Study On Catalyst Denitrification Performance And Optimal Control On Spraying Ammonia Of SCR Flue Gas De-NO_x System In Coal-fired Power Plant

Nitrogen oxides are discharged from coal-fired power plants as one of the main pollutants,however,the selective catalytic reduction(SCR)denitrification technology,a high denitrification efficiency and mature technology for removing NO_X in flue gas,has been widely used in domestic coal-fired power plants at present.Therefore,it is of significance to research the denitrification performance and optimized operation of SCR.In this paper,study on the catalyst performance and optimized control on spraying ammonia of the system based on some practical SCR projects in coal-fired units was carried out,and the main results are shown as following:Combined experimental research and theoretical analysis,the effect of flue gas parameters on the De-NO_X performance of catalysts was studied.The result shows that CO2 with high concentration in oxygen enriched combustion(O2/CO2)flue gas affects the denitrification performance of catalyst,which the effect is not related to the influence of the flue gas parameters.Similarly,Moisture and oxygen in flue gas has also an impact on catalyst activity,but this effect is temporary and recoverable;The influence of catalyst regeneration on the performance of denitrification was studied with experimental method.The result shows that after disposed with different regeneration methods,inactivated sample is capable of removing poisoned element and recovering the specific area.In the simulated flue gas,catalyst activities are recovered in a different degree;XRF analysis indicates that V2O5,the active component on catalyst surface,respectively dissolves in varying degrees;In order to study the effect of boiler working load changed on the actual operation of the SCR,A 600 MW in a power plant,living in the problem of air preheater blocking as the higher rate of ammonia escape.Field ammonia-injected optimization experiments have been conducted under 600 MW condition and then a parallel experiment under 320 MW was conducted and the filed optimization result was tested.The results show that after optimizing with the field experiment,NO_X distributes much more uniformly at the inlet and outlet.With the parallel experiment done,it has been observed that the uneven distribution of NO_X at SCR outlet has not been fairly improved with the relative standard deviation ?k being quite large,the reason of which mainly lies in the obvious change of flue gas flow field at SCR inlet,distributing in an opposite trend to that under 600 MW.Finally,spraying ammonia control technology of SCR denitrification system has been optimized,using RBF neural network to establish network model which was the relationship about denitrification efficiency with unit load,flue gas flow,smoke temperature at SCR inlet,NO_X concentration on the De-NO_X import,Spray ammonia amount and so on.The optimized spraying ammonia rates were determined using MATLAB simulation experiments on the model to seek the critical point of the cost of ammonia consumption and power consumption and NO_X emissions fees under the condition that meeting the NO_X emission requirements and the minimum operating costs for SCR denitrification system.Results show that while the amount of ammonia injection is higher or lower than measured,the trend of the Denitrification cost is decreasing under the premise of meeting the NO_X emission standard.