加压多段循环流化床固体颗粒浓度分布特性

Distribution characteristics of solid holdups in pressurized multi-stage circulating fluidized bed

针对加压煤气化的发展需要和加压多段循环流化床气化炉的研发,建立了一套加压多段循环流化床冷态试验装置.研究了0. 1,0. 3,0. 5 MPa压力下,平均粒径为400μm、密度为1 020kg/m^3的固体颗粒在循环流化床轴向和径向颗粒浓度的分布特性.实验结果表明,多段循环流化床轴向颗粒体积分数分布呈ε形分布特点,即颗粒较浓区域集中在射流流化床底部浓相段和提升管进出口位置.提升管轴向颗粒浓度分布呈现C形分布,且表观颗粒浓度随固体循环通量的增加而增加,随着表观气速的增大而减小.在相同固气比的条件下,增加系统压力可以显著提高管内颗粒浓度.颗粒浓度径向分布呈现中心区域稀,边壁区域浓的环核流动结构.增大表观气速或减小固体循环通量可以使颗粒径向分布更加均匀.另外,颗粒浓度分布在边壁区比中心区对表观气速和固体循环通量的变化更加敏感.

A cold model experimental facility of the pressurized multistage circulating fluidized bed was built for the development of pressurized coal gasification and circulating fluidized bed gasifier.The distribution characteristics of solid holdups in axial and radial directions of Geldart group B particles with the mean diameter of 400μm and the density of 1 020 kg/m^3 were studied under different pressures(0.1,0.3,and 0.5 MPa).The results show that the axial profiles of solid holdups in the multi-stage circulating fluidized bed present a typicalε,that is,the dense regions in the vicinity of the bottom of the JFB,inlet and outlet of the riser.The axial profiles of solids holdup in the riser presented a typical C,and the axial solid holdups increase with increasing the solid circulation rate and with decreasing the apparent gas velocity.At the same solids-to-gas ratio,the solid holdups increase obviously with increasing pressure.The radial distribution of solid holdups presents a large dilute region in the axis and a small dense region around the wall,called the core-annular flow structure.The radial distribution of solid holdups became more uniform with decreasing the solid circulation rate or increasing the apparent gas velocity.In addition,the change of solid holdups around the wall region is more sensitive than the central region with changing apparent gas velocity and solid flux.