Numerical Simulation Study On Removal Of NO By Non-equilibrium Plasma

The removal of the NO by non-equilibrium plasma belongs to the interdiscipline combining physics, chemistry and environmental engineering, the essence which impacts the NO removal lies in the micro physical and chemical reactions. It is difficult to study these courses though experiments, but it can be researched by the numerical simulation experiments. Based on different gases backgrounds, the NO removal in the simulating gases systems with the He and N2as the carrier by non-equilibrium plasma were studied through the numerical simulation in this paper. According to the mechanism and the reaction equation of the NO removal by non-equilibrium plasma, the kinetic reaction equations of the simulating gases systems were obtained, and the numerical solutions were derived. By adjusting the initial values and the reaction parameters, the courses of the micro physical and chemical reactions of the plasma were systemically studied, and the cofactors which effect the NO removal by non-equilibrium plasma based on different gases were also studied. The major course of the NO removal in each system was revealed.For the simplified simulating gas system with the He as the carrier, such as the He/NO、He/NO/O2and He/NO/O2/H2O systems, the reactions of NO converting to N2and the impactors on the NO removal were mainly studied. The results showed that the efficiency of the NO removal increased initially and then slowed down as the micro-wave output increased in the He/NO/O2/H2O system. The same result was found for the selectivity of the N2. But, for the no-water system, the micro-wave output had little impact on the NO removal. In the course of the simulation calculation, the NO removal and the selectivity of N2were obviously impacted by the O-radical and N-radical, and especially by the N· radical. Existing O· shielding N· facilitated the converting of the NO to NO2, and existing N· shielding O· facilitated the NO removal and increased the selectivity of the N2. The addition of the O2and H2O could increase the yield of NO2, but it was still lower than the production of N2. The major reaction of the NO removal in the He/NO system was reduction. The NO removal in the He/NO/O2and He/NO/O2/H2O systems included not only reduction process but also oxidation process, but the major reaction was reduction reaction and the oxidation reaction was comparably weaker. The oxidation agents were O· and·OH radicals. The effects of the oxidizing removal of the NO by the·OH radicals was verified by the addition of Fenton agents as the oxidizing agent in the liquid phase. In order to simulate the actual flue gas, the N2/NO system was selected, the impact of main features of the plasma and other factors on the NO removal were studied. The results showed that the ionized degree of the plasma and the average energy of the electrons had strong effects on the efficiency of the NO removal. The NO removal by non-equilibrium plasma was essentially determined by the initial comparable electron number density. The higher the initial comparable electron number density was, the higher the NO removal efficiency. When the initial comparable electron number density was1/2, the efficiency of the NO removal reached to97.91%; The efficiency of the NO removal was positively related to the average energy of the electrons. When the average energy of the electrons was over10eV, the efficiency of the NO removal could be over to87%, the final reaction products were mainly N2with little O2and NO2. The above result showed that the main course for the NO removal was the reduction process. With the O· radicals shielding, the efficiency of the NO removal descended from58.68%to49.75%, and the selectivity of the NO2reduced from8.86%to0. With the N· radicals shielding, the efficiency of the NO removal and the selectivity of the NO2all decreased to0, which showed that O· radical was oxidizing agent and N· was reduction agent. The removal of NO was mainly depended on the reactivity of the N·. The addition of the O2was against to the reduction environment of the NO removal and made the efficiency of the NO removal decrease.