bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evaporation rate and separation factor of molecular distillation in a falling film apparatus
Authors: Kawala Zdzislaw , Stephan Karl 
Published: August 2005

AbstractDuring molecular distillation in a falling film apparatus, temperature and concentration of the more volatile components undergo a marked decrease in axial and radial directions, due to the distillation in vacuo. The gradients produce changes in the rate of surface evaporation and separation efficiency along the flow path. A theoretical study of this problem is presented for binary mixtures. The respective differential equations for heat and mass transfer in the liquid film are solved numerically. As the results demonstrate, the aspect ratio of an apparatus should be large when a high separation is required and small when a high distillation rate is more important.
On‐line measurement of partical size distribution and partical concentration in suspensions by ultrasonic spectrometry
Authors: Riebel Ulrich , Löffler Friedrich 
Published: August 2005

AbstractThe principle of ultrasonic spectrometry is based on the measurement of the ultrasonic extinction caused by the presence of particles. From measurements at different frequencies and with the knowledge of the ultrasonic extinction cross section of the particles, a system of linear equations can be established and solved to obtain the particle size distribution and particle concentration. With an experimental apparatus covering the frequency range from 1.7 MHz to 81 MHz, particles ranging from 20 to 1000 μm in diameter may be analyzed. The measurements can be carried out with particle concentrations as high as 10% by volume.
A study of gas and liquid distributions in structured packings
Authors: Stikkelman Rob , Teeuw Hessel , Wesselingh Hans , de Graauw Jan , Olujic Zarko 
Published: August 2005

AbstractThis study describes the gas and liquid distributions in a column with structured packings. The column is 0.5 m in diameter. It is equipped with a total of 1289 detectors in the top and bottom cross‐sections. These detectors provide a detailed picture of the gas and liquid flows through elements of only 25 × 25 mm2. The maldistribution in the gas bulk flow is negligible. Only the observed wall can contribute to malperformance. The gas flows in parallel to sheet orientation, thus introducing a radial transport. Together with the change in the orientation of subsequent packing elements, this results in good gas mixing. It was observed that the liquid wall flow rate decreases when the gas velocity exceeds 1.7 m/s. Up to the loading point, the maldistribution of the liquid is constant. Above this point, the equality of the distribution deteriorates rapidly, due to the occurrence of large‐scale liquid segregation.
Measurement of transient deformations by double‐pulsed holography
Authors: Hajduk Martin , Mewes Dieter 
Published: August 2005

AbstractHolographic interferometry is used for the determination of surface deformation of items of equipment. The material failure which caused the surface deformation can then be identified. Because a double‐pulsed laser is used to plot the hologram, non‐vibration stabilized holographic equipment is necessary. Thus, non‐destructive testing of equipment components is also possible during plant operation. In this report, we present the experimental results of non‐destructive testing of composite materials. We examined centrifugally cast pipes and filament wound pipes, which were made from glass fibre reinforced plastic and carbon fibre reinforced graphite. As a rule, the severity of failure is characterized by the apparent perturbation of its holographically stored fringe pattern. In this report, we present the experimental results which yield the relationship between the perturbation of interference fringes and the extent of the specific types of failure. Measurement results were compared with displacements calculated by the finite element method. By using the interferogram, and with the knowledge of tension stress beneath the surface, the size of the crack can be estimated. The size of the smallest detectable flaw was clearly smaller than the critical flaw size. Thus, holographic interferometry is suitable for detecting damage to cylindrical containers.
Breakthrough behaviour of a binary gas mixture with azeotropic adsorption equilibrium
Authors: Persichini Carlo , Mersmann Alfons 
Published: August 2005

AbstractThis contribution reports on the breakthrough behaviour of binary gas mixtures with ideal and non‐ideal multicomponent adsorption equilibria. Investigations were carried out on mixtures CO2/C2H4 and C2H4/C2H6, both adsorbed on molecular sieve 5A (ms5A). The adsorption equilibrium of the system CO2/C2H4/ms5A may exhibit azeotropic behaviour, which subsides with decreasing active pressure (= sum of partial pressures of adsorbable components) or on raising the temperature. In contrast, the system C2H4/C2H6/ms5A maintains its ideal behaviour also at higher active pressures or lower temperatures. Attempts to calculate the non‐ideal adsorption equilibrium from measured single component isotherms have failed when known models were applied. The investigation of the effect of azeotropic equilibrium on the fixed bed adsorption led to intersecting breakthrough curves of the two components. This behaviour is due to a displacement of equilibrium caused by the change in the active pressure and partial pressures, and a superposed temperature effect. This can be shown by calculating the breakthrough curves with the equilibrium model.
Residence time distribution and hold‐up in a cocurrent upflow packed bed reactor at elevated pressure
Authors: van Gelder Klaas B. , Westerterp K. Roel 
Published: August 2005

AbstractThe residence time distribution in liquid phase was measured in a cocurrent upflow packed bed reactor for the system methanol‐hydrogen at low Reynolds numbers and at elevated pressure. The plug flow with axial dispersion model was used to describe mixing in the system. The imperfect pulse method was used to measure the system response to a tracer pulse input. The parameters were calculated using the weighted moments method. The influence of the weighting factor was investigated. The experimental and theoretical outputs, as calculated by convolution, agreed very well. Different types of correlations were used for the Bodenstein number and liquid hold‐up. From these correlations, the optimal one was selected for each parameter. A comparison was made between the ordinary moments and the weighted moments methods which led to the conclusion that the latter method is superior with respect to the accuracy of the estimated parameters and therefore strongly recommended.
On supersaturation during mass crystallization from solution
Authors: Kind Matthias , Mersmann Alfons 
Published: August 2005

AbstractSupersaturation is the driving force for crystallization from solution. For design and operation of crystallization processes, it is necessary to apply a set of criteria for the determination of appropriate or even optimum supersaturation. In this paper we present and discuss the results of our experimental and theoretical investigations on supersaturation during crystallization from solution. While the determination of the metastable zone width of the solution is frequently applied as a fast check on solution behaviour, we demonstrate that the determination of the induction period of the supersaturated solution is a useful aid in ascertaining the maximum allowable supersaturation. Theoretical considerations and experiments confirm that the induction period dependssoley on growth kinetics if secondary nucleation is the predominant mechanism. In order to avoid uncontrollable spontaneous value of between 70 and 130 μm during crystallization. Since growth kinetics turns out to be the only important system property for the determination of maximum possible supersaturation, we conclude the paper with some arguments concerning a closed representation of growth kinetics.
Effect of nuclei storage and growth rate dispersion on the transient behaviour of continuous crystallizers
Authors: Heffels Stefan K. , de Jong Esso J. 
Published: August 2005

AbstractBench scale experiments and computer simulations of transient crystal size distributions obtained in a 1.4 m3 sucrose crystallizer, which prove the existence of nuclei stock, are presented. This stock represents a large number of non‐growing nuclei, which can be activated at increased supersaturations. The nuclei stock attenuates the dynamic behaviour of crystallization process.
Biological treatment of effluents from a coal tar refinery using immobilized biomass
Authors: Hüppe Paul , Hempel Dietmar Christan , Höke Hartmut 
Published: August 2005

AbstractAn airlift‐loop reactor with a fluidized bed was used for the microbiological removal of a complex mixture of aromatic substances originating from coal tar process waters. A specially adapted mixed microbial culture derived from several soil and sludge samples was immobilized on fluidized sand particles and retained in a reactor at high biomas concentrations of 3 to 16 g dry matter per liter, depending on the COD‐load. In a two‐stage pilot plant, those aromatic substances which passed through the first stage either unaltered or only partially oxidized were effectively eliminated by the immobilized biomass in the second stage. Whereas most of the waste water components such as phenols and quinoline were already degraded by a conventional activated sludge system in the first stage, the majority of nitrogen‐containing aromatic bases could be sufficiently eliminated with specially adapted micro‐organisms in the second stage. Although the COD‐feed load was increased to 12 and 15 kg m−3 d−1 in the first and second stages, respectively, it was removed to the extent of 87% on the average with an overall residence time varying between 11.5 and 29 h.
Modelling of a fluidized bed bioreactor for immobilized enzymes (Part 2)
Authors: Kiesser Torsten , Oerstzen Gustav A. , Bauer Werner 
Published: August 2005

AbstractIn the first part of this contribution, a mathematical model was presented for a liquid fluidized bed using immobilized enzymes, with reversible Michaelis‐Menten kinetics. This part is focused on the experimental results. The reaction kinetics of native and immobilized enzymes was determined in continuous stirred tank reactors under comparable conditions. The influence of external mass transfer was investigated in a fixed bed reactor column. The extend of pore diffusional resistance was examined in a continuous stirred tank reactor and with a numerical simulation. Hydrodynamics was measured in different reactor columns (diameter dt = 0.052 − 0.225 m; length L: 1.0–2.0m) and with a static mixer. Further, the concentration profile was determined in a fluidized bed reactor with side stream analysis for different biocatalyst samples, fluid velocities and bed heights. The simulation of experimental results indicates that they are well described by the developed model. Furthermore, the model is well suited to predicting the influence of specific parameters on the effective kinetics of the biocatalyst and the expansion of the fluidized bed.
Absorption of NO2/N2O4 in nitric acid
Authors: Weisweiler Werner , Eidam Klaus , Thiemann Michael , Scheibler Erich , Wiegand Karl Wilhelm 
Published: August 2005

AbstractLaboratory‐scale measurements were performed on the absorption of NO2 gas into diluted nitric acid. The concentration of NO2 gas, which represents an NO2/N2O4 equilibrium, varied from 1000 to 20000 ppm, the carrier gas being nitrogen. The concentration of nitric acid ranged from 15 to 60 mass‐%. The absorption experiments were carried out in a double stirred cell, with a defined gas/liquid interface as the mass transfer area. The liquid phase was conducted periodically and the gas phase continuously. Mass flow rates were determined. The well‐known film model of absorption was used for analyzing the experimental results. Only the N2O4 species was considered to pass the gas/liquid interface. The measured data yielded values of H(k D1)1/2 as well as their variation with temperature and nitric acid concentration.
Critical temperatures and pressures and high temperature vapour pressures of seven alcohols
Authors: Lydersen Aksel L. , Tsochev Vassil 
Published: August 2005

AbstractCritical temperatures and pressures have been determined experimentally for the four lowest n‐alcohols, 2‐propanol, 2‐butanol, and 2‐methyl‐1‐propanol, and are given in the penultimate line of Table 3. The last line of Table 3 lists the weighted mean critical pressures, with the corresponding critical temperatures obtained from he vapour pressure equation. Comparison with the corresponding data from standard reference books reveals deviations from the experimental data in some [2, 4] and incorrect critical pressure for ethanol in all five reference books quoted in Table 3. In addition, vapour pressure data were obtained for the same alcohols in the temperature range approaching the critical point. The measurements are reproduced by the simplified Clausius‐Clapeyron equation with the constants and standard deviation given in Table 2.
Influence of gas flow on heat transfer in film condensation
Authors: Numrich Reiner 
Published: August 2005

AbstractFor the dimensioning of condensers in film condensation, the heat transfer coefficient between film surface and cooled tube wall must be known. Generally, Nusselt equations are used which have been verified by experiments. When there is no significant gas flow, a large number of equations correlate the experimental. data very well. The description of heat transfer enhancement by a significant gas flow is not sufficiently covered by the available literature. For film wise condensation in a vertical tube, a calculation method is presented which reproduces this phenomenon characterized by the interfacial shear stress at the film surface. This method is based on the assumption that, in the proximity of gas flow, the condensation process also affects the interfacial shear stress. A comparison with known experimental local Nusselt numbers showed a good agreement with water as the fluid. For test fluid MWA, which was used by Blangetti, the measured values show only a moderate agreement with theoretical calculations. Possibly, this is related to entertainment which occurred during measurements at film Reynolds numbers of over 80.
Evaluation of plug flow assumption in packed beds
Authors: Foumeny Esmail A. , Pahlevanzadeh Hassan 
Published: August 2005

AbstractKnowledge of modelling and computer simulation is an essential prerequisite for type design and operation of packed bed systems. Unfortunately, the existing models are based on a number of weak assumptions of which plug flow can be considered as a common deficiency. Such a simplification would inevitably have a noticeable bearing on the accuracy of the final design and consequently calls for the development of a coherent mathematical description of the packed bed systems so that reliable design information can be explored. A two‐dimensional heterogeneous transient model has been developed which allows for the radial variations of velocity and void age. The model equations have been solved using numerical approximation. The simulated results reveal significant differences between the present refined data and those established from existing plug flow models.
Measurements with multi‐point microprobes: Effect of suspended solids on the hydrodynamics of bubble columns for application in chemical and biotechnological processes
Authors: Wolff Christoph , Briegleb Frank Ulrich , Bader Joerg , Hektor Klaus , Hammer Hans 
Published: August 2005

AbstractMany experimental studies reveal that suspended solids considerably alter the coalescence behaviour and hydrodynamic functions of wo‐phase flow. But no systematic efforts have yet been undertaken to separate the effects of different particle properties on local gas hold‐up, bubble size and interfacial area gas/liquid. The aim of this paper is to present the local values of these parameters in three‐phase fluidized beds of different solids, using miniaturized optical fiber and conductivity needle probes. It is shown that particle concentration, size and, in particular, density are decisive for the change in coalescence behaviour. Ranges of normal (ϱS > ϱL) and inverse fluidization (ϱS < ϱL) must be distinguished and the flow regime also exerts a strong influence on the interactions between the dispersed phases, the transition point itself being a function of particle properties can be observed, This effect is evaluated for different column diameters, between 0.1 and 0.3 m.
Growth rate dispersion in a continuous sucrose crystallizer and its effect on CSD
Authors: Gupta Bhaskar Sen , Dutta Tapas K. 
Published: August 2005

AbstractA Random Crystal Growth (RCG)model is proposed to predict CSD in a continuous MSMPR crystallizer when the crystals exhibit growth rate dispersion. RCG model links two well‐known models of growth rate dispersion, namely the Random Fluctuation (RF) and Constant Crystal Growth (CCG) Models. Monte Carlo simulation has been employed to solve the model equations. Predicted results are compared with experimental CSD data on sucrose reported by Bennett.
Large‐scale anaerobic/aerobic treatment of complex industrial wastewater using immobilized biomass in fluidized bed and air‐lift suspension reactors
Authors: Heijnen Sef J. , Mulder Arnold , Weltevrede René , Hols Pam H. , van Leeuwen Hans L. J. M. 
Published: August 2005

AbstractWarm concentrated industrial wastewaters are preferably treated in an anaerobic reactor for reasons of energy generation and low surplus sludge production. Problems to be solved in the practical application concern a low growth rate of the micro‐organisms, their low settling rate, process instability and the need for after treatment of the noxious anaerobic effluent which often contains NH and HS−. The use of biomass immobilized on small suspended carriers (< 0.5 mm) has proven to be a suitable means to overcome most of these problems. Results are presented on pilot and full‐scale pretreatment of industrial wastewater in an anaerobic 2‐state fluidized bed reactor for CH4‐production and laboratory and pilot scale post‐treatment of the anaerobic effluent, which contains NH and HS− in an aerobic air‐lift suspension reactor for the production of NO and SO.
Contribution to solving the problem of dioxins generated during waste incineration
Authors: Vogg Hubert , Hunsinger Hans , Stieglitz Ludwig 
Published: August 2005

AbstractThe production of dioxins/furans during waste incineration, and particularly the development of measures for minimizing the amount of generated pollutants, continue to command a considerable scientific as well public interest. Experiments are reported which were performed at the TAMARA municipal solid waste pilot incineration, erected on the premises of the karlsruhe Nuclear Research Centre. These experiments show that the solid waste mass flow rate and moisture content influence the dioxin/furan formation, Good removal efficiencies of dioxins/furans have been In wet cleaning. Hydrogen peroxide added to the crude gas is an interesting “killer” reagent for dioxins/furans.
Study on regeneration of diesel particulate filter using a laboratory reactor
Authors: Hoffmann Ulrich , Ma Jianxin 
Published: August 2005

AbstractRegeneration of diesel particulate filters can be accomplished by complete combustion of a collected particulate. A reactor has been developed for study of the regeneration in the presence of catalysts, additives and ignition aids. This reactor allows an accurate measurement of soot ignition temperatures and a kinetic study of soot oxidation with an undisturbed soot layer and under a defined gas composition. Results of various investigations carried out with this reactor are presented.
Deasphaltization and demetalling of heavy crude oils and distillation residues with CO2
Authors: Eckermann Burkhard , Vogelpohl Alfons 
Published: August 2005

AbstractDeasphaltization of heavy crude oils and distillation residues may reduce the metal content of these oils to such an extend that the upgrading of deasphaltized oil in a catalytic process becomes economically feasible. Experimental results of deasphaltization of Boscan crude from Venezuela, using subcritical and supercritical carbon dioxide as deasphaltizing agent, are presented. Deasphaltization and demetalling with CO2 in the supercritical state is more effective. Under favorable conditions, the deasphaltized oil contains practically no asphaltenes and the metal content is reduced by 690 wt‐%. The influence of n‐heptane or n‐pentane addition to the crude, which lowers viscosity and promotes flocculation, is also discussed. Furthermore, a multistage deasphaltization process is more efficient than a single stage process.
New and overlooked relationships for turbulent flow in channels
Authors: Churchill Stuard W. 
Published: August 2005

AbstractThis paper describes general, asymptotic and speculative relationships which can be deduced directly from the time‐averaged form of the basic, partial‐differential model for the conservation of mass and momentum in fully developed turbulent flow of constant‐property fluids through round and parallel‐plate channels. Such relationship are shown to provide insight as well as useful forms for correlation. Several analogies for flow in round tubes and between parallel plates which have generally been overlooked are reexamined and extended. A generally overlooked anomaly which occurs for flow in concentric, circular annuli, for flow between plates of non‐identical roughness, and for the combination of forced and wall‐Ind.uced flow between parallel plates is also is noted. The data needed to test the above analogies and to quantify the deviations, if any identified, as well as those needed to generalize the anomalous behavior.
Computation of plate columns for NOx absorption by a new stage‐to‐stage method
Authors: Wiegand Karl Wilhelm , Scheibler Erich , Thiemann Michael 
Published: August 2005

AbstractA new stage‐to‐stage method has been developed for the calculation of NXx absorption columns. Each stage of the absorption column is simulated as a combination of a bubble column reactor (absorption) and an adiabatic plug for reactor (oxidation). The bubble column reactor is modelled as two single stirred tank reactors, one as a gas‐phase and one as a liquid‐phase reactor, both coupled by mass and heat transfer. In this hydrodynamic model, a dynamic approach is adopted, in which the gas‐phase transport of N2O4 is the limiting step for the absorption. A gas‐phasepseudo‐enhancement for factor for N2O4 is therefore introduced. The balance equations for a single phase of the bubble column are solved with a Newton‐Raphson algorithm. The entire column calculation is divided into a gas and a liquid side. On both sides, the stage‐to‐stage method is applied in such way that the overall calculation is performed as a loop process. The direction of the loop calculation follows that of the flow: gas‐side upwards and liquid‐side downwards.
Evaluation of standard thermodynamic parameters for the sorption of n‐hexane and methanol in zeolites
Authors: Pal Tapan Kumar , Majumder Asitava , Raha Tarun Kumar , Fetting Fritz 
Published: August 2005

AbstractAdsorption isotherms for n‐hexane and methanol in mordenite and ZSM5 in the temperature range from 323 K to 473 K were found to be of type 1. The adsorbate‐adsorbent interaction (C1) and adsorbate‐adsorbate interaction (C2) wee computed according to Bradley and Wilkins model, whereas the Rees and Williams model predicts the adsorption characteristics. Finally, the thermodynamic parameters such as ΔGo, ΔSo, ΔHo, K, K+ have been evaluated for the sorption of n‐hexane in mordenite and ZSM5.