基于CFD的循环流化床锅炉二次风入口结构的改进设计

摘要

The inadequate depth of secondary air caused boiler insufficient oxygen in the furnace center and uneven flow in the Circulating Fluidized Bed (CFB). The uneven flow between the gas and solid phases not only increased the abrasion on the cooling wall but also reduced the combustion efficiency, restricting the development of large-scale CFB boiler. Aiming at the injection of secondary air in CFB boiler,the design of secondary air inlet for a 150 MW CFB boiler was improved,using Eulerian multiphase model to investigate the flow field in the furnace. The results showed that the internal gas-solid flow field was more even with new inlet and anoxic zone in the center was eliminated, with a great improvement of combustion efficiency and reduction of the abrasion on the cooling wall. The improved design also allowed secondary air enter the furnace with lower momentum which reduced the energy consumption energy cost.%由于循环流化床锅炉中二次风穿透深度不够而存在着炉膛中心供氧不足和流动不均匀的现象，这种气固流动的不均匀性不仅加重了水冷壁壁面磨损的问题，更使得燃烧效率大大降低，成为了制约循环流化床锅炉大型化发展的瓶颈。因此针对传统循环流化床锅炉二次风射流问题，本文对某150 MW循环流化床锅炉的二次风入口结构进行了改进设计，并采用欧拉双流体模型对改进前后炉内流场进行了数值模拟和对比分析。结果表明，入口改进后炉膛内部气固流场更加均匀，新的入口结构改善了中心区域“欠氧区”的存在，不仅提高了燃烧效率并可以减轻壁面的磨损程度，同时该结构下二次风以较小的动量即可达到穿透深度的要求，降低了风机的能耗，从而达到了节能的效果。