Experimental Analysis on NOx Reduction Process By Aerosol Assisted Non-Thermal Plasma

Summary form only given. Non-thermal plasma technique (NTPT) has been applied to several kinds of pollution gas disposal of large quantities. The major process of the disposal is the vapor reduction by condensation onto aerosol surface following the gas to particle conversion of pollution gas. Chang mentioned that the rate coefficient of surface reaction is much larger than that of neutral reaction, ion reaction, radical reaction and electron reaction, but it is not only due to the chemical based reduction but to the physical based condensation of the vapors. Vapor condensation onto the aerosol surface increases according to the increase of the surface concentration of aerosol particles. In this study, the NO_x/SO_x removal process in the non-thermal plasma system associated with primary and secondary aerosol particles were investigated with a time resolved tubular type chemical reactor and numerical codes for chemical reaction and flow simulation in the chamber. The effect of the associated aerosol particles was also discussed how reduction rate was affected by the change of total surface concentration. Numerical simulation was conducted regarding aerosol particles injected into the reactor to clarify the NO_x/SO_x reduction mechanisms by comparing the experimental observations with calculated results. Standard NH₃ (NH₃: 1%, N₂: 79%, O₂: 20%) gas from the cylinder was flowed into the gas discharger to be ionized or dissociated; the radical or ions flowed directly into a time resolved tubular type chemical reactor to make several kinds of chemical reaction with radical and ions for NH₄NO₃ aerosol formation. NO (NO: 1%, N₂: 99%) gas from the cylinder was diluted and flowed into the reactor. The foreign aerosol particles generated with electric wire method of nichrome were injected into the reactor from the extra inlet of the reactor. Two kinds of simu- ator, REMECH and PHOENICS, were used to clarify the NO_x reduction mechanisms by comparing the experimental observations with calculated results. From the experiments, the following were made clear: 1) reduction rate per unit time is improved dramatically with increase of injected aerosol particles, i.e., the increase of surface area for condensation of the pollution gas. 2) The coincidence of calculated results with experimental observations was not so well. It will be due to the selection sticking coefficient. The results showed that the increase of surface area of associated aerosol definitely enhanced the reduction rate of NO_x/SO_x and it was cleared that the condensation of NH₄NO₃ and (NH₄)₂SO₄ onto the surface of aerosol particles in the reactor was major removal process of the NTPT.