Showing papers in "Chemie Ingenieur Technik in 1978"
65 citations
TL;DR: In this paper, the geodetical and momentum pressure drop are discussed and reasonable correlations are presented, along with their limitations and range of application. And the accuracy of the prediction of some generally accepted void correlations is dealt with; here too, numerous published void fraction data have been gathered and checked.
Abstract: Pressure drop during gas/vapour-liquid flow in pipes. Pressure drop in two phase flow is considered to be made up of terms for geodetical elevation or depression, acceleration, and friction. The geodetical and momentum pressure drop are discussed and reasonable correlations are presented, along with their limitations and range of application. Various relationships are available for calculating the technically important friction component. However, such predictions are still relatively inexact. If purely empirical correlations are neglected, all the remaining predictive schemes can be related to three basic physical models. These models as well as the commonly accepted and most reliable relationships are discussed and classified according to type. Furthermore, their scope is defined and the accuracy of prediction systematically compared with the aid of a newly set-up data bank. The extensive literature data consulted refer to single component two phase flow of water and various refrigerants and several two-component systems in horizontal and vertical unheated straight pipes under industrially relevant flow conditions. Finally, the accuracy of the prediction of some generally accepted void correlations is dealt with; here too, numerous published void fraction data have been gathered and checked.
44 citations
TL;DR: In this article, an automated full-scale plant has been developed in collaboration with an industrial firm for the treatment of copper-containing electroplating wash waters and the first results obtained in a trial run are given.
Abstract: Fixed-bed electrolysis – a process for purifying waste water contaminated with metals. In an effort to combine the purification of metal-containing electroplating wastes with the recovery of valuable materials and a recycling of the wash water greater substitution of the hydroxide precipitation will be necessary in the future. The electrochemical separation of dissolved metals represents an interesting alternative if material transport is intensified by use of a fixed-bed electrode and the specific surface area of the electrode is so increased that high yields of recovery are achievable from low concentrations. The separation of various metals and the influence of operating parameters have been investigated on a pilot-plant scale, and separations of down to less than one 1000th of the initial concentration and final concentrations below 0.1 ppm are currently being achieved. On the basis of these investigations an automated full-scale plant has been developed in collaboration with an industrial firm for the treatment of copper-containing electroplating wash waters. The first results obtained in a trial run are given.
30 citations
TL;DR: In this paper, the authors consider the effect of the volume-specific mass transfer area on the attainable conversion and yield of a gas/liquefloor nuclear reactor and show that the relationship between these parameters can be plotted quantitatively in a working diagram for each reactor type.
Abstract: Criteria for the choice and design of gas/liquid reactors. The mass transfer area in a given reactor volume can be varied over several orders of magnitude by the choice of operating parameters. The way in which the volume-specific conversion can be altered by variation of the volume-specific mass transfer area depends upon the rate of the chemical reaction. The greater the volume-specific mass transfer area chosen, the more power is required per unit reactor volume. Analysis shows that not only the attainable conversion but also the yield can be greatly influenced by the volume-specific mass transfer area. This applies both to parallel and to consecutive reactions. In the case of consecutive reactions, the liquid retention time must also be included as a parameter in yield determination. If a reactor system requires economic optimization, then, in addition to the yield, the power required for mixing and the investments in reactor volume are also of importance. All three parameters can be modified by means of quantities accessible to the engineer, such as gas throughput, specific power dissipation, and residence time. The quantitative relations depend upon reactor type. The relation between these parameters can be plotted quantitatively in a working diagram for each reactor type. Its plotting and use in reactor optimization on the bases of laboratory experiments are considered.
27 citations
TL;DR: A survey and selection criteria for industrial liquid/liquid extractors is presented in this article, with emphasis being laid on a description of the apparatus and the problems met with in their practical application; theoretical considerations are largely avoided.
Abstract: Modern liquid/liquid extractors – survey and selection criteria. Various types of industrial extractors are presented with emphasis being laid on a description of the apparatus and the problems met with in their practical application; theoretical considerations are largely avoided. An attempt is made to categorize and assess individual extractors. For this purpose the efficiencies and loadings are given, which enable a rough comparsion to be made since such data are very strongly dependent in the properties of the substances to be processed. A scheme taking into consideration the most important parameters and based on available experimental results and operational experience simplifies the task of preselection of a suitable extractor for a new seperation problem. Final choice and design of extractor to be used under particular conditions are possible only by experiment.
24 citations
TL;DR: Stability and dynamics of Reactors with Heterogeneously Catalyzed Reactions are reviewed in this article, highlighting the physical and chemical causes of the observed phenomena, and the state-of-the-art state of the art can be found here.
Abstract: Stability and Dynamics of Reactors with Heterogeneously Catalyzed Reactions. Our knowledge of causes and consequences of problems arising from instability and dynamic effects in reactors with heterogeneously catalyzed reactions has increased remarkably in recent years. Especially thermal effects, caused by the self-acceleration of an exothermic reaction in combination with heat and mass transport, are now well unterstood. In addition kinetic effects, i. e. phenomena which have to be explained by the kinetic peculiarities of surface reactions, have attracted increasing interest. For both cases the state of the art will be reviewed, highlighting the physical and chemical causes of the observed phenomena.
24 citations
TL;DR: In this article, a general two-phase model that is valid for fast reactions has been developed and its validity is confirmed by comparison with the experimental results obtained by other authors, and its use is illustrated with the aid of design diagrams.
Abstract: Mathematical modelling of fluidized bed reactors. Among the many fluidized bed models to be found in the literature, the two-phase model originally proposed by May has proved most suitable for accommodation of recent advances in flow mechanics: this model resolves the gas/solids fluidized bed into a bubble phase and a suspension phase surrounding the bubbles. Its limitation to slow reactions is a disadvantage. On the basis of the analogy between fluidized beds and gas/liquid systems, a general two-phase model that is valid for fast reactions has therefore been developed and its validity is confirmed by comparison with the experimental results obtained by other authors. The model describes mass transfer across the phase interface with the aid of the film theory known from gas/liquid reactor technology, and the reaction occurring in the suspension phase as a pseudo-homogeneous reaction. Since the dependence of the performance of fluidized bed reactors upon geometry is accounted for, the model can also be used for scale-up calculations. Its use is illustrated with the aid of design diagrams.
23 citations
22 citations
21 citations
21 citations
TL;DR: In this article, a model for describing growing, decomposing, and steady-state dispersions is presented, which is used for predicting growth and decomposition rates in good agreement with experiment.
Abstract: Coalescence in vertical close packed dispersions. Models are presented for the description of growing, decomposing, and steady-state dispersions. They contain the velocity of the dispersed phase V0, the initial drop diameter Φ0, the hold-up e, and the coalescence times between the drops τ and at the free interface, τi. The height H of a steady-state dispersion is calculated from the equation
The values of τ and τi were determined experimentally for two liquid/liquid systems with the use of a model of a steady-state dispersion and used for predicting growth and decomposition rates in good agreement with experiment.
TL;DR: The liquid-membrane technique is a promising extraction process as mentioned in this paper, which is the name given to a simultaneous extraction/stripping process by means of a selective liquid phase (liquid membrane) separating two other miscible liquids (solvent, extract phase).
Abstract: The liquid-membrane technique – a promising extraction process. The liquid-membrane technique is the name given to a simultaneous extraction/stripping process by means of a selective liquid phase (liquid membrane) separating two other miscible liquids (solvent, extract phase). This review attempts to summarize the present applications of the liquid-membrane technique, pointing out the scope and limitations of this membrane process. No industrial application of the liquidmembrane technique is yet known. Nevertheless some applications have been suggested or claimed as patents, for example the removal of weak acids such as phenol from waste water, the separation of ethylene and methane, the concentration of ions with the aid of carriers in the liquid membrane and catalytic gas/liquid oxidations (oxidation of ethylene to acetaldehyde). Further proposed applications are in the field of medical technology (artificial systems for organ assistance or replacement). The summary of applications of the liquid-membrane technique is preceded by a general discussion of the physical properties of liquid membranes and the relevant mass transfer mechanisms for a better understanding of this novel technology.
TL;DR: In this paper, the authors described the mode of action of the new three-way catalysts in detail and the present trends in development of multifunctional automotive exhaust catalysts are outlined.
Abstract: Mode of action and characterization of multifunctional automotive exhaust catalysts. Because of the pending reduction in permissible concentration of toxic components in automotive exhausts the catalysts presently available will have to be replaced by more efficient systems. For these “second generation” catalysts multifunctional platinum/rhodium based catalysts are in the course of development, with provision being made for control of the fuel/air mixture. The new catalysts destroy both NOx as well as carbon monoxide and hydrocarbons and are effective in the neighbourhood of the stoichiometric composition of the fuel/air mixture. The mode of action of the new “three-way” catalysts is described in detail and the present trends in development are outlined.
TL;DR: In this paper, an attempt is made to maintain the same product properties, especially the porosity and size of the agglomerates, on scale-up of the granulating equipment.
Abstract: Disign of granulating plates and granulating drums. Equations relating mechanical and geometrical parameters have been derived for use in calculating the power requirements of granulating plates and granulating drums. An attempt is made to maintain the same product properties, especially the porosity and size of the agglomerates, on scale-up of the granulating equipment. This condition considerably limits the possible operational parameters. In order to define the operating conditions on scaling-up from model experiments, their influences are described in terms of theoretical models and empirical results. The utility of the expressions derived is illustrated using the design of a granulation plate as example.
TL;DR: In this article, a purely stochastic approach of the pore structure of the catalyst was adopted, and a more fundamental approach was developed on the basis that deactivation occurs by site coverage and pore blockade.
Abstract: In the mathematical modeling of deactivation by coke formation, the initial rate of the main reaction(s), r/sup 0/A, is multiplied by a deactivation function, phiA, while the rate of the coking side reaction(s) is multiplied by a deactivation function, phiC, to yield the actual rates on the coked catalyst. So far, the deactivation functions phiA and phiC were empirically related to the coke content of the catalyst (3) or to process time (4). In this work a more fundamental approach is developed on the basis that deactivation occurs by site coverage and pore blockade. A purely stochastic approach of the pore structure of the catalyst will be adopted.
TL;DR: In this article, the principal methods of measuring convective transfer of momentum, heat, and mass are surveyed on the basis of the threefold analogy existing between the transfer between the convective mass, heat and mass, and the most simple and sensitive method is the mass transfer technique based on the principle of absorption with chemical reaction and coupled colour reaction.
Abstract: Methods of measuring convective mass transfer. The principal methods of measuring convective transfer of momentum, heat, and mass are surveyed on the basis of the three-fold analogy existing between the transfer of momentum, heat, and mass. The most simple and most sensitive method is the mass transfer technique based on the principle of absorption with chemical reaction and coupled colour reaction. It is shown by selected examples that this measuring technique is already developed to the point where it serves adequately for the solution of most complex problems met with in practice. It is distinguished by its high accuracy of measurement, simple application, high local resolution, and its utilizability both for developable as well as for undevelopable surfaces. By way of the local mass transfer observable as colour-intensity distribution it also affords a simple and illustrative means of making flow processes on solid surfaces visible. The quantitative evaluation is accomplished by reflectance photometry; quantitative image processing methods are available for complex distributions. In addition, it is shown that the mass transfer technique is also suitable for practical utilization as a method for measuring turbulence. The measuring principle is based on the extremely high dependence of the length of transitional separation bubbles in the nose section of flat plates of finite thickness in longitudinal flow on the turbulence intensity.
TL;DR: In this article, the pyrolytic techniques developed especially for producing smelting coke from coal and in petroleum refining can be applied to the thermal decomposition of waste materials having a high organic content.
Abstract: Pyrolytic recovery of raw materials from special wastes. The pyrolytic techniques developed especially for producing smelting coke from coal and in petroleum refining can be applied to the thermal decomposition of waste materials having a high organic content. Fluidized bed reactors and rotary kilns are particularly suitable as universally applicable pyrolysis units for continuous operation. Highly aromatic pyrolysis oils for use as chemical raw material, heating gases for the autothermic operation of the pyrolysis unit, and carbon and solids containing nonferrous metals are obtained from plastics waste, used tires, old cable, shredder wastes, and acid resins at reactor temperatures of about 700°C. Largescale applicability and economics of the process have yet to be proved.
TL;DR: In this article, the development and planning of plant for the high-pressure extraction of natural products is discussed, and the thermodynamic aspects are dealt with in more detail and ways of optimizing a large-scale plant and reducing the power consumption are outlined.
Abstract: Development and planning of plant for the high-pressure extraction of natural products. Important criteria in the designing of plant for the recovery of carrier or extract are reviewed, especially for the extraction of natural products with supercritical CO2. The quantities to be determined in the planning of a large-scale plant are outlined and a typical process, the extraction of spices, is discussed in detail. The plant components and assemblies are presented together with their particular process engineering and construction characteristics. Finally, the thermodynamic aspects are dealt with in more detail and ways of optimizing a large-scale plant and reducing the power consumption are outlined. Particular attention is paid to the question of optimization regarding the most economic method of operation of such a plant in the future.
TL;DR: Theoretical and experimental concept of heat and mass transport in liquid pool flames is reviewed in this article. But, the authors do not consider the effect of temperature, heat radiation, and concentration on the dynamics of pool flames.
Abstract: Heat and mass transfer in pool flames. Theoretical and experimental concept of heat and mass transport in liquid pool flames are reviewed. The heat and mass transfer processes in the interface between flame and liquid fuel are outlined, and the concept of the burning rate as a parameter for the quantitative description of a pool fire is discussed. The methods of calculation and experimental results concerning flame length and flame shape as well as buoyancy forces are described. In pool flames, a lower region (flame neck) and an upper region (flame plume) are distinguishable. Both the flame neck and the flame plume show a flow pattern obtained from short or long periods of observation. The flow patterns of the flames have been measured by the techniques of equidensitometry and Laser-synchronous-interferometry. The flow pattern observed over a short period of time gives an insight into the eddy field of the pool flame whose turbulence is measured. The flow pattern observed over a long time is obtained from time averaged values of temperature, heat radiation, concentration etc.
TL;DR: In this article, the authors consider the practical implications of adsorption of electrolyte ions on electrodes and methods for quantitative determination of electrosorption, and show that surface-active neutral compounds and lyophobic ions are most strongly adsorbed in a narrow potential range around the zero point.
Abstract: Adsorption of ions on electrodes in aqueous and nonaqueous electrolytes. This article considers the practical implications of adsorption of electrolyte ions on electrodes and methods for quantitative determination of electrosorption of ions. Adsorbed ions influence the potential drop in the inner Helmholtz layer and thereby modify the rate of charge transfer for redox processes occurring at electrodes, and the chemical reactions ensuing upon charge transfer can be effectively directed by adsorbed ions. Corrosion and its inhibition as well as deposition of metal in electroplating can be influenced by surface-active ionic additives which are adsorbed. Measurement of differential capacity provides information about the electrosorption of ions and neutral compounds. A knowledge of the zero point of the electrode metal permits clear predictions concerning ion adsorption. Anions are preferentially adsorbed at potentials on the anodic side of the zero point, and cations at potentials that are more negative than the zero point. Surface-active neutral compounds and lyophobic ions are most strongly adsorbed in a narrow potential range around the zero point. Adsorption of weakly solvated ions on hydrophobic metals (e. g. Au, Hg) is more pronounced than the adsorption of strongly solvated ions on hydrophilic metals (e. g. Ga, Cd, Zn).
TL;DR: Ionic conduction in solids has numerous potential applications in the fields of instrumentation, energy storage, energy conversion, and production of chemicals as mentioned in this paper, and the present state of development of various processes and devices ranges from industrial maturity via application tests and R&D work to projects in the concept stage.
Abstract: Applications of solid state electrolytes – a survey. Ionic conduction in solids has numerous potential applications in the fields of instrumentation, energy storage, energy conversion, and production of chemicals. The present state of development of the various processes and devices ranges from industrial maturity via application tests and R & D work to projects in the concept stage. The state of the art is briefly reviewed.
TL;DR: In this paper, the effects resulting from superposition of reaction and distillation are demonstrated for a few examples and the industrial exploitation of such a system is illustrated, in comparison to the processes in actual distillation columns are extremely complex and it is therefore advantageous in industrial engineering design to have suitable mathematical models at hand.
Abstract: Reactions in distillation columns. Reaction columns are an interesting alternative for numerous reactions, and they have often proved economically advantageous. The effects resulting from superposition of reaction and distillation are demonstrated for a few examples and the industrial exploitation of such a system is illustrated. In comparison to the processes in actual distillation columns the processes in reaction columns are extremely complex. It is therefore advantageous in industrial engineering design to have suitable mathematical models at hand. Control problems can be overcome by profile control or by dynamic detectors.