Desulfurization wastewater zero discharge treatment system and method by utilizing flue gas and electrodialysis

Abstract

The invention relates to a desulfurization wastewater zero discharge treatment system and method by utilizing flue gas and electrodialysis. The system comprises a chemical precipitation flocculation unit, a lime-flue gas softening unit, a membrane concentration unit and an evaporation and crystallization unit; based on the system, firstly the chemical precipitation flocculation unit is utilized for treating desulfurization wastewater raw water, then lime milk and CO2 in the flue gas of a power plant are utilized for efficiently removing hardness ions such as calcium and magnesium in effluent of the chemical precipitation flocculation unit, and carbon dioxide emission reduction is realized; softening effluent is subjected to ultrafiltration treatment and then enters an ion selective electrodialysis unit to be subjected to efficient concentration, so that NaCl concentrated water is obtained, and further NaCl industrial salt is obtained through evaporation crystallization; electrodialysis fresh water passes through a low pressure volume-type reverse osmosis membrane, so that recyclable fresh water is obtained; and reverse osmosis concentrated water reenters an electrodialysis unit. The system and method which are provided by the invention have the advantages that CO2 in the flue gas is utilized for replacing expensive sodium carbonate, so that the softening cost is reduced, and CO2 emission reduction is also promoted; and an electrodialysis process is introduced for concentrating, so that electrodialysis and reverse osmosis are respectively under the optimal treatment conditions, and energy consumption is reduced.

Description

technical field [0001] The invention relates to the technical field of treating desulfurization wastewater by adopting zero-discharge technology, in particular to a zero-discharge treatment system and method for desulfurization wastewater using flue gas and electrodialysis. Background technique [0002] At present, most coal-fired power plants in my country use limestone / gypsum wet desulfurization technology (WFGD) for flue gas desulfurization, and a certain amount of desulfurization wastewater needs to be discharged regularly during the desulfurization process. The water quality of desulfurization wastewater is extremely poor, and it has the characteristics of high salt content, high content of suspended solids, high hardness, strong corrosion, and large changes in water quality with time and working conditions. In addition, desulfurization wastewater also contains trace heavy metal elements, such as mercury, chromium, cadmium, lead, etc., many of which are the first type o...

AI Technical Summary

Problems solved by technology

The reverse osmosis method has the advantages of simple process and high desalination rate. However, there are some inherent problems in the reverse osmosis process that cannot be solved: the recovery rate of product water is low; Low; high salt content leads to high operating pressure and increased energy consumption

When treating desulfurization wastewater with poor water quality, the operating pressure of the reverse osmosis method often reaches above 6MPa, and the investment and operation costs are further increased

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