Showing papers on "Countercurrent exchange published in 1987"

High-speed countercurrent chromatography

Abstract: Support-free high-speed countercurrent liquid chromatography provides a rich domain of applications, some beyond reach of conventional liquid chromatography.

Pressure swing adsorption process for gas separation

Abstract: An improved pressure swing adsorption process enables the more readily adsorbable component of a feed gas to be economically recovered, e.g. nitrogen from air. The more readily absorbable component is used as copurge at upper adsorption pressure, and less readily adsorbable component is used for countercurrent purge at subatmospheric desorption pressure and for initial repressurization in a countercurrent backfilling step.

Axial dispersion in plate-pulsed columns

Abstract: The residence time distribution (RTD) of the phase under continuous flow and dispersed flow was measured in a plate-pulsed column under countercurrent liquid-liquid flow, and modelled using (i) the axial dispersion model and (ii) the noninteger ideal stage cascade model. The axial mixing in the continuous phase was found to be significantly higher than in the dispersed phase. The model parameters were related to the operating conditions and system variables.

Analysis and experiment of boiling heat transfer on T-shaped finned surfaces

Abstract: The experiments of pool boiling were carried out on the T-shaped finned surfaces. The produced surfaces have precise geometric sizes. Therefore, the analysis of the heat transfer mechanism and the research of the optimal structural size are easily conducted. Based on the experiments and observations, a countercurrent two-phase flow model for boiling heat transfer on the T-shaped finned surfaces was proposed. Both relation for the heat transfer and the relation for the optimal slit width between T-shaped fins were obtained. The model was further extended to Thermoexcel-E surfaces, yielding the corresponding heat transfer relation.

Liquid-liquid extraction in a hollow-fiber device

Abstract: Liquid-liquid extraction operations were conducted in a hollow fiber mass transfer device using two systems: phenol/water vs. n-octanol and phenol/hexane vs. water. Individual mass transfer resistances due to the tube-side fluid, the hollow fiber wall (membrane), and the shell-side fluid were determined for runs in which the solvent was held stagnant on the shell-side. Countercurrent flow runs with moving solvent were conducted to show that the degree of extraction rises steadily as the solvent-to-raffinate ratio increases. Factors affecting the mass transfer resistances in this type of device are discussed, and the advantages of hollow fiber units over conventional mixer-settler units are pointed out.

The separation of lecithin and soya oil in a countercurrent column by near critical fluid extraction

Abstract: The present contribution illustrates a way of developing a continuous separation process for near critical fluid extraction, on the example of separation of soya oil from lecithin. First, a suitable solvent was selected. Phase equilibria were measured in autoclaves. Operating conditions for a pilot plant were derived from the phase equilibrium data. The pilot plant experiments provided the necessary data for designing a production plant. Computer programs for phase equilibrium, stage to stage and mass and heat balance calculations were used in order to minimize the number of experiments. A production plant with a capacity of 500 t/a of raw lecithin was designed on the basis of experimental and computational results. A cost estimation, based on tenders, showed that it is more economical to produce lecithin by near critical fluid extraction than by conventional acetone extraction.

Process and apparatus to improve the power factor of compressor-operated (hybrid) refrigerators or heat pumps functioning with solution cycle

Abstract: A process for the operation of hybrid compression-absorption heat pumps or refrigerators with the use of fluid medium containing a mixture of differently volatile components (typically two) easily soluble in each other. During heat extraction, in a first counter current heat exchange, vapor of the more volatile component is partially dissolved in the liquid of the less volatile component. Simultaneously, an additional portion of the volatile component is condensed. Importantly, the medium is discharged from the first heat exchange in a stage of incomplete dissolution/condensation of the vapor phase. The combined medium is expanded and absorbs heat in a second counter current heat exchange phase, during which the more volatile component is both expelled from the solution and evaporated. A counter current heat exchanger is connected between the first and second heat exchangers, and uses low pressure medium exiting from the second heat exchange to effect cooling and thus further dissolution and condensation of the high pressure medium exiting from the first heat exchange.

A simulation for liquid surfactant membrane permeation in a continuous countercurrent column.

Abstract: The continuous permeation of metal ions in a countercurrent column was simulated in order to develop a continuous separation process with the liquid surfactant membrane technique. In the simulation, an axial dispersion model was applied for a continuous phase. For the permeation of metal ion in a dispersed phase, an approximate model was adopted in which the external diffusion around the dispersed phase, the diffusion through a peripheral thin oil layer in the dispersed phase and the extraction reaction at the interface between the continuous and dispersed phases were taken into account. The observed concentration distributions of metal ions in the column reported by Marr et al. were satisfactorily simulated by the models applied and by use of the conventional relations for liquid-liquid extraction.

Process and apparatus for separating a gas mixture by adsorption

Abstract: Process comprising: a) isobaric concurrent production (fp1 - fp2); b) equilibration between the said adsorber under partial vacuum and another countercurrent adsorber under recompression (fC1 - N4); c) a partial countercurrent evacuation towards a storage vessel (fR); d) a final countercurrent decompression (fa); e) countercurrent sweeping with gas of the storage vessel (fb); f) a partial countercurrent recompression by at least one equilibration (f'e); g) a final countercurrent recompression (f'd1 - f'd2); according to which process the sum of the durations of the operations according to c) and d) is smaller than the said dephasing and the sum of the durations of the operations according to c), d) and e) is smaller than twice the said dephasing; h) at least two adsorbers are simultaneously on isobaric production, characterised by: i) the number of adsorbers is at least equal to four and smaller than 3 + x + y, x and y being the number of adsorbers on production and y the number of equilibrations; j) the evacuation is introduced into the storage; k) each equilibration is "direct". … …

Method for separation of coarse particules

Abstract: The disclosure herein describes a method for the separation of hydrophobic from hydrophilic materials in a liquid suspension by means of gas bubbles and a flow of water that drags the hydrophobic material upwards. A distinctive feature of the method is an upward flow of water countercurrent to the flow of settling hydrophilic particles. The disclosure describes a cell in which gas is caused to disperse into an ascending flow of liquid and in which a feed port is provided to introduce particles in a flow countercurrent to that of the bubbles and water.

Apparatus for continuously cooking and/or dehydrating foodstuffs

Abstract: The invention concerns a process and an apparatus for the continuous heat treatment of foodstuffs. Unlike in known cooking or boiling installations with a substantially homogeneous temperature control of the heat carrier in the form of water, a multizone installation comprising preheating, boiling and recooling zones is suggested, through which the foodstuffs to be treated are passed successively. The heat carrier is conducted through the recooling zone in a direction counter to the conveying direction and then, bypassing the boiling zone, is supplied to the preheating zone leading to a temperature rise in the latter due to the thermal energy passing to the heat carrier during the recooling process. The energy demand is covered by the heat supplied to the boiling zone, which also operates in the countercurrent principle with the aid of circulating means.

Limitations of the equilibrium theory of countercurrent devices

Abstract: In the analysis of countercurrent adsorption processes, an equilibrium theory in which local equilibrium between the fluid and the adsorbent phases is assumed has been used in the past to determine the composition of the pinch state that would be obtained for long columns. It is shown that this equilibrium theory is deficient and that certain mass transfer parameters, which are lost in the procedure by which the model equations for the equilibrium theory are formulated, can have a profound effect on the composition of the pinch.

Method and apparatus to produce a hot fluidizing gas

Abstract: A fluid bed reactor for treatment of refractory materials with a hot fluidizing gas and a method to use same. Both the refractory materials and the fluidizing gas are introduced from the top of the reactor. Unusually high reaction temperatures of up to 2000° C. are maintained in the reaction chamber due to the presence of heating elements within the reactor and due to countercurrent heat transfer.

Gas dispersed packed extraction column

Abstract: A liquid extraction process involving countercurrent flow of aqueous and organic liquid phases with gas dispersion in the organic phase is carried out in a pulsed column with for example a knitted bed, and the organic phase is discharged into the bed via a tube which physically supports the bed and is used for (optional) reciprocation of the bed to pulse the phases.

High-Pressure Transition Boiling in Internal Flows

Abstract: Transition boiling heat transfer was studied for the case of internal flow of high-pressure water. Transition boiling results were determined from measurements from 138 steady-state tests conducted in a temperature-controlled facility. Water flowed vertically upward inside a tube with inside diameter = 10.1 mm and vertical length = 13.1 m, as it was heated by liquid sodium flowing countercurrent in a surrounding annulus. The water parameter range of the experiments was pressure 7--15.3 MPa and mass flux 0.7--3.2 Mg/m/sup 2/xs. A mathematical model was developed that predicted the transition boiling heat transfer coefficient well over the entire parameter range.

Process for the preparation of monomeric alpha-cyanoacrylates

Abstract: 1 A process for the production of high-purity, monomeric alpha-cyanoacrylates by distillation under reduced pressure, characterized in that distillation is carried out in countercurrent under reduced pressure and with more than 10 separation stages, inhibitors are continuously added to the countercurrent at the uppermost separation stage and stabilized liquid alpha-cyanoacrylate is added at those places where condensate can occur

Heat exchanger for gases with sharply differing temperatures, especially in the cross countercurrent construction

Abstract: In such a heat exchanger with a bundle-like profile pipe matrix, the pipe separators must be vibration-damping packing elements made from an elastic material, in which elements the pipes of the matrix are directed movably relative to each other, especially in the longitudinal direction of the pipes.

Flow characteristics in a bubble column with enlarged section at bottom.

Abstract: The critical operation condition for complete countercurrent flow may be extended by enlarging the bottom of the bubble column. Several cylindrical enlarged sections of different diameter and length were examined and the critical liquid velocities were measured.It was found that the critical liquid velocity increased with increasing diameter or length of the enlarged section. An experimental equation for the critical liquid velocity was deduced.Higher gas holdup and liquid-phase overall mass transfer coefficient were obtained in the bubble column with enlarged bottom and correlating equations were derived.

Parametric Sensitivity Study of Adsorption in a Periodic Countercurrent Cascade of Stirred Tanks

Abstract: Material balance equations are developed to describe adsorption on activated carbon in either batch or continuous countercurrent systems. The carbon is divided into two regions with distinctly different kinetic characteristics. A Freundlich isotherm is used to describe the equilibrium adsorption of gold cyanide on activated carbon. Kinetic and equilibrium parameters estimated from batch tests are shown to predict the behavior of a small-scale continuous plant accurately. A parametric sensitivity analysis of this model is conducted in order to explain the factors which influence the efficiency of a carbon-in-pulp (CIP) plant used for the recovery of gold from cyanided pulps. The periodicity of the transfer of carbon countercurrent to the flow of pulp is shown to have almost no effect on the behavior of a CIP plant. Mixing should be more efficient in the stages where low concentrations in solution occur.

Process and apparatus for the increased preservation heat treatment, in particular by ultra-high heating, of products containing germs.

Abstract: In the process for a heat treatment prolonging the shelf life, in particular ultra-high heating, of products containing germs, a product stream is heated and subsequently cooled to treatment end temperature on a flow path covered over its entire length at an at least approximately constant flow rate, in indirect heat exchange with a heat transfer medium flowing in countercurrent in exchange zones, with the recovery of heat. At the beginning of a high-temperature zone which includes the treatment end temperature, the product stream is divided into parallel part streams of equal quantities, and in their separate part-flow paths, the part streams are exposed to treatment conditions of which are identical to each other. At the end of the high-temperature zone, the part streams are recombined to form one comprehensive stream.

Method and apparatus for the continuous heat treatment of food

Abstract: The invention relates to a method and apparatus for continuous heat treatment of foodstuffs. In contrast to known cooking apparatuses having a substantially homogeneous temperature profile of the heat carrier water, a multi-zone system consisting of pre-heat (6), cooking is proposed (14) and re-cooling zone (24) through which are passed foods to be treated successively. In this case, the heat transfer medium to the conveying direction is contrary flowing passed through the rear cooling zone (24) and from there fed bypassing the cooking zone (14) of the preheating zone (6), whereby due to the transferred to the heat carrier during the return cooling process thermal energy, a temperature increase of the latter takes place. The energy demand is met by supplying heat in the cooking zone, which also operates by means of recirculating the countercurrent principle.

Centrifugal type multistage countercurrent contact device

Abstract: PURPOSE:To effectively perform mass transfer between liquid and liquid by enhancing contact efficiency between light liquid and heavy liquid and increasing the number of theoretical plates. CONSTITUTION:A rotor 2 tightly stuck to a rotary shaft 1 is divided into multistages in the direction of the rotary shaft 1 and thereby countercurrent contact chambers 3a, 3b, 3c are provided. As a result, heavy liquid once separated in the outer periphery side of the rotor 2 is again returned to the center side of the shaft and similarly light liquid separated in the center side of the shaft is retransferred to the outer periphery side of the rotor 2 and respective liquids are successively subjected to countercurrent contact with fresh light liquid and heavy liquid. Therefore since the region of countercurrent contact is increased and also the number of theoretical plates can be increased by providing a packing material, both the countercurrent distribution between two liquids of a small difference in specific gravity and continuous treatment of large amounts are performed.

A Study on Instability of Falling Liquid Film in a Countercurrent Annular-Mist Two-Phase Flow

Abstract: Stability of liquid film in a counter-current two-phase flow of falling liquid film and upward mist flow, which is generated by spraying the liquid into gas flow, in a vertical pipe have been investigated both experimentally and theoretically. The liquid film flow rate, pressure drop, and interfacial wave velocity were measured for vapor-water and air-water systems. It is shown that, with increasing the spray flow rate under the condition of constant gas-phase velocity, the falling liquid film becomes unstable due to the impact of droplets flowing upward. With the onset of instability, flow reversal of liquid film, entrainment of droplets, and rapid increase of pressure drop occur. This instability occurs even in a stable range of conventional flooding correlation for a counter-current two-phase flow. Based on comparison between experimental results for a vapor-water system at a pressure lower then the atmospheric pressure, and an air-water system at the atmospheric pressure, the droplets' impingement effect on the stability of liquid film is correlated with the ratio of the momentum of the colliding droplets on the liquid film to the interfacial shear stress. A theoretical analysis on the stability of liquid film impinged by droplets is made. Nonlinear stability of a finite-amplitude interfacial wave is treated in the analysis. The theory predicts the existence of a stable finite-amplitude interfacial wave. It also predicts that the flow becomes unstable with increasing the gas velocity and the momentum of impinging droplets. The stability limit predicted by the analysis agrees well with the experimental results.

A differential model for a countercurrent extractor column with non‐constant flow rates, interfacial area per unit volume and axial dispersion coefficients

Abstract: In the extraction literature, no attention has been given so far to differential calculation models for countercurrent extraction columns which take into account the changes in flow rates of the phases as a result of transferred mass, and which also reflect the variations in interfacial area per unit volume and in axial dispersion coefficients since these depend on the flow rates. The present contribution puts forward a formulation of such a model; this results in a set of non-linear differential equations with separated boundary conditions, representing the feeds at either side of the extraction column. This set of differential equations must be solved numerically. The model is illustrated by a sample calculation on the extraction of benzene with furfural. In this (realistic) example, the interfacial area per unit volume varies from bottom to top by a factor of 3. Ignoring this effect would obviously result in serious under- or overdesign.