ASTM_D_6721_-_01_2015.pdf

Designation:D672101(Reapproved 2015)Standard Test Method forDetermination of Chlorine in Coal by Oxidative HydrolysisMicrocoulometry1This standard is issued under the fixed designation D6721;the number immediately following the designation indicates the 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 totalchlorine in coal.1.2 The values stated in SI units are to be regarded asstandard.No other units of measurement are included in thisstandard.1.3 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 determine the applica-bility of regulatory limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D2013 Practice for Preparing Coal Samples for AnalysisD3173 Test Method for Moisture in the Analysis Sample ofCoal and CokeD3180 Practice for Calculating Coal and Coke Analysesfrom As-Determined to Different BasesD4621 Guide for Quality Management in an OrganizationThat Samples or Tests Coal and Coke(Withdrawn 2010)3D5142 Test Methods for Proximate Analysis of the AnalysisSample of Coal and Coke by Instrumental Procedures(Withdrawn 2010)3E29 Practice for Using Significant Digits in Test Data toDetermine Conformance with SpecificationsE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method2.2 Other StandardsISO 5725-6:1994 Accuracy of measurement methods andresults-Part 6:Use in practice of accuracy values43.Summary of Test Method3.1 A 5.00 to 40.00 mg sample of coal is combusted withtungsten accelerator in a humidified oxygen gas flow,at 900C.Halogens are oxidized and converted to hydrogenated halides,which are flushed into a titration cell where they accumulate.Chlorine is converted to hydrochloric acid.Once the chloride iscaptured in the electrolyte of the titration cell,it can bequantitatively determined by microcoulometery,where chlo-ride ions react with silver ions present in the electrolyte.Thesilver ion thus consumed is coulometrically replaced and thetotal electrical work needed to replace it is proportional to thechloride in the test sample.4.Significance and Use4.1 This test method permits measurements of the chlorinecontent of coals.5.Interferences5.1 Bromides and iodides,if present are calculated aschloride.However,fluorides are not detected by this testmethod.6.Apparatus6.1 Hydrolysis Furnace,which can maintain a minimumtemperature of 900C.6.2 Hydrolysis Tube,made of quartz and constructed suchthat when the sample is combusted in the presence of tungstenaccelerator and humidified oxygen,the byproducts of combus-tion are swept into a humidified hydrolysis zone.The inlet endshall allow for the introduction and advancement of the sampleboat into the heated zone.The inlet shall have a side arm for theintroduction of the humidified oxygen gas.The hydrolysis tubemust be of ample volume,and have a heated zone with quartzwool so that complete hydrolysis of the halogens is ensured.1This test method is under the jurisdiction of ASTM Committee D05 on Coaland Coke and is the direct responsibility of Subcommittee D05.29 on MajorElements in Ash and Trace Elements of Coal.Current edition approved Jan.1,2015.Published January 2015.Originallyapproved in 2001.Last previous edition approved in 2006 as D6721 01(2006).DOI:10.1520/D6721-01R15.2For 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.3The last approved version of this historical standard is referenced onwww.astm.org.4Available from International Organization for Standardization 1 Rue deVaremb,Case Postale 56,CH-1211,Geneva 20,SwitzerlandCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 6.3 Titration Cell,containing a reference electrode,a work-ing electrode,and a silver sensor electrode,a magnetic stirreras well as an inlet from the hydrolysis tube.6.4 Microcoulometer,capable of measuring the potential ofthe sensing-reference electrode pair,comparing this potentialwith a bias potential,and amplifying the difference to theworking electrode pair to generate current.The microcoulom-eter output voltage should be proportional to the generatingcurrent.6.5 Controller,with connections for the reference,working,and sensor electrodes,for setting operating parameters and fordata integration.6.6 Hydration Tube,containing water,positioned before thegas inlet on the side arm of the combustion tube,through whichoxygen gas bubbles to provide a hydrated gas flow.6.7 Dehydration Tube,positioned at the end o