Method and system for crystallizing and separating fly ash washing liquid and separating and purifying sodium salt and potassium salt based on seed crystal method

Abstract

The invention discloses a method and a system for crystallizing and separatingfly ash water washing liquid and separating and purifying sodium salt and potassium salt based on a seed crystal method. The method comprises the following steps: preheating the fly ash water washing liquid, and then carrying out evaporation concentration treatment; crystallizing and layering the concentrated feed liquid in an evaporation crystallizer to obtain crystal slurry, concentrated salt liquid and salt slurry; separating the crystal slurry in a gypsum separator to obtain crystallized gypsum and gypsum mother liquor; treating the salt slurry in a sodium chloride separating and purifying device to obtain sodium chloride crystal salt, supernate and sodium chloride mother liquor; and treating the supernate in a potassium chloride separating and purifying device to obtain potassium chloride crystals, potassium chloride crystal salt and potassium chloride mother liquor. The method and the system can effectively prevent the evaporator from scaling, ensure stable operation of the system and improve the quality of produced salt; the crystallized gypsum is subjected to dechlorination treatment in a water washing or leaching mode, and a gypsum product is recycled; generated condensate water and gypsum eluent are recycled; in the evaporative crystallization process, mother liquor is circularly concentrated and evaporated, and the salt yield is increased.

Description

technical field [0001] The invention relates to a treatment method and a treatment system for waste incineration fly ash, in particular to a method for washing and crystallizing fly ash based on a seed crystal method, a method for separating and purifying sodium salt and potassium salt, and a treatment system, belonging to the field of reprocessing and utilization of waste incineration fly ash . Background technique [0002] Waste incineration fly ash contains a large amount of chloride ions, and because it is rich in heavy metal inorganic harmful substances and high concentrations of dioxin organic carcinogens, it is listed as solid hazardous waste (code name HW18) by the state. Utilizing cement kiln co-processing waste incineration fly ash technology is a new treatment method in the development of fly ash disposal technology. Its main process is to wash waste incineration fly ash, and the remaining fly ash after water washing is dried to make cement and washed with water. ...

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Problems solved by technology

[0005] For the process of evaporating salt from fly ash or kiln ash washing liquid with high salt content, although the existing technology has realized to a certain extent that the equipment is not easy to scab, the product salt quality is good, and the system operates stably, but the composition of the fly ash washing liquid is complicated. And the salt concentration is high. During the evaporation process, the feed liquid is continuously evaporated, and the salt crystals in the concentrated feed liquid will adhere to the surface of the evaporator, resulting in uneven heat transfer and low heat transfer efficiency. This will not only cause energy waste, but also require Periodic outage for cleaning seriously affects production efficiency

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