Plug Flow Modeling of Particle Formation and Growth Combined with Plasma Chemistry in NO_x Removal by a Pulsed Corona Discharge Process

摘要

We analyzed the plasma chemistry, particle formation, and growth in the pulsed corona discharge process (PCDP) to remove No_x and investigated the effects of several process variables (initial concentrations of NO, NH_3, and H_2O and electron concentration). In the PCDP, most of NO is converted into NO_2 and, later, HNO_3, which reacts with NH_3 to form NH_4NO_3 particles. As the initial NO concentration increases or as the initial H_2O concentration and the electron concentration decrease, it takes longer reactor lengths to remove the No_x. With the increase of initial NO concentration, more NH_3 is consumed to remove the NO supplied initially and NH_3 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 suplied is all consumed. Later, the particle concentration decreases slowly because the disapearance rate of particles is slightly faster than the generation rate from the NO newly formed and the NO_2 by N_2O_5 decomposition reaction, but the standard deviation increases slowly. New particle formation stops after the NH_3 is all consumed, and the particle concentration and the standard deviation drop quickly by coagulation between aprticles, but the averate particle diameter starts to grow quickly. As the initial concentrations of NO and H_2O increase or as the electron concentration increaes, 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_3 concentration increases, the averate particle diameter starts to increase later, but paritcle concentration increases and the averate particle diameter becomers laerger by faster coagulation in the end of the reactor. The informaiton on the particle characteristics can be the basic raw materials to develop more efficient PCDP and particle collection equipments.