循环流化床锅炉气固两相流换热研究进展

Research on heat transfer of gas-solid two-phase flow in CFB boilers

循环流化床锅炉炉内床料粒度分布较宽,气固流动属于多流态复合流动,传热过程更加复杂。分析了气固两相流在不同流态下对流换热的共性机理,总结了气固两相流动换热的影响因素、机理模型及数值模拟工作,归纳了固相对流换热、气相对流换热和辐射换热3种气固两相流传热机理的计算方法。气流速度、颗粒粒径、床层压力和温度等是影响传热的重要因素,颗粒运动特性和颗粒浓度分布对循环流化床锅炉炉内换热至关重要。在今后研究中,应针对宽筛分颗粒进一步完善现有计算模型。优化循环流化床锅炉气固两相流动换热效率,提高能源利用率,对实现碳达峰、碳中和战略目标具有重大意义。

The particle size distribution of bed materials in circulating fluidized bed(CFB)boilers is wide.Gas-solid flow,a kind of multi-fluid composite flows,is of a complicated heat-transfer process.The common heat transfer mechanism of the two-phase flow in different states is analyzed,and its influencing factors,mechanism models and numerical simulation are investigated.The calculation methods for the heat transfer mechanisms of three gas-solid two-phase flows are summarized:solid-phase flow heat transfer,gas-phase flow heat transfer and radiation heat transfer.The important influencing factors of heat transfer are air velocity,particle size,bed pressure and temperature. The particle movement characteristics and concentration distribution are crucial for the heat transfer in CFB boilers.The improvement of the current calculation model should focus on wide particle size distribution.Optimizing the heat transfer efficiency of gas-solid two-phase flow in CFB boilers can boost the energy utilization rate and facilitate the achievement of carbon peaking and carbon neutrality.