摘要
本文考察了园环、锥斗及多孔板构件对循环流化床径向颗粒分布的影响。实验及分析表明,循环流化床中径向颗粒分布的不均匀起因于气固流动系统中的湍流不均匀因素,多孔板构件是改善径向颗粒不均匀的较好结构,合理地设计多孔板开孔方式及边缝尺寸,可使径向分布趋于均匀。本文还对多孔板的影响范围及多层构件对径向颗粒分布的影响进行了研究,结果表明,多孔板的有效影响范围相当于床径两倍的尺寸,采用多层构件可提高平均颗粒浓度。
Circulating fluidized bed, featured withbubbleless gas-solid contact, minimum gas backmixing and uniform reaction temperature, has been widely applied as efficient commercial reactors. Recent studies of hydrodynamics in circulating fluidized beds have shown that the particles distributed non-uniformly over the bed cross section, resulting in great reduction in reaction selectivity and product yield. Non-uniform radial solid distribution is considered related to gas-solid flow pattern within the circulating fluidized bed, The tendency of gas passing through the central portion of the bed leads to the macro-scale circulations of particles, where solids being lifted in dilute phase in th center and moving downward in dense phase near the wall Thus, improvement of radial solid distribution can be realized by using internals to divert he particles circulation of macro-scale to that of micro-scale in the bed. Several configurations of internals were successively conceived for investigation of their influences on radial solid distribution ina circulating fluidizedbed. The internals of different configuration tested in this work are ring, inverse cone tube and several perforated plates, All experiments were carried out in a 90mm diameter circulating fluidized bed. The solid material used in this study is FCC particle. The optical fiber probe was employed to measure the radial solid distribution. The measured radial solid distributions for different internals are compared. The results have shown the advantage of one perforated plate internal over other internals for improving the radial distribution. For ring internal, an intensified non-uniformity in radial distribution of particles was detected. For inverse cone tube. the micro-scale circulations of particles could not be established due to gas tending to flow to the wall. The experimental results are obtained by using two perforated plate internals with different buffle spacings, from which an optimal spacing of about 200mm (equivalent to twice the bed diameter) was determined. The measured radial solid distribution when four plates with a spacing of 200mm were used suggests that denser bed hold-up may be obtained by using multiple plates.
出处
《化工冶金》
CSCD
北大核心
1990年第4期296-302,共7页
关键词
循环流化床
内部构件
径向颗粒分布
Circulating fluidized bed, Internal, Improved radial distribution of particles, Non-uniformity
