Patent ID: 6939439

Claim:
A batch process for producing chemical pulp from lignocellulose-containing material by means of alkaline cooking, comprising the steps of: a) charging said lignocellulose-containing material to a digester; b) initially treating said lignocellulose-containing material with an impregnation liquor to produce an impregnated lignocellulose-containing material; c) treating said impregnated lignocellulose-containing material with hot liquor so as to produce a heated lignocellulose-containing material, displacing calcium-containing spent liquor from said digester during said treatment; removing said calcium containing spent liquor from said digester; and storing said calcium-containing spent liquor in a storage unit; d) allowing said lignocellulose-containing material to continue being treated while said calcium-containing spent liquor is stored in said storage unit; e) heating and cooking said heated lignocellulose-containing material at predetermined cooking temperatures and pressures so as to produce cooked lignocellulose-containing material and cooking liquor; and f) reintroducing said calcium-containing spent liquor in said storage unit back into said digester so as to displace said cooking liquor from said digester using at least a portion of said displaced calcium-containing spent liquor being reintroduced into said digester.