Integrated lignocellulose digestion and recovery process

Claim 1

THE IMPROVED PROCESS OF RECOVERING CHEMICALS ANDF HEAT FROM RESIDUAL LIQUOR PRODUCING IN A THREE-STAGE ACIDNEUTRAL-ALKALINE PROCESS FOR PRODUCING PULP FROM FIBROUS MATERIAL CONTAINING CELLULOSE WHICH COMPRISES COOKING FIBROUS MATERIAL WITH A WEAK ACID SOLUTION CONTAINING AN AGENT OF THE GROUP CONSISTING OF SULFITE, BISULFITE, AND BISULFITE WITH AN EXCESS OF SO2 OF AN LAKALI METAL, PRODUCING PARTLY DIGESTED PULP, CONVERTING SAID ACID COOKING BY INJECTING AN ALKALINE LIQUOR IN THE DIGESTOR AT THE END OF THE ACID COOKING STAGE TO AN ALKALI COOKING LIQUOR HAVING A PH RANGE OF ABOUT 7 TO ABOUT 10.5 WITHOUT SEPARATING SAID PARTLY COOKED PULP AND WITHOUT DISCONTINUING THE COOKING, SAID INJECTED ALKALINE LIQUOR CONSISTING ESSENTIALLY OF A CARBONATE AND MOTHER LIQUOR OF AN ALKALI METAL PRODUCED IN THE CONVERSION OF THE SMELT SOLUTION PRODUCED HEREINAFTER, COOKING WITH SAID WEAK ALKALINE COOKING LIQUOR CONSISTING ESSENTIALLY OF A CARBONATE OF AN ALKALI METAL TO PRODUCE COMPLETELY DIGESTED PULP AND RESIDUAL LIQUOR WHILE EVOLVING STRONG CO2 DURING SAID ALKALINE COOKING, RECOVERING SAID EVOLVED CO2, SAID RECOVERED CO2 CONSTITUTING MAINLY THE AMOUNT REQUIRED IN THE SUBSEQUENT TREATMENT OF A SMELT SOLUTION, SEPARATING SAID PULP FROM SAID RESIDUAL LIQUOR, EVAPORATING AND BURNING SAID RESIDUAL LIQUOR TO PRODUCE STEAM AND A SMELT CONSISTING ESSENTIALLY OF A CARBONATE OF AN ALKALI METAL AND A SULFIDE OF AN ALKALI METAL, DISSOLVING