Electrolytic causticizing of smelt from a kraft recovery furnace
AssigneesInstitue of Paper Science and Technology Inc., Georgia Tech Research Corporation
InventorsJack Winnick, Peter H. Pfromm
Life of this patent
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Abstract
An electrochemical process is provided for treatment of molten kraft smelt produced from black liquor in a kraft recovery boiler. Treated smelt can be contacted with water to produce white liquor which can be re-used or recycled in the kraft process.
Claims16
A method for electrolytically treating molten Kraft smelt to provide sodium sulfide to a Kraft process, the molten Kraft smelt comprising sodium sulfide, sodium sulfate, sodium chloride and alkali metal carbonates, the method comprising:
- providing an electrolytic cell having an anode and a cathode;
- feeding the molten Kraft smelt into the cell, wherein the molten Kraft smelt comprises sodium carbonate, potassium carbonate, sodium sulfide, sodium sulfate and sodium chloride, the molten Kraft smelt having a temperature of from about 750° C. to about 950° C.;
- and
- applying an electrical potential which is effective for preventing reactions of sulfide in the molten Kraft smelt, the potential between the anode and the cathode with the molten Kraft smelt therebetween in an environment that is substantially without liquid water,
- whereby the method is effective for providing sodium sulfide to a Kraft process and at least about 75% of the alkali metal carbonates in the molten Kraft smelt are converted to alkali metal oxides or alkali metal hydroxides.
A method for electrolytically treating molten Kraft smelt generated in a process for making pulp, the method to provide sodium sulfide to a Kraft process, the method comprising:
- filtering and washing brown pulp to generate a waste liquor having dissolved organic materials and spent pulping chemicals;
- feeding the waste liquor to an evaporator wherein the waste liquor is concentrated;
- burning the concentrated waste liquor to produce a molten Kraft smelt comprising sodium sulfide, sodium sulfate, sodium chloride and alkali metal carbonates selected from the group consisting of sodium carbonate, potassium carbonate and mixtures thereof;
- directing the molten Kraft smelt to an electrolytic cell at a temperature of from about 750° C. to about 950° C.;
- electrolytically treating the molten Kraft smelt in a system without liquid water at electrical potential which is effective for preventing reactions of sulfide in the molten Kraft smelt to provide a treated molten Kraft melt and to convert at least about 75% of the alkali metal carbonates therein to alkali metal oxide or alkali metal hydroxide, the method being effective for providing sodium sulfide to the Kraft process, the potential between the anode and the cathode with the molten Kraft smelt therebetween in an environment that is substantially without liquid water;
- and
- contacting the treated molten Kraft smelt with water to produce a caustic liquor.
Dependencies are inferred from the claim text.