Study on preparation process of cryolite from anode carbon slag by catalytic decarburization
Aluminum anode carbon slag is a hazardous waste,but also a high-value of fluorine resources,the content of cryo-lite is about 70%,which has greater recycling value.In order to achieve the resource utilization and value-added utilization of anode carbon slag,the one-step roasting decarbonization process for recovering cryolite was explored.The effects of calci-nation temperature,holding time,and reagent ratio on the decarburization rate of anode carbon slag were investigated by adding reaction additives for catalytic calcination.The obtained optimal experimental conditions were calcination tempera-ture of 760℃,holding time of 2.5 h,addition of reaction additives of 5%(mass fraction),and a decarbonization rate of 97.75%under these conditions.Differential thermal analysis was conducted on the carbon slag with reaction additive of 5%and the combustion law of anode carbon slag catalyzed by adding reaction additives was obtained.As the temperature in-creasing,the decomposition of crystalline water,combustion of reaction additives,combustion of carbon in carbon slag,and volatilization of electrolytes occured successively.There was no obvious carbon residue in the obtained product,and the main component was cryolite.No new impurities were introduced during the catalytic roasting process.The iron and silicon impurities in the recovered cryolite were low in content and of high quality,and could be directly returned to the electrolytic cell for recycling.
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