410t/h燃煤锅炉选择性非催化还原气液混合特性的数值研究

Numerical Study of Mixing Characteristic Between Flue and Droplet at 410t/h Coal-fired Boiler SNCR System

基于Fluent平台,对410t/h燃煤锅炉选择性非催化还原(selective non-catalytic reduction,SNCR)系统喷射的尿素溶液液滴与烟气的混合过程进行数值模拟研究,同时探讨这一混合特性对脱硝率的影响。研究发现液滴穿透距离对于大空间的气液混合和烟气脱硝有重要影响,而对于给定的喷嘴它由溶液流量和液滴粒径确定;但是由于沿喷射方向存在较大的温度梯度,所以脱硝率还决定于液滴分布的当地温度。模拟结果表明在固定氨氮摩尔比下,喷射流量增大82%,脱硝率可提高8.8%,而随液滴粒径增大则先提高后降低;漏氨量随二者的增大均呈现降低趋势。另外,还将计算结果与实验测量数据进行了对比,以保证数值研究结论的可靠性。

Numerical study of the mixing process between urea solution droplet and flue gas at 410 t/h coal-fired boiler selective non-catalytic reduction（SNCR） system was conducted based on Fluent platform, meanwhile the effect of this mixing characteristic on NOx removal efficiency was discussed. It is found that the droplet penetration length that is dependent on the liquid flow and droplet size for a given nozzle has great influence on the mixing between gas and liquid in large space, and on the NOx removal efficiency. However, due to the temperature gradient existing along the injecting direction, NOx removal efficiency also depends on the local temperature at which droplets distributed. The simulation results show that at fixed molar ratio of NH3/NO, NOx removal efficiency can improve 8.8% with the 82% increase of injection flow, and as droplet size rises it represents increasing tend followed by a slight fall. In addition, the calculation result was compared with the experimental data measured, to guarantee the reliability of the conclusion drawn from this numerical study.