Showing papers on "Countercurrent exchange published in 1978"

Process for recovering heat from stack or flue gas

Abstract: A method and apparatus for efficiently recovering heat from a gas stream such as discharged flue gas. The gas stream is countercurrently contacted with a liquid medium in two stages. A first countercurrent contact stage is between a partially cooled gas stream and cold liquid medium in a bed of packing through which the cold liquid medium flows downwards and the partially cooled gas stream flows upwards, so that a warmed liquid medium and fully cooled gas stream are produced. The second countercurrent contact stage is between the warmed liquid medium derived from the first contact stage and the hot initial gas stream in a plurality of parallel vertically oriented passages. The warmed liquid medium flows downward on the inner walls of the vertically oriented passages as a thin liquid film, while the hot initial gas stream flows upwards within the vertically oriented passages, so that a fully heated liquid medium and the partially cooled gas stream are produced. The second contact stage accomplishes high direct contact heat transfer with low mass transfer, so that minimal heat is lost as heat of vaporization of liquid medium evaporated into the gas stream. The fully heated liquid medium is passed in indirect heat exchange with a fluid, so that the liquid medium is cooled and the fluid, which may be water, air, or a process fluid stream, is heated.

The Separation of Nonvolatile Substances by Means of Compressed Gases in Countercurrent Processes

Abstract: Mixtures of nonvolatile and heat-sensitive substances can be separated by means of compressed gases in countercurrent processes. Moreover, such separations can be carried out at lower temperatures than in vacuum distillation. Addition of an entrainer enables alteration of the relative volatilities of the components. That such a method of separation is feasible on a large scale is illustrated using as example the separation of monoglycerides from a mixture of oleic glycerides at e.g. 110°C/135 bar. Propane is used as compressed gas, and acetone as entrainer.

Char gasification in a countercurrent reactor

Abstract: A model is developed for the countercurrent char gasifier of Lurgi form. Char particles are fed to the top and oxygen, inert, and steam in the bottom. The combustion zone is defined as the zone in which there is a nonzero molfraction of oxygen. In the gasification zone, the particles are assumed to be a lumped system in which the Johnson reaction kinetic expressions are assumed to be valid with the water gas shift reaction at equilibrium. All of the reactions between oxygen and carbon and water and carbon are assumed to take place in the combustion zone but with the carbon-oxygen reaction predominating to form a shell progressive system within the particles. Radiation is taken into account, and parametric computations are made on temperatures, compositions, flow rates, and char reactivity. The maximum temperature is strongly influenced by radiation and its position is a sensitive function of the solid flow rate producing an ash layer at the bottom of varying thickness.

Apparatus for distribution separation processes

Abstract: In a process for separating miscible substances by mass transfer between two phases, at least one of which is a fluid phase (gas, vapor or liquid) and the other phase being a solid phase or a liquid phase (stationary or flowing in countercurrent with the aforesaid fluid phase, the mass transfer takes place and is substantially confined to the outside of the surface regions of the solid parts of porous material having the structure of an open pore foam, preferably substantially reticulated. This structure can be industrially reproduced in an idealized fashion in the form of interleading pores between which the solid parts are outlined in all three dimensions by concave shapes of spherical to near-spherical curvature corresponding to the outlines of densely packed phases. Column packings for chromotography, distillation, countercurrent extraction and similar process. The advantages are low pressure drops combined with high flow rates (which in the case of chromotography are advantageously in the turbulent range), low theoretical plate heights.

Countercurrent transport in the kidney.

Abstract: Renal physiologists recognized many years ago that the ability of a glomerular kidney to form a concentrated urine was correlated in some way with the possession of a loop of Henle (see 56). It was also recognized that more water than solute must be absorbed from the glomerular filtrate to produce a urine more concentrated than plasma. Smith (62, 63) quantitated the relative water reabsorption by noting that if the final urine were to be reduced to isotonicity by the addition or subtraction of water, the total solute excreted by the kidney per minute would occupy a volume of UCM!CpM, where Uis the urine flow, CM is the urine osmolality, and G],M is the plasma osmolality. Since the actual volume occupied by this solute is U. the quantity of water U UeM! G],M would have to be subtracted when the urine is hypotonic and added when the urine is hypertonic to bring the final urine to isotonicity. Smith called this virtual volume free water for the diluting kidney and negative free water for the concentrating kidney. Since the micropunc­ ture studies of Richards and his associates had shown that the glomerular filtrate was isotonic and remained so in the proximal tubule (57, 58), it was inferred that in the concentrating kidney the absorption of water in excess of its isotonic complement of solute took place somewhere in the distal nephron. For many years the mechanism of this distal water reabsorption remained totally obscure. It was suggested that it was by "active" water transport, but this concept turned out to be thermodynamically unsound (5). At last, in a series of brilliant papers, Kuhn and his co-workers implicated the medullary counterflow system (13, 3840). Analyzing analogous counterflow systems theoretically and experimentally, they pointed out that counterflow permitted a small single membrane effect to be multiplied manyfold to produce a highly concentrated fraction of the outflow.

Thermal design of a heat exchanger for heating or cooling blood.

Abstract: Experimental data, and their correlation with predictions from theory, are presented for the thermal design of a countercurrent heat exchanger for heating or cooling blood. The thermal design considers the influence on the Nusselt number of blood and the heat exchanger effectiveness of variables such as the blood flow rate, tube diameter and length, and the thermal properties of blood. The data presented are compared with data from the literature and with predictions from theory. Insofar as the design of a blood heat exchanger is concerned, flowing blood can be considered a single-phase fluid. Some applications of the thermal design analysis, the production and control of blood hyperthermia or hypothermia are discussed.

Carbon dioxide acceptor process using countercurrent plug flow

Abstract: Disclosed is an improved CO 2 acceptor process for the gasification of carbonaceous solids to produce H 2 , CO and CH 4 . In the process a hot calcined CO 2 acceptor solid and a carbonaceous solid are contacted in countercurrent plug-like flow in a gasification vessel filled with packing or other suitable internals. The CO 2 acceptor flows downwardly through the vessel in a fluidized state, countercurrent to entrained carbonaceous solid flowing upwardly through said vessel. The heat of gasification is provided by sensible heat transfer from the calcined CO 2 acceptor solid to the carbonaceous solid and by the exothermic heat of reaction of the calcined CO 2 acceptor with CO 2 generated in the process.

Analysis of three‐phase packed‐bed reactors

Abstract: Three-phase reactors involving a solid catalyst are normally used for production of product or removal of impurity. Equations are presented for these two measures of reactor performance for a first-order, reversible or irreversible reaction in an isothermal reactor. The results are presented in terms of dimensionless groups of the pertinent mass transfer, kinetic, and equilibrium (solubility) properties, and the gas and liquid flow rates. From the equations given, it is possible to predict the relative performance of concurrent (trickle bed) and countercurrent flow reactors and also the effect of mixing in the gas or liquid streams on performance.

Apparatus for distillation

Abstract: The thermal efficiency of an ammonia still is significantly increased by the use, in conjunction with the usual countercurrent steam stripping medium, of an auxiliary inert gas stripping medium initially heated and humidified by passage through a heat exchanger together with hot still bottoms derived from the still.

Mass transfer into laminar gas streams in wetted-wall columns with countercurrent gas-liquid flow

Abstract: The effect of the gas and liquid flow rates on the mass transfer rate in laminar gas streams in wetted-wall columns with countercurrent gas-liquid flow was studied. An approximate analytical solution was obtained for the average gas-phase Sherwood number as a function of the gas-phase Graetz number and the dimensionless interfacial gas velocity. Experiments were carried out on the absorption of ammonia into aqueous sulfuric acid solution and of methanol vapor into water, using two columns of different lengths. The agreement between the experimental and the predicted effects of both gas and liquid flow rates on the gas-phase mass transfer rate was found to be fairly good.

Countercurrent direct contact heat exchange process and system

Abstract: Recovery of energy from geothermal brines and other hot water sources by direct contact heat exchange with a working fluid, such as a hydrocarbon working fluid, e.g. isobutane, is described. The process and system consist of a plurality of stages (A, B, C, D, E), each stage including mixing (22, 48, 62, 76, 90) and settling (26, 52, 64, 78, 92) units. In the first stage (A), hot brine and warm working fluid are intimately mixed (22) and passed into a settler (26) wherein the brine settles to the bottom of the settler and the hot working fluid rises to the top. The hot working fluid is passed to a heat engine or turbine (30) to produce work and the working fluid is then recycled back into the system. The system is comprised of a series of stages (A, B, C, D, E) each containing a settler (26, 52, 64, 78, 92) and mixer (22, 48, 62, 76, 90), and wherein the working fluid and the brine flow in a countercurrent manner through the stages to recover the heat from the brine in increments and raise the temperature of the working fluid in increments.

Mass transfer into turbulent gas streams in wetted-wall columns with cocurrent and countercurrent gas-liquid flow

Abstract: The effects of gas and liquid flow rates on gas-phase mass transfer from a turbulent gas stream into a laminar falling liquid film in wetted-wall columns with cocurrent and countercurrent gasliquid flow were studied. Numerical solutions were obtained for the average gas-phase Sherwood number as functions of the gas-phase Reynolds number based on the gas velocity relative to the liquid surface, the dimensionless interfacial gas velocity, the gas-phase Schmidt number and the dimensionless column height. Experiments were carried out on the absorption of ammonia into aqueous sulfuric acid solution, using two columns of different dimensions. The agreement between experimental and predicted effects of both gas and liquid flow rates on gas-phase mass transfer rate was found to be fairly good.

Apparatus for separating ions present as solutes

Abstract: In apparatus for separating ions in a solution by countercurrent electrolysis, a generally cylindrical column is constituted by axially juxtaposed annular segments which define respective chambers separated by liquid-permeable partitions. The two axially terminal chambers contain electrodes. Radial bores in the segments permit introduction and discharge of the solution to be tested, of an electrolyte flowing countercurrent to the solution, and of a cooling liquid passing through a cooling coil in each chamber. A shaft axially extending through the column carries agitating blades in each chamber and is magnetically rotated.

Separation of butanediol

Abstract: PURPOSE:To separate butanediol from an aqueous solution thereof, efficiently with a small amount of heat by combining countercurrent extraction with recycling using a specific extractant and distillation.

A Cell for Countercurrent Electromigration Experiments for Molten Nitrates

Abstract: A new type of cell for countercurrent electromigration of molten nitrates is proposed, in which molten NH4NO3 is employed just above its melting point in a large cathode compartment. This cell can be used effectively without trouble of corrosion for the purpose of (1) enrichment of 6Li, (2) enrichment of heavier isotopes such as 7Li, and (3) measurements of relative internal mobility differences of cations and/or isotopes.

Continuous contact method and apparatus for gas with granular material

Abstract: PURPOSE:To carry out adsorption and desorption continuously without valve changing operation by countercurrent contact of granular material such as adsorbing agent which can be regenerated with gas while the agent falls within a catalyst apparatus so as to absorb gas components, and after the absorption (adsorption), by countercurrent contact with regenerating gas in regeneration apparatus.

Air bubble countercurrent separator

Abstract: PURPOSE:To continuously remove or concentrate a very small amount of substance in a large amount of liquid or to effectively separate a small amount of sample chromatographically, by carrying out air babble countercurrent separating operation giving centrifugal force by rotation to the spiral column.

Industrial burner for gaseous or liquid fuels

Abstract: A burner is connected to a fuel line and to an air supply line A countercurrent recuperator is attached to the burner for providing heat exchange between the supply air and the exhaust gases The recuperator has a frictional flow resistance to the exhaust gases and the supply air resulting in a pressure differential between entrance and exit of supply air, which is highly temperature dependent This pressure differential is employed for self-controlling the relative supply air flow to the burner at different operating temperatures