1、Designation: D7675 11Standard Test Method forTest Method for the Determination of Total Hydrocarbons inHydrogen 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 adop
2、tion or, in the case 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) mea
3、surement in hydrogen intended as a fuel forfuel cells on a C1 Basis. Total Hydrocarbons on a C1 basis isan analytical technique where total carbon is determined andall of the hydrocarbons are assumed to have the same responseas Methane. Sensitivity from 0.1 part per million (ppm,mole/mole) up to 100
4、0 parts per million (ppm, 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 acco
5、mplished.1.2 This test method is a FID based hydrocarbon analysismethod without the use of separation columns, therefore, thismethod does not provide speciation of individual hydrocar-bons. Varieties of instruments are manufactured and can beused for this method.1.2.1 This method provides a measure
6、of total hydrocarbons“as methane”, because all hydrocarbon species are quantifiedthe same as methane response, which is the sole species usedfor calibration. Therefore C2 and above hydrocarbons arequantified relative to the number of carbon atoms present in themolecule.1.3 The values stated in SI un
7、its are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 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 pra
8、ctices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2F307 Practice for Sampling Pressurized Gas for Gas Analy-sisF1398 Test Method for Determination of Total Hydrocar-bon Contribution by Gas Distribution System Components2.2 SAE St
9、andards:3SAE TIR J2719 nformation Report of the Development of aHydrogen Quality Guideline for Fuel Cell Vehicles3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 C1 Hydrocarbongeneral hydrocarbon containingone Carbon atom.3.1.2 C2 Hydrocarbongeneral hydrocarbon containingtwo Ca
10、rbon atoms.3.1.3 contaminantimpurity that adversely affects the com-ponents within the fuel cell system or the hydrogen storagesystem.3.1.4 dynamic calibrationcalibration of an analytical sys-tem using calibration gas standard concentrations generated bydiluting known concentration compressed gas st
11、andards withpurified inert gas.3.1.5 fuel cell grade hydrogenhydrogen satisfying thespecifications in SAE TIR J2719.3.1.6 gaseous fuel hydrogen used as a fuel source for theoperation of the flame ionization detector.3.1.7 gauge pressurepressure measured above ambientatmospheric pressure. Zero gauge
12、pressure is equal to ambientatmospheric (barometric) pressure.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 March 15, 2011. Published April 2011. DOI: 10.1520
13、/D767511.2For 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 standards Document Summary page onthe ASTM website.3Available from SAE International (SAE), 400 Commonw
14、ealth Dr., Warrendale,PA 15096-0001, http:/www.sae.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.8 pressurized samplingcollection of a sample in acanister with a (final) canister pressure above atmosphericpressure3.1.9 Shew
15、art Control Chartstatistical tool for monitoringand improving quality, originated by Walter Shewart in 1924for the manufacturing environment and later extended toquality improvement in all areas of an organization.3.1.10 static calibrationcalibration of an analytical sys-tem using standards in a mat
16、rix, state or manner different thanthe samples to be analyzed.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 Analyzerutilizes the
17、 flameionization method of detection. The sensor is a burner in whicha regulated 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 ion
18、iza-tion that produces electrons 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 hyd
19、rocar-bons in the original sample, 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 controllermaintain
20、s the analyzer interior at a constant temperature. Atemperature of 50C 6 1 is appropriate. This feature mini-mizes temperature-dependent variations in electronic currentmeasuring circuitry and adsorption/desorption equilibrium ofbackground hydrocarbons within the internal flow system.4.4 To minimize
21、 system response time, an internal 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/v and thehydrocarbon was met
22、hane (CH4) there would be 1 mole ofmethane/mole of hydrogen. However, if the THC result is 1ppm v/v and the hydrocarbon was propane (C3H8), therewould be 0.33 mole of propane/mole of hydrogen.5. Significance and Use5.1 Low operating temperature fuel cells such as protonexchange membrane fuel cells (
23、PEFCs) require high purityhydrogen for maximum material performance and lifetime.Analysis to 0.1 part per million (ppm) concentration of totalhydrocarbons (measured as methane) in hydrogen is necessaryfor assuring a feed gas of sufficient purity to satisfy fuel cellsystem needs as defined in SAE TIR
24、 J2719 or as specified inregulatory codes.5.2 Although not intended for application to gases otherthan hydrogen, techniques within this test method can beapplied to other non-hydrocarbon gas samples requiring totalhydrocarbon content determination.6. Apparatus6.1 InstrumentAny instrument of standard
25、 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 manifold,burner jet and th
26、e collector. Streams of sample, fuel and airdelivered by the analyzer flow system are routed throughinternal passages in the manifold and into the interior of theburner. Here the sample and fuel pass through the burner jetand into the flame; the air stream flows around the periphery ofthe flame. (Se
27、e Fig. 1.)6.1.2 The burner jet and the collector function as electrodes.The jet is connected to the positive terminal of the 90 VDCpolarizing voltage. The collector is connected to the signalamplifier. The two polarized electrodes establish an electro-static field in the vicinity of the flame. The f
28、ield causes thecharged particles formed during combustion to migrate. Elec-trons go to the burner jet; positive ions go to the collector. Thusa small ionization current flows between the two electrodes.Magnitude of the current depends on the concentration ofcarbon atoms in the sample. The burner cur
29、rent serves as theinput signal 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 is measured by appro
30、priatemeans 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 RecorderA 0 to 1 mV range recording potentiom-eter or equivalent can be used.6.3.2 Data StorageMost instruments come equippe
31、d 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 MaterialsNOTE 1The use of oxygen scrubbers, water dryers, and hydrocarbonscrubbers are used in all gases supplied to the total carbon analysis system.Follow suppli
32、er instructions in the use of such gas purifiers and replace asnecessary.NOTE 2Compressed gas standards should only be handled in wellventilated locations away from sparks and flames. Improper handling ofcompressed gas cylinders containing air, nitrogen, hydrogen, or heliumcan result in explosion. R
33、apid release of nitrogen or helium can result inasphyxiation. Compressed air supports combustion. The hydrogen deliv-ery system must be leak free or a flammable situation could occur.7.1 Ultra-High Purity (UHP) Hydrogen, 99.999% mini-mum purity, 0.1 ppmv total hydrocarbon content.7.2 Ultra Zero Grad
34、e Air, less than 0.1 ppmv total hydro-carbon content.7.3 Reference StandardsThe calibration standards used inthis test method are NIST traceable standard mixtures ofMethane in Hydrogen. Methane concentrations used in this testmethod are listed below:D7675 112ZERO SPANCertified UHP Hydrogen-99.999% 1
35、06 2ppm Methane Balance Hydrogen7.4 Other multi-component gases as needed.8. Preparation of Apparatus8.1 1 Set up the instrumentation in accordance with themanufacturers instruction or as specified herein. If optional onthe specific instrument, use the maximum sensitivity settings toachieve the lowe
36、st possible detection limit.8.1.1 Start-up instrument according to manufactures speci-fications.8.1.2 Turn on the hydrogen fuel and air cylinders todetector. Insure flow settings are according to manufacturerspecifications. Typical flow settings for flame ionization detec-tors are 25cc/min for hydro
37、gen and 250cc/min for air.8.1.3 Ignite Detector. Flame ignition is indicated by a lowpopping sound. Allow sufficient time for the instrument andelectronics to stabilize.8.1.4 Proceed to calibration and sample analysis.9. Calibration and Standardization9.1 CalibrationThe instrument is calibrated dail
38、y “on-use” with zero gas (UHP Hydrogen, 99.999% min purity, 0.1ppm THC) and span gas certified standards. Most instrumentsmake it is possible to adjust the zero and span gain so that thedisplayed percent of full scale is the same as the ppm/vconcentration in the standards. This obviates the need for
39、mathematical calculation and expedites THC analysis.9.2 It is necessary to compare calculated results to thecertified values for a known standard before adopting thecalibration. The standard should contain all of the componentstypically observed in the samples. Results should agree within5% or bette
40、r of the certified value.9.3 Quality MonitoringIt is recommended to use a controlchart to record the response of the certified standard each timethe instrument is operated for the analysis of a sample. Whencalibration is complete, document the response for this instru-ment. After a representative se
41、t of data has been recorded, thedata can be plotted as a Shewart Control Chart to determineinstrument trends. The standard three sigma control limits canbe set as acceptance criteria for the performance of thisinstrument.9.3.1 Results are reported with respect to a lower detectablelimit of the analy
42、sis being performed with the instrument. Alower detectable limit of 0.1 ppm v/v has been established forthis method using the Student T-Test value for seven samples.Control charts aid in the maintaining of reproducible detectionlimits.10. Procedure10.1 Sampling10.1Sampling at the sample source shall
43、always be done in a manner that ensures safety and that arepresentative sample is being analyzed. Lack of precision andaccuracy in using this method can most often be attributed toimproper sampling procedures. (See Test Methods F307 andF1398.)10.2 Calibration:10.2.1 Open the zero and span gas cylind
44、er valves. Connectthe zero gas to the analyzer inlet and adjust the flow to themanufacturers specification.10.2.2 Adjust the zero control so that the display reads theconcentration of the zero standard.10.2.3 Connect the span gas to the analyzer inlet and adjustthe span control to the concentration
45、of the span standard.10.2.4 Repeat steps 10.2.2 and 10.2.3, alternating betweenzero and span, until the displays reaches the exact values of thestandards without further adjustment.FIG. 1 Typical FID Burner DiagramD7675 11310.2.5 An adjustment to either zero or span necessitates acheck of the opposi
46、te end of the scale. Close the zero and spangas cylinder valves.10.2.6 When calibration is complete, document it in thecontrol chart for this instrument along with the calibration gascylinder serial number, standard concentration, date, time, andinitials.10.3 Sample Analysis:10.3.1 Connect a regulat
47、or to the sample vessel, and connectthe sample from the regulator to the analyzer inlet viaappropriate sample line connections. Insure the sample pres-sure regulator does not exceed the maximum inlet pressurerecommended by the instrument manufacturer. Set the flow tothe manufacturer specification.10
48、.3.2 Wait for the reading to stabilize and record the ppm/vconcentration of the display.10.4 Shut-down:10.4.1 Close main valve from sample vessel and allowregulator to return to atmospheric pressure. Disconnect sampleconnection to analyzer.10.4.2 Close the fuel and air cylinder valves.10.4.3 Check t
49、hat the zero and span standard cylinder valveshave been closed.10.4.4 Shut down instrument according to manufacturer.11. Calculation11.1 A direct readout of the instrument display can be usedif the instrument is calibrated where the zero and span gain areset so that the displayed percent of full scale is the same as theppm/v concentration in the standards. This obviates the needfor mathematical calculation and expedites THC analysis.12. Report12.1 Report the concentration of the Total HydrocarbonContent as the ppm v/v concentration of the readout displ
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