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Showing papers on "Packed bed published in 1974"


Journal ArticleDOI
TL;DR: In this article, the axial effective thermal conductivity in the one-phase model and the heat transfer coefficient in the twophase model were derived without assuming that the solid and gas temperatures are equal.

207 citations


Journal ArticleDOI
TL;DR: In this article, a formulation for three-dimensional flow of fluids through packed beds having a spatially variable resistance to flow is presented, and a selection of computed results is presented for cylindrical beds where the nonuniform resistance of flow obeys axial symmetry.
Abstract: Through the statement of the Ergun equation in a vectorial form, a formulation is presented for three-dimensional flow of fluids through packed beds having a spatially variable resistance to flow. The equations were put in a form convenient for numerical solution by successive over-relaxation, and a selection of computed results is presented for cylindrical beds where the nonuniform resistance to flow obeys axial symmetry. The method outlined in the paper for calculating flow maldistribution in packed beds is thought to be a necessary first step in the representation of hot spot formation and flow nonuniformities in packed bed reactors.

83 citations


Journal ArticleDOI
TL;DR: In this paper, a single pellet string reactor (SPSR) was used to simulate a packed bed reactor, which is particularly useful for larger solid particles such as pelletized ores, and also offers a convenient laboratory method for obtaining average effective diffusion coefficients for a representative sample of large porous particles.

76 citations


Journal ArticleDOI
TL;DR: In this paper, a study was made of the cathodic deposition of copper ions from flowing dilute aqueous solutions onto a packed bed of graphite, where the electrodeposition reaction was mass transfer controlled and expressions were presented for the cathode current as a function of time, solution flow rate and bed characteristics.
Abstract: A study has been made of the cathodic deposition of copper ions from flowing dilute aqueous solutions onto a packed bed of graphite. The electrodeposition reaction is mass transfer controlled and expressions are presented for the cathodic current as a function of time, solution flow rate and bed characteristics. These have been verified from potentiostatic experiments. The cathode current efficiency is shown to approach 100% and packed bed electrodes are shown to be an effective means of extracting or removing metal ions from dilute solutions.

64 citations


Journal ArticleDOI
TL;DR: In this paper, the authors analyzed radiative transfer through a packed bed of microspheres, which combines the continuous and discontinuous models in predicting the scattering and absorption properties of packed micro-spheres.
Abstract: Radiative transfer through a packed bed of microspheres is analyzed on the basis of a new conceptual model, which combines the continuous and discontinuous models in predicting the scattering and absorption properties of packed microspheres. The basic elements of the formulation consist of the determination of the scattering diagram of a unit cell, the optical properties of a series of thin microsphere layers, and the solution of the two-flux equations. Results show a strong dependence of these radiative properties on the particle diameter and emissivity. Qualitative agreement is shown in the comparison of the predictions with existing experimental data.

60 citations


Journal ArticleDOI
TL;DR: In this paper, a packed column with concurrent upward flow has been examined and the results show greater area and liquid mass transfer coefficient values than with downward flow, while the increase of power consumption was less than proportional to the mass transfer increase.
Abstract: In a previous paper hydrodynamic conditions, interfacial areas and mass transfer coefficients in a packed tower with concurrent downward flows were measured. In this work a packed column with concurrent upward flow has been examined. The results show greater area and liquid mass transfer coefficient values than with downward flow. In concurrent upward flow the increase of power consumption was less than proportional to the mass transfer increase. The experimental data show some factors which affect the increase of area and of the liquid mass transfer coefficient. Energy correlations of mass transfer parameters were proposed.

56 citations



Journal ArticleDOI
TL;DR: In this article, a column packed with glass spheres of 3 different sizes (2.59-12.2 mm) was measured for two-phase cocurrent flow of O2-water and CO2-NaOH systems.
Abstract: Volumetric absorption coefficient (ka)lg, specific interfacial area alg and mass transfer coefficient klg were measured for two-phase cocurrent flow of O2-water and CO2-NaOH systems in a column packed with glass spheres of 3 different sizes (2.59-12.2 mm). Values of (ka)lg observed were so high as to be that can be hardly attainable in conventional gas-liquid contactors. This is due to large alg of small bubbles dispersed in liquid where alg very often exceeds the geometrical surface area of packing. Values of klg range from 2 to 8×10-4m/sec, which are comparable to that of circulating bubbles in the usual systems. The effect of superficial gas velocity on (ka)lg and alg is much greater than that in a countercurrent packed column, while the effect of liquid velocity is approximately same. A liquid-phase energy loss El per unit volume of liquid contained in a bed was newly defined as a measure of microscopic flow intensity and was used for discussion and correlation of mass transfer properties. It was found that the bubble diameter is proportional to El-2/5.

49 citations



Journal ArticleDOI
TL;DR: Packing of packing materials in a continuous-type thermal diffusion column substantially increases the separation efficiency by reducing the remixing effect as mentioned in this paper, and a significant improvement in separation over the achieved by an open column was obtained by employing a packed column with packing materials having the best value of permeability.

35 citations


Journal ArticleDOI
TL;DR: In this article, a model for adiabatic packed bed reactors with axial diffusion was developed, which includes all the intra-particle and interphase effects plus the additional effect of axial expansion.

Journal ArticleDOI
TL;DR: In this article, a model for cocurrent gas liquid flow through a packed bed is proposed for predicting pressure gradient and liquid holdup for both cocurrent upflow and downflow.

Journal ArticleDOI
TL;DR: In this paper, the effects of intraparticle flow resulting from an axial pressure gradient in a flow reactor are investigated theoretically and experimentally, and an equation which gives the effectiveness factor under the combined effects of flow and diffusion is presented and the results are compared with experiments using an ion exchange reaction.
Abstract: The effects on solid-catalyzed reaction of intraparticle flow resulting from an axial pressure gradient in a flow reactor are investigated theoretically and experimentally. First, an equation which gives the effectiveness factor under the combined effects of flow and diffusion is presented and the results are compared with experiments using an ion exchange reaction. From the analyses the large effects of intraparticle flow on reaction are proved, and it is found that a packed bed of catalyst pellets permitting intraparticle flow is the most suitable reactor for reducing reactor volume and flow resistances.


Patent
24 Jun 1974
TL;DR: In this paper, a horizontal multiple-chamber, packed column structure for adsorptive separation process is proposed, where loading and unloading of packing material is facilitated, and efficient, effective contact between the packing material and a fluid passing therethrough is provided by the configuration and placement of a fluid inlet and distributor at one end thereof and fluid collector and fluid outlet at the horizontally opposite end, each chamber also including a plurality of axially extending rods to maintain a relatively uniform packing density of packing materials in the chamber.
Abstract: A horizontal multiple-chamber, packed column structure for adsorptive separation process wherein loading and unloading of packing material is facilitated, and efficient, effective contact between the packing material and a fluid passing therethrough is provided by the configuration and placement of a fluid inlet and distributor at one end thereof and fluid collector and fluid outlet at the horizontally opposite end, each chamber also including a plurality of axially extending rods to maintain a relatively uniform packing density of packing material in the chamber.

Journal ArticleDOI
TL;DR: In this article, the axial heat and mass transfer in tubular catalytic reactors may be described by mixing-cell model and diffusion model as well, and a simple numerical and graphical analysis for mixingcell model is presented.

Journal ArticleDOI
TL;DR: In this paper, the surface area of powders packed in a diffusion tube was evaluated using the Knudsen equation for diffusional flow of gases through capillaries, together with the Kozeny concept of a packed bed of powder being similar to a bundle of narrow tortuous caillaries and the simple diffusion method gave comparable surface areas, for porous and nonporous powders, to that obtained by low temperature nitrogen adsorption.

Journal ArticleDOI
TL;DR: In this article, the authors proposed another dimensional equation for the prediction of hpa by relating it with (Gsf-Gmf) only, which can be used for predicting the packed bed formation, which is closely related with the fluid velocity employed.
Abstract: The semifluidization phenomenon can be viewed as the combination of a batch fluidized bed at the bottom and a fixed bed at the top. Such a bed can be formed by providing sufficient space for the free expansion of a fluidized bed and then arresting the escape of the particles by means of a top restraint. A semifluidized bed overcomes the disadvantages of a fluidized bed, namely back-mixing of solids, attrition of particles, erosion of surfaces, etc., and at the same time, the inherent drawbacks of a packed bed such as nonuniformity in bed temperature, channel flow, and segregation tendency are absent. Babu Rao, et al. (1965), have shown that reactors involving fast exothermic reactions can be operated with steep temperature gradients in one section and a uniform temperature in the other section, with practically no elutriation of solids and a low pressure drop. The pioneer investigators in the field of semifluidization are Fan, et al. (1959, 1961, 1963), who studied the mechanical and dynamical characteristics of semifluidized beds of single-sized particles both in liquid-solid and gassolid systems. Additional studies dealing with the various aspects of liquid-liquid semifluidization have been reported by Poddar and Dutt (1969), Roy and Sarma (1970, 1971a,b) and Sunkoori, et al. (1969). Data on gas-solid semifluidization are relatively meager, the notable work being that of Fan, et al. (1963), and Roy (1971). One important aspect in semifluidization is the prediction of the packed bed formation, which is closely related with the fluid velocity employed. Fan, et al. (1959, 1963), measured the packed bed formed in liquid-solid as well as gas-solid semifluidization. A plot of (h hs)/(h — hpa) vs. (Gsf — Gmf)/(Gt — Gmf) was given which can be used for the prediction of hpa. An alternative method suggested by the same authors consists in the prediction of hpa from bed porosity considerations. An identical equation valid for liquid-solid semifluidization was developed by Poddar and Dutt (1969). Roy and Sarma (1971a,b) modified the first approach of Fan, et al. (1963), and suggested the use of Gosf in place of Gmf. These authors proposed another dimensional equation for the prediction of hpa by relating it with (Gsf — Gosf) only. In the work of Sunkoori, et al. (1969), the ratio of the free surfaces during free and restricted fluidizations (semifluidization) was related with the fluid mass velocity and the particle size.

Journal ArticleDOI
TL;DR: In this article, the performance and efficiency of five different types of electrochemical reactors were compared, using the test reaction: Cu2+Cu − 2e, and the cell types used comprised parallel plate with forced flow, the same design packed with Netlon® and glass beads respectively between the parallel plates, a cell using mesh electrodes and lastly a packed bed type reactor.

Journal ArticleDOI
TL;DR: In this article, a model for the performance of a packed bed encapsulated enzyme reactor was developed, which includes all the resistances controlling the rate of reaction plus the effect of axial dispersion of the bulk liquid.
Abstract: A model has been developed for the performance of a packed bed encapsulated enzyme reactor which includes all the resistances controlling the rate of reaction plus the effect of axial dispersion of the bulk liquid. The method of solution to the problem is based on the application of the orthogonal collocation method to both the enzyme capsule and the bulk liquid, thereby reducing the problem into one of solving a number of simultaneous first order ordinary differential equations.

Journal ArticleDOI
TL;DR: In this article, the authors measured the interfacial area of a column packed with Raschig rings, 10 mm in diameter, by the classical sulfite oxidation method, and showed that the column behaves as a recycle differential reactor.

Journal ArticleDOI
TL;DR: In this article, a mathematical model to represent the extraction of sugar from sugar cane is described, which is based on the assumption that extraction occurs according to two parallel first-order processes, corresponding to displacement-washing and diffusional processes.

Journal ArticleDOI
TL;DR: In this article, liquid entrainment separation was studied experimentally for packed bed, knitted mesh, zigzag baffle, tube bank, and cyclone type apparatus.
Abstract: Liquid entrainment separation was studied experimentally for packed bed, knitted mesh, zigzag baffle, tube bank, and cyclone type apparatus. Primary collection efficiency data compare well with theoretical predictions but re-entrainment of the collected liquid did not agree with theoretical models. Separation efficiency, drop size, and pressure drop data are presented.


Journal ArticleDOI
TL;DR: In this article, the anodic stripping of deposited copper from a packed graphite bed is shown to be a kinetically controlled process at high anodic overpotential, and the bed can be unloaded in a few seconds to form a concentrated solution of copper sulphate suitable for further processing.
Abstract: The anodic stripping of deposited copper from a packed graphite bed is shown to be a kinetically controlled process At high anodic overpotentials the bed can be unloaded in a few seconds to form a concentrated solution of copper sulphate suitable for further processing The fractional recovery is at least 95% on a single polarization

Journal ArticleDOI
TL;DR: In this paper, an extension of Ergun's relation for Raschig packings has been investigated in a countercurrently irrigated column, where the pressure drop in the irrigated packing (ΔP/ΔZ)L,G can be expressed as a function of the pressure dropping in the dry packing ( ΔP/ ΔZ)O,GG′ for the same effective gas velocity, by the relationship ( Δ P Δ Z )L, G = ( Δ p Δ Z ),G′ (1 - βt)−n.

Journal ArticleDOI
TL;DR: In this paper, the authors developed an analogy between heat transfer and coupled heat and mass transfer and explored the effect of such departures on system behaviour by a numerical method, showing that the extended analogy method gives a fairly close representation of the system behaviour resulting from a step change in the inlet fluid state.

Journal ArticleDOI
TL;DR: In this article, a theoretical study of the regeneration of coked catalyst particles in an adiabatic packed bed reactor has been made and the effect of chemical reaction resistance on the transient temperature and concentration profiles has been investigated.

Journal ArticleDOI
TL;DR: In this paper, the current potential curves for flow of solutions containing iodide, bromide, and chloride ions through a packed-bed silver electrode are presented, and it is shown that with the proper arrangement of experimental conditions these ions may be quantitatively removed from the stream.

Patent
28 Mar 1974
TL;DR: Gas scrubber combines venturi scrubber for dust laden streams with irrigated packed column for removing noxious gases also present as discussed by the authors, the gas stream then passes at lower velocity into a scrubbing section which forms an annulus around the venturi.
Abstract: Gas scrubber combines venturi scrubber for dust laden streams with irrigated packed column for removing noxious gases also present. Gas is accelerated to 50-120 m/sec. in a central pipe or venturi. At the base, the stream must turn sharply through 180 degrees and this causes significant removal of airborne material. The gas stream then passes at lower velocity into a scrubbing section which forms an annulus around the venturi. The gas finally passes through a droplet eliminator and is thenexhausted.