1、Designation: D7675 15Standard Test Method forDetermination of Total Hydrocarbons in Hydrogen by FID-Based Total Hydrocarbon (THC) Analyzer1This standard is issued under the fixed designation D7675; the number immediately following the designation indicates the year oforiginal adoption or, in the cas
2、e of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method describes a procedure for total hydro-carbons (THC) measurement in hydroge
3、n intended as a fuel forfuel cells on a methane (C1) basis. The determination of totalhydrocarbons on a C1 basis is an analytical technique where allof the hydrocarbons are assumed to have the same response asmethane. Sensitivity from 0.1 part per million (ppm(v), mole/mole) up to 1000 parts per mil
4、lion (ppm(v), mole/mole)concentration are achievable. Higher concentrations can beanalyzed using appropriate dilution techniques. This testmethod can be applied to other gaseous samples requiringanalysis of trace constituents provided an assessment ofpotential interferences has been accomplished.1.2
5、 This test method is an FID-based hydrocarbon analysismethod without the use of separation columns. Therefore, thismethod does not provide speciation of individual hydrocar-bons. Several varieties of instruments are manufactured andcan be used for this method.1.2.1 This method provides a measure of
6、total hydrocarbons“as methane,” because all hydrocarbon species are quantifiedthe same as methane response, which is the sole species usedfor calibration. Magnitude of the FID response to an atom ofcarbon is dependent on the chemical environment of this atomin the molecule. This method provides the
7、total hydrocarbonresult as if all carbon atoms are from aliphatic, aromatic,olefinic, or acetylenic compounds, where the detector responsecaused by these atoms are approximately relative to the numberof carbon atoms present in the molecule. Other types ofmolecules, including those containing oxygen
8、or chlorineatoms will respond differently and usually much lower than thecorresponding aliphatic hydrocarbon. Therefore other methods(Test Methods D7653, D7892, or equivalent) must be utilizedto determine the exact constituents of the total hydrocarbonresponse determined by this method.1.3 The prope
9、r handling of compressed gas cylinders con-taining air, nitrogen, hydrogen, or helium requires the use ofgas regulators to preclude over-pressurization of any instru-ment component1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstand
10、ard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenc
11、ed Documents2.1 ASTM Standards:2D7653 Test Method for Determination of Trace GaseousContaminants in Hydrogen Fuel by Fourier TransformInfrared (FTIR) SpectroscopyD7606 Practice for Sampling of High Pressure Hydrogenand Related Fuel Cell Feed GasesD7892 Test Method for Determination of Total OrganicH
12、alides, Total Non-Methane Hydrocarbons, and Formal-dehyde in Hydrogen Fuel by Gas Chromatography/MassSpectrometry2.2 EPA Standards:3EPA40 CRF Part 136 Appendix B: Definition and Procedurefor the Determination of the Method Detection Limit2.3 SAE Standards:4SAE J2719 Hydrogen Quality Guideline for Fu
13、el Cell Ve-hicles3. Terminology3.1 Definitions of Terms Specific to This Standard:1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.14 on Hydrogen andFuel Cells.Current edition approved Nov. 1, 2015. Published Decemb
14、er 2015. Originallyapproved in 2011. Last previous edition approved in 2011 as D7675-11. DOI:10.1520/D767515.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the sta
15、ndards Document Summary page onthe ASTM website.3Available from United States Environmental ProtectionAgency (EPA), WilliamJefferson Clinton Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20460,http:/www.epa.gov.4Available from SAE International (SAE), 400 Commonwealth Dr., Warrendale,PA 15096-00
16、01, http:/www.sae.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.1.1 C1 Hydrocarbon, na hydrocarbon carbon contentexpressed in terms of methane.3.1.2 C2 Hydrocarbon, na hydrocarbon carbon contentexpressed in terms of ethane.3.1
17、.3 contaminant, nimpurity or foreign material thatmakes a product less suitable or even unsuitable for theintended use or that adversely affects the components withinthe processing, storage, or distribution systems.3.1.4 dynamic calibration, ncalibration of an analyticalsystem using calibration gas
18、standard concentrations generatedby diluting known concentration compressed gas standardswith purified inert gas.3.1.5 gaseous fuel , nhydrogen used as a fuel source forthe operation of the flame ionization detector.3.1.6 gauge pressure, npressure measured above ambientatmospheric pressure. Zero gau
19、ge pressure is equal to ambientatmospheric (barometric) pressure.3.1.7 pressurized sampling, ncollection of a sample in acontainer with a (final) container pressure above atmosphericpressure.3.1.8 Shewart Control Chart, nstatistical tool for moni-toring and improving quality, originated by Walter Sh
20、ewart in1924.3.1.9 static calibration, ncalibration of an analytical sys-tem using standards in a matrix, state, or manner different thanthe samples to be analyzed.3.1.10 student t-test, na t-test is any statistical hypothesistest in which the test statistic follows a students t distributionif the n
21、ull hypothesis is supported.4. Summary of Test Method4.1 A hydrogen gas sample is analyzed via appropriate gasinlet system by a total hydrocarbon analyzer and compared toa reference standard mixture of known composition.4.2 The total hydrocarbon analyzer utilizes the flame ion-ization method of dete
22、ction. The sensor is a burner in which aregulated flow of sample gas passes through a flame sustainedby regulated flows of air and a fuel gas (hydrogen or ahydrogen/diluent mixture). Within the flame, the hydrocarboncomponents of the sample stream undergo a complex ioniza-tion that produces electron
23、s and positive ions. Polarizedelectrodes collect these ions, causing current to flow throughelectronic measuring circuitry. The ionization current is pro-portional to the rate at which carbon atoms enter the burner,and is therefore a measure of the concentration of hydrocar-bons in the original samp
24、le, present as methane. The analyzerprovides a readout on a front panel digital display and aselectable output for an accessory recorder.4.3 To ensure stable, drift-free operation, particularly inhigh-sensitivity applications, an internal temperature controllermaintains the analyzer interior at a co
25、nstant temperature. Atemperature of 50 6 1C is appropriate. This feature minimizestemperature-dependent variations in electronic current measur-ing circuitry and adsorption/desorption equilibrium of back-ground hydrocarbons within the internal flow system.4.4 To minimize system response time, an int
26、ernal samplebypass feature provides high velocity sample flow through theanalyzer.4.5 This test method determines total carbon, and all of thehydrocarbons are assumed to have the same response asmethane. Therefore, if the THC result is 1 ppm(v) and thehydrocarbon was methane (CH4) there would be 1 m
27、ole ofmethane/mole of hydrogen. However, if the THC result is 1ppm(v) and as an example, the hydrocarbon was propane(C3H8), there would be 0.36 mole of propane per mole ofhydrogen.5. Significance and Use5.1 Low operating temperature fuel cells such as protonexchange membrane fuel cells (PEM-FC) requ
28、ire high purityhydrogen for maximum material performance and lifetime.Analysis to 0.1 part per million (ppm(v) concentration of totalhydrocarbons (measured as methane) in hydrogen is necessaryfor ensuring a feed gas of sufficient purity to satisfy fuel cellsystem needs as defined in SAE J2719 or as
29、specified inregulatory codes.5.2 Dynamic dilution techniques using highly accurate massflow controllers can be used with test samples that have totalhydrocarbon content exceeding the upper limit of the instru-ments linear range, without the need to recalibrate the instru-ment using higher levels of
30、calibration standards. The samplecan be diluted with a high purity grade of hydrogen (99.999 %,so long as it contains 0.1 ppm(v) total hydrocarbons) toachieve a result of the total hydrocarbon content by applyingthe appropriate dilution factor to the result. Samples thatcontain total hydrocarbon con
31、centrations greater than1000 ppm(v) may be determined, although results will likey beachieved with reduced precision and should be analyzed by thedilution method.5.3 Although not intended for application to gases otherthan hydrogen, techniques within this test method can beapplied to other non-hydro
32、carbon gas samples requiring totalhydrocarbon content determination. This can be achieved byusing a zero gas and a calibration gas that consist of the samebackground gas as the actual sample. As an example, for thetotal hydrocarbon determination of nitrogen, the instrumentzero point must be determin
33、ed with a high purity grade ofnitrogen (99.999 % and 0.1 ppm(v) total hydrocarbons) andthe instrument calibration must be done with a certifiedstandard of methane in nitrogen in the appropriate range. Thiswill correct for any interferences caused by the backgroundgas.6. Apparatus6.1 InstrumentAny in
34、strument of standard manufacture,with hardware necessary for interfacing to a pressurizedhydrogen sample and containing all the features necessary forthe intended application(s) can be used.6.1.1 This method uses a Flame Ionization Detector (FID).The principle components of the burner are the manifo
35、ld,burner jet, and the collector. Streams of sample, fuel, and airdelivered by the analyzer flow system are routed throughinternal passages in the manifold and into the interior of theD7675 152burner (see Fig. 1). Here the sample and fuel pass through theburner jet and into the flame; the air stream
36、 flows around theperiphery of the flame.6.1.2 The burner jet and the collector function as electrodes.The jet is connected to the positive terminal of a polarizingvoltage. The collector is connected to the signal amplifier. Thetwo polarized electrodes establish an electrostatic field in thevicinity
37、of the flame. The field causes the charged particlesformed during combustion to migrate. Electrons go to theburner jet; positive ions go to the collector. Thus a smallionization current flows between the two electrodes. Magni-tude of the current depends on the concentration of carbonatoms in the sam
38、ple. The burner current serves as the inputsignal to the electronic measuring circuitry.6.2 Detector Gas ControlConstant flow control of detec-tor gases is critical for optimum and consistent analyticalperformance. Control is achieved by use of pressure regulatorsand flow controllers. The gas flow i
39、s measured by appropriatemeans and adjusted as necessary.6.3 Data AcquisitionData acquisition and storage can beaccomplished using a number of devices and media. Followingare some examples.6.3.1 RecorderA0 to 1 mV range recording potentiometeror equivalent can be used.6.3.2 Data StorageMost instrume
40、nts come equipped withan RS-232 port. This allows the instrument to report its data toa computer or to a serial printer for data storage.7. Reagents and Materials7.1 A high purity grade of hydrogen that meets 99.999 %minimum purity and 0.1 ppm(v) total hydrocarbon content.(WarningExtremely flammable
41、 gas under high pressure.)7.2 A high purity grade of compressed air with less than 0.1ppm(v) total hydrocarbon content. (WarningCompressedgas under high pressure that supports combustion.)7.3 Reference StandardsThe calibration standards usedfor this test method are standard mixtures of methane inhyd
42、rogen traceable to NIST or another national metrologyinstitute. Recommended methane concentrations used in thistest method are listed in Table 1.Accuracy of the standard mustbe 1% or better. (WarningExtremely flammable gas underhigh pressure.)TABLE 1 Zero Span Gas Used for CalibrationZERO SPANHydrog
43、en99.999%;0.1 ppm(v) THC10 2 ppm(v) Methane BalanceHydrogen7.4 Other concentrations of methane in hydrogen as needed.7.5 The use of oxygen scrubbers, water dryers, and hydro-carbon scrubbers are used in all gases supplied to the totalhydrocarbon analysis system. Follow supplier instructions inthe us
44、e of such gas purifiers and replace as necessary.8. Hazards8.1 Compressed gas cylinders should only be handled inwell-ventilated locations away from sparks and flames. Im-proper handling of compressed gas cylinders containing air,nitrogen, hydrogen, or helium can result in explosion. Rapidrelease of
45、 nitrogen or helium can result in asphyxiation.Compressed air supports combustion.8.2 The hydrogen delivery system must be leak-free or aflammable situation could occur. Safety measures such ashydrogen monitors are recommended to ensure that potentiallycombustible gas mixtures do not come in contact
46、 with anyignition source9. Preparation of Apparatus9.1 Set up the instrumentation and optimize the FID inaccordance with the manufacturers instruction or as specifiedherein. Optimization of the FID and a check of linearity (see10.1.1) should occur after installation and after any mainte-nance is per
47、formed on the instrument. If applicable on thespecific instrument, use the maximum sensitivity settings toachieve the lowest possible detection limit.9.1.1 Start-up instrument according to manufacturersspecifications.9.1.2 Turn on the hydrogen fuel and air cylinders todetector. Ensure flow settings
48、are according to manufacturerFIG. 1 Typical FID Burner DiagramD7675 153specifications. Typical flow settings for flame ionization detec-tors are 25 mL/min for hydrogen and 250 mL/min for air.9.1.3 Ignite detector. Flame ignition is indicated by a lowpopping sound. Allow sufficient time for the instr
49、ument andelectronics to stabilize.9.1.4 Proceed to calibration and sample analysis.10. Calibration and Standardization10.1 CalibrationThe instrument shall be calibrated eachday that it is used with zero gas (hydrogen, 99.999 % minpurity, 0.1 ppm(v) THC) and span gas certified standards.Most instruments make it possible to adjust the zero and spangain so that the displayed percent of full scale is the same as theppm(v) concentration in the standards. In most cases, astandard of 10 ppm(v) CH4balance H2with 1% accuracy isused for the span gas. This wi
