PROCESS FOR CONTINUOUS COOKING OF PULP

摘要

PROBLEM TO BE SOLVED: To increase productivity of an existing continuous pulp cooker by improving a process for cooking pulp. SOLUTION: This process is suitable for a continuous cooking of wood chips at elevated pressure and temperature in a vertical cooker (1) suitable for chemically dissolved pulp production. A fibrous material and a cooking liquor are introduced into the top of the cooker, the pulp is discharged from the bottom of the cooker (1) through a line (8) maintained at the same pressure level as that of a substantial pressure cleaning (7) of the pulp. The wholly used cooking liquor (black liquor) extracted from a system in an amount of >=50% is extracted from a cleaning filtrate of pressure cleaning. Simultaneously a small amount of the cleaning filtrate is recycled to the bottom of the cooker as a diluent. The pressure cleaning is controlled so as to maintain the cleaning filtrate at a high temperature. The extraction is controlled so that a net co-current flow is established at the bottom of the cooker. The speed of increasing pulp is reduced through the cooker so that a production can be increased in the cooker in an overloaded state in which extraction of cooking liquor from the cooker is substantially difficult.