THIS INVENTION REFERS TO THE PROCESS FOR THE RECOVERY OF ALCALI AND HEAT OF A BLACK RESIDUAL LIQUID (5), CONTAINING SILICATE, FROM A COOKING IN SOSA OF, FOR EXAMPLE, GRASS, RODS, STRAW AND BAGAZO. IN THE PROCESS, THE BLACK LIQUOR (5) IS TREATED WITH A GAS (6) CONTAINING CARBON DIOXIDE TO PRECIPITATE SILICE AND LIGNINE; THE PRECIPITATE (9) SEPARATES (2) FROM THE BLACK LIQUOR, WHICH IS EVAPORATED (3) AND SUBMITS TO COOKING (4) TO GENERATE HEAT AND RECOVER A SODIUM CARBONATE FUSION. IN THE INVENTION, THE BLACK LIQUOR (5), WHICH CONTAINS SILICATE, IS NEUTRALIZED WITH AN EXCESS OF GAS (6) CONTAINING CARBON DIOXIDE, WHICH PREFERREDLY INCLUDES MORE THAN 60% BY CARBON DIOXIDE VOLUME. THE EVAPORATION (3) OF THE BLACK LIQUOR IS BASICALLY PLACED AFTER THE PRECIPITATE (9) RICH IN SILICE IS SEPARATED (2). THE COMBUSTION IS CARRIED OUT WITH GAS OF PURE OXYGEN OR AIR ENRICHED WITH OXYGEN (14), ONCE THE BLACK LIQUOR HAS BEEN RAISED TO A NEAR TEMPERATURE AS ITS POINT OF BOILING, BY DIRECT CONTACT WITH THE HOT GASES OF ESCAPE COMBUSTION, ALL THESE OPERATIONS UNDER A SUBSTANCIAL OVERPRESSURE OF AT LEAST 100 KPA. WITH THIS PROCEDURE, A FUSED SODIUM CARBONATE MATERIAL IS RECOVERED AND A GAS IS FORMED (17) THAT CONTAINS MORE THAN 60% IN VOLUME OF CARBON DIOXIDE, USED TO NEUTRALIZE THE BLACK RESIDUAL LIQUOR (5) THAT CONTAINS SILICATE.
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