Method for washing and dechlorinating fly ash and recycling washing liquid and system for realizing method

Abstract

The invention discloses a method for washing and dechlorinating fly ash and recycling water washing liquid and a system for realizing the method. The method comprises the following steps: preparing fly ash slurry, and carrying out dechlorinating separation treatment to obtain washed fly ash and water washing liquid; sequentially carrying out purification, preheating, concentration and evaporative crystallization treatment on the water washing liquid to obtain crystal slurry liquid, concentrated salt liquid and salt slurry; and performing crystallization separation treatment on the crystal slurry to obtain crystallized gypsum and feed liquid, and performing separation treatment on the salt slurry to obtain crystallized salt, mother liquor and non-crystallized mother liquor. The invention further discloses a system for implementing the method. The gypsum seed crystal method is applied to evaporative crystallization, decalcification treatment in the water washing liquid purification process is omitted, a heat exchanger and an evaporative crystallizer are prevented from scaling, mass and heat transfer energy consumption is reduced, and the quality of crystallized salt is improved; the crystallized gypsum is washed with water to remove soluble impurities in the gypsum, so that the additional value of the gypsum is increased; the non-crystallized mother liquor is treated by adopting a membrane technology, and fresh water and concentrated water obtained after treatment are recycled, so that the load of water washing and evaporation units is reduced.

Description

technical field [0001] The present invention relates to a method and system for fly ash dechlorination and recycling, in particular to a method for elution of chlorine from waste incineration fly ash and recycling of washing liquid based on the seed crystal method. The present invention further relates to the method for realizing the method The system belongs to the field of fly ash dechlorination and recycling. Background technique [0002] Fly ash is a powder material with light bulk density and small particle size collected in flue gas pipes, flue gas purification, separators and dust collectors during the waste incineration process. Fly ash is listed as solid hazardous waste (code-named HW18) by the state because it is rich in heavy metal inorganic harmful substances and high-concentration dioxin organic carcinogens. [0003] At present, the main waste incineration fly ash disposal technologies in China include: cement solidification, melting and sintering solidificatio...

AI Technical Summary

Problems solved by technology

[0007] One of the objectives of the present invention is to provide a method based on the seed crystal method for the elution of chlorine in waste incineration fly ash water and the recycling of water washing liquid, so as to solve the problems of high water consumption in the elution process of fly ash in the prior art and the evaporation and crystallization process. The equipment is easy to scale, the forced circulation evaporation equipment consumes a lot of energy, and the output of crystallized salt is low and the quality is poor.

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