ASTM D7675-11
(Test Method)Standard Test Method for Test Method for the Determination of Total Hydrocarbons in Hydrogen by FID Based Total Hydrocarbon (THC) Analyzer
Standard Test Method for Test Method for the Determination of Total Hydrocarbons in Hydrogen by FID Based Total Hydrocarbon (THC) Analyzer
SIGNIFICANCE AND USE
Low operating temperature fuel cells such as proton exchange membrane fuel cells (PEFCs) require high purity hydrogen for maximum material performance and lifetime. Analysis to 0.1 part per million (ppm) concentration of total hydrocarbons (measured as methane) in hydrogen is necessary for assuring a feed gas of sufficient purity to satisfy fuel cell system needs as defined in SAE TIR J2719 or as specified in regulatory codes.
Although not intended for application to gases other than hydrogen, techniques within this test method can be applied to other non-hydrocarbon gas samples requiring total hydrocarbon content determination.
SCOPE
1.1 This test method describes a procedure for total hydrocarbons (THC) measurement in hydrogen intended as a fuel for fuel cells on a C1 Basis. Total Hydrocarbons on a C1 basis is an analytical technique where total carbon is determined and all of the hydrocarbons are assumed to have the same response as Methane. Sensitivity from 0.1 part per million (ppm, µmole/mole) up to 1000 parts per million (ppm, µmole/mole) concentration are achievable. Higher concentrations can be analyzed using appropriate dilution techniques. This test method can be applied to other gaseous samples requiring analysis of trace constituents provided an assessment of potential interferences has been accomplished.
1.2 This test method is a FID based hydrocarbon analysis method without the use of separation columns, therefore, this method does not provide speciation of individual hydrocarbons. Varieties of instruments are manufactured and can be used for this method.
1.2.1 This method provides a measure of total hydrocarbons “as methane”, because all hydrocarbon species are quantified the same as methane response, which is the sole species used for calibration. Therefore C2 and above hydrocarbons are quantified relative to the number of carbon atoms present in the molecule.
1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
General Information
Relations
Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D7675 − 11
StandardTest Method for
Determination of Total Hydrocarbons in Hydrogen by FID
Based Total Hydrocarbon (THC) Analyzer
This standard is issued under the fixed designation D7675; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method describes a procedure for total hydro- 2.1 ASTM Standards:
carbons(THC)measurementinhydrogenintendedasafuelfor F307 Practice for Sampling Pressurized Gas for Gas Analy-
fuel cells on a C1 Basis. Total Hydrocarbons on a C1 basis is sis
an analytical technique where total carbon is determined and F1398 Test Method for Determination of Total Hydrocarbon
all of the hydrocarbons are assumed to have the same response Contribution by Gas Distribution System Components
as Methane. Sensitivity from 0.1 part per million (ppm,
2.2 SAE Standards:
µmole/mole) up to 1000 parts per million (ppm, µmole/mole)
SAE TIR J2719 nformation Report of the Development of a
concentration are achievable. Higher concentrations can be Hydrogen Quality Guideline for Fuel Cell Vehicles
analyzed using appropriate dilution techniques. This test
3. Terminology
method can be applied to other gaseous samples requiring
analysis of trace constituents provided an assessment of
3.1 Definitions of Terms Specific to This Standard:
potential interferences has been accomplished.
3.1.1 C1 Hydrocarbon—general hydrocarbon containing
one Carbon atom.
1.2 This test method is a FID based hydrocarbon analysis
method without the use of separation columns, therefore, this 3.1.2 C2 Hydrocarbon—general hydrocarbon containing
method does not provide speciation of individual hydrocar-
two Carbon atoms.
bons. Varieties of instruments are manufactured and can be
3.1.3 contaminant—impurity that adversely affects the com-
used for this method.
ponents within the fuel cell system or the hydrogen storage
1.2.1 This method provides a measure of total hydrocarbons
system.
“as methane”, because all hydrocarbon species are quantified
3.1.4 dynamic calibration—calibration of an analytical sys-
the same as methane response, which is the sole species used
tem using calibration gas standard concentrations generated by
for calibration. Therefore C2 and above hydrocarbons are
diluting known concentration compressed gas standards with
quantifiedrelativetothenumberofcarbonatomspresentinthe
purified inert gas.
molecule.
3.1.5 fuel cell grade hydrogen—hydrogen satisfying the
1.3 The values stated in SI units are to be regarded as
specifications in SAE TIR J2719.
standard. No other units of measurement are included in this
3.1.6 gaseous fuel —hydrogen used as a fuel source for the
standard.
operation of the flame ionization detector.
1.4 This standard does not purport to address all of the
3.1.7 gauge pressure—pressure measured above ambient
safety concerns, if any, associated with its use. It is the
atmospheric pressure. Zero gauge pressure is equal to ambient
responsibility of the user of this standard to establish appro-
atmospheric (barometric) pressure.
priate safety and health practices and determine the applica-
bility of regulatory limitations prior to use.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
ThistestmethodisunderthejurisdictionofASTMCommitteeD03onGaseous contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Fuels and is the direct responsibility of Subcommittee D03.14 on Hydrogen and Standards volume information, refer to the standard’s Document Summary page on
Fuel Cells. the ASTM website.
Current edition approved March 15, 2011. Published April 2011. DOI: 10.1520/ Available from SAE International (SAE), 400 Commonwealth Dr.,Warrendale,
D7675–11. PA 15096-0001, http://www.sae.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7675 − 11
3.1.8 pressurized sampling—collection of a sample in a 4.4 To minimize system response time, an internal sample
canister with a (final) canister pressure above atmospheric bypass feature provides high velocity sample flow through the
pressure analyzer.
3.1.9 Shewart Control Chart—statistical tool for monitoring
4.5 This test method determines total carbon and all of the
and improving quality, originated by Walter Shewart in 1924
hydrocarbons are assumed to have the same response as
for the manufacturing environment and later extended to
methane. Therefore, if the THC result is 1 ppm v/v and the
quality improvement in all areas of an organization.
hydrocarbon was methane (CH4) there would be 1 µmole of
methane/mole of hydrogen. However, if the THC result is 1
3.1.10 static calibration—calibration of an analytical sys-
ppm v/v and the hydrocarbon was propane (C3H8), there
tem using standards in a matrix, state or manner different than
would be 0.33 µmole of propane/mole of hydrogen.
the samples to be analyzed.
5. Significance and Use
4. Summary of Test Method
5.1 Low operating temperature fuel cells such as proton
4.1 A hydrogen gas sample is analyzed via appropriate gas
inlet system by a total hydrocarbon analyzer and compared to exchange membrane fuel cells (PEFCs) require high purity
hydrogen for maximum material performance and lifetime.
a reference standard mixture of known composition.
Analysis to 0.1 part per million (ppm) concentration of total
4.2 The Total Hydrocarbon Analyzer—utilizes the flame
hydrocarbons (measured as methane) in hydrogen is necessary
ionization method of detection.The sensor is a burner in which
for assuring a feed gas of sufficient purity to satisfy fuel cell
aregulatedflowofsamplegaspassesthroughaflamesustained
system needs as defined in SAE TIR J2719 or as specified in
by regulated flows of air and a fuel gas (hydrogen or a
regulatory codes.
hydrogen/diluent mixture). Within the flame, the hydrocarbon
5.2 Although not intended for application to gases other
components of the sample stream undergo a complex ioniza-
tion that produces electrons and positive ions. Polarized than hydrogen, techniques within this test method can be
applied to other non-hydrocarbon gas samples requiring total
electrodes collect these ions, causing current to flow through
electronic measuring circuitry. The ionization current is pro- hydrocarbon content determination.
portional to the rate at which carbon atoms enter the burner,
and is therefore a measure of the concentration of hydrocar- 6. Apparatus
bons in the original sample, present as methane. The analyzer
6.1 Instrument—Any instrument of standard manufacture,
provides a readout on a front panel digital display and a
with hardware necessary for interfacing to a pressurized
selectable output for an accessory recorder.
hydrogen sample and containing all the features necessary for
4.3 To ensure stable, drift-free operation, particularly in the intended application(s) can be used.
6.1.1 This method uses a Flame Ionization Detector (FID).
high-sensitivity applications, an internal temperature controller
maintains the analyzer interior at a constant temperature. A The principle components of the burner are the manifold,
temperature of 50°C 6 1° is appropriate. This feature mini- burner jet and the collector. Streams of sample, fuel and air
mizes temperature-dependent variations in electronic current delivered by the analyzer flow system are routed through
measuring circuitry and adsorption/desorption equilibrium of internal passages in the manifold and into the interior of the
background hydrocarbons within the internal flow system. burner. Here the sample and fuel pass through the burner jet
FIG. 1 Typical FID Burner Diagram
D7675 − 11
and into the flame; the air stream flows around the periphery of 8.1.2 Turn on the hydrogen fuel and air cylinders to
the flame. (See Fig. 1.) detector. Insure flow settings are according to manufacturer
specifications. Typical flow settings for flame ionization detec-
6.1.2 The burner jet and the collector function as electrodes.
The jet is connected to the positive terminal of the 90 VDC tors are 25cc/min for hydrogen and 250cc/min for air.
polarizing voltage. The collector is connected to the signal 8.1.3 Ignite Detector. Flame ignition is indicated by a low
amplifier. The two polarized electrodes establish an electro-
popping sound. Allow sufficient time for the instrument and
static field in the vicinity of the flame. The field causes the electronics to stabilize.
charged particles formed during combustion to migrate. Elec-
8.1.4 Proceed to calibration and sample analysis.
tronsgototheburnerjet;positiveionsgotothecollector.Thus
a small ionization current flows between the two electrodes.
9. Calibration and Standardization
Magnitude of the current depends on the concentration of
9.1 Calibration—The instrument is calibrated daily “on-
carbon atoms in the sample. The burner current serves as the
use” with zero gas (UHPHydrogen, 99.999% min purity, < 0.1
input signal to the electronic measuring circuitry.
ppm THC) and span gas certified standards. Most instruments
6.2 Detector Gas Control—Constant flow control of detec-
make it is possible to adjust the zero and span gain so that the
tor gases is critical for optimum and consistent analytical
displayed percent of full scale is the same as the ppm/v
performance. Control is achieved by use of pressure regulators
concentration in the standards. This obviates the need for
and flow controllers. The gas flow is measured by appropriate
mathematical calculation and expedites THC analysis.
means and adjusted as necessary.
9.2 It is necessary to compare calculated results to the
6.3 Data Acquisition—Data acquisition and storage can be
certi
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.