System and method for grading purification of potassium salt and sodium salt in fly ash water washing solution

Abstract

The invention relates to a system and a method for grading purification of a potassium salt and a sodium salt in a fly ash water washing solution. The system comprises a thickener, a cooling kettle, ahorizontal screw centrifuge, a potassium salt mother liquor tank, a potassium salt mother liquor heat exchanger and an MVR evaporation system which are sequentially connected, the cooling kettle is further connected with a vacuum pumping system and an MVR water supply tank, the horizontal screw centrifuge is also connected with a fine salt tank, and the fine salt tank is connected with a sodium salt centrifuge. The system of the invention can realize the effective separation of sodium chloride and potassium chloride in the fly ash water washing solution to obtain a high-purity potassium chloride product and make the purity of potassium chloride reach 92%, and also can reduce the treatment cost of fly ash, alleviate the fine salt enrichment degree of the MVR system, promote the continuousand stable running of the MVR system and prolong the period of scaling and salt attachment of a crystallization separator, caused by the fine salts in the MVR system.

Description

technical field [0001] The invention belongs to the technical field of hazardous waste treatment, and in particular relates to a system and method for separating and purifying potassium and sodium salts of fly ash washing liquid. Background technique [0002] MVR is the abbreviation of mechanical vapor recompression technology. It uses the secondary steam and its energy generated by the evaporation system itself to work through the compression of the steam compressor to increase the thermal energy of the secondary steam. This cycle supplies heat to the evaporation system, thereby reducing the impact on An energy-saving technology that meets the demand for external energy, and is currently widely used in the fields of chemical industry, food, papermaking, medicine, seawater desalination and sewage treatment. [0003] Garbage fly ash refers to the residue collected in the flue gas purification system of waste incineration power plants, which contains soluble substances such as...

AI Technical Summary

Problems solved by technology

At present, the MVR system is used for evaporative desalination of the fly ash washing liquid. During the operation of the MVR system, it is easy to cause wall formation, scarring and blockage due to the continuous enrichment of potassium chloride, which leads to shutdown and mother liquor emptying operations, which affects the MVR system. continuous operation of

[0004] In order to ensure the continuous operation of the MVR system and realize the classified recovery of potassium chloride and sodium chloride resources in the fly ash washing liquid, CN206793091U discloses a potassium and sodium salt separation system combined with the MVR system, mother liquor, insulation filtration, cooling and crystallization And the main process of centrifugation. When potassium chloride is used to treat the critical saturation point, the salt mother liquor is subjected to heat preservation filtration, cooling crystallization, centrifugal separation and other processes to realize the effective separation of potassium chloride and obtain high-purity potassium chloride products. However, there are problems such as the reflux of potassium salt mother liquor affecting the evaporation of the MVR system, the difficulty in establishing the balance between the old and new systems, the low purity of recovered potassium chloride, and low recovery efficiency, which need further optimization.

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