| With the wide application of ultra-low emission technology of thermal power,most thermal power units can meet the emission limit requirement of no more than 5mg/Nm3 dust concentration after the ultra-low emission modification.However,according to the technical characteristics of wet desulfurization mainly adopted by thermal power units in China,the exhaust gas at the tail end is over-saturated and contains a large number of micro drops and aerosols,which leads to a large number of soluble substances,such as SO42-,gypsum,C1-,NH4+ and heavy metal,Which are extremely harmful to the environment.In order to further reduce the environmental hazards of soluble pollutants in the tail gas of thermal power units,some units have installed wet electrostatic precipitator at the tail.However,according to the test report of the removal modification unit that has been implemented,the removal efficiency of the wet electrostatic precipitator is limited for the fine particles below 2?m,and the high-voltage electrostatic field in the wet environment is difficult to catch the fine particles in this size range.In this paper,the theory of heat exchange coagulation and particle collision coalescence is used to study the wet condensation technology.According to the characteristics of flue gas at the tail end of thermal power unit,a heat exchanger with high corrosion resistance and heat transfer coefficient using modified F plastics was developed.In order to further improve the efficiency of the capture of fine particulate matter by the wet high pressure electrostatic field,a special wet electrostatic precipitator cathode line was developed.Through the establishment of pilot test bench in the field of the thermal power generating unit,the performance of the condensation and wet electrostatic precipitator composite technology for the capture of fine particulate matter in the flue gas of the thermal power generating unit was studied.The results show that the heat exchanger pipe made of modified F plastics has a relatively thin wall thickness and a large heat exchange area,which can have a heat exchange efficiency related to the metal material.Besides,the material has a good anti-corrosion and anti-scaling characteristics due to its own characteristics,which fully meets the application requirements of the exhaust gas environment at the tail end of the thermal power unit.At the same time by changing the phase change heat medium velocity control,considering the technical economy of plant operation and controlling flow velocity between the gas pipe within 6 m/s and cooling water flow rate control for more than 0.4m/s,can realize condensation,water efficiency>70%,the whole device showed better fine particulate matter capture efficiency,proves that the condensation and wet electrostatic precipitator composite technology can significantly improve comprehensive efficiency of removal of particulate matter.On the basis of pilot test,the paper added a wet coagulator in a 630MW large thermal power unit wet dehumidification renovation project,and completed the design and construction of the first set of condensing wet electrical composite flue gas purification plant in China.The project uses the composite technology to make fine particulate matter in flue gas reunion grew up,and wet condensate modulator characteristic of temperature gradient field improves the wet capillary rectifying effect in addition to the entrance to the uniformity of smoke flow in,therefore the composite technology compared to conventional wet electrostatic precipitator has higher PM2.5,aerosol,SO3,soluble salt,mercury and other heavy metals removal effect,at the same time,the project realize the recycling of water?15t/h by cutting the flue gas temperature 2?,and has good water saving effect.According to the test,the collecting efficiency of the device for total dust and PM2.5 in the tail gas of the thermal power unit is higher than 80%,and that of SO3 and droplet is higher than 75%. |
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