蜂窝状催化剂脱硝过程数值计算  

Numerical Calculation of a Honeycomb-shaped Catalyst Denitration Process

作　　者：范红梅[1] 仲兆平[1] 金保升[1] 李锋[1] 

机构地区：[1]东南大学能源与环境学院,江苏南京210096

出　　处：《热能动力工程》2007年第4期450-456,共7页Journal of Engineering for Thermal Energy and Power

基　　金：教育部新世纪优秀人才基金资助项目(NCET-05-0469)

摘　　要：对蜂窝状催化剂内部的对流、传质、化学反应过程进行分析研究。建立壁面区域的控制方程,由几何对称性及扩散平衡写出边界条件,生成自适应网格,利用有限差分法对控制方程进行离散,求壁面NO浓度分布;建立蜂窝状催化剂通道内部区域的控制方程,由几何对称性及扩散平衡写出边界条件,采用交替方向隐式(ADI)算法对控制方程进行离散;最后通过方程式联立并求解,得到对于给定温度、气流速率、一定的脱硝效率和可接受氨泄漏量的条件下最佳NH3/NO比的计算式。实例计算得出:SCR反应仅发生在靠近催化剂壁面的一薄层内,其余部分均为死区;由催化剂单个孔内NH3和NO沿轴向的浓度分布情况,得到各断面上NH3的浓度下降比NO来得快,主要由于NH3在高温下被氧化而导致的结果;由一定NO进气浓度、温度和气流速率下的最佳NH3/NO比,得出最合适的NH3给气流量与NO不是等摩尔。An analytic study was conducted of the convection,mass transfer and chemical reaction process occurring inside a honeycomb-shaped catalyst and a control equation established for the wall surface areas.Boundary conditions were written out on the basis of the geometrical symmetry and diffusion balance with self-adaptive meshes being generated.A discretization of the control equation was performed by using a finite difference method to seek a solution of NO concentration distribution on wall surfaces.Established was a control equation for the inner areas in the honeycomb-shaped catalyst passage and written out were the boundary conditions on the basis of the geometrical symmetry and diffusion balance.A discretization of the control equation was conducted by using an alternating-direction implicit (ADI) algorithm.Finally,simultaneous equations were set up and a solution was sought.Obtained was an optimum NH3/NO-ratio-based formula for a given temperature,air-flow velocity and certain denitration efficiency as well as under the condition of an acceptable ammonia leakage rate.A specific-case calculation shows that SCR (selective catalytic reduction) reaction only occurs in a thin layer close to the catalyst wall surface and the others are all dead zones.From the concentration distribution of the NH3 and NO in a catalyst single hole along the axial direction,it can be shown that the concentration of NH3 in various sections drops quicker than the concentration of NO,a result mainly caused by NH3 being oxidized at a high temperature.From the optimum NH3/NO ratio at a certain NO admission concentration,temperature and air-flow velocity,one can conclude that the most suitable NH3 gas-feeding flow rate is not equimolar with the amount of NO.

关 键 词：蜂窝状催化剂 脱硝 数值计算 

分 类 号：TK16[动力工程及工程热物理—热能工程] TQ039[化学工程]