1、Designation: D4468 85 (Reapproved 2015)Standard Test Method forTotal Sulfur in Gaseous Fuels by Hydrogenolysis andRateometric Colorimetry1This standard is issued under the fixed designation D4468; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、 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 sulfurgaseous fuels in the range from 0.001 to
3、20 parts per million byvolume (ppm/v).1.2 This test method may be extended to higher concentra-tion by dilution.1.3 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.4 This standard may involve hazardous materials,operations, an
4、d equipment. This standard does not purport toaddress all of the safety concerns associated with its use. It isthe responsibility of the user of this standard to establishappropriate safety and health practices and determine theapplicability of regulatory limitations prior to use. Specificprecaution
5、ary statements are given in 6.7, 6.8, and 7.3.2. Referenced Documents2.1 ASTM Standards:2D1193 Specification for Reagent WaterD1914 Practice for Conversion Units and Factors Relating toSampling and Analysis of AtmospheresD4045 Test Method for Sulfur in Petroleum Products byHydrogenolysis and Rateome
6、tric Colorimetry3. Summary of Test Method3.1 The sample is introduced at a constant rate into aflowing hydrogen stream in a hydrogenolysis apparatus. Thesample and hydrogen are pyrolyzed at a temperature of 1000Cor above, to convert sulfur compounds to hydrogen sulfide(H2S). Readout is by the rateom
7、etric detection of the colori-metric reaction of H2S with lead acetate. Units used are ppm/v,which is equivalent to micromoles/mole.4. Significance and Use4.1 This test method can be used to determine specification,or regulatory compliance to requirements, for total sulfur ingaseous fuels. In gas pr
8、ocessing plants, sulfur can be acontaminant and must be removed before gas is introduced intogas pipelines. In petrochemical plants, sulfur is a poison formany catalysts and must be reduced to acceptable levels,usually in the range from 0.01 to 1 ppm/v. This test methodmay also be used as a quality-
9、control tool for sulfur determi-nation in finished products, such as propane, butane, ethane,and ethylene.5. Apparatus5.1 Pyrolysis FurnaceA furnace that can provide anadjustable temperature of 900 to 1300C in a quartz or ceramictube of 5 mm or larger tube (ID) is required for pyrolysis of thesample
10、. (See Fig. 1.) The flow system is to be a fluorocarbonor other material inert to H2S and other sulfur compounds. (SeeFig. 1.)5.2 Rateometric H2S ReadoutHydrogenolysis productscontain H2S in proportion to sulfur in the sample. The H2Sconcentration is determined by measuring rate of change ofreflecta
11、nce of a tape impregnated with lead acetate caused bydarkening when lead sulfide is formed. Rateometricelectronics, adapted to provide first derivative output, allowssufficient sensitivity to measure to 0.001 ppm/v. (See Fig. 2.)5.3 RecorderA suitable chart recorder may be used for apermanent record
12、 of analysis.6. Reagents and Materials6.1 Purity of ChemicalsReagent grade unless specifiedotherwise.6.2 Purity of WaterUnless otherwise indicated, referenceto water shall be understood to mean Type II, reagent gradewater, conforming to Specification D1193.6.3 Sensing TapeLead acetate impregnated an
13、alyticalquality filter paper shall be used.1This 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 Nov. 1, 2015. Published December 2015.
14、 Originallyapproved in 1985. Last previous edition approved in 2011 as D446885 (2011).DOI: 10.1520/D4468-85R15.2For 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 s
15、tandards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States16.4 Acetic Acid (5 %)Mix 1 part by volume reagent gradeglacial acetic acid with 19 parts water to prepare 5 % aceticacid solution.6.5 Ga
16、stight SyringeA gastight 0.1- and 0.5-mL syringefor preparing calibration standard. Volumetric measurementaccuracy of the syringe shall be 1 % or better.6.6 Piston CylinderUse a 10-L acrylic cylinder with a freemoving piston and silicone rubber “O” ring lubricated with afree-flowing silicone lubrica
17、nt. This cylinder is used to prepareppm/v calibration samples volumetrically.6.7 Carbonyl Sulfide (COS)A lecture bottle of COS, 99 %purity, with a needle valve connected to the lecture bottleoutlet. Connect 2 ft of tygon tubing to allow insertion of ahypodermic syringe to withdraw pure COS while tub
18、ing ispurged from the lecture bottle. Other sulfur compounds can beused with adequate odor control. If the sulfur compound hastwo sulfur atoms per molecule, reduce the volume by one half.(Warning Work with COS should be done in a well-ventilated area, or under a fume hood.)6.8 Hydrogen GasUse sulfur
19、-free hydrogen of laboratorygrade. (WarningHydrogen has wide explosive limits whenmixed with air. See 1.4 regarding precautions.)6.9 Carrier Gas for Calibration StandardsUse sulfur-freelaboratory grade bottled gas of the same type or similar densityas the gas to be analyzed or calibrate the flowmete
20、r to establishcorrect flow setting for an available carrier gas. Test, as in 7.5,adding the carrier gas flow to the hydrogen flow.6.10 Purge GasSulfur-free purge gas, nitrogen, CO2,orother inert gas. Commercial grade cylinder gas is satisfactory.7. Preparation of Apparatus7.1 Turn on the furnace and
21、 allow temperature to stabilize at1000C. If thiophenic sulfur could be present, use 1300Ctemperature setting.NOTE 1Reduced operating temperature extends furnace life. Thio-phenic compound conversion increases from about 60 % at 1000C to100 % at 1300C.7.2 Connect all flow tubing between components an
22、d fillhumidifier inside the cabinet to 30 mL with a 5 % by volumeacetic acid solution. Purge all flow systems with inert gas thenclose valve. Check all connections for leaks with soap solutionand repair any leaks. Connect hydrogen and set flow at 200mL/min and allow temperature to stabilize. Sample
23、flow mustbe13 or less of the H2flow. Total flow can be up to 500mL/min, except when the sample has thiophenic compoundsthat require 200 mL/min of H2flow for conversion. Make finaltemperature adjustment to 1000 6 15C or a minimum 1300Cif the sample contains thiophenic sulfur compounds.7.3 Install sen
24、sing tape and turn H2S readout analyzer on.Use adequate safety precautions in handling lead acetate tape.7.4 Adjust the zero of the analyzer indicator meter (andrecorder if used) to desired position with no flow. This shouldbe performed with span at maximum.7.5 Test hydrogen purity by turning on hyd
25、rogen flow andnoting any change in zero position after 5 min. If the readingis upscale from the zero set point by greater than 4 %, then thehydrogen source should be suspect as not being sulfur free andshould be changed.FIG. 1 Hydrogenolysis Flow DiagramD4468 85 (2015)27.6 If the change in the recor
26、der zero is less than 4 %, thenreset the recorder zero to the desired position while thehydrogen is flowing. This should be performed with the span atmaximum.8. Standardization8.1 With hydrogen flow at 200 mL/min, advance tape to anunexposed area and note baseline.8.2 Prepare a reference standard as
27、 described in Section 9.Connect the reference sample to the pump and the pump to theanalyzer. When a stable reading is obtained, record this value(C in 11.1). Advance the tape and introduce reference samplegas flow with a sulfur concentration near that expected in theunknown (see 9.2).Adjust the sam
28、ple flow to 65 mL/min.Afterabout 4 min, adjust the recorder span such that the recordingindicates to desired response. The response is linear. A calibra-tion standard, such as 0.8 ppm/v, can be prepared and therecorder span adjusted to 80 % of full scale so that full scale is1 ppm/v and any lower va
29、lue can be read directly on a scaledivided into 100 parts.9. Calibration and Standardization9.1 Reference StandardReference standards are preparedby volumetric measurement at the time the reference materialis to be used. (See Fig. 3.) This minimizes deterioration of thesample. Normally this referenc
30、e standard will deteriorate lessthan 1 % in 15 min. Small volumes of pure sulfur compoundare measured using a gastight syringe. Dilution gas is measuredusing a 10-L graduated cylinder having a movable piston.When ppm/v samples are prepared for immediate use byvolumetric measurement, no correction fo
31、r temperature andpressure changes are needed in a laboratory environment.Temperature and pressure correction will be needed if conver-sion to weight units is desired.9.2 PreparationTo prepare 1-ppm/v sample, add 10 L(0.01 mL) of COS to make a 10-L sample carrier mixture.Inject COS through the septum
32、 on the 10-L acrylic cylinder asit is filled with carrier gas. Swirling of the carrier providesmixing. To calculate millilitres of sulfur compound required ina 10-L mixture, use the following equation:p 5 ppm/v 31022(1)FIG. 2 Photorateometry H2S ReadoutD4468 85 (2015)3where: p = millilitres of sulfu
33、r compound. (This applies togas-phase material only.)9.2.1 Prepare a reference standard of a concentrationslightly higher than may be anticipated in the sample. Purge the10-L cylinder with sulfur-free carrier gas. Connect the tygontubing to the COS lecture bottle and insert end into a beaker ofwater
34、. Open valve while observing bubbles to adjust tubingpurge flow rate. Insert gastight hypodermic needle into the wallof the tygon tubing. Raise and lower plunger slowly severaltimes to purge the syringe. Start filling the 10-L cylinder withcarrier gas and inject desired quantity of sulfur compoundth
35、rough the septum. Withdraw the syringe quickly after injec-tion to prevent residual gas in the needle tip from diffusing intothe flowing gas. Turn off the carrier gas when 10 L areobtained. The reference standard is now ready for use incalibrating the analyzer. For samples less than 1 ppm/v,secondar
36、y volumetric dilution may be used. As an example, toget a 0.2-ppm/v sample, exhaust the cylinder filled with 10 Lof 1-ppm/v gas to 2 L, then fill again to 10 L with diluent gas.10. Sample Measurement Procedure10.1 Connect the sample to the analyzer and adjust the flowrate to approximately 65 mL/min.
37、 This flow must be main-tained constant during testing.After the response is observed tobe stable, record the reading A (see 11.1). The referencestandard described in 9.2 must be prepared and run to establishthe analyzer span frequently enough to allow compensation forchanges in temperature and atmo
38、spheric pressure. Whensamples are within 25 % of the reference standard, repeatingthe entire calibration procedure twice a day is normallysufficient for this purpose.11. Calculation11.1 Calculate concentration of an unknown sample inppm/v as follows:X 5 A 2 B!D/C 2 B! (2)where:A = scale reading for
39、the unknown sample at ambienttemperature and pressure,B = blank scale reading,C = scale reading obtained from the prepared referencestandard at ambient temperature and pressure,D = fraction of sulfur compound in reference standard inunits of ppm/v, andX = fraction of sulfur compound in the unknown s
40、ample inppm/v.FIG. 3 Flow System for Gas Sample and Calibration ReferenceD4468 85 (2015)411.2 Conversion from volume fraction to mass concentra-tion W of sulfur compound in milligrams per cubic metre at25C and 760 mm Hg (101.3 kPa) is obtained by multiplyingppm by molecular weight and dividing by 24
41、.450 as shown inPractice D1914. For carbonyl sulfide:W 5 2.46X (3)where:W = mass concentration, mg/m3;X = fraction of sulfur compound by volume in the un-known sample, ppm by volume; andM = molecular weight.Make appropriate correction for other temperatures andpressures.12. Precision12.1 The informa
42、tion in this section is derived from datacollected by ASTM Committees D03 and D22, using a similartype analyzer to measure H2S.12.1.1 RepeatabilityAt the 95 % confidence level, thedifference as a result of test error obtained between two resultsfrom the same sample at the same laboratory should beco
43、nsidered suspect if greater than as follows:RepeatabilityFull-Scale Range,ppm/vPiston Cylinder Reference(Manual) Deviation,(ppm/v)PPM GeneratorReference (Automatic)Deviation, ppm/v1.0 0.014 0.0170.1 0.002 0.00212.1.2 ReproducibilityAt the 95 % confidence level, thedifference caused by test error obt
44、ained between two resultsfrom the same sample from different laboratories should beconsidered suspect if greater than as follows:ReproducibilityFull-Scale Range,ppm/vPiston Cylinder Reference(Manual) Deviation,ppm/vPPM GeneratorReference (Automatic)Deviation, ppm/v1.0 0.050 0.1410.1 0.006 0.00812.1.
45、3 For sulfur compounds other than H2S, the repeatabil-ity and reproducibility are as follows : (See Test MethodD4045.)Full-Scale Reading,ppm/vRepeatability,ppm/vReproducibility,ppm/v1.0 0.16 0.260.1 0.051 0.08213. Keywords13.1 gaseous fuels; sulfurASTM International takes no position respecting the
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