| 摘要 |
In a process for evaporating a solution containing KCl and NaCl to precipitate NaCl and then cooling the KCl-rich solution to crystallize out KCl, the resultant KCl-depleted solution is passed upwardly into the lower part of the evaporator to elutriate solid impurities and enable pure NaCl to be recovered. Preferably a series of 4 steam heated evaporators are used, which increase in temperature in the direction of liquid flow, each having a narrower leg in its lower part. The feed solution may be used as elutriating liquid in evaporators 1 and 2, and the recycle solution in 3 and 4. NaCl withdrawn from the legs of evaporators 1 and 2 may be fed to one centrifuge, and that from evaporators 3 and 4 to another; effluent liquid may be used as part of the elutriating liquid in evaporators 2 and 4 resp. The recycle solution may also be used as part of the feed to evaporator 3. Tables showing the temperatures and amounts of NaCl, KCl, MgCl2, CaCl2, and CaSO4 at all stages are given.ALSO:In a process for evaporating a solution containing KCl and NaCl to precipitate NaCl and then cooling the KCl-rich solution to crystallise out KCl, the resultant KCl-depleted solution is passed upwardly into the lower part of the evaporator to elutriate solid impurities and enable pure NaCl to be recovered. As shown, four evaporators connected in multiple-effect are used which increase in temperature in the direction of liquid flow, each having a narrow leg 11 in its lower part. The feed solution is introduced into evaporator 4; and the liquor withdrawn from evaporator 1 is cooled to precipitate KCl. The direction of steam flow is countercurrent to the direction of solution flow. The feed solution may be used as elutriating liquid in evaporators 1 and 2, and the recycle solution in evaporators 3 and 4. NaCl withdrawn from the legs of evaporators 1 and 2 may be fed to one centrifuge, and that from evaporators 3 and 4 to another; effluent liquid may be used as part of the elutriating liquid in evaporators 2 and 4 resp. The recycle solution may also be used as part of the feed to evaporator 3.
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