Process for the continuous digestion of cellulosic materials

Claim 1

A PROCESS FOR CONTINUOUSLY TREATING CELLULOSE MATERIALS AT SUPERATMOSPHERIC PRESSURE; WHICH COMPRISES INTRODUCING CELLULOSIC MATERIAL TO BE TREATED INTO THE UPPER PORTION OF A FIRST DIGESTER AND PASSING SAID MATERIAL AS A CONTINUOUS DOWNWARD FLOW THERETHROUGH, CIRCULATING CHEMICAL TREATING LIQUOR THROUGH SAID DIGESTER IN COUNTERCURRENT FLOW TO SAID DOWNWARDLY FLOWING MATERIAL WHERE BY SAID LIQUOR SUBSTANTIALLY IMPREGNATES SAID MATERIAL, FORTIFYING SAID CIRCULATING LIQUOR WITH FRESH CHEMICAL TREATING LIQUOR, WITHDRAWING SAID IMPREGNATED MATERIAL AND CHEMICAL TREATING LIQUOR FROM SAID DIGESTER AND PASSING SAID WITHDRAWN MATERIAL AND LIQUOR TO A SECOND DIGESTER FOR DELIGNIFICATION OF SAID IMPREGNATED MATERIAL DURING PASSAGE THERETHROUGH, HEATING SAID WITHDRAWN MATERIAL AND CHEMICAL TREATING LIQUOR DURING SAID PASSAGE TO SAID SECOND DIGESTER TO ABOUT THE DELIGNIFYING TEMPERATURE EMPLOYED FOR SAID DELIGNIFICATION, AND WITHDRAWING SUBSTANTIALLY DELIGNIFIED CELLULOSIC MATERIAL FROM SAID SECOND DIGESTER.