负压差立管内的气固两相流

GAS-SOLIDS TWO-PHASE FLOW IN STANDPIPE UNDER NEGATIVE PRESSURE GRADIENT

在8 0 0mm× 1 2 0 0 0mm流化床实验装置上对1 5 0mm× 1 1 5 0 0mm负压差立管内气固两相流的轴向压力、空隙率和气体流动特性进行了测量和分析 .立管出口无约束淹没在密相流化床内 ,颗粒质量流率范围Gs<1 2 0 0kg·m-2 ·s-1 .立管内气固两相流态有两种存在形式 ,当颗粒质量流率Gs<2 0 0～ 2 5 0kg·m-2 ·s-1 时 ,流态是稀密两相共存形式 ;当Gs>2 0 0～ 2 5 0kg·m-2 ·s-1 时 ,流态是浓相输送流态 .两种流态之间可以相互转换 ,主要取决于颗粒质量流率的变化 .影响立管内气固两相流的轴向压力、空隙率分布、气相的流动特性和气固流态存在形式的主要参数是颗粒质量流率Gs、旋风分离器入口速度Vi、下端流化床流化速度uf,质量流率Gs

This paper presents an experimental study on the axial pressure, voidage and gas flow of gas solids two phase flow in a  150 mm×11500 mm standpipe under negative pressure gradient.The outlet of standpipe is submerged in a dense fluidized bed and the maximum mass flux of solids is about 1200 kg·m -2 ·s -1 .The axial pressures, voidage and gas flow in the standpipe are affected by mass flux of solids, inlet velocity of cyclone, fluidizing velocity, mainly determined by mass flux of solids.When mass flux of solids is less than 200～250 kg·m -2 ·s -1 , there are two fluidization regimes coexisting in the standpipe,a dilute phase flow and a bottom dense phase flow The pressure is low and changes little in the dilute regime.Gas flows upward, which is fluidizing gas from the standpipe bottom.When mass flux of solids is more than 200～250 kg·m -2 ·s -1 , there is only one dense phase conveying regime in the standpipe.The pressure increases progressively from top to bottom and pressure profiles are smooth Gas flows downward, and is carried by particles The axial voidage distribution in the standpipe changes from Z shaped profile to S shaped as mass flux of solids increases.