Optimizaiton Of SCR Flue Gas Denox Sysytem And Study On Fly Ash Particle Motion In Coal-Fired Plant

NOx from coal burning is the main source of NOx air pollution. With the NOx emission standards rising in China, increasing attention has been paid to the methods of reducing NOx emission. The Selective Catalytic Reduction (SCR) technology for flue gas DeNOx has been widely applied in major power plants for its advantages such as technological maturity, high DeNOx efficiency, minimized secondary pollution, and etc.. Under the pre-condition of a determined SCR system structure and catalyst, to ensure DeNOx efficiency and reduce NH3 escape rate depends to a large extent on the uniformity of flue gas velocity distribution and NH3 concentration distribution in the catalytic layer entrance cross-section. With the devolopment of computational fluid dynamic and computer technology, SCR DeNOx system can be simulated via computational fluid dynamics software, which can provide a reference for the arrangement of guiding device, the design of Ammonia Injection Grid (AIG) and the installation of soot blower.Therefore, this simulation is of remarkable significance.In this paper, computational fluid dynamics software FLUENT is adopted as a research platform to study the object—SCR reactor from a coal fired power plant boiler flue gas DeNOx system. The research consists of three sections: firstly, the flue gas flow field of SCR reactor is simulated. Optimize the flow field through a reasonable arrangement of guide vanes so as to make the flue gas velocity deviation in entrance cross-sections of AIG and catalytic layer less than 15%, to reduce the system pressure drop , and as a result to meet the SCR system operation requirements. Secondly, the diffusion of flue gas and NH3 is simulated by species transport model. Study the influence of different-diameter orifices and differernt jet speed on NH₃ concentration distribution in the catalytic layer entrance cross-section to meet the requirement that concentration deviation is less than 5%. Consequently, the appropriate orifices diameter and jet speed can be obtained as a design reference for the optimization of AIG. Finally, by using the Lagrange one-way random model to track the fly ash particles motion trajectory, the research studies the influence of different particle diameter and Rosin-Rammler distribution on motion trajectory. Moreover, the characteristics of particle motion can provide reference for the installation of ash hopper and soot blower so as to optimize the SCR reactor.