prEN ISO 2613-1
(Main)Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total silicon by atomic emission spectroscopy (AES) (ISO/FDIS 2613-1:2023)
Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total silicon by atomic emission spectroscopy (AES) (ISO/FDIS 2613-1:2023)
This document is applicable to the determination of the total silicon content in gaseous matrices such
as biomethane, biogas and landfill gas. Silicon is present in a gas phase contained predominantly in
siloxane compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in
liquid phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion
stable in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the
analysed gas.
This document is applicable to all stated gas matrices with silicon concentrations up to 5 mg/m3, and it
is prevalently intended for the biomethane matrices containing (0,1 to 0,5) mg/m3. It can be used for
higher concentration but then the absorption efficiency of the bubblers/impingers should be checked
before the results can be regarded as valid. The detection limit of the method is estimated as 0,05
mg/m3 based on a sample volume of 0,020 m3. All compounds present in the gas phase are volatile at
the absorption and derivatization temperature and gaseous siloxanes are trapped in absorbance media
and derivatized into analytical silicon specie are measured by this method. The concentration of the
silicon is measured in diluted derivatization media using atomic emission spectrometer upon
atomisation/ionisation in microwave or inductively coupled plasma.
Analyse von Erdgas - Siliziumgehalt von Biomethan - Teil 1: Bestimmung des Gesamtsiliziumgehalts durch AES (ISO/FDIS 2613-1:2023)
Analyse du gaz naturel - Teneur en silicium du biométhane - Partie 1: Dosage de la teneur totale en silicium par spectrométrie d'émission atomique (AES) (ISO/FDIS 2613-1:2023)
Analiza zemeljskega plina - Vsebnost silicija v biometanu - 1. del: Določevanje celotnega silicija z atomsko emisijsko spektrometrijo (AES) (ISO/FDIS 2613-1:2023)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN ISO 2613-1:2022
01-junij-2022
Analiza zemeljskega plina - Vsebnost silicija v biometanu - 1. del: Določevanje
celotnega silicija z atomsko emisijsko spektrometrijo (AES) (ISO/DIS 2613-1:2022)
Analysis of natural gas - Silicon content of biomethane - Part 1: Determination of total
silicon content by AES (ISO/DIS 2613-1:2022)Analyse von Erdgas - Siliziumgehalt von Biomethan - Teil 1: Bestimmung des
Gesamtsiliziumgehalts durch AES (ISO/DIS 2613-1:2022)
Analyse du gaz naturel - Teneur en silicium du biométhane - Partie 1: Détermination de
la teneur en silicium total par AES (ISO/DIS 2613-1:2022)Ta slovenski standard je istoveten z: prEN ISO 2613-1
ICS:
75.060 Zemeljski plin Natural gas
oSIST prEN ISO 2613-1:2022 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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oSIST prEN ISO 2613-1:2022
DRAFT INTERNATIONAL STANDARD
ISO/DIS 2613-1
ISO/TC 193/SC 1 Secretariat: NEN
Voting begins on: Voting terminates on:
2022-03-22 2022-06-14
Analysis of natural gas — Silicon content of biomethane —
Part 1:
Determination of total silicon content by AES
ICS: 75.060
This document is circulated as received from the committee secretariat.
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
ISO/CEN PARALLEL PROCESSING
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
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USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 2613-1:2022(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. © ISO 2022
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oSIST prEN ISO 2613-1:2022
ISO/DIS 2613-1:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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oSIST prEN ISO 2613-1:2022
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Contents Page
Foreword ........................................................................................................................................................................................................................................iv
Introduction .................................................................................................................................................................................................................................v
1 Scope ................................................................................................................................................................................................................................. 1
2 Normative references ..................................................................................................................................................................................... 1
3 Terms and definitions .................................................................................................................................................................................... 1
4 Principle ........................................................................................................................................................................................................................ 2
5 Reagents and labware .................................................................................................................................................................................... 2
6 Apparatus .................................................................................................................................................................................................................... 5
6.1 Sampling and derivatization equipment ......................................................................................................................... 5
6.2 MWP/ICP-AES instrument ........................................................................................................................................................... 6
6.3 Analytical balance accurate to 0,01 mg. .......................................................................................................................... 6
7 Sampling ....................................................................................................................................................................................................................... 7
8 Derivatization ......................................................................................................................................................................................................... 8
9 Analytical procedure ...................................................................................................................................................................................... 8
9.1 Set-up of the equipment .................................................................................................................................................................. 8
9.2 Calibration line ....................................................................................................................................................................................... 9
9.3 Analysis of unknown and QC samples ............................................................................................................................... 9
10 Calculation .................................................................................................................................................................................................................. 9
11 Expression of results ....................................................................................................................................................................................10
12 Precision of the method ............................................................................................................................................................................10
13 Measurement uncertainty ......................................................................................................................................................................10
14 Test report ...............................................................................................................................................................................................................11
Bibliography .............................................................................................................................................................................................................................12
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Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing documents 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.Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.© ISO 2022 – All rights reserved
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Introduction
This document describes a method for the measurement of the total concentration of silicon in
biomethane, biogas and similar gaseous matrices when used in the natural gas grids and when using it
as a transport fuel. The method is based on using a liquid impinger to accumulate the silicon from a gas
sample, followed by instrumental analysis.Due to the extensive usage of siloxane compounds, their volatility and great affinity to apolar
environments, siloxanes are considered as one of the most important impurities in biogas. They are
undesired because of their potential for abrasive SiO formation as combustion product that can
damage engines and appliances. Furthermore, some of these compounds present a health risk.
For the purpose of this document, silicon specie measured is quoted as total silicon. Silicon measured
is from siloxane compounds that are trapped from the gas phase in liquid media and derivatized into
analytical form of hexafluorosilicate (SiF ) ions which remain present in solution when analysed.
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oSIST prEN ISO 2613-1:2022
DRAFT INTERNATIONAL STANDARD ISO/DIS 2613-1:2022(E)
Analysis of natural gas — Silicon content of biomethane —
Part 1:
Determination of total silicon content by AES
1 Scope
This document is applicable to the measurement of the total silicon content in gaseous matrices such
as biomethane and biogas. Silicon is present in a gas phase contained predominantly in siloxane
compounds, trimethylsilane and trimethylsilanol. The analytical form of the silicon measured in liquid
phase after conducted sampling and derivatization procedure is soluble hexafluorosilicate anion stable
in slightly acidified media. Total silicon is expressed as a mass of silicon in the volume of the analysed
gas.This document is applicable to stated gaseous matrices with silicon concentrations up to 5 mg/m ,
3 3and it is prevalently intended for the biomethane matrices containing 0,1 mg/m to 0,5 mg/m Si. With
adaptation to ensure appropriate absorption efficiency, it can be used for higher concentrations. The
3 3detection limit of the method is estimated as 0,05 mg/m based on a gas sample volume of 0,020 m .
All compounds present in the gas phase are volatile at the absorption and derivatization temperature
and gaseous siloxanes are trapped in absorbance media and derivatized into analytical silicon that is
measured by this method. The concentration of the silicon is measured in diluted derivatization media
using atomic emission spectrometry upon atomisation/ionisation in microwave or inductively coupled
plasma.Unless specified otherwise, all volumes and concentrations refer to normal conditions.
NOTE When using appropriate dilution factors, the method can also be applied for silicon concentrations
above 5 mg/m .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 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 14532, Natural gas — VocabularyISO 10715, Natural gas — Sampling guidelines
ISO 14912, Gas analysis — Conversion of gas mixture composition data
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/
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3.1
Siloxanes
functional groups where two silicon atoms are connected via an oxygen atom
Note 1 to entry: Depending on the substrate used to produce biogas and the process used for purification,
biomethane can contain siloxanes. During combustion, siloxanes can be oxidized to silicon dioxide, an abrasive
compound harmful for mechanical moving parts in e.g. engines and turbines [8 ].3.2
atomic emission spectroscopy (AES)
a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark
at a particular wavelength to determine the quantity of an element in a sample4 Principle
WARNING — Persons using this International Standard should be familiar with normal
laboratory practice. This standard does not purport to address all of the safety problems, if any,
associated with its use. It is the responsibility of the user to establish appropriate safety and
health practices and to ensure compliance with any national regulatory conditions.
A methane matrix gas sample (e.g., biomethane, biogas, natural gas and blends thereof) containing
siloxane compounds is passed through liquid absorbent (nitric acid) in serially connected gas bubblers/
impingers to collect the silicon-containing compounds. After sampling of an adequate gas volume,
content of sampling vessels (gas bubblers) is subjected to derivatization by adding hydroxide solution
and hydrofluoric acid in order to obtain silicon in analytical from, hexafluorosilicate (SiF ) anion.
The derivatized sample is analysed for silicon content using an ICP/MWP atomic emission spectrometer
at selected characteristic silicon emission wavelengths using a multipoint calibration using a straight
line obtained from analysing a series of standard silicon solutions.5 Reagents and labware
To carry out the method, the following reagents shall be of a recognized analytical grade and only
ISO 3696 grade 1 water. If it is visually determined that the reagents have changed their appearance
(colour, consistency, turbidity) they shall be discarded, and fresh ones shall be used.
5.1 Absorber media5.1.1 Nitric acid (HNO ), ρ = 1,41 g/cm ; 65 % HNO (mass fraction) – for trace elemental analysis.
3 20 3CAUTION This chemical is especially dangerous if used outside specialized laboratory conditions.
Tests have been performed in which other non-oxo mineral acids (HCl) have been used, but they have
been shown to be inadequate for the absorption of siloxanes from the gas phase. Special precautions
are to be taken when handling this chemical in lab and field conditions.5.2 Derivatization media
5.2.1 Sodium hydroxide pellets, for the preparation of 8 mol/L – 10 mol/L hydroxide solution.
Accurately weigh an appropriate amount of sodium hydroxide pellets and dissolve these in an
appropriate amount of reagent water (5.3). As an example for 100 ml of 10 mol/l sodium hydroxide
solutions, weigh 40 g of sodium hydroxide pellets and dissolve in 100 ml water.Potassium hydroxide can also be used, but sodium hydroxide is preferred due to operation safety.
WARNING — Reaction of dissolving sodium hydroxide in water is highly exothermic! Heat will be
released and care should be taken when handling the reaction. Add pellets slowly to the water
and cool the dissolution vessel until the dissolution is complete.© ISO 2022 – All rights reserved
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5.2.2 Hydrofluoric acid (HF), ρ = 1,16 g/cm ; 48 % HF (mass fraction).
(20˚C)
WARNING — Hydrofluoric acid is a very toxic acid and penetrates the skin and tissues deeply
if not treated immediately. Injury occurs in two stages: firstly, by hydration that induces tissue
necrosis; and secondly, by penetration of fluoride ions deep into the tissue and thereby reacting
with calcium. Boric acid and/or other complexing reagents and appropriate treatment agents
should be administered immediately. Consult appropriate safety literature for determining the
proper protective eyewear, clothing and gloves to use when handling hydrofluoric acid. Always
have appropriate treatment materials readily available prior to working with this acid.
CAUTION This chemical is especially dangerous if used outside specialized laboratory conditions.
Tests have been performed in which other fluoride donor derivatization reagents (NaF) have been
used, but they have been shown to be inadequate for the derivatization of absorbed siloxanes from the
gas phase. Special precautions are to be taken when handling this chemical in lab and field conditions
5.3 Water, complying with grade 1 of ISO 36965.4 Pure siloxane compounds:
Linear siloxanes Cyclic siloxanes
Hexamethyldisiloxane - L2; C H OSi Hexamethylcyclotrisiloxane - D3; C H O Si
6 18 2 6 18 3 3
Octamethyltrisiloxane - L3; C H O Si Octamethylcyclotetrasiloxane - D4; C H O Si
8 24 2 3 8 24 4 4Decamethyltetrasiloxane - L4; C H O Si Decamethylcyclopentasiloxane - D5; C H O Si
10 30 3 4 10 30 5 5Dodecamethylpentasiloxane - L5; C H O Si Dodecamethylcyclohexasiloxane - D6;
12 36 4 5
C H O Si
12 36 6 6
Use at least one representative of chain and one representative of cyclic siloxane compounds for the
purpose of performing initial and regular quality control of the method validity.
5.5 pH colour-fixed indicator strips, pH range from 0 - 14, or, alternatively, a pH meter with HF
resistant electrode5.6 Calibration solutions
5.6.1 General
The following procedure for the preparation of standard and calibration solutions of silicon is adjusted
to the lower range of silicon concentration in gas sample. If higher concentrations of silicon shall be
measured, adjust the concentrations of the working standard and calibration solutions accordingly.
When determining silicon in aqueous samples, only plastic, PTFE or quartz labware shall be used from
time of sample collection to completion of analysis.5.6.2 Certified ICP-Si stock standard solution
Example of certified Si standard solution is (water, traces HF) 10 000 μg/ml ± 0,5 % or better. It is used
for the purpose of demonstration of the calibration solutions preparation.Certified Si standard solutions of other concentrations can also be used. Adjust the procedure for
preparing standard solution accordingly.If Si stock standard solution is prepared in-house gravimetrically from salt-containing silicon, apply
required statistical procedure for obtaining accurate concentration accompanied with uncertainty
value.[1][2]
NOTE References provide guidance.
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5.6.3 Si standard solution
ρ(Si) ≈ 100 mg/kg
Weigh empty 50 ml plastic volumetric flask using analytical balance (6.3). Add around 10 ml of 2 %
nitric acid (mass fraction). Accurately pipette 0,5 ml of stock solution (5.6.2) and add it to the plastic
volumetric flask. Dilute with 2 % nitric acid (mass fraction) to volume. Weigh full plastic volumetric
flask and calculate the concentration of silicon.Store the solution in plastic volumetric flask or similar vessel of silicon free material properly stoppered
at room temperature or refrigerated (~5 °C). The solution is stable for at least two weeks if stored
properly.5.6.4 Si calibration solutions
Gravimetrically prepare a minimum of five calibration solutions in accordance with expected silicon
concentration in the collected sample.As an example proceed as follows for the range from 10 μg /kg Si to 200 μg/kg Si:
Weigh empty 100 ml (or 200 ml) plastic volumetric flasksPipette 10 μl; 20 μl; 50 μl; 75 μl; 100 μl; 150 μl; and 200 μl; respectively of silicon standard solution
(5.6.3) into 100 ml one-mark plastic volumetric flask that was empty-weighted and prefilled with
around 10 ml - 20 ml of 2 % nitric acid (mass fraction). Dilute with 2 % nitric acid (mass fraction) to
volume. Weigh full plastic volumetric flask and calculate the concentration of silicon.
The calibration solutions contain 10 μg/kg Si; 20 μg/kg Si; 50 μg/kg Si; 75 μg/kg Si; 100 μg/kg Si; 150
μg/kg Si and 200 μg/kg Si respectively.5.6.5 Solution for wavelength calibration control
Perform wavelength check using solution containing assorted elements covering the wavelength range
of the instrumentation used provided by the manufacturer prior to daily calibration of the instrument
for the analysis of silicon. This solution is usually provided as concentrate that needs to be diluted prior
to the analysis in accordance with the manufacturer’s instructions. Wavelength calibration control test
result shows if the optical settings of the instrument are appropriate, and if the readings of the emission
lines for each individual element correspond to the instrumental settings when selecting the analytical
wavelengths for the analyte of interest.NOTE The solution for wavelength calibration control is usually provided by the manufacturer of the
equipment.5.7 Quality control
5.7.1 Blanks
Three types of blanks are used during the analysis. The calibration blank is used in establishing the
analytical curve, the laboratory reagent blank is used to assess any contamination from the sample
preparation procedure and a rinse blank is used to flush the instrument uptake system and nebulizer
between standards, check solutions, and samples to reduce memory interferences.5.7.1.1 The calibration blank is prepared by acidifying reagent water to the same concentrations
of the acids as used for the standards; in this case it is 2 % nitric acid (mass fraction). The calibration
blank should be stored in a plastic container as samples.5.7.1.2 The laboratory reagent blank should contain all the reagents in the same volumes as used
in the processing of the samples. The laboratory reagent blank shall be carried through the same entire
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preparation scheme as the samples including sample derivatization. This type of blank should be
prepared at least every time new reagents are used.5.7.1.3 The rinse blank is prepared by acidifying reagent water to the same concentrations of nitric
acid as used in the calibration blank and stored in a convenient manner.5.7.1.4 Labware blank – pure methane gas free from silicon used as blank gas sample to test the
cleanliness of labware used.5.7.2 Instrument performance check i.e. wavelength calibration control sample (see 5.6.5)
5.7.3 Calibration Control Sample (CC)A calibration control sample shall be used for initial and periodic verification of calibration standards
or stock standard solutions in order to verify instrument performance. The CC shall be obtained from
an outside source different from the standard stock solutions and prepared in the same acid mixture as
the calibration standards. It can be either ready standard solution obtained from a different supplier,
or at least from a different lot, or it can be prepared gravimetrically using pure (NH ) SiF salt. The
4 2 6concentration of the silicon in the CC solution should be near to expected concentration of silicon in the
sample or at the middle of calibration range. A fresh solution should be prepared prior to the analysis
and stored in plastic container as samples.5.7.4 Derivatization control sample (DC)
A derivatization control sample shall be used for initial and periodic verification of the completeness
of the derivatization process. For this purpose pure siloxane compounds are used. For example, L2
and D4 siloxanes represent linear and cyclic siloxanes found in biomethane matrices. Other siloxanes
may be used as well. The DC is prepared by accurately pipetting appropriate amount of siloxane with
previously calculated mass of silicon contained, and adding this amount to the aliquot of nitric acid thus
simulating the absorbance procedure. The solution of siloxane(s) is then subjected to derivatization by
adding appropriate amount of hydroxide solution and hydrofluoric sample. The DC should be stored in a
plastic container as sample. Concentration of the silicon in DC shall be within the calibration range and
can be adjusted by dilution if needed.5.7.5 Reference gas mixture of siloxanes in methane with certified silicon content, in the range
3 30,1 mg/m Si to 0,5 mg/m Si
Certified reference gas mixtures containing different siloxanes and combinations of siloxanes in
methane are available with certified siloxane amount fractions. These amount fractions can be
converted to a total silicon concentration, but it should be noted that the total silicon in the mixture
may differ, i.e. be higher due to siloxane impurities that are present as non-certified siloxanes. Such gas
mixtures are suitable for assessing the recovery of the sampling and derivatization.
ISO 14912 shall be used for the conversion of amount fractions to concentrations, including the
associated uncertainties.6 Apparatus
6.1 Sampling and derivatization equipment
An outline of the equipment for the sampling of gas is given in Figure 1. The apparatus consists of a gas
flow meter and an impinger train containing absorbent (conc. Nitric acid) to capture gaseous siloxanes.
A thermometer shall be used if the laboratory has no controlled ambient temperature within ±3 °C.
If gas flow meter used is not equipped with the embedded ambient pressure sensor providing data
for normalization to standard conditions of 273,15 K and 101,325 kPa, a barometer shall be used to
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measure atmospheric pressure during collection of the gas. Using the measured temperature and
pressure, volumes and concentrations shall be converted to appropriate standard conditions.
All tubing, gaskets and seals used to for passing of the sample gas, as well as the impingers and
derivatization vessels and stirring rod shall be made of plastic polymer silicon free.
The sampling and sample derivatization described in this document refers to the laboratory equipment
and conditions. Specialized sampling equipment may be used that allows the absorption of siloxane
from the gaseous medium in the field if the described requirements are met.Field sampling / absorption and derivatization were not covered by the study during the development
of this standard. In the case of the development of equipment that enables field sampling and
derivatization, it shall be validated in terms of applicability and minimize and avoid any losses. To
generate the best results, it is recommended to perform sampling / absorption and derivatization
procedures in the laboratory.6.1.1 Gas flow meter with temperature sensor, calibrated with methane, operating range: 0 ml/
min - 20 ml/min with the software readout of normalized values for the volume of gas
Methane calibrated gas flow meters are commercially available, which is applicable for biomethane
matrix. If a flow meter is used to read the flow of different biogas gas matrices, a calibration shall be
performed on the actual medium, i.e. a correction of sampled gas volume in relation to the composition
of the biogas.6.1.2 Gas cylinder with gas pressure regulator
Pressure regulator suitable to deliver low outlet pressure (just above the atmospheric pressure) in
order to achieve low but measurable gas flow and slow release of gas from the cylinder to keep gas
bubbles longer in the liquid absorbent to increase the absorption efficiency of siloxanes.
NOTE There a...
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