Redissolution supplementary salt, nitrate and salt separation system and process for zero discharge of desulfurization wastewater

Abstract

The invention provides a desulfurized waste water zero-emission technology adopting redissolution for salt and nitrate supplementation and realizing salt separation for recycling. The technology comprises steps as follows: a membrane concentration liquid after concentrated by a softening membrane is preheated and then enters an MVR (mechanical vapor recompression) system for further concentration, an MVR concentrated solution enters a redissolution tank, salt and nitrate are supplemented to saturation, a mixed solution enters a four-effect evaporation and crystallization system, NaCl and Na2SO4 are crystallized and precipitated out respectively, are separated by a centrifugal salt removing system and a centrifugal denitration system and are dried, and NaCl and Na2SO4 with the purity higher than 98% are obtained. With the technological combination of the membrane, the MVR and the multi-effect evaporation, separation of salt and nitrate is realized, and meanwhile, the operating cost is greatly reduced; with the adoption of the technology of realizing salt and nitrate supplementation through redissolution, the disturbance of water quality fluctuation on operation and control nodes of a salt production system is avoided, so that the system can operate stably for a long term, and the purity of salt and nitrate is guaranteed.

Description

technical field [0001] The technology relates to the field of desulfurization wastewater in power plants, specifically a zero-discharge system and process for recovering desulfurization wastewater by dissolving back, supplementing salt, nitrate and separating salt. Background technique [0002] SO in the flue gas of thermal power plants in my country 2 The emissions are strictly controlled, and limestone wet flue gas desulfurization is currently the most widely used flue gas desulfurization method at home and abroad. The main characteristics of the desulfurization wastewater produced by wet desulfurization are acidity, high turbidity, a large amount of heavy metals, high COD, and extremely high salinity; the main salt ions include Na + , Cl - , SO 4 2- ions, in addition to a small amount of Ca 2+ , Mg 2+ , F - and all-silicon plasma. At present, domestic power plants adopt desulfurization wastewater treatment methods including chemical coagulation treatment method an...

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Problems solved by technology

Among them, the chemical coagulation treatment method is complex in process, the dosing system is huge, and the effluent quality basically does not meet the current discharge standards in my country; the pretreatment + evaporation crystallization process realizes the separation of desulfurization wastewater into standard condensed water and solid miscellaneous salts, realizing The zero discharge of desulfurization wastewater is achieved, but the amount of solid miscellaneous salts produced is large and the composition is complex, and its further disposal is also a difficult issue, and it is directly evaporated after pretreatment, resulting in a large amount of water, huge equipment, and large investment

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