Numerical Simulation And Optimization On Small Channel Catalyst Of SCR De-NO_x System

Compared with the high ash layout of the SCR flue gas denitrition system which was widely used in coal-fired boilers,the SCR low ash layout can effectively prevent fly ash in flue gas from poisoning,abrasing and blocking the reaction catalyst to prolong the catalyst lifetime,and the application of small channel catalyst can greatly reduce the consumption amount of catalyst.The paper analyzes the influence of structure and operation parameters on denitration performance by establishing one-dimensional model of the seclective catalytic reduction?SCR?.And a three-dimensional model of SCR reactor was established to optimize the flow field,some conclusions can be drawn as follows:?1?The SCR De-NO_x experimental system of the small channel catalyst was designed to investigate the De-NO_x performance.Combined with the flue gas parameters of laboratory scale one-dimensional pulverized coal-fired test furnace,ultra-low emission and test requirements of the catalyst,a feasible laboratory SCR denitrification scheme was designed,and a pilot test rig was built for SCR De-NO_x under low dust conditions.?2?One-dimensional model of the selective catalytic reduction?SCR?reactor was established based on Eley-Rideal kinetic mechanism and it was used to analyze the influences of different structure parameters and operating conditions on the denitration efficiency under low-dust conditions.The results show that the concentration of the reactants and the chemical reaction rate decreses along the reator axial direction.The best reaction temperature is about 610 K when the gas velocity is 4.5 m/s.Too high or too low temperature has an adverse effect on the denitration efficiency.In order to achieve the denitration efficiency of above 78%,the ammonia nitrogen molar ratio should be set at least 1.1 when the inlet NO_x concentration is 500mg/m³.However,the lower ammonia nitrogen molar ratio or flow rate is set,the easier SO₂ is oxidized.?3?Three dimensional model of the SCR De-NO_x reactor was establishedto simulate the flow field uniformity of the conventional catalyst and the small channel catalyst reactor was optimized by contrast.The results show that the pressure loss of the conventional catalyst was about 55 Pa,and the pressure loss of small channel catalyst system increases to 210 Pa under the condition that the inlet flue gas mass flow rate is 0.003396 kg/s.The flow velocity distribution in the mainstream area of flue duct is even,and there is a small reflux at the pipe outlet,and the flow field uniformity of the catalyst reactor inlet with different guide plates is improved greatly.The NH₃ concentration distribution in the small channel catalyst inlet is more symmetrical and uniform to meet the design requirements.The small channel catalyst reactor with the guide plates also needs to control the flow velocity to ensure the uniform distribution of the NH₃ concentration in the catalyst inlet.Comparing with the small channel catalyst,the flow velocity distribution in the conventional catalyst reactor is even more symmetrical,and the velocity of marginal area of the small channel catalyst is about 20%lower than that of the central area.