Production of cellulose pulp

Claim 1

IN THE PRODUCTION OF CELLULOSE PULP FROM FIBROUS PLANT MATERIAL, THE PROCESS WHICH CONSISTS OF THE STEPS OF INTRODUCING PLANT MATERIAL IN SUBDIVIDED CONDITION INTO A PRESSURE VESSEL; DISPLACING AIR IN SAID PRESSURE VESSEL WITH STEAM; SUBJECTING SAID PLANT MATERIAL WITHIN SAID PRESSURE VESSEL TO A PRE-TREATING OPERATION WHICH COMPRISES INTRODUCING STEAM UNDER PRESSURE TO ESTABLISH WITHIN THE CAPILLARY INTERSTICES OF THE PLANT MATERIAL A MIXTURE OF AIR AND STEAM UNTIL A PRESSURE OF FROM ABOUT FIVE TO FIFTY POUNDS PER SQUARE INCH GAGE PRESSURE IS REACHED, THEN DISCONTINUING THE INTRODUCTION OF STEAM, AND WHILE EXCLUDING ADDITIONAL AIR FROM SAID PRESSURE VESSEL FORTHWITH RAPIDLY WITHDRAWING SAID MIXTURE OF AIR AND STEAM FROM SAID PRESSURE VESSEL AND FROM THE INSTERSTICES OF SAID PLANT MATERIAL UNTIL A PRESSURE IS REACHED WITHIN THE RANGE OF FROM ATMOSPHERIC PRESSURE TO A GAGE PRESSURE HALF THAT WHICH EXISTED WHEN THE INTRODUCTION OF STEAM WAS DISCONTINUED; THEREAFTER IMMERSING SAID PRE-TREATED PLANT MATERIAL IN COOKING LIQUOR WHILE CONTINUING TO EXCLUDE AIR FROM SAID PLANT MATERIAL; AND THEN COOKING SAID PRE-TREATED PLANT MATERIAL.