Continuous digesting of cellulosic fibrous material at decreasing pressure with mechanical defibering therebetween

Claim 1

THE PROCESS OF PRODUCING PULP FROM CELLULOSIC FIBROUS MATERIAL COMPRISING FORCING THE FIBROUS MATERIAL INTO A FIRST CHAMBER, INTRODUCING INTO SAID FIRST CHAMBER PULPING CHEMICALS AND STEAM TO MAINTAIN THEREIN A FIRST PRESSURE SUBSTANTIALLY HIGHER THAN ATMOSPHERIC PRESSURE AND THE CORRESPONDING TEMPERATURE OF SATURATED STEAM, AGITATING THE MATERIAL IN SAID FIRST CHAMBER TO HEAT THE MATERIAL SUBSTANTIALLY TO SAID SATURATED STEAM TEMPERATURE, DISCHARGING THE MATERIAL DIRECTLY FROM SAID FIRST CHAMBER INTO A SECOND CHAMBER, MECHANICALLY DEFIBERING THE MATERIAL IN SAID SECOND CHAMBER AT SUBSTANTIALLY THE PRESSURE AND TEMPERATURE IN SAID FIRST CHAMBER, DISCHARGING THE MATERIAL DIRECTLY FROM SAID SECOND CHAMBER INTO A THIRD CHAMBER, MAINTAINING IN SAID THIRD CHAMBER A SECOND PRESSURE SUBSTANTAILLY HIGHER THAN ATMOSPHERIC PRESSURE BUT LOWER THAN SAID FIRST PRESSURE, SUBJECTING THE MATERIAL TO THE PRESSURE DROP FROM SAID FIRST PRESSURE TO SAID SECOND PRESSURE WHILE MOVING IT INTO SAID THIRD CHAMBER, AGITATING THE MATERIAL IN SAID THIRD CHAMBER AT SAID SECOND PRESSURE AND AT THE CORRESPONDING SATURATED STEAM TEMPERATURE, DISCHARGING THE MATERIAL FROM SAID THIRD CHAMBER DIRECTLY INTO A FOURTH CHAMBER, MECHANICALLY DEFIBERING THE MATERIAL IN SAID FOURTH CHAMBER DELIVERING IT INTO AN OUTLET CONDUIT WHILE SUBJECTING THE MATERIAL IN SAID FOURTH CHAMBER TO A PRESSURE DROP FROM SAID SECOND PRESSURE.