LEACHING OF CHLORIDE AND POTASSIUM FROM ELECTRIC FILTER ASHES

摘要

The invention concerns an arrangement and a method for the leaching of electrical filter ash that contains potassium and chlorides. The electrical filter ash undergoes mixing in the invention with leaching fluid in a first recirculation zone. The mixture of electrical filter ash and leaching fluid is subsequently led to a second recirculation zone. The mixture in this zone is placed into a flow that is toroidal relative to the horizontal plane. The fluid is forced to recirculate in the toroidal flow downwards at its outer edges and upwards at its centre, whereby crystal growth of sludge particles is promoted in this toroidal flow. Fluid that is enriched in potassium and chlorides is withdrawn from the second recirculation zone from the outer edge of the enforced toroidal flow, while slurry particles sink down into a third sedimentation zone. Condensate is added in the sedimentation zone such that this is expelled through the slurry particles. Leaching fluid is withdrawn from the sedimentation zone, which fluid is added at the first zone in order to be mixed with the electrical filter ash.