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US 5,961,803 AGranted
Leaching process
AssigneeEka Chemicals AB
InventorsJohan Landfors, Roy Hammer-Olsen, Kimona Haggstrom
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AssigneeEka Chemicals AB
InventorsJohan Landfors, Roy Hammer-Olsen, Kimona Haggstrom
Estimating the term…
An increasing problem with the pulping chemical recovery system, is the presence of chloride and potassium in the recovery boiler. Chloride and potassium increase inter alia the stickiness of carryover deposits and dust particles to the recovery boiler tubes, which accelerate fouling, corrosion and plugging of the recovery boiler. As the environmental legislation becomes more stringent, the degree of system closure increases. The present invention relates to a process by which the collected precipitator dust is leached, at a temperature exceeding 50.degree. C., for a residence time sufficient to get a chloride and potassium enriched leach solution and to remove at least a part of the content of metal ions in a solid phase. Said leach solution is electrochemically treated, preferably in an electrodialysis cell, in order to remove at least a part of the chloride and potassium therein. By the present process, the problem of sticky deposits in the recovery boiler can be substantially reduced. This means an improved energy efficiency as well as a higher degree of recovery of the pulping and bleaching chemicals.
A process for reducing the content of metal ions and chloride in a recovery system for pulping chemicals, wherein said metal ions comprise potassium, said process comprising transferring spent liquor from a paper making process to a recovery boiler, burning said spent liquor to form a precipitator dust, and collecting the precipitator dust formed, wherein the precipitator dust is leached with a leaching liquid at a temperature exceeding 50.degree. C. and at a pH above 6 to form a metal ions enriched leach solution and a solid phase comprising metal hydroxides and/or carbonates and organic material, wherein said solid phase is separated from the metal enriched leach solution, whereupon said leach solution is subjected to an electrodialysis treatment for removing at least a part of the metal ions therefrom.
Dependencies are inferred from the claim text.