水泥分解炉掺烧污泥NO_(x)排放特性的模拟与优化

Simulation and Optimization of NO_(x) Emission Characteristics of Co-combustion of Coal and Sludge in Cement Precalciner

本文采用CFD数值模拟,对某6000 t/d带有燃烧室的PYROCLON型水泥分解炉进行掺烧污泥NO_(x)排放研究。通过设立单烧煤粉和掺烧污泥工况对比,对煤粉和污泥在水泥分解炉内的燃烧特性进行了研究,分析了两种工况下分解炉内的温度分布、生料煅烧和出口NO_(x)排放量,在此基础上对污泥掺烧量进行优化。结果表明,分解炉掺烧污泥后能明显降低NO_(x)生成量,相对单烧煤粉工况出口NO_(x)浓度降低35.5%,同时生料分解率可达95%。保持燃料总发热值不变,随着污泥掺烧热占比的增加,出口NO_(x)浓度逐渐增大,增加幅度呈平缓到快速增加的特性。综合考虑生料的煅烧,处理污泥的经济性和NO_(x)排放量,在污泥热占比为24.97%时为最佳掺烧工况,此时出口NO_(x)浓度相对单烧煤粉工况可减少27.66%。

In this paper,a 6000 t/d pyroclon type cement precalciner with combustion chamber is used to study the NO_(x) emission of co-combustion of coal and sludge by CFD numerical simulation method.Firstly,the two working conditon that coal mono-combustion and co-combustion of coal and sludge are set up to analyze the combustion characteristics of coal and sludge in the precalciner.The temperature distribution,calcination of raw meal and NO_(x) emission at the outlet of the precalciner under the two working conditions are examined.On this basis,the mixed combustion of sludge is optimized.The results show that the NO_(x) production can be significantly reduced,compared with the coal mono-combustion condition,the NO_(x) concentration at the outlet can be reduced by 35.5%,and the decomposition rate of raw meal can reach 95%.Keeping the total calorific value of fuel unchanged,with the increase of the proportion of sludge co-firing,the NO_(x) concentration at the outlet increases gradually,and the increase range of NO_(x) concentration at the outlet is gentle at first and then rapid.Considering the calcination of raw meal and economy of sludge treatment and NO_(x) emission,it is considered that the best calcination condition is when the proportion of sludge heat is 24.97%and the NO_(x) concentration at the outlet can be reduced by 27.66%compared with the coal mono-combustion condition.