燃煤烟气中毫米以上的大颗粒灰会导致SCR烟气脱硝装置中的催化剂堵塞与磨损，影响SCR催化剂的使用寿命及脱硝性能。在烟道中加装拦截网装置对大颗粒灰进行拦截可有效解决该问题。目前拦截网的设计主要依赖试验测量与工程经验，缺少通用设计准则与理论依据，对其压降影响因素的探究不够深入。准确计算拦截网压降特性对于开发高效、低成本、低压降拦截装置具有重要意义。利用Ansys Fluent计算流体力学的方法构建了拦截网局部网孔附近的计算模型，探究了拦截网开孔形状、烟气流速、开孔率以及拦截网厚度等参数对拦截网压降的影响。结果表明，烟气流速和拦截网的开孔率是影响压降的主要因素：流速5～20 m/s时，压降约与流速的2次方成正比；拦截网开孔率为40%～65%时，压降约与开孔率的3次方成反比。开孔率相同时，改变网孔形状对压降影响较小。在临界尺寸相同的条件下长条形拦截网压降最小。拦截网厚度为6～18 mm时，压降随厚度呈准线性增加。基于大量模拟数据，给出了拦截网压降与各参数之间的关联公式，并进一步推导了拦截网等效多孔介质渗透率的经验表达式，为拦截网的选型设计及全尺度模拟计算提供理论依据。

The large ash particles in the flue gas from coal combustion would lead to severe blockage and wear problems of the catalyst in a selective catalytic reduction (SCR)denitrification system,which affects the service life and denitration performance of SCR catalyst. This problem can be effectively solved by installing an interception net device in the flue to intercept large particle ash. The design of interceptor mainly depends on experimental measurement and engineering experience,which lacks general design criteria and theoretical basis,and the research on influence factors of pressure drop is not deeply explored. It is of significance for developing an effective and low-cost interceptor to calculate accurately the pressure drop of the flow across the interceptor with different pore structures. The influences of pore structure,flue gas velocity,interceptor porosity and thickness on the pressure drop were investigated based on computational fluid dynamics by construct the calculation model of interceptor mesh. The simulation results show that controlling parameters on pressure drop are the flow velocity and the porosity. The pressure drop is a quadratic power function of the flow velocity within the range of 5-20 m/s and inversely proportional to the third power of the porosity when the porosity of the interception network is 40%-65%. It is also found that,given the same porosity,the pore structure has negligible effect on the pressure drop. And the strip interceptor has the minimum pressure drop under the condition of the same critical size. The pressure drop increases quasi-linearly with the thickness of interceptor increase in the range 6-18 mm. Based on a large number of simulation data,A correlation is then proposed to predict the pressure drop and the empirical expression of the equivalent porous medium permeability of the interception network is further deduced,which can be feasibly applied to full-scale CFD simulation of SCR denitrification system.

0 引言

1 研究方法

   1.1 CFD计算模型

   1.2 控制方程

2 结果与讨论

   2.1 开孔形状对压降的影响

   2.2 开孔率和烟气流速对压降的影响

   2.3 拦截网厚度对压降的影响

   2.4 压降及渗透率关联式

3 结论