ASTM_D_6559_-_00a_2010.pdf

Designation:D655900a(Reapproved 2010)Standard Test Method forDetermination of Thermogravimetric(TGA)Air Reactivity ofBaked Carbon Anodes and Cathode Blocks1This standard is issued under the fixed designation D6559;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 thermogravimetric(TGA)determination of air reactivity and dusting of shaped carbonanodes and cathode blocks used in the aluminum reductionindustry.The apparatus selection covers a significant variety oftypes with various thermal conditions,sample size capability,materials of construction,and procedures for determining themass loss and subsequent rate of reaction.This test methodstandardizes the variables of sample dimensions,reactiontemperature,gas velocity over the exposed surfaces,andreaction time such that results obtained on different apparatusesare correlatable.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:2D6353 Guide for Sampling Plan and Core Sampling forPrebaked Anodes Used in Aluminum ProductionD6354 Guide for Sampling Plan and Core Sampling ofCarbon Cathode Blocks Used in Aluminum ProductionE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test Method3.Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 dusting,nthe quantity of carbon that falls off thecarbon artifact while in the reaction chamber and is collected inthe container at the bottom of the reaction chamber.3.1.2 final air reactivity,nthe mass loss of the carbonartifact during the final 30 min of exposure to air in the reactionchamber divided by the initial geometric(right cylindrical)exposed surface area of the sample,expressed as mg/cm2-h.3.1.3 initial air reactivity,nthe mass loss of the carbonartifact during the first 30 min of exposure to air in the reactionchamber divided by the initial geometric(right cylindrical)exposed surface area of the sample,expressed as mg/cm2-h.3.1.4 total air reactivity,nthe total mass loss of the carbonartifact(including dusting)during the total time that the sampleis exposed to air(180 min)in the reaction chamber divided bythe initial geometric(right cylindrical)exposed surface area ofthe sample,expressed as mg/cm2-h.4.Summary of Test Method4.1 Initial,final,and total air reactivity and dusting aredetermined by passing air at flow rates,giving a standardvelocity of reactant gas around cylindrically shaped carbonartifacts under nearly isothermal conditions for a specifiedlength of time.The reactivity is determined by continuouslymonitoring the sample mass loss.The dusting term is deter-mined by collecting and determining the mass of carbonparticles that fall off the sample during reaction.5.Significance and Use5.1 The air reactivity rates are used to quantify the tendencyof a carbon artifact to react with air.Carbon consumed by thisunwanted side reaction is unavailable for the primary reactionsof reducing alumina to the primary metal.Air reactivity dustingrate is used by some companies to quantify the tendency of thecoke aggregate or binder coke of a carbon artifact to selectivelyreact with these gases.Preferential attack of the binder coke orcoke aggregate of a carbon artifact by these gases causes somecarbon to fall off or dust,making the carbon unavailable for theprimary reaction of reducing alumina and,more importantly,reducing the efficiency of the aluminum reduction cell.1This test method is under the jurisdiction of ASTM Committee D02 onPetroleum Products,Liquid Fuels,and Lubricantsand is the direct responsibility ofSubcommittee D02.05 on Properties of Fuels,Petroleum Coke and Carbon Material.Current edition approved May 1,2010.Published May 2010.Originallyapproved in 2000.Last previous edition approved in 2005 as D655900a(2005).DOI:10.1520/D6559-00AR10.2For 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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 5.2 Comparison of air reactivity and dusting rates is usefulin selecting raw materials for the manufacture of commercialanodes for specific smelting technologies in the aluminumreduction industry.5.3 Air reactivity rates are used fo