bluuebunny/crossref_metadata_2025_split huggingface dataset:
A new method for determining the efficiency of tray columns with downcomers
Authors: Koziol Antoni , MaćKowiak Jerzy 
Published: August 2005

AbstractA new method for determining the efficiency of columns with sieve, sieve‐valve, valve, bubble cap and tunnel trays is introduced, taking into consideration entrainment, weeping and mixing of liquid on the tray. The presented calculation concept is valid for any stripping factors and any quality of liquid mixing on the tray. A comparison of the new calculation concept with experimental data from literature resulted in an average relative deviation of approx. 8% between the sieve tray efficiencies. The comparison of calculated values with experimental data for sieve‐valve, valve and tunnel trays also produced a satisfactory agreement.
Thermodynamic conditions for the formation of dioxin
Authors: Spencer Philip John , Neuschütz Dieter 
Published: August 2005

AbstractThe thermodynamic data bank system THERDAS [1, 2] has been used in conjunction with the program ChemSage [3] to calculate the conditions necessary for the formation of 2,3,7,8‐TCDD (tetrachlorodibenzodioxin). The stability ranges of both gaseous and condensed dioxin are presented as functions of the chlorine content, C/H mole ratio, oxygen partial pressure and temperature of the system.
Adsorption of p‐nitrophenol from aqueous solution on activated carbon: Influence of pH and preozonization
Authors: Serrano Vicente G´mez , Beltrán Fernando J. , Segovia Antonio Durán 
Published: August 2005

AbstractThe adsorption of p‐nitrophenol (PNP) from an NaOH, H3PO4‐buffered, aqueous solution on activated carbon was studied at pH 2, 7, and 8.5. Comparative studies were then carried out on ozonized carbon and ozonized PNP solution. In the latter case, PNP adsorption was performed from an ozonized solution, and also after exposing the activated carbon to the ozonized PNP solution for 24 h. At acid pH, PNP adsorption was found to be markedly higher than at neutral and weakly basic pH's. Ozonization of carbon affects the results only at pH 7 and 8.5. Ozonization of PNP led to a small decrease in adsorption, irrespective of the method of contect between carbon and ozonization reaction products. The rate was faster at acid than at basic pH, and the ozonization speeded up the adsorption slightly but only at pH 8.5. Application of a mathematical model indicated that mass transfer in bulk solution controls the rate of adsorption.
Determination of intraparticle transport parameters for multicomponent adsorption
Authors: Carl Petra Sabine , Seidel‐Morgenstern Andreas 
Published: August 2005

AbstractThis paper is devoted to the problem of determining intraparticle transport coefficients for multicomponent adsorption from experimental kinetic curves. Due to thermodynamic and kinetic interactions between the mixture's components, this task is more difficult than for single component systems. As an example, the kinetics of adsorption on activated carbon of binary mixtures of phenol and indole from aqueous solutions was studied in a continuous stirred tank adsorber (CSTA). To describe the intraparticle transport of this system, the surface diffusion model using a linear driving force (LDF) was applied. For determining the matrix of the unknown kinetic parameters of the LDF‐model, the application of three independent mathematical methods is discussed. Firstly, a semi‐analytical calculation (SA) of the intraparticle transport parameters by solving a system of linear equations on the basis of an empirical description of experimental kinetic curves is put forward. Secondly, a non‐linear regression (NR) method for parameter estimation was applied. The third method is a non‐linear regression which, in contrast to the SA and NR methods, guarantees the stability of the system of differential equations in the steady state of the process (NRS).
Useful experimental technique for the study of heterogeneous reactions
Authors: Bjerle Ingemar , Xu Fuming , Ye Zhicheng 
Published: August 2005

AbstractThe heterogeneous CaO/SO2 reaction has been thoroughly investigated by developing a series of new experimental techniques including the TGA reactor, the volulmetric reactor and the entrained flow reactor. The heterogeneous system is designed in such a way that most of the gas film and pore diffusion resistances are reduced. The modelling of each step related to the reaction is discussed while the chemical reaction and product layer diffusion are emphasized as the main influences on the SO2removal. The unchanging size shrinking core model is used to describe the reaction progress with a two stage assumption which has been confirmed in the TGA reactor: first, a very fast surface reaction, followed by a product layer diffusion controlled reaction. It was found from the experiments that the SO2‐partial pressure aat the very beginning is very important for a high removal efficiency during the initial reaction period.
Estimation of dispersion coefficients in packed beds
Authors: Foumeny Esmail A. , Chowdhury Masrur A. , McGreavy Colin , Castro Jose A. A. 
Published: August 2005

AbstractThe design and performance of fixed beds are greatly influenced by fluid dispersion. Unfortunately, the existing design data do not provide an accurate picture of this phenomenon. This paper presents an attempt to characterize the dispersive features of packed beds by obtaining reliable estimates of the associated coefficients in the axial (DL) and radial (DR) directions. Such an objective is achieved by developing a representative two‐dimensional pseudo‐continuous dispersed flow model which is subsequently employed to compute the desired coefficients using data obtained from a refined experimental approach. The established values have been correlated to allow such coefficients to be reliably predicted under a variety of physical and operating conditions.
A study of mass transfer from single large oscillating drops
Authors: Al‐Hassan Tariq , Mumford Clive James , Jeffreys Geoffrey Vaughan 
Published: August 2005

AbstractA study was made of mass trasfer rates from single large oscillating drops of pure liquid‐liquid systems, in the size range of 5 to 10 mm. A thrermostatically‐controlled, 50 mm in diameter, 1000 mm long, rising drop column was used, in which mirrors in the jacket enabled front and side views of drops to be photographed simultaneously. The systems studied were (1) toluene and acetone (dispersed)‐water (continuous), and (2) n‐heptane and acetone (dispersed)‐water (continuous). High concentrations of acetone (up to 3.75 kmol/m3) were used to examine the effect of different parameters on the mass transfer rate, frequency and amplitude of oscillation in countercurrent operation. Previous theories and empirical correlations [2–6, 12, 13, 15] for the prediction of overall mass transfer coefficients showed large deviations from measured values. These may have aarisen because the models do not represent droplet oscillation accurately, and/or apply only to oscillations of small droplets. Fair agreement was obtained for small oscillating droplets as low solute concentrations. The oscillations of a travelling drop were asymmetrical; the period of oscillation was uniform for mutually‐saturated systems but changed when mass transfer was taking place. The periods were longer than those predicted by the Lamb [7] and Shroeder and Kintner [37] correlations. Terminal velocities predicted from literature correlations [32, 34] did not give reasonable agreement with experimental data when there was mass transfer of solute. The drag coefficient increased with increasing mass transfer rate from the drop. Correlation of the results and the dispersed phase mass trasfer coefficients by dimensional analysis resulted in the correlation List of symbols at the end of the paper.

with a mean deviation of ±23%, by insertion of experimental oscillation frequency data. This will facilitate more accurate prediction of the dispersed phase mass transfer coefficients relating to equipment containing droplets in the oscillating regime, e.g. pulsed columns or agitated tanks.
Development and start‐up of a fixed bed reaction column for manufacturing antiknock enhancer MTBE
Authors: Flato Jörg , Hoffmann Ulrich 
Published: August 2005

AbstractA laboratory fixed‐bed reaction column is presented, in which a heterogeneouslyl catalyzed reversible fluid‐phase reaction and the separation of the reaction product from unreacted or inert components by distillation are performed simultaneously. The rection studied, the formation of methyl tertiary butyl ether (MTBE) from methanol and isobutylene, is catalyzed by strongly acidic macroreticular ion exchange resins. Packing elements are Raschig rings, manufactured for the first time from the above‐mentioned ion exchange resins. This in‐house made catalyst shows practically the same ion exchange capacity as the commercial products. The control system installed in the equipment is capable of correcting strong disturbances os the steady state. As shown by expwrimental results, the superimposed distillation process occurs in such a way that the chemical equilibrium of the MTBE synthesis does not limit isobutylene conversion.
Production of methylamines over ZK‐5 zeolite treated with tetramethoxysilane
Authors: Fetting Fritz , Dingerdissen Uwe 
Published: August 2005

AbstractThe reaction of methonol with ammonia over catalysts, used commercially today, to give methylamines, does not occur with the desired dimethylamine selectivity. Both a thermodynamically and kinetically controlled reaction over conventional catalysts permits a maximum dimethylamine selectivity (DMA selectivity) of only about 30 mol‐%. In addition to monomethylamine (MMA), a large amount of the undesirable trimethylamine (TMA) is formed. By using zeolites and taking advantage of their shap‐selective properties, it is possible to achieve high MMA and DMA selectivities. Shape‐selective catalysis can only take place at catalytically active centrs in the inteerior of the por system. The proportion of non‐shape‐selective catalysis at the active centres on the outer surfaces of zeolites is not negligible. Treatment of ZK‐5 zeolite with tetramethoxysilane deactivates the outer surface of the crystallite and increases the shape‐selectivity of the ZK‐5 zeolite with rgard to the amination reaction. Computer simulation of the zeolite skeleton in conjuction with investigations of the reaction leads to some conclusions with respect to the reaction mechanisms and reaction sites.
Design of vessels subjected to external pressure
Authors: Diwakar Chengalvala , Rao Yadavalli Bhaskar , Parlikar Ram Nagesh 
Published: August 2005

AbstractAn analytical procedure, developed to simulate the graphic method for the design of vessels subjected to external pressure or vacuum, suggested by the ASME Code, Section VIII, Division 1, is presented in this contribution. A comprehensive computer program based on this method is also presented. The program also covers the design of stiffener rings. The procedure can be easily extended to include other international standards such as the British and German codes, since the method is based on the concept of the number of lobes at collapse. The method produced reproducible results over the entire range of L/D0 and D0/t ratios of the code. The deviation observed at any point in this range is less than 0.5% for factor A. The variation in allowable pressure is less than 2%.
Sensitivity to phase equilibrium data in the simulation of a hydrogen purifying column
Authors: Campanella Enrique A. 
Published: August 2005

AbstractThe impact of phase equilibrium data on the simulation of a hydrogen purifying column has been evaluated. The analysis was performed in two stages. First, the most sensitive binary system was obtained. Then, it was verified if further experimental data were necessary for a reasonable simulation. The calculations were carried out using both rigorous and short‐cut methods.
Mixing characteristics in the torus reactor
Authors: Belleville Pascal , Nouri Lhadi , Legrand Jack 
Published: August 2005

AbstractThe hydrodynamic characteristics of propeller‐induced toroidal flow in a loop reactor were investigated by performing an RTD analysis. The experimental determination of circulation time allows the calculation of the mean axial velocity with respect to the rotational speed of the impeller. RTD measurements are interpreted with the aid of the dispersion plug flow model, and it is shown that axial dispersion is relatively weak in the torus reactor. The mixing time was also determined experimentally and related to the circulation time. A direct relationship between mixing time and axial dispersion coefficient has been established, leading to a correlation for the mixing time in a torus reactor.
Comparative studies of dehydrocyclization of n‐octane and iso‐octane on bifunctional and monofunctional Pt/Al2O3 catalysts
Authors: Ako Churchill T. , Susu Alfred A. 
Published: August 2005

AbstractThe dehydrocyclization of n‐octane and iso‐octane to ethyl benzene, and ortho‐, para‐, and meta‐xylenes was investigated on mono‐ and bifunctional platinum/alumina catalysts in a microcatalytic reactor with hydrogen as carrier at 1.8 atm pressure and between temperatures of 573 and 763 K, using pulse technique. On bifunctional Pt/Al2O3 catalyst, the total conversion of both n‐octane and iso‐octane was found to start from a high value and decrease with increasing temperature for all pulse volumes investigated. However, iso‐octane was found to be more reactive than n‐octane. There was only one primary product, namely iso‐octane, in the n‐octane reaction. As regards the iso‐octane reaction, two primary products, ethyl benzene and o‐oxylene were identified. For both reactions, these primary products decreased to a minimum as temperatures increased. On monofunctional (non‐acidic) Pt/Al2O3, the total conversion of n‐octane increased with temperature and passed through a maximum. The primary products of the reaction were ethyl benzene and o‐xylene.
A learning feedforward control strategy for the concentration control of recycle reactors. Part II: Disturbance control
Authors: Schnitzlein Klaus , Löwe Arno 
Published: August 2005

AbstractA disturbance control scheme for the concentration control of differential recycle reactors is developed which is based on the learning feedforward control strategy. Steady‐state decoupling eliminates interactions between the closed loops of this non‐linear, multivariable control system, thereby significantly improving the response to disturbances. Since the process model is iteratively updated, the control strategy can be regarded as a model identification adaptive control. Simulation experiments show the performance of the overall control concept.
Binary ion exchange equilibrium for Ca2+, Mg2+, K+, Na+ and H+ ions on amberlite IR‐120
Authors: de Lucas Martínez Antonio , Cañizares Pablo , Díaz Jacinto Zarca 
Published: August 2005

AbstractExperimental data are reported for ion exchange equilibria of binary systems on Amberlite IR‐120 resin, at different temperatures and total ionic concentrations in aqueous solutions. These systems exhibit non‐ideal behaviour in both phases, and the equilibrium characterization has been based on the law of mass action, using Wilson and Meisssner, and Kusik equations to correlate the activity coefficients in the resin and aqueous solutions, respectively. Equilibrium constants, standard thermodynamic properties (Gibbs free enthalpy changes, enthalpy and entropy) and Wilson binary parameters were obtained as functions of temperature.
Biocatalytic treatment of waste air
Authors: Wittorf Falko , Klein Joachim , Körner Klaus , Unterlöhner Othmar , Ziehr Holger 
Published: August 2005

AbstractBiological processes are becoming increasingly popular in dealing with waste air problems. Compared to chemical and physical treatment methods, they offer several advantages, especially in handling of waste air contaminated with low concentrations of biodegradable organic and, occasionally, inorganic substances. Two types of commercial systems are currently in use: biofilters and bioscrubbers. The aim of our studies was to develop an innovative concept of reactor design and engineering called “biocatalyst” (Biokatalysator). Our biocatalytic three‐phase system lies in between the conventional biofilter and bioscrubber, using biomass immobilized on macroporous, tubiform supports installed in parallel to the air flow. In laboratory‐scale investigations, a bioreactor was continuously fed with solvent‐laden air, which produced a more cost‐effective mode of operation than the conventional bioscrubber systems.
Mass transfer in packed columns: The cylinder model
Authors: Bornhütter Klaus , Mersmann Alfons 
Published: August 2005

AbstractIn order to predict mass transfer in packed columns, it is necessary to know the interfacial area. The well‐known and often cited equation (Onda, Kolev, Zech, etc.) do not yield precise values for the mass transfer coefficient βL ae or the interfacial area ae, especially for modern packing elements. A new model will be presented which takes into account the structure of packing (cylinder model) as well as the structure of the liquid hold‐up. This model allows the separation of liquid flow through packings into its main constituents, i.e. rivulets and drops (freely falling). The determination of the structure of liquid flow allows the prediction of effective interfacial areas as well as of volumetric mass transfer coefficients for irrigated large packing elements manufactured from plastics, metals or ceramic. The applicability to novel future packings is one of the advantages of the new model.
Influence of recycling on mass transfer and reaction in a G‐L jet loop reactor with variable interfacial area
Authors: Warnecke Hans‐Joachim , Prüss Jan , Tamm Günter , Brinkmann Manfred 
Published: August 2005

AbstractThe effect of recycling on mass transfer, characterized by the volumetric mass transfer coefficient kLa, was investigated by absorbing CO2 into water in a laboratory jet loop reactor. Based on a mathematical model, which includes the correlation function kLa = kLa(rL), a first order chemical reaction and the variation of interfacial area, a = a(εG), caused by strong absorption effects, the interaction ‘recycling – mass transfer – reaction’ was simulated and its influence on the reactor performance is discussed.
A general method of designing gas and gas‐liquid injectors using laws of turbulent jet mixing
Authors: Rao Natti S. , Kremer Hans 
Published: August 2005

AbstractBased on the equation for entrainment of a turbulent free jet, a simple method of designing gas and gas‐liquid injectors is presented. Using the formula for mass flow ratio of an injector consisting of a nozzle and a short cylindrical mixing tube open at both ends, a general equation for designing any injector with variable geometry and flow resistances is given. The optimization procedure is outlined. Compared to the conventional design of injectors, starting from macroscopic mass and momentum balances, the present method is much simpler, easily applicable and involves only one empirical entrainment coefficient. It is particularly advantageous in the case of variable density of the motive and entrained fluids since the density ratio appears explicitly in the relevant equations.
Gas and solids mixing in a commercial FCC regenerator
Authors: Wei Fei , Lin Shixiong , Yang Guanghua 
Published: August 2005

AbstractMixing of gas, solids and heat in a commercial FCC regenerator, 5.76 m in diameter, was investigated. This regenerator was operated at a high superficial gas velocity (>1.2 m/s) and high temperature (650–710°C). It is classified as a highly efficient regenerator. The profiles of coke content in the catalyst, gas composition, temperature and pressure were obtained by sampling and instrumental measurement. It was confirmed that a proposed axial dispersion model could be used for a satisfactory prediction of these experimental profiles. The values of gas and solids dispersion coefficients are also presented.
Quantitative rate equations for change of phase
Authors: Kasai Takeshi 
Published: August 2005

AbstractA new set of rate equations for gas desorption has been derived from the laws of thermodynamics and motion and the kinetic theory of gases. The equations assume that gas desorption or absorption originally represents an isothermal change at the interface, similarly to condensation or vaporization. The mass transfer in gas desorption or absorption is initially caused by external work being done on the system and takes place as work done by the system which instantly develops a concentration gradient, increases in internal energy and temperature, and a deviation from the ideal gas behaviour inside MTZ in the process of mass transfer. After cessation of external work, these conditions disappear following the transfer of a small residual mass at a constant velocity and a decrease in internal energy inside the MTZ.
Experimental investigations of flow, turbulence and subspace formation on cold models of gas‐stirred reactors with a view to describing mixing processes by mathematical models
Authors: Jank Gerhard , Nonte Thomas , Steinmetz Eberhard , Wilhelmi Herbert 
Published: August 2005

AbstractTheoretical and experimental investigations were performed with cold water models of bottom‐blown metallurgical ladles in order to develop a mathematical description of the mixing processes in such reactors. This analytical model is based on the subdivision of the reactor into interacting subspaces, whereby each subspace is regarded as an ideal mixer. The convective mass transfer between the subspaces is represented by constant coupling coefficients, and the mass balance for the material to be mixed in provides a homogeneous system of differential equations to determine the time dependence of concentration in the individual subspaces. Different combinations of interacting subspaces are represented. The flow field and the distribution of turbulence intensity measured by LDA in water models and the concentration profiles in mercury models measured by EMF cells show that a subdivision into five subspaces is adequate. Size, position and interaction coefficients are also determined by experiments. The calculated mixing times agree well with those measured.
Determination of operating characteristics of agitators in tubes
Authors: Rieger František , Weiserová Hana 
Published: August 2005

AbstractOperating characteristics of an agitator in a tube are necessary for the calculation of its pumping capacity and power consumption in a given configuration. General dimensionless equations for pumping and power characteristics are presented which were derived by inspection analysis of basic equations. Experimental procedure for the determination of these characteristics is put forward. This procedure is based on the measurement of flow rate or pressure rise and power consumption for an agitator in a draft tube, calandria or closed tube. The measurements and their evaluation are illustrated on the example of a three‐blade screw agitator.
Kinetics of coal desulphurization by Acidianus brierleyi
Authors: Olsson Gunnel , Larsson Liselotte , Holst Olle , Karlsson Hans T. 
Published: August 2005

AbstractAcidianus brierleyi was demonstrated to remove pyritic sulphur from coal. A. brierleyi was also found capable of catalyzing the removal of what is normally reported as organic sulphur from coal 171US34. A kinetic analysis was performed by assuming a first order reaction. The first order kinetics allowed a comparison with literature data for Thiobacillus ferrooxidans. Also, formation of jarosite was taken into account in the analysis. The simple first order kinetics was observed to fit the data on removal of sulphur satisfactorily.