System and method for softening treatment of desulfurization wastewater of coal-fired power plant

Abstract

The invention discloses a system and a method for softening treatment of desulfurization wastewater of a coal-fired power plant. A primary reaction tank, a primary clarification tank, a secondary reaction tank and a secondary clarification tank are arranged, lime milk, sodium sulfate, polymeric ferric sulfate and polyacrylamide are added to the primary reaction tank for a primary reaction and clarified through the primary clarification tank, Mg(OH)2 and CaSO4*2H2O in the wastewater after the primary reaction are removed, the mixture has a secondary reaction in the secondary reaction tank, smoke is fed into the secondary reaction tank and is settled in the secondary clarification tank, CaCO3 is settled, and softening treatment of the desulfurization wastewater of the coal-fired power plant is completed. The system is simple in structure and easy to implement and facilitates industrial production; when the softening treatment effect is met, that is, the content of Mg<2+> is smaller than or equal to 5 mg / L and the content of Ca<2+> is smaller than or equal to 5 mg / L, the adding amount of chemical is reduced, and the chemical operation cost is reduced, so that the operation cost of a zero discharging system for the desulfurization wastewater of the coal-fired power plant is reduced, and the system has important economic benefits and environmental benefits.

Description

technical field [0001] The invention belongs to the technical field of zero discharge of waste water from coal-fired power plants, and relates to a system and method for softening and treating desulfurization waste water from coal-fired power plants. Background technique [0002] In order to achieve zero discharge of desulfurization wastewater in coal-fired power plants, the desulfurization wastewater must be solidified. Generally, evaporation and crystallization can be used for solidification. Desulfurization wastewater contains a large amount of scaling ions such as calcium and magnesium, generally Ca 2+ The concentration can reach 600~900mg / L, Mg 2+ The concentration can reach 3000~5000mg / L. At the same time, due to the presence of a large amount of sulfate ions, the calcium sulfate in the wastewater is in a supersaturated state, and the water quality is unstable. It is extremely easy to form scaling on the heat exchange surface of the evaporation crystallization equipm...

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Problems solved by technology

[0003] At present, the coal-fired power plants with good zero-discharge operation of desulfurization wastewater all adopt a treatment process combining softening and evaporation crystallization, among which the softening process adopts the double alkali method (lime plus sodium carbonate two-stage softening treatment), the system effluent is stable and the water quality is good (Mg 2+ ≤5mg / L,Ca 2+ ≤5mg / L), so that the chemical cleaning cycle of the evaporation and crystallization equipment is longer, and the chemical cleaning cost is lower, but the chemical operating cost of the softening treatment process is as high as 32.5 yuan / (m 3 ﹒ waste water), the high operating cost of reagents has greatly restricted the promotion of this process, so the zero discharge project of desulfurization waste water in coal-fired power plants is still rarely implemented

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