bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fluid dynamic description of jet‐loop reactors in multiphase operation
Authors: Tebel Karl Heinz , Zehner Peter 
Published: August 2005

AbstractA superposition of simple physical equations allows a satisfactory, comprehensive fluid dynamic description of jet‐loop reactors in multiphase operation up to a dispersed phase hold‐up of 15%. In the case of higher concentrations, there are further interactions which are not yet included in the model description. Apart from the drag coefficient of the single‐phase jet loop, information on the particle swarm behaviour, i.e. on the slip velocity of the dispersed phase is required. Explicit formulation of the influence of the relevant geometrical parameters permits a reliable scale‐up without additional adaptation parameters.
Vapour‐liquid equilibria of hydrogen/coal liquid and methane/coal liquid systems at elevated temperatures and pressures
Authors: Wiegand Karl W. , Strobel Bernd O. , Hofmann Hanns 
Published: August 2005

AbstractA cubic equation of state is modified in such a way that prediction of PVT data from 40 model compounds, typical of coal oil, becomes possible with an absolute mean deviation of less than 2% for saturated liquid volumes and vapour pressures > 1 bar. Additional correlations for binary interaction parameters are obtained by an optimization procedure using vapour‐liquid euilibrium (VLE) data from known heavy hydrocarbon liquid/light gas systems. When the modified equation is applied to coal‐derived liquids, only specific gravity and boiling analysis data of the coal liquids are required, primarily in order to determine the equation‐of‐state parameters. The proposed equation is shown to allow a good prediction of VLE data for systems consisting of wide‐boiling‐range coal oils and light gases. Experimental values were obtained at elevated temperatures and pressures with a circulation flow apparatus.
Directional specific shear‐rate measurements in gas‐liquid two‐phase flow
Authors: Pauli Judith , Menzel Thomas , Onken Ulfert 
Published: August 2005

AbstractWall shear rate vectors in a bubble column and an airlift‐loop reactor were measured using the limiting‐current electrodiffusion technique. In connection with a new circular three‐segment probe, the magnitudes and directions of shear rates were determined. The results for the bubble column are in good agreement with hot film‐anemometry measurements in the same column. Moreover, the spiral flow structure, postulated in the shear‐zone model of Franz, has been confirmed. In addition, the measuring technique was used to determine the flow structure in an airlift‐loop reactor employed for the cultivation of animal cells. The region above the gas distributor of this fermenter has been identified as critical for mechanical damage to the cells.
Measurement of heat transfer coefficients in tubes by temperature oscillation analysis
Authors: Roetzel Wilfried 
Published: August 2005

AbstractAn experimental technique and evaluation method is described for the determination of local heat transfer coefficients in tubes or other ducts. By means of a rotary mixing valve, cold and warm fluid flows are mixed in order to generate an arbitrarily shaped but periodically oscillating inlet temperature profile at the test tube. The propagation of the fundamental harmonic oscillation from the fluid to the outer surface of the tube wall is calculated analytically. Comparison of fluid and wall oscillations yields the heat transfer coefficient to be measured. The inaccurate measurement of fluid bulk temperature in the centre of the cross‐section is compensated by an additional correction. Experiments were carried out with turbulent water flow through a copper tube. Measured heat transfer coefficients were compared to values calculated using Hausen's equation and good agreement was obtained.
Investigation of a wet dust scrubber with a pneumatic nozzle: Dust collection based on turbulent diffusion
Authors: Centner Peter , Büttner Helmut , Ebert Fritz 
Published: August 2005

AbstractThe “nozzle scrubber” is a wet scrubber in which the scrubbing water is dispersed in dust laden gas stream by means of one or more pneumatic nozzle. This scrubber is distinguished by an excellent collection efficiency for submicron dust at an unusually low energy and water consumption. So far, the physical effects affecting the separation cannot be explained by a well‐defined theory. Therefore, it is sensible to investigate the collection efficiency with regard to the mechanisms of inertial impaction, turbulent diffusion and coalescence induced by turbulence. The experimental equipment is of a very simple design. A light scattering device was used to measure the particle distributions. In addition, electron micrographs were analyzed to obtain information about the submicron particles. The influence of operating parameters on grade efficiency has been demonstrated by their systematic variation. The contribution of turbulent diffusion to the collection efficiency has been confirmed; nevertheless, grade efficiencies were also measured when inertial impaction prevailed.
Influence of feed solids concentration on the performance of hydrocyclones
Authors: Braun Thomas , Bohnet Matthias 
Published: August 2005

AbstractEven though the influence of solids concentration in the feed on the separation efficiency of hydrocyclones has long been recognized, a systematic research on the change in pressure drop across the hydrocyclone and the latter's separation characteristics has thus far been lacking. If all other operating parameters are kept constant, an increase in feed concentration generally leads to a coarser cut size, reduced sharpness of separation and a rise in pressure drop. Apart from the particles hindering one another's radial motion, the limited capacity of the apex valve and the changes in the flow field within the hydrocyclone cause additional particles to be entrained by the overflow. The flow ratio thus becomes an additional parameter in determining the cyclone efficiency. A theoretical model, which takes these effects into account, has been developed and successfully tested against experimental data.
Modern carbon fibres from polyacrylonitrile (PAN)‐polyheteroaromatics with preferred orientation
Authors: Fitzer Erich , Frohs Wilhelm 
Published: August 2005

AbstractThis contribution presents the mechanical data of high performance carbon fibres currently available on the market, based on experimental studies on stabilization and pyrolysis of PAN (SAF) from Courtaulds. The effects of stabilization and carbonization temperatures on the properties as well as on the ultra‐ and crystalline structures of the fibres are shown in more detail.
Modelling of thermal desorption of active coke loaded with sulphuric acid and ammonium sulphate
Authors: Richter Ekkehard 
Published: August 2005

AbstractThe BF‐Uhde‐Mitsui Process uses active coke for SO2‐ and NOx‐removal from flue gases in the temperature range between 100 and 190 °C, Experimental methods of thermal regeneration were applied to the evaluation of the state of the adsorbent after use in flue gas cleaning and of the parameters for disrober design. A reaction model was derived from experiments carried out in differential and back‐mix reactors. The parameters were evaluated by adaptation of the model to the adsorption spectra. The model was successfully applied to the regeneration of active coke in a fluidized bed reactor.
Mass transfer in countercurrent and cocurrent bubble columns
Authors: Seno Tadachika , Uchida Shigeo , Tsuyutani Shinji 
Published: August 2005

AbstractThe hydrodynamic and mass transfer characteristics in countercurrent, cocurrent and liquid batch operations with various Newtonian liquids were studied experimentally using the same bubble column. Taking the effect of gas sparger geometries, operating variables and liquid properties into account, empirical correlations were obtained for the gas hold‐up and the volumetric liquid‐phase mass transfer coefficient.
Study on dynamic behaviour of thermally coupled distillation processes
Authors: Xien Xu , Chunyan Wang 
Published: August 2005

AbstractA dynamic mathematical model has been developed which is suitable for thermally coupled distillation processes. An algorithm known as the equation‐decoupled method was used for simulation. EPISODE software and LU decomposition method were adopted to solve the ordinary differential and algebraic equations of the model, respectively. The initial conditions, viz. a solution for the steady state of the process in dynamics simulation were obtained by means of modified Naphtali‐Sandholm algorithm. Research on the dynamic behaviour of thermally coupled distillation processes was carried out on two examples. It was found, via the dynamic simulation, that a disturbance in the distribution of vapour coupled stream has a large effect on the composition of vapour side withdrawal and, similarly, for liquid coupled stream, on that of liquid side withdrawal when the fraction of side withdrawal is fixed, and a smaller effect when the quantity of side withdrawal is fixed.
Formation of Di‐isobutene, main by‐product of methyl tertiary butyl ethyl ether synthesis catalyzed by ion exchange resin
Authors: Rehfinger Alwin , Hoffmann Ulrich 
Published: August 2005

AbstractAn experimental set‐up is presented for the measurement of steady‐state reaction rates in the liquid phase methyl tertiary butyl ether (MTBE) synthesis from isobutene and methanol using ion exchange resin as catalyst. This apparatus was used for a separate investigation of the main side reaction, i.e., the formation of isobutene dimers (DIB), in the temperature range between 60 and 90°C. The reaction catalyzed by Amberlyst 15 (A15) showed no steady‐state behaviour, but the catalytic activity declined at a rate dependent on the reaction conditions. Time constants for activity loss were determined in the range from 3.5 to 30 h. The deactivated A15 catalyst could be regenerated through MTBE synthesis experiment. Deactivation is assumed to be caused by blocking of the microparticle gel phase by higher isobutene oligomers. The DIB formation, using 1‐butene as solvent, was of 2nd order with respect to isobutene and showed an apparent activation energy of about 40 kJ/mol.
Determination of flooding gas velocity and liquid hold‐up at flooding in packed columns for gas/liquid systems
Authors: Maćkowiak Jerzy 
Published: August 2005

AbstractA new model of suspended bed of droplets for describing the vaour or gas the vapour or gas velocity at the flooding point in packed of columns for rectification and absorption under vacuum and normal pressure is presented metallic, ceramic and plastic packings with diameters of 8–90 mm as well on sheet metal and gauze packings, in a wide range of liquid and vapour loads. Approximately 650 literature measurements and own data were evaluated. The mean relative error in determining the gas velocity at flooding point is less than ±5%. On the basis of the double layer model, a new equation was derived for the hold‐up at flooding point, which is needed for the calculation of the flooding gas velocity. An example of calculations for sample applications is also included.
Agitation of aerated emulsions
Authors: Schneider Torsten , Vettermann Rainer , Franz Kristian 
Published: August 2005

AbstractAerated emulsions are gaining significance in fermentation as well as in inorganic and organic chemistry. In these processes, liquid‐liquid mass transfer can be the limiting step. Therefore, the effect of gassing rate on droplet size was investigated as a function of dispersed liquid phase concentration and power input in different vessels. At high power inputs, the droplet size decreased. With increasing dispersed phase concentration and gassing rate, the droplet size increased and its dependence on power input subsided.
Batch cooling crystallization at constant supersaturation: Technique and experimental results
Authors: Gutwald Thomas , Mersmann Alfons 
Published: August 2005

AbstractA new laboratory plant for batch cooling crystallization is described, which allows to maintain the supersaturation at a constant level during an experimental run. A method for continuous supersaturation measurements has been developed, using a density meter and a hydrocyclone. Experimental results obtained from a seeded solution in constant supersaturation cooling mode and at constant cooling rate are compared. In the case of a constant cooling rate, the supersaturation passes through a sharp maximum, whereby effective nucleation is enhanced. As a consequence, a smaller median crystal size is obtained than for cooling at constant supersaturation. Equation for controlled cooling at a constant supersaturation require an accurate description of the effective rate of nucleation. Therefore, the mechanical stress, to which the crystals are subjected, must be included as the main source of new nuclei. This is shown by the influence of stirrer on batch time.
Simple new formulae for efficiency and mean temperature difference in heat echangers
Authors: Martin Holger 
Published: August 2005

AbstractThe well‐known formulae for efficiency and mean temperature difference of a heat exchanger as functions of its numbers of transfer units, or dimensionless lengths, can be written in a more compact form by introducing the auxiliary function φ(x) = x/(1 – e−x). The resulting new formulae show a number of advantages: They are shorter, easier to memorize, and in many cases the limiting values can be seen more directly. They may therefore contribute to easier and faster heat exchanger design, and to reduced probability of errors in the relevant calculations.
Thermal decomposition of 2, 3‐dimethyl butane: Experiments and mechanistic modelling
Authors: Stabel Uwe , Hönig Ulrich F. , Nowak Ulrich , Ederer Hanns J. , Ebert Klaus H. 
Published: August 2005

AbstractPyrolysis of 2,3‐dimethyl butane (DMB) was carried out in a quartz flow reactor in the temperature range from 740 to 1032 K at normal pressure. The input concentration of DMB was 3.3 × 10−3 mol/1 using argon as diluent. Reaction time ranged between 3.1 and 3.9 s. The following products were analyzed by two‐column gas chromatography: hydrogen, methane, ethene, propane, propene, butenes, butadiene, 2‐methyl‐2‐butene, isoprene, benzene and toluene. Compared to thermal decomposition of n‐hexane under similar experimental conditions, the main difference concerned the formation of ethylene, ethane and branched alkanes. A reaction model, based on elementary reactions, was developed to predict the experimental results and to verify our data basis of elementary reactions under different conditions. The model gives a quantitative description of the complex chemistry of the process. In addition, an algorithm is presented for model reduction.
Sensitivity analysis of catalytic conversion of n‐C6
Authors: Wolff Andrzej 
Published: August 2005

AbstractThe present paper is a case study of an application of sensitivity analysis in chemical kinetics. Emphasis is laid upon chemical interpretation of sensitivity information and on identification of the most important model important model parameters. The kinetic model for reforming of C6 hydrocarbons proposed by Mobil [14] is extended to the analysis of the behavior of n‐hexane conversion in an adiabatic reactor. The importance of six initial conditions (feed composition and initial temperature) is analyzed by the computation of normalized first order sensitivity gradients (y/y) (δyi/δy). The relative importance of 21 model parameters αj is estimated by the computation of normalized sensitivity gradients of the type (αj/yi) (δyi/δαj). The influence of the decisive model parameters ΔH and ΔH (activation enthalpies of benzene hydrogenation and methyl cyclopentane isomerization, respectively) as well as operating parameters is presented. The problem of uncertainly in the value of ΔH and its influence on the model solution is also sown. Finally, some advantages of the application of normalized gradients of the explanation of process behavior are discussed.
The implications of carboxylic acid properties
Authors: Andereya Erwin , Chase J. David 
Published: August 2005

AbstractSome properties of carboxylic acids are reviewed, with emphasis on recent experimental data, Qualified, consistent latent heat of vaporization data were developed for the series and a two‐population viewpoint is suggested. The equation of state formulated by Grenzheuser [1] is also recommended as a practical tool, and its further development is urged.
Adsorption and catalytic reactions of NO and NH3 on activated carbon
Authors: Richter Ekkehard , Schmidt Hans‐Jürgen , Schecker Hans‐Georg 
Published: August 2005

AbstractIn industrial processes, the reduction of nitrogen oxides by ammonia on activated carbons is carried out at temperatures between 90 and 190 °C. Adsorption of NO and NH3 on the catalyst was investigated separately. Reactions models for NO‐reduction by carbon and ammonia were derived from experiments carried out in an integral reactor. In each case, the formation of an adsorbed (NO2)‐complex is an important step. The kinetics of both reactions was described by modified Langmuir‐Hinshelwood equations.
Mixing in continuous DTB and FC crystallizers
Authors: Gupta Bhaskar Sen , Dutta Tapas K. 
Published: August 2005

AbstractOwing to imperfect mixing, the theoretical prediction of CSD for an MSMPR crystallizer deviates from the experimental results. In the present work, different modelling approaches were adopted to account for incomplete mixing in DTB and FC crystallizers. For DTB crystallizers, compartmental model, based on an earlier work of Nyvlt et al. has been proposed. For FC crystallizers, a mixed model comprising perfectly mixed and plug flow regimes has been put forward. This is based on the tracer response studies reported by de Jong. Predicted results were compared with experimental data of Bennett and van Buren for continuous urea crystallizers.
Selection and design of aerobic bioreactors
Authors: Mersmann Alfons , Schneider Georg , Voit Harald , Wenzig Edda 
Published: August 2005

AbstractCompared to chemical reactors, there are additional requirements to be considered when selecting and designing a bioreactor. The cultivated organisms and most of the desired products are to a greater or lesser extent sensitive to temperature, pH and Shear stress. Furthermore, sterilization often plays an important role in maintaining a monoseptic process. Many design procedures for chemical reactors can be applied but requirements which are relevant to the biological system are sometimes decisive. Consequently, it is useful to first consider the essential features of the organisms with respect to the selection and design of bioreactors. Attention must be paid to the fermentation medium because its flow behaviour can range from slightly viscous and Newtonian to highly viscous, non‐Newtonian. Many papers deal with low viscosity fermentation broths [1–5]. However, little is known about the design of bioreactors for highly viscous non‐Newtonian liquids. Fundamentals for the design of bioreactors are presented. It has been attempted to apply theoretical equations suitable for both, low viscosity Newtonian and high viscosity non‐Newtonian fermentation broths. Apart from the calculation procedure for the OTR‐values, the difference between global and local values within bioreactor is demonstrated by means of velocity and shear stress profiles. Special requirements for bioreactors such as prevention of excessive foaming, shear sensitivity of micro‐organisms and cell‐lines and effective sterilization are also discussed.
Collection of fine adhesive and cohesive dusts with pluse‐jet fabric filers
Authors: Schmidt Eberhard , Löffler Friedrich 
Published: August 2005

AbstractThe collection of reactive and therefore extremely adhesive and cohesive fine particles (< 1 μm) by means of bag filters with pulse‐jet cleaning may present problems. The electron‐beam dry scrubbing (EBDS) process, used to remove SO2 and Nox in a power plant of the Badenwerk AG, Karlsruhe, serves as an example. To solve the occurring problems and achieve a satisfactory filter performance, extensive know‐how of process engineering is necessary. This contribution deal with the following aspects: construction of the cleaning system, selection of filter medium, precoating, and dosage of an auxiliary dust during filtration.
Fluid dynamics of pulsed sieve plate extraction columns
Authors: Lorenz Markus , Haverland Hartmut , Vogelphol Alfons 
Published: August 2005

AbstractThe presented contribution reports on comprehensive hydrodynamic investigations in two pulsed sieve‐plate extraction columns (PSE) on a pilot scale. The experiments were conducted with three different sieve plate geometries employing test systems recommended by EFCE, under varying pulsation conditions and throughputs. The results of the investigation add to the existing knowledge of relationships between hydrodynamic parameters, drop size, hold‐up, flooding throughput and mixing and operating parameters. They also provide useful information for scale up, selection of sieve‐plate geometry, most favorable operating range, and constructive design of equipment. On the basis of measurements, analytical methods are recommended for prediction of PSE hydrodynamics.
Effect of mixing behaviour on gas‐liquid mass transfer in highly viscous, stirred non‐newtonian liquids
Authors: Henzler Hans‐Jürgen , Obernosterer Gerd 
Published: August 2005

AbstractWhen declaring and using process engineering data such as, for exmple, mixing times or kLa values, it is assumed that these apply to the entire reactor contents. The condition of uniform mixing, necessary for this, is generally met in the regime of turbulent flow. When highly viscous and, above all, strongly non‐Newtonian liquids are stirred in small reactors, there are frequently also regions of laminar flow and completely stagnant zones, which are only partially mixed or not at all. The present paper pursues the question to what extent is the gas‐liquid mass transfer in stirred, highly non‐Newtonian liquids influenced by the mixing behaviour of the reactor. The results show that, below certain Reynolds numbers, three relatively distinct regions exist, with different mixing intensities. Between an almost ideally mixed region in the vicinity of the stirrer and a completely stagnant and dead one, there is a zone of very slight motion. This finding demonstrates that the usual determination of integral or volume‐based data in the literature is neither logical nor adequate for the case under consideration. Thus, the gas‐liquid mass transfer takes place mainly in the relatively well mixed region. Therefore, use of a kLa value also requires the volume of this region to be declared. Only the knowledge of this volume enables us to correlate the kLa values in such a way that the sorption characteristics thus obtained appear suitable for scale‐up. This procedure, which is illustrated by numerous examples of measured results for different stirrers, is important whenever design data for highly viscous liquids are to be worked out on the basis of laboratory measurements. Only when larger equipment is used, in which turbulent flow can be achieved, this problem does not arise because of the relatively uniform mixing of reactor contents.