Desulfurization wastewater zero discharge system for gradient utilization of flue gas waste heat and working method thereof

Abstract

The invention discloses a desulfurization wastewater zero discharge system for gradient utilization of flue gas waste heat and a working method of the desulfurization wastewater zero discharge system,and belongs to the technical field of desulfurization wastewater treatment. The system comprises a first air inlet device, a second air inlet device, a first air heat exchanger, a second air heat exchanger, a first flue gas heat exchanger, a second flue gas heat exchanger, a spray drying tower, a dust remover, an evaporation concentration tower and a desulfurization wastewater pool. High-temperature flue gas at the tail of a boiler is used for increasing the air temperature, desulfurization wastewater is evaporated and dried by high-temperature air through gradient utilization of the temperature, the cooled air is used for concentrating and reducing the desulfurization wastewater, the dust remover is used for recovering dried salt in the wastewater, and the air heat exchanger is used forrecovering heat in air at an outlet of a system for preheating the air. Compared with a conventional desulfurization waste water zero-discharge method, waste heat in flue gas is fully utilized, concentration and drying of waste water are synchronously achieved, the influence on water balance and material balance of gas in an original flue is small, and good application prospects are achieved.

Description

technical field [0001] The invention belongs to the technical field of desulfurization wastewater treatment, and in particular relates to a desulfurization wastewater zero discharge system for cascaded utilization of flue gas waste heat and a working method thereof. Background technique [0002] Domestic coal-fired power plants usually use the limestone-gypsum method to desulfurize the flue gas, resulting in a large amount of wastewater. Desulfurization wastewater has the characteristics of low pH, high salt content, and high heavy metal content. It is still highly polluting after being treated by traditional pH adjustment, coagulation, and precipitation processes. With the increasing environmental protection requirements, zero discharge of desulfurization wastewater has gradually become the technical trend of power plant water treatment. [0003] Membrane concentration + evaporation crystallization is the technical route usually adopted for zero discharge of industrial was...

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Problems solved by technology

However, the actual operation effect of membrane concentration + evaporative crystallization is not ideal, mainly in the following aspects: the membrane system has high requirements on water quality, usually requires softening and other pretreatment links, and the process flow is long; during long-term operation, membrane pollution is serious, and equipment maintenance Frequent; the operating pressure of the reverse osmosis membrane is relatively high, and the operating cost is high; the mixed salt produced by evaporation and crystallization cannot be used, and is usually disposed of as hazardous solid waste

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