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Showing papers in "Chemical Engineering & Technology in 1987"


Journal ArticleDOI
TL;DR: In this article, a distillation column with a vertical partition is proposed to separate a feed mixture into 3 or 4 pure fractions, where the internal separation wall prevents lateral mixing of liquid and vapour in the central part of the column, forming separate feed and outlet sections.
Abstract: Distillation columns with vertical partitions can separate a feed mixture into 3 or 4 pure fractions. Compared to other column arrangements, their investment costs and energy consumption are lower. Production columns show good results and are easily controlled. Conventional distillation columns produce only 2 pure product streams at the top and at the bottom of the column. Side products are contaminated by light or heavy components, depending on the location of the side stream in the rectifying or stripping section. This disadvantage is set aside by using a distillation column with a vertical partition. The internal separation wall prevents lateral mixing of liquid and vapour in the central part of the column, forming there separate feed and outlet sections. In the presence of a vertical partition, 3 or 4 pure fractions can be obtained in a single distillation step. This is particularly advantageous when heat sensitive components are to be separated. On account of good thermodynamic properties, the energy consumption is 20 to 35% lower than that of other distillation arrangements. The control behaviour is similar or better than that of conventional distillation columns.

297 citations


Journal ArticleDOI
TL;DR: In this paper, a physical model for the description of fouling, caused by sedimentation and crystallization, is presented, in order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments.
Abstract: Fouling and/or scaling of heat transfer surfaces causes serious problems in industry. Prevention of fouling is therefore essential for technical (considerable deterioration of heat transfer) and also economic reasons (increased costs). In order to provide successful countermeasures, it is, however, necessary to obtain more detailed information on the physical, chemical and biological processes which produce fouling. Based on the already known fouling mechanisms, it is shown that a satisfactory prediction of fouling behaviour of heat exchangers is not yet possible. This contribution presents a physical model for the description of fouling, caused by sedimentation and crystallization. It is assumed that, during fouling, deposition and removal processes overlap. In order to verify the theoretical considerations, experiments were carried out on a test rig, which could also be used for field experiments. Aqueous CaSO4 solutions served as experimental liquids. A comparison of experimental and calculated fouling factors shows a satisfactory agreement.

211 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed a simplified process design for the production of hydrogen at high temperatures in a steam reforming of natural gas, where the hydrogen discharge is directly in the reformer tube, resulting in more favorable process conditions and, consequently, in improved by 36% utilization of the feed hydrocarbons.
Abstract: The development of heat resistant permeation membranes has opened up new possibilities for the conversion of fossil energy resources. In steam reforming of natural gas, such membranes even permit a direct production of hydrogen at high temperatures during the conversion of feed hydrocarbons. Further gas processing, such as required for reformer gas in existing hydrogen production processes, is not necessary. Due to continuous hydrogen discharge directly in the reformer tube, the chemical equilibrium of the occurring reactions becomes displaced towards the products, resulting in more favourable process conditions and, consequently, in improved by 36% utilization of the feed hydrocarbons. At the same time, the hydrogen yield increases by 44%. The heat required, which is provided by a high temperature reactor, is 17% in excess of that in conventional plants. It can be expected that the simplified process design will produce substantial cost advantages over the existing processes for the production of hydrogen.

127 citations


Journal ArticleDOI
TL;DR: Mesure des effets des particules solides sur les caracteristiques de fluidization, de la retenue de gaz, and du coefficient de transfert de masse volumetrique (pour la phase liquide) dans une colonne a bulle contenant des particles en suspension as mentioned in this paper.
Abstract: Mesure des effets des particules solides sur les caracteristiques de fluidisation, de la retenue de gaz, et du coefficient de transfert de masse volumetrique (pour la phase liquide) dans une colonne a bulle contenant des particules en suspension. Le diametre et la densite des particules est similaire a celle que l'on peut avoir en biotechnologie avec des bacteries immobilisees. Basees sur des modeles de turbulence et sur une circulation induite par l'ascension de bulles de gaz, on obtient, par analyse dimensionnelle, la vitesse critique du gaz, la retenue de gaz et le coefficient de transfert de matiere volumetrique pour la phase liquide

45 citations


Journal ArticleDOI
TL;DR: In this paper, the authors developed models for the description of coalescence and splitting of bubbles in gas fluidized beds and showed that a change in bed temperature does influence the mechanisms of bubble coalescence.
Abstract: In the present paper, models are developed for the description of coalescence and splitting of bubbles in gas fluidized beds. The distinction between slow and fast bubbles, which originates from the Davidson model of gas flow in and around a rising bubble, was found to be decisive for the modelling of coalescence processes. On the basis of the respective models, it is shown that a change in bed temperature does influence the mechanisms of both bubble coalescence and splitting. In cases of both slow and fast bubbles undergoing splitting, the theory predicts a decrease of bubble size with temperature whereas in the case of a non-splitting system with fast bubbles, typically encountered with Geldart type B particles, no significant temperature effect on bubble size is expected. The theoretical predictions are shown to be in agreement with own measurements as well as with the results of other workers.

38 citations


Journal ArticleDOI
TL;DR: In this article, a distinction is made between macro and micromixing processes, and it is shown that the real flow conditions are necessary to consider in these cases, in order to avoid deviations from the ideally calculated conversions, yields and product qualities.
Abstract: Ideal flow conditions are generally assumed for the reactor design. If stoichiometry, reaction mechanism and kinetics are known, the balance equations for the ideal flow tube, the ideal steady-state continuous stirred tank reactor or the ideal, completely mixed stirred batch reactor are often applied. In many cases, formal kinetics, which forms the basis of reaction modelling, is so uncertain that the idealization of the flow field can be accepted. In practice, however, deviations from the ideally calculated conversions, yields and product qualities, often occur. In these cases, it is necessary to consider the real flow conditions. In general, a distinction is made between macroand micromixing processes.

36 citations


Journal ArticleDOI
TL;DR: In this article, the conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H-ZSM-5 at 673 K was investigated.
Abstract: The conversion of a number of alcohols, ethers, ketones, aldehydes, carboxylic acids, esters, and cyclic compounds and their mixtures on H-ZSM-5 at 673 K was investigated. These compounds can be easily converted to aromatic hydrocarbons if the C/H ratio of the molecule fragment, remaining after elimination of oxygen as water, is less than 0.62. At higher C/H ratios, coking of the catalyst increases, thus reducing its lifetime, a difficulty which can be overcome by hydrogenation of these compounds prior to their conversion over H-ZSM-5. A procedure is proposed for converting at least a part of organic waste chemicals to valuable products instead of burning them.

32 citations


Journal ArticleDOI
TL;DR: In this article, des essais experimentaux en l'absence de corps a broyer avec des fluides newtoniens sont effectues pour mettre en place des modeles de prediction de la consommation de broyeurs a boulets projetes.
Abstract: Des essais experimentaux en l'absence de corps a broyer avec des fluides newtoniens sont effectues pour mettre en place des modeles de prediction de la consommation de broyeurs a boulets projetes. Des essais de broyage sont aussi realises pour aboutir a des strategies d'extrapolation. L'influence de la taille des corps a broyer est aussi abordee

30 citations


Journal ArticleDOI
TL;DR: In this article, a tentative process scheme is put forward and its economics evaluated with respect to ethylene production with particular emphasis on the oxidative coupling of methane to C2+ hydrocarbons.
Abstract: Against the background of long-term availability of natural gas, its present technology and future prospects are described. Particular emphasis is put on the oxidative coupling of methane to C2+ hydrocarbons: (1) Catalyst development, activity, selectivity and deactivation as well as reactor operation are discussed; (2) a tentative process scheme is put forward and its economics evaluated with respect to ethylene production.

28 citations


Journal ArticleDOI
TL;DR: In this paper, a review of the work performed mainly at Bergbau-Forschung during the past few years is presented, where a method and quantitative data are provided for the calculation of reaction rates for uncatalyzed and potassium-catalyzed gasification, on the example of chars from high volatile bituminous coals.
Abstract: This contribution reviews the work performed mainly at Bergbau-Forschung during the past few years. First, it deals with the quantitative description of gasification kinetics, taking into account the pressure of the gasifying agent and partial pressures of product gases. Thereby, a method and quantitative data are provided for the calculation of reaction rates for uncatalyzed and potassium-catalyzed gasification, on the example of chars from high volatile bituminous coals. In addition, a method for characterization of internal surface area by oxygen chemisorption with respect to char reactivity has been improved. Progress has also been achieved in the assessment of the impact of pyrolysis conditions, especially the time-temperature profile during char formation, on its chemical activity during subsequent use.

24 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the relationship between power consumption and superficial gas velocity in three-phase systems, where the liquid constitutes the continuous phase, solid is the catalyst and gas represents the dispersed phase.
Abstract: In three-phase systems, where the liquid constitutes the continuous phase, solid is the catalyst and gas represents the dispersed phase, there are decisive criteria which have to be observed in reactor design. These are e.g. the interfacial area per unit volume between gas and liquid, the volumetric mass transfer coefficient and the mass transfer coefficient. The basic aim of the present work was therefore the investigation of these parameters in relation to the main influencing parameters. Process parameters stirrer speed and superficial gas velocity were varied as well as the physical properties such as liquid viscosity, solids concentration, particle diameter and a geometrical parameter, i.e. reactor diameter. The sulphite method was employed for the determination of these values. The test results confirmed the known relationships of power consumption and superficial gas velocity. An increase in the liquid viscosity leads to a decrease in all the tested values. In most cases, suspended solid particles lead to a lowering of the test values. The influence of the tank diameter on the plots of the test values against specific power consumption turned out to be invariant so that a scale-up of geometrically similar systems can be carried out at constant power consumption, superficial gas velocity and liquid viscosity.

Journal ArticleDOI
TL;DR: In this article, the mass transfer in liquid pulsed sieve-tray extraction columns (PSE) was studied and the diameters and hold-ups of the drops were measured using a suction technique with photoelectric detection.
Abstract: As a part of a research project on the mass transfer in liquid pulsed sieve-tray extraction columns (PSE), the diameters and hold-ups of the drops were measured: the drop size using a suction technique, with photoelectric detection, which was adapted to the special boundary conditions of the PSE; the integral hold-up by the pressure difference between the lower and upper parts of the column. Since experimental results cannot be described by known calculation formulae for the Sauter mean diameter and the hold-up, a new method of calculation was developed. It is phenomenologically based on high-speed photographs of the drop motion on a sieve tray. The mathematical-physical model allows the prediction of drop size and hold-up within certain limits, while the possible different operating regimes of the PSE, i.e. the mixer-settler and dispersion regimes can also be estimated.

Journal ArticleDOI
Arno Behr1
TL;DR: In this paper, the reactions of CO2 employed in industry, such as the production of urea, the Kolbe-Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO 2 in methanol synthesis, are discussed.
Abstract: Although carbon dixoide is important as an abundant carbonaceous raw material, so far, its utilization in chemical processes has been rather limited. This review covers the reactions of CO2 employed in industry, such as the production of urea, the Kolbe-Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO2 in methanol synthesis. Interesting recent developments in CO2 chemistry, such as the reactions catalyzed by transition metals, are also described. Apart from the synthesis of polymers and hydrocarbons, the production of oxygen-containing substances appears to be very profitable and attractive for future industrial applications. Not only can derivatives of formic and carbonic acids be produced but also longer-chain carboxylic acids and their derivatives by reactions of carbon dioxide with hydrocarbons such as alkynes, alkenes and 1,3-dienes.

Journal ArticleDOI
TL;DR: In this paper, a 0.5 MW spray-dry scrubbing FGD pilot plant was used in the study of spray dryer performance over a wide range of operating conditions.
Abstract: A 0.5 MW spray-dry scrubbing FGD pilot plant was used in the study of spray dryer performance over a wide range of operating conditions. Experimental findings were compared with a spray dryer model. During operation with large excesses of lime, the SO2 absorption was limited by gas phase diffusion. At operation with a shortage of lime, the rate limiting step was the dissolution rate of lime. In addition, the flow regime in a spray dryer can be best described as well mixed. The SO2 level in the flue gas was found to exert no direct effect on the efficiency of SO2 removal. The observed effects are attributed solely to the changes in the drying process, due to the inter-dependence of slurry composition and SO2 concentration.

Journal ArticleDOI
TL;DR: In this article, a simplified reactor model is used for predicting the performance of an industrial VGO-treater based on the results of laboratory-scale experiments performed on the same feed and catalyst as those in the industrial unit lead to a reactor simulation which agrees well with the data from this unit.
Abstract: A simplified reactor model can be used for predicting the performance of an industrial VGO-treater. Laboratory-scale experiments performed on the same feed and catalyst as those in the industrial unit lead to a reactor simulation which agrees well with the data from this unit. In the laboratory experiments, it is possible to overcome the specific hydrodynamic problems of tricklebed reactors by appllying the catalyst dilution technique. Results obtained by this technique allowed the development of a reactor model which enables the user to simulate the adiabatic behaviour of the industrial reactor. In this way, the significant gap between the reaction temperature in the isothermal laboratory reactor and the WABT of the industrial adiabatic reactor can be bridged.

Journal ArticleDOI
TL;DR: In this article, a new method for the simulation of the dispersed phase behavior in liquid-liquid extraction columns is presented, which is based on a mathematical model which explicitly takes into account drop transport, break-up and coalescence mechanisms, via a drop population balance along the column.
Abstract: The present contribution reports on a new method for the simulation of the dispersed phase behaviour in liquid-liquid extraction columns. The fluid dynamic description is based on a mathematical model which explicitly takes into account drop transport, break-up and coalescence mechanisms, via a drop population balance along the column. Application of the model requires some simple measurements on single drops in order to determine transport and break-up laws, which are required by the model, and possibly also coalescence parameters. In this study the model is applied to pulsed sieve plate columns. The specific example considered here is based on systematic studies on the determination of break-up rates from the corresponding probabilities of break-up and the generated daughter drop size distributions by means of high-speed photography. The validity of the model was subsequently tested by comparison with some experimental results from studies on two different pulsed columns 80 and 225 mm in diameter for the water/toluene system without mass transfer. The satisfactory agreement between the results justifies the use of such a method for the description of the behaviour of liquid-liquid extraction columns in a wide range of operating conditions. Furthermore, application of the model may help to dispense with long and expensive pilot tests.

Journal ArticleDOI
TL;DR: In this article, a systematic experimental investigation was carried out in a pilot plant at pressures of up to 100 bar, and the experimental equipment and techniques, evaluation methods, and some characteristic experimental results were presented.
Abstract: Correlations for pressure drop and upper capacity limit (flooding) are useful for the design of packed columns. Available correlations are based on the results of measurements made at atmospheric pressure. Extrapolation to higher pressures is not recommended. Therefore, systematic experimental investigations were carried out in a pilot plant at pressures of up to 100 bar. The experimental equipment and techniques, evaluation methods, and some characteristic experimental results are presented.

Journal ArticleDOI
TL;DR: In this article, the authors presented a way of developing a continuous separation process for near critical fluid extraction, based on the example of separation of soya oil from lecithin.
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.

Journal ArticleDOI
TL;DR: In this paper, a one-stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces.
Abstract: A one-stage model of the formation of primary bubbles is presented in which the bubble volume is deduced from an equilibrium of buoyancy, viscosity, inertia and surface tension forces. In contrast to the two-stage model, presented by Kumar and Kuloor, it was not assumed that the drag coefficient in bubble expansion can be described by the same constants as in the steady-state bubble ascent. The constants were adapted in such a way that the introduction of an additional bubble volume was not necessary. It was demonstrated that this model describes the bubble formation in gravitational and centrifugal fields equally well and, furthermore, is also applicable to structurally viscous liquids, provided that the effective shear gradient is calculated from the equilibrium of shearing and buoyancy forces. The model is based on the assumption of a constant volumetric flow rate during bubble formation and, for this reason, a minimum Froude number is necessary in analogy to the weeping limit for sieve plates. The normalized presentation permits simple operation. The possibility of applying the model to drop formation was confirmed by comparison of experimental values with those, predicted by the model.

Journal ArticleDOI
TL;DR: In this paper, the authors discussed different possible module arrangements for two cases, i.e., the enrichment of oxygen from air and the separation of methane from biogas, and showed that, depending on the selling price of the methane enriched gas, one- or two-stage cascades with recycle have to be considered.
Abstract: In the separation of gaseous mixtures by gas permeation, it is in some cases impossible to achieve the desired product quality in a single stage and, therefore, several stages may be necessary. Multistage processes can be implemented by membrane modules arranged in the form of a cascade or by a membrane column design. On the basis of an economic analysis, this paper discusses different possible module arrangements for 2 cases, i.e. the enrichment of oxygen from air and the separation of methane from biogas. Present calculations indicate that, in the first case, two-stage cascades with or without recycle and, in the second case, one-stage cascade without recycle constitute the optimum module arrangements. However, depending on the selling price of the methane enriched gas, one- or two-stage cascades with recycle have to be considered. Finally, It was shown that, in the permeation of non-ideal gases, the Joule-Thomson effect has to be taken into account.

Journal ArticleDOI
TL;DR: In this paper, the measurements of bubble behavior in presence of A, B and D powders in a semi-industrial scale pressurized fluidized bed were taken at static pressures of 0.2, 1.0 and 2.5 MPa, using capacitance probes.
Abstract: This contribution presents the measurements of bubble behaviour in presence of A, B and D powders in a semi-industrial scale pressurized fluidized bed. Local measurements were taken at static pressures of 0.2, 1.0 and 2.5 MPa, using capacitance probes. Quartz sand with mean particle diameter of 157 μm was fluidized in small “two-dimensional” transparent equipment with Frigen R 115. In addition, pressure fluctuations in the bulk of the fluidized bed with inner diameter of 0.4 m were studied experimentally.

Journal ArticleDOI
TL;DR: In this article, the authors present a calculation method which allows a precise modelling of various pump installations, and a comparison of calculated and experimental data shows a good agreement and provides a validation of the computational model.
Abstract: Pressure pulsations in hydraulic systems, generated by reciprocating pumps, can cause serious problems with regard to plant safety and reliability. In particular, fatigue problems arise in high-pressure piping systems. The available knowledge is not sufficient for an accurate computation of pressure peaks in the piping of reciprocating pumps. A number of calculation models are available which, however, neglect both fluid compressibility and friction. This contribution presents a calculation method which allows a precise modelling of various pump installations. Comparison of calculated and experimental data shows a good agreement and provides a validation of the computational model.

Journal ArticleDOI
TL;DR: In this paper, the authors describe a pilot plant for entrainment measurements on various types of column trays and compare the results with the theoretical model of Stichlmair.
Abstract: This paper describes a pilot plant for entrainment measurements on various types of column trays. The data obtained from different trays differ by up to a factor of 10. The measurements were compared with the theoretical model of Stichlmair. The Stichlmair entrainment diagram permits a fairly accurate prediction for most types of trays if the height of the two-phase layer is known. Prediction of the height and relative liquid hold-up in this two-phase system should be modified by a term reflecting the vapour flow profile, which requires further testing. These tests should examine the effect of tray spacing, fractional free area and, in particular, the influence of different media.

Journal ArticleDOI
TL;DR: In this paper, a simulation dynamique de conception de technique de procede is used to simulate dynamiques de l'installation and les matrices Jacobiennes correspondantes.
Abstract: Le programme utilise est un programme de simulation dynamique de conception de technique de procede. Les equations dynamiques de l'installation et les matrices Jacobiennes correspondantes sont generees automatiquement. Les possibilites offertes par le simulateur sont demontrees en simulant deux installations en laboratoire

Journal ArticleDOI
TL;DR: In this article, a model of coal desulphurization of coal by pyrite oxidizing enrichment cultures containing predominantly Thiobacillus ferrooxidans was performed in an air-agitated slurry reactor, 20 l in volume.
Abstract: Microbial desulphurization of coal by pyrite oxidizing enrichment cultures containing predominantly Thiobacillus ferrooxidans was performed in an air-agitated slurry reactor, 20 l in volume A model of microbiological and chemical reactions, occurring at various points within the coal, was set up taking into account the pore structure of the coal The influence of parameters relevant to industrial processes, such as superficial gas velocity, particle size, initial pyrite concentration, and slurry density of the coal, on the conversion of pyrite was examined Variation of the superficial gas velocity in the range of 001 to 004 m/s confirmed that the reaction is not controlled by oxygen transfer from gaseous to liquid phase The rate of pyrite oxidation depends mainly on the accessibility of pyrite to micro-organisms which is determined by the particle size of the coal as well as the distribution of pyrite crystals in the coal matrix The accessibility of pyrite to the micro-organisms is described by the ratio of effective to maximum microbial activity, measured as oxygen consumption Starting with higher initial concentration of pyrite in the coal increases the oxidation rate, according to first order kinetics Enhanced slurry densities lead to a decrease of pyrite conversion, in spite of higher pyrite concentration The maximum pyrite oxidation rate was measured at 15% (v/v) slurry density and 25°C as 1800 mg Spyr/kg coal per day, or 360 mg Spyr/l reactor volume per day

Journal ArticleDOI
TL;DR: In this article, it was shown that plate efficiency is not very sensitive to liquid channelling on trays, since the liquid is completely mixed in the downcomer and the effects of liquid chanelling are restricted to a single tray.
Abstract: All the present experiments confirm that there is some liquid channelling on trays. Liquid channelling is extensive on trays of large diameters. It largely depends on the tilting of the plate, modifications of the inlet weirs and on non-uniform bubble cap spacing. Consequences of liquid channelling for plate efficiency are clear; the higher the degree of liquid channelling the lower the plate efficiency. However, own experimental and theoretical investigations indicate that plate efficiency never falls below the value of point efficiency. Therefore, liquid channelling only affects the crossflow on trays. Liquid channelling reduces the mass transfer performance to a similar extent as does the backmixing of liquid. Consequently, plate efficiency is not very sensitive to liquid channelling. Since the liquid is completely mixed in the downcomer, the effects of liquid channelling are restricted to a single tray. The behaviour of tray columns completely differs from that of packed columns, where the effects of liquid channelling are cumulative over the packed height. Consequently, trays represent a suitable design for columns of large diameters.

Journal ArticleDOI
TL;DR: In this paper, the influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally.
Abstract: The influence of electrolytes, which are dissolved in the aqueous absorbent and do not react with nitrogen oxides, on the absorption kinetics of both these components was investigated experimentally. In addition to demineralized water, various salt solutions of different concentrations as well as sodium hydroxide solution were used as absorbents. The term H for N2O4 and N2O3, which is important for the design of industrial absorbers, was determined as a function of composition and concentration of the absorbents. In the case of N2O4, the chosen measuring and evaluation methods permitted a separate determination of the rate constant k of the pseudo first order reaction and of the solubility H. The diffusion coefficient D of the gas in the absorbent can be obtained only by calculation. Experimental results showed that decreases with increasing ionic strength I, however, without a clear indication of any ion-specific effects. This decrease does not appear to be caused simply by a reduction in solubility (salting out effect), or in diffusion coefficient, but at least, to the same extent, through a decrease of the rate constant k with increasing electrolyte content in the absorbent. The measurements permitted the determination of the gas-based salting out parameter for N2O4. The investigations on the absorption of N2O3 in water and in an Na2SO4 solution showed no experimentally detectable influence of dissolved salts on . The numerical value of is six times that of .

Journal ArticleDOI
TL;DR: In this article, a new measurement method for determining the local liquid-phase velocities in multiphase flows is presented, based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer.
Abstract: A new measurement method for determining the local liquid-phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat-labelled fluid elements is calculated on-line as a cross-correlation function between the pseudo-random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas-liquid flows at high gas throughputs and high liquid-phase velocities.

Journal ArticleDOI
TL;DR: In this article, a simulation program was developed and employed for the calculation and optimization of methanol-water separation columns, where the number of possible control schemes was reduced on the basis of heuristic rules.
Abstract: For the simulation of steady- and non-steady-state behaiour of separation columns, a simulation program was developed and employed for the calculation and optimization of methanol-water separation. The demand for increasingly higher purities and energy-saving optimization of plants results in complex column configurations and thus in complex control schemes. The number of possible control schemes was reduced on the basis of heuristic rules. By simulating the process, the optimum control and manipulative variables and measuring points were determined from the reduced number of control concepts. A control scheme was introduced. The model was verified by simulation of the dynamic behaviour of the process. The investigation included the effects of computing technique, time interval, model reduction and tray hold-up on the results. Thus, various effects and interactions were verified theoretically with respect to the robustness of the model. This was followed by a simulation of the non-ontrolled and controlled column. By implementing the controllers in the existing column program, the computer can predict the control parameters. These parameters were checked and corrected when the metahnol-ater column was put in operation. In the start-up phase, major problems were caused by the sensitivity and failure rate of density, throughput and pump measuring sensors. Feed impurities were another source of problems. Operation with high product purities is possible, with a side stream to discharge impurities.