INTEGRATION OF HEMICELLULOSES RECOVERY INTO COLD CAUSTIC EXTRACTION PROCESS FOR THE PRODUCTION OF DISSOLVING PULP

摘要

In this study,the hemicelluloses recovery process has been suggested to integrate into the upgrading of paper-grade kraft pulp into dissolving pulp by the cold caustic extraction(CCE).Under the conditions of 15％NaOH,10％pulp consistency,30oC and 1h,a paper-grade softwood kraft pulp was purified to a high-grade dissolving pulp with 97.57％α-cellulose content,1.67％pentosane content,and a more uniformed structure.The resulting extraction filtrate was sequentially extracted with ethanol to precipitate and recover hemicelluloses with predominate sugar composition of xylose.The filtrate after removing ethanol was a relatively clear NaOH solution with around 15％alkalinity that can be reused into the CCE process.The produced pulp using recycled alkaline solution presented almost the same properties as the fresh alkaline solution yielded,which indicate the feasibility of integrating of hemicelluloses production into the cold caustic extraction process for the dissolving pulp production.