is thereafter conveyed onwards to recovery below the level of the extraction screens 8a and 8b the chip column enters a countercurrent cooking zone the chips here encounter cooking liquid which has been extracted at the lower screen 17 heated in a lower heat exchanger shown at 17b and with the aid of a pump shown at 17a has been recirculated via a central pipe whose mouth 17c opens out level with the screen 17 according to a preferred embodiment of the present invention white liquor can be added in at least two positions on the one hand at the digester top 3 and on the other hand in the cooking circulation in the case where there are two cooking circulations it can be added to the one cooking circulation or to both cooking circulations it is of course also possible to add white liquor in the lower circulation 17 so that the alkali concentration is increased in the counter current zone and approximately the same temperature is expediently maintained in all the cooking zones so that the patented method itc u2122 is used wash liquor is added at the lower end 10 of the digester which wash liquor thus moves in a conventional manner in countercurrent and displaces hot liquor from the fiber material which permits a subsequent cold blow the pulp is then.