1、Designation: D7551 10Standard Test Method forDetermination of Total Volatile Sulfur in GaseousHydrocarbons and Liquefied Petroleum Gases and NaturalGas by Ultraviolet Fluorescence1This standard is issued under the fixed designation D7551; the number immediately following the designation indicates th
2、e year oforiginal adoption 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 covers the determination of total
3、volatile sulfur in gaseous hydrocarbons, Liquefied PetroleumGases (LPG) and Liquefied Natural Gas (LNG). It is applicableto analysis of natural gaseous fuels, process intermediates, finalproduct hydrocarbons and generic gaseous fuels containingsulfur in the range of 1 to 200 mg/kg. Samples can also
4、betested at other total sulfur levels using either pre-concentrationmethods or sample dilution using a diluent gas. The method-ology for preconcentration and dilution techniques is notcovered in this test method. The precision statement does notapply if these techniques are used in conjunction with
5、this testmethod. The diluent gas, such as UHP nitrogen, zero nitrogenor zero air, shall not have a significant total sulfur concentra-tion.1.2 This test method may not detect sulfur compounds thatdo not volatilize under the conditions of the test.1.3 This test method covers the laboratory determinat
6、ionand the at-line/on-line determination of total volatile sulfur ingaseous fuels, LPG, and LNG.1.4 This test method is applicable for total volatile sulfurdetermination in gaseous hydrocarbons, LPG, and LNG con-taining less than 0.35 mole % halogen(s).1.5 The values stated in SI units are to be reg
7、arded asstandard. No other units of measurement are included in thisstandard1.6 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 determi
8、ne the applica-bility of regulatory limitations prior to use. See Sections 4.1,7.3, 7.4, 11.2, and Section 8.2. Referenced Documents2.1 ASTM Standards:2D1070 Test Methods for Relative Density of Gaseous FuelsD1072 Test Method for Total Sulfur in Fuel Gases byCombustion and Barium Chloride TitrationD
9、1265 Practice for Sampling Liquefied Petroleum (LP)Gases, Manual MethodD3588 Practice for Calculating Heat Value, CompressibilityFactor, and Relative Density of Gaseous FuelsD3609 Practice for Calibration Techniques Using Perme-ation TubesD4150 Terminology Relating to Gaseous FuelsD4177 Practice for
10、 Automatic Sampling of Petroleum andPetroleum ProductsD4784 Specification for LNG Density Calculation ModelsD5287 Practice for Automatic Sampling of Gaseous FuelsD5503 Practice for Natural Gas Sample-Handling and Con-ditioning Systems for Pipeline InstrumentationD5504 Test Method for Determination o
11、f Sulfur Com-pounds in Natural Gas and Gaseous Fuels by Gas Chro-matography and ChemiluminescenceD6228 Test Method for Determination of Sulfur Com-pounds in Natural Gas and Gaseous Fuels by Gas Chro-matography and Flame Photometric DetectionD6299 Practice for Applying Statistical Quality Assurancean
12、d Control Charting Techniques to Evaluate AnalyticalMeasurement System PerformanceD7166 Practice for Total SulfurAnalyzer Based On-line/At-line for Sulfur Content of Gaseous FuelsE617 Specification for Laboratory Weights and PrecisionMass StandardsE691 Practice for Conducting an Interlaboratory Stud
13、y toDetermine the Precision of a Test Method1This test method is under the jurisdiction ofASTM Committee D03 on GaseousFuels and is the direct responsibility of Subcommittee D03.05 on Determination ofSpecial Constituents of Gaseous Fuels.Current edition approved May 1, 2010. Published June 2010. DOI
14、: 10.1520/D755110.2For 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.1Copyright ASTM International, 100 Barr Har
15、bor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.F307 Practice for Sampling Pressurized Gas for Gas Analy-sis2.2 ASTM Manuals:3ASTM MNL 72.3 GPA Standards:4GPA 2166 Obtaining Natural Gas Samples for Analysis byGas ChromatographyGPA 2174 Obtaining Liquid Hydrocarbon Samples for
16、Analysis by Gas Chromatography3. Terminology3.1 Defintions:For definitions of at-line instrument and on-line instrumentsee Terminology D4150.3.2 Acronyms:3.2.1 LNGliquefied natural gas3.2.2 LPGliquefied petroleum gas3.2.3 NISTNational Institute of Standards and Technol-ogy3.2.4 NMiNederlands Meetins
17、tituut3.2.5 NTRMNIST traceable reference material3.2.6 QAquality assurance3.2.7 QCquality control3.2.8 SO2ground state sulfur dioxide3.2.9 SO2*excited state sulfur dioxide3.2.10 SOxsulfur oxides3.2.11 SRMstandard reference material3.2.12 UHPultra high purity3.2.13 UVultraviolet3.2.14 VSLVan Swinden
18、Laboratorium4. Summary of Test Method4.1 A gaseous sample is injected into the analyzer, either bya sample valve, direct injection at a constant flow rate, or bysyringe. A LPG or LNG sample is vaporized in an appropriateexpansion chamber and injected into the analyzer by a samplevalve or a syringe o
19、r a sample valve connected to an expansionchamber. The gaseous sample then enters into a high tempera-ture combustion tube where the sulfur-containing compoundsin the sample are oxidized to SO2. Water produced during thesample combustion is removed, as required, and the samplecombustion gases are th
20、en exposed to a source of continuous orpulsed UV light. The SO2absorbs the energy from the UV lightto form SO2*. Fluorescence emitted from SO2* as it returns toSO2, is detected by a photomultiplier tube. The resulting signalis a measure of the sulfur contained in the sample. WarningExposure to exces
21、sive quantities of UV light is injurious tohealth. The operator shall avoid exposing any part of theirperson, especially their eyes, not only to direct UV light butalso to secondary or scattered radiation that is present.4.2 The design and installation details for the on-line/at-lineprocess analyzer
22、 needs to conform to application-specificrequirements including, but not limited to, acceptable designpractices as described in Practice D7166, hazardous areaclassifications, safety practices, and regulatory requirements.Fig. 1 illustrates a general flow diagram applicable for anon-line/at-line proc
23、ess analyzer. Sample collection and condi-tioning, sample introduction and detection system are depicted.Modifications to meet site-specific and/or application specificrequirements may be required.5. Significance and Use5.1 The sulfur content of gaseous hydrocarbons, LPG, andLNG used for fuel purpos
24、es contributes to total SOx emissionsand can lead to corrosion in engine and exhaust systems. Someprocess catalysts used in petroleum and chemical refining canbe poisoned by trace amounts of sulfur-bearing materials in thefeed stocks. This test method can be used to determine the totalvolatile sulfu
25、r content in process feeds, to control the totalvolatile sulfur content in finished products and, as applicable,to meet regulatory requirements. Practice D1072 has previ-ously been used for the measurement of total sulfur in gaseousfuels.6. Apparatus6.1 FurnaceAn electric furnace held at a constant
26、tem-perature in accordance with the analyzer manufacturers rec-ommendations (nominally 1000 to 1125C) sufficient to oxi-dize the entire sample to carbon dioxide and water and oxidizethe sulfur in the sample to SO2.6.2 Combustion TubeA quartz tube constructed to allowthe direct injection of the sampl
27、e into the heated oxidation zoneof the furnace by syringe or sample valve using either oxygen3MNL7A Manual on Presentation of Data and Control Chart Analysis, SeventhEdition, ASTM International, West Conshohocken. 2002.4Available from Gas Processors Association (GPA), 6526 E. 60th St., Tulsa, OK7414
28、5, http:/.FIG. 1 General Flow DiagramOn-Line AnalyzerD7551 102or air for the oxidation of the sample. Other tube materialssuitable for use at the furnace operating conditions can be usedso long as performance is not degraded. The oxidation sectionshall be large enough to ensure complete conversion o
29、f thesample to carbon dioxide and water and oxidize the sulfur inthe sample to SO2.6.3 Flow ControlThe apparatus shall be equipped withflow controllers capable of maintaining a constant volumetricflow rate of the carrier gases necessary for performing the totalsulfur analysis.6.4 DrierThe oxidation
30、of the sample produces reactionproducts that include water vapor which, if in excess, must beremoved prior to measurement by the detector. This can beaccomplished with a membrane drying tube, or a permeationdryer that utilizes a selective capillary action for water re-moval.6.5 UV Fluorescence Detec
31、torA quantitative detector ca-pable of measuring light emitted from the fluorescence of SO2generated by continuous or pulsed UV light.NOTE 1For an on-line analyzer, detection of uncombusted hydrocar-bons in the UV Fluorescence Detector can be used to ensure completeconversion of the hydrocarbons to
32、carbon dioxide and water and tominimize the potential for coke formation in the analytical system.6.6 Sample Inlet SystemEither of the following two typesof sample inlet systems can be used.6.6.1 Sample Valve SystemThe system provides a gas-sampling valve, or an LPG or LNG gas or liquid samplingvalv
33、e with an expansion chamber, or both, with access to theinlet of the oxidation area. The system is swept by the carriergas at the manufacturers recommended flow rate.6.6.2 Sample InjectionThe sample inlet system for gas-eous samples shall be capable of allowing the quantitativedelivery of the materi
34、al to be analyzed into an inlet carrierstream which directs the sample into the oxidation zone at acontrolled and repeatable rate. For a laboratory analysis, asyringe drive mechanism that discharges the sample from thesyringe at a rate of approximately 1 mL/s is required. For atline and on-line anal
35、ysis a constant volumetric flow ratedelivery device is used.6.7 Strip Chart Recorder, equivalent electronic data logger,integrator or, recorder (optional).7. Reagents7.1 Purity of ReagentsReagent grade chemicals shall beused in tests. Unless otherwise indicated, it is intended that allreagents shall
36、 conform to the specifications of the Committeeon Analytical Reagents of the American Chemical Society,where such specifications are available. Other grades may beused, provided it is first ascertained that the reagent is ofsufficiently high purity to permit its use without lessening theaccuracy of
37、the determination.7.2 Inert GasArgon or helium only, high purity grade(that is, chromatography or zero grade), 99.998 % minimumpurity, moisture 5 mg/kg maximum, as required.7.3 OxygenHigh purity, that is, chromatography or zerograde, 99.75 % minimum purity, moisture 5 mg/kg maximum,dried over molecu
38、lar sieves, as required. WarningOxygenvigorously accelerates combustion.7.4 AirUse dry, sulfur free air, that is, chromatographygrade or zero grade, 40 Cdew point or lower, as required.Nitrogen/oxygen or helium/oxygen bottled gas blends contain-ing no more than 30 % oxygen can also be used, as requi
39、red.WarningNever use pure oxygen as a substitute for air onanalyzers designed to operate using air as a carrier gas.7.5 Calibration StandardsCertified liquid or gas phasecalibration standards from commercial sources or calibrationgases prepared using certified permeation tube devices arerequired (se
40、e Notes 2 and 3). Accurate volatile sulfur contain-ing standards are required for quantization of the volatile totalsulfur content. Permeation tubes and compressed gas standardsshould be stable, of high purity, and of the highest availableaccuracy. Use of standards consisting of a sulfur compoundand
41、 matrix similar to samples to be analyzed is recommended.NOTE 2Other sulfur sources and diluent materials can be used ifprecision and accuracy are not degraded. The use of solvent basedcalibration standards that are liquid at ambient temperatures and pressuresis not recommended.NOTE 3Calibration sta
42、ndards are typically re-mixed and re-certifiedon a regular basis depending upon frequency of use and age. LPGcalibration standards have a typical useful life of about 612 months.NOTE 4Enhanced oxygen containing combustion gasses, such as30 % Oxygen balance Helium, Nitrogen, and/or Argon, can be used
43、 ifprecision and accuracy are not degraded.NOTE 5Warning: Compressed gas cylinders as well as sulfur com-pounds contained in permeation tubes may be flammable and harmful orfatal if ingested or inhaled. Permeation tubes and compressed gasstandards should only be handled in well ventilated locations
44、away fromsparks and flames. Improper handling of compressed gas cylinderscontaining air, nitrogen, helium, or other gasses can result in unsafeconditions that can cause severe damage to equipment and significantharm, including death, to people. Rapid release of nitrogen or helium canresult in asphyx
45、iation. Compressed air supports combustion.7.5.1 Permeation DevicesStandards containing volatilesulfur compounds can be made from permeation tubes, one foreach selected sulfur species, gravimetrically calibrated andcertified at a convenient operating temperature. With constanttemperature, calibratio
46、n gases covering a wide range of con-centration can be generated by varying and accurately measur-ing the flow rate of diluent gas passing over the permeationtubes. These calibration gases can be used to calibrate theanalyzer system.7.5.1.1 Permeation System Temperature ControlPermeation devices are
47、 maintained at the calibration tempera-ture within 60.1 C.7.5.1.2 Permeation System Flow ControlThe permeationflow system measures diluent gas flow over the permeationtubes within an accuracy of 62%.7.5.1.3 Permeation tubes are inspected and weighed to thenearest 0.01 mg on at least a monthly basis
48、using a balancecalibrated against Specification E617 Class 1 weights orequivalent. Analyte concentration is calculated by weight lossand dilution gas flow rate as per Practice D3609. Permeationtubes are replaced when the liquid contents are reduced to lessthan 10 % of the initial mass or when the pe
49、rmeation surface isunusually discolored or otherwise compromised. Permeationtube disposal shall be in accordance with all applicableregulations.D7551 1037.5.2 Compressed Gas StandardsAs an alternative topermeation tubes, blended gaseous standards containing vola-tile sulfur-containing compounds in nitrogen, helium methaneor other base gas may be used. Care must be exercised whenusing compressed gas standards since they can introduce errorsin measurement due to lack of uniformity in their manufactureor instability
