Improvement of N0x Reduction Efficiency in High Temperature System by Aerosol Assisted Non-Thermal Plasma Technique

Abstract

Summary form only given. Disposal of NOx by the chemical reaction with radicals and ion radicals (NH2, NH, OH and H) by non-thermal plasma technique (NTPT) is mainly proceeded with the particulate process of NH4NO3 vapor via homogeneous nucleation, condensation and coagulation. In the homogeneous nucleation and condensation, the activity (=(vapor pressure)/(saturated vapor pressure)) of the vapor is the essential parameter, and it should exceed unity even for condensation. But the activity becomes small at high temperature because of increase of saturated vapor pressure at high temperature like in a diesel dynamo. On the other hand, heterogeneous nucleation, which requires much less activity, is very effective for the condensational disposal of such gases, and heterogeneous nucleation process of NH4NO3 vapors on to foreign aerosol particles adding to the system from outside should be considered as the associated process of NTPT at high temperature. Removal of NOx by the association of aerosol particles in NTPT at high temperature was examined from the viewpoint of the improvement of reduction efficiency of exhaust gas. NO standard gas was supplied from a gas cylinder and adjusted the concentration in a dilution chamber with fleshed filtered air from a compressor. N2, O2 and NH3 (O2:20%, NH3:1.0%) were also supplied from standard gas cylinders. To produce NHx radical shower, NH3 balanced with O2 diluted by N2 was passed through a corona discharger and injected into a reaction chamber. Foreign aerosol particles were generated with an electric wire heating method. The number concentration and the size distribution of the nichrome aerosol particles were measured by CNC (TSI, Model-3020) with a diffusion battery. The generated aerosols were directly transported to an inlet of a reaction chamber without any additional treatment to keep the initial characteristics of the generated particles. The reaction chamber consisting of a ceramic tubular reactor (outer diameter: 75 mm, inner diameter: 68 mm, length: 1000 mm) to avoid uncertain reaction before the reaction chamber was set at the center of an electric furnace. Temperature of the electric furnace was varied from 100 to 350degC in this series experiments. From these experiments, the efficiency of NTPT was improved more than 20% with the association of foreign aerosol particles even at higher temperature more than 350degC. Total surface of aerosol particles annexing in exhausted gases containing NOx showed strong dependence on the improvement of reduction rate of such pollutant gases with NTPT. It suggested that the removal process of NOx should be progressed under the association of annexed aerosol particles.