Process for regenerating black liquor

Claim 1

A PROCESS FOR REGENERATING AN ALKALINE SULFIDE PULPING LIQUOR FROM BLACK LIQUOR CONTAINING SODIUM HYDROXIDE, SODIUM SULFIDE, SODIUM SULFATE AND SODIUM CARBONATE WHICH INCLUDES OXIZING BLACK LIQUOR TO DESTROY ORGANIC MATTER THEREIN AND CONVERT THE SODIUM SALTS TO SODIUM SULFATE AND SODIUM CARBONATE BY HEATING UNDER PRESSURE SUFFICIENT TO MAINTAIN AT LEAST PART OF THE REATION MIXTURE IN THE LIQUID PHASE AT ELEVATED TEMPERATURE WITH SUFFICIENT OXYGEN TO CONVERT THE CARBON TO CARBON DIOXIDE AND ALL THE HYDROGEN TO STEAM; ADDING A RECYCLED, PREVIOUSLY KILNED MIXTURE OF BARIUM SULFIDE CONTAINING BARIUM CARBONATE AND CALCIUM OXIDE TO THE RESULTING OXIDIZED AQUEOUS LIQUOR TO PRECIPITATE BARIUM SULFATE, BARIUM CARBONATE, CALCIUM HYDROXIDE AND CALCIUM CARBONATE; SEPARATING SAID WET PRECIPITATED MIXTURE FROM ITS SUPERNATANT LIQUID; ADDING CARBON TO SAID PRECIPITATED MIXTURE; PASSING THE CARBON-CON TAINING MIXTURE TO A ROASTING ZONE TO CONVERT SUBCONTAINING MIXTURE IN SAID ROASTING ZONE TO CONVERT SUBSTANTIALLY QUANTITATIVELY THE BARIUM SULFATE TO BARIUM SULFIDE AND THE CALCIUM HYDROXIDE TO CALCIUM CARBONATE TO CALCIUM OXIDE; WITHDRAWING A MIXTURE OF BARIUM SULFIDE CONTAINING BARIUM CARBONATE AND CALCIUM OXIDE FROM SAID ROASTING ZONE; AND, RECYCLING SAID WITHDRAWN MIXTURE OF BARIUM SULFIDE CONTAINING BARIUM CARBONATE AND CALCIUM OXIDE TO SAID ADDITION STEP.