Numerical Analysis of DE-NOx Process from Diesel Exhaust Gases by Heterogeneous Discharge Model

Summary form only given. Non-thermal plasma applications for pollution control such as de-NO_x process are currently being investigated in various places. Some of them are experimental works, and others are 19 theoretical works of the de-NO_x process. We have been investigating methods which improve the energy efficiency of the de-NO_x process by computer simulation. So far the computer simulation works of the de-NO_x process were carried out using a homogeneous discharge model, however because the silent discharge is consisted of many micro-discharges, it is necessary to use heterogeneous discharge model. In our previous works, we developed a calculation model which takes the structure of silent discharge into account, and using the model we have analyzed the NO removal mechanism, chemical reaction passes etc. However, the model assumed that the micro-discharges move with the same speed as gas flow. In the present work, we have improved the simulation model so as to include the effect of gas flow. The newly developed simulation program is a two-dimensional model and it takes the diffusion of radicals and movement of the micro-discharge channels into consideration. This analysis does not consider the turbulence of gas flow. Using this model, we calculated the NO removal performance of the 2 cases. The first case is that channel of a pulse micro discharge moves only one direction, and the second one is that it moves in random directions. Calculation results were compared with the results of the previous works. As the results, it became evident that the NO removal efficiency and NO removal rate are improved considerably by moving the channel of micro-discharge. The reason of the efficiency improvement comes from the facts that NO formation reactions from NO₂ by O radicals decrease and ozone dissociations by electrons and excited states of oxygen decrease as well.