旋流筛板式气固挡板流化床内压力脉动特性

在表观气速Ug=0.04~1.14 m/s时，采用旋流筛板构型的挡板式内构件，通过对比分析旋流筛板式气固挡板流化床与自由床内流动现象、压差脉动标准偏差和压力脉动标准偏差等参数，确定了旋流筛板式气固挡板流化床能有效破碎气泡的流动与操作条件。结果表明，构件下方区域颗粒随表观气速增加而不断转移至构件上方床层，造成构件下方区域密相床层高度持续降低，该区域出现3种流动状态并直接决定构件是否能破碎气泡。当Ug<0.44 m/s时，构件下方区域密相床层料位较高，形成下部为密相床层、上部为密相与大气泡交替通过构件的鼓泡床，此时构件具有抑制气泡生长并破碎气泡的作用，全床压差脉动及压力脉动标准偏差低于相同条件下的自由床；当0.44≤Ug<0.66 m/s时，密相床层料位较低，形成下部为密相床层、上部为单一稀相的湍动床，此时构件不再直接抑制气泡生长或破碎气泡，但构件下方密相床层的存在能降低构件下方及构件上方一定高度内床层的压力脉动强度；当Ug≥0.66 m/s后，密相床层完全消失，形成气体为连续相的稀相流化状态，构件不能破碎气泡、降低床层压力和压差脉动强度。

Pressure fluctuations in a gas-solid fluidized bed with rotating sieve tray type baffles

Compared with the free bed, the gas?solid fluidized bed with rotating sieve tray type baffles has good performance in breaking the bubbles under different superficial gas velocities (Ug=0.04~1.14 m/s). The ideal operating conditions were then determined by some parameters, e.g. the flow phenomena, the standard deviation of differential pressure fluctuation and the standard deviation of pressure fluctuation. The results showed that, when the superficial gas velocity increased, the particles below the internals tended to move forward to the areas above the internals. It caused the bed height to decrease below the internals. Moreover, three flow types appeared below the internals under different superficial gas velocities. It directly determined if the internals worked in breaking bubbles. When Ug<0.44 m/s, the bed height kept high value below the internals. The bubbling fluidized bed appeared. It contained two sections: the bottom section with dense phase and the upper section with the alternant appearance of the dense phase and the large bubbles. At that time, the internals suppressed the growth of bubbles and can even break the bubbles. Compared with the free bed, the fludized bed with internals had lower standard deviation of differential pressure fluctuation and the standard deviation of pressure fluctuation. When 0.44≤Ug<0.66 m/s, the bed height became small below the internals. The turbulent fluidized-bed occurred. It included two sections: the bottom section with dense phase and the upper section with dilute phase. At that time, the internals had no direct influence on the bubbles. However, the dense phase at bottom reduced the pressure fluctuation intensity below the internals and a little above the internals. When Ug≥0.66 m/s, the turbulent fluidized-bed comprised one single section with dilute phase. The section with dense phase disappeared. The gas phase became the continuous phase below the internals. At that time, the internals had little influence on the bubbles, the bed pressure and the differential pressure fluctuation intensity.