Research And Application Of SCR Denitration System For Cement Kiln Flue Gas

In recent years,with the implementation of ultra-low emissions in the coal burning and power industry,the proportion of total emissions of air pollutants in the non-electricity industry has become more and more prominent.In particular,the cement industry has a huge proportion of total emissions of NOx pollutants and is facing the pressure of in-depth governance.In this paper,the application of SCR denitration technology in cement industry was studied from the technical route,key technologies and engineering applications.From the applicability of the catalyst to the flue gas working conditions,the flue gas at 280℃～350℃at the outlet of the cement kiln tail preheater C1 was selected as the denitration temperature to maximize the catalytic denitration efficiency.In order to prevent failure risks such as catalyst wear,poisoning and plugging,dust concentration in flue gas must be reduced to less than 30g/Nm~3.By comparing and analyzing various kinds of high temperature dust precipitators,high temperature electric precipitators were selected to be installed in the front section of denitrification reactor,and the integrated technical route of"high temperature electric precipitator+SCR denitrification"was developed for research.The key technology of cement SCR denitration was studied in this paper.The catalyst is 13-well honeycomb type,and the flow rate in the hole should be 5m/s～6m/s to reduce the risk of catalyst clogging.The ammonia water was sprayed directly into the inlet flue of high temperature electric precipitator.The static mixer and high temperature electric precipitator were used as the uniform distribution facilities to reduce the standard deviation of ammonia concentration to 3.29%,improve the denitration efficiency and reduce ammonia escape.The combined dust removal technology is used to remove the dust on the surface of the catalyst.The distance between the nozzle of the raking soot blower and the catalyst is 200mm～300mm,the flow rate of the compressed air on the surface of the catalyst is 35m/s～45m/s,the range of the dust removal of the acoustic soot blower is 9m～12m in the axial direction and4m-6m in the radial direction,which can effectively remove the dust on the catalyst.The purging medium of rake soot blower adopts compressed air,which is heated to 250℃through flue gas heat exchange,so as to avoid the cold and brittle effect of cold compressed air on catalyst.CFD fluid simulation technology is adopted to improve the uniformity of flow velocity and ammonia concentration,reduce the incident Angle of flue gas into catalyst and reduce the operating resistance of the system by effective diversion and air distribution measures.In this paper,the engineering application of a 5000t/d cement SCR denitration system was studied.The engineering application results show that the concentration of NOx emission can be stable<50mg/Nm~3,and the ammonia escape can be<3mg/Nm~3.Compared with the original SNCR denitration technology,NOx emission concentration decreased from 200mg/Nm~3 to less than 50mg/Nm~3,ammonia consumption decreased from 1700kg/h to 1000kg/h.