Treatment method of catalytic cracking flue gas desulfurization wastewater

Abstract

The invention provides a treatment method of catalytic cracking flue gas desulfurization wastewater. The treatment method comprises the following steps: fully utilizing waste heat of high-temperature flue gas, concentrating circulation slurry in a washing tower, and controlling the concentration of the circulation slurry, thus ensuring normal operating of a desulfurization system; meanwhile, carrying out pretreatment (flocculating, filtering, removing calcium and magnesium ions, reducing COD (Chemical Oxygen Demand) through oxidization and the like) on concentrated discharged wastewater, enabling the wastewater to meet the feeding requirements of a concentration system, and then carrying out evaporation and crystallization (multi-effect evaporation or MVR (Mechanical Vapor Recompression)), thus realizing zero emission of salt-containing wastewater and recycling of inorganic salt. According to the technology, a sodium alkaline flue gas desulfurization technology and an inorganic salt evaporative crystallization recovery technology are organically integrated, the problems of membrane pollution and membrane scaling during a membrane concentration process, large investment, high energy consumption and the like are avoided, the emission problem of salt-containing wastewater in an alkaline washing technology is completely solved, and zero emission is really realized; meanwhile, separated crystallization is carried out on inorganic sodium salt products, the recycled products are used as products, the problems of mixed salt and hazard waste are solved, and secondary pollution is removed.

Description

technical field [0001] The invention relates to the technical field of sewage treatment, in particular to a treatment method for catalytic cracking flue gas desulfurization wastewater. Background technique [0002] At present, there are hundreds of sets of catalytic cracking flue gas desulfurization devices in operation in China, and most of them adopt disposable sodium-alkali desulfurization technology. To the liquid phase, a large amount of salty wastewater is discharged, forming secondary pollution. For the recovery of saline wastewater, the combined process of membrane separation technology and evaporation crystallization technology is mainly used, including the use of reverse osmosis membrane (RO), electrodialysis (EDR), ultrafiltration (UF) and membrane reactor (MBR). The salt concentration is increased from 3% to 5% to 10% to 15%, and then multi-effect evaporation or mechanical vapor recompression (MVR) technology is used to increase the salt concentration to the cry...

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Problems solved by technology

[0006] The first purpose of the present invention is to provide a treatment method for catalytic cracking flue gas desulfurization wastewater to solve the secondary pollution problem caused by the generation of a large amount of mixed salt in the prior art when treating this type of wastewater. The treatment method of gas desulfurization wastewater makes full use of the waste heat of high-temperature flue gas, concentrates the circulating slurry in the washing tower, and ensures the normal operation of the desulfurization system by controlling the concentration of the circulating slurry; at the same time, pre-treats the concentrated wastewater ( Flocculation, filtration, removal of calcium and magnesium ions, oxidation reduction of COD, etc.), so that the discharged wastewater meets the feed requirements of the concentration system, and then through evaporation and crystallization (multi-effect evaporation or MVR) to achieve zero discharge of saline wastewater and recovery of inorganic salts

Integrate sodium-alkali flue gas desulfurization and inorganic salt evaporation and crystallization recovery process organically, avoid membrane fouling, scaling, large investment and high energy consumption in the membrane concentration process, and completely solve the problem of salty wastewater in the alkaline washing process Discharge problem, truly realize "zero discharge", and at the same time carry out fractional crystallization of inorganic sodium salt products, make the recovered products into products, solve the problem of mixed salt hazardous waste, and eliminate secondary pollution

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