METHOD FOR CONTINUOUS COOKING OF CELLULOSE-CONTAINING FIBRE MATERIAL

摘要

A method for cooking chips, involving steaming the chips, impregnating the chips with impregnating liquid in an impregnation vessel (2), which impregnating liquid comprises fresh cooking liquid and spent liquor, extracting spent liquor from the impregnation vessel (2), cooking the impregnated chips in cooking zones including an introductory co-current cooking zone and a concluding counter-current cooking zone, extracting spent liquor from the digester (3) at a position between the said co-current and counter-current cooking zones, transferring the said spent liquor from the digester to at least one position upstream of the digester, circulating the cooking liquid in a bottom circulation within the said counter-current cooking zone, heating the circulating cooking liquid by means of heat exchange, and supplying wash liquid to the bottom of the digester. According to the invention, at least some (18) of the digester extract (16), before being transferred to the said position upstream of the digester (3), undergoes heat exchange (32) with at least some (30) of the cooking liquid in the said bottom circulation.