bluuebunny/crossref_metadata_2025_split huggingface dataset:
Continuous deasphalting of heavy petroleum residues with ethyl acetate
Authors: Höucker Jürgen , Vogelpohl Alfons 
Published: August 2005

AbstractWhen crude oil is vacuum distilled, about 30% of the feed remain as low value residue. Hydrocracking can upgrade this residue into valuable light hydrocarbons. The hydrocracking could be optimized catalytically, if the residue were not to contain the metals vanadium and nickel that poison the catalyst. This contribution shows that continuous extraction of the residue with ethyl acetate yields a fraction with low metal content, while an asphaltene fraction with the remaining metal content is filtered off.
Simulation of fluid dynamics in a pulsed sieve plate column
Authors: Haverland Hartmut , Vogelpohl Alfons , Gourdon Christophe , Casamatta Gilbert 
Published: August 2005

AbstractThe 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.
DIVA – a flow‐sheet oriented dynamic process simulator
Authors: Marquardt Wolfgang , Holl Peter , Gilles Ernst Dieter , Butz Dieter 
Published: August 2005

AbstractThe detailed dynamic simulation of coupled process units in chemical plants is gaining an increasing importance as a useful tool in plant engineering and operation. The outline of the program package DIVA (Dynamische Simulation verfahrenstechnischer Anlagen) which is currently under development is presented in the following. The dynamic plant equations and the corresponding Jacobian matrix are generated automatically. The full exploitation of sparse matrix techniques in combination with stiff ODE (ordinary differential equation) solvers allows an efficient solution of all the equations simultaneously. The possibilities offered by the simulator are demonstrated by the simulation of two laboratory plants.
Contact‐free measurements of oxygen concentration in industrial flames by raman scattering
Authors: Leipertz Alfred , Haumann Jürgen , Fiebig Martin 
Published: August 2005

AbstractSpatially resolved oxygen concentration measurements were performed in premixed hydrocarbon flames by using laser induced spontaneous Raman scattering. The measurements demonstrate the performance of a relatively simple pulsed laser Raman probe for fundamental combustion studies and also for the control of the equivalence ratio in flames (best spatial resolution: 0.2 mm3; theoretical detection limit: 0.8% of O2). Comparison of the results with those obtained by a mechanical suction probe (Magnos 2 T) confirmed a good agreement. At present, control of different stoichiometric conditions is possible at a minimum O2 concentration of 1.3%.
Oxygen and methane enrichment — a comprison of module arrangements in gas permeation
Authors: Rautenbach Robert , Dahm Wolfgang 
Published: August 2005

AbstractIn 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.
Flow‐induced vibrations of tube arrays in cross‐flow
Authors: Troidl Hubert , Strohmeier Klaus 
Published: August 2005

AbstractExisting heat exchanger design criteria do not satisfy the continually increasing requirements for greater efficiency or mass flux and energy throughput. Occasionally, failures appear even after only a few hours of operation, as shown in section 3. A long series of experiments, often carried out on original scale, did lead to the derivation of a large number of empirical expressions; however, physical explanations of the complex tube‐failure interactions could not as yet be found. In contrast, experiments with a well defined simple model, whereby the tube deflections were recorded digitally and, at the same time, tube‐fluid interactions were registered on a high‐speed film, show that elementary “fluid transport mechanisms” control the stability behaviour of the heat exchanger tubes. Vibration excitation mechanisms such as “galloping”, “jet switching” and “whirling” (fluid elastic coupling) proved, with their characteristics, as typical for the vibration behaviour of single rows within the tube array, but not for the vibration phenomena of tube bundles.
Conversion of organic oxygen compounds and their mixtures on H‐ZSM‐5
Authors: Fuhse Jürgen , Bandermann Friedhelm 
Published: August 2005

AbstractThe 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.
Comparison of performance of an industrial VGO‐treater with reactor model predictions
Authors: Döhler Werner , Rupp Martin 
Published: August 2005

AbstractA 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.
Kinetic studies on catalytic methanation by means of a concentration‐controlled recycle reactor
Authors: Löwe Arno , Tanger Uwe 
Published: August 2005

AbstractThe rate behaviour of multi‐step reaction systems is difficult to model. Concentration‐controlled investigations in a recycle reactor provide new tools for this purpose, e.g. the possibility to decompose a network into single reaction steps. Methanation of carbon monoxide over a supported Ni catalyst could be shown to be accompanied to a considerable extent by the shift reaction, and to a lesser extent by direct hydrogenation of carbon dioxide. Deactivation of the catalyst was measured at definite gas compositions. The two main steps show different responses to deactivation: Separable kinetics was found only for the methanation step. Power law rate equations were fitted to the rate data of the individual reaction steps to represent the main features of their kinetic behaviour. Some aspects of deactivation kinetics are also discussed.
A differential model for a countercurrent extractor column with non‐constant flow rates, interfacial area per unit volume and axial dispersion coefficients
Authors: Cornelissen A. E. , Grievink J. , Toneman L. H. 
Published: August 2005

AbstractIn the extraction literature, no attention has been given so far to differential calculation models for countercurrent extraction columns which take into account the changes in flow rates of the phases as a result of transferred mass, and which also reflect the variations in interfacial area per unit volume and in axial dispersion coefficients since these depend on the flow rates. The present contribution puts forward a formulation of such a model; this results in a set of non‐linear differential equations with separated boundary conditions, representing the feeds at either side of the extraction column. This set of differential equations must be solved numerically. The model is illustrated by a sample calculation on the extraction of benzene with furfural. In this (realistic) example, the interfacial area per unit volume varies from bottom to top by a factor of 3. Ignoring this effect would obviously result in serious under‐ or overdesign.
A model for the rate of catalytic oxidation of methanol in a fixed bed reactor
Authors: Sohrabi Morteza , Dabir Bahram , Mozaffari Farhad 
Published: August 2005

AbstractOxidation of methanol to formaldehyde, using a mixture of ferric and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 150 mm long, 25 mm o.d. and 10 mm i.d. The catalyst was prepared by reaction between aqueous solutions of ammonium heptamolybdate and ferric chloride. It has been shown that, under experimental conditions similar to those employed in industry, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A two‐step mechanism has been put forward for the oxidation of methanol. According to such a mechanism, methanol is first oxidized to formaldehyde, accepting an oxygen molecule from the catalyst and changing the latter into a reduced form. In the second step, the reduced catalyst is transformed into the original form on obtaining an oxygen molecule from the gas phase. Based on this scheme, a rate model has been derived and verified by experimental results.
An improved method for flow network design
Authors: Lin Sheng H. 
Published: August 2005

AbstractAn improved method is presented for the design of a complex flow network system. The method employs head loss and flow rate in the iteration process for the determination of flow rates and/or pressure drop. This represents a major departure from the conventional approach which uses only the flow rate. The two‐step iteration method proposed here drastically improves both the convergence rate and iteration stability. Tests on different examples have shown that, for most design applications, three iterations are sufficient to yield an accurate final solution, regardless of the initial guess.
Application of dynamic programming to high‐dimensional systems described by difference equations
Authors: Luus Rein , Smith Stephanie G. 
Published: August 2005

AbstractThe application of dynamic programming using an interative procedure, which employs domain contraction and accessible grid points for the state vector, is investigated for solving optimal control problems where the system is described by a set of difference equations. A model of a gas absorber with six state variables and two control variables is used to examine the feasibility of the proposed algorithm and to analyze the effects of the grid size and of the domain contraction factor. This algorithm yields rapid convergence to the optimum even when a relatively coarse grid with as few as 11 grid points is used.
A new process for indirect gas supply by means of perfluorinated polyethers
Authors: Schäfer Hans , Bayer Thomas , Buchholz Rainer , Kühlein Klaus , Schlingmann Merten , Wullbrandt Dieter 
Published: August 2005

AbstractA new process has been developed for indirect gas supply for culturing shear sensitive cells by means of a perfluorinated hydrocarbon. Hostinert 216, a perfluorinated polyether, was used as oxygen and carbon dioxide carrier. Hydrodynamics and mass transfer, required for industrial implementation, were investigated in a drop column. Based on the knowledge, obtained with indirect gas supply, it has been possible to construct a waste‐gas free sterile pilot plant. Correlations derived from performed measurements permit design of and scale‐up to an industrial plant.
Studies of drop break‐up in liquid‐liquid systems in a rotating disc contactor. Part II: Effects of mass transfer and scale‐up
Authors: Bahmanyar Hossein , Dean D. Roy , Dowling Irena C. , Ramlochan Kenrick M. , Slater Michael J. , Yu Wei 
Published: August 2005

AbstractThe number fraction of drops of a given size which break up at rotor level in a rotating disc contactor has been observed during mass transfer in either direction to or from solvent or aqueous drops. Critical rotor speeds for a given drop size undergoing mass transfer can be used to find an effective interfacial tension. Using this interfacial tension value, the break‐up fractions are correlated within experimental uncertainties in the same manner as for no mass transfer. Drop break‐up fractions depend on column size and relevant empirical correlations of the data are presented. The results may be used to estimate the effect of mass transfer on drop size distributions in an RDC.
Three‐component mass transfer in liquid‐liquid extraction with the system glycerol‐acetone‐water. Part 1: The influence of vanishing diffusion coefficients in binodal states on the mechanisms of mass transfer
Authors: Schermuly Wolfgang , Blass Eckhart 
Published: August 2005

AbstractThis contribution deals with the consequences of the decrease in diffusion coefficients at the boundaries of miscibility in fluid systems and its effect on the mechanisms of mass transfer. The liquid‐liquid (1–1) extraction involving several components is taken as an example for the discussion of this topic. A short review of Hampe's theory on transport mechanisms in the transition regions of interfaces [1] explains the intrinsic interdependence between mass and momentum transfer. Finally, a discussion of the peculiarities of resistances to mass transfer in boundary layers, based on the changes in molecular transport properties, is presented.
Influence of intraparticle total pressure change on pore mass transport
Authors: Scholl Stephan , Mersmann Alfons 
Published: August 2005

AbstractInfluence of intraparticle total pressure change on pore mass transport is investigated in physical gas phase adsorption of a single component from an inert carrier medium. The Dusty Gas Model is applied to quantify pore mass transport, assuming local equilibrium between pore fluid and adsorbed phase. Calculated results for single pellet adsorption kinetics of cyclohexane on activated carbon and CO2 on molecular sieve 5 Å are compared with experimental data. It is found that the total pressure drop in the pore system may be as much as 1% of the ambient total pressure. This results in a maximum viscous flow contribution of 13% for the cases studied. Since this contribution is obtained only under conditions of low overall transport rates of the adsorbed component, the assumption of isobaric conditions within the pore system of a porous adsorbent appears justified for most cases of practical calculations.
Role of sparger design in mechanically agitated gas‐liquid reactors. Part II: Liquid phase mixing
Authors: Rewatkar Vilas B. , Joshi Jyeshtharaj B. 
Published: August 2005

AbstractLiquid phase mixing time was measured in 0.57, 1.0 and 1.5 m i.d. mechanically agitated gas‐liquid reactors. Transient conductivity technique was used for the mixing time measurement. Pitched blade downflow turbine was employed. The design details of PTD impellers such as diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.35 D) were studied. The influence of sparger types and their design on mixing time has been investigated. For this purpose, pipe, ring, conical, and concentric ring spargers were employed. The design details of the ring sparger, i.e. ring diameter, number of holes and hole size were also studied in depth. Sparger location with respect to the impeller was found to be the most important variable and, therefore, it was varied for practically all the spargers studied in this work. It was found that the liquid phase mixing time depends on the impeller design, sparger design, sparger location, impeller speed and superficial gas velocity. Correlations have been developed for the dimensionless mixing time.
Equilibrium model for CO2 absorption in an aqueous solution of 2‐amino‐2‐methyl‐1‐propanol
Authors: Erga G. Olav , Lidal Håvard 
Published: August 2005

AbstractA semi‐empirical gas‐liquid equilibrium model for the absorption of CO2 in aqueous 3M AMP (2‐amino‐2‐methyl‐1‐propanol) is presented. It applies to high CO2 loadings (y > 0.5) in the temperature range between 20 and 50 °C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO2 as a function of only two variables: the CO2 loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: p = m y × 10x, where p is the equilibrium partial pressure, x = logK ‐ pH, m is the amine molarity, y the CO2 loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K1, of carbonic acid. pH is found to depend on both temperature and CO2 loading while logK depends only on the CO2 loadIng. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.
Hydrodynamics in a pressurized cocurrent gas‐liquid trickle‐bed reactor
Authors: Wammes Wino J. A. , Westerterp K. Roel 
Published: August 2005

AbstractThe influence of gas density on total external liquid hold‐up, pressure drop and gas‐liquid interfacial area, under trickle‐flow conditions, and the transition to pulse flow have been investigated with nitrogen or helium as the gas phase up to 7.5 MPa. It is concluded that the hydrodynamics depends on the gas density and not on the reactor pressure. At higher gas densities, the operating region for trickle flow becomes larger while the gas‐liquid interfacial area increases only slightly. Pressure gradient and liquid hold‐up are considerably affected by gas density and correlations have been derived for these parameters.
Effect of thermal pretreatment and reduction on acidity and metal state in doped NiH and CuH mordenites
Authors: Exner Herbert , Fetting Fritz 
Published: August 2005

AbstractThermal pretreatment such as calcination and steaming as well as the reduction of cations by hydrogen, affect the zeolitic acidity and activity of nickel‐ and copper‐doped mordenites in heterogeneously catalyzed reactions such as the conversion of n‐hexane. Data on acidity changes were obtained by IR spectroscopy, and information on ionic and metallic states by temperature‐programmed reduction, CO chemisorption and transmission electron microscopy (TEM). The findings were compared with reaction results from conversion of n‐hexane. Trimethylamine (TMA) was selected as a standardization molecule for semi‐quantitative determination of acidity. Correlation of relative acidity values with experimental results was possible only to a very limited extent. Results of CO chemisorption, TPR and TEM allow conclusions to be drawn on metallic crystallites, Ni+ and Cu+ ions and clusters, which appear to exert a stabilizing influence on zeolitic activity. Nickel crystallites with d > 2 nm catalyze both hydrogenation and dehydrogenation of paraffins on the metal in bifunctional catalysis, as was also observed on platinum‐doped zeolites.
Heat, mass and momentum transfer in packed bed distillation columns
Authors: Karlström Anders , Breitholtz Claes , Molander Mats 
Published: August 2005

AbstractThis contribution presents the basic equations for heat, mass and momentum transfer in multicomponent packed bed distillation processes. In some situations, the use of strongly simplified models is justified, but when approaching more difficult and, at the same time, economically more interesting regions of operation where non‐linear effects are significant, these models are likely to fail. Consequently, a more rigorous vapour‐liquid equilibrium model should be employed since the pressure drop in the column will not be negligible in those regions. Furthermore, neither constant parameter hold‐ups nor heat and mass transfer coefficients are assumed. Simulations demonstrate some interesting process properties. The impact of the surroundings on the process is discussed and a three‐dimensional model extension is outlined.
On the permeability of binary packings of spheres
Authors: Andrade José S. , Rajagopal Krishnaswamy , Benyahia Farid , Foumeny Esmail A. , McGreavy Colin 
Published: August 2005

AbstractMacroscopic flow properties of packed beds are strongly dependent on the structure of the pore space. In the case of permeability, the classical approach in which this coefficient is related to the mean voidage cannot be systematically applied as a predictive methodology, because the mean voidage index does not account for the morphology and topology of the porous media. In this work, a modelling technique is developed which enables the effective permeability of a binary packing of spheres to be evaluated from a detailed structural and phenomenological description of the system. The results are then compared with experimental data to confirm the predictive capability of the model.
Investigations on increasing safe gas volumetric flow rate through a water trap flame arrester
Authors: Rubach Torsten , Schecker Hans‐Georg , Jäger Walter Rudolf , Onken Ulfert 
Published: August 2005

AbstractIn the process industries, safety problems may arise when combustible gases are transported through pipes. Therefore, it is necessary to prevent propagation of flame fronts into or through systems, in order to avoid undesired explosions and flashbacks into the production plant. Safety devices which are used in such cases are the flame arresters, e.g. water trap flame arresters. There is a maximum gas flow rate through a water trap flame arrester below which a flashback is unlikely to occur. Based on investigations of the explosion behaviour of bubbles in suspensions of glass spheres, experiments were carried out in a water trap flame arrester of industrial demensions. It is shown that the safe gas volumetric flow rate through a water trap flame arrester can be increased by up to 30% for H2/air mixtures when glass spheres are added to the liquid in the flame arrester.