Combined Removal of SO2, NOx, and Fly Ash from Flue Gas using Pulsed Streamer Corona

A pulse-energized electron reactor (PEER) which utilizes pulsed streamer corona has been developed for the combined removal of SO2, NOx, and particles from effluent gases. In the PEER process, fast-rising, narrow, high voltage pulses are superimposed on a dc-bias voltage and applied to a nonuniform field geometry to generate pulsed streamer corona. The pulsed streamer corona produces energetic free electrons which dissociate gas molecules, forming radicals. These radicals cause chemical reactions that convert SO2 and NOx into acid mists and/or solids which can be collected by conventional means. The pulsed streamer corona also produces ions, and between pulses the ions charge the fly ash particles which aro then collected by the dc-bias voltage. In PEER performance tests on a humid air stream with an initial SO2 concentration of 1000 ppm, more than 90% of the SO2 was removed with an advantageously small power requirement. Combined treatment performance was demonstrated by introducing high resistivity fly ash into the gas stream. The fly ash collection efficiency of the PEER was significantly better than that of a conventional dc electrostatic precipitator when the electrodes of both were covered with a high resistivity layer. Most of the fly ash which escaped collection by the PEER was agglomerated, which facilitates subsequent collection. Furthermore, the SO2 removal efficiency was improved by the presence of fly ash. The practical electrode configurations (wire-to-cylinder or wire-to-plate) and performance results of the PEER make it attractive for retrofit applications.