISO 6974-5 34 % to 100 % Yes
>90 %
ISO 6974-6 40 % to 100 % Yes
ISO 23978 50 % to 100 % Yes
7.2.2.2 Hydrogen
The scopes of ISO 6974-4 and ISO 6974-5 do not include the determination of hydrogen. ISO 6974-3,
ISO 6974-6 and ISO 6975 are suitable for the determination of hydrogen in the range of 0,001 % to 0,5 %, see
Table 7.
Generally, the hydrogen content in CBSNG is 0,1 % to 5,0 %.
Therefore, when the hydrogen content in CBSNG exceeds 0,5 %, ISO 6974-3, ISO 6974-6 and ISO 6975 are not
applicable to the determination of hydrogen content in CBSNG.
Three relevant standard hydrogen test methods from other countries or organizations can be referred to
Annex B. Two of these standards are applicable for the determination of hydrogen in the range of 0,01 % to
10,0 % and one standard is applicable for the determination of hydrogen in the range of 0,03 % to 100 %.
Table 7 — Summary of determination range of H by relevant ISO/TC 193 standards
Content in CBSNG Relevant ISO/TC 193 Suitable determination Whether applicable to
standards range CBSNG
ISO 6974-3 0,001 % to 0,5 % Not exactly
0 % to 5 % ISO 6974-6 0,001 % to 0,5 % Not exactly
ISO 6975 0,001 % to 0,5 % Not exactly
7.2.2.3 Nitrogen
ISO 6974-4, ISO 6974-5, ISO 6974-6 and ISO 23978 are suitable for the determination of nitrogen in the
ranges of 0,001
...