Study & Design Of Pulsed Discharge Reactor For SO₂ Removal From Flue Gases

The pulsed streamer discharge plasma appears to be one of potent technologies for removal of SO2 and NOx from flue gas. For decreasing the energy consumption and improving the DeSO2/NOx efficiency, the electrode configuration of the wire-plate reactor has been optimized theoretically and experimentally. The main contents and conclusions are presented as follows:1. From an engineering application point of view and on the basis of analyzing the mechanism of pulsed streamer discharge, the electric field distributions of the wire-plate reactor under different electrode configuration have been calculated and the electrode configuration has been optimized by numerical simulation. The results of numerical simulation show that the average electric field strength between the wire and plate increases with the discharge wire diameter, and the optimized wire-to-wire spacing is 0.6-1 times the wire-to-plate spacing.2. The energy utilization efficiency has been defined based on the different qualities of primary and secondary streamer. The influences of the discharge voltage, the wire-to-wire spacing, the wire-to-plate spacing, and the pulse-forming capacitance on per pulse energy, secondary streamer energy and energy utilization efficiency have been investigated at atmospheric pressure. The results show that increasing wire-to-plate spacing, decreasing discharge voltage and pulse-forming capacitance can decrease secondary streamer energy and increase energy utilization efficiency. When the optimal wire-to-wire spacing is 0.6-1 times the wire-to-plate spacing, per pulse energy increases, and the secondary streamer energy decreases.3. The overall emission intensity of the second positive system (C3∏u→B3∏g) of N2 in the pulsed streamer discharge has been successfully measured at room temperature and atmospheric pressure. The density distribution law of high-energy electrons has been obtained, which are similar to the electric field distribution in wire-plate reactor. That is, high-energy electrons mainly centralize around the discharge wires. The electrode configuration has greatinfluence on space distributions of the high-energy electrons. High-energy electron distribution will become more uniform under the optimal electrode configuration.4. The laws of pulse voltage distortion, pulse energy transmission and attenuation along discharge wire have been investigated. The results show that the pulse voltage distortion occurs in the course of transmission. Pulse width and front rise time increase with transmission distance increasing. The peak of pulse voltage decreases sharply at first, and then slowly, but at last increases at the tail of the discharge wire. Increasing voltage, pulse-forming capacitance and discharge wire diameter can improve the attenuation rate of pulse energy. The curve of the energy attenuation is linear when the length of discharge wire is less than 20m. Energy attenuation becomes quicker as discharge wire is shorter. For demonstrating the law of the energy attenuation, the emission spectroscopy of N2 (C3∏u→B3∏g) has been measured along the discharge wire. The measurement results not only validate the law of energy attenuation but also present that the discharge wire length should be less than 10m for improving the efficiency energy of discharge wire.5. The DeSO2 efficiency of the simulated flue gas with the flow rate of 200Nm3/h has been studied in order to validate the optimal electrode configuration. When the concentration of SO2 is 2000ppm the energy cost is 16.7eV/moleculeSO2(3.5Wh/Nm3), and the removal efficiency is more than 85 % under the optimal electrode configuration. On the basis of the experimental results, a pulse streamer discharge DeSO2/NOx reactor with the flow rate of flue gases of 105Nm3/h has been designed.