Influence Of Non-uniform Distributions Of Inlet Velocity And Reductant On SCR DeNO_x Performance

Nitrogen oxides(NO_X)pollution is serious in atmospheric environment in China and coal fired power plant is one of the important sources of NO_X emission,which is mainly controlled by selective catalytic reduction(SCR)denitrification technology.Faced on the demand for coal fired power plant flue gas ultra low emission,the effect of the velocity and the concentration non-uniform distribution on the performance of the SCR reactor was studied and provided guidance for the improvement of SCR denitrification process design method.Firstly,the flow,mass transfer and reaction models of SCR catalyst modules were established and the performance of the single channel with different parameters was obtained by numerical simulation.Then on the basis of this model,the effect of the uneven distribution of ammonia and inlet velocity of the multi channel catalyst bed under the standard conditions on the performance of SCR was studied.It is found that the distribution of ammonia and inlet velocity can increase the concentration of nitrogen oxides and the ammonia slip.And the effect of different distribution forms on the performance of denitrification is different.With the increase of the relative deviation of the distribution,the efficiency of denitrification was reduced and ammonia slip was increased and the distribution of ammonia is the most important.Reducing space velocity or improving the ratio of ammonia nitrogen can increase the denitration efficiency but improving the ratio of ammonia nitrogen may also increase the ammonia slip.On the basis of this,the method of setting the value of relative deviation of the inlet velocity and ammonia distribution to meet the demand of NO_X ultra low emission was put forward.Secondly,the effects of inlet velocity and ammonia distribution uniformity of SCR reactor under low load on the performance of SCR were studied by using the above model and algorithm.It is found that when it is under low load,the uneven distribution fitted to standard conditions exceed the emissions standard because of the flue gas cooling.To achieve ultra low emissions at low load,it isneed to reduce the average space velocity or entrance NO concentration and the later one is better.Finally,some methods of regulating the flow field and concentration field are summarized.The flow field and concentration field regulating method to meet the demand of ultra low emission is recommended.