Numerical Simulation And Experimental Research On The Distribution Of SCR Flow Field And Concentration Of Fly Ash

SCR is the most effective techniques for flue gas denitrification.With the Selective Catalytic Reduction method widely used,the problems of operation and maintenance are increasing.SCR catalysts are the main equipment of the Selective Catalytic Reduction in denitration system,usually the initial investment of 30%~50%.In the operation process,the catalysts maybe deactivation caused by physical and chemical,which brings significant economic losses.The physical deactivation of the catalyst is mainly manifested in the wear of the catalyst,the blockage of the hole,the coverage layer poisoning and sintering.The wear of the catalyst and hole plugging are common problem in the power plant.The factors influencing the wear degree of the catalyst are gas velocity,characteristics of fly ash,impact angle and the catalyst itself characteristics.In general,the flue gas flow faster the wear more serious,the impact angle greater the wear more serious.The blockage in catalyst layer can be divided into pore clogging and channel blockage,and the factors that influence the catalyst blockage include the particle size of fly ash,fly ash concentration distribution,fly ash velocity and son on.In this paper,based on the commercial software ANSYS14.0,first to a 600 MW coal-fired power plant boiler supporting SCR denitration tower as the research object,simulating and calculating the effect of velocity distribution and the angle in the surface of first catalyst,when the spacing or height of the grid rectifier is transform.Results show that grid rectifier spacing is 100 mm and height is 400 mm,the speed relative standard deviation on the above of the first catalyst is least(12.87%),speed angle less than 10° accounted for 95.35%.After rectifier grids modified,the optimization result is relative ideal,but there is a low velocity zone in the near the furnace side of SCR denitration tower,so simulating and calculating the effect of the installation height,angle,quantity of the baffle in triangular area to velocity distribution on the surface of the catalyst.The study shows that the low velocity zone of the near furnace side is disappears,when the single plate is 30° at the 1/3 of inlet height of horizontal section,and the speed relative standard deviation above the surface of initial catalyst is reduced to 7.25%.The calculated result also found that the distance between the grid rectifier and the first catalyst is positively correlated with the speed relative standard deviation above the surface catalyst.Then taking the hopper below the economizer and the whole SCR system as research objects,simulating and calculating the collection efficiency of different specifications hopper and the influence after transformation that the grid rectifier,the diversion baffle in triangle zone and the hopper on the SCR system.The results show that the distribution of flow field is similar between the SCR denitration system and SCR denitration tower;the distribution of fly ash concentration and distribution of flue gas flow are not a positive correlation;after hopper expansion,on the one hand can improve their trapping efficiency,on the other hand can optimize concentration distribution uniformity of fly ash that escape the hopper.