Showing papers on "Packed bed published in 1990"

Rate-controlled separations

Abstract: Preface. 1. Introduction. Part I: Crystallization. 2. Crystallization and Precipitation from Solution - Equilibrium Analysis. 3. Nucleation and Crystal Growth. 4. Population Balances and Crystal Size Distributions. 5. Crystallization from the Melt. Part II: Sorption and Chromatography. 6. Basics of Sorption in Packed Columns. 7. Linear Theories of Sorption and Chromatography. 8. Non-Linear Theories and Packed Bed Adsorption Systems. 9. Ion Exchange. 10. Moving Bed and Simulated Moving Bed Sorption Separations. 11. Electrophoretic Separation Methods. Part III: Membranes. 12. Introduction to Membrane Separations. 13. Detailed Theories for Membrane Separations. Part IV: Selection and Sequencing. 14. Selection and Sequencing of Separations. Appendix: Answers to Selected Problems. Index.

Immobilization and characterization of β‐galactosidase in thermally reversible hydrogel beads

Abstract: Beta-Galactosidase has been immobilized within thermally reversible hydrogel beads and has been studied in batch and packed bed reactor systems. The enzyme was entrapped in a copolymer hydrogel of N-isopropylacrylamide (NIPAAm) and acrylamide (AAm) as beads were formed in an inverse suspension polymerization. A reversible deswelling and reswelling of the hydrogel matrix was induced by first warming and then cooling through 37-40 degrees C, which is the lower critical solution temperature, LCST, of the backbone copolymer. The optimum temperature for maximum activity of the immobilized enzyme-gel bead system was found to be 30-35 degrees C in a batch mode and 40 degrees C in a packed bed reactor, which were both below the 50 degrees C optimum for the free enzyme. These differences are understandable, since the mass transfer rates of substrate and product within the pores of the gel matrix are controlled mainly by the temperature, so therefore it is the temperature which governs the overall activity of the immobilized enzyme system. It was also found that when the operational temperature in the packed bed reactor was cycled between temperatures below (35 degrees C) and above (45 degrees C) the copolymer gel LCST, the activity of the immobilized enzyme almost fully recovered after each cycle. In fact, the enzyme-gel system exhibited a complete "shut-off" in activity at 50 degrees C which was the temperature where the free enzyme showed its maximum activity. The thermal cycling operation of LCST enzyme-gel beads can be used to enhance overall activity and productivity of a packed bed reactor, when compared to isothermal operation of this reactor. This is due to the thermally induced "pumping" which enhances mass transfer rates of substrate in and product out of the gel beads.

Hydrolysis of Methyl Acetate in Distillation Column Packed with Reactive Packing of Ion Exchange Resin

Abstract: Ion exchange resin tablets (7 mm diameter × 7 mm length) were molded from ion exchange resin beads and polyethylene powder in a furnace. 700 ml of the tablets was packed in a Pyrex glass tube of 36 mm diameter as a reaction zone and an Oldershaw column of 30 plates and 32 mm in diameter was employed as the recovery zone of the column. A mixture of methyl acetate and methanol (75:25 by weight) was fed to the bottom of the reaction zone at a rate of 89 g/h and water was fed to the top of the column at a rate of 89 g/h. When all the condensed top vapor was recycled at a rate of 254 g/h, the concentration of methyl acetate in the resulting reaction mixture discharged from the bottom was practically negligible.The reactive distillation column can be incorporated into the process of hydrolysis of methyl acetate for recovery of acetic acid and methyl alcohol. The advantages of the new process are the elimination of two columns in the conventional process and reduction of the heat requirement of the total process. The decrease in heat requirement is estimated to be about 50% that of the conventional process.

Distillation columns containing structured packing

Abstract: Presentation de methodes pour l'evaluation et la prediction de la capacite d'engorgement, de la perte de charge et du transfert de masse dans les lits a garnissage structure. Etude limitee aux geometries d'elements metalliques ondules tels que Intalox, Gempak, Flexipac, Mellapak, Sulzer et Montz

Method and apparatus for an on-stream particle replacement system for countercurrent contact of a gas and liquid feed stream with a packed bed

Abstract: This invention makes possible substantially continuous flow of uniformly distributed hydrogen and hydrocarbon liquid across a densely packed catalyst bed to fill substantially the entire volume of a reactor vessel by introducing the fluids as alternate annular rings of gas and liquid at a rate insufficient to levitate the bed and with catalyst selected by a density, shape and size at a design feed rate of liquids and gas to prevent ebulation of the packed bed at the design feed rates. Catalysts are selected by measuring bed expansion in a large pilot plant run with hydrocarbon, hydrogen, and catalyst at the design pressures and flow velocities. The liquid and gas components of the feed flow into the bed in alternate annular rings across the full area of the bed. At the desired flow rate, such catalyst continually flows in a plug-like manner downwardly through the vessel by introducing fresh catalyst at the top of the bed by laminarly flowing such catalyst in a liquid stream on a periodic or semicontinuous basis. Catalyst is similarly removed by laminarly flowing catalyst particles in a liquid stream out of the bottom of the bed. Intake for such flow is out of direct contact with the stream of gas flowing through the bed and the flow path is substantially constant in cross-sectional area and greater in diameter by several times than the diameter of the catalyst particles.

An investigation of a latent heat storage porous bed and condensing flow through it

Abstract: In this work the transient analysis of the behavior of a packed bed of encapsulated phase change material (PCM) and the condensing flow through it is presented. The rigorous model used assumes no local thermal equilibrium between the bed particles and working fluid, and incorporates the inertia effects int eh momentum transport by the use of the Ergun-Forchheimer equation. Condensation in the working fluid is investigated. Thermal charging of the packed bed is analyzed and compared for a sensible heat storage material as well as for different latent heat storage materials (PCMs).

Residence time distribution and hold-up in a cocurrent upflow packed bed reactor at elevated pressure

Abstract: The residence time distribution in liquid phase was measured in a cocurrent upflow packed bed reactor for the system methanol-hydrogen at low Reynolds numbers and at elevated pressure. The plug flow with axial dispersion model was used to describe mixing in the system. The imperfect pulse method was used to measure the system response to a tracer pulse input. The parameters were calculated using the weighted moments method. The influence of the weighting factor was investigated. The experimental and theoretical outputs, as calculated by convolution, agreed very well. Different types of correlations were used for the Bodenstein number and liquid hold-up. From these correlations, the optimal one was selected for each parameter. A comparison was made between the ordinary moments and the weighted moments methods which led to the conclusion that the latter method is superior with respect to the accuracy of the estimated parameters and therefore strongly recommended.

Simultaneous deactivation and coating of porous silica particles for microcolumn supercritical fluid chromatography

Abstract: A new method for the simultaneous deactivation and coating of porous silica particles for supercritical fluid chromatography (SFC) has been developed. This method is based on a dehydrocondensation reaction between polymeric silicon hydride reagents and the silanol groups on the surface of the particles. The procedure produces a less active surface than conventional silica packings, which results in less adsorption and improved peak shapes for polar analytes. In SFC, more polar analytes can be chromatographed without the need for mobile phase modifiers. Furthermore, the sensitive and universal flame ionization detector (FID) can be used, since modifiers are not necessary. To avoid splitting of the column effluent before FID detection, packed capillary columns were utilized in this study. The ability to use packed capillary columns for the analysis of polar compounds, while at the same time allowing the use of a wide range of detection methods, serves to expand the number of useful applications for packed column SFC.

Determination of flooding gas velocity and liquid hold-up at flooding in packed columns for gas/liquid systems.

Abstract: A new model of suspended bed of droplets for describing the vaour or gas the vapour or gas velocity at the flooding point in packed of columns for rectification and absorption under vacuum and normal pressure is presented metallic, ceramic and plastic packings with diameters of 8–90 mm as well on sheet metal and gauze packings, in a wide range of liquid and vapour loads. Approximately 650 literature measurements and own data were evaluated. The mean relative error in determining the gas velocity at flooding point is less than ±5%. On the basis of the double layer model, a new equation was derived for the hold-up at flooding point, which is needed for the calculation of the flooding gas velocity. An example of calculations for sample applications is also included.

Study of moisture transfer during the strand sintering process

Abstract: Moisture transfer during the strand sintering operation was studied both experimentally and using a mathematical model. The drying of iron ore pellets was found to occur in two distinct periods: one at a constant drying rate and the other at a decreasing drying rate, whereas the drying of zinc ore pellets always occurs at a decreasing drying rate. Characteristic drying curves were determined for both materials. The moisture transfer mechanisms during the sintering process were demonstrated in detail, including the recondensation of water in the cold layers of the bed and the formation of an inert, overmoistened zone. The mathematical model presented simulates all of these phenomena and is used to calculate the variables related to moisture transfer. The model is adaptable to other processes where a hot gas passes through a moist packed bed.

Effect of mobile phase density gradients on efficiency in packed column supercritical fluid chromatography

Abstract: The efficiency of packed columns was measured as a function of flow rate, temperature, outlet density, and the density differential across the column, unsing pure carbon dioxide as the mobile phase. Although density differentials are often blamed for a serious loss in efficiency in packed column supercritical fluid chromatography, the results show that efficiency was not a function of the density differential. Peak shapes suggest that apparent loss in efficiency is actually due to inadequate solubility of the solute in carbon dioxide.

Method and apparatus for oil well stimulation utilizing electrically heated solvents

Abstract: A method and apparatus of stimulating production from an oil well by removing solid wax deposits from a production zone, includes an electrical resistance heater comprised of a packed bed of spherical heating elements 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.

Adsorption and desorption of noble gases on activated charcoal: II. 222Rn studies in a monolayer and packed bed.

Abstract: The adsorptive and desorptive characteristics of canisters containing a petroleum-based charcoal were investigated under controlled conditions of temperature, relative humidity, and Rn concentration. Charcoals exposed in a monolayer and packed bed during exposure intervals of 1-7 d demonstrate that Rn adsorption and desorption are dependent on bed depth and the amount of water adsorbed. Changes in the adsorptive and desorptive properties of the charcoal occurred near the break-point where the pores became occluded by water vapor that condenses in the entrance capillaries. Radon-222 adsorption is decreased by an order of magnitude as the amount of adsorbed water exceeds the break-point of the charcoal. The reduction in pore surface due to adsorbed water results in a marked increase in the rate of Rn loss from exposed canisters, accounting for reduced adsorption. The apparent desorption time-constant for a 2-cm bed of loose Witco 6 x 10 mesh charcoal containing 0.220-0.365 kg H2O kg-1 is typically between 2-8 h. The apparent desorption time-constant for an equivalent packed bed containing a water vapor content of 0.026-0.060 kg H2O kg-1, which is below the break-point of the charcoal, is about 15-30 h. Conventional charcoal canisters, if exposed in the fully-opened configuration, can achieve the break-point in less than 4 d at 70% humidity. The use of a diffusion barrier would allow for longer exposure times until the break-point of the charcoal is achieved.

Antibody production in packed bed reactors using serum-free and protein-free medium

Abstract: The present work demonstrates the utility of packed bed reactors for the production of monoclonal antibody. We present data from a continuous process run for the production of over 100 grams of antibody, using serum-free medium. An additional pilot run also demonstrates the potential for continued antibody production under protein-free conditions, using a standard basal medium.

Methanol synthesis in a trickle-bed reactor

Abstract: A novel approach to methanol production from coal-derived synthesis gas is cocurrent gas and mineral oil feed flowing over a packed bed of catalyst in the trickle flow regime. Production rates of 0.7 to 2 kg/h · kg cat were obtained for a H2/(CO + CO2) ratio of 1 and at space velocities of 2,000 to 25,000 L/h · kg cat. Slurry reactor and bubble column productivities were substantially less for H2/(CO + CO2) ratios of 0.55 to 2.3 at similar conditions as the trickle-bed reactor. Reaction temperature was 250°C in three types of reactors but 240°C in gas-liquid phase Berty reactor; the pressure in the slurry and bubble column reactors was 52-70 atm and in Berty Reactor 77.5-100 atm, whereas 70 atm pressure was used in the trickle bed. Differences in production rates and conversions can be explained by the extent of backmixing in trickle-bed and slurry reactors operating at the same conditions.