Recovery of chemicals in wood pulp preparation

Claim 1

IN RECOVERING CHEMICALS AND HEAT FROM SODA-BASE ACID-SULFITE WASTE LIQUOR, THE IMPROVEMENT WHICH COMPRISES EVAPORATING THE LIQUOR AND BURNING THE CONCENTRATE IN A FURNACE TO FORM A SMELT, ADDING TO THE SMELT STRIPPED AQUEOUS LIQUOR FROM THE PROCESS TO FORM A SLURRY OF SODIUM CARBONATE CRYSTALS IN A CONCENTRATED SOLUTION OF SODIUM SULFIDE, SEPARATING SODIUM CARBONATE CRYSTALS FROM THE SLURRY, CIRCULATING PART OF THE SODIUM CARBONATE CRYSTALS BACK TO THE WASTE LIQUOR TO FLUX THE CONTAINED CHEMICALS AND LOWER THE MELTING TEMPERATURE OF THE SMELT, DIRECTING THE OTHER PART OF THE SODIUM CARBONATE TO SODABASE ACID-SULFITE LIQUOR MAKE-UP, SUBJECTING THE CONCENTRATED SODIUM SULFIDE SOLUTION TO CARBONATION AND STEAM STRIPPING TO FORM HYDROGEN SULFIDE AND SAID STRIPPED AQUEOUS LIQUOR, OXIDIZING THE HYDROGEN SULFIDE TO SULFUR DIOXIDE, REACTING THE SULFUR DIOXIDE WITH THE SODIUM CARBONATE TO MAKE UP THE SODA-BASE ACID-SULFITE LIQUOR, SAID CARBONATION BEING CARRIED OUT AT A TEMPERATURE ABOVE 50*C. UNDER A PRESSURE OF AT ALEST 16 POUNDS PER SQUARE INCH ABSOLUTE AND SAID STRIPPING BEING CARRIED OUT UNDER A VACUUM OF FROM 5 TO 29 INCHES OF MERCURY.