ASTM_D_6558_-_22.pdf

Designation:D655822Standard Test Method forDetermination of TGA CO2Reactivity of Baked CarbonAnodes and Cathode Blocks1This standard is issued under the fixed designation D6558;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.Scope*1.1 This test method covers the thermogravimetric(TGA)determination of CO2reactivity 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 methodstandardizesthevariablesofsampleshape,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,health,and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards,Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade(TBT)Committee.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,nthat 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 plus thequantity of carbon that is collected from the carbon artifactafter cooling.3.1.2 final CO2reactivity,nthe mass loss of the carbonartifact during the final 30 min of exposure to CO2in thereaction chamber divided by the initial geometric(right cylin-drical)exposed surface area of the sample,expressed asmilligrams per centimetre squared per hour.3.1.3 initial CO2reactivity,nthe mass loss of the carbonartifact during the first 30 min of exposure to CO2in thereaction chamber divided by the initial geometric(right cylin-drical)exposed surface area of the sample,expressed asmilligrams per centimetre squared per hour.3.1.4 total CO2reactivity,nthe total mass loss of thecarbon artifact(including dusting)during the total time that thesample is exposed to CO2(60 min to 420 min)in the reactionchamber divided by the initial geometric(right cylindrical)exposed surface area of the sample,expressed as milligramsper centimetre squared per hour.4.Summary of Test Method4.1 Initial,final,and total CO2reactivity and dusting aredetermined by passing carbon dioxide gas at flow rates givinga standard velocity of reactant gas around cylindrically shapedcarbon artifacts under isothermal conditions for a specifiedlength of time.The reactivity is determined by continuouslymonitoring the sample mass loss.The dusting term can bedetermined by collecting and determining the mass of carbonparticles that fall off the sample during reaction or collectedfrom the sample after the heat treatment.5.Significance and Use5.1 The CO2reactivity rates are used to quantify thetendency of a carbon artifact to react with carbon dioxide.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 1,2022.Published July 2022.Originally approvedin 2000.Last previous edition approved in 2015 as D6558 00a(2015)1.DOI:10.1520/D6558-22.2For 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.*A Summary of Changes section appears at the end of this standardCopyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Sta