Desulphurization wastewater zero discharge treatment process for power plant with low running cost

Abstract

The invention discloses a desulphurization wastewater zero discharge treatment process for a power plant with low running cost. The desulphurization wastewater zero discharge treatment process for the power plant with low running cost comprises a pretreatment softening process and an evaporative crystallization process, wherein desulphurization wastewater is firstly conveyed to an electronic flocculator in the pretreatment softening process, then reaction is carried out with added lime and sodium sulphate, separation and precipitation are carried out by virtue of a primary clarifier, then reaction is carried out with added sodium carbonate, then reaction products enter a secondary clarifier to be separated and precipitated and then to be filtered by virtue of a multi-medium filter, and finally filtrate is discharged into a clean water tank for carrying out the evaporative crystallization process; and in the evaporative crystallization process, firstly pretreated wastewater is subjected to pH regulation, then enters a plate heat exchanger to be heated and then enters an evaporator to be subjected to evaporative crystallization, and crystal separation is carried out on crystal mush. The desulphurization wastewater zero discharge treatment process for the power plant with low running cost has the advantages that low-cost sodium sulphate is used for replacing sodium carbonate, the pretreatment softening process and the evaporative crystallization process are combined, usage amount of a softening medicament is reduced, running cost is reduced, and an evaporative crystallization operation point is controlled, so that crystalline salt is high-purity industrial-grade sodium chloride, and purity is more than 99%.

Description

Technical field [0001] The invention belongs to a water treatment process in the environmental protection industry, and specifically relates to a zero-discharge treatment for desulfurization wastewater of power plants and other high-salinity and high-hardness industrial wastewater. Background technique [0002] At present, most of the desulfurization wastewater from coal-fired power plants at home and abroad is directly discharged after being treated by the coagulation sedimentation process. The technology is relatively mature, although for heavy metals, suspended matter, COD, fluoride, sulfide and other emission standards listed in the Pollutants can be effectively removed, but the soluble substances in the wastewater cannot be effectively removed. The salt content of the discharged wastewater is generally 25000~35000mg / L. If the discharge is improper, it will cause pollution to the environment. [0003] With the increase of social environmental protection awareness and the gradua...

AI Technical Summary

Problems solved by technology

[0007] 3) The mixed salt produced is not only useless, but also requires additional costs and sites for solid waste disposal, while crystallized salt is extremely soluble, and improper disposal will cause secondary pollution

[0011] Due to NaOH and Na 2 CO 3 High cost, resulting in high pretreatment operating costs

When using the lime-soda ash method, since the first step needs to add Ca(OH) 2 , resulting in Ca in water 2+ Concentration increases, adding Na in the second step 2 CO 3 required dosage, so the cost is still higher

Images