1、Designation: D 4084 07Standard Test Method forAnalysis of Hydrogen Sulfide in Gaseous Fuels (LeadAcetate Reaction Rate Method)1This standard is issued under the fixed designation D 4084; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revisi
2、on, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the determination of hydrogensulfide (H2S) in gaseous fuels. It is applicable
3、 to the measure-ment of H2S in natural gas, liquefied petroleum gas (LPG),substitute natural gas, landfill gas, sewage treatment off gasses,recycle gas, flare gasses, and mixtures of fuel gases. Thismethod can also be used to measure the hydrogen sulfideconcentration in carbon dioxide. Air does not
4、interfere. Theapplicable range is 0.1 to 16 parts per million by volume(ppm/v) (approximately 0.1 to 22 mg/m3) and may be extendedto 100 % H2S by manual or automatic volumetric dilution.1.2 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is th
5、eresponsibility 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. Referenced Documents2.1 ASTM Standards:2D 1193 Specification for Reagent WaterD 1914 Practice for Conversion Units and Factors
6、 Relatingto Sampling and Analysis of AtmospheresD 2420 Test Method for Hydrogen Sulfide in LiquefiedPetroleum (LP) Gases (Lead Acetate Method)D 3609 Practice for Calibration Techniques Using Perme-ation TubesD 7166 Practice for Total Sulfur Analyzer Based On-line/At-line for Sulfur Content of Gaseou
7、s FuelsE 2165 Practice for Establishing an Uncertainty Budget forthe Chemical Analysis of Metals, Ores, and RelatedMaterials3. Summary of Test Method3.1 Measurement of H2S is accomplished by ratiometricallycomparing a reading of an unknown sample with that of aknown standard using a differential col
8、orimetric detection.Pure H2S is used as a primary standard and mixed volumetri-cally with a sulfur free matrix gas that is ideally similar incomposition to the sample gas. A gaseous sample at constantflow is humidified and passed over lead-acetate-impregnatedpaper. H2S reacts with lead acetate to fo
9、rm a brown stain on thepaper. The rate of reaction and resulting rate of color change isproportional to the concentration of H2S in the sample. Theanalyzer is comprised of an optical system, a photon detectionsystem, a signal differentiation system of first order, and asignal output system. When the
10、re is no change in the color ofthe tape, and no resulting change in photodetector output, E,the first derivative, dE/dt, is zero. This results in an analyzerthat automatically zeroes when there is no H2S.4. Significance and Use4.1 This test method is useful in determining the concentra-tion of hydro
11、gen sulfide in gaseous samples and in verifyingcompliance with operational needs and/or environmental limi-tations for H2S content. The automated performance operationof this method allows unattended measurement of H2S con-centration. The user is referred to Practice D 7166 for unat-tended on-line u
12、se of instrumentation based upon the leadacetate reaction rate method.5. Apparatus5.1 Volumetric Measuring DevicesA graduated 10-L cyl-inder (see Fig. 1) having a movable piston for volumetricallymeasuring test gas. Gastight syringes of 0.1 and 0.5-mLvolume for volumetrically measuring 100 % H2S. Ga
13、s tightsyringes of other volumes can be used. These graduateddevices are not needed when the permeation tube method ofdynamic mixing is used to prepare the reference sample sincethis method will generate a reference mixture.5.2 Sample PumpA pump capable of providing more than8 mL/s (approximately 1
14、ft3/h) or less than 1 mL/s at 70 kPa(approximately 10.15 psig). Gas-wetted parts are ideally con-structed from either aluminum or polytetrafluorethylene1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determin
15、ation ofSpecial Constituents of Gaseous Fuels.Current edition approved June 1, 2007. Published June 2007. Originallyapproved in 1981. Last previous edition approved in 2006 as D 4084 06.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceas
16、tm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(PTFE). Stainless steel may be used when higher safety thana
17、fforded by aluminum or PTFE is required.5.3 Colorimetric Rate of Reaction SensorSelect a deviceof sufficient sensitivity to measure a minimum rate of changeof color density corresponding to 0.1-ppm H2S by volume inthe sample gas. (See Fig. 2.)5.4 Recorder, having an adjustable span of 1 to 10-V full
18、scale with an input impedance of 1 MV or higher. A printer orother output means, such as a data logger or DistributedControl System (DCS) , can be used.6. Reagents and MaterialsNOTE 1Warning: Hydrogen Sulfide contained in lecture bottles,permeation tubes or compressed gas cylinders may be flammable
19、andharmful or fatal if ingested or inhaled. Lecture bottles, permeation tubesand compressed gas standards should only be handled in well ventilatedlocations away from sparks and flames. Improper handling of compressedgas cylinders containing air, nitrogen or hydrocarbons can result inexplosion. Rapi
20、d release of nitrogen or hydrocarbon gasses can result inasphyxiation. Compressed air supports combustion.6.1 Acetic Acid SolutionAdd 50 mL of glacial acid(CH3COOH) to distilled water or dionized water to make 1 Lof solution (5 %). Type II distilled water as specified inSpecification D 1193 is satis
21、factory for the dilution. Waterdionized to 1 megaohm-centimeter is also satisfactory for thedilution.6.2 Reference Gas:FIG. 1 Calibration Sample Preparation Cylinder withMovable PistonFIG. 2 Flow System for H2S Measurement Showing Calibration, LPG, and Gaseous Sample ConnectionsD40840726.2.1 Hydroge
22、n Sulfide Source99.5 % by volume purityor better.An alternative H2S source is an H2S mixture obtainedusing permeation tube procedures. Hydrogen sulfide generatedfrom a solid heated to generate H2S may be used instead of aH2S source if desired. H2S contained in permeation tubes orcompressed gas cylin
23、ders may be flammable and harmful orfatal if ingested or inhaled. Permeation tubes and compressedgas standards should only be handled in well ventilatedlocations away from sparks and flames. (WarningHydrogensulfide is an extremely toxic gas.)6.2.2 Dilution GasesChemically pure grade or purifiedgas.
24、Blend or obtain a sulfur-free gas of the same relativedensity as the sample gas to be analyzed. Blends of gases, ofsimilar composition to the sample gas, are prepared from puregases by mixing, using a 10-L cylinder with piston. Pipelinegas scrubbed through activated charcoal and sodiumhydroxide-asbe
25、stos absorbent is satisfactory.6.2.3 Gas MixturesAnother alternative H2S source is acertified H2S mixture obtained from a gas standard vendor.Such mixtures are in a sulfur free carrier gas that is of the sametype, or a close approximation, as the gas to be analyzed. Thesemixtures can be either a pri
26、mary standard, which is then dilutedto the desired H2S concentration using a 10-L cylinder with apiston, or a standard in a pressurized cylinder containing thedesired H2S concentration. Because of the potential for degra-dation, H2S mixtures obtained from a gas standard vendor mustbe properly stored
27、 and used only within the stated certificationperiod. In the event of a discrepancy, H2S mixtures preparedfrom a 99.5 % by volume or better purity H2S lecture bottle orobtained using permeation tube procedures must be used.6.2.3.1 Compressed Gas StandardsThe protocol for com-pressed gas standards co
28、ntained in the appendix can be used toensure uniformity in compressed gas standard manufacture andprovide for traceability to a NIST or NMi reference material.6.2.3.2 Compressed gas standard regulators must be appro-priate for the delivery of sulfur gases and attached fittings mustbe passivated or i
29、nert to sulfur gases.6.3 Lead Acetate Sensing PaperPrepare in accordancewith Test Method D 2420, using appropriate size strips anddrying in an H2S-free environment. Commercially availabletest paper has been found satisfactory. Used Lead AcetateSensing Paper should be disposed of in accordance with l
30、ocal,state, and/or federal environmental regulations.6.4 Permeation DevicesHydrogen Sulfide standards canbe prepared using a permeation tube gravimetrically calibratedand certified at a convenient operating temperature.At constanttemperature, calibration gases covering a wide range of con-centration
31、 can be generated by varying and accurately measur-ing the flow rate of diluent gas passing over the tubes. Thesecalibration gases are used to calibrate the analyzer.6.4.1 Permeation System Temperature ControlPermeation devices are maintained at the calibration tempera-ture within 0.1C.6.4.2 Permeat
32、ion System Flow ControlThe permeationflow system measures diluent gas flow over the permeationtubes within 62 percent.6.4.3 Permeation tubes are inspected and weighed to thenearest 0.01 mg on at least a monthly basis using a balancecalibrated against NIST traceable “S” class weights or theequivalent
33、. Analyte concentration is calculated by weight lossand dilution gas flow rate as per Practice D 3609. Thesedevices are discarded when the liquid contents are reduced toless than ten (10) percent of the initial volume or when thepermeation surface is unusually discolored or otherwise com-promised. U
34、sed permeation tubes should be disposed of inaccordance with local, state, and/or federal environmentalregulations.7. Sampling7.1 Because of the chemical activity and adsorptive proper-ties of H2S, it is highly desirable to connect the test apparatusdirectly to the sample source using minimum length
35、s ofstainless steel, hastalloy, aluminum or fluorocarbon samplelines. Do not use copper containing, that is, brass or copperflow system parts. In the event that direct sampling is notpractical, clean aluminum, stainless steel, or fluorocarbon linedsample containers may be used. Tedlar bags with iner
36、t fittingssuch as polypropylene or equivalent and silica lined samplecontainers can also be used for sample collection. Tedlar bagscontaining sample require protection from light and heat. Thecollection of samples that are either in two phases or that willform two phases before analysis can be perfo
37、rmed must beavoided. The presence of liquids causes H2S to partitionunequally between the liquid and gas phases. Such a partitionof H2S results in inaccurate measurement of H2S content.Samples must be analyzed with as little delay as possible andreported as “proximate analyses from cylinders” with l
38、ength ofresidence time noted. Because of the broad reactivity of H2S,an extended delay between obtaining the sample and analyzingthe sample can result in inaccurate results.NOTE 2Each new sample container to be used for a test specimen canbe filled with a sample and analyzed over a period of time an
39、d theresulting data examined to determine the rate of deterioration of thesample. Repeated filling with a representative sample will tend topassivate a container. Approximately 10 L (approximately13 ft3)ofsample, at atmospheric pressure, is convenient for analysis and willnormally not deteriorate ap
40、preciably within 1 h. Slow instrument responseto changes in H2S concentration indicates the need for a thorough cleaningof the flow system. (See Appendix X1 for a suggested cleaning proce-dure.) Errors caused by ambient temperature and pressure changes arecompensated for by comparison to a reference
41、 standard prepared at thetime of analysis. Preparation of the reference sample is described inSection 11.8. Instrument Preparation8.1 Fill a humidifier or humidifying bubbler to the full markwith acetic acid solution. The acetic acid minimizes someinterfering species. Set the range of the analyzer f
42、or the rangeexpected in the sample. Connect the pump and set theflowmeter for a nominal flow of 8 mL/s (approximately 1ft3/h). Note: analyte gas can also be delivered to the analyzerby use of a compressed gas cylinder or a permeation tubedevice.Alternative flow settings, such as a nominal 1 mL/s, ca
43、nbe used. Obtain a blank reading by flowing dilution gasthrough the analyzer. Record the reading of the blank sample asB in 12.1. Do not adjust the instrument zero until verificationis obtained, that the room air or the carrier gas does not containH2S. Verification is accomplished by analyzing a roo
44、m air orD4084073carrier gas sample after it has been passed through an activatedcharcoal filter absorbent.9. Calibration9.1 Immediately after preparing the calibration standard,obtain its response on the analyzer. Practice D 3609 is accept-able as an alternative method for preparation of a reference
45、standard. Certified compressed gas calibration standards ob-tained from a gas standard vendor can also be used to calibratethe analyzer. The analyzer response is recorded as C in 12.1.Atleast twenty (20) discrete response replicates should be ob-tained to adequately demonstrate the statistical repea
46、tability ofthe analyzer at two times the standard deviations about themean. If the analyzer repeatability response fall outside of thepublished repeatability specifications then appropriate correc-tive action must be taken and the repeatability response of theanalyzer must be redetermined.10. Sample
47、 Measurement Procedure10.1 Sampling and Preparation of SamplesAppropriatesampling procedures are critical for meaningful hydrogensulfide determinations and must be tailored to the particularsample source.10.1.1 SamplesSamples are delivered to the laboratory inTedlar bags with polypropylene fittings
48、or other inert fittings atatmospheric pressure, protected from heat and light. Samplesare normally analyzed within 24 h of sampling to ensureaccurate measurement of hydrogen sulfide in the sample. Theholding time can be extended to the limits of existing datawhen hydrogen sulfide gas retention in a
49、specific matrix isavailable.Alternatively, samples are delivered to the laboratoryin passivated/lined vessels demonstrated to not demonstratesignificant hydrogen sulfide losses in samples over 24 h. Aspart of a QA/QC program, passivated or lined vessels shouldperiodically be examined for continued hydrogen sulfide gasstability and acceptable sample carryover characteristics. Pas-sivated or lined vessels may allow for reliable sample analysisafter more than 24 h. In such cases, analysis is recommendedwithin a time frame supported by hydrogen sulfide retentiondata.10
