Flow,Mass Transfer And Modeling Of Three-Phase Fluidized Beds

Three—phase fluidized—bed reactors are widely used in chemical, petrochemical, coal chemical and biochemical industries. However, a model with reliable parameters interrelating flow regimes is still lack. The main purpose of this thesis is to investigate a two-dimensional model based on the measured results of hydrodynamics and mass transfer regularities of different flow regimes in a relatively large column.In the first Chapter, an extensive literature review is given on the topics of flow regimes, phase holdups, mass transfer, mixing, heat transfer, bubble behaviors and flow models in three—phase fluidized beds. On the basis of this review it is shown that, in the past two decades, plenty of investigations on flow regimes, phase holdups, mass transfer coefficient and bubble behaviors etc. in three—phase fluidized beds have been published and reviewed, though the results are diverse. Most published results are correlations of mean value parameters over whole column regardless the flow regime where data were evaluated. On the contrary, investigations on flow regimes in a column were independent of transport parameters and were merely based on visual judgement without instrumentally characterising.Besides, those results were based on small experimental columns—most columns diameter lesser than 100 mm, part up to 200 mm and seldom over 200 mm—while flow characteristics in large columns are quite different from that in smalls.The reason causing the diversity of existing correlations for multiphase fluidized-bed systems is complicate, however, it is no doubt that the above—mentioned problems in the foregoing investigations might be essential.Flow regimes have remarkable influence on hydrodynamics and transport...