bluuebunny/crossref_metadata_2025_split huggingface dataset:
Atmospheric spouted bed combustion: The role of hydrodynamics in emissions generation and control
Authors: Konduri Ravi K. , Altwicker Elmar R. , Morgan M. H. 
Published: March 2009

AbstractRecent studies have reaffirmed the utility of spouted beds as potential combustion devices for a variety of fuels: solid, liquid and gaseous fuels (Arbib and Levy, 1982; Weinberg et al., 1988; Zhao et al., 1987; Altwicker et al., 1989; Altwicker and Lin, 1991; Altwicker et al., 1993; Konduri et al., 1994). In this study, the role of annulus residence time on the performance of such a spouted bed combustor is investigated. The experiments presented here show that fluid hydrodynamics in the annulus of a spouted bed combustor can significantly influence the overall performance; changing the residence time in the annulus significantly affects the concentrations of products due to incomplete combustion at the exit of the combustor. The annular residence time is varied by changing the shape of the bottom of the reactor, by introducing a draft tube and by changing the bed heighn. Propane is used as the fuel and sand as the bed medium. Inferences from the combustion results are supported by pressure and temperature profiles. A streamtube model (Lim and Mathur, 1976) was used to obtain an estimate of the residence time in the annulus. It is concluded that the flame processes taking place at the top of the annulus play a critical role in the emission generation and that more information is needed to understand the annulus‐flame.
Isobaric vapour‐liquid equilibrium for the binary mixtures of 1‐bromobutane with isomeric butanols at 40.0 and 101.3 kpa
Authors: Artigas Hector , Cea Pilar , Dominguez Magdalena , Royo Felix M. , Urieta Jose S. 
Published: March 2009

AbstractA dynamic recirculating still was employed to measure isobaric vapour‐liquid equilibrium at 40.0 and 101.3 kPa for the binary systems 1‐bromobutane and each of the isomers of butanol. All mixtures show azeotropes at both pressures. The experimental VLE data are thermodynamically consistent and were correlated using Margules, Van Laar, Wilson, NRTL and UNIQUAC equations.
Operations optimization and control design for a petroleum distillation process
Authors: Mizoguchi Atsushi , Marlin Thomas E. , Hrymak Andrew N. 
Published: March 2009

AbstractProcess automation involves both steady‐state optimization and feedback control. In this paper, the economic optimum steady‐state operating conditions for a petroleum crude distillation process are determined using a tray‐to‐tray model. This model is used to evaluate the steady‐state operation achieved with several multivariable process control designs. Only one controller design was found to result in essentially optimum steady‐state operation; others deviated significantly. The method applied in this paper relies on a knowledge of the key disturbances occurring in the process; good economic performance may not be obtained should other disturbance types occur. The results demonstrate the importance of implementing the operations optimization through a control strategy which will respond properly to disturbances.
The effect of geometrical parameters on the flow field of an opposed jet rim mix head: Equal flow and matched fluids
Authors: Johnson David A. , Wood Philip E. , Hrymak Andrew N. 
Published: March 2009

AbstractThe effect of geometrical parameters on the flow field present in the mix head used in reaction injection molding (RIM) are presented for Red (Red = 4Q/πdv, nozzle diameter d, fluid kinematic viscosity v and the volumetric flow rate Q through the nozzle) representative of commercial practice. Quantitative velocity measurements of the flow field in a mix head have not been reported in the literature despite the extensive use of the mix head for reaction injection molding. Flow visualization and velocity measurements using a laser Doppler anemometer have been obtained for different values of geometrical parameters such as mix chamber diameter (D), distance from the nozzle inlet to the closed end of the chamber (H), and nozzle needle position (N). The ratio of the mix chamber to nozzle diameter (d) (D* = D/d) was a significant parameter affecting the flow field. The distance from the impingement point to the closed end of the chamber was found to have little effect on the observed flow field beyond the impingement area. A nozzle needle position that partially constricted the nozzle opening was found to decrease the axial distance to unidirectional flow within the mix chamber.
Axial dispersion in a reciprocating plate column
Authors: Lounes Mustapha , Thibault Jules 
Published: March 2009

AbstractAxial mixing in a reciprocating plate column with different amplitudes has been investigated for single‐phase and two‐phase (air‐water) systems. Experiments were performed in water in a semi‐batch scheme (no water flow) in a 1.26 m high and 101.6 mm internal diameter column.It was found that the axial dispersion coefficient is a strong function of reciprocation speed and amplitude. The presence of gas considerably affects the axial dispersion coefficient but its contribution appears to saturate at low gas flow rates and then, over a large range of gas flow rates, the axial dispersion coefficient was almost constant. Models are proposed based on experimental data to account for the effects of gas superficial velocity, amplitude and reciprocating frequency. The models predictions are compared with experimental data, obtained over a wide range of operating conditions, and the agreement between them was found to be good. A new class of nonlinear models, for which it is not necessary to have a constant dependency on each operating variable, was also used to correlate the axial dispersion coefficient. This new model allows to carry out sensitivity analysis on each operating variable.
A new investigation of the metzner‐otto concept for anchor mixing impellers
Authors: Tanguy P. A. , Thibault F. , De La Fuente E. Brito 
Published: March 2009

AbstractAnchor impellers are commonly used for the homogenization of non‐Newtonian fluids, often in association with a set of coaxial turbines. The optimal design of such mixers relies on the knowledge of power drawn by the individual impellers. In non‐Newtonian mixing, this can be readily obtained using the Metzner‐Otto (1957) concept. In this article, the Metzner‐Otto concept and the determination of the constant Ks for anchor impellers have been revisited using numerical and experimental techniques for the case of shear‐thinning and shear‐thickening fluids. Contrary to literature findings, it is shown that the constant Ks does not vary strongly with the power law index and that, for mixer design purposes, the use of a constant value of Ks for each of the rheological behaviors considered is adequate.
A study of autoxidation reaction fouling in heat exchangers
Authors: Wilson D. Ian , Watkinson A. Paul 
Published: March 2009

AbstractThe mechanism of autoxidation reaction fouling in single phase liquid heat transfer under turbulent flow conditions was studied using model solutions of indene in lube oil recirculated through a tubular fouling probe which permitted both thermal and mass deposition measurements. The fouling rate was initially constant, and then accelerated as polyperoxide gums reached their solubility limit. Deposit composition and morphology in the tubular device are compared with results obtained in an annular probe with a short heated length. The initial fouling data collected over surface temperatures of 180−255°C and flow velocities of 0.5–2.6 m/s (Re = 3000 − 16000) gave reasonable agreement with a boundary layer reaction model.
Impurity effects on crystallization of KCL from aqueous solutions in a MSMPR crystallizer
Authors: Dash S. R. , Rohani S. , Sokhansanj S. 
Published: March 2009

AbstractExtensive experimental investigations into the effect of magnesium and sulfate ionic impurities on cooling crystallization of KCl were carried out in a steady‐state Mixed Suspension Mixed Product Removal (MSMPR) crystallizer. The impurities selected for investigation were chosen from those naturally associated with KCl in potash industry. Eighty one experiments were performed in a factorial experimental design scheme. The results exhibited that magnesium ion did not have any significant influence upon crystallizations of KCl, while the sulfate ion enhanced the aggregation rate. The nucleation rate was only slightly affected by the presence of impurities. The size enlargement in presence of sulfate ion was ascribed to an increase in aggregation rate. It was demonstrated that the role of the impurities studied upon KCl crystallization is consistent and predictable and is a function of the chemical character of the impurity species. Based on these results two mechanisms for size enlargement were identified, first due to crystal growth by solid deposition and second due to aggregation. Aggregation was found to be the governing mechanism for producing large crystals.
Mechanical behaviour of highly filled lignin/polyethylene composites made by catalytic grafting
Authors: Casenave S. , Aït‐Kadi A. , Riedl B. 
Published: March 2009

AbstractHighly filled lignin/polyethylene composites, with enhanced mechanical properties, were studied. Composites are prepared using the catalytic grafting technique of polyethylene on lignin particles. This technique improves wetting and dispersion of additives in the matrix as well as interactions between these two components. Mechanical properties (tensile and impact) and morphology of the composites were measured. The experimental results showed that highly filled HDPE/lignin composites (up to 73 vol%) could be produced by catalytic grafting. Tensile properties of the composites were quantitatively analysed using a micromechanical model for particulate composites based on an energy balance. Model predictions for Young's modulus are in excellent agreement with experimental results. The adjustable parameters of the model were varied from one composite to the other in a way which corresponds to the basic concepts related to particulate composites in general and to catalytic grafting in particular.
Modeling of approach processes for equal or unequal sized fluid particles
Authors: Svendsen Hallvard F. , Luo Hean 
Published: March 2009

AbstractThe approach of two unequal or equal sized fluid particles is modeled using a simple parallel film model, giving expressions for interaction time and maximum film area, disregarding all external forces. The interaction time is found independent of the initial approach velocity and it explains why the effective virtual mass coefficient changes with the radius ratio of particles in the model of Chesters and Hofman (1982). A more general parallel film model is also developed based on the balance of forces acting on the particles and shows how initial velocity, radius ratio and buoyancy affect the interaction time, approach velocity and film area. Both models are compared to the experimental data of Scheele and Leng (1971).
Electrooxidation of Diacetone ‐L‐Sorbose (DAS) into Diacetone‐2‐Keto‐L‐Gulonic acid (DAG) at nickel electrodes
Authors: Lyazidi H. Ait , Benabdallah M. Z. , Berlan J. , Kot C. , Fabre P.‐L. , Mestre M. , Fauvarque J.‐F. 
Published: March 2009

AbstractThe oxidation of diacetone‐L‐sorbose (DAS) into diacetone‐2‐keto‐L‐gulonic acid (DAG) is a step in the synthesis of vitamin C. This oxidation was carried out electrochemically in a stirred cell with the redox couple Ni (OH)2/β‐NiOOH as an electrochemical mediator. The anode was made of a current collector (nickel foam or platinized‐titanium) and of a suspension of Ni(OH)2 in KOH aqueous media. The mediated electrooxidation of DAS was achieved by the Ni(OH)2β‐NiOOH couple in solution which was regenerated at the current collector. This process required a two‐compartment reactor but afforded high yields of chemical conversion: we obtained 96% with a 48% faradaic yield. Previous works dealing with DAS electrooxidation to DAG on nickel anode are reviewed hereafter.
Mass transfer behaviour of a fixed bed electrochemical reactor with a gas evolving upstream counter electrode
Authors: Sedahmed G. H. 
Published: March 2009

AbstractMass transfer rates were determined at a horizontal screen cathode stirred by oxygen bubbles evolved at a horizontal anode placed below the screen by measuring the limiting current of the cathodic reduction of ferricyanide ion from alkaline solution. Variables studied were oxygen discharge rate, ferricyanide concentration and number of closely packed screens forming the cathode. For a single screen cathode the data were correlated by the equation:J = 0.249 (Re Fr)‐0.25The mass transfer coefficient was found to decrease with increasing the number of screens forming the cathode. Implications of the present work for improving the performance of the flow‐through packed bed electrochemical reactor were highlighted.
Simulation and optimization of cellulose and styrene graft copolymerization process
Authors: Bataille P. , Statioukha G. , Statioukha O. 
Published: March 2009

AbstractGraft polymerization of styrene into cellulose was investigated using Ceric ions redox systems as initiator. A mathematical model with the D‐optimal design combined with the least squares method was applied to the system. The variables considered in the model are the reactant variables i.e. monomer and initiator concentrations and the processing variables i.e. reaction time, temperature and agitation rate. The optimal composition and processing conditions were determined using a three dimensional space analysis.
A predictive neural network model based on the karhunen‐loéave expansion for wall‐cooled fixed‐bed reactors
Authors: Zhou Xing‐Gui , Liu Liang‐Hong , Yuan Wei‐Kang , Hudson J. L. 
Published: March 2009

AbstractExperiments were carried out with a pilot scale, wall cooled, fixed‐bed reactor for benzen oxidation. The inlet concentration of benzene was varied in three ways: periodically, with PRBS, and by means of a step change. A model for the reactor is developed with use of the Karhunen‐Loéve (K‐L) expansion and neural networks. The K‐L expansion procedure used here acts as a preprocessor to achieve good data compression while preserving as much information about the measurements as possible. A recurrent multilayer feedforward network is then used to relate the coefficients of the K‐L expansion to the operating conditions. The model developed is used for on‐line prediction of the axial temperatures in a fixed‐bed reactor and results show that the predictions are in good agreement with measurements.
Control of a nonadiabatic packed bed reactor under periodic flow reversal
Authors: Budman Hector , Kzyonsek Mark , Silveston Peter 
Published: March 2009

AbstractA full parametric study of the open‐loop behavior of a packed bed reactor‐recuperator system operating under periodic flow reversal produced a series of parametric maps which slow regions of operating conditions for which the system exhibits runaway, stable operation or extinction of the reaction. The reaction is CO oxidation over a Pt/alumina catalyst. A set of optimal operating conditions in terms of cycle time and heat transfer coefficient can be directly extracted from the parametric maps.A preliminary study on the control of periodic flow reversal tested and compared two strategies. 1) feedback PID control of the exit CO concentration and 2) model based feedforward control.
Bleach activation of thermomechanical pulp
Authors: Sain M. M. , Daneault C. , Parenteau M. 
Published: March 2009

AbstractUnder mild alkaline condition the bleaching activator tetraacetyl ethylenediamine (TAED) forms peroxyacetic acid with sodium perborate and improves the brightness of thermomechanical pulp. The activator makes it possible to bleach the pulp efficiently even without addition of sodium hydroxide at any temperature in the range 40 to 70°C. A mathematical model has been proposed to allow estimation of the total peroxy acid consumption during activated bleaching process. Using this model it is possible to calculate the extent of peroxy acid decomposition by predetermining the rate constant and activation energy. The effect of bleach activation was found to be maximum at temperatures below 60°C. The influences of bleaching time, pH, consistency, temperature and TAED charge on the bleach activation has been evaluated. The activator is effective enough to improve the brightness of sodium perborate bleached pulp at an average charge of about 50 mass% of sodium perborate. Apparently, high consistency dispersive bleaching without free alkali is a technological and economic advantage of the process.
Étude comparative de flux et de performances lors du traitement d'effluent papetiers par bioréacteur à membranes
Authors: Dufresne Robert , Lebrun R. E. , Lavallée H. C. 
Published: March 2009

AbstractLe but de cette étude est d'évaluer le rôle des membranes à l'intérieur des bioréacteurs à membranes (BRM) et de mod‐éliser les flux. Deux modèles, développés pour les bioréacteurs à membranes externes, ont permis de quantifier l'importance de la concentration des solides en suspension de la liqueur mixte. L'effet des rétrolavages est également quantifié. Une comparaison des performances de BRM équipés de membranes avec des seuils de coupure différents, a permis de démontrer l'importance prédominante de la couche de boues (à la surface et à l'intérieur des pores des membranes) par rapport au seuil de coupure.
A new method to determine the composition of biomass by thermogravimetric analysis
Authors: Cozzani Valerio , Lucchesi Aldo , Stoppato Giusto , Maschio Giuseppe 
Published: March 2009

AbstractA method for the direct determination of the cellulose and lignin content of biomass has been developed. The method assumes that negligible interactions exist between biomass macrocomponents and it is based on the analysis of thermogravimetric (TG) pyrolysis data. The TG‐weighed sum method seems to be reliable and less time consuming than conventional methods for the determination of the cellulose and lignin content. Some limitations of the macrocomponent approach in the description of biomass pyrolysis are also discussed. In particular, hemicellulose pyrolysis data are analyzed. The use of xylans as substitute materials for hemicellulose have been critically examined. The results obtained point out that the widely practiced use of xylans as substitute compounds for the simplified description of hemicellulose pyrolysis can lead to significant errors.
Performance assessment of multivariate control loops on a paper‐machine headbox
Authors: Huang Biao , Shah Sirish L. , Kwok K. Ezra , Zurcher Jim 
Published: March 2009

AbstractA large number of control loops in the pulp and paper industry are multivariate in nature. The main control objective of these loops is to reduce process variation. The satisfactory performance of these loops is therefore important for maintaining product quality. This paper introduces a multivariate performance measure of such control loops. The multivariate minimum variance control performance which provides an absolute lower bound on process variance can be estimated from routine operating data, and serves as a good benchmark to assess control loop performance. The proposed measure of performance is evaluated by application to the multiloop control of a headbox machine.
Etude de l'oxydation du pentachlorophénol dans différentes géométries de réacteurs à ultrasons de haute fréquence
Authors: Gonze E. , Gonthier Y. , Boldo P. , Bernis A. 
Published: March 2009

AbstractNous avons entrepris de déterminer les paramétres géometriques fondamentaux intervenant dans la modélisation d'un réacteur à ultrasons de haute fréquence. Une méthodologie permettant de caractériser les différents réacteurs réalisés au laboratoire a été mise au point. Elle comprend: la mesure de la calorimétrie, la détermination de la distribution des temps de séjour, I'observation de la chimiluminescence du luminol et le suivi de la dégradation de solutions de penta‐chlorophénol. A I'issue de la caracténsation des réacteurs étudiés, il semble que la puissance volumique, à systéme émet‐teur équivalent, soit le paramétre qui conditionne le fonctionnement du réacteur.
Prediction of optimum operating conditions of liquid fluidized bed systems
Authors: Jamialahmadi M. , Malayeri M. R. , Müller‐Steinhagen H. 
Published: March 2009

AbstractAn important advantage of fluidized beds applied in various chemical and physical operations is the high rate of heat transfer between the bed and the heat transfer surfaces. However, the design of these systems for optimum conditions remains uncertain and essentially empirical. In this study a model for bed voidage and a model for heat transfer are presented which can be used to predict the maximum attainable heat transfer coefficient and the corresponding bed voidage of liquid fluidized bed systems with good accuracy.
Study of humic acid adsorption on nanofiltration membranes by contact angle measurements
Authors: Bouchard C. R. , Jolicoeur J. , Kouadio P. , Britten M. 
Published: March 2009

AbstractMembrane fouling is a major problem, which extent depends on the respective natures of the solute and membrane material. Membrane surface characterization under different fouling conditions may help in understanding the fouling mechanism. Such characterization was performed for the case of humic substances filtered on two nanofiltration membranes, using special contact angles measurements. The measured contact angles allowed the calculation of polar and non‐polar contributions to the surface energy of dry, hydrated and fouled membranes. The results reveal significant differences in the two membrane behaviours and information about the way that fouling material may be adsorbed on membrane surface.
Modeling of multi gas—solid reactions: A transient model
Authors: Abba I. A. , Hastaoglu M. A. 
Published: March 2009

AbstractA rigorous multicomponent multi gas‐solid reaction model is developed. It is based on the particle — pellet model and considers the transient nature of the system, inter‐ and intra‐particle heat and mass transfer and the variation of structural parameters with reaction. The model equations describing the structural changes along with property evaluation schemes are formulated for a general multicomponent system. Simulation results are compared with experimental data for carbon gasification and the reduction of a nickel oxide/hematite mixture. The match between model and experiment was found satisfactory. Both concentration and temperature profiles and other parameters are examined.
Optimal control of final state constrained systems
Authors: Mekarapiruk Wichaya , Luus Rein 
Published: March 2009

AbstractIn using penalty functions to handle final state equality constraints, we propose a systematic scheme for adjusting the penalty function factors, so that all the constraints are satisfied within a specified tolerance, and so that the performance index is minimized. Two typical engineering problems, which are used to test the procedure, show that the proposed method of adjusting the penalty function factors can be used for reasonably complex systems to yield reliable results.
Effect of catalyst loading on gasliquid mass transfer in a slurry reactor: A statistical experimental approach
Authors: Inga Juan R. , Morsi Badie I. 
Published: March 2009

AbstractA statistical experimental design was employed to study the effects of pressure, temperature, catalyst loading, and mixing speed on the solubilities (C*) and volumetric gas/liquid mass transfer coefficients (kLa) for H2, N2, CO, CH4 and C2H4 in a liquid mixture of hexanes containing iron oxide catalyst in a 4‐litre agitated autoclave. Statistical correlations for kLa values for the gases used were developed. Mixing speed and solid concentration showed the strongest effects on kLa. At low catalyst concentrations, a maximum in kLa was observed and at concentrations > 37 mass%, kLa decreased by more than one order of magnitude.