Showing papers on "Packed bed published in 1992"

Expanded-Bed Adsorption of Proteins Using Ion-Exchangers

Abstract: The use of expanded beds of ion-exchange adsorbents for the adsorption of proteins from feedstocks containing whole cells is described. Such feedstocks can be applied to the bed without prior removal of particulate material by centrifugation or filtration, thus showing considerable potential for this approach in simplifying downstream processing flow-sheets. Stable, expanded beds can be obtained using simple equipment adapted from that used for conventional packed bed adsorption and chromatography processes. Ion-exchange adsorbents are likely to be chosen for such separations as a result of the robustness of the ion-exchange groups to cleaning and sanitization protocols. Frontal analysis involving the measurement of breakthrough curves indicates that the adsorption performance of an expanded bed is similar to that achieved when the same amount of adsorbent is used in a packed configuration at the same volumetric flow-rate. In addition, the adsorption performance of an expanded bed of a cation exc...

Modified CelliGen-packed bed bioreactors for hybridoma cell cultures.

Abstract: This study describes two packed bed bioreactor configurations which were used to culture a mouse-mouse hybridoma cell line (ATCC HB-57) which produces an IgG1 monoclonal antibody. The first configuration consists of a packed column which is continuously perfused by recirculating oxygenated media through the column. In the second configuration, the packed bed is contained within a stationary basket which is suspended in the vessel of a CelliGen™ bioreactor. In this configuration, recirculation of the oxygenated media is provided by the CelliGen Cell Lift impeller. Both configurations are packed with disk carriers made from a non-woven polyester fabric. During the steady-state phase of continuous operation, a cell density of 108 cells per cm3 of bed volume was obtained in both bioreactor configurations. The high levels of productivity (0.5 gram MAb per 1 of packed bed per day) obtained in these systems demonstrates that the culture conditions achieved in these packed bed bioreactors are excellent for the continuous propagation of hybridomas using media which contains low levels (1 %) of serum as well as serum-free media. These packed bed bioreactors allow good control of pH, dissolved oxygen and temperature. The media flows evenly over the cells and produces very low shear forces. These systems are easy to set up and operate for prolonged periods of time. The potential for scale-up using Fibra-cel carriers is enhanced due to the low pressure drop and low mass transfer resistance, which creates high void fraction approaching 90% in the packed bed.

Influence of tube and particle diameter on heat transport in packed beds

Abstract: Influence of the tube and particle diameter and shape, as well as their ratio, on the radial heat transport in packed beds has been studied. Heat transport experiments were performed with four different packings in three wall-cooled tubes, which differed in inner diameter only. Experimental values for the effective radial heat conductivity and wall heat-transfer coefficient for the pseudo-homogeneous two-dimensional model and the overall heat-transfer coefficient for the one-dimensional model are presented. Values were obtained for glass spheres, alumina cylinders, and alumina Raschig rings. The effective radial heat conductivity and wall heat-transfer coefficient can both be correlated as a linear function of the gas flow rate. The Bodenstein number for heat at fully developed turbulent flow is influenced strongly by the shape of the packing: 10.9 for glass spheres, 7.6 for alumina cylinders, and 4.2 for alumina Raschig rings. For the same packing, no significant influence is found of the tube diameter on the effective radial heat conductivity or on the wall heat-transfer coefficient. The overall heat-transfer coefficient can be described very well by the so-called lump equation, which gives the relations among the overall heat-transfer coefficient, effective radial heat conductivity, and wall heat-transfer coefficient. The lump factor, as used in the lump equation, has a best-fit experimental value of 7.4.

Continuous hydrolysis of olive oil by immobilized lipase in organic solvent

Abstract: Lipase (EC 3.1.1.3) from Candida rugosa was immobilized with DEAE-Sephadex A50, Sephadex G50, Sephadex LH-20, Amberlite IRA94, and Amberlite XAD-7. The enzyme immobilized with DEAE-Sephadex A50 was found to be most effective for continuous hydrolysis of olive oil in isooctane. For the continuous reaction, 0.2 g of dry immobilized enzyme was swollen with predetermined amount of water, and packed in a glass column reactor. When the organic solvent (Isooctane) containing olive oil substrate was co-currently fed with aqueous buffer, the two phases were evenly distributed throughout the packed bed without surfactant supplement or prior mixing of the two phases. A small amount of the surfactant (AOT) was used only in packing procedure, and no additional surfactant was necessary thereafter. Effects of initial water content of the swollen gel, buffer types, and strength were examined in the continuous reaction. Our results suggest that the operational half-life was affected by desorption of the bound enzyme. Under the conditions of 20% olive oil in isooctane and 25 mM triethanolamine buffer (pH 7.0), operational half life was 220 h at 30 degrees C. The reactor was also operable with n-hexane, but the operational stability of the immobilized enzyme in n-hexane was only half of that in isooctane. Our results indicate that various enzyme carrier having hydrophilic or amphiphilic properties could be used for two-phase continuous reaction in packed-bed column, reactor without any surfactant supply or prior dispersion of the two immiscible phases.

Removal of CO2 by Gas Absorption across a Polymeric Membrane

Abstract: For the purpose of removing carbon dioxide from flue gases a novel operation, “permabsorption”, a hybrid operation of membrane permeation and gas absorption was proposed. Permeability of a non-porous hollow-fiber (HF) membrane made of polydimethylsiloxane for PUre CO2 and O2 was obtained in this simple-operation mode, the observed values being in reasonable agreement with literature values. High permselectivity can be attained by using an appropriate absorbent liquid. In the permabsorption of CO2 using alkaline solution, the permeation rate could be expressed by a model based on membrane permeation with gas absorption. The performance of a multiple-HFs module was comparable to that of a packed column. This result implies that the permabsorption method provides the possibility of operation at lower liquid flow rate than in packed columns and, therefore, of energy-saving CO2 removal from flue gases.

Packed bed arrangement for oxidation reaction system

Abstract: The present invention relates to processes and apparatus for mixing oxidizable reactants with oxidant and oxidizing oxidizable reactants. When ammonia is used as the reactant, nitric acid can be obtained. Through using particular mixing and oxidizing arrangements, the volume of reactant oxidized can be significantly increased.

Storage and release of heat in a single spherical capsule containing phase-change material with a high melting point

Abstract: A latent-heat thermal storage system using a packed bed is one of the most attractive recovery methods of periodically generated waste heat in industrial processes. The thermal performance of the system depends largely on that of a single spherical capsule containing phase-change material (PCM). In this study, PCMs were investigated as materials to recover and store heat for the temperature range between 500 and 1100 K. Some inorganic salts and metals were selected from the point of view of higher latent heat, chemical stability, nontoxicity, inexpensiveness. Heat storage and release experiments of single capsules under the condition of predominant convective heat transfer were carried out

Improvement of activated charcoal-ammonia adsorption heat pumping/refrigeration cycles : investigation of porosity and heat/mass transfer chacteristics

Abstract: Reported in this thesis are the results of a combined theoretical and experimental study into improvements to the solid adsorption refrigeration or heat pumping cycle using the ammonia-activated charcoal pair. The three areas which have been examined are the cycle thermodynamics, the porosity characteristics of ammonia-charcoal pairs and the heat transfer through an ammonia granular charcoal packed bed. It was found through the use of advanced thermodynamic cycles utilizing multiple beds that the coefficient of performance of a refrigerator could be increased by sv 250% and the coefficient of amplification of a heat pump could be increased by co 110%. The coefficients of performance and amplification may also be increased to a lesser degree by judicious choice of the charcoal porosity characteristics. A survey of charcoal porosity characteristics revealed that the useful energy per cycle could be doubled by the correct choice of charcoal. The thermal conductivity of an ammonia granular charcoal bed was measured using a novel piece of apparatus. From the results it was decided for all practical purposes that the bed conductivity may be considered constant and equal to 0.165 W/m K. The power output of the cycle was found from modelling the dynamic desorption of a reactor using a one-dimensional finite difference model set in radial coordinates. The cycle simulations revealed that ideally the reactor should be constructed from solid charcoal shapes manufactured in such a way as to incorporate paths of enhanced conductance and be integral with the containing vessel wall.

Method of stimulating oil wells

Abstract: This invention describes a method of stimulating production from an oil well by removing solid wax deposits from a production zone. An electrical resistance heater comprised of a packed bed of spherical heating elements is lowered through the tubing on a wireline and placed adjacent to the perforations. Solvent is pumped through the heater to raise its temperature by 200° C. and then into the formation to contact wax deposits. The solid wax deposits are liquified and together with the oil and the solvent form a single liquid phase. The wax is then removed from the formation by placing the well back on production. Because the invention completely avoids the use of either water or gas, the saturation of the water and gas phases in the formation is minimized, thereby maximizing the mobility of the liquid phase containing the wax and facilitating the removal of the liquified wax from the treatment area before it reprecipitates. The packed bed heater has a large surface area and a large heat transfer coefficient, so high power rates (150 kW) can be achieved within a compact volume (6 m long × 5 cm id) without solvent degradation. By heating the solvent to a high temperature, a minimum volume of solvent is required, thereby minimizing production downtime and solvent costs. The burnout and catastrophic failure problem usually associated with resistive heaters is avoided due to the multiplicity of current paths through the packed bed.

Compressibility Effects in Packed and Open Tubular Gas and Supercritical Fluid Chromatography

Abstract: Summary The influence of the pressure drop on the efficiency and speed of analysis in packed and open tubular supercritical fluid chromatography (SFC) is described: methods previously developed to describe the effects of mobile phase compressibility on the performance of open tubular columns in SFC have been extended to packed columns. The Horvath and Lin equation has been used to elucidate the influence of variations in velocity, diffusivity, and capacity factor along the column on the overall efficiency of packed column SFC. In packed columns, in contrast with the situation in open tubular columns, because the increase in velocity is no longer compensated by an increase in diffusion coefficients, the increase in both linear velocity and capacity factor which result from a significant pressure drop cause the plate height to increase along the column. The effect of fluid decompression along the length of the column on the speed of analysis in SFC has been studied and numerical expressions derived which enable calculation of compressibility correction factors for the plate height. Both the fl and f2 correction factors remain very close to unity for acceptable pressure drops, which means that the pressure drop has virtually no effect on the number of plates generated per unit time for an unretained component. For retained species, the decompression of the mobile phase across the column causes the capacity factor to increase and hence leads to increased analysis times.

Further studies of a zinc-air cell employing a packed bed anode part II: Regeneration of zinc particles and electrolyte by fluidized bed electrodeposition

Abstract: Fluidized bed zinc electrodeposition appears to be an efficient way of regenerating zinc particles and electrolyte from the discharge products of the cell described in Part I. Using a laboratory cell, various electrode materials were examined to determine their suitability for this electrodeposition. The effects of current density and zincate concentration on the performance of the cell were determined. The lowest d.c. electrical energy consumption achieved was 1.92 kWh kg−1 of zinc at 1000 A m−2 superficial current density. The corresponding figure at 2000 A m−2 was 2.08 kWh kg−1. Combining these values with the results of Part I, the ‘roundtrip’ electrical energy efficiencies of a system employing the cell of Part I for discharge, and fluidized bed electrodeposition for recharge, are 50% and 46%, respectively.

Main Factors Affecting Static Holdup of Molten Slag in Coke-packed Bed

Abstract: Synopsis : Fundamental experiments under high temperature were carried out to clarify the dropping behavior and residual mechanism of molten slag in the lower part of blast furnace. According to the result of experiment, it was verified that residual phenomenon of molten slag in the coke-packed bed was controlled by capillarity caused by immersion wetting. Static holdup of molten slag was able to be shown by dimensionless empirical formula considering balance between static pressure and that based on immersion work. Void diameter affected the quantity of slag droplet that residued in graphite funnel, that is to say, the quasi-packed bed, and its residue was present only under critical void diameter. It is estimated that static holdup indicates almost zero under the condition that coke diameter in the deadman is more than about 20 mm.

Study on catalytic distillation processes. Part II: Simulation of catalytic distillation processes. Quasi-homogeneous and rate-based model

Abstract: The rate-based model for the design and simulation of separation processes is modified so as to be suitable for the catalytic distillation process where the column consists of three parts: a rectifying and a stripping section with trays and a packed reactive section with a specially arranged structure. The correlations given in Part I were employed for computations of mass transfer coefficients in the catalytic packing bed using the Newton-Raphson technology to solve the model equations. In order to accelerate the convergence, a better method for obtaining the initial values of iteration variables, that particularly suit this complicated problem, was advanced for the rate-based model. Using the kinetic model by Wang et al., the catalytic distillation process for the manufacture of methyl tertiary butyl ether (MTBE) was simulated. The results are in agreement with that from practice