300MW燃煤锅炉SCR脱硝系统导流装置的设计优化

Design and optimization of guide vanes in a 300 MW coal-fired boiler SCR system

为优化某300 MW亚临界燃煤锅炉SCR脱硝系统,基于FLUENT6.3软件,对系统烟道及反应器区域进行了模拟分析,结果表明:无导流装置下因烟道截面变化及弯头的偏转,反应器前烟道烟气流速不均,反应器入口烟气流速标准偏差Cv高达47.1%,氨氮混合较差,氨氮比最高值可达4.08;加装设计导流装置后,流场得到显著改善,系统内烟气流速和氨氮比标准偏差均下降到15%以内,各区域内氨氮比均控制在1左右,脱硝效率由66.48%提高至89.62%,系统压降由1 155.8 Pa降低到549.2 Pa,这使得SCR系统运行的经济性得以显著提高。此外,优化后系统在不同负荷下压降及速度偏差均满足运行要求,因而该方案适用于机组的变负荷运行。

To optimize the SCR system of a 300 MW subcritical coal-fired boiler,the flow field and the reagent concentration field of the system were numerically simulated using FLUENT6. 3. Guide vanes were also designed and optimized. The results indicate that the cross-section before reactor of SCR appears velocity non-uniformity when there are no guide vanes,which results from variable cross-section and deflection in flue. The velocity deviation Cvof reactor inlet is up to 47. 1%,so the mixing of NH3 and NO is uneven,the molar ratio of NH3 to NO in local area reaches 4. 08.The guide vanes improve the flow field significantly. The standard deviations of velocity and the molar ratio of NH3 to NO are down to less than 15% when the optimized guide vanes are installed in flue. The molar ratio of NH3 to NO in all regions is controlled about 1,and the denitrification efficiency increases from 66. 48% to 89. 62%. The system pressure drop decreases from 1 155. 8 Pa to 549. 2 Pa,therefore the operation economy of the SCR system is improved greatly. The pressure drop and velocity deviation of the optimized system can meet operation requirements under different loads.