Plug flow modeling of particle formation and growth combined with plasma chemistry in NOx removal by a pulsed corona discharge process

초록

We analyzed the plasma chemistry, particle formation, and growth in the pulsed corona discharge process (PCDP) to remove NO<inf>x</inf> and investigated the effects of several process variables (initial concentrations of NO, NH<inf>3</inf>, and H<inf>2</inf>O and electron concentration). In the PCDP, most of NO is converted into NO<inf>2</inf> and, later, HNO<inf>3</inf>, which reacts with NH<inf>3</inf> to form NH<inf>4</inf>NO<inf>3</inf> particles. As the initial NO concentration increases or as the initial H<inf>2</inf>O concentration and the electron concentration decrease, it takes longer reactor lengths to remove the NO<inf>x</inf>. With the increase of initial NO concentration, more NH<inf>3</inf> is consumed to remove the NO supplied initially and NH<inf>3</inf> disappears more quickly in the PCDP. In the beginning of the reactor, the particle concentration and the standard deviation of particle size distribution increase quickly because of fast particle formation from the NO supplied initially. The particle concentration and the standard deviation decrease in the PCDP, where the NO initially supplied is all consumed. Later, the particle concentration decreases slowly because the disappearance rate of particles is slightly faster than the generation rate from the NO newly formed and the NO<inf>2</inf> by N<inf>2</inf>O<inf>5</inf> decomposition reaction, but the standard deviation increases slowly. New particle formation stops after the NH<inf>3</inf> is all consumed, and the particle concentration and the standard deviation drop quickly by coagulation between particles, but the average particle diameter starts to grow quickly. As the initial concentrations of NO and H<inf>2</inf>O increase or as the electron concentration increases, new particle formation stops earlier in the PCDP and the average particle diameter starts to increase earlier and becomes larger and the standard deviation drops more quickly to reach an asymptotic value. As the initial NH<inf>3</inf> concentration increases, the average particle diameter starts to increase later, but particle concentration increases and the average particle diameter becomes larger by faster coagulation in the end of the reactor. The information on the particle characteristics can be the basic raw materials to develop more efficient PCDP and particle collection equipments.