Showing papers on "Countercurrent exchange published in 1981"

Countercurrent flow absorber and desorber

Abstract: Countercurrent flow absorber and desorber devices are provided for use in absorption cycle refrigeration systems and thermal boosting systems. The devices have increased residence time and surface area resulting in improved heat and mass transfer characteristics. The apparatuses may be incorporated into open cycle thermal boosting systems in which steam serves both as the refrigerant vapor which is supplied to the absorber section and as the supply of heat to drive the desorber section of the system.

Method of extracting organic contaminants from process waters

Abstract: In a method for removing an organic contaminant from process waters, the contaminant is extracted from the water in a countercurrent extractor by a low-boiling water-immiscible solvent. The solvent extract is sparged with an inert gas to vaporize the solvent, and the raffinate is sparged with an inert gas to vaporize any dissolved solvent therefrom. Solvent is condensed from the vapors and returned to the extractor.

An efficient, general method for computation of countercurrent separation processes with axial dispersion

Abstract: A calculational method is proposed for the simulation of steady-state, multisolute, countercurrent extraction with axial dispersion. The method provides for complex chemical-equilibrium and phase-equilibrium relationships, and accounts for the individual resistances of the liquid phases in the calculation of mass-transfer rates. The solution procedure follows that developed by Newman (1967, 1968) for systems of simultaneous, second-order difference equations. Three example problems are solved to demonstrate the efficiency and flexibility of the method. These include (1) an example from McSwain and Durbin (1966), (2) calculation of axial-dispersion and mass-transfer parameters from experimental data for the extraction of acetic acid from water by a tertiary amine in an RDC extractor, and (3) simultaneous extraction of solutes that interact in an acid-base complexing reaction at the liquid-liquid interface. The examples all assume that extraction is governed by interphase mass-transfer rates and cell-wise backmixing; however, the method is also applicable to equilibrium-stage separators, separators described by the diffusional model of axial dispersion, and other countercurrent separation processes.

Method for recovering heat.

Abstract: A method of recovering the head of hot water or a hot aqueous solution whose temperature is higher than the ambient temperature but lower than 200 DEG C, wherein air or a non-condensing gas is brought into direct countercurrent contact with the hot water or hot aqueous solution to provide a heated gas mixture of water vapor and air or non-condensing gas, and the heat is recovered in the form of the sensible heat of the resulting heated gas mixture and the latent heat of the water vapor in said mixture is disclosed.

A Model of Countercurrent Steam-Water Flow in Large Horizontal Pipes

Abstract: A numerical study was performed to derive a model of countercurrent steam-water flow in large horizontal pipes, with application to the emergency core cooling (ECC) system of a pressurized water reactor. The purpose of the study was to provide data from which simple correlations could be obtained to describe mass, momentum, and energy exchange between the phases during hot leg ECC injection. It was assumed that steam, driven by a pressure drop from the upper plenum to the ECC injection port, flows counter to the subcooled ECC water. Several series of calculations were performed to determine the sensitivity of the ECC flow velocity at the entrance to the reactor vessel to the pressure drop, for several values of the mass and momentum exchange coefficients used in the numerical method. The results were consistent with those obtained from solution of the mixture equation, which did not involve interfacial drag or condensation.

Countercurrent solids-fluid contactor

Abstract: A method and apparatus for the countercurrent contacting of solid particles with a fluid is disclosed. The contacting is effected within a multistage tower, each stage having a weir means regulating the flow of particles within and from each chamber so that all particles receive approximately the same exposure to the contacting fluid. The disclosed design is readily scaled up to increase capacity without requiring proportional increases in the vertical dimension which are costly and might result in damage to the particles. The method and apparatus are especially adapted for washing salt from alumina microspheres.

Production of oxygen by air separation

Abstract: Production of oxygen from air, by compressing air to relatively low pressure, e.g. to about 3 atmospheres, and passing the compressed feed air to alternate passages of a reversing heat exchanger in heat exchange relation with a nitrogen waste stream, whereby water vapour and C0 2 in the feed air are frozen on the surface of the heat exchange passage. By reversing the flow streams the low pressure nitrogen waste stream now flows through the feed air passage. This causes sublimation or evaporation of the C0 2 and water vapour. A portion of the feed air is withdrawn at an intermediate point in the exchanger and is further cooled in a heat exchange passage in the lower portion of a non-adiabatic fractionating device. The cooled feed air withdrawn from the heat exchanger is partly condensed by evaporating oxygen liquid product, and is fed to the partial condensing zone of the fractionating device, whereby oxygen-rich liquid is condensed and withdrawn, and nitrogen is removed as overhead. The nitrogen is expanded in a turbine and is passed in countercurrent heat exchange relation to the partial condensing zone, thereby providing refrigeration to the system. The oxygen-rich liquid is reduced in pressure, e.g. to about 1 atmosphere, and is fed to the partial evaporation zone of the fractionating device whereby nitrogen-rich vapour is removed as overhead, and oxygen of about 95% purity is removed as a liquid. The waste nitrogen stream exiting the heat exchange passage of the fractionating zone is passed through one of the reversing passages of the reversing heat exchang - er, the fractionation being carried out so that there is only about a 3 o R temperature difference between the nitrogen waste stream and the feed air at the cold end of the reversing exchanger. The oxygen product is passed through a separate passage of the reversing exchanger also in countercurrent heat exchange relation with the feed air.

Numerical simulation of the countercurrent flow in a gas centrifuge

Abstract: A finite difference method is presented for the numerical simulation of the axisymmetric countercurrent flows in gas centrifuge. A time-marching technique is used to relax an arbitrary initial condition to the desired steady-state solution. All boundary layers may be resolved, and nonlinear effects may be included. Numerical examples are presented. It is concluded that this technique is capable of accurately predicting the performance of a wide variety of machines under all operating conditions of interest.

Production of nitrogen by air separation

Abstract: Production of nitrogen from air, by compressing air to relatively low pressure, e.g. to about 3 atmospheres, and passing the compressed feed air to alternate passages of a reversing heat exchanger in heat exchange relation with an oxygen-rich waste stream, whereby water vapor and CO 2 in the feed air are frozen on the surface of the heat exchange passage. By reversing the flow streams the low pressure oxygen-rich waste stream now flows through the feed air passage. This causes sublimation or evaporation of the CO 2 and water vapor. A portion of the feed air is withdrawn at an intermediate point in the exchanger and is expanded in a turbine. The cooled feed air withdrawn from the heat exchanger is fed to a non-adiabatic fractionating device, whereby oxygen-rich liquid is condensed and withdrawn, and nitrogen is removed as overhead. The oxygen-rich liquid is mixed with the portion of feed air discharged from the turbine, and such mixture, and the nitrogen overhead are passed through the fractionating system in heat exchange relation with and countercurrent to the feed air being separated in the fractionation zone. The waste oxygen-rich stream exiting the heat exchange passage of the fractionating zone is passed through one of the reversing passages of the reversing heat exchanger, the fractionation being carried out so that there is only about a 3° R temperature difference between the waste oxygen-rich stream and the feed air at the cold end of the reversing heat exchanger. The nitrogen product is passed through a separate passage of the reversing heat exchanger also in countercurrent heat exchange relation with the feed air.

Column for mass-and/or heat transfer-processes

Abstract: Built-in element (1) for a mass transfer column, the structure of which is composed of parallel, vertical contacting layers (2) obliquely to the column axis superposed guide surfaces (3). Here, the layers (2) are arranged so that the guide surfaces (3) of adjacent layers (2) cross each other, wherein open at both ends through the flow channels (4) are formed. Such a formed packing element (1) causes an improved and accelerated mass transfer between two passes through it in countercurrent fluid media.

Multi-effect rotary distillation process

Abstract: A thermally driven multi-effect distillation process and apparatus are disclosed in which liquid is introduced into a plurality of evaporating and condensing stages or chambers while heat energy is passed through the stages or chambers in a direction countercurrent to the direction of flow of the liquid which undergoes evaporation to form condensate and distilland in each stage or chamber while transferring the heat of condensation to the next downstream stage or chamber and maintaining a minimum temperature differential between stages or chambers, and separately removing condensate and distilland from each stage or chamber while rotating the stages or chambers about an axis passing through the points of introduction thereto of the liquid and heat energy. Generally the apparatus comprises a plurality of adjacent evaporation and condensation chambers and means for introducing liquid and heat energy thereto in countercurrent directions. The walls of the chambers, formed of spaced heat conductive sheets, act as heat transfer means. Common walls of adjoining chambers provide condensing and evaporating surfaces on the opposite sides. The chambers are provided with means for separate removal of condensate and distilland and means for rotating them about an axis passing through the points of introduction of liquid and heat energy thereto.

Computer Simulation of Zirconium-Hafnium Separation by Countercurrent Extraction

Abstract: In carrying out research and development on an improved method for production of reactor-grade zirconium oxide, the Bureau of Mines has prepared a computer program capable of accurately predicting the stage-by-stage performance of a multistage countercurrent solvent extraction system for separation of zirconium from hafnium using a tertiary amine extractant. The results were used to plan laboratory experiments using a multistage countercurrent mixer-settler unit. The number of extractor stages, number of scrubber stages, feed solution concentrations, scrubber solution concentration, feed flow, scrubber flow, and organic-phase flow are the significant variables. The computer simulation indicates the effects of changes in the pertinent variables and makes it possible to locate the best combination of variables without a prohibitively large number of time-consuming experiments.

Process and apparatus for heating or cooling light solid particles

Abstract: The invention discloses a process and apparatus for the heating or cooling of light solid particles having a low free-fall speed, by means of flowing gas-solid exchangers. The process makes it possible to heat or cool light solid particles dispersed in a gas flow by contacting them with a countercurrent flow of heavy solid particles having a greater final free-fall speed and that are hot or cool in relation to the light particles, thus effecting a heat transfer between the particles.

Countercurrent heat exchanger for two streams of solids using heat pipes

Abstract: Disclosed are apparatuses and methods for transferring heat from a relatively hot stream of solid materials to a relatively cold stream of solid materials. Both streams cascade downward under the force of gravity over a series of heat pipes which are arranged between the streams to transfer heat therebetween. The heat pipes are arranged so they provide countercurrent heat transfer between the two materials streams. The invention is shown applied to a process for recovering hydrocarbons from shale rock.

Improved ion exchange particle regeneration method

Abstract: A method of regenerating particles in an ion exchange column wherein the physical characteristics of a regenerating fluid cause regenerated particles to be displaced from the original bed of particles and flow in a direction countercurrent to that of the fluid.

High temp. gas desulphurisation with lime - sliding downwards over gratings in shaft reactor in countercurrent to gas

Abstract: Desulphurisation of gases with any temp. up to 1000 deg.C is carried out by passing the (waste) gas in countercurrent to lump lime sliding downwards over gratings in a shaft reactor. Complete utilisation of the countercurrent principle is possible and the layer of material on the gratings has a relatively high air passage area, allowing optimum contact between gas and lime.

Biological nitrifying denitrification apparatus

Abstract: PURPOSE:To improve denitrification efficiency without increasing circulating pump power by feeding air to the liquid downward countercurrent part of a deep-well- shaped nitrifying part and opening the discharge end of the ciculating line communicating an NOx reducing part and the liquid downward countercurrent part of the nitrifying part above the liquid surface. CONSTITUTION:Feed water is supplied from an inflow pipe 14 to the inflow part of a denitrification tank 1. The NOx-N in the nitrifying liquid flowing in from a nitrifying tank 2 is reduced to an N2 gas and is thereby denitrified. During this time, the BOD components in the feed water is utilized as a hydrogen donator of denitrification bacteria. The denitrified liquid is transferred from a circulating pump 8 into the nitrifying tank 2 and the air supplied from a supply pipe 12 is supplied to the region where virtually no water pressure is applied in the upper part of a liquid downward countercurrent part 5. The discharge liquid of the pump 8 contains air bubbles and flows downward, then ascends in a liquid upward countercurrent part 6, reaches the upper part of the tank 2, and is sent from an outflow part 13 to a solid-liquid separating process, but the greater portion of the nitrifying liquid is circulated to the tank 1 via a communicating path 3, thus it is continuously and efficiently NOx-reduced.

Process for the separation of mixtures by means of mass transfer at different temperatures or pressures

Abstract: The invention relates to a process for the separation of material mixtures by means of mass transfer of different phases, which at least partly circulate in countercurrent in a closed circuit in which part of the mass transfer devices are operated at a higher temperature or pressure and another part thereof are operated at a lower temperature or pressure. The separating effects are achieved in that at least one third of one of the components of the mixtures also changes phase state with respect to the particular temperature or pressure change. The process is particularly suitable for the separation of methane and argon from the synthesis circuit of an ammonia plant. The otherwise conventional hydrogen and ammonia are largely avoided. The process requires neither compressors nor high pressure pumps nor low-temperature devices.

Single and multi-stage countercurrent bubble column loop reactor performances

Abstract: In 254 cm high single- and three-stage countercurrent stainless steel tower loop reactors of 20 cm in diameter. Hansenula polymorpha was operated in extended culture employing ethanol as a substrate and Desmophen 3600 as an antifoam agent. In the three-stage column, higher cell productivity, OTR, k L a and lower specific energy requirement with regard to the absorbed oxygen and/or produced cell mass have been attained than in the single-stage column. The reactor performance is especially high, if the bubbling layer height is reduced to 20 cm.