| The zero-emission treatment of wastewater from wet flue gas desulfurization system has been increasingly valued with the improvement of pollutant emission standards for coal-fired power plants.Desulfurization wastewater has many types of pollutants and large fluctuations in water quality.It is difficult to achieve zero discharge of desulfurization wastewater by traditional treatment processes.The process of spray drying evaporation of desulfurization wastewater by using bypass flue gas fully utilizes the heat of boiler hot flue gas which has low investment operation cost is a zero-discharge technology for wastewater with great application prospect.In this paper,the atomization characteristics and evaporation characteristics of desulfurization wastewater are studied and analyzed by using the desulfurization wastewater atomization characteristic test system and spray drying system.The PDA was used to test the velocity and particle size distribution of the atomized desulfurization wastewater of the rotary atomizer based on the established atomization characteristic test system for desulfurization wastewater.The results show that the particle size of droplets formed by rotary atomization of desulfurization wastewater is mainly concentrated below 50?m,showing a single peak distribution.The pH value of the wastewater has no significant effect on the average particle size of the atomized droplets that is increased with the increasing of atomizer speed and the wastewater flow rate.The rotary atomizer has high adaptability to the content of suspended solids and inorganic salts in the desulfurization wastewater.The atomization particle size will increase and the atomization effect will decrease for the desulfurization wastewater with suspended solids concentration greater than 20000 mg/L and chloride ion concentration above 40000 mg/L.The droplets of the desulfurized wastewater after atomization are dried and evaporated by the spray drying system,and the particles are collected and analyzed by means of flue sampler,scanning electron microscope and thermogravimetric analyzer.The results show that the inlet flue gas temperature and wastewater flow have a significant impact on the evaporation process of desulfurization wastewater.The spray drying evaporation system has high adaptability to the chloride ion concentration in wastewater,which can be applied to the atomization evaporation treatment of high-salt wastewater with chloride ion concentration below 40,000mg/L.The large particles in the evaporation product of the desulfurization wastewater are mainly deposited by gravity in the bottom ash hopper and the small particles follow the outlet flue gas.The droplets form larger particle clusters with the fly ash particles attached to the droplets of the desulfurization wastewater during the evaporation process,resulting in a relatively larger particle size of the fly ash in the outlet flue gas,which is beneficial to the subsequent removal of the electrostatic precipitator.The effects of spray drying evaporation of desulfurization wastewater on electric ESP,WFGD,boiler thermal efficiency and resource utilization of fly ash were studied.The application of wastewater spray drying evaporation engineering application was introduced.The results show that the temperature of the flue gas is reduced and the humidity is increased by the spray drying tower,which is beneficial to improve the efficiency of ESP and WFGD,and the thermal efficiency of the boiler will decrease slightly.The chlorine content of the fly ash after doping of the evaporation product of desulfurization wastewater generally does not exceed the standard of six ten thousandths,and does not affect the resource utilization of the fly ash.The desulfurization wastewater in the spray drying tower can be well evaporated and the moisture content of the evaporated product is low when the ratio of flue gas flow to wastewater treatment is above 1.1×10~4 Nm~3/t for hot flue gas with a temperature above 300°C in engineering applications. |
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