System and method for evaporating desulfurization wastewater by using exhaust gas waste heat under underload working condition

Abstract

The invention relates to a system and a method for evaporating desulfurization wastewater by using exhaust gas waste heat under an underload working condition. The system comprises an economizer fumebypass subsystem, a desulfurization wastewater high-temperature flue bypass evaporation subsystem as well as an air pre-heater bypass flue, wherein the economizer fume bypass subsystem comprises an economizer bypass flue; the desulfurization wastewater high-temperature flue bypass evaporation subsystem comprises a softening tank, a concentration device, a wastewater pump, a wastewater preheater and a double-fluid atomization ejector which are connected in sequence through a wastewater pipeline; the softening tank is connected with a desulfurizer; an evaporator is arranged on the air pre-heaterbypass flue; the double-fluid atomization ejector is arranged at the top end inside the evaporator. The invention further relates to a method for achieving zero desulfurization wastewater emission under the underload working condition on the basis of the system for evaporating the desulfurization wastewater by utilizing the exhaust gas waste heat. By adopting the system and the method, the energyutilization rate of a machine set is increased, and zero wastewater emission is achieved.

Description

technical field [0001] The invention relates to a system and a method for evaporating desulfurization wastewater by using exhaust waste heat in a coal-fired power plant under low-load conditions. The system can improve the energy utilization rate of a unit and realize zero discharge of wastewater, and belongs to the field of thermal power generation energy saving and emission reduction. Background technique [0002] In recent years, domestic coal-fired units have faced a difficult task of peak regulation, and most units have been operating at low load for a long time. The reduction of the load leads to the decrease of the exhaust gas temperature of the boiler. When the flue gas temperature at the outlet of the economizer is too low, the efficiency of the SCR denitrification device will be greatly reduced, and even the entire operation will be stopped, and the concentration of nitrogen oxides in the flue gas will not reach the national standard. low emission requirements. Th...

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Problems solved by technology

[0004] To sum up, when the unit is running at reduced load, due to the drop in flue gas temperature, the desulfurization wastewater needs to consume more high-temperature flue gas to completely evaporate, which will reduce the boiler efficiency; the economizer flue gas bypass technology is improving the denitrification effect At the same time, the temperature of the flue gas is also increased, which increases the heat loss of the boiler exhaust

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