| Because of the synergistic desulfurization and denitrification effect along with high efficiency dedusting,the Jingliu-type electrostatic precipitation technology based on DC corona discharges has shown some technical advantages and great development potential in the ultra-low emission renovation project of coal-fired power plants in China.The desulfurization and denitrification effect of corona discharges can be attributed to the chemical conversion processes of non-thermal plasma,and the related research on its chemical mechansim and influencing factors is still not perfect.Based on self-designed and optimized laboratory-scale flue gas purification reactor and experimental system,the effects of corona discharge voltage,initial concentrations of pollutants,flue gas flow rate and liquid-phase chemical adsorption on desulfurization and denitrification efficiency and energy utilization efficiency were studied under the excitation of negative DC power supply.The synergistic desulfurization and denitrification effect of Jingliu-type electrostatic precipitation structure was systematically verified.At the same time,a one-dimensional fluid model and a chemical kinetic model of corona discharges were constructed.The spatial and temporal evolution of flue gas purification by DC corona discharges was researched in detail by numerical simulation method,and the chemical pathways of pollutant removal under different background gas systems were defined.The experimental results show that multilayer wire mesh anode plate is superior to common carbon steel plate in power characteristics of corona discharge.The increase of discharge electrode radius leads to the increase of corona onset voltage and the decrease of maximum output power.The interaction between corona wires leads to the increase of corona onset voltage and there is an optimum value for the influence of the distance between different poles and the distance between the same poles on the maximum output power.The removal efficiency of pollutants increases with the increase of corona voltage,and the energy efficiency decreases with the increase of corona voltage;the addition of calcium carbonate adsorption slurry has obvious promotion effect on SO2 removal,but negligible effect on NO removal;the increase of relative humidity significantly promotes SO2 removal and improves its energy efficiency,while its influence on NO removal is negligible.When the two pollutants are removed simultaneously,removal of NO is inhibited to a certain extent,but SO2 removal is less affected.Pollutant removal efficiency decreases with the increase of initial concentrations and removal energy efficiency increases with the increase of initial concentrations;pollutant removal efficiency decreases with the increase of flue gas flow rate,but removal energy efficiency increases with the increase of flue gas flow rate.The results of numerical simulation show that when the radius of discharge electrode is 0.15 mm,the distance between discharge and grounding electrodes is 10 cm and the negative DC voltage is not more than 50 kV,the effective removal region of NO and SO2 in different background gas systems is not more than the radius of 1 cm around the discharge electrode;the range of 1 mm around the discharge electrode is the high electron energy region,and the active particles mainly come from this region.In NO/SO2/N2 system,SO2 has no removal effect,and the removal of NO is dominated by the reduction of N,and the removal of NO is mainly inhibited by the recombination reaction of N and O.In NO/SO2/O2/N2 system,SO2 has no removal effect,and the removal of NO is dominated by the reduction of N and the oxidation of O in the early and late stages of discharge,respectively,and the removal of NO is mainly inhibited by the reduction of NO2 by O.In NO/SO2/O2/N2/H2O/CO2 system,the reduction of N is as important as the oxidation of O for NO removal,and the removal of NO is mainly inhibited by the reduction of CO2 by N.The removal of SO2 in this system is attributed to the oxidation of OH.By comparison,oxygen-enriched systems and the addition of CO2 are not conducive to denitrification. |
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