木屑在循环流化床中的流动特性研究

研究了冷态实验条件下木屑在内径0.28m、高10m的循环流化床中的流体力学特性。着重研究了表观气速U_g=1.81～2.26m/s、循环流率G_s=0.42～0.76kg/(m~2·s)的工况下木屑在循环流化床上升管中颗粒速度与床层空隙率的轴向及径向分布特点。实验发现:循环流化床的下降管中保持足够料高是木屑实现先定循环的必要条件;颗粒在上升管中的流动为典型的环-核结构;面积平均空隙率沿床高呈现先增大再减小的现象。通过将截面按径向位置r/R=0～0.71,0.71～0.93,0.93～1.00分为3个区域,分析了环区、核区和环核过渡区各自的床层空隙率以及颗粒速度沿床高变化的特点。

STUDY OF HYDRODYNAMIC CHARACTERISTICS OF SAWDUST IN A CIRCULATING FLUIDIZED BED

Hydrodynamic characteristics of sawdust were investigated in a circulating fluidized bed (CFB) with height of 10m and inner diameter of 0.28m. Experiments were carried out to study the axial and radial distributions of particle velocity and bed voidage along the riser under the conditions of superficial velocity Ug=1.81～2.26m/s, particle circulation rate Gs=0. 42 ～ 0. 76kg/(m2·s). The results show that stable operation of the CFB can be obtained if sufficient materials are kept in the downcomer; particle flow in the riser shows a typical core-annulus structure; average bed voidage goes up first and then down along with bed height; flow characteristics along the riser of core, transition and annulus area can be obtained by dividing the cross section into three areas with r/R =0～0.71, 0.71～0.93 and 0.93～1.00.