Elutriation of fines from fluidized bed
31 Mar 1972-Journal of Chemical Engineering of Japan (The Society of Chemical Engineers, Japan)-Vol. 5, Iss: 1, pp 51-57
TL;DR: In this article, the authors studied theoretically and experimentally the T. D. H for both continuous and batch fluidized beds, and found that the theoretical elutriation rate of fine above T.D. H, defined as Z at V = 1.01Vt, coincided fairly well with the present and reported experimental results.
Abstract: 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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TL;DR: In this paper, the entrainment of Geldart Group A powders was investigated in a 7.62 cm diameter column fluidized batchwise at velocities between 0.2 and 0.7 m s −1.
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TL;DR: In this article, a simplified theory for a bubble column is applied to understand particle circulation in the fluidized catalytic beds, and it is possible to analyze flow patterns of bubbles and emulsion.
Abstract: 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.
80 citations
TL;DR: In this article, the elutriation characteristics of widely different solids (density from 920 to 5900 kg/m 3 ) were measured in fluidized beds (up to 0.9 m in size) having high freeboard (7.5 m), using gas velocities up to 4 m/s.
80 citations
TL;DR: In this article, the elutriation of fine powders from a fluidized bed of a fine-coarse particle mixture was investigated in a transparent column with a diameter of 7.1 cm and a height of 102 cm at gas velocities from 0.3 to 0.9 m/s.
75 citations
TL;DR: A comprehensive review of the available correlations is warranted, with the goal of extracting the underlying physics giving rise to the disparities, and thereby providing insights towards an enhanced understanding of entrainment.
63 citations
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TL;DR: In this paper, the authors made a series of experiments on the quadrant nozzles with 1-in, and 2-in. steel pipes, and the results showed that the discharge coefficient for a certain quadrant nozzle, No.1-St, was determined directly yb substituting water for air flowing through the nozzle.
Abstract: The accurate measurement of air discharge at low Reynolds numbers is important in many cases for chemical engineering researches. The quadrant nozzle is recommended by Koennecke as one of the most suitable fluid meters for low Reynolds numbers, because the coefficient of discharge can be maintained constant with low Reynolds numbers.He gave the coefficient of discharge for quadrant nozzles having optimum values of the ratios r/d and m as shown in Fig. 6, as a result of his extensive experiments. However, owing to the fact that he used a steel pipe 40mm in diameter and incompressible fluid such as water or oil, it is questionable whether the results obtained by him are valid for the measurement of air flow through a pipe other than 40mm in diameter, because the effect of pipe diameter on the discharge coefficient may not be negligible. Furthermore, at present, no information is available on the expansion factors for air through quadrant nozzles.Hence, the authors made a series of experiments on the quadrant nozzles with 1-in, and 2-in. steel pipes.First, the discharge coefficient for a certain quadrant nozzle, No.1-St, was determined directly yb substituting water for air flowing through the nozzle, and the expansion factor was evaluated indirectly from tests with three air nozzles as shown in Fig. 2.Finally, others as shown in Table 1 were calibrated individually with No.1-St.From the experimental results, it may be concluded that: -i) The coefficient of discharge for quadrant nozzles increases with an increase of the ratios m and r/d, but appears to decrease when r/d exceeds a certain limiting value.ii) The agreement of the discharge coefficient with Koennecke's data is to some extent satisfactory with both the quadrant nozzles, No.1-5 and No.2-0, but the coefficient, as pointed out by Jorrisen et al., can not be maintained constant with Reynolds numbers quite as low as those asserted to have been reached by Koennecke.iii) The expansion factor for air, although under the influence of m, is almost independent of r/d.iv) The size of pipe diameter, as observed by Koennecke, affects the coefficient of discharge more or less, and at the same time changes the expansion factor.v) Values of the discharge coefficient and the expansion factor for these devices are between the values for standard orifices and those for standard nozzles under identical conditions.vi) A deviation from the prescribed values of m and r/d, which is due to the manufacturing procedure, causes changes within 0.4% in the discharge coefficient.Furthermore, another experiment was conducted as follows. Two quadrant nozzles were installed in such a manner that the flat surface of the nozzle plate might face upstream, unlike in normal installation, and the authors succeeded in determining, as the result, the values of the discharge coefficient and the expansion factor.
2 citations
TL;DR: In this paper, the authors show that 2.3 × 80 cm (6.3×80 cm) is a good size for a 6.1cm person. But,
Abstract: 内径14.1cmの装置で砂を流動化し, 軸方向の密度分布と粒径分布とを同時に測定した。流動層内の密度は, Lmfまで一定で, それから指数函数的に滅少すること, および層内の粒径分布は一定で分級は密度が極めて小さくなる最上部においく初めて始まることが見い出された。両分布の測定に加えて, 2次元装置 (6.3×80cm) で写真撮影することにより, 流動層上部における粒子の拳動を研究した。
2 citations