Optimization Study On Rectifying Device Of SCR Reactor With Variable Cross-section Flue

Selective Catalytic Reduction (SCR) regarded as one of the most mature DeNOx technologies has been the first choice for coal fired power plant to control NOx.The flow field characteristics of SCR system play an important role in improving DeNOx efficiency. In china, variable cross-section flue is often designed at the AIG upstream because of space limitation in retrofit projects. So the study on flow optimizing flow field of SCR system with variable cross-section flue have certain project guiding significance. In this paper, the flow field of SCR system is studied in a 660MW coal fired plant. Aiming at the situation that the variable croos-section has a great influence on the flow field at the AIG upstream, the flow-uniforming devices are designed and a new design method for optimizing splitters is put forward.Firstly, the effect of porous plate at the AIG upstream on flow field of SCR system was studied using numerical simulation. The results show that installation of porous plate can improve the flow field uniformity at the AIG upstream, and the Cvv value decreasese from 37.4% to 15.4%. Then the effect of splitter installation angle varying from 56°to 76°at the variable cross-section inclined flue on flow field was investigated. The results show that Cvv value increases at first and then decreases at the AIG upstream with the installation angle increasing. It is found that the guiding effect of splitters make the velocity distribution at the two walls perform inverse trends. These two conteracting trends nullify the effect of the splitters and make the Cvv value lowest at installation angle of 64°. Howerver, the same installation angle of splitters at the variable cross-section inclined flue play a limited role in the optimization of system flow field. So in this paper, a new optimization design method using different installation angle is put forward by analyzing the trend of E coefficient. The results show that the new design can reduce the deviation of velocity near two walls at the AIG upstream to average velocity, make the Cvv value at the AIG inlet decrease from 15.4% to 12.4%, as well as make the distribution of velocity and NH3/NOx mole ratio more uniform to ensure high denitration and low NH3 slip. Furthermore, the incident angle of gas at the catalyst inlet can be improved to make the flue gas enter the catalyst layer more vertically and decrease the abrasion of catalyst. At last, the cold test was carried out and the results have a good agreement with those of numerical simulation.