The Process Optimization for SCR System at High NOx and Low Space Velocity
In the production process of acrylonitrile catalyst,due to the high temperature decomposition of ni-trate,a large number of high concentration NOx gas is produced.Selective catalytic reduction(SCR)is the re-action of reducing agent ammonia(NH3)with nitrogen oxide to produce nitrogen(N2)and water(H2O).In or-der to meet NOx emission standards,the production unit adopts the selective catalytic reduction(SCR)NOx environmental treatment process.This process uses urea[(NH2)2CO]aqueous solution pyrolysis to obtain reduc-ing agent NH3,which is safer and more environmentally friendly than using NH3 directly.Through the process condition test of SCR system of acrylonitrile catalyst production unit,the optimized process condition of re-moving high concentration NOx at low space speed was obtained.The test results show that the reaction tem-perature is controlled at 325～335℃,the inlet NOx concentration is controlled below 3000μL/L,the ammonia-nitrogen ratio is maintained at 1.1～1.4,and the space velocity is maintained at 620～700h-1(corresponding to the urea pyrolysis wind flow is 320～370m3/h).The NOx removal rate of SCR system is maintained at 95％or above and the NO2 removal rate is also maintained at a high level of about 90％.The test results have been verified by actual operation.In the observation range of this paper,the removal rate of NO can maintain a high level of more than 97％under various working conditions,and the main factor affecting the removal rate of NOx is the removal rate of NO2.
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