1、Designation: D7800_D7800 14Standard Test Method forDetermination of Elemental Sulfur in Natural Gas1This standard is issued under the fixed designation D7800_D7800; the number immediately following the designation indicates the yearof original adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval.A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is primarily for the determination ofelemental sulfur in natural gas pipelines, but it may be appliedto oth
3、er gaseous fuel pipelines and applications provided theuser has validated its suitability for use.The detection range forelemental sulfur, reported as sulfur, is 0.0018 to 30 mg/L. Theresults may also be reported in units of mg/kg or ppm.1.2 The values stated in either SI units or inch-pound unitsar
4、e to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.3 This standard does not purport to address all
5、 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. Referenced Documents2.1 ASTM Standards:2D1072 Test Method for
6、 Total Sulfur in Fuel Gases byCombustion and Barium Chloride TitrationD1145 Test Method for Sampling Natural Gas (Withdrawn1986)3D1945 Test Method for Analysis of Natural Gas by GasChromatographyD3609 Practice for Calibration Techniques Using Perme-ation TubesD4084 Test Method for Analysis of Hydrog
7、en Sulfide inGaseous Fuels (Lead Acetate Reaction Rate Method)D4150 Terminology Relating to Gaseous FuelsD4468 Test Method for Total Sulfur in Gaseous Fuels byHydrogenolysis and Rateometric ColorimetryD4626 Practice for Calculation of Gas ChromatographicResponse FactorsD5287 Practice for Automatic S
8、ampling of Gaseous FuelsD5504 Test Method for Determination of Sulfur Compoundsin Natural Gas and Gaseous Fuels by Gas Chromatogra-phy and ChemiluminescenceD6228 Test Method for Determination of Sulfur Compoundsin Natural Gas and Gaseous Fuels by Gas Chromatogra-phy and Flame Photometric DetectionD7
9、165 Practice for Gas Chromatograph Based On-line/At-line Analysis for Sulfur Content of Gaseous FuelsD7166 Practice for Total Sulfur Analyzer Based On-line/At-line for Sulfur Content of Gaseous FuelsD7551 Test Method for Determination of Total VolatileSulfur in Gaseous Hydrocarbons and Liquefied Pet
10、roleumGases and Natural Gas by Ultraviolet FluorescenceD7607 Test Method for Analysis of Oxygen in GaseousFuels (Electrochemical Sensor Method)E840 Practice for Using Flame Photometric Detectors in GasChromatography2.2 ISO DocumentsISO 14532 Natural GasVocabulary3. Terminology3.1 Definitions:3.1.1 c
11、ompressed natural gas (CNG), nnatural gas that istypically pressurized to 24.8 MPa 3,600 psi. CNG is primar-ily used as a vehicular fuel. D4150-08 with modifications3.1.2 elemental sulfur, na pale yellow nonmetallic ele-ment occurring in nature and found as a particulate in dieselexhaust, natural ga
12、s, and other gaseous fuels. It exists inseveral free and combined allotropic forms.3.1.3 episulfide, na class of compound that contains asaturated heterocyclic ring consisting of two carbon atoms andone sulfur atom. It is the sulfur analogue of an epoxide. Theyare also known as thiiranes, olefin sul
13、fides, thioalkyleneoxides, and thiacyclopropanes.3.1.4 liquefied natural gas (LNG), nnatural gas that hasbeen liquefied, after processing, for storage or transportationpurposes. ISO 145321This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility
14、 of Subcommittee D03.05 on Determination ofSpecial Constituents of Gaseous Fuels.Current edition approved Nov. 1, 2014. Published November 2014. DOI:10.1520/D7800_D7800M-142For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For An
15、nual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. Unite
16、d States13.1.5 natural gas, na naturally occurring mixture of hy-drocarbon and nonhydrocarbon gases found in porous geologi-cal formations (reservoirs) beneath the earths surface, often inassociation with petroleum. The principal constituent of naturalgas is methane. D4150-083.1.6 natural gas pipeli
17、ne, npipeline in which natural gasis transported.3.1.7 pipeline, nall parts of those physical facilitiesthrough which gas moves in transportation, including pipe,valves, and other appurtenance attached to pipe, compressorunits, metering stations, regulator stations, delivery stations,holders, and fa
18、bricated assemblies.3.1.8 polysulfide, na class of chemical compounds con-taining chains of sulfur atoms. The two main classes ofpolysulfides are anions with the general formula Sn2. Theseanions are the conjugate bases of the hydrogen polysulfidesH2Sn. Organic polysulfides are also known; the main r
19、epre-sentatives of which have the formulae RSnR, where R = alkylor aryl.3.2 Acronyms:3.2.1 DMFdimethylformamide3.2.2 FPDflame photometric detector3.2.3 GCgas chromatograph3.2.4 PFPDpulsed flame photometric detector3.2.5 SCDsulfur chemiluminescence detector3.2.6 TPPtriphenylphosphine4. Summary of Tes
20、t Method4.1 A transportable elemental sulfur reactor is used toconvert elemental sulfur in the side stream of a flowing gasstream into an easily detectable species. This is accomplishedby sampling a representative portion of the natural gas streamand bubbling it through a chemical reactor containing
21、 triph-enylphosphine (TPP) in a solution of dimethylformamide(DMF). This solution selectively reacts with crystals of el-emental sulfur to produce the elemental sulfur adduct triph-enylphosphine sulfide (TPPS) (Eq 1 and Eq 2).5C6H5!3P1C6H5!3P1SSSSSSSS2C6H5!3PS1C6H5!3P1SSSSSSS2, etc. (1)C6H5!3P1C6H5!
22、3P1SS22C6H5!3PS (2)Liquid samples extracted from the transportable elementalsulfur reactor are injected into a gas chromatograph (GC)interfaced to a SCD, FPD, or a PFPD operating in thephosphorus mode. The concentration of TPPS is proportionalto the concentration of elemental sulfur found in the gas
23、.4.1.1 Natural gas, at a gauge pressure up to 6.8 MPa 1,000psig, is introduced into a transportable elemental sulfur reactorthrougha6mm14 in. stainless steel probe located in themiddle to top third of a pipeline. The reactor consists of anenclosure that is heated to approximately 71 C 160 F andconta
24、ins a series of three high pressure bubblers, which containthe reaction solution. A fourth bubbler is located outside theheated enclosure to act as a reaction solution vapor condenser.The gas flows through a coalescing filter to remove any liquiddroplets present to keep the meter from being contamin
25、ated.The gas is regulated to provide a constant pressure to ametering valve that is used to control the flow rate of gasthrough the system.The meter records the total volume that haspassed through the reactor during the test period.The apparatusis depicted in Fig. 1.4.1.2 Liquid samples extracted fr
26、om the transportable el-emental sulfur reactor are injected into a gas chromatographinterfaced to an SCD, FPD or PFPD configured to detectphosphorus. The TPPS and surrogate, TPPO4, are chromato-graphically resolved from other compounds in the sample,integrated, and concentration of elemental sulfur
27、in the originalnatural gas sample is calculated using the equations describedin subsection 4.1.5. Significance and Use5.1 Elemental sulfur impacts the quality of pipeline naturalgas and deposits on pipeline flanges, fittings and valves,thereby impacting their performance. Natural gas suppliers anddi
28、stributers require a standardized test method for measuringelemental sulfur. Some government regulators are also inter-ested in measuring elemental sulfur since it would provide ameans for assessing the contribution of elemental sulfur inpipelines to the SOx emission inventory from burning ofgaseous
29、 fuels. Use of this method in concert with sulfur gaslaboratory test methods such as Test Methods D4084, D4468,D5504, and D6228 or on-line methods such as D7165 orD7166 can provide users with a comprehensive sulfur com-pound profile for natural gas or other gaseous fuels. Otherapplications may inclu
30、de elemental sulfur in particulate depos-its such as diesel exhausts.6. Interferences6.1 Triphenylphosphine abstracts sulfur from polysulfideand episulfides, as well as elemental sulfur. Hence, polysulfideand episulfides that react with TPPS can interfere with thisanalysis. Simple organosulfur compo
31、unds such as thiols andthioethers are unreactive.6.2 Triphenylphosphine selenide (Ph3PSe) is an interferentthat may be encountered in some biogases.6.3 Triphenylphosphine oxide (Ph3PO) is an interferentresulting from slow oxidation of triphenylphosphine. (Eq 3).2PPh31O22OPPh3 (3)6.4 During the sampl
32、e collection, Hydrogen Sulfide (H2S)in the gas stream at elevated temperatures may react with TPP.Also, residual H2S in the medium may react with theTPPat theGC injector temperatures required to volatilize the sample.6.5 There may also be inadvertent oxidation of the residualH2S to elemental sulfur.
33、 To avoid extraneous oxidation, pre-cautions are taken with respect to preparation of the testsolutions, cleaning of the apparatus and handling of the reactedsolutions.7. Apparatus7.1 For each test site, the following equipment is needed:5“Reactions of Elemental Sulfur: I: The Uncatalyzed Reaction o
34、f Sulfur withTriarylphosphines,” Bartlett, P. D. and Garbis Meguerian. Journal of the AmericanChemical Society, vol. 78, No. 15, pp 3710. 1956.D7800_D7800 142FIG. 1 ReactorD7800_D7800 1437.1.1 Reactor cart with bubblers filled with TPP in asolution of DMF and purged with nitrogen. The bubblers areth
35、ree 500 mLpolytetrafluoroethylene-lined steel cylinders. Thethree cylinders are housed in an insulated cabinet fitted withheat trace tape to generate elevated temperatures, nominally 70to 90 C 160 to 195 F, required for the test.Afourth 500 mLsteel cylinder is connected downstream outside of the ins
36、ulatedcabinet. The interior of the reactor is rated for operation in aClass 1 Division 2 hazardous environment, however, theheating cable termination cap and the thermostat box may berated NEMA 4 (weather proof), so the reactor is typicallylocated at least 4.6 m 15 ft. away from the pipeline;7.1.2 C
37、oalescing filter and filter element,7.1.3 A6 mm in. sample probe of suitable length so thatthe probe tip can be positioned between the middle and aposition one-third from the top of the pipe,7.1.4 A4.6 m 15 ft. length of 6 mm in. stainless tubing(or longer depending on site),7.1.5 Thermocouple probe
38、,7.1.6 Thin wire thermocouple,7.1.7 Electronic thermometer or data logger,7.1.8 Stopwatch,7.1.9 Oxygen analyzer, and7.1.10 Electrical connection and 15 m nominally 50 ft.cord (or longer depending on site).7.2 The following laboratory equipment is needed:7.2.1 Chromatograph,7.2.1.1 Any gas chromatogr
39、aph of standard manufacture,with hardware necessary for interfacing to an SCD, PFPD, orFPD, and containing all features necessary for the intendedapplication(s) can be used. The detector should be configuredfor selective detection of phosphorus and placed in service inaccordance with the manufacture
40、rs instructions. This analysiscan be performed under a wide range of operating conditions.Typical, minimal performance criteria for chromatographicconditions are:(a) Operating conditions must be set such that TPPSseparates from the matrix and other sulfur species that may bepresent in a sample.(b) T
41、he injection system must transfer the TPPS to the GCcolumn without loss or absorption, without reaction to theTPPS and without excessive carryover between samples.The operating conditions presented in Fig. 3 and Fig. 4 havebeen successfully used to fulfill the above criteria. Fig. 2illustrates a typ
42、ical analysis of TPPS determined from a naturalgas sample.7.2.1.2 SCDPlace in service in accordance with the manu-facturers instructions, and configure the detector forphosphorus-selective detection or other selective sulfur modeto achieve sulfur speciation. Matrix interference is occasionallyobserv
43、ed when changing sample size. Matrix interference isalso indicated by recoveries less than 90% or greater than110% for samples spiked with calibration gas or samplesdiluted with air. When matrix interference is indicated, samplesmay be analyzed by dilution or application of other mitigationefforts p
44、rovided a spiked sample performed using the mitiga-tion procedure results in recoveries within 10% of theoreticalresults. Operational features specific to the interface configu-ration employed are described in the following. For furtherinformation on SCD operation and limitations, the user isreferre
45、d to Test Method D5504.FIG. 3 Example of General SCD Method ParametersMethod DescriptionProgram for Analysis of TPPSInjection Temperature = 275 CColumn Temperature = 155:1 at 25 275:9.2ValveOn=0Detector Temperature = OffGC ParametersTemperature SetupOven ParametersOven: OnOven Equilib Time: 0.00 min
46、Oven Max Temperature: 320 COven Cryo: OffOven Cryo Blast: OffOven Ambient: 20 COven Temperature ProgramInit LevelFinal Temp: 155.00 CFinal Time: 1.00 minLevel 1Rate: 25.00 C/minFinal Temp: 275.00 CFinal Time: 4.70 minZone TemperaturesInjector A Setpoint: 275 CDetector SetupDetector B: OnDet. B Negat
47、ive Polarity: OffSignal 1 ParametersSource: Det. BAttenuation: 0Range: 0Auto Zero: OffInlet AConstant Flow: OnConstant Flow Pressure: 12.60 kPaConstant Flow Temperature: 100.00 CColumn Length: 50.00 mColumn ID: 0.52 mmColumn Gas: HeVacuum Compensation: OffSplit Flow: 0.00 mL/minSplit Ratio: (0.00 :
48、1)Inlet A Pressure ProgramInit LevelPressure: 0.00 kPaFinal Time: 0.00 minPressure: 0.00 kPaFinal Time: 0.00 minInlet Temperature SetupInlet AZone Temperature: OnSetpoint Temperature: 275 COven Track: OffInlet A Temperature ProgramInit LevelFinal Temp: 0.00 CFinal Time: 0.00 minInit LevelFinal Temp:
49、 0.00 CFinal Time: 0.00 minInstrument SetupMinimum Stable Baseline Time: 15.0 minMaximum Test Time: 15.0 minD7800_D7800 1447.2.1.3 PFPD and FPDPlace into service in accordancewith manufacturers instructions, and configure the gas flowrates and optical filter for phosphorus-selective detection. Forfurther information on PFPD and FPD operation see PracticeE840.7.2.1.4 ColumnA variety of columns can be used inperforming the determination of elemental sulfur according tothis standard. Typically, a 60 m x 0.53 mm
