Thermal power plant desulfurization wastewater resource utilization system and method with low reagent consumption

Abstract

The invention provides a thermal power plant desulfurization wastewater resource utilization system and method with low reagent consumption. The system comprises a flocculent precipitation unit, a filtering unit, a bipolar membrane electrodialysis unit and a concentrated water nanofiltration unit which are sequentially connected in series. The bipolar membrane electrodialysis unit adopts a seven-chamber bipolar membrane electrodialysis assembly unit; the bipolar membrane electrodialysis unit is divided into seven different chambers by a bipolar membrane, an anionic membrane, a cationic membrane, an anionic membrane, a cationic membrane and a bipolar membrane which are arranged in sequence; each chamber is respectively connected with an anolyte circulating box, an acid circulating box, a desulfurization wastewater circulating box, a concentrated water circulating box, a salt circulating box, an alkali circulating box and a catholyte circulating box; the filtering unit is connected withthe desulfurization wastewater circulating tank, the concentrated water circulating tank is connected with the concentrated water nanofiltration unit, the wastewater circulating tank is connected withthe fresh water recycling pipeline, the acid circulating tank is connected with the acid recycling pipeline, and the alkali circulating tank is connected with the alkali recycling pipeline. The system has extremely important significance for realizing zero discharge of desulfurization wastewater, reducing discharge of solid wastes and practically protecting the water ecological environment.

Description

Technical field: [0001] The invention relates to a resource utilization system and method for thermal power plant desulfurization wastewater with low chemical consumption, and belongs to the technical field of zero-discharge treatment of thermal power plant desulfurization wastewater. Background technique: [0002] Desulfurization wastewater is a stream of highly salty wastewater discharged from the wet desulfurization system of thermal power plants to maintain the balance of chloride and magnesium ion concentrations in the desulfurization slurry system. This wastewater contains high concentrations of chloride ions, sulfate ions and calcium and magnesium ions , cannot be reused due to serious corrosion and scaling problems. With the country's increasingly stringent requirements for water ecological environment protection, the demand for zero-discharge treatment of desulfurization wastewater is increasing. The existing zero-discharge technology for desulfurization wastewater...

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Problems solved by technology

The existing zero-discharge technology for desulfurization wastewater is still immature. The mainstream flue gas evaporation technology and membrane concentration + evaporation crystallization technology have major defects. Among them, the flue gas evaporation technology simply realizes the solidification of pollutants in wastewater. , so that the pollutants are transferred to the fly ash. At the same time, due to the increase of the moisture content of the flue gas, the acid dew point rises, and there is a greater risk of corrosion for the operation of the unit equipped with a low and low temperature economizer.

Although the membrane concentration + evaporation crystallization technology realizes the recovery and utilization of chloride ions, it needs to thoroughly soften the desulfurization wastewater, thus adding a large amount of sodium carbonate and sodium hydroxide. Due to the high price of sodium carbonate and sodium hydroxide, The cost of chemicals is huge. Taking the desulfurization wastewater with calcium ion concentration of 2000mg / L and magnesium ion concentration of 5000mg / L as an example, the dosage of sodium hydroxide is 16.5Kg / m 3 , sodium carbonate dosage 5.3Kg / m 3 , the cost of softening agents is high; at the same time, due to the large fluctuations in the quality of desulfurization wastewater and the lack of reliable calcium ion online concentration meters, it is difficult to adjust the amount of dosing. Once calcium ions are not completely removed, it is easy to cause scaling and fouling

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