220t_h锅炉再燃改造的数值模拟

为了对锅炉进行再燃改造,借助Fluent 6.3软件平台,采用数值模拟的方法,对某电厂一台220 t/h四角切圆燃烧锅炉再燃改造前后炉内的气流场、温度场和污染物排放特性进行了分析,并对再燃区过量空气系数对再燃改造效果的影响进行了探讨。湍流模型分别采用了realizable k-εmod-el和大涡模型(LES),并对模拟结果进行了比较;LES模拟和结果与现场的实验数据进行了对比验证,包括温度场、组分场和NOx,LES数值模拟结果与实验结果吻合比较好。计算结果表明:使用再燃改造后炉膛温度分布更加均匀;再燃喷口附近形成了还原性气氛,降低了NOx浓度;当再燃区过量空气系数为0.90时,再燃效果最佳,此时炉膛出口处NOx浓度下降33.87%;LES模拟结果较realizable k-εmodel准确。

Numerical Simulation of the Reburning Modification of a 220 t/h Boiler

To perform a reburning modification of a boiler,with the help of a Fluent 6.3 software platform and by adopting a numerical simulation method,studied were the in-furnace gas flow field,temperature field and pollutant emissions characteristics before and after a reburning modification of a 220 t/h tangentially-fired boiler.Furthermore,the influence of the excess air ratio in the reburning zone on the reburning modification effectiveness was also investigated.The realizable k-ε and LES model were used as the turbulent flow model respectively and a comparison of the simulation results was conducted.A contrast and verification of the simulation results obtained by using the LES model with the on-the-spot test data were conducted,including the temperature field,component field and NOx.It has been found that the numerical simulation results obtained by using the LES model are in relatively good agreement with the test results.The calculated results show that after the reburning modification,the temperature distribution in the furnace is more uniform and a reduction atmosphere is formed around the reburning spout,leading to a drop of the NOx concentration.When the excess air ratio in the reburning zone is 0.90,the reburning effectiveness is deemed as the best one and in such a case,the NOx concentration at the outlet of the furnace will decrease by 33.87%.The simulation results obtained by using the LES model are more precise than those obtained by using the realizable k-ε model.