Kraft pulp and paper recovery process

Abstract

Abstract WASTE EFFLUENTS FROM A KRAFT PLANT ARE REDUCED BY RECLAIMING COLORED LIQUORS WHITE WATER AND WEAK LIQUOR SEWER WATERS BY SEPARATE PROCEDURES THAT ARE PREFERABLY INTEGRATED. EFFLUENT COLORED LIQUORS, SUCH AS EVAPORATOR CONDENSATE, BLOW HEAT CONDENSATE, AND PULP DECKER FILTRATE ARE TREATED IN A CLARIFIER WITH CALCIUM CARBONATE AS A FLOCCULATING AID TO SETTLE OUT COLLOIDAL MATERIAL AND THE CLARIFIER UNDERFLOW IS PASSED TO THE LIME AND FILTER CAKE FOR SUBSEQUENT BURNING IN THE LIME KILN. THE CLARIFIED LIQUOR IS RETURNED TO THE PROCESS FOR USE AS SCRUB WATERS IN A RECOVERY FURNACE GAS SCRUBBER AND IN THE PRIMARY AND SECONDARY LIME KILN GAS SCRUBBERS, AND THE UNDERFLOW FROM THE PRIMARY SCRUBBER IS USED AS A SOURCE OF CALCIUM CARBONATE IN THE CLARIFIER. THE WHITE WATER IS ISOLATED FROM THE PLANT SEWER SYSTEM AND ALSO TREATED IN A CLARIFIER WITH CALCIUM CARBONATE. IN THE CASE, THE UNDERFLOW FROM THE SECONDARY SCRUBBER SERVES AS A CALCIUM CARBONATE SOURCE. THE CLARIFIED WHITE WATER IS THEN FLITERED AND SUBSEQUENTLY PASSED THROUGH A CATION EXCHANGE UNIT SO THAT IT CAN BE THEN USED AS FRESH WATER IN THE KRAFT PLANT. WEAK LIQUOR FROM THE PLANT SEWER SYSTEM IS ALSO ISOLATED AND AFTER COLLECTION IN A POUND IS RETURNED AS WASH WATER TO AN INTERMEDIATE STAGE IN THE MULTISTAGE PULP WASHING UNIT. A PORTION OF THE EFFLUENT FROM THE CATION EXCHANGE UNIT IS HEATED IN A BLOW HEAT RECOVERY UNIT AND SUBSEQUENTLY USED AS FRESH WASH WATER IN THE LAST STAGE OF THE WASHING UNIT WHILE THE UNDERFLOW FROM THE RECOVERY FURNACE GAS SCRUBBER IS USED AS WASH WATER IN THE LIME MUD WASHER.

Inventors

• 👤 Joseph E Mailhos
• 👤 Gerald P Delaune

Bibliographic Details