炼化废液焚烧飞灰粒子碰撞概率影响因素研究

Investigation on impaction efficiency of ash particles derived from refining and chemical wastewater incineration

中文关键词: 碰撞概率  数值模拟  气-固两相流  余热锅炉

英文关键词: Impaction efficiency  Numerical simulation  Gas-particle two-phase flow  Heat recovery steam generator

中文摘要:

      利用CFD软件Fluent对某石化企业废液焚烧余热锅炉内换热管壁上飞灰粒子碰撞及分布情况进行数值模拟研究。采用Eulerian-Largrangian法对余热锅炉内气-固两相流问题进行求解，重点分析粒子尺寸、烟气流速、纵向管间距、横向管间距等四种因素对飞灰粒子碰撞概率的影响情况。研究结果表明，除纵向管间距之外，其余三种因素对飞灰粒子的碰撞概率影响显著。飞灰粒子碰撞概率随粒子尺寸的增大而增大，其中大尺寸粒子主要在前2排换热管束的迎风侧发生碰撞，小尺寸粒子在迎风侧和背风侧均发生碰撞，且碰撞概率分布均匀。当烟气流速增大时，飞灰粒子碰撞概率随之增大，且20 μm飞灰粒子比0.2 μm飞灰粒子对烟气流速更为敏感。随着纵向管间距的增大，飞灰粒子碰撞概率仅出现轻微的下降趋势，而随着横向管间距的增大，飞灰粒子碰撞概率下降明显。

英文摘要:

      Ash particle impact and distribution characteristics on the surfaces of heat transfer tubes in a heat recovery steam generator (HRSG) of an industrial refining and chemical wastewater incineration plant have been numerically investigated by CFD software Fluent. Eulerian-Largrangian method was applied to study gas-solid two-phase flow in the HRSG, the influences of ash particle size, flue gas velocity, longitudinal tube pitch and spanwise tube pitch on ash particle impaction efficiency were investigated in detail. Overall, all parameters played important roles in impaction efficiency of ash particles except longitudinal tube pitch. Impaction efficiency increased with the growth of ash particle size, and the results showed that large particles mainly impacted on the windward side of the first two rows of tubes, while small particles impacted on both windward and leeward sides forming a uniform distribution. Enhancing the flue gas velocity contributed more ash particles to impact on the heat transfer surfaces, moreover, 20 μm particles were much more sensitive to fluid velocity compared with 0.2 μm particles. As to spanwise tube pitch, the results indicated that it had obvious effect on decreasing the impaction efficiency with increase of spanwise tube pitch, while with the increase of longitudinal tube pitch, the impaction efficiency declined slightly.