Showing papers on "Countercurrent exchange published in 2006"

Removal of Carbon Dioxide from Natural Gas by Vacuum Pressure Swing Adsorption

Abstract: A vacuum pressure swing adsorption (VSA-PSA) process is studied for the removal of carbon dioxide in a contaminated stream of natural gas to achieve fuel grade methane. The adsorbent used was zeolite 13X (CECA) where CO2 is strongly adsorbed. A Skarstrom-type cycle comprising pressurization with product, feed, countercurrent blowdown, and countercurrent purge was employed. A mixture having 60% CH4/20% CO2/20% N2 was used, and two different temperatures were evaluated in a single-column VSA-PSA unit. Under the conditions tested, CO2 was removed to levels lower than 2% as required by fuel grade methane with methane recovery higher than 80% without recycle. This separation process also helps in the CH4−N2 separation. A bidisperse (macropore−micropore) model also including distributed energy balances in gas, solid, and column wall considering heat and mass transfer resistance at the gas−solid interface was used to simulate the VSA-PSA behavior and compare with experiments. Also, some scale-up considerations a...

Flow and Heat Transfer Prediction in a Corrugated Plate Heat Exchanger using a CFD Code

Abstract: The purpose of this study is to explore the potential of using a general purpose CFD code to compute the characteristics of the flow field, and of the heat transfer augmentation in conduits with corrugated walls, encountered in commercial plate heat exchangers (PHE). The CFD code is used to simulate the performance of a PHE model comprised of stainless steel plates, following a herringbone design and assembled for single-pass countercurrent flow. The code is validated by comparing the numerical results with experimental data on pressure drop and overall temperature differences acquired for the countercurrent flow of water at both sides of the model PHE. The limited data published in the literature are also in fairly good agreement with the results of the present study. It is shown that the CFD code is an effective and reliable tool for studying the effect of various geometrical configurations on the optimum design of a PHE.

Temperature Profiles within a Double-pipe Heat Exchanger with Countercurrent Turbulent Flow of Newtonian Fluids: Derivation, Validation, and Application to Food Processing

Abstract: Pasteurization or sterilization of food and bioproducts is mostly performed using heat exchangers in countercurrent flow. The lack of appropriate analytic solutions for temperature profiles in the heating and cooling sections of such processes is most likely the main reason for the traditional cautious approach of disregarding the contribution of these stages in the total thermal history calculation. This approach leads to excessive thermal abuse of the product. The current manuscript describes the derivation and validation of an analytic solution for the temperature profiles within a double-pipe heat exchanger with countercurrent turbulent flow of Newtonian fluids, at any possible flow rate and not necessarily assuming an isothermal heating medium or coolant. The presented solution is based on application of the “heat exchanger effectiveness” concept in a partial heat exchanger, and can be easily solved and plotted using a spreadsheet. An interactive ExcelTM workbook was developed for fast prediction of temperature profiles and used in a simulated case study to demonstrate the influence of operating conditions on the temperature profile and thermal history of a pasteurized liquid product.

General regularities of liquid chromatography and countercurrent extraction

Abstract: Some general regularities of liquid chromatography with a free stationary phase and countercurrent extraction are considered. An analytical solution to the linear model of nonequilibrium chromatography is presented.

Process for producing monosilane

Abstract: The present invention relates to a plant and a process for the continuous production of monosilane and tetrachlorosilane by catalytic dismutation of trichlorosilane at an operating temperature and a pressure of from 1 to 50 bar abs. in a plant according to claim 1, in which - trichlorosilane (A) is preheated in a heat exchanger (7), and fed to the 10 countercurrent reactor (1) which is provided with catalyst (3), - product mixture formed in the countercurrent reactor (1) is at least partly condensed by means of the condenser (5) at a temperature in the range from -25 to 50~C with the condensate flowing back into the countercurrent reactor (1), - the product phase which is not condensed in the condenser (5) is passed to the 15 condensation unit (8) which is operated at a temperature in the range from -40 to -110~C, - the volatile product phase from the condensation unit (8) is fed to the distillation column (9) which is operated at a temperature in the range from -60 to -170~C and monosilane (C) is discharged at the top of the distillation column (9), 20 - the SiCl4-containing bottoms from the countercurrent reactor (1) are brought to a temperature in the range from 60 to 110~C in the vaporizer unit (6) and - bottom product from the vaporizer (6) is conveyed via a heat exchanger (7) into the double wall (2) of the countercurrent reactor (1) and the SiCl4-containing product stream (B) is discharged at a level in the upper region of the reactor (1).

Separation of mixtures and distribution of a liquid on a structured packing in a large-scale model of a distillation column

Abstract: A large-scale experimental setup is designed to study the hydrodynamic parameters and the mass-transfer efficiency in a countercurrent flow of mixtures of Freon R21 and Freon R114 on structured packings in a column 0.9 m in diameter. The study deals with the local and integral parameters of separation of the mixture, the degrees of nonuniformity of the flow rates and concentration distributions of the liquid and vapor phases over a cross section and on the column wall, and the pressure difference while varying the number of packing layers and their rotation angle. The mass-transfer processes while independently varying the liquid and vapor flow rates over wide ranges are also investigated. Experimental data are presented to illustrate the effect of the operating parameters on the height of an equivalent theoretical plate, the relative pressure difference, and the distributions of the local parameters of the flows.

Chemisorptive Removal of Carbon Dioxide from Process Streams Using a Reactive Bubble Column with Simultaneous Production of Usable Materials

Abstract: In the context of attempts to improve the protection of the environment, a novel process where the carbon dioxide reacts rapidly with almost 100% conversion under mild conditions, is proposed. The chemisorptive process takes place in a slurry bubble column which operates with countercurrent flow, utilizing special solutions of primary long chain amines in a nonaqueous media. The product obtained is insoluble and separated by filtration. Because of its molecular structure, this product possesses tenside properties and can be used as an industrial additive. Typically the liquid phase consists of a mixture of hexadecylamine (C 16 H 33 NH 2 ) or dodecylamine (C 12 H 25 NH 2 ) in various concentrations with methanol or other alcohols as the solvent. Numerous parameters have been studied including different column heights, gas inlet compositions, gas flow rates and solvent type. Efficiencies of up to 99 % are achievable for CO 2 absorption with methanol as the solvent. The second solvent examined, isopropanol, shows lower CO 2 conversion rates. This can be attributed to its physical properties, mainly higher viscosity and hence, smaller mass transfer coefficient. In order to simulate real gas conditions, the influence of other sour gases, e.g., SO 2 was also investigated experimentally. Because of coabsorption of the two gases, the CO 2 efficiency was lower in this instance. In both solvents, the absorption efficiency with respect to SO 2 is more than 99 % due to its high solubility and reactivity. A complex mathematical model has been developed and applied to describe the mass and enthalpy transport in the reactive bubble column.

Study on two-phase countercurrent flow and transport phenomenon in PEM of a direct methanol fuel cell

Abstract: Based on the requirement of water management for a direct methanol fuel cell, this paper analyzes qualitatively the mechanism of occurrence and development of a two-phase countercurrent flow with corresponding transport phenomenon in the PEM. A one-dimensional, steady state quantitative model of heat and mass transfer in internal volumetric ohmic heating porous media saturated by liquid and vapor phases is developed. The effects of capillarity, electro-osmotic drag and phase change are included. Two important formulas to calculate the theoretical length of two-phase zone δ t and determine the critical criterion |−ω/γ|cr for dryout in PEM are deduced. By use of these two dimensionless parameters, dryout of PEM can be easily predicted. Theoretical temperature, pressure and saturation profiles within the two-phase region are obtained numerically, which can help to explore the performance of a DMFC operating in its ohmic polarization region. The simulation results can be used to determine the catalyst content of cathode catalyst layer and the corresponding optimal thickness of PEM.

Effect of gas density on countercurrent flow limitation in wetted wall column

Abstract: Countercurrent wetted wall flow limitation was studied in a 20.6 mm i.d. cylindrical column, with water as the liquid. The gas was either air at up to 0.8 MPa, or argon at up to 1.3 MPa, thus covering a range of gas densities (1.6–21.3 kg/m3) of great practical interest for which very few data are available. The film Reynolds number varied in the range 515–3090. The velocity of gas for which signs of flooding instability first became apparent was typically 5 to 25% below the velocity at which liquid carryover started and this may be a result of the particular design adopted for fluid inlet to and outlet from the test section. Over the range of gas densities tested, the limiting gas velocity decreased with pressure from between 2.5 and 5.0 m/s to between 0.4 and 0.8 m/s, very approximately following the law: (gas density) × (limiting gas velocity)2 = constant. The data collected were used to test the correlation of Wallis, which gave remarkably good prediction of the limiting gas velocities, and a correlation of Alekseev and coworkers modified by McQuillan and Whalley in 1985, which gave poor predictions, particularly with regard to the effect of changes in liquid flow rate. The results of the present work are shown to be useful in interpreting recent data on the effect of gas density on the slug/churn flow transition in cocurrent vertical gas–liquid flow. © 2006 American Institute of Chemical Engineers AIChE J, 2006

Process for producing methanol

Abstract: This invention is directed to a process for producing methanol. The methanol product that is produced according to this invention is achieved with a high conversion of synthesis gas. The high conversion of synthesis gas is achieved by flowing a liquid layer across a plurality of catalyst beds countercurrent to the gas flow. The gas containing methanol product exiting each bed flows through the liquid layer. The liquid acts to extract methanol from the gas, as well as cool the gas.

Mathematical modeling of continuous production of carbon nanofibers from methane in a reactor with a moving bed of a nickel-containing catalyst

Abstract: The continuous production of carbon nanofibers from methane on a Ni/Al2O3 catalyst (90 wt % Ni) in a plug-flow reactor with countercurrent or cocurrent flows of the phases is considered. The methane conversion, specific carbon content, and relative catalyst activity in the reactor are calculated as functions of the longitudinal coordinate, temperature, and specific gas and catalyst flow rates. It is shown that, at a fixed specific methane flow rate, there is an optimal specific catalyst flow rate at which the specific yield of carbon nanofibers is maximal, with this yield in the cocurrent reactor being higher than that the countercurrent reactor. At certain parameter values, the reactor may contain a region with a virtually deactivated catalyst, which is indicative of inefficiency of use of the reactor space.

Optimum Channel Inclination for Gas Venting Under Countercurrent Flow Limitations

Abstract: Countercurrent flow limitation (CCFL) in the pressurizer surge line of future Pressurized Water Reactors (PWR) with passive safety systems is an important phenomenon in reactor safety analysis. The pressurizer surge line is typically comprised of several sections with various inclination angles. Under certain accident conditions, countercurrent flow takes place in the surge line with liquid flowing down from the pressurizer and steam flowing up from the hot leg. The steam venting rate as well as the liquid draining rate may affect the Emergency Core Cooling System (ECCS) actuation. The objective herein is to develop a physics-based model for evaluating the effect of inclination angle on CCFL. For a given liquid superficial velocity in the countercurrent flow system of the pressurizer surge line, the gas superficial velocity should be as large as possible at the onset of flooding, so that the steam can vent as fast as possible without inhibiting the pressurizer drain rate. Thus the system could de-pressurize in a timely manner to initiate the ECCS actuation. As indicated by CCFL experiments, for a given liquid superficial velocity, the gas superficial velocity attains a greatest value at a certain channel inclination, which is defined as the optimum channel inclination. Inmore » the present work, an analytical model is proposed to predict the optimum channel inclination under simplified conditions. The model predictions compare favorably with experimental data. (authors)« less

Nonstationary heat and mass transfer in evaporative cooling of flowing liquid films

Abstract: A mathematical model of nonstationary evaporative cooling of a laminar liquid film flowing down a vertical surface in its blowing with a countercurrent steam-air flow has been developed. The problem of heat and mass transfer has been formulated in a conjugate statement. The calculated data on the time change in the temperature and concentration fields in the steam-air flow and the liquid film as well as in the density of the heat flux on the flowing-film surface have been given.

Automatic water desalination plant, based on evaporation using solar collector and heat pump or Peltier element, using countercurrent principle for partial energy recovery

Abstract: An automatic water desalination plant as in Claim 1 of (based on evaporation using a solar collector and a heat pump or Peltier element) is claimed, in which: (a) the countercurrent principle is used (13) for partial recovery of the expended energy, thus supporting the distillation process; (b) on exceeding a specific weight, density or driving action due to the increased salt solution concentration during distillation, the salt solution is evacuated; (c) fuel oil of b.pt. more than 270[deg]C and extremely low flammability is used as cheap and safe heat carrier; and/or (d) preheated salt water is supplied via a valve controlled by a float in the evaporation chamber.

Semiempirical model of carbon dioxide boiling in tubes

Abstract: A mathematical model of the evaporator of a heat pump with carbon dioxide as a working medium and water as a heat-transfer medium is constructed and used to calculate the hydrodynamic and heat-and mass-transfer processes in boiling liquid convection, liquid film evaporation, film breakup, drop settling, and disperse flow. The coupled heat transfer between the working medium and the heat-transfer medium in a countercurrent evaporator is considered. The calculation results are compared with the experimental data.

Compact fan, comprising a heat exchanger with integrated or attached ventilators

Abstract: The invention relates to a coiled heat exchanger (WT), which has 360° channels (K1 - K6) following one after the other from the inside to the outside, wherein the first exchange medium (A) is admitted to the first channel and the second exchange medium (B) is admitted to the following channel in countercurrent, with some open and some closed annular passages, which form annular elements for the inflow and outflow of the exchange media (A, B) in such a way that lying approximately opposite an open sector of the annulus on one side of the heat exchanger there is a closed sector of the annulus on the other side of the heat exchanger and that the media flows (A, B) are thereby brought together at the extreme ends with the aid of segmental distributor caps (AK, AbK) It is proposed that, by attaching and/or integrating suitable feeding equipment, in particular ventilators (RLK, RLWK), pumps or feed membranes, and by means of routing the channels in the covers or adapters in such a way as to match the segmental connection areas of the heat exchanger, the heat exchanger (WT) is formed as a compact unit, in particular for air-to-air heat exchange in a device for controlled building ventilation with heat recovery

Heat exchanger for air conditioner

Abstract: The utility model discloses a heat exchanger for air conditioners, which comprises hydrophilic aluminum foil, a size U-shaped tube, a sheet metal end plate and various pipeline connecting pieces. An inlet tube set is divided into two ways which are respectively connected with inlets of an upper countercurrent segment and a lower countercurrent segment on an air-out side, and a collecting tube set is connected with outlets of the upper countercurrent segment and the lower countercurrent segment on a windward side; the collecting tube set is connected with an inlet of an over-cooling segment; an outlet of the over-cooling segment is connected with an outlet tube set; the collecting tube set and the over-cooling segment are arranged in the middle part of the windward side; an inlet of the lower countercurrent segment is arranged at the bottom of the heat exchanger for air conditioners. The utility model has the refrigeration high efficiency and the heating high capability of a split type heat pump air conditioner, and simultaneously solves the problem of heating defrosting under a low temperature work condition. The utility model has the advantages of simple structure and strong batch production capability, and does not need to reform the existing equipment and mould greatly.

Mass-transfer flow in a parallel-plate channel with permeable barriers inserted for countercurrent multi-pass operations

Abstract: The mass-transfer flow of a multi-pass counterflow laminar mass exchanger by inserting three permeable barriers with external refluxes was investigated theoretically, and the mathematical formulation was developed as well. With the use of an orthogonal expansion technique and the eigenfunction expanding in power series, the analytical solutions were obtained for finding the outlet concentration and mass transfer efficiency. The influences of the design parameters, the channel thickness ratio (β) and barrier characteristics (γ), and the operating parameters, the mass-transfer Graetz number (Gz m ) and recycle ratio (R), are examined. Theoretical predictions of the new multi-pass operations are compared with those in the single- (without the permeable barrier inserted) and double-pass operations under the same working dimensions and represented graphically. The results show that the influences of the recycle ratio and channel thickness ratio in the present device with external refluxes are dominant...

An Analytical Study of Mass Transfer Efficiency in Double-Pass Parallel-Plate Mass Exchangers under Uniform Wall Fluxes

Abstract: A permeable barrier was inserted to divide an open duct into two subchannels of uniform wall fluxes for conducting double-pass laminar countercurrent operations. The mass transfer rate of such a double-pass device was substantially improved and has been investigated theoretically by using an eigenfunction expansion in power series. The theoretical predictions of mass-transfer efficiency enhancement in double-pass parallel-plate mass exchangers were represented graphically and compared with those in an open duct of single-pass operation (without a permeable barrier inserted). The results show that the double-pass operation can effectively enhance the mass transfer efficiency and especially when the permeable-barrier position is appropriately adjusted.

Evaluation of Decolorization, Mineralization, and Toxicity Reduction of an Azo Dye C.I. Reactive Black 5 in a Countercurrent Bubble Column by Ozone

Abstract: A countercurrent and continuous-flow design bubble column reactor (BCR) was used to investigate variations in traditional parameters of water-containing Reactive Black 5 (RB5) under different gas/liquid flow rates. RB5 is a long-chain diazo dye with a high molecular weight that is widely applied in industry. The results revealed that the variations were functions of the flow rates of the liquid and/or gas and of operation column height. Pseudo-first-order or global-second-order reaction types were used to describe the variations, and the monitored parameters i.e., total organic carbon (TOC), sulfate, and nitrate. Not only did flow patterns affect the RB5 removal and the mineralization of derivatives, but column height might also have had an influence on ozone consumption. It was observed that the extent of decolorization and mineralization decreased as the sampling port height increased, indicating that the column height may reflect the retention time of ozone gas and the contacting time between ozone and...

High-temperature thermochemical amino energy storing device

Abstract: The utility model relates to a high-temperature thermochemical amino energy storing device, wherein an amino heat-absorbing reactor (2) is connected with a heat-absorbing side countercurrent heat exchanger (1) through a pipeline; a heat-releasing reactor (6) is connected with a heat-releasing side countercurrent heat exchanger (7) through a pipeline; a main high pressure storage tank (9) is connected with the heat-absorbing side countercurrent heat exchanger (1) via an ammonia feeding pump (10) through a pipeline; the heat-releasing side countercurrent heat exchanger (7) is connected with the main high pressure storage tank (9) via a course condenser (8) through a pipeline; the main high pressure storage tank (9) is connected with heat-releasing side countercurrent heat exchanger (7) via a composite and recirculation compressor (5) through a pipeline. The utility model can effectively convert solar heat energy, high temperature heat energy, residual heat or waste heat, etc. into chemical energy, and store the chemical energy into a reaction medium. When used, the utility model reverses the chemical energy into heat and releases the heat by means of reverse thermochemical reaction method to obtain high-grade heat energy.

Novel technology: Fresh approach to countercurrent ion exchange

Abstract: By reversing a commonly-used way of distributing fluids to ion-exchange cells, Belgian separations technology company PuriTech has developed a liquid adsorption separation technology, which could improve liquid-resin contact efficiency, while reducing plant operating costs and CAPEX, explains Filip Rochette.

Multi-group heat exchanger

Abstract: The utility model discloses a multibank heat exchanger arranged in heating pipeline for keeping warm and enjoying hot shower through heat exchange, which comprises a heat supply inlet connector and a heat supply outlet connector fixed on the heat exchanger and a plurality of heating pipes; one end or both ends of the two heating pipes are communicated witheach other through communication tube to form ''U''-shaped heat supply channel; a heat absorption tube is arranged in the heating pipe and the communication tube; one group of heat exchanger comprises the heating pipe, the communication tube and the heat absorption tube; one heat exchanger can be communicated with another through a conduction tube between heat exchangers to form the multibank heat exchanger, the heat absorption tubes in the multibank heat exchanger are connected for conduction and the water supply connector and the water outlet connector of the tap water are separately connected on both ends of heat absorption tube. Each group of heat exchanger is superposing arranged or parallel arranged. A countercurrent flow structure is formed by the heating pipeline and the heat absorption pipeline. The utility model has advantages of small volume, little occupation space, high utilization ratio of thermal energy, simple manufacturing technology and low production costs.

Distillation column for recovering vapor from aqueous solution, especially alcohol-containing fermentation solution, has rectification plates with back-flow device separate from steam outlet

Abstract: In a distillation column for recovering vapor (especially alcohol vapor) from an aqueous solution using steam in a countercurrent process, having rectification plates with a back-flow device for the aqueous solution, the back-flow device (5) is separate from a steam outlet (7.1, 7.2) in at least one of the rectification plates (2.1, 2.2, 2.3).