变径组合提升管浓相区颗粒流动特性

The Flow Characteristics of Dense Phase in Adjustable Combined Riser

在颗粒循环强度(G_s)为32.65~84.59kg/(m^2·s)、固/气比(Gs/(ρ_g·U_g))为9.22~47.95的操作条件下,对变径组合提升管浓相区颗粒流动特性进行了实验研究,并与以往高密度循环流化床和循环湍动流化床对比。结果表明,变径组合提升管浓相区各局部位置均存在上行与下行颗粒;随着无因次半径增加,局部时均固含率和颗粒返混比增加,局部颗粒速度及颗粒质量净流率则降低。当Gs/(ρg·Ug)在27~47.95范围,各截面平均固含率基本不再随其变化而变化,变径组合提升管浓相区进入高密度操作状态,对应局部时均颗粒速度和颗粒质量净流率均向上。在高密度操作下,变径组合提升管在局部流动特性上与循环湍动流化床相近,在截面平均及浓相区整体流动特性上与高密度循环流化床相近。

The flow characteristics of dense phase in adjustable combined riser with the solids flux（Gs）ranging between 32.65 and 84.59kg/（m^2·s）and solid-gas ratio（Gs/（ρg·Ug））ranging between 9.22 and 47.95 were investigated and compared with that in high density circulating fluidized bed and circulating turbulent fluidized bed in previous studies.The results showed that there all existed upward and downward particles at local position in dense phase.The local timemean solids holdup and the particle back-mixing ratio increased,while the local particle velocity and the net solids mass flux decreased with the increase of r/R.The cross-sectional averaged solids holdup remained the same when Gs/（ρg·Ug）varied from 27 to 47.95,and the corresponding local time-mean particle velocity and the net particle solids mass flux were upward.Meanwhile,the dense phase became into a high-density status,at which the local flow characteristics of dense phase were similar to that in circulating turbulent fluidized bed and the cross-sectional average flow characteristics as well as the overall flow characteristics were similar to that in high-density circulating fluidized bed.