bluuebunny/crossref_metadata_2025_split huggingface dataset:
Search for optimal geometry of a conical turbine agitator for heat transfer in stirred vessels
Authors: Strek Frederyk , Karcz Joanna , Bujalski Waldemar 
Published: August 2005

AbstractSimultaneous measurements of power consumption P and heat transfer coefficient α for a jacketed, baffled, agitated vessel of diameter D = 0.45 m, equipped with a conical turbine, were carried out. The following geometric parameters of the agitator were tested: diameter d, blade width b and number Z, and distance from the bottom of the vessel to the lower edge of the blade h. The results of these investigations were generalized mathematically. On the basis of optimization, the best geometric parameters with respect to heat transfer are proposed for the conical turbine agitator.
Monte carlo simulation of transient CSD in a continuous crystallizer
Authors: Gupta Bhaskar Sen , Dutta Tapas Kumar 
Published: August 2005

AbstractA Monte Carlo simulation scheme is proposed for transient crystal size distribution in a continuous crystallizer. The suggested scheme can taken into account dispersion effects of growth rate, shape factor and birth size on crystal size distribution. This method is simple and more versatile than solution of the number balance equation or the finite‐state Markov chain model. The proposed algorithm of the process has a very simple structure and can be easily implemented on a personal computer. The present contribution is extension of an earlier work of Sen Gupta and Dutta.
Cooling of arc furnace electrodes with heat pipes
Authors: Bullerschen Klaus‐Gerd , Wilhelmi Herbert 
Published: August 2005

AbstractCombination electrodes with water cooling shanks, which have been introduced to reduce graphite consumption in UHP furnaces, cause the danger of vapour explosions in case of breakIng. Heat pipes are highly efficient two phase heat conductors which could provide a safer alternative to water cooling shanks, since they contain only a small amount of liquid. The transport of energy results from evaporation of the working fluid in the heated section, convection of the vapour to the cooled section and reflux of the condensed fluid to the heated end. Large heat quantities can be transferred under nearly isothermal conditions within the tube, as long as certain limits are not exceeded. The operating temperature can be controlled by design parameters such as the thermal resistance of the cooling zone. The proper function of heat pipes for cooling arc furnace electrodes is investigated by comparing the calculated heat load with temperature dependent limits to heat transport. It is shown that copper tubes with water as the working fluid combine efficient cooling and safe performance in the low temperature range, while the cheaper steel tubes with sodium filling are suitable for high temperature operation.
Adsorption and desorption of halogenated hydrocarbons using activated carbon
Authors: Schäfer Manfred , Schröter Hans‐Jürgen , Peschel Gerhard 
Published: August 2005

AbstractEnvironmental hazards caused by halogenated hydrocarbons and increasingly stringent regulations for limiting their emission require comprehensive investigations of these substances. The present work deals with the adsorption and desorption of halogenated hydrocarbons on activated carbon. The results could be useful in the utilization of landfill gases because halogenated hydrocarbons must be removed in order to avoid pollution and the loaded activated carbons have to be regenerated. Activated carbons are well suited to removal and recovery of halogenated hydrocarbons from gas flows.
Coke removal from a zeolite catalyst by supercritical fluids
Authors: Manos Georgios , Hofmann Hanns 
Published: August 2005

AbstractIn the study of the possible coke removal from zeolite catalysts, the solubility of polyaromates in supercritical fluids (SCF) was determined, showing that it becomes drastically reduced with increasing molar mass. Experiments with supercritical ethyl benzene and benzene showed that only coke precursors can be dissolved and, therefore, complete coke removal by SCF is impossible but it has been confirmed that, under supercritical conditions, deactivation of the catalyst could be slowed down.
On the falling‐rate period
Authors: Schultz Peter 
Published: August 2005

AbstractA fixed bed of glass particles, wetted with water, was dried from above. The measured moisture profiles within the sample show that its surface is not completely dry during the falling‐rate period. Hence, the current view, according to which the moisture front retreats into the sample directly after reaching the critical moisture content, has to be revised. Assuming that parallel dry and wet channels form within the sample during the constant‐rate period, the onset of the falling‐rate period depends only on the diameter of these channels. If the moisture is distributed very finely, a large number of channels with a small diameter have to be considered. The falling‐rate period for this system occurs at low moisture contents. For a coarse distribution of moisture, fewer channels with a large diameter should be assumed. Their drying rates show the beginning of the falling‐rate period already at high moisture contents. A good agreement between measured and calculated drying rates could be achieved by fitting the channel diameter. Only for very low moisture contents, is the agreement poor. This is to be expected, because the measured moisture profiles show a completely dry sample surface for these moisture contents, indicating that the moisture front has already retreated into the sample.
Mass transfer to regular packings in single phase
Authors: Colazo Jorge A. , Nieva Isabel A. , Böhm Ursula 
Published: August 2005

AbstractA study of mass transfer to regular packings by the electrochemical technique is presented in this paper. The excellent properties of radial mixing were verified and the correlation for mass transfer rate was also obtained. It was found that the energy efficiency, which is represented by the LeGoff number, is higher than that of other packings due to the low pressure drop shown by these arrangements.
Theoretical analysis of gas stripping performance of spray towers
Authors: Beg Shafkat A. , Rehman Syed Obaidur , Hassan Mirza M. 
Published: August 2005

AbstractA simplified model has been developed to describe ammonia stripping process in spray towers. The effect of various operating parameters including air flow rate, contact time, droplet size, liquid to gas ratios and tower height on the performance of such systems has been studied in detail. The results obtained for ammonia stripping have been compared with the limited experimental data available in literature. The predicted results agree reasonably well with the reported experimental data.
Sensitivity analysis in static optimization of fermentation plants
Authors: Posten Clemens 
Published: August 2005

AbstractBiotechnological processes are often characterized by uncertain model parameters, input variables which are difficult to handle and ill defined cost functions. Nevertheless, it is desirable to define optimal operating points. Starting with a robust approach for numerical optimization, the paper presents three different methods for evaluating the sensitivity of an optimal operating point to uncertain parameters or disturbances of the input variables. It is shown that sensitivity analysis can provide useful guidelines for designing biotechnical plants with invariant optimum operation in the presence of changing inputs or parameters.
Particle structure change of CaO during high temperature sulphatization
Authors: Bjerle Ingemar , Ye Zhicheng 
Published: August 2005

AbstractThe effects of particle size (layer thickness), BET surface area and pore size distribution on the reactivity of CaO derived from limestone were studied by using a pH‐stat and the BET method. Visual analysis was obtained with SEM, and X‐ray diffraction was used to determine the crystalline components present. It was found that the pore size distribution, including pore volume and pore surface distribution, affected the sulphatization behaviour. The larger pores (D > 50 Å) with their pore volume and pore surface were to some extent responsible for both initial reactivity and ultimate capacity of CaO.
Method of multiobjective optimization for imprecise objectives
Authors: Kraslawski Andrzej , Rzyski Edward , Stelmach Jacek 
Published: August 2005

AbstractA method of multiobjective optimization for imprecise objectives is presented. The problem consisted in a minimization of the distance between the set of admissible solutions and an ideal point. Applicability of the method is illustrated by the choice of best impeller from a group of seven different types tested. The optimum process conditions were selected, taking as optimization objective the maximization of kLa and minimization of PG.
Performance of construction materials in multiphase liquid/solid flows
Authors: Ehmann Ingo , Heitz Ewald 
Published: August 2005

AbstractThe transport of corrosive liquids containing solids, in conventional energy and process technology as, for example, in oil and gas production, places high demands on the selection of materials for plant construction. A discussion on the chemo‐mechanical load demonstrates the significance of hydrodynamics in selecting the test method. Choosing a pipe with an abrupt expansion of cross‐section as a flow model yields a new method of simulating operation conditions. By subjecting ferrous materials used for hydraulic machinery to representative media from three important industries, a broad spectrum of results can be obtained. Classification of the results leads to four basic types of mass loss behaviour in materials as functions of flow rate. These findings yield guidelines for the selection of materials and the dimensioning of flow equipment.
Water determination in pyrolysis gases using calcium carbide
Authors: Lindblom Mats , Andersson Lars A. , Bjerle Ingemar 
Published: August 2005

AbstractA method for the measurement of water content in a flowing gas has been developed. It consists in passing warm moist gas through a bed of CaC2 where the water vapour is adsorbed and reacts directly with the carbide to form C2H2, which is then analyzed in a gas chromatograph. In this work, water vapour concentrations ranged from 1000 to 13000 ppm at a minimum pressure of 10 bar. The method has also been applied in a number of pyrolysis experiments.
Kinetics of carbon dioxide absorption in aqueous solutions of diisopropanolamine
Authors: Sotelo Jose L. , Benitez F. Javier , Beltran‐Heredia Jesus , Rodriguez Concepcion 
Published: August 2005

AbstractA bubble column absorber was used to investigate kinetics of the reaction between carbon dioxide and aqueous solutions of diisopropanolamine (DIPA), by means of gas absorption experiments. These were conducted in the temperature range of 20 to 40°C, with DIPA concentrations from 5 to 500 mol/m3, and CO2 partial pressures between 5 and 101 kPa. A model based on the Danckwerts' surface reneval theory was used to analyze the experimental results and to determine the rate constant. The obtained data support the assumption of a second‐order overall reaction, with the rate constants being well correlated by the Arrhenius equation:
Agitation and effective nucleation in forced circulation magma crystallizers
Authors: Gerigk Markus J. , Offermann Hans 
Published: August 2005

AbstractA new model is derived to establish the effective nucleation rate in terms of the MSMPR‐theory. The model is based on the concept of two‐step crystal growth, secondary nucleation, nuclei activation and metastable supersaturation. A comparison between model prdictions and experimental data from different crystallizers is presented. This model, which integrates hydrodynamics directly into its theory, proves to be extremely suitable for describing the MSMPR‐crystallization process.
Degradation of lignin with monomethylamine
Authors: Peter Siegfried , Gotz Rolf 
Published: August 2005

AbstractWood chips were treated with gaseous mixtures of monomethylamine and water vapour at temperatures between 160 and 120°C and pressurs ranging between 1.5 and 7.0 MPa. The degradation products were subsequently extracted with different solvents at ambient pressure. First, The degradation products of lignin were extracted with highly selective organic solvents such as diethyl ether or 2‐butanone. Then, the remaining decomposition products were extracted with water or an aqueous solution of monomethylamine. The latter extract contains the degradation products of the hemicelluloses in a relatively high concentration. After a three hour digestion, the residue obtained from spruce had a lignin content of 3.1 wt‐% (pine: 3.7 wt‐%; birch 0.3 wt‐%). The total yield of unbleached cellulose was approximately 60 wt‐%.
Liquid circulation in columns due to bubble drift
Authors: Millies Marco , Mewes Dieter 
Published: August 2005

AbstractThe profiles of liquid velocity and gas hold‐up in convection cells of bubble columns were calculated numerically. Development of a circulation cell was calculated from momentum and mass balances. Breakdown of the circulation cell was calculated taking into account the drift motion of bubbles ascending in accordance with the velocity gradient of the liquid. A limit of stability for the development of circulation cells has been obtained.
Characterization of a photochromic triaryl methane dye sulphite for use as a tracer in the visualization of water flows
Authors: Douglas Peter , Enos Richard D. 
Published: August 2005

AbstractThe chemical and photochemical properties of a photochromic water soluble triaryl methane dye sulphite, acid magenta monomethyl magenta sulphite, (AMMM · SO3)4−, have been examined, and the application of this photochromic system to the visualization of water flows is discussed. Addition of sulphite to an aqueous solution of the parent dye acid magenta monomethyl magenta, AMMM2−, (a methylated derivative of acid magenta, C.I. acid violet 19) leads to formation of the colourless sulphite complex, (AMMM · SO3)4−. Pulsed irradiation of a solution of this compound, with light of wavelength shorter than ≈ 340 nm, causes transient production of the parent dye, whose lifetime is influenced by pH, sulphite concentration, temperature and ionic strength. Longest useful lifetimes are of the order of a few seconds and a general equation is presented for the calculation of dye lifetimes for a variety of conditions. The complex formation constant for (AMMM · SO3)4− is 1.8 (± 0.2) × 105 M−1, while that for the weakly photochromic hydroxide (AMMM · OH)3− is 1.3 (± 0.3) × 106 M−1. The quantum yield of dye production at 308 nm is ≈ 0.5 – 1.0, and this is discussed along with the absorption spectra of AMMM2− and (AMMM · SO3)4− with respect to the penetration characteristics of a pulse of 308 nm laser radiation with an energy of a few millijoules. The action spectrum for dye production from (AMMM · SO3)4− suggests that there is a non‐photochromic absorption band at about 350 nm, an assumption which is supported by the failure to detect efficient dye production when using 355 nm excitation from a Nd/YAG laser.
Optimization and adaptive control of a semi‐batch synthesis reactor
Authors: Uhlemann Jens , Cabassud Michel , Le Lann Marie‐Véronique , Borredon Elisabeth , Casamatta Gilbert 
Published: August 2005

AbstractThe optimization of a chemical synthesis aims at an adjustment of the operating conditions, i.e. pH, temperature and initial concentrations, in order to obtain maximum yield, minimum operating costs or similar. The optimization effort may be considerable so that, in many cases, its cost cannot be justified, especially for small volume products. This paper introduces a new strategy, namely to establish the optimum operating conditions with a relatively small effort. The new approach is illustrated by the synthesis of 2‐furyl oxirane. In the first step, a simplified mechanistic process model has to be determined on the basis of easily accessible experimental data. Initial and final concentrations of all reacting components, reaction time and temperature must be known. A two‐step evaluation yields the stoichiometric coefficients of all the occurring reactions as well as the parameters of the Arrhenius model. This so‐called trend model is used in the optimization of the operating conditions. It is not only important to know the optimum operating conditions but also to maintain them as close as possible in practical operation. An adaptive controller is well suited to such an application and its use is discussed.
Kinetics and mechanism of oxidative coupling of methane over sodium‐manganese oxide catalyst
Authors: Golpasha Rahmatolah D. , Karami Davood , Ahmadi Reza , Bagherzadeh Ebrahim 
Published: August 2005

AbstractThe kinetics of methane oxidative coupling (OCM) was studied using 1 g of Na‐Mn2O3 catalyst at 1073 to 1123 K, in an integral flow reactor (I.d. = 10 mm), at atmospheric pressure with methane and oxygen partial pressures of 0.27 and 0.13 bar, respectively, so that the ratio of CH4 to O2 was 2. The flow rate range was 50 to 200 ml/min. the kinetic data were analyzed by the Rideal‐redox type of rate equation assuming the methyl radical and active surface oxygen to be the steady‐state intermediates. Oxidation and reduction rate constants (Kox, Kred) for methane consumption were calculated from experimental catalysis results by computer simulation using the multiple least squares method. The activation energies at rate constants Kox and Kred for this type of catalyst were reported as 43.26 and 62.2 kcal/mol, respectively.
Liquid phase oxidation of α‐pinene initiated by ozone. 1. Conversion of α‐pinene and formation of its hydroperoxide
Authors: Encinar José María , Beltrán Fernando J. , Frades Jesús María 
Published: August 2005

AbstractThe use of ozone as initiating agent in the liquid phase oxidation of α‐pinene has been investigated. The first intermediate product of the reaction is the hydroperoxide of α‐pinene. Both, ozone partial pressure and its initiation time exert an inhibiting effect on the conversion of α‐pinene but yield higher selectivities for the hydroperoxide of α‐pinene compared with those of oxidation without ozone. In all cases, temperature was found to be the most important variable affecting the oxidation rate. From a mechanism of radical reactions, kinetic equations, consistent with the experimental results, corresponding to α‐pinene oxidation rate and net formation rate of its hydroperoxide, were obtained. The rate constants are given as functions of temperature. The results also suggest that a fraction of the hydroperoxy radicals decomposes to yield other products such as verbenol and verbenone, identified in this work, and whose kinetics will be reported in a later paper.
Thermal analysis of solids production processes
Authors: Mersmann Alfons , Franke Jürgen 
Published: August 2005

AbstractThe present work investigates the energy consumption of a solids production process. Such a process consists of three different operation units: crystallization/precipitation, solid‐liquid separation by centrifuges or filters and drying of wet crystals. Each unit is analyzed with the objective of minimizing the energy consumption. Operating conditions, process design and other characteristic parameters (crystal size, porosity and physical proporties) are discussed with the aim to evaluate their influence on the process.
Transient behaviour of an impulsively heated fluid
Authors: Brown Matthew A. , Churchill Stuart W. 
Published: August 2005

AbstractApproximate as well as reasonably exact numerical solutions of the equation of conservation have previously predicted that sudden heating of a solid surface adjacent to a region of gas will generate a slightly supersonic wave with small positive amplitudes in pressure, temperature and density, and thereby a small mass velocity in the direction of wave propagation. If the gas is confined by a second parallel surface, the wave is predicted to be reflected repeatedly from both surfaces and to decay slowly due to viscous and thermal dispersion. This process, which has been termed thermoacoustic convection, is presumed to result in transient heating of the confined gas and heat transfer through it at rates greatly exceeding that of pure thermal conduction. The current work constitutes the first quantitative experimental confirmation of this behaviour. Numerical solutions obtained for support and guidance of the experimental work define for the first time the conditions required for the generation of a wave of significant strength.
Effect of filling method on the packing distribution of a catalyst bed
Authors: Šmíd Jiří , Van Xuan Pham , Thýn Dr. Jiří 
Published: August 2005

AbstractThe bulk density of a catalyst bed in two‐dimensional reactor model has been measured by a radiogauging method. Three ways of introducing the catalyst were used. Attention was paid to bulk density near the wall and the bottom of the model. A homogeneous distribution of the catalyst was obtained in the case of the “rainy” (uniform) filling method using a grid distributor.
Bed collapse technique for estimating parameters of generalized wake model for a three‐phase fluidized bed
Authors: Jin Yong , Zhang Junping , Yu Zhiqing 
Published: August 2005

AbstractThe hydrodynamic behaviour of a cocurrent gas‐liquid‐solid fluidized bed was studied by using the bed collapse technique. The key parameters, k and x, of the generalized wake model were estimated. Compared with other existing methods for evaluating the parameters k and x, the bed collapse technique shows some distinct advantages. Parameters are derived directly from experiments in a three‐dimensional three‐phase fluidized bed and there is no need to assume that a bubble and its wake form a perfect sphere. Hold‐up data of the three‐phase fluidized bed predicted by the generalized wake model with k and x estimated by the bed collapse technique are in good agreement with those obtained via the traditional pressure‐drop method.
Influence of solids concentration and static mixers on fluid dynamics in three‐phase fluidized bed bioreactors
Authors: Potthoff Matthias , Bohnet Matthias 
Published: August 2005

AbstractThe influence of solids concentration and static mixers on the hydrodynamics of the gas phase was studied for a three‐phase fluidized bed bioreactor (air, nutrient solution, biocatalyst Ca alginate beads). Axial gas hold‐up profiles, radial gas velocity profiles, mean bubble diameter and gas/liquid interfacial area per unit volume were measured in a bubble column (DR = 0.142 m, HR = 1.748 m). The influence of solids concentration on the gas hold‐up is insignificant; static mixers enhance the gas hold‐up in the reactor volume element in which they are installed. Axial gas velocity decreases with increasing solids concentration. At high solids concentrations, static mixers exert little influence on the gas phase but, at low concentrations, they do. A model is suggested to describe the influence of solids concentration (characterized by turbulent viscosity vt) and static mixers (characterized by profile parameter n) on the gas velocity profile.
Interfacial tension in systems with a supercritical component at high pressures
Authors: Hiller Norbert , Schiemann Hartmut , Weidner Eckhard , Peter Siegfried 
Published: August 2005

AbstractInterfacial tension of the binary systems pelargonic acid/ethane, pelargonic acid/carbon dioxide, linoleic acid/ethane, and linoleic acid/carbon dioxide was measured at 313, 333, and 353 K and pressures ranging up to 250 bar, using the capillary rise and Du Nouy ring methods. Both these methods yield similar values. The surface excess of supercritical components is deduced from the measurement results with the aid of Gibbs adsorption equation. The surface excess concentration increases with increasing gas activity, runs through a pronounced maximum, later decreasing rapidly to very small values. Near the surface excess maximum, a falling film of fatty acids disintegrates into a mist of tiny droplets.