Optimization Design And Demonstration Project On The Electric System Of The Large-scale Wet Membrane Electrostatic Precipitator

Fine particles（e.g.PM2.5）in the environment is a serious threat to the development of human beings.At present,the Coal-fired power plants are still the main source of fine particles,and electrostatic precipitators（ESPs）are widely used to treat the particles.Although,the collection efficiency of ESP for coarse particles is higher than 99.9%,but its collection efficiency for the fine particles is relative low due to the penetrating window in the range of 0.1 μm to 1.0μm.In resent years,wet electrostatic precipitators（WESPs）have been widely installed downstream of wet flue gas desulphurization（WFGD）system in coal-fired power plants to meet the requirements ultra-low emissions regulations.The WESPs are considered to be a promising measurement method,which not only can effectively control the emission of fine particulate matter,but also can synergistically capture the SO3 acid mist and Hg by employing the single approach.To reveal the effect of discharge electrode on the voltage-current characteristics and the discharge current density distribution,a small mechanism WESP test bed is firstly established in the laboratory environment.The influence of flue gas speed,electrode pipe diameter,electrode shape and arrangement on the discharge current are investigated respectively.Eventually,the relationship between the structural parameters and the discharge characteristics are determined and an optimal discharge electrode type is obtained.Considering the difference in flue gas composition between the laboratory and the field,a single-channel WESP pilot test bed was established,relying on the 1 MW active coke flue gas treatment test platform in Qufu.The emission characteristics of fine particles at the ESP outlet under different collecting electrode lengths,discharge electrode parameters,operating conditions and discharging electrodes were tested by the Electrical low pressure impactor（ELPI）.Besides,the deposition characteristics of fine particles in the ESP were also obtained,which can provide a lot of scientific experimental data for the demonstration project in Fugu.Based on the above research results,a demonstration project of wet membranes electrostatic precipitator is carried out in the second phase expansion project（2×660 MW）of Deyuan Fugu Power Plant in Shanxi Province.The On-site field tests on the number and mass concentrations of fine particles at the inlet and the outlet of WESP were performed in this coal-fired power plant.The particles removal performance and its outlet emission characteristics in WESP was analyzed.Comparing with other WESPs,the electric field strength increases by 21-27%,the uniformity of the space charge density increases by 22-29%,and the full-scale dust removal efficiency increases by 7-9%;the particulate matter mass is less than 1 mg/Nm3.The overall investment is saved by more than 6.53 million yuan,especially the weight of the WESP system is reduced by about 350 tons,and the WESP saves more than 25%of materials.