bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissolution equilibria and kinetics of fluorite and calcite mixtures
Authors: Qi Jian , Knaebel Kent S. 
Published: June 2004

AbstractMinerals commonly contain impurities, and their dissolution involves complicated ionic equilibria and multicomponent mass transfer. This paper describes the experiments that were carried out and proposes a mechanism for dissolution behavior of fluorspar containing calcite as a major impurity in both batchwise and continuous packed‐bed systems.The mechanism is based on analysis of coupled equilibria among the soluble species. Of more than eight potentially relevant species, only three (viz., F−, HCO3−, and Ca2+) are significant. The coupled flux equations for F− and HCO3− are written in terms of “main” and “cross” mass transfer coefficients, with the concentration of ca2+ being accounted for by electroneutrality. Only one main mass transfer coefficient needs to be determined experimentally; and other coefficients can be evaluated from it by means of simple diffusion coefficient ratios, which are determined independently. The Stanton number based on the main mass transfer coefficient is correlated with Reynolds number and the Schmidt number for packed bed dissolution.
Solid flow in the annular region of a spouted bed
Authors: Benkrid Abdelhakim , Caram Hugo S. 
Published: June 2004

AbstractThe solid circulation in the annular region of a 0.146 and a 0.292 m ID semicylindrical and cylindrical air spouted beds was investigated for different spouting conditions. Stroboscopic photography, stopwatch and fiber optic methods were used to measure the vertical particle velocities in the annular region. The optical fiber probe enabled the measurement of particle velocities inside the dense annular phase and was validated at the walls. Velocity profiles in half beds were very different from those found in full beds. The work was then limited to full beds. Experimental results show that the solids flow is characterized by a point sink at the nozzle entrance with the solids moving almost in plug flow higher in the bed. There is negligible entrainment of solids along the spout wall and slow, thin wall layers are observed near the walls and spout. The velocity profiles are independent of the total height of the bed. A kinematic model successfully describes the observed velocity field.
Melt transesterification of dimethyl terephthalate with ethylene glycol
Authors: Besnoin J.‐M. , Lei G. D. , Choi K. Y. 
Published: June 2004

AbstractThe kinetics of a semibatch melt transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) is studied with zinc acetate as a catalyst. This paper quantifies the effect of various reactor operating conditions on the transesterification rate and the product composition distribution. Our experiments support the assumption that the methylesters in DMT and growing oligomer chains have the same reactivities for transesterification with EG and that the reactivity of hydroxyl groups in pure EG for esterification with DMT is twice that of the hydroxyl group in oligomers. With a molecular species model in which various oligomers are identified by the type of functional end groups, the progress of the transesterification and the oligomer concentration distribution were estimated and the agreement between the model predictions and the experimental data were excellent. It has also been shown that 30 wt. % of oligomers are produced for [EG]/[DMT] molar ratio of three, and up to 70 wt. % oligomers are produced at the [EG]/[DMT] molar ratio of one.
Observation of a dynamic wetting process using Laser‐Doppler velocimetry
Authors: Mues W. , Hens J. , Boiy L. 
Published: June 2004

AbstractThe purpose of this study is to observe the dynamic wetting process of a slide coater flow (Ca = 0.16; Re = 14.4; St = 0.0142; ΔeP = 2.5), using a specially‐developed Laser‐Doppler measuring technique.The measurements, carried out with glycerol solutions, reveal that the observed contact line is apparent and that a thin air film is entrained between the web and the liquid surface. The liquid is accelerated along the lower free surface and attains approximately 50% of the web velocity at the apparent contact line. Downstream from the apparent contact line, the liquid is further accelerated along the air film to the web velocity at the real contact line.The apparent contact angle increases with the capillary number Ca and air entrainment occurs at Ca = 0.25.
Improved oxygen mass transfer modeling for diffused/subsurface aeration systems
Authors: McWhirter John R. , Hutter Joseph C. 
Published: June 2004

AbstractThe mass transfer analysis of the oxygen transfer performance of diffused air or subsurface mechanical aeration systems has progressed very little over the past 20 years. The recently‐developed ASCE Standard method for determination of the oxygen mass transfer performance of diffused or subsurface aeration systems is based on a greatly over‐simplified mass transfer model. Although the ASCE Standard can be used to empirically evaluate point performance conditions, it does not provide a meaningful representation of the actual mass transfer process and is not capable of accurately assessing or predicting performance under changing operating or environmental conditions. A new oxygen mass transfer model has been developed which is a fundamentally more rigorous description of the actual mass transfer process in diffused aeration systems. This model can be confidently used to predict aerator performance under changing operating and environmental conditions. The model is easily adapted to numerical computer solution for routine aeration systems performance evaluation as well as process design.
Ultrapyrolysis of propane in a spouted‐bed reactor with a draft tube
Authors: Stocker Rudolf K. , Eng John H. , Svrcek William Y. , Behie Leo A. 
Published: June 2004

AbstractUltrapyrolysis or ultrarapid pyrolysis is a hydrocarbon thermal cracking process which offers the promise of greater product selectivity, higher yield and feedstock flexibility. In this paper, ultrapyrolysis of propane in a spouted bed with a draft tube was used as a test system to demonstrate these advantages. Experiments, carried out on a 20‐cm‐diameter pilot‐scale reactor, illustrate the spouted bed to be capable of achieving the extremely high reactant heating rates of up to 105 K/s and the short gas residence times of less than 500 ms necessary for this process. Moreover, reactant conversion and product yields can be enhanced by controlling the operating temperature of the bed. In addition, application of the propane pryolysis reaction scheme of Sundaram and Froment into a recently developed computer model indicates the ability to correctly simulate the spouted bed as an ultrapyrolysis reactor.
Hindered transport of spherical macromolecules in fibrous membranes and gels
Authors: Phillips R. J. , Deen W. M. , Brady J. F. 
Published: June 2004

AbstractMethods are described for calculating the effects of hydrodynamic interactions on the hindered transport of solid spherical macromolecules in ordered or disordered fibrous media. These methods are applied to a medium made up of a square lattice of straight, bead‐and‐string‐type fibers. Hydraulic permeabilities and coefficients governing hindered diffusion and convection are obtained from a detailed hydrodynamic model, and the hindered transport coefficients are shown to be in very good agreement with an effective medium approach based on Brinkman's equation. The use of Brinkman's equation for the calculation of hindered transport rates in fibrous membranes and gels is validated further by comparing with experimental data from the literature.
The effect of pore structure on the char‐steam reaction
Authors: Chi Wei‐Kuang , Perlmutter Daniel D. 
Published: June 2004

AbstractThe kinetics of the char‐steam gasification reaction and the accompanying pore structure changes have been investigated experimentally and interpreted through the use of the random pore model of Bhatia and Perlmutter (1980) and its extensions developed in this study. To allow model evaluations, surface areas and pore‐size distributions were obtained for various partially‐reacted char samples. Surface areas follow the reaction rates as a function of conversion, supporting the interpretation that the reaction of porous char with steam is governed by the structural changes that occur as conversion proceeds. Reaction rate constants were obtained from the kinetic data.A pyrolytic change of char mass was observed during the heatup period from room temperature to reaction temperature for each of the two char samples tested. This results in a significant increase in surface area and a decrease in pore structure parameter. It is shown that this pore structure parameter is very sensitive to changes in conversion when the initial parameter is large and the conversion is small.
Incipient fault diagnosis of chemical processes via artificial neural networks
Authors: Watanabe Kajiro , Matsuura Ichiro , Abe Masahiro , Kubota Makoto , Himmelblau D. M. 
Published: June 2004

AbstractArtificial neural networks have capacity to learn and store information about process faults via associative memory, and thus have an associative diagnostic ability with respect to faults that occur in a process. Knowledge of the faults to be learned by the network evolves from sets of data, namely values of steady‐state process variables collected under normal operating condition and those collected under faulty conditions, together with information about the degree of the faults and their causes.Here, we describe how to apply artificial neural networks to fault diagnosis. A suitable two‐stage multilayer neural network is proposed as the network to be used for diagnosis. The first stage of the network discriminates between the causes of faults when fed the noisy process measurements. Once the fault is identified, the second stage of the network estimates the degree of the fault. Thus, the diagnosis of incipient faults becomes possible.
Axial dispersion in pulsed‐, perforated‐plate extraction columns
Authors: Prvcic Leanne M. , Pratt H. R. Clive , Stevens Geoffrey W. 
Published: June 2004

AbstractContinuous‐phase backmixing coefficients have been determined by continuous tracer injection for pulsed‐plate extraction columns of 72‐, 152‐ and 300‐mm‐diameter. Both single‐phase water and two‐phase kerosene‐water were studied in all three columns, together with four other solvent‐water systems in the smallest column; in all cases, water was the continuous phase. Evidence of maldistribution of the phases was obtained in the largest column. The backmixing coefficient was found to increase with column diameter in single‐phase operation, but was diameter‐independent in the two‐phase case. Alternative correlations of the data were based on dimensional analysis and on a physical model, respectively. The influence of different systems was accounted for in the latter in terms of droplet size and terminal velocity, dispersed phase holdup, and density difference. Qualitative color tracer tests on the dispersed phase gave no evidence of backmixing of this phase, although strong forward dispersion was observed in the emulsion regime.
Robust isolable models for failure diagnosis
Authors: Gertler Janos , Luo Qiang 
Published: June 2004

AbstractThe paper presents a design procedure to generate parity equation models for analytical failure detection and isolation. The models are in “statistically‐isolable” structure that prevents incorrect isolation decisions under marginal failure size if the residuals are tested in parallel. Of the combinatorial multitude of structurally‐suitable models, a choice is made on the basis of sensitivities with respect to different failures and robustness relative to uncertainties in selected parameters of an underlying model. A complete set of parity equations fitting the isolable structure is first generated from a state‐space model. The equations unsuitable for sensitivity are eliminated, and a suboptimally‐robust diagnostic model is obtained in a constrained discrete search over the remaining set.
Partitioning of spherical solutes into sponge‐type materials
Authors: Fanti Lisa A. , Glandt Eduardo D. 
Published: June 2004

AbstractPartition coefficients are computed for hard spherical solutes in equilibrium with sponge‐type matrices containing randomly‐placed spherical cavities or pores using grand canonical Monte Carlo simulation. The random pore model is representative of a variety of disordered porous solids including porous glasses and some polymeric materials. The algorithm used brings additional realism to the problem by rigorously distinguishing between accessible and inaccessible pore space. The simulation results display significant concentration effects which are often observed experimentally and are compared to data obtained by Brannon and Anderson (1982) for the partitioning of bovine serum albumin into controlled‐pore glass.
Turbulence‐producing eddies in the viscous wall region
Authors: Lyons S. L. , Hanratty T. J. , McLaughlin J. B. 
Published: June 2004

AbstractA computer simulation of turbulent flow in a channel is used to detect flow patterns related to the production of Reynolds stress. It is found that quadrant 2 and quadrant 4 events possess a streaky structure in the viscous wall region and that these events can be best understood by examining the velocity field in the y‐z plane. Large turbulence production in the viscous wall region is found to occur in updrafts and downdrafts associated with closed eddies. These eddies, on average, have a spanwise dimension of 50 wall units and a streamwise dimension of 400–450 wall units. They are often seen to originate from small attached eddies at the wall.
A neural network methodology for process fault diagnosis
Authors: Venkatasubramanian Venkat , Chan King 
Published: June 2004

AbstractThe ability of knowledge‐based expert systems to facilitate the automation of difficult problems in process engineering that require symbolic reasoning and an efficient manipulation of diverse knowledge has generated considerable interest recently. Rapid deployment of these systems, however, has been difficult because of the tedious nature of knowledge acquisition, the inability of the system to learn or dynamically improve its performance, and the unpredictability of the system outside its domain of expertise.This paper proposes a neural‐network‐based methodology for providing a potential solution to the preceding problems in the area of process fault diagnosis. The potential of this approach is demonstrated with the aid of an oil refinery case study of the fluidized catalytic cracking process. The neural‐network‐based system successfully diagnoses the faults it is trained upon. It is able to generalize its knowledge to successfully diagnose novel fault combinations it is not explicitly trained upon. Furthermore, the network can also handle incomplete and uncertain data. In addition, this approach is compared with the knowledge‐based approach.
Mass transfer with chemical reaction in a threehyphen;phase foam‐slurry reactor
Authors: Stangle Gregory C. , Mahalingam R. 
Published: June 2004

AbstractStudies on mass transfer coupled with chemical reaction were conducted in a gas‐liquid‐solid foam bed contactor under a variety of operating conditions in order to establish the controlling parameters for such a contacting system. Analytical equations were derived in order to predict the influence of solids dissolution on the specific rate of absorption in the stable foam stage of a three‐phase foam‐slurry reactor. Experimental investigations on the absorption of carbon dioxide in the presence of an aqueous foam‐slurry containing calcium hydroxide particles were carried out in order to verify the theoretical model. Results indicate that the gas‐liquid interfacial area and gas flow rate strongly affected the rate of mass transfer, while solids holdup affected mass transfer rates only moderately over the range of solids holdup studied. A comparison with conventional chemical reactor configurations (e.g., bubble column, CSTR) was made to demonstrate the gas‐liquid‐solid system, for which this novel reactor might be employed. Foam stability enhancement, due to the presence of solid particles, was not observed.
Extensional flow of a two‐phase fiber
Authors: Park Chang‐Won 
Published: June 2004

AbstractA steady, isothermal flow of a two‐phase fiber spinning has been studied. To investigate the spinline velocity profile affected by the interaction between two fluids with different rheological properties, a Newtonian and an upper‐convected Maxwell fluid were considered to be the core and skin layers, respectively. Unlike the one‐dimensional analysis, which has been the typical approach for spinning flows, radial dependency of the flow field was maintained in our analysis. Consequently, a set of partial differential equations were derived for the flow field in the draw‐down region where lubrication scalings are applicable. Asymptotic solutions were then obtained for two limiting cases, where the Deborah number of the skin layer is small and the applied axial tension is large. When the Deborah number of the skin layer is small, a velocity correction to the Newtonian profile indicates a strong effect of the flow rate ratio as well as the shear viscosity ratio of the two fluids. For the case of a large applied tension, which is more relevant to industrial practice, very interesting flow behaviors are predicted. In this limit, the viscoelasticity effect of the skin layer is shown to be dominant and dictates the mechanics of the flow even when both its flow rate and shear viscosity may be much smaller than those of the Newtonian core layer. The result also predicts that hoop stress has a negligible effect on the axial velocity profile.
A dynamic model for the interaction of caustic reagents with acidic oils
Authors: Chiwetelu Chris I. , Hornof Vladimir , Neale Graham H. 
Published: June 2004

AbstractThis paper describes the mechanisms and a quantative analysis of the interaction between a multicomponent acid mixture with a spectrum of caustic solutions. A physico‐chemical model of the acidic oil/caustic system has been proposed which demonstrates the effect on dynamic interfacial tension (IFT) of variations in caustic concentration as well as changes in the initial composition and ionization properties of the constituent acids of the oleic phase. The model relies on the Langmuirian theory of interfacial sorption kinetics in addition to the Nernstian theory of convective diffusion. Pertinent kinetic and mass transfer parameters for all contributing surface‐active species were determined from a recently proposed single‐component dynamic model (Chiwetelu et al., 1988a). The validity of this multicomponent dynamic model was confirmed by the close agreement between predicted IFT and experimental data for a binary carboxylic acid system in contact with a broad range of caustic concentrations.
Shear thickening (dilatancy) in concentrated dispersions
Authors: Boersma Willem H. , Laven Jozua , Stein Hans N. 
Published: June 2004

AbstractA new criterion is introduced for the onset of shear thickening in a concentrated dispersion. The criterion follows from the assumption that shear thickening occurs when the shear forces overrule the interparticle forces. A force balance at small interparticle distances is used to predict the dependence of this critical shear rate on the volume fraction. It is deduced that the critical shear rate is proportional to the interparticle distance, has a linear dependence on the magnitude of the stabilizing force, an inverse linear dependence on the dispersion medium viscosity, and an inverse linear dependence on the particle radius. The model is confirmed experimentally with viscosity measurements on various electrostatically stabilized dispersions. The validity of the model is also checked with data obtained from the literature. Experiments indicate that polydisperse dispersions exhibit pronounced shear thickening but with a less dramatic increase in viscosity than monodisperse dispersions.
Solubility models for amino acids and antibiotics
Authors: Gupta Ram B. , Heidemann Robert A. 
Published: June 2004

AbstractAn approach is presented for modeling the effects of temperature and pH on the solubility of amino acids in water. The amino acids studied are alanine, amino‐butyric acid, glycine, hydroxy‐proline, proline, serine, threonine, and valine. The data employed are activity coefficients and solubilities of the amino acids in neutral water and the dissociation constants for the various amino‐acid ionization reactions. Activity coefficients are correlated with the modified UNIFAC group contribution model and with new glycine and proline groups being introduced.A similar approach is presented for modeling the solubilities of certain antibiotics in mixed nonaqueous solvents. Fusion temperature data and solubilities of the antibiotics in pure organic solvents are used to deduce modified UNIFAC energy interaction parameters between new large antibiotic groups and the standard alkane (CH2), alcohol (OH), aromat (ACH), and ester (CCOO) groups.
Analysis of autocatalytic reactions in isothermal catalyst particles
Authors: Hu R. , Sapre A. V. 
Published: June 2004

AbstractMultiplicity features of autocatalytic reactions in isothermal catalyst particles with diffusion interaction are presented. Discussed also are two types of autocatalytic reactions—A + B → 2B (quadratic) and A + 2B → 3B (cubic)—and a decay reaction for autocatalyst B, B → C, and a nonautocatalytic reaction, A → B, which generates the autocatalyst. For quadratic reactions, the bifurcation diagrams for a catalyst particle are similar to those for a CSTR. The location of the branch solution, however, is somewhat different. For cubic autocatalytic reactions, the exact parameter regions, where the isola, mushroom, reverse‐S, and reverse‐S‐plus‐isola patterns of bifurcation exist, are determined. Furthermore, the parameter space, where a unique solution exists for all Thiele moduli, is also given.
Particle generation in a chemical vapor deposition process with seed particles
Authors: Okuyama Kikuo , Ushio Ryuichi , Kousaka Yasuo , Flagan Richard C. , Seinfeld John H. 
Published: June 2004

AbstractThe formation of aerosol particles by gas‐phase chemical reaction in the presence of seed particles has been studied experimentally and theoretically. Titanium tetraisopropoxide (TTIP) vapor containing ultrafine TiO2 seed particles was introduced into a laminar flow aerosol reactor, and the properties of produced TiO2 aerosol were measured. By comparing the particle numbers and size distributions of the resulting aerosol with those of the seed particles and those of homogeneously nucleated particles in the absence of seed particles, the effects of initial concentrations of TTIP vapor, reaction temperatures, and properties of seed particles on the suppression of homogeneous nucleation were experimentally clarified. In the theoretical analysis, the population balance equation expressing simultaneous generation of TiO2 monomer, Brownian coagulation and diffusive deposition of TiO2 monomer and aerosols was solved. The observed suppression of homogeneous nucleation by the seed particles is explained qualitatively by the theoretical analysis.
Gas‐liquid mass transfer from a single bubble in liquid‐solid fluidized beds
Authors: Song Gyung‐Ho , Fan Liang‐Shih 
Published: June 2004

AbstractExperiments were conducted to study the gas‐liquid mass transfer of a single bubble containing an ozone‐oxygen gas mixture in liquids and liquid‐solid fluidized beds. A spectrophotometric technique is developed for the measurement of the instantaneous mass transfer coefficient and the local concentration distribution around the bubble wake. The method employs an ultraviolet light source and optical fibers. Axial variations of the mass transfer rate are studied. An ozone and starchiodide complex reaction is employed to visualize the mass transfer phenomena.