bluuebunny/crossref_metadata_2025_split huggingface dataset:
Adsorption of ethyl benzene on activated carbon from supercritical CO2
Authors: Harikrishnan R. , Srinivasan M. P. , Ching C. B. 
Published: April 2004

AbstractOur work involves experimental and simulation studies of the adsorption breakthrough and equilibria of ethyl benzene (a pollutant commonly encountered in industrial waste streams) on activated carbon in the presence of supercritical carbon dioxide. Frontal and single breakthrough saturations were analyzed for a range of operating conditions of pressure (100–130 bar) and temperature (313–338 K). The equilibrium data correlated well with the Langmuir isotherm. The adsorption process was successfully modeled by a three‐parameter model with comparable fitting parameters for the two types of breakthrough curves.
Standing wave design of nonlinear SMB systems for fructose purification
Authors: Mallmann T. , Burris B. D. , Ma Z. , Wang N. H. L. 
Published: April 2004

AbstractDesign equations were derived from standing wave analysis for continuous moving bed (CMB) and simulated moving bed (SMB) systems with nonlinear isotherms. Simple wave solutions and hodograph plots from batch elution experiments can be used to derive the optimal operation conditions for SMB systems without mass‐transfer effects. The design equations are tested with results from computer simulations and experimental data from two pilot‐scale SMB units for the separation of fructose from glucose. Batch equilibrium tests of single component and binary solutions are used to estimate adsorption isotherm parameters. Overall mass‐transfer and axial dispersion coefficients are estimated from eight sets of pulse, frontal and elution data at different concentrations and flow rates. The isotherm and mass‐transfer parameters are used in the standing wave analysis to determine the zone flow rates and switching times for the two SMB units. Experimental column profiles, product purities, and product concentrations agree closely with simulation results. This method gives robust operation conditions for SMB systems with nonlinear isotherms, and optimal cycle time and zone flow rates for nonlinear systems without mass‐transfer effects can be determined from the standing wave analysis.
Leak detection in liquefied gas pipelines by artificial neural networks
Authors: Belsito Salvatore , Lombardi Paolo , Andreussi Paolo , Banerjee Sanjoy 
Published: April 2004

AbstractA leak detection system for pipelines was developed by using artificial neural networks (ANN) for leak sizing and location and by processing the field data. This system can detect and locate leaks down to 1% of flow rates in pipelines carrying hazardous materials in about 100 s. A reference pipeline was considered for practical implementation of the package. The ability of the package to withstand spurious alarms in the event of operational transients was tested. The compressibility effect, due to “packing” of the liquid in the pipeline, causes many such spurious alarms. Adequate preprocessing of the data was performed by using a computer code in conjunction with the ANN to compensate for the operational variations and to prevent spurious alarms. The package detects leaks as small as 1% of the inlet flow rate and correctly predicts the leaking segment of pipeline with a probability of success that is greater than 50% for the smallest leak. In all cases, the timely response of the system was seen as a major advantage.
Direct sonication system suitable for medium‐scale sonochemical reactors
Authors: Dahlem Olivier , Demaiffe Vincent , Halloin Véronique , Reisse Jacques 
Published: April 2004

AbstractA radially vibrating horn is studied as a possible system for scaling up sonochemical reactors. The anisotropic behavior of this horn was demonstrated, as were strong correlations among the acoustic field, the acoustic streaming, and the sonochemical reactivity. A comparison with the classic laboratory horn exhibits the benefits of the larger emitting surface of the radially vibrating horn for homogeneous reactions, but not for polymer degradation reactions or for heterogeneous liquid–liquid reactions. The experimental techniques used proved to be very useful in characterizing the sonochemical reactors.
Filtration of liquid aerosols on wettable fibrous filters
Authors: Agranovski Igor E. , Braddock Roger D. 
Published: April 2004

AbstractLiquid aerosols produced in many manufacturing and refining processes need to be filtered from the exhaust streams. Where wettable fibers are used in the filters, the aerosol liquid collects on the fibers. Observation shows that thin films develop on the fibers, and the liquid drains down the fibers under the action of gravity. A model is developed for the flow of liquid in these films, and careful experimentation confirms the nature and importance of the flow pattern. The resultant overall efficiencies of the filter are also calculated from a theoretical analysis and compared with the results of experimentation using counting techniques. The theoretical and experimental results agree excellently for the range of aerosol sizes that are detectable by laser diffraction and cascade impactor techniques.
Filtration of liquid aerosols on nonwettable fibrous filters
Authors: Agranovski Igor E. , Braddock Roger D. 
Published: April 2004

AbstractChemical, manufacturing and refining processes often generate toxic liquid by products that are emitted as liquid aerosols in the waste stream. Wettable and nonwettable fibers can be used to filter these exhaust streams. The behavior of liquid aerosols and droplets on nonwettable fibers is studied by observation, measurement, and theory. Droplets form on the fibers, grow by accretion from the aerosol, oscillate, and then fall under the action of gravity. Observation and theory indicate that these developing droplets influence air and aerosol flow strongly in the filter. These droplets are akin to the dendritic structures formed by solid aerosol particles within filters, but the shapes are modified by surface tension. The total efficiency of the filter is influenced by these droplets, and the total filter efficiencies are estimated using theoretical methods. The results from both approaches agree excellently in the particle‐size range as measured using particle‐counting techniques.
2‐D Solution for drying with internal vaporization of anisotropic media
Authors: Perré Patrick , Turner Ian W. , Passard Joë 
Published: April 2004

AbstractA set of physical assumptions for a straighfforward and eficient simulation of the dying of a porous medium submitted to a conuective and/or radiative heating is proposed. All of the parameters used are physical (liquid migration coefficient, peimeability values along the thickness and the length, thermal conductive, and external exchanges), but the relevant geometrical properties (length and thickness of the slab) were also included in the analysis. The 2‐D pressure field generated within the medium during the dying process is obtained by using an analytical expression. The treatment of the pressure field, especially for a strongly anisotropic medium, is an important feature of the model, which allows an analytical model for such a complicated porous medium as wood to be used across a wide range of dying conditions. The computer code developed from the proposed formulation permits a complete simulation of the drying process within a few seconds on a personal computer. Different configurations have been tested for both anisotropic (wood) and isotropic (light concrete) porous media. Agreement with the experimental results is reasonable in terms of the obserued physical phenomena. For instance, the model highlights dependence of the duration of the first diying rate on both material properties and drying conditions. This new model can be used for a global physical characterization of products by curve fitting and the collated information for the design of dryers.
Modeling shock layers in ion‐exchange displacement chromatography
Authors: Natarajan Venkatesh , Cramer Steven M. 
Published: April 2004

AbstractIn ideal displacement chromatography (systems with infinite mass‐transfer kinetics), various solutes are separated by sharp discontinuities. In real systems, however, the shocks are eroded into shock layers because of the finite rates of mass transfer. The thickness of these shock layers, which can reduce the yields achievable in these systems, depend on the flow rate, particle diameter and the “difficulty” of these separations. The steric mass action formalism of ion‐exchange chromatography was used in concert with a solid film linear driving force model to describe the effects of flow rate, particle diameter, and the degree of difficulty of the separation on ion‐exchange displacement systems. Simple pulse techniques are employed to estimate the thermodynamic and mass‐transfer parameters. The simulations are then compared to experimental results over a range of conditions. The results demonstrate that this relatively simple modeling approach can be employed to describe the behavior of these nonideal displacement systems.
Absorption of NOx gases in aqueous NaOH solutions: Selectivity and optimization
Authors: Pradhan M. P. , Joshi J. B. 
Published: April 2004

AbstractA mathematical model is presented for multicomponent gas absorption with multiple reactions by considering the case of NOx absorption in aqueous solution of NaOH. Procedures are developed for estimating the overall reaction rates and selectivity. The effects of temperature, pressure, and NOx composition are examined. Optimum design strategy is suggested by proper configuration of the oxidation and absorption stages and by appropriate selection of levels of oxidation and absorption. A comparison between the model predictions and the performance of two operating plants is presented.
Modeling, analysis and control of ethylene glycol reactive distillation column
Authors: Kumar Aditya , Daoutidis Prodromos 
Published: April 2004

AbstractThe dynamic behavior and control of an ethylene glycol reactive distillation column were studied. A detailed tray‐by‐tray model that explicitly includes the vapor‐phase balances is derived and compared with a conventional model that ignores the vapor holdup. The steady‐state variation of the product purity (the key output to be controlled) with respect to reboiler heat duty was studied, identifying a region of output multiplicity with three branches corresponding to different conversion and product selectivity. Further analysis of the process on the steady‐state branch with high conversion and selectivity reveals a transition from minimum phase behavior at moderate purity to nonminimum phase behavior at high purity. The nonminimum phase behavior was analyzed and addressed in the design of a nonlinear inversion‐based controller that performs well with stability in the high purity region.
Design of reactive crystallization systems incorporating kinetics and mass‐transfer effects
Authors: Kelkar Vaibhav V. , Ng Ka M. 
Published: April 2004

AbstractA coherent approach for the design of reactive crystallization systems is presented by incorporating reaction and crystallization kinetics, and mass transfer, into an existing equilibrium‐based conceptual design method. A generic model for a well‐mixed crystallizer is developed; it is applicable to reacting systems with any number of components. The reaction, mass‐transfer and dissolution Damköhler numbers, and the nucleation and growth numbers which result from the generic model, represent the relative rates of the individual steps, and their effect on the resulting crystal‐size distribution and the crystallizer productivity is discussed. Estimates are provided for the typical values of the dimensionless numbers. To describe the solubility behavior of solid‐liquid systems, a generalized equation for the isothermal solubility of a solute in the presence of an arbitrary number of other components is presented. The effects of the dimensionless numbers on the process paths are shown on the phase diagrams for systems involving up to four components. The utility of this integrated approach in the design of reactive crystallization systems is discussed using examples involving single and coprecipitation systems, and a salting out crystallization system.
State observation of a nonlinear system: Application to (bio)chemical processes
Authors: Farza M. , Hammouri H. , Jallut C. , Lieto J. 
Published: April 2004

AbstractThe design of simple nonlinear observer‐based estimators for the on‐line estimation of the reaction rates in chemical and biochemical processes is presented. The proposed estimators do not assume or require any model for the reaction kinetics and are very successful for accurately estimating these variables. They are first presented in a continuous‐time version. Then, the stability and convergence of a discrete‐time version, obtained by a direct forward Euler discretization of these estimators, are established. A main characteristic of these estimators lies in the easiness of their implementation and in particular their calibration. Indeed, their gain does not necessitate the resolution of any dynamical system and is explicitly given. Moreover, its tuning is reduced to the calibration of a single parameter, and this is true regardless of the number of reaction rates to be estimated. The performances of the proposed estimators are highlighted through experimental results dealing with biological and chemical reactions performed in stirred‐tank reactors.
Robust dynamic state estimation of nonlinear plants
Authors: Alvarez Jesús , López Teresa 
Published: April 2004

AbstractAn on‐line state‐estimation design for multiinput multioutput nonlinear plants, either observable or detectable, is presented. The design considers a stage of analysis, in which the solvability of the estimation problem with robust convergence is assessed a priori, and a stage of synthesis, in which the estimator is constructed and its gains are tuned with a systematized procedure. The approach, which stems from a suitable definition of robust nonlinear observability or detectability, provides a methodological framework that identifies the compromise between the performance and the robustness of the estimator and interprets the functioning of the estimator with notions and vocabulary from conventional‐type linear filtering and control techniques. The problem for a class of free‐radical homopolymerization reactors is studied as an application example showing how the proposed design, together with available nonlinear dynamics modeling and characterization methods, can be applied to polymer reactor engineering in particular and to chemical‐process engineering in general.
Lumped kinetic model for catalytic wet oxidation of organic compounds in industrial wastewater
Authors: Zhang Qinglin , Chuang Karl T. 
Published: April 2004

AbstractA simplified reaction pathway was proposed to describe the kinetic behavior of catalytic wet oxidation of organic mixture. The oxidation reactions were divided and lumped into two groups: (1) the deep or complete oxidation reactions with formation of CO2 and H2O; (2) the partial oxidation reactions with formation of all intermediates in aqueous solution of the industrial wastewater. The concentrations of all reactants in wastewater and those of the intermediates formed during the reaction are also represented by a lumped concentration of total organic carbon (TOC). To test the model, catalytic oxidation of organic pollutants in an effluent from a softwood Kraft pulp mill was investigated in a slurry reactor using a Pd‐Pt/Al2O3 catalyst. Sodium hydroxide was used to adjust the initial pH of wastewater to 7.3 to avoid the problem of metal leaching and excessive corrosion. The lumped kinetic model developed in this study describes well both our experimental data and those reported in literature. The lumped kinetic model proposed in this study can be used for both catalytic and noncatalytic wet oxidation processes.
3‐D nonisothermal flow simulation model for injected pultrusion processes
Authors: Mustafa I. , Khomami B. , Kardos J. L. 
Published: April 2004

AbstractInjected pultrusion (IP) is an efficient process for high‐quality, low‐cost, high‐volume manufacturing of polymeric composites with relatively simple cross sections. This process was developed recently, and efforts to develop tools for model‐based design and optimization of this process have only just begun. This work focuses on developing a 3‐D nonisothermal computer simulation model for the IP process. First, the governing equations for transport of mass, momentum, and energy are formulated by using a local volume‐averaging approach. In turn, a computer simulation model of the IP process is developed using the finite‐element/control‐volume (FE/CV) approach. Specifically, the continuity equation and the conservation of momentum equation are solved using a Galerkin FE/CV technique. The chemical species balance equation is solved in the Lagrangian frame of reference, whereas the energy equation is solved using the streamline upwind Petrov‐Galerkin approach. Using the simulation model, the effect of fiber pull speed, reinforcement anisotropy, and taper of the die on the product quality was demonstrated. In addition a simple pulling‐force model was developed and integrated with the simulation model. Overall, the simulation model can be effectively used to design the die geometry and to optimize the operating conditions for a given product.
Growth processes in a cascade of bioreactors: Mathematical models
Authors: Mantzaris Nikolaos V. , Daoutidis Prodromos , Srienc Friedrich , Fredrickson Arnold G. 
Published: April 2004

AbstractMathematical modeling of continuous multiple bioreactors is complicated by two factors. First, the chemical environments differ in different reactors, so biomass receives an environmental shock when it is transferred between reactors. Second, biomass occurs as discrete cells, which of course are and remain segregated from one another, so an element of biomass that enters a reactor does not mix with the biomass already present. This differs from the behavior of an element of liquid which enters a reactor in that such an element quickly mixes with the liquid already present. The biomass in a bioreactor receiving biomass from an external source is therefore heterogeneous with respect to the history of environmental conditions and composition. This article shows how to construct a mathematical model of multiple bioreactor apparatus that accounts for these complications. It also describes simpler models that do not account for both of them.
Growth processes in a cascade of bioreactors: Comparison of modeling approaches
Authors: Mantzaris Nikolaos V. , Daoutidis Prodromos , Srienc Friedrich , Fredrickson Arnold G. 
Published: April 2004

AbstractThe theory of a two‐tank cascade of bioreactors developed by Mantzaris et al. (1998) was used to calculate the performance of such a cascade predicted by two chemically structured models: one for gene expression of Bentley and Kompala (1989) and Bentley et al. (1991) and the other a cybernetic model of Kompala et al. (1986) for multiple substitutable substrates. Two modeling approaches developed previously—one that accounts for biomass segregation and one that does not—were used with the model of Bentley and Kompala (1989) and Bentley et al. (1991). These modeling approaches showed that, in general, biomass segregation is an important feature of what happens in the second tank of the cascade and cannot be neglected. The same two approaches as well as a third approach based on the use of a chemically unstructured model were applied to the model of Kompala et al. (1986). It was found that biomass segregation in the second tank was important under some circumstances but not all and that the unstructured model failed to describe accurately what happens in the second tank under all circumstances.
Simulation of hydrodynamic performance of stirred extraction column
Authors: Steiner Ladislav , Balmelli Marco , Hartland Stanley 
Published: April 2004

AbstractThe hydrodynamic behavior of countercurrent extractors is described by balancing numbers of incoming and outcoming drops against those formed and destroyed by breakage and coalescence. The laws for these processes are still poorly understood, and no reliable experimental data exist. Special empirical equations were, therefore, derived from measurements in a stirred cell. Using a simplified model, a computer program for simulating the variation of the drop‐size distribution along the height of a pilot‐plant sized stirred column solved the equations for all column stages and preselected characteristic drop volumes. A comprehensive set of holdup and drop‐size distribution profiles measured earlier with the same column and o‐xylene dispersed in water has been simulated, with the average mean deviation of local drop‐size distributions not exceeding 20%. Transitional phenomena such as the startup time necessary for obtaining a new steady state after changing the operating parameters and the flooding were successfully predicted.
Capillary transport in adsorption from liquid phase on activated carbon
Authors: Aarden Frans B. , Kerkhof Piet J. A. M. , van der Zanden Antonius J. J. 
Published: April 2004

AbstractTwo models presented here predict the kinetics of adsorption from solution. The adsorbate is considered to form a capillary separated phase inside the micropores. The transport in the adsorbed phase is modeled as capillary transport under the influences of gradients in capillary pressure. In model I the capillary separated phase is assumed to be continuous, while in model II it is assumed to be discontinuous. The effective adsorbed phase diffusion coefficient for this transport is directly related to the pore‐size distribution, which can be found from the sorption isotherm. In both models the overall apparent diffusion coefficients are compared with experimental data. Both models satisfactorily predict the dependency of the diffusion coefficient on carbon loading. Model I slightly underestimates the temperature dependency of the effective diffusion coefficient, while model II gives a good prediction of the influence of temperature on the rate of adsorption.
Model for the interparticle surface separation in concentrated mono‐ and polydisperse suspensions
Authors: Hoffmann A. C. , Kevelam J. 
Published: April 2004

AbstractThe interparticle surface separation in mono‐ and polydisperse concentrated suspensions of spherical particles is discussed. For monosized particles, it is shown that the “expansion” argument of Frankel and Acrivos (1967) can be extended from cubic to arbitrary packing geometries. This argument is then further extended to polydisperse suspensions, resulting in an equation of the same form, but incorporating the surface mean particle diameter for the interparticle surface separation in terms of the packing fraction of the equivalent packed bed (a packed bed with the same packing geometry as the suspension) and that of the suspension. Another approach to interparticle surface separation in suspensions (the “volume of free liquid” argument) confirms the usefulness of the surface mean particle diameter for polydisperse suspensions. A relation potentially useful for suspensions of nonspherical particles is also given.
Dependence of cooled reverse‐flow reactor dynamics on reactor model
Authors: Khinast J. , Jeong Y. O. , Luss D. 
Published: April 2004

AbstractExtensive simulations indicate that in most but not all cases the single‐ and two‐phase models predict similar dynamic behavior of a reverse‐flow reactor, when catalyst pellet multiplicity does not occur at any point in the reactor. Differences in the predictions are found in some cases close to the dynamic bifurcation loci of a cooled RFR, or in others when the qualitative dynamic behavior is very sensitive to the value of the parameters, such as close to a transition to chaotic behavior. The two models can lead to rather different predictions of the dynamic features when there are large differences between the feed and coolant temperatures.