Terukatsu Miyauchi

Axial dispersion in packed beds

Abstract Behaviour of axial dispersion in packed beds is made clear from the properties of the equation of continuity. New dispersion data are added to relate liquid data with gas data in the Stokes flow regime. A special device to send a plane impulse of tracer liquor was developed. A correlation has been given for a wide range of flow and dispersion in packed beds.

Transport Phenomena and Reaction in Fluidized Catalyst Beds

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.

Radioactive Rare Gas Separation Using a Separation Cell with Two Kinds of Membrane Differing in Gas Permeability Tendency

A separation cell embodying two kinds of membrane—porous and nonporous, i.e. differing in gas permeability—has a separation factor higher than possible with a conventional separation cell with a single kind of membrane. The performance of such separation cells and of cascades constituted thereof are analyzed theoretically and measured experimentally for different conditions of operation, to determine the applicability of the concept to the separation of rare gases from gaseous waste out of nuclear plants. Theoretical considerations indicate that, in a cascade composed of symmetric separation cells, the separation performance can be improved by recycling part of the effluent from a cell back through the same cell (recycling cascade). It is shown that its performance is better than with the arrangement of diverting another effluent several stages upstream. With the recycling cascade, the symmetric separation recycling rate is determined by the depletion separation and enrichment separation factors relevant ...

Gas film coefficient of mass transfer in low Péclet number region for sphere packed beds

Abstract The limiting Sherwood number between particles and fluid in the low Peclet number region has been determined experimentally for gas phase mass transfer in packed beds. A value of Sh ho = 8·33 (or Sh po = 12·5 at ϵ f = 0·50), was found where Sh po and Sh ho are the Sherwood numbers based on the particle diameter and the hydraulic diameter respectively and ϵ f is the void fraction of the beds. A high accuracy of measurement was obtained by applying a pulse response of CO 2 tracer gas to determine the film coefficients.

Mass transfer in a liquid—liquid laminar jet

Abstract Rates of mass transfer in a liquid—liquid laminar jet for three component systems have been measured. The velocity at the liquid—liquid interface has also been measured to obtain the actual contact time. Except for a short jet where the end effect of the film of surface active agent (polyethylene glycol) is considered to appear, results are well explained by the theory and thus the interfacial resistance of appreciable order does not exist in these experiments.

Limiting Sherwood number of sphere packed beds by electrical method

Abstract An electrical method which applies the analogy between electric field and molecular diffusion has been utilized to measure the limiting Sherwood number of packed bed at zero flow rate. This limiting value appropriate to usual mass transfer operations is found 9·40 when expressed in terms of the hydraulic diameter and the area averaged mean concentration driving force. When the influence of velocity profile on the film coefficient is corrected, this Sherwood number compares favourably with the previously reported value of 7·87 which is based on the hydraulic diameter and the cup-mixing mean concentration driving force.

Relative Contribution of Axial Dispersion on the Performance if Liquid Extraction Columns

ABSTRACT Terukatsu Miyauchi, 1990. Relative contribution of axial dispersion on the performance of liquid extraction columns Early development has been reviewed for the theories and modelling to evaluate the effect of axial dispersion on the performance of solvent extraction columns. These include the diffusion model, the backflow model and the convective model. The concept of equilibrium dispersion model is extended. Possible future approaches have been discussed.

Influence of Compaction in Gel-Immobilized Enzyme Packed Bed Reactors

Enzymes have been immobilized mostly on organic carriers, which may suffer from compaction when utilized in packed columns. Although packed columns are the most effective reactors, due to ideal flow characteristics, contact will be decreased significantly by compaction. Therefore, it is important to know the effect of compaction on enzymatic packed bed reactor design. The salient effect of compaction on conversion or on selectivity has been pointed out in practical use; but it has never been investigated from an engineering viewpoint.

On the Mechanisms of Nucleate Boiling Heat Transfer

大気圧付近で比較的低い熱負荷 (q≦2×105kcal/m2hr) の核沸騰伝熱機構の研究を行なった。まず, 白金伝熱面を用い, 沸騰伝熱係数の測定と同時に伝熱境膜の物質移動係数を拡散電流法により測定して, その比較から伝熱の律速段階は液境膜にあることを知った。次に伝熱機構について考察し, 伝熱面上の発生蒸気泡によって誘起される液膜の強制振動に基づいて, 沸騰伝熱係数の解析とデータの相関を行ない, Eq.(25) をえた。

On Activity Coefficient of Binary Vapour-liquid Equilibrium

argulesの式は活量係数対組成の関係が極値を持つ場合でも表わせるが, van Laarの式はそのような場合には表わせない。このことを簡単に数学的に示した。またMargulesの式の定数間の関係において, 極値をもつようになる領域を示した。