Patent ID: 6325888
Filing Date: 2001-12-04
Classification: D21C

Abstract:
A method of producing chemical cellulose pulp from sawdust utilizing a static down-flow retention vessel, comprising the steps of continuously:(a) adding steam and cooking liquor to a flow of sawdust to produce a heated slurry of sawdust and cooking liquor at a consistency of between about 15-35%, and a cooking temperature of between about 250-350 degrees F.;(b) passing the heated slurry from step (a) at superatmospheric pressure downwardly in the static down-flow retention vessel, and retaining the slurry in the retention vessel at cooking temperature between about 0.5-6 hours, and then discharging it at a consistency of between about 5-20% from the retention vessel; and(c) at superatmospheric pressure, without significant reduction in pressure from the retention vessel, cooling the slurry discharged from the retention vessel by diffusing cooling liquid therethrough so that the temperature of the slurry drops below cooking temperature, and cooking thereof is terminated.