Research And Design A Low Temperature And Pressure Ev Aporation System For WFGD Wastewater

Limestone gypsum wet process(WFDG)is the most widely used desulfurization technology for flue gas desulfurization system in thermal power plant,and the desulfurization wastewater generated by this process has become the difficult point of wastewater treatment.Commonly,using physical and chemical methods have lots of shortcomings,such as high operating costs,hard to remove the Cl-,and so on.How to achieve desulfurization wastewater zero discharge efficiently at lower costs has become a hot spot in the current stage.This paper puts forward a low temperature and pressure evaporation technology for desulfurization wastewater zero discharge.The process is designed and correspinding experiments are made to investigate this technology.In this paper,a design and research on evaporation and heat pump of low temperature and pressure wastewater zero discharge evaporation technology were carried out.Based on the premise of desulfurization wastewater treatment capacity,the treatment quantity is lt/h.First of all,evaporator structure,the mass flow and energy flow of whole system were designed and calculated.Then,the design and type selection of the compressor,expansion valve and heat exchanger of heat pump were carried out.When the temperature in the tube heat exchanger was constant,with the increase of flow velocity in the tube,the pressure was increased and the heat transfer area of exchanger was gradually decreased.when heat flow and flow velocity in the tube was constant,pressure drop in the tube and heat transfer area of exchanger were mainly affected by temperature-----decreased with reducing the temperature of the tube side outlet.Based on the design.electric heating tube and water-cooled heat exchanger are used as energy supplyinstead of heat pump.The processing capacity of the test device is 15kg/h.Desulfurization wastewater is used as the main experimental material.Performances of the device at different temperatures,pressures and salt concentrations are studied in the condition of evaporation and condensation of water treatment capacity,conductivity,etc.As a result,It is found that saturated steam pressure of the desulfurization wastewater is gradually increasing with the increase of temperature.In the case of constant temperature,vapor pressure of wastewater was less than that of water.With the increase of the mass fraction,boiling point increased gradually.Evaporation capacity both of water and desulfurization wastewater are decreased with the increase of the temperature in the tank,and increased with the increase of the temperature outlet of the nozzle.When nozzle temperature is ranged from 50℃ to 58℃ and tank temperature reach the same,the evaporation capacity of water is less than that of wastewater.The condensation capacity show similar trand with characteristics of evaporation capacity.When conductivity of desulfurization wastewater in the evaporator is increased,the percentage of salt particles in the steam is also increasedwith constant evaporation pressure namely pumping pressure.Low temperature and low pressure evaporation crystallization technology of desulfurization wastewater can deal with desulfurization wastewater effectively.After the treatment,the soluble salt is significantly lower than the original desulfurization wastewater,and water quality can reach the standard of recycling in power plant.The experimental results show that the low temperature and pressure evaporation system for desulfurization wastewater zero discharge is feasible.