中文摘要：

引言 流化床气相聚合技术具有众多的优点，在过去几十年中取得了巨大的工业成功。但是这种反应器存在着传热能力差的缺点，特别是在生产高附加值产品如双峰聚乙烯产品的过程中。因此，提高反应器的时空产率就会受到严重制约。最近，Hendrickson研究表明，结块主要发生在高度为1／4-3／4床层直径的流化床壁面处，即所谓的流型滞留区（stagnantzone），但其仅为资料分析基础上的推测。

英文摘要：

The flow pattern of a fluidized bed is a key factor for heat transfer and new reactor design. The flow pattern of the gas-solid fluidized bed was experimentally measured by a novel acoustic emission （AE） technique. The acoustic energy generated by the collision of solids particles on the reactor wall or in the local space is a reflection of the speed and frequency of collision, and consequently the flow pattern of particles. The flow pattern of polyethylene particles with the average size 460 μm in a φ 150 mm fluidized bed in the range of superficial gas velocity from 0.3 m ·s^-1 to 0.7 m·s^-1 was multi-circulation pattern with main-circulation zone, sub-circulation zone and stagnant zone. The multi-circulation flow pattern would transit to the single circulation flow pattern if superficial gas velocity exceeded 0.8 m ~ s-1 or average particle size decreased to below 365 μm. The height of stagnant zone remained unchanged with the increase of static bed height. It was also found that the type of the distributor had an evident effect on flow pattern. The single circulation flow pattern in the fluidized bed with a perforated stainless steel plate distributor would change to the multi-circulation flow pattern for the same particles and the same fluidized bed with a cone-shaped distributor. An empirical equation calculating the height of stagnant zone was presented and the experimental data could be correlated with the empirical equation with fairly good accuracy.