Patent ID: 8758555

Claim:
A method of defibring lignocellulose-bearing raw material using a polysulphide-bearing cooking liquor in a pulp cooker comprising an absorption unit and a cooking unit consisting of the following steps, in order: mixing the cooking liquor before the cooking into the raw material which is to be defibred in the absorption unit, allowing the cooking liquor to absorb into the raw material at a temperature which is at maximum approximately 130° C., moving the cooking liquor and the treated raw material to the cooking unit, separating the unabsorbed cooking liquor used in the absorption from the treated raw material in the cooking unit, heating the separated cooking liquor to a temperature of approximately 140-170° C., feeding back all the generated hot cooking liquor to the treated raw material in the cooking unit from which it had been separated, the alkaline cooking liquor used in the cooking stage thus being that which was originally mixed with the raw material to be defibred in the absorption unit and forming at least 90% of the effective alkali dose of cooking liquor, and defibering the raw material with the hot cooking liquor in order to produce pulp which has a desired kappa number.