Research On SCR Ammonia Uniformity And Optimization Of Flow Field

The problem of nitrogen oxide pollution has received more and more attention.As a pillar industry in the current stage of the energy industry and even for the future,coal-fired power plants are one of the main sources of nitrogen oxides.Although the nitrogen oxide control technology of coal-fired power plants with SCR denitrification and low nitrogen combustion is rich in various types and widely used,in practice,there are still many problems such as uneven distribution of ammonia,serious ash blockage,and denitration efficiency lower than the theoretical value.In this paper,the ammonia injection grid in a SCR reactor and the SCR reaction system of a power plant are taken as research objects respectively.The numerical simulation and the problems existing in the actual operation are used to analyze the ammonia-flowing grid and the internal flow-conversion rectifier of the reactor.In this paper,through numerical simulation method,the problem of uneven ammonia injection from different nozzles of general ammonia spray grid is obtained.According to the flow path of ammonia-air mixture in the ammonia spray grid,the cause of this problem is deeply explored and targeted optimization is carried out.The research results show that the ammonia injection amount of each nozzle can be effectively balanced by adjusting the bottom diameter of the nozzle outside the ammonia spray grid,and the method has strong stability and remarkable optimization effect under consideration of other factors.After the expansion of the study,it was found that there is an optimal ammonia spray bottom diameter for the ammonia spray grids with different nozzle branch ratios to ensure the balanced spray speed of each nozzle.Combined with the actual operation feedback and computer simulation results,the problem of uneven flow velocity distribution in the prototype SCR reactor and serious ash accumulation at the rectifier grid are analyzed.Studies have shown that the baffles in the triangular region are irreplaceable for the uniformity of the velocity field in the reactor.The highly gradual rectifying grid with the baffle can make the velocity flow field reach the standard.For the simulation study of the fly ash trajectory,it is found that a large amount of large particle fly ash is concentrated in the low speed region at the near corner side of the rectifying grid due to inertia,which causes severe ash blockage.By locally widening the rectifying grid and setting the fly,the gray angle can effectively alleviate the deposition phenomenon of fly ash,and the modified width of the rectifying grid and the height of the fly ash angle will have a certain negative impact on the speed field.Modification within a certain range can achieve the speed field uniformity while minimizing the problem of ash accumulation.