Process and configuration for providing external upflow/internal downflow in a continuous digester

摘要

A continuous digester configuration and process for continuously cooking and digesting cellulosic material and producing cellulosic pulp is disclosed. The digester configuration comprises a plurality of jump-stage recirculations located along the length of a continuous digester vessel, wherein each of the jump-stage recirculations moves extracted liquor from one elevation of the digester vessel and re-introduces the liquor at a higher elevation in the vessel to maintain an internal liquor downflow substantially throughout the entire digester vessel. The process for continuously cooking and digesting cellulosic material comprises maintaining an internal concurrent liquor downflow substantially throughout the continuous digester vessel, wherein the internal liquor downflow does not exceed 400 gallons per ton of b.d. wood feed.