bluuebunny/crossref_metadata_2025_split huggingface dataset:
Détermination de constantes cinétiques du craquage catalytique par la modélisation du test de microactivité (MAT)
Authors: Pitault Isabelle , Forissier Michel , Bernard Jean‐René 
Published: March 2009

AbstractLe test de microactivité (MAT), utilisé pour comparer les catalyseurs de craquage, fonctionne avec un réacteur approximativement piston, isotherme et non stationnaire. Les rendements à la sortie d'un tel réacteur sont calculés dans le cas d'un modèle cinétique à familles (lumps), d'une grande expansion molaire et d'une désactivation rapide du catalyseur fonction de la concentration en poison. Le poison (le coke dans le cas du craquage catalytique) est un produit résultant de plusieurs chemins réactionnels.Les résultats sont appliqués à la cinétique du craquage catalytique avec un modèle à 4 familles (charge, essence, gaz et coke).La comparaison entre les rendements observés et calculés, permet l'ajustement des constantes cinétiques à partir d'un groupe d'expériences réalisées dans des conditions variées.La simulation des profils de concentration dans le réacteur, permet une meilleure compréhension du déroulement de la réaction.
Desorption of cadmium from algal biosorbent
Authors: Aldor Ilana , Fourest Eric , Volesky Bohumil 
Published: March 2009

AbstractDesorption of metal‐laden new biosorbent material was studied using batch and column equilibrium elution processes. Equilibrium screening tests of cadmium desorption established a solution of HC1 as the most appropriate eluant at approximately pH 1.0. The desorption of Cd by protons was indicated to be a reversible exchange with a stoichiometric coefficient of 1.24. The solid to liquid ratio (biosorbent mass to elutant volume) is described as a key parameter in determination of elution efficiency, affecting simultaneously the pH at desorption equilibrium, the concentration of cadmium released, and the concentration ratio of the overall metal recovery process. When the pH is maintained constant, the solid to liquid ratio has little influence on metal recovery but still controls the concentration ratio. Recycling a small amount of eluant through a desorption column with metal‐laden biosorbent material resulted in very high solid‐to‐liquid ratios (up to 130 g/L) leading to high value of 70 for the metal concentration ratio of the sorption/desorption process. No loss of cadmium biosorbent properties was observed in three consecutive metal uptake/desorption cycles.
Mathematical modeling of the rotary coke calcining kiln
Authors: Bui R. T. , Simard G. , Charette A. , Kocaefe Y. , Perron J. 
Published: March 2009

AbstractA three‐dimensional steady‐state mathematical model of a rotary calcining kiln for the petroleum coke is presented. The model takes into account all the physical phenomena of interest, from gas flow, heat transfer, volatile matter and coke dust evolution and combustion, to the granular bed motion and the thermal effects of the refractories. The model is built in modular form with several submodels coupled together. This methodology facilitates the construction of the model and its use. This article gives a detailed mathematical description of the model. A complete simulation is presented, and the results are discussed. Data coming from an industrial kiln in operation are used for validation, and the results show that the model can be a useful tool for solving problems of kiln operation or design.
Visual study of an airlift pump operating at low submergence ratios
Authors: Tramba A. , Topalidou A. , Kastrinakis E. G. , Nychas S. G. , Francois P. , Scrivener O. 
Published: March 2009

AbstractThe operation of an airlift pump, working under low submergence ratios (between 0.17 and 0.31), has been visually studied. The two‐phase flow structures occurring in the riser channel and around the injector section were recorded by a high speed video system. A quasi‐periodic burst‐like behaviour characterised the flow pattern in the riser tube, which appeared to dominate the operation of the airlift pump under the conditions of low submergence ratios. An interesting aspect of the airlift pump operation, under these conditions, is that the two phases show a large interface area; this is due to the high dispersion degree of the two‐phase mixture in the riser duct. Data and pictures from video recordings regarding the sequence, time and length scales of the occurring flow patterns are reported.
Wall effect for the fall of spheres in cylindrical tubes at high reynolds number
Authors: Uhlherr P. H. T. , Chhabra R. P. 
Published: March 2009

AbstractNew experimental results on the wall effect for sphere motion in cylindrical tubes are presented and discussed for the conditions d/D ≤ 0.9 and Rem ≤ 20000. Extensive comparisons with previous studies have been carried out to evaluate their predictability and to demonstrate the utility of the present results.The wall factor, defined as the ratio of settling velocity in an unbounded medium to that measured in a cylindrical tube, is found to depend on sphere‐to‐tube diameter ratio and on sphere Reynolds number. However, for small values of the Reynolds number (Re ≤ 0.5), as well for large values (Re ≥ 1000), the Reynolds number dependence of the wall factor disappears; in these regions, only the dependence on diameter ratio remains.
Gas hold‐up and volumetric oxygen transfer coefficient in an aerated agitated vessel without baffles having forward‐reverse rotating impellers
Authors: Yoshida M. , Kitamura A. , Yamagiwa K. , Ohkawa A. 
Published: March 2009

AbstractGas hold‐up and volumetric oxygen transfer coefficient were studied in a gas‐liquid contactor without baffles, containing multiple impellers with four delta‐type blades. The blades of each adjacent impeller were offset by 45° in an alternating manner. The direction of rotation of the impellers periodically was reversed. This new type of agitated gas‐liquid contactor was denoted as “AJITER”. The effects of the gas sparging rate, the forward‐reverse agitation rate and the number of impellers on the gas hold‐up and volumetric oxygen transfer coefficient in the AJITER when different types of gas spargers were used were evaluated experimentally for an air‐water system. Empirical relationships are presented to predict the gas hold‐up and volumetric oxygen transfer coefficient. The differences in performance between the AJITER and existing types of gas‐liquid contactors are discussed in terms of the differences in the gas hold‐up and volumetric oxygen transfer coefficient due to changes in the superficial gas velocity.
Transition to turbulent fluidization in a binary solids fluidized bed
Authors: Bai D. , Masuda Y. , Nakagawa N. , Kato K. 
Published: March 2009

AbstractThis paper presents a study on the transition velocity from bubbling to turbulent fluidization in a binary solids fluidized bed. Experiments were carried out with two kinds of binary solids mixtures with FCC as fine particles and silica sands as coarse particles. The onset velocity to turbulent fluidization, Uc, determined by the measurement of pressure fluctuations, was found to increase with increasing the fraction of coarse/heavy solids. By introducing an equivalent particle diameter and an equivalent particle density, the results obtained in this study can properly be described by a general correlation of Uc proposed by Cai and co‐workers (1989) for mono‐density particles with relatively narrow size distribution.
Experimental study of the tail end selective hydrogenation of steam cracking C2‐C3 mixture
Authors: Godínez C. , Cabanes A. L. , Víllora G. 
Published: March 2009

AbstractDiolefins and alkynes in C2‐C3 olefins streams can be selectively hydrogenated to produce high‐purity mono‐olefins for downstream polyolefin production. The aim of this paper is on the experimental study of the tail end selective hydrogenation of a stream cracking C2‐C3 cut, over two different palladium/alumina catalysts.A series of integral reactor type experiments were performed and the integral method was used for the kinetic analysis. The minimization of the objective function was made by the Marquardt algorithm for multiple response and the continuity equation set integrated by fourth order Runge‐Kutta technique. The comparison between experimental and observed values of the acetylene, ethylene, ethane, MAPD, propylene and propane molar fraction in the hydrocarbon mixture, which were used for the minimization, confirm the suitability of the fit.
Oxidative coupling of methane over a La2O3/CaO catalyst. Optimization of reaction conditions in a bubbling fluidized‐bed reactor
Authors: Mleczko L. , Pannek U. , Rothaemel M. , Baerns M. 
Published: March 2009

AbstractOxidative coupling of methane over a La2O3/CaO catalyst was investigated in laboratory‐scale fluidized‐bed reactors (ID = 5 and 7 cm) in the following range of reaction conditions: T = 700 – 880°C, P = 41 – 72 kPa and P = 6 – 29 kPa. The maximum C2+ selectivity and yield amounted to 73.8% (T = 800°C, X = 13.1%, Y = 9.7%) and 16.0% (T = 840°C, X = 34.0%, S = 47.2%), respectively. Axial gas concentration profiles revealed that C2+ selectivity was not only influenced by oxidative consecutive reactions, but also by steam reforming of ethylene. When diluting the catalytic bed (mcat = 145 g) with quartz (m = 200 and 400 g), a slight decrease of the selectivity (1–2%) was observed. The dilution of the feed gas with nitrogen only led to only a small increase (< 2%) of the C2+ selectivity.
Evaluation of the local composition model for VLE of binary mixtures of triethylene glycol with methane, water and benzene
Authors: Cartaya Eduardo , Harmon Steve , Starling Kenneth E. 
Published: March 2009

AbstractThis work evaluated the predictive accuracy of the local composition model (LCM) formulation developed by Li et al. (1986) for four binary, vapor‐liquid equilibria (VLE) mixtures. The four components comprising these mixtures were benzene, triethylene glycol (TEG), water and methane, while the mixtures examined in this work were the benzene‐TEG, water‐TEG, methane‐TEG and methane‐benzene systems. The Khan‐Chung‐Lee‐Starling (KCLS) equation of state developed by Chung et al. (1984) was used with the LCM to predict the VLE behavior of these systems. The accurate results obtained in this work may be applied to the design of natural gas dehydration processes.
Simultaneous evaluation of effective diffusion coefficients of the substrates in a biofilm with a novel experimental method
Authors: Beyenal Haluk , Tanyolaç Abdurrahman 
Published: March 2009

AbstractIn this study, a pure culture of Zoogloea ramigera was grown as a film on active carbon particles in a differential fluidized bed biofilm reactor (DFBBR) as a novel experimental system for the application of diffusion‐reaction models. The effective diffusion coefficients of the essential substrates; glucose, ammonium ion and oxygen in the active biofilm were simultaneously calculated. The values of effective diffusion coefficients in the active biofilm to those in water varied between 13–34, 48–96 and 28–48% for glucose, ammonium ion and oxygen, respectively, at different biofilm densities, which is in fair agreement with the literature.
Interfacial tension from the height and diameter of sessile drops and captive bubbles with an arbitrary contact angle
Authors: Prokop R. M. , Rio O. I. Del , Niyakan N. , Neumann A. W. 
Published: March 2009

AbstractA method has been developed to calculate the interfacial tension of sessile drops and captive bubbles of arbitrary contact angle by measuring the drop diameter and vertical distance to the apex at arbitrary horizontal planes within the drop. The procedure works in theory for any contact angle with an accuracy on the order of 0.1%. However, practical limitations reduce the range of angles to roughly 50°–180° but do not restrict the range of interfacial tensions (at least 0.01 mJ/m2 to 72.0 mJ/m2). The optimal strategy is to use the method at several points on a single drop and to calculate the mean and standard deviation of the resulting interfacial tensions.
Population balance models of autonomous periodic dynamics in microbial cultures. Their use in process optimization
Authors: Hjortso Martin A. 
Published: March 2009

AbstractOscillations in continuous microbial cultures are well documented for baker's yeast. The oscillations can be modeled by unstructured population balance models in which a key cell cycle parameter, such as the division age, is a function of the substrate or product concentration.The state variables of the periodic solutions exhibit average values different from those of steady state cultures. This suggests that oscillating cultures can be used to optimize microbial processes. Models analyzed here indicate that the possible improvements of oscillating cultures over steady state cultures are insignificant when the cultures are harvested continuously but not when harvested periodically.
Reactor performance and stability in an alternating reaction‐reheat paraffin dehydrogenation system
Authors: Ercan C. , Gartside R. J. 
Published: March 2009

AbstractThe classical fixed bed C3–C4 paraffin dehydrogenation process is a cyclic operation in which the reactor alternates between reaction and reheat cycles. During the reheat cycle, the necessary energy for the dehydrogenation reaction is stored in the fixed bed by passing hot air through it. In this established technology, both the hydrocarbon reactant and the reheat hot air are fed into the fixed bed from the same end (top) of the reactor. This is termed parallel flow (cocurrent) operation. An alternative feeding fixed bed has the hydrocarbon reactant and the reheat air entering from the opposite ends of the reactor. This is termed reverse flow (countercurrent) operation. This alternate creates an ideal temperature profile for an equilibrium limited endothermic reaction (rising temperature profile along the reactor). The transient flow behavior of both parallel and reverse flow reactors has been modelled and the dynamics of temperature profile development for both concepts have been analyzed. Based upon the model predictions, the characteristics as well as the reactor stability of the both concepts have been discussed.
Dynamic operation of butadiene dimerization reactor undergoing catalyst deactivation
Authors: Dixit Ravi S. , Grant Nancy 
Published: March 2009

AbstractOperation of fixed‐bed catalytic reactors undergoing catalyst deactivation has been investigated as an optimal control problem to yield optimal temperature policies. An efficient numerical scheme using a control vector iteration method based on gradients in functional space is developed. The procedure is applied to develop optimal temperature profiles for a butadiene dimerization process. The temperature‐time trajectories and dynamic activity profiles are strongly influenced by kinetics. A sensitivity analysis is done to study the effect of flow rates, conversion level and parameters that influence kinetic and deactivation processes. These results have been validated with experimentation on a lab scale reactor and a 9.14 m pilot‐plant reactor.
Catalytic SO2 oxidation in a periodically operated trickle‐bed reactor
Authors: Lee Joong Kee , Ferrero Stefano , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractCentaurTM carbon (Calgon Carbon Corp.) was used as a catalyst for SO2 oxidation in a trickle bed under periodic interruption of its liquid flow for cycle periods from 15 to 60 min, cycle splits (split being the proportion of a cycle in which liquid flows) from 0.0083 to 0.2, and feed temperatures about 80°C.SO2 removal in the trickle bed was improved at longer periods. At a fixed period of 15 min, a maximum occurred with split. At high splits, platinized and unplatinized carbons performed indistinguishably. Results suggested kinetic rate control at low splits and oxygen mass transport control at high splits.
The transient operation of a solid oxide fuel cell monolith under forced periodic reversal of the flow
Authors: Neophytides S.G. , Tripakis A. 
Published: March 2009

AbstractThe forced periodic reversal of the flow is proposed for the case of a Solid Oxide Fuel Cell (SOFC) monolith. A one‐dimensional non‐steady state heterogeneous model is applied to an investigation of H2 electrochemical oxidation in a co‐current flow solid oxide monolithic fuel cell. Results are reported on the transient evolution along the reactor, of the species conversion, temperature distribution, thermodynamic energy conversion efficiency and volumetric power density. This novel transient operation of an SOFC leads to improved and highly efficient performances, thus allowing for a combination of the concepts of a regenerative heat preheater and of an electrocatalytic converter, in a single SOFC monolithic assembly.
The STAR configuration for methanol synthesis in reversed flow reactors
Authors: Vanden Bussche K. M. , Froment G. F. 
Published: March 2009

AbstractAlthough the transient reversed flow operation of a fixed bed reactor for methanol synthesis was shown to be an economically attractive alternative for the traditional steady state technology, it suffers from strongly varying exit concentrations upon flow reversal. These not only disturb the operation of downstream equipment but also significantly decrease the time averaged conversion to methanol.To avoid this drawback, the STAR reactor concept is introduced. It operates in a fully transient mode, but combines the attractive features of the reversed flow reactor operation with practically constant exit concentrations. Extensive simulation work shows that the conversions obtained exceed those of the single reversed flow reactor by at least 5 percent.
Extension of EOS non‐iterative methods to density calculations: Correlation of saturated molar volumes and heats of vaporization
Authors: Zabaloy Marcelo S. , Vera Juan H. 
Published: March 2009

AbstractSoave's direct calculation procedures for the vapor pressure of pure compounds with cubic equations of state (EOSs), have been extended to the calculation of phase densities at saturation for Peng‐Robinson (PR) type EOSs. These universal relations have been used to propose EOS‐based correlation methods for the pure compound saturated liquid and vapor molar volumes, at temperatures higher than the normal boiling point. The methods yield satisfactory results independently of the molecular nature of the chemical under consideration. The results for phase densities are used to correct the heats of vaporization predicted by the ZVPR‐EOS. Complete relative error information is provided for calculated heats of vaporization and correlated vapor and liquid phase molar volumes for more than one hundred compounds of industrial interest.
Factors influencing the efficacy of an interfacial modifier for the interface in an immiscible polymer blend
Authors: Favis Basil D. , Cigana Patrick , Matos Mireya , Trembla Alain 
Published: March 2009

AbstractThe modification of the interface in immiscible polymer blends is critical in order to optimize physical properties. Despite the great commercial importance of polymer blends, many aspects of the emulsification process remain unclear In this paper, it will be shown that an emulsification curve can be used to estimate the influence of the architecture molar mass of styrene/hydrogenated butadiene block copolymer interfacial modifiers on the emulsifion of polystyrene/ethylene‐propylene rubber blends under melt processing conditions. An expression for eing the critical amount of copolymer to saturate the interface, as well as aspects concerning the localisation of the modifier in the blend system will also be addressed.
The catalytic oxidative coupling of methane: II. Axial gas sample probing in a bubbling Fluidised‐Bed reactor and the effect of side reactions
Authors: Do K. T. , Edwards J. H. , Tyler R. J. 
Published: March 2009

AbstractThe atmospheric pressure catalytic oxidative coupling of methane was studied in detail by axial gas concentration probing experiments in a 60 mm OD bubbling fluidised‐bed reactor system. Experimental data demonstrated a very fast reaction which occurred within the vicinity of the distributor (normally in the first 5 mm of bed height) under normal reaction conditions of 850°C and 83 vol%/17 vol% CH4/O2 feed. The data also showed that hydrocarbon selectivity was deleteriously affected by side reactions which were also promoted by the catalysts even though they were good catalysts for the oxidative coupling reaction. If this reduction in hydrocarbon selectivity is inevitable then there will be optimum operating conditions for each catalyst in the bubbling fluidised bed reactor.
Kinetics of iodine poisoning of hydrophobic Pt/SDBC catalyst for hydrogen isotopic exchange reaction
Authors: Wei Yue‐Zhou , Shimizu Masami , Takeshita Kenji , Kumagai Mikio , Takashima Yoichi 
Published: March 2009

AbstractChanges with time in the isotopic exchange reaction rate between H2 and HDO(v) over a hydrophobic Pt/SDBC (styrene‐divinylbenzene copolymer) catalyst induced by iodine have been studied experimentally. The addition of a trace amount of I2 to the reactor caused a remarkable decrease in the activity of the catalyst. The measurement results by means of the gas chromatographic pulse technique show that the H2 adsorption onto the catalyst surface was strongly inhibited by iodine. A kinetic model for the poisoning was developed in terms of the competitive adsorption of I2 with H2 onto the catalytic active site. The experimental results were explained reasonably by the proposed kinetic model based on the site balance by assuming that I2 adsorbs non‐dissociatively on the active site. The poisoning could be prevented by the conversion of I2 to I− or IO3−through redox reactions.
Arma neuron networks for modeling nonlinear dynamical systems
Authors: Krishnapura Venugopal G. , Jutan Arthur 
Published: March 2009

AbstractA new neuronal structure, the ARMA neuron, is proposed here. These new neurons are designed for modeling nonlinear dynamics often encountered in chemical engineering processes. They are an extension of standard neurons which are used for static process modeling. These new neurons contain internal input/output dynamic structure and can model dynamic non‐linearities in a flexible manner. A nonlinear output transformation is used here as opposed to a linear version used earlier (Krishnapura and Jutan, 1993). New algorithms for training networks comprised of the new ARMA neurons are developed using the backpropagation approach. The ARMA neurons are used to model both simulated and experimental nonlinear dynamic processes, including an industrial fluidized bed reactor.
Investigation of the oxidation of o‐Xylene over a Vanadia/Titania catalyst by means of the TAP reactor
Authors: Creten Glenn , Froment Gilbert F. , Kopink Frank‐Dieter 
Published: March 2009

AbstractThe oxidation of o‐xylene over a commercial V2O5/TiO2 (anatase) catalyst was studied in the TAP (Temporal Analysis of Products) reactor system. The transient method with high time resolution has led to new insights into the reaction mechanism. The selective oxidation is shown to consist of a sequence of steps, involving intermediates which desorb as o‐toluolaldehyde and phtalide. The key reaction step in the non‐selective oxidation is shown to be a decar‐bonylation of a surface species, leading to a surface benzoate. The kinetics of the elementary steps in the reaction were derived from a quantitative analysis of the transient responses on o‐xylene pulses.