displacement liquid progresses in the digester moving upwardly from the bottom of the digester and moving downwardly from the top toward screen 25 and the displaced liquid leaves an interface will be formed between the advancing fronts of the displacing liquid which may be separately collected from the hot spent black liquor thus it can be seen that the displacement liquid and displaced liquid are collected and further processed separately with respect to one another blowing of the digester at the completion of the cook may be accomplished by the insertion of pressurized steam air or other fluid at a top inlet 31 the admission of fluid will continue until all of the pulp has been forced into the blow pit 13 alternatively a pump associated with valve 12a and blow pit 13 can be used for evacuating the digester the fibers in the blow pit will be delivered to a washer 29 which has an admission of wash water 30 the washing liquid having picked up some heat from the hot fibers is delivered to a low temperature tank 19 to be used as displacement liquid in the next successive batch cooking process the low temperature tank 19 may be a part of tank farm 16 usually a plurality of digesters will be used and operated in sequential batch cooking processes so that the wash liquid from one digester will be used for successive digesters as was the case in using the hot black liquor from the accumulators in the tank farm 16 for successive digesters such as illustrated at 27 thus it will be seen that i have provided an improved and simplified relatively rapidly operating process which is capable of reducing the loss.