Elutriation of fines from gas fluidized beds of Geldart A-type powders — effect of adding superfines

Publisher Summary Flow properties of the fluidized catalyst bed (FCB) are different from those of other conventional fluidized beds. The different treatment required is very significant for research and development on fluidized catalytic beds. This chapter discusses the factors affecting the flow properties. These properties include particle size distribution, also heat and mass transfer, and mixing properties. In the FCB, the dilute phase plays an important role in advancing the catalytic reaction when reaction rates are high. This factor provides a basis for identifying the appropriate reaction model and clarifying the effect of the dilute phase on selectivity and stability. The simplified theory for a bubble column is applied to understand particle circulation in the FCB. As a result, it is possible to analyze flow patterns of bubbles and “emulsion.” This chapter considers the uses of fluidized beds for catalytic reactions, using a viewpoint quite different from studies directed toward the physical handling of solid particles or toward gas–solid noncatalytic reaction. Particle size distribution has a great effect on most aspects of fluidization. Fluid beds are usually operated in the turbulent-flow region to obtain good contact and sufficient throughput of reactant gas. The uniformity and contact efficiency of a fluid bed can be improved by immersion of a surface within the bed.

Transport Phenomena and Reaction in Fluidized Catalyst Beds

Elutriation from fluidized beds

Effect of interparticle adhesion forces on elutriation of fine powders from a fluidized bed of a binary particle mixture

Review of entrainment correlations in gas–solid fluidization

Transport Disengaging Height (T. D. H.) was studied theoretically and experimentally for both continuous and batch fluidized beds. The theoretical elutriation rate of fines above the T. D. H., Vt, was calculated by use of the Maxwell-Bolzmann energy distribution, and it showed good agreement with the experimental value for the continuous fluidized bed. The theoretical values of the T. D. H., which were defined as Z at V=1.01Vt, coincided fairly well with the present and reported experimental results. The elutriation height coefficients a were found empirically to increase with increase in particle diameter and with decrease in superficial velocity.

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Elutriation of fines from fluidized bed

ELUTRIATION OF FINES FROM FLUIDIZED BED:Study of Transport Disengaging Height

Spout region in fluidized beds similar to that in spouted beds is important for reaction, mass transfer and so on.In the present paper, the spout diameter Ds and the spout height Hm above the distributor were tested in the semicylindrical fluidized bed by changing some factors, such as the geometry of perforated plates, particle size and operating conditions.At first, an empirical correlation for Hm based on qin has been obtained in the range of U/Umf=1-7.Next, the spout formed at each hole in perforated plate is assumed to be similar to that in spouted beds.According to the assumption, a new empirical correlation for Ds and Hm in the fluidized bed has been presented by modifying the semi-empirical correlation in spouted beds.It was found that Ds and Hm increased with increase of the superficial gas velocity for U/Umf≤5, on the other hand, they were independent of the superficial gas velocity for U/Umf>5.

Perforated Plate Distributor of Fluidized Beds

Eltriation of Fines from Spouted Bed Effects of Apparatus Structure

creasing velocity as long as the superficial velocity is smaller than the terminal velocity of the particle Ut. But there are no equations for the case where U>Ut; that is, the region of transport bed. In this paper, the length of the particles bed in solidliquid spouted or fluidized bed for four kinds of particles is studied for the case where U>Ut. In this case, superficial liquid velocity U is defined as the

Isamu Tanaka

Papers

Elutriation of fines from fluidized bed

ELUTRIATION OF FINES FROM FLUIDIZED BED:Study of Transport Disengaging Height

Perforated Plate Distributor of Fluidized Beds

Eltriation of Fines from Spouted Bed Effects of Apparatus Structure

Length of particles bed in batch solid-liquid spouted and fluidized systems