Showing papers on "Packed bed published in 1978"
TL;DR: For low Peclet numbers most of the experimentally obtained particle-to-fluid heat and mass transfer coefficients in packed beds were found to be some orders of magnitude below the values predicted for a single sphere in cross flow as mentioned in this paper.
255 citations
25 Aug 1978
TL;DR: In this article, the authors present a calculational model that describes certain aspects of the in situ gasification process and predict and correlate reaction and thermal front propagation rates and product-gas composition as a function of coal bed properties and process operating conditions.
Abstract: This report presents a calculational model that describes certain aspects of the in situ gasification process The primary aim of this preliminary work was to predict and correlate reaction and thermal-front propagation rates and product-gas composition as a function of coal bed properties and process operating conditions We restricted initial efforts to a one-dimensional transient Darcy flow in a permeable packed bed The numerical calculations include a detailed description of the reacting systemchemistry (13 species), with appropriate reaction rates and overall heat and mass transport in the system A comparison of calculated results with experimental data from a packed-bed combustion tube showed good agreement for reaction-zone propagation rates and produced-gas compositions However, we believe the sensitivity of the calculations to other reaction-rate and transport-coefficient models needs to be investigated
122 citations
118 citations
TL;DR: In this paper, the existence of multiple hydrodynamic states in trickle bed reactors with small particles is investigated and it is shown that these states are characterized by significantly different pressure gradients and different liquid holdups for identical gas and liquid flowrates.
Abstract: Evidence for the existence of multiple hydrodynamic states in trickle bed reactors with small particles is produced. These states are characterized by significantly different pressure gradients and different liquid holdups for identical gas and liquid flowrates. The determining factor is the maximum gas flowrate to which the packed bed has been subjected.
84 citations
TL;DR: In this article, the axial dispersion coefficients of isobutane in air in a bench-scale column with sample withdrawal at varying heights were investigated, showing that the number of mixing cells in series decreases with particle diameter due to the increasing numbers of particles agglomerated to clusters.
73 citations
TL;DR: A multiphase caralytic packed-bed as mentioned in this paper was used in the Reppe-Buna synthesis for the first time in the early 1970s and has been used in a variety of applications, such as liquid-phase catalytic hydrocracking and brryaadiol synthesis.
Abstract: Multiphase caulytic packed-bed reactors are used in chtmid, petrocbemid, as well as in the petroleum Lndustrg for contactirrg gaseau and liquid reactaxzzs with 2 solid ucalyst. Xydrodesulfurszltion of petroleum fractions, liquid-phase catalytic hydrocracking, and brrryaadiol synthesis fmm forrmldehyde and acetylene (one of the main steps of the Reppe-Buna synthesu) am well-bwn mrrltipnase caralytic packed-bed pmcesses. Multpharse catalytic packed-oed reactom have also been used in liquid waste treazmens recemly. h the case of absoqzion followed by homogeneous catalyrlc reacsions LO the liquid phe. The Sxed bed is formed by inert packing which enables an inmnsiw mixing between the gas and liquid phases, and thus producar a large gas-liquad interface.
60 citations
TL;DR: In this paper, a one-dimensional single-phase conductivity model of packed beds in which air and rock are at the same temperature is used to develop closed-form analytical solutions for the transient responses produced by time-varying air inlet temperatures.
59 citations
TL;DR: In this paper, the fluid effective diffusion coefficients under first-order-reaction condition were calculated at zero flow rates and shown in chart as a function of fluid and intraparticle diffusivities and Thiele modulus.
43 citations
Patent•
13 Nov 1978
TL;DR: Improved liquid chromatographic apparatus and an improved process for making and utilizing a chromatogram are described in this paper. But the authors do not consider the use of column packing. And they do not address the problem of column uniformity in the context of chromatograms.
Abstract: Improved liquid chromatographic apparatus and an improved process for making and utilizing a chromatographic column. By providing means to exert radial pressure on the column packing, the packing efficiency of the column is increased and is more reproducible, and greater uniformity can be achieved in column performance both among packed columns of the same kind and during the useful life of a given packed column.
36 citations
Patent•
20 Jun 1978TL;DR: In this paper, a positive downward pressure on a packed bed of aluminum by a weighted or spring-loaded piston was used to provide improved contact between the aluminum particles with resulting improved electrical continuity.
Abstract: Heat and electrical energy are generated from aluminum by introduction of aluminum particles on demand into a reaction chamber for reaction with an aqueous electrolyte solution with the concurrent formation of aluminum hydroxide. Improved packing of the aluminum is achieved by exertion of a positive downward pressure on a packed bed of aluminum by a weighted or spring-loaded piston, the pressure providing improved contact between the aluminum particles with resulting improved electrical continuity.
34 citations
TL;DR: In this paper, the effects of changes in experimental factors influencing adsorption were investigated using both batch (agitated flask) and column (flow through packed bed) systems; solution pH and concentration, carbon particle size, carbon bed depth and flow rate were all studied.
TL;DR: In this article, the axial mixing in a 72 mm diameter mechanically agitated extraction column of the Oldshue-Rushton type has been determined in a liquid-liquid mass transfer system.
TL;DR: In this article, the performance of different types of three-phase reactors for removal of a gaseous reactant by catalytic reaction is compared in terms of the key variables affecting the fraction of sulfur dioxide reacted.
Abstract: Methods are developed for predicting the performance of different types of three-phase reactors for removal of a gaseous reactant by catalytic reaction. The removal is assumed to occur by mass transport of reactant from gas-to-liquid and liquid-to-catalyst particle and then by intraparticle diffusion and reaction in the liquid filled pores. The method is applied to the oxidation of sulfur dioxide at 25°C and 1 atm using activated carbon, in the presence of water, as a catalyst. Slurry, trickle-bed, and counterflow packed-bed reactors are compared in terms of the key variables affecting the fraction of sulfur dioxide reacted.
Patent•
17 Nov 1978
TL;DR: In this paper, a volume of particulate packing material through which a fluid is to flow, a piece of solid porous material adjacent to the surface of the packing material, and a heatshrinkable tubing which triaxially compress the packing materials into a tightly packed bed predominantly in the directions which are normal to and parallel to the direction of fluid flow through the packed bed.
Abstract: A cartridge is disclosed which comprises a volume of particulate packing material through which a fluid is to flow, a piece of solid porous material adjacent to the surface of the packing material though which the fluid is to enter the volume and a second piece of solid porous material adjacent to the surface of the packing material through which the fluid is to exit from the volume, and a heat-shrinkable tubing which triaxially compress the packing material into a tightly packed bed predominantly in the directions which are normal to and parallel to the direction of fluid flow through the packed bed and which extends beyond the pieces of solid porous material to form an inlet opening to and an outlet opening from the packed bed.
TL;DR: The theory of liquid redistribution in packed columns under the influence of a potential when the boundary conditions have been set by differences in permeability between the wall and bulk regions, has been tested in experiment as mentioned in this paper.
TL;DR: In this article, the reaction between dichloramine and activated carbon in batch and packed bed reactors has been described by a mathematical model involving pore transport and surface reaction rate as rate limiting steps.
TL;DR: In this paper, the experimental observation of preferential liquid flow is interpreted as a difference in permeability between the wall and bulk region of packing, and the existence of a potential for liquid redistribution is inferred from an examination of experimental work on two-phase flow in porous media, and of the internal consistency of the early relation between radial velocity and the radial gradient of axial velocity.
TL;DR: In this article, a random packing structure constructed by a computer simulation of the slow settling of rigid spheres into a randomly packed bed is investigated, where the bulk-mean volume fraction of the particles is 0.582.
TL;DR: In this article, the authors examined the effect of finite pressure gradients on the dispersion of a pulse of an adsorbable gaseous species as it flows through a fixed bed of adsorbing spherical particles.
TL;DR: In this paper, the molecular pair-correlation function from statistical mechanics yields a theoretical variation in local packing density which agrees with values from the simulation, similar to the short-range order of the arrangement of spheres in the interior of the random assemblage.
TL;DR: In this article, a model of the biological removal of dissolved pollutants by filtration through a packed-column has been developed, and theoretical predictions concerning porosity change, oxygen depletion and purification efficiency have been tested with a dissolved substrate: the model allows, after laboratory trials, the design and optimization of a filter.
TL;DR: In this paper, the shape of the elution curve from a packed bed with axial dispersion was computed by numerical inversion of the Laplace transformed solutions for a Dirac delta function input.
Abstract: Transient pulse diffusivity measurements were carried out in a pellet string reactor. The outer skin of the catalyst spheres was partially obstructed by contaminants, and the objective was to determine the diffusivity both in this obstructed skin and also in the unobstructed core.
Conservation equations were formulated which describe the transient diffusion process in catalyst pellets with two interconnecting regions of differing diffusivities. The shape of the elution curve from a packed bed with axial dispersion was computed by numerical inversion of the Laplace transformed solutions for a Dirac delta function input.
The calculations indicated that if an appropriate residence time is chosen, the elution curve shape should be sensitive to the differing diffusivities of the two zones in the catalyst pellets.
The experimental peak shapes were analyzed by the Fourier analysis technique and the diffusivities were extracted by the Constrained Simplex optimization routine. The results showed good resolution of the different diffusivities in the skin and the core of the catalyst pellets.
TL;DR: In this paper, a simultaneous heat and mass transfer model was applied to a binary system in a 3-in. distillation column packed with 1 4 in. Raschig rings.
01 Jan 1978
TL;DR: In this article, the use of a magnetic carboxylic acid resin in a fluidized bed has definite advantages over existing systems for dealkalization, less resin is needed and simpler plants can handle the same throughput of raw water whilst maintaining product quality.
Abstract: SUMMARY From the results observed in the treatment of a number of hard alkaline feedwaters it has been shown that the use of a magnetic carboxylic acid resin in a fluidized bed has definite advantages over existing systems for dealkalization. Less resin is needed and simpler plants can handle the same throughput of raw water whilst maintaining product quality. Plant operation is simple and truly continuous without any complex valve system or pressurized vessels. The ability of the resin to treat a turbid effluent of variable composition from a sewage treatment plant has been demonstrated. Cost analyses have suggested that for a large plant, e.g. 1 mgd, changes in reactor design will be necessary to maintain the advantages mentioned above for small scale plants. A number of alternative configurations have been considered, including stirred tank, a high voidage packed bed and an entrained reactor. The final choice depends on the scale of the application.
TL;DR: Mean drop size, fractional hold-up of dispersed phase, and axial mixing have been determined in a 72 mm dia. packed column, packed with 8 mm glass Raschig rings, using the systems toluene-acetone-water and MIBK-acetic acid-water, in an attempt to assess the effects of the solute transfer processes on column operation.
TL;DR: In this paper, the performance of a first-order reversible or irreversible reaction in an isothermal three-phase isothermal reactor is analyzed in terms of dimensionless groups of pertinent mass transfer, kinetic, and equilibrium properties, and the gas and liquid flow rates.
Abstract: Three-phase reactors involving a solid catalyst are normally used for production of product or removal of impurity. Equations are presented for these two measures of reactor performance for a first-order, reversible or irreversible reaction in an isothermal reactor. The results are presented in terms of dimensionless groups of the pertinent mass transfer, kinetic, and equilibrium (solubility) properties, and the gas and liquid flow rates. From the equations given, it is possible to predict the relative performance of concurrent (trickle bed) and countercurrent flow reactors and also the effect of mixing in the gas or liquid streams on performance.