evaporation they can be closed for example with mantles in addition to the apparatus described herein above crushing apparatus developed in the mining industry for crushing minerals can also be used for performing the crushing step the method can also be based on utilizing a screw press according to a preferable embodiment at least a portion of the liquor flowing together with the chips or corresponding raw material is replaced by fresh cooking liquor after the crushing treatment this can be accomplished by separating 10 80 preferably about 30 60 of the cooking liquor after the crusher in a standard output or for example in a screw press whereafter fresh cooking liquor is fed into the spiral conveyor 14 15 28 29 the fresh liquor fed into the spiral conveyor can be heated to the pulping temperature 70 110 u00b0 c preferably about 90 100 u00b0 c which causes pulping to take place partly already in the spiral conveyor in fact the pulper may comprise the said spiral conveyor as is described herein below in this case it is fitted with a heating jacket to retain the temperature the jacket can be heated for example with oil the separated cooking liquor is washed and regenerated when necessary and returned for example into the wash tank of chips to be used.