300 MW循环流化床锅炉气固流动特性的CPFD模拟

CPFD Simulation on Gas-Solid Hydrodynamics of a 300 MW Circulating Fluidized Bed Boiler

采用计算颗粒流体力学(CPFD)的方法对300 MW循环流化床锅炉内的气固两相流体动力学参数进行全床数值模拟研究,重点分析了循环流化床锅炉炉膛以及回料阀的气固流动特性,获得固相颗粒浓度和速度场在炉膛内的分布以及固体循环流量、系统压力平衡、回料阀的运行情况等锅炉关键参数。结果表明:颗粒浓度的轴向分布呈现明显的密相区和稀相区两部分,模拟得到的轴向压力分布与实际工况吻合较好,验证了CPFD方法模拟循环流化床锅炉的准确性;锅炉回料阀内压降最大,这与床料分布相符;回料阀返料室流化程度较高,而输运室流化程度较小,呈现鼓泡床状态,气泡大都贴壁逃逸。

Gas-solid hydrodynamics of a 300 MW circulating fluidized bed(CFB)boiler was investigated by computational particle fluid dynamics(CPFD)simulation.The flow characteristics of the chamber and loop seal were analyzed in detail.Operation states and key parameters of the CFB boiler,such as the solid volume fraction distribution,velocity field,system pressure,the solid circulating rate and the operational condition of loop seal were evaluated to optimize the operation of the boiler.Results showed that the solid volume fraction distribution along the furnace height was obviously distinguished as a dense-phase zone at the bottom of boiler and a dilute-phase zone at the upper part of the boiler.The solid volume fraction and velocity field in dense-phase were influenced by the bed inventory,which was returned from the loop seal.It was found that these effects were gradually reduced along the height of CFD boiler.The pressure from simulation agreed with the results obtained in actual production,which showed that CPFD is an effective way for CFB simulation.It was noted that the pressure drop at loop seal was the maximum because of its function of the pressure balance for CFB,which was in line with the distribution of bed inventory.The solid bed inventory in recycle chamber was fluidized more intense than that in supply chamber and in supply chamber,material was steadily fluidized with the bubbles escaping along the wall.