Chemical recovery in pulp manufacture

• US 3,258,391 A
• Filed: 04/01/1965
• Issued: 06/28/1966
• Est. Priority Date: 08/25/1961
• Status: Expired due to Term

• Current Assignee: Conrad F. Cornell, Donald A. Dahlstrom
• Original Assignee: Conrad F. Cornell, Donald A. Dahlstrom
• Inventors: Cornell, Conrad F., Dahlstrom, Donald A.
• Application Number:
  US04/446,480
• Time in Patent Office: 453 Days
• US Class Current: 162/30.11
• CPC Class Codes: C01D 1/20 Preparation by reacting oxides or hydroxides with alkali metal salts
• CPC Class Codes: C01D 1/22 with carbonates or bicarbonates
• CPC Class Codes: D21C 11/0064 Aspects concerning the production and the treatment of green and white liquors, e.g. causticizing green liquor
• CPC Class Codes: Y02P 40/40 Production or processing of lime, e.g. limestone regeneration of lime in pulp and sugar mills
• CPC Class Codes: Y10S 423/03 Papermaking liquor

Claims

1. AN ALKALINE PULPING PROCESS WHEREIN CHEMICALS ARE RECOVERED FROM SPENT DIGESTION LIQUORS FOR REUSE IN THE PROCESS COMPRISING, LIBERATING FIBERS FROM WOOD BY DISSOLVING THE LIGNIN BINDER IN A CAUSTIC DIGESTION LIQUOR, RECOVERING SPENT DIGESTION LIQUOR, SMELTING THE SPENT DIGESTION LIQUOR TO FORM A SODIUM BEARING SMELT, DISSOLVING THE SMELT TO FORM AN AQUEOUS GREEN LIQUOR SOLUTION, CAUSTICIZING SUCH GREEN LIQOUR SOLUTION WITH LIME TO FORM A CAUSTIC WHITE LIQUOR CONTAINING CALCIUM CARBONATE PRECIPITATE, SEPARATING AND RECOVERING THE CAUSTIC WHITE LIQUOR AND CALCIUM CARBONATE, SAID SEPARATION AND RECOVERY EFFECTED SOLELY BY MEANS OF VACUUM FILTRATION TO WITHDRAW CAUSTIC LIQUOR AS FILTRATE WHILE FORMING A CALCIUM CARBONATE CAKE, SUBJECTING SUCH CAKE TO A FILTRATION DISPLACEMENT WASH UTILIZING FROM .15 TO .25 GALLON OF WASH LIQUOR PER POUND OF DRY CAKE SOLIDS, MAINTAINING THE STRENGTH OF SUCH CAUSTIC LIQUOR WITHDRAWN AS FILTRATE AT ABOUT 7.5 POUNDS TOTAL TITRATABLE ALKALI PER CUBIC FOOT OF LIQUOR BY INTRODUCING ADDITIONAL WATER TO THE MATERIAL UNDERGOING TREATMENT AFTER SMELTING AND BEFORE CAUSTICIZING, SAID AMOUNT OF WATER BEING AT LEAST EQUAL TO THE VOLUME OF WASH LIQUOR USED IN WASHING THE CALCIUM CARBONATE CAKE ON SAID FILTER MEANS, USING SUCH CAUSTIC LIQUOR FILTRATE WITHOUT FURTHER TREATMENT IN THE DIGESTION OF MORE WOOD, REMOVING WASHED CAKE FROM SAID FILTER MEANS, AND SUBJECTING SUCH WASHED CAKE TO CALCINING WITHOUT FURTHER TREATMENT TO PRODUCE LIME FOR CAUSTICIZING MORE GREEN LIQUOR.