Power plant variable-load coal-fired furnace desulfurization wastewater zero discharge system

Abstract

The invention discloses a power plant variable-load coal-fired furnace desulfurization wastewater zero-discharge system which comprises an adjustable low-temperature flue gas waste heat recycling system device, a desulfurization wastewater evaporation and concentration system using waste heat as a heat source, a desulfurization wastewater pretreatment system and a system for finally treating concentrated desulfurization wastewater to zero discharge. The system has the beneficial effects that the influence of furnace load adjustment automatically performed by most power plant coal-fired furnaces along with power grid load change on a furnace tail flue gas waste heat recovery device and a desulfurization flash evaporation concentration system can be conveniently adapted through system adjustment, so that the waste heat recovery system and the low-temperature flash evaporation concentration system are integrally stable in operation; by automatically adjusting the temperature difference between the wall surface temperature of the waste heat recovery device and the temperature of the flue gas, the waste heat exchange amount is basically unchanged, a higher energy-saving effect is achieved, the waste heat of the flue gas is fully utilized, desulfurization wastewater does not need to be subjected to dosing pretreatment, and the wastewater treatment operation cost is reduced.

Description

technical field [0001] The invention relates to the field of energy-saving recovery and utilization of low-temperature flue gas waste heat and the field of environmental protection water treatment for zero-discharge treatment of desulfurization wastewater. Specifically, it relates to a zero-discharge system for desulfurization wastewater of a variable-load coal-fired boiler in a power plant. Background technique [0002] Desulfurization wastewater is the wastewater generated after dedusting and desulfurization of flue gas in coal-fired power plants. Because the desulfurization process requires regular replenishment of water to the desulfurization system due to evaporation and flue gas carryover, but the quality of replenishment water is not high, so basically all recycled reclaimed water in power plants will be collected in the desulfurization tower as supplementary water, including: Circulating cooling tower drainage, reverse osmosis concentrated water, acid-base wastewater...

AI Technical Summary

Problems solved by technology

Disadvantages: The operating conditions when the boiler load changes are not considered. The evaporation of a large amount of desulfurization wastewater when the flue gas temperature is lower than 130 degrees will cause the flue gas temperature to drop too much and the flue gas humidity to increase, which will cause subsequent flue and equipment corrosion , so it is not suitable for variable load coal-fired boilers in power plants

Disadvantages: First, the desulfurization wastewater needs to be softened by dosing and turbidity removal, and the operating cost is high; second, when the boiler is operating at variable load, the amount of exhaust steam is small, and high-quality steam needs to be used for heating and evaporation, which increases the operating cost; third, crystallization The product cannot be used as industrial salt

Disadvantages: the waste water is softened and treated many times, and the cost of adding chemicals is very high; the bypass flue uses high-temperature flue gas evaporation and crystallization, which actually reduces the thermal efficiency of the boiler and increases the operating cost

[0014] Comparing the above-mentioned national environmental protection policies, various papers, inventions, etc., we can draw the following conclusions: the zero-discharge treatment technology for desulfurization wastewater is feasible, and the direction of policy guidance is correct, but in practical applications, the operating energy consumption (including chemicals) high cost, electricity cost, steam cost, etc.) is an important reason why this type of project cannot be promoted; in addition, most of the large unit boilers in domestic power plants are operating under variable load conditions. At this time, the flue spraying cannot be used normally, and the desulfurization wastewater Large amount, low-temperature spraying with large amount of water will make the flue gas temperature too low, which will corrode subsequent equipment and flue

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