bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unified treatment of structural effects in fluid‐solid reactions
Authors: Bhatia S. K. , Perlmutter D. D. 
Published: June 2004

AbstractBy considering reaction and diffusion through a product layer and concomitant movement of pore and reaction surfaces, a general rate equation is derived for fluid‐solid reactions. Application to the random pore model extends the prior results (Bhatia and Perlmutter, 1980, 1981a) to account for nonlinear concentration gradients in the product layer, by assuming that the product is deposited as overlapping cylindrical annulae. For the Petersen (1957) model, new results are derived which account for product layer diffusion. A comparison of numerical conversion‐time predictions from the grain model (Szekely et al., 1976), the Petersen model, and the random pore models suggests that they are more strongly affected by the representation of the reaction surface than by that of the pore surface. The model is applied to the data of Borgwardt (1970) on the SO2‐lime reaction, and the results are compared with a previous interpretation using a linear concentration gradient approximation.
Hydraulic deliquoring of compressible filter cakes. Part 1: Reverse flow in filter presses
Authors: Tiller Frank M. , Horng Liou‐Liang 
Published: June 2004

AbstractRemoval of liquid from filter cakes can be accomplished by mechanical or hydraulic methods after cake formation is complete. This paper deals with the latter procedure. The local porosity in porous beds (Tiller and Cooper, 1962) is a function of hydraulic pressure distribution and cake compressibility. Calculation of average porosity requires an integration of local values as determined by liquid flow patterns. As most compressions of filter cakes are irreversible, the local porosity is a function of the maximum effective pressure (frictional pressure loss) reached during cyclical operations. Reversal of flow through a cake develops radically changed pressure distributions which can be utilized to reduce local porosities. Analytical expressions are presented for reduction of average porosity brought about by reversing flow of liquid in plate‐and‐frame and recessed plate filter presses.
Modeling of acid hydrolysis of solasodine glycosides. Part I: Formation of solasodine by glycoside hydrolysis
Authors: Crabbe P. G. , Fryer Colin 
Published: June 2004

AbstractSolasodine from Solanum plants is a potential raw material for steroid drug manufacture. Acid hydrolysis of the naturally occuring glycosides of solasodine is a major step in production of the aglycone. As part of a detailed study of the hydrolysis of solasodine glycosides, the hydrolysis procedure has been mathematically modelled. Two models are presented and have been used to obtain kinetic data for the reactions at a number of different reaction conditions. The subsequent conversion of solasodine to solasodiene is considered in Part II of this paper; the combined reactions and guidelines for commercial hydrolysis are presented in Part III.
Modeling of acid hydrolysis of solasodine glycosides. Part III: Combined glycoside hydrolysis and solasodiene formation—guidelines for commercial hydrolysis
Authors: Crabbe P. G. , Fryer Colin 
Published: June 2004

AbstractKinetic models for glycoside hydrolysis and solasodiene formation are combined, and using previous experimental data the effect of changes in reaction conditions on hydrolysis times and the proportion of solasodiene in the final hydrolysed product are established. These are used to give a set of guidelines for commercial hydrolysis. The use of the models for new commercial situations is explained.
Selective propylene oxidation over a copper‐tin oxide catalyst
Authors: Self D. E. , Oakes J. D. , White M. G. 
Published: June 2004

AbstractThe mixed oxide system of copper and tin and the active single oxide, Cu2O, were compared for reducibility of the copper ion, relative number and type of active sites, and reaction kinetics. The enhanced selectivity of the mixed oxides may result from the formation of highly selective sites at the expense of less selective sites. The reducibility of the copper ion in the mixture is influenced by the oxidation state of the tin ion. The reactant and product reaction orders are the same for both catalysts but the mixed oxides are more sensitive to inhibition by water. The catalyst composition affects the energetics of the reaction over the copper‐tin oxide catalysts.
Advanced multivariable control of a pilot‐plant distillation column
Authors: Ogunnaike B. A. , Lemaire J. P. , Morari M. , Ray W. H. 
Published: June 2004

AbstractThis paper reports an experimental study of the multivariable control of a pilot‐plant distillation column having a side stream as well as overhead and bottom products. A recently developed multivariable controller for systems having multiple time delays is implemented for the first time on an experimental process. The controller consists of a new multivariable time delay compensator coupled with traditional PI controllers. Realization is accomplished with a PDP 11 minicomputer. Improved system performance was observed with the delay compensator, especially in disturbance rejection.
Studies in magnetochemical engineering. Part II: Theoretical development of a practical model for high‐gradient magnetic separation
Authors: Liu Y. A. , Oak M. J. 
Published: June 2004

AbstractHigh‐gradient magnetic separation (HGMS) is an existing commercial technology which promises to be an effective means for the large‐scale separation of both weakly magnetic and practically nonmagnetic, micron‐sized particles. It utilizes the strong magnetic forces created typically by placing filamentary ferromagnetic packing materials inside a separator matrix magnetized by a uniform background magnetic field. In this paper, a practical mathematical model for HGMS is developed for quantitatively predicting the grade and recovery of the separated product and the capacity (concentration breakthrough) of the separator. Computer implementation and experimental verification of the new model for HGMS applied to pilot‐scale coal beneficiation are described in Part III.
One variety of quick estimation schemes for parameters in kinetic models
Authors: Watanabe K. , Himmelblau D. M. 
Published: June 2004

AbstractQuick estimation of the parameters in a process model can play a significant role in kinetic studies. This work is aimed at developing a quick estimation strategy by means of process discretization and evaluating errors engendered by the strategy. A systematic error evaluation method and guidelines to select the best discretization relation used in the strategy are described.
Anomalous diffusion of vapors through solid polymers. Part I: Irreversible thermodynamics of diffusion and solution processes
Authors: Neogi P. 
Published: June 2004

AbstractThe solubility and diffusivity of vapors in polymers below and in the vicinity of glass transition temperature are known to be explicitly time‐dependent. It is assumed here that the polymers are in nonequilibrium states, characterized by an internal order. The latter relaxes with time and moves towards equilibrium. The changes in the internal order bring about changes in the properties of the polymer‐solute system.The time dependence of diffusivity and solubility has been derived for isothermal processes not far from equilibrium. Well‐known procedures for analyzing relaxing systems are used to obtain the above results, and the knowledge of how the internal order is related to the molecular properties is not required.
Simplification of quasilinearization method for parameter estimation
Authors: Kalogerakis Nicolas , Luus Rein 
Published: June 2004

AbstractAn alternate development of the quasilinearization method for parameter estimation is presented to enable a more efficient implementation of the algorithm. Similarity of this algorithm to Gauss‐Newton method is shown and attention is given to systems having a nonlinear relationship between the observed and state variables. To overcome the problem of a small region of convergence, the use of direct search optimization is proposed for the first few iterations, followed by the simplified quasilinearization algorithm.
Reconciliation of process flow rates by matrix projection. Part I: Linear case
Authors: Crowe C. M. , Campos Y. A. Garcia , Hrymak A. 
Published: June 2004

AbstractFlow rate measurements in a steady‐state process are reconciled by weighted least squares so that the conservation laws are obeyed. A projection matrix is constructed which can be used to decompose the linear problem into the solution of two subproblems, by first removing each balance around process units with an unmeasured component flow rate. The remaining measured flow rates are reconciled, and the unmeasured flow rates can then be obtained from the solution of the conservation equations. The basic case contains constraints which are linear in the component and the total flow rates. The method is extended to cases with bilinear constraints, involving unknown parameters such as split fractions.Chi‐square and normal statistics are used to test for overall gross measurement errors, for gross error in each node imbalance which is fully measured, and for each measurement adjustment.
Studies in chemical process design and synthesis: Part V: A simple heuristic method for systematic synthesis of initial sequences for multicomponent separations
Authors: Nadgir V. M. , Liu Y. A. 
Published: June 2004

AbstractA simple heuristic method for the systematic synthesis of initial sequences for multicomponent separations is proposed and applied to a number of synthesis problems which have been solved previously using other methods. Based on reported costs, it is shown that the initial sequences synthesized for the test problems by the new heuristic method are cheaper than those obtained by other ordered heuristic methods. These initial sequences are also either identical to or at most a few percents higher in costs than those optimum sequences obtained by other algorithmic, heuristic‐algorithmic and heuristic‐evolutionary methods. The new method is straightforward to apply by hand and it does not require any mathematical background and computational skill from the user.
One‐dimensional model of the physico‐chemical processes occurring inside a burning coal surface
Authors: Massaquoi J. G. M. , Riggs J. B. 
Published: June 2004

AbstractA one‐dimensional model has been developed to account for the physicochemical processes occurring inside a burning wet coal surface. The model considers the vaporization of coal moisture and the existence of a moving evaporation front, pyrolysis and char/gas reactions in the hot zone, molecular diffusion and Darcy flow through the dry porous coal, transpiration cooling effect of the water vapor and pyrolysis gases, temperature‐dependent reaction kinetics and coal thermal conductivity, and variable porousity of the coal due to pyrolysis and char/gas reactions.The model and associated assumptions have been verified with experimental data from the combustion and drying of coal. The results also show that the model prediction of the heat transferred from the coal surface into the coal is much higher than that calculated by the simple heat conduction equation.The fraction of the water in the coal that reacts with char is shown as a function of the linear burn velocity and the surface temperature. In addition, the effect of variations in coal moisture and the thermal conductivity on the thickness of the dry zone are also shwon.
Excess second virial coefficients and critical temperatures: Acetone + methyl acetate
Authors: McElroy P. J. , Hashim H. , Tatt Wong Loke 
Published: June 2004

AbstractFor the system acetone + methyl acetate measurements are reported of excess second virial coefficients (at 75 and 100°C) and critical temperatures for nine different compositions. The efficacy of the correlations due to Tsonopoulos and to Hayden and O'Connell are discussed and the former correlation (with one modification) is shown to give a better prediction of unlike interaction terms. The implication of the results for excess Gibbs Free Energy estimation is discussed.
Oxidative absorption of H2S and O2 by iron chelate solutions
Authors: Neumann D. W. , Lynn Scott 
Published: June 2004

AbstractHydrogen sulfide is oxidized to elemental sulfur by ferric ion chelated with nitrilotriacetic acid (NTA) in aqueous solution at pH 3.5 to 4.5. The reaction appears to be fast relative to gas‐ and liquid‐phase diffusion, and the transfer of H2S from a gas stream is correlated well by the theory of absorption with instantaneous chemical reaction. The ferrous ion formed in this reaction may be reoxidized with oxygen absorbed from a stream of air. The presence of NTA catalyzes the reaction of O2 and Fe2+ in the same pH range, and diffusion is again controlling. Design calculations based on laboratory data for both absorption steps show that cocurrent gas‐liquid contactors are advantageous for achieving high reaction rates (e.g., ∼99.99% H2S removal), high gas velocities (10 to 20 m/s), low pressure drops [1 to 3 kPa (10 to 30 cm H2O)], and moderate column heights (10 to 15 m).
Computer‐aided synthesis and design of plant utility systems
Authors: Petroulas T. , Reklaitis G. V. 
Published: June 2004

AbstractA design synthesis procedure is developed for preliminary design of utility systems. Given known steam sources (waste heat and auxiliary boilers) and sinks (heating, process injection, and driver horsepower needs), the algorithm determines the optimal header pressure levels, the distribution of steam turbines in the network, and the steam flows between all devices so as to maximize the real work recovered from the sources. Any number of pressure levels can be accommodated at only modest increase in computational effort.
Fate of solids fed pneumatically through a jet into a fluidized bed
Authors: Kececioglu Ifiyenia , Yang Wen‐Ching , Keairns D. L. 
Published: June 2004

AbstractSolid tracer particles were fed pneumatically through a jet into a fluidized bed to simulate the feeding of solids via a pneumatic transport line into a fluidized‐bed reactor operating in the slugging‐bed mode. The fluidized bed was defluidized instantaneously at different times after the initiation of the tracer particle injection. The bed was then sampled layer by layer to provide the radial and axial concentration profiles of the tracer. Regular and high‐speed movies (1,000 frames per second) were taken to study the operation of the fluidized bed and the phenomena of the gas‐solid two‐phase jet.Experimental results on solid mixing, jet constriction and slugging frequencies, slugging bed height, slug length, jet penetration, and jet half‐angle at three nominal jet velocities of 52, 37, and 25 m/s and corresponding solids loadings are presented. Additional experimental results on jet constriction and slugging frequencies, and slug volume (axial slug size) obtained for a wider range of jet velocities confirm the hydrodynamic trends observed during the tracer particle injection experiments. The results indicate that solids mixing increases, and well‐mixed conditions are reached earlier, with an increase in jet injection velocity. The obtained mixing times were correlated successfully in terms of the excess gas velocity. The experimental data on jet penetration and slug motion were satisfactorily correlated by modified versions of existing theoretical relations. The modifications included the effect of the injected solids on jet penetration and jet half‐angle and also the effect of our semicircular column geometry and single wall‐slug configuration on the observed slug motion.
Determination of catalyst surface area from desorption characteristics of physisorbed gases
Authors: Miller D. J. , Lee H. H. 
Published: June 2004

AbstractA new experimental method for the measurement of catalyst surface area of supported catalysts has been developed using selective physisorption. The desorption characteristics of a gas are studied separately on the catalyst, the support, and the supported catalyst by carrying out thermal desorption experiments in a continuous flow sorptometer. Differences in the coverage vs. temperature curves, obtained from the thermal desorption experiments, are a measure of the selectivity of the physisorbing gas, and allow calculation of the fraction of total surface area occupied by the catalyst.Two systems have been studied utilizing the thermal desorption with carbon dioxide as adsorbate: potassium carbonate/carbon black and silver/alumina. Supported catalyst surface area was determined for each system; the results were confirmed using physical mixtures of the two components (where the actual area of each component is known) and oxygen chemisorption for the silver/alumina system. The experimental technique allows for straightforward calculation of the catalyst area.
Dispersion, mass transfer and chemical reaction in multiphase contactors: Part I: Theoretical developments
Authors: Hatton T. A. , Lightfoot E. N. 
Published: June 2004

AbstractThe convective dispersion theory of Gill and Sankarasubramanian is extended to allow for multiphase mass transfer interactions in column‐type contactors, and for multisolute, reversible and irreversible, homogeneous and wall‐catalyzed heterogeneous chemical reactions in the individual phases. This theory can now be applied in any transverse average, not just the area average used in the past, and additional interactions between the phases not normally accounted for in the traditional axial dispersion model are indicated.
Dynamic behavior of a porous char particle burning in an oxygen‐containing environment: Part I: Constant particle radius
Authors: Sotirchos S. V. , Amundson N. R. 
Published: June 2004

AbstractThe transient combustion of porous char particles is modelled. The model takes into account the reactions of carbon with CO2 and O2 and the oxidation of CO in the gas phase. It reveals strong effects of the intraparticle thermal gradients and of the pore structure evolution scheme on the burning time and predicts an optimum particle size that gives minimum burning time.
Structural analysis and solution of systems of algebraic design equations
Authors: Book N. L. , Ramirez W. F. 
Published: June 2004

AbstractA new method for expressing the structure of a system of equations is developed using a type of occurrence matrix entitled the functionality matrix. The functionality matrix indicates not only the occurrence of variables in equations but also the functional form in which they occur. Since the difficulty of solving an equation for a variable is related to its functional form, analysis of the functionality matrix provides explicit information on the difficulty of solution of the solution of the equation.A methodology for the solution of design problems by digital computers is described. This methodology operates on the functionality matrix which describes the set of design equations. Algorithms using this methodology interact and guide the designer in an efficient selection of design variables and redundant equations. Once design variables and redundant equations are selected, a computational method is presented for ordering and solving the equations.
Mass transfer in AC electrolysis part I: Theoretical analysis using a film model for sinusoidal current on a rotating hemispherical electrode
Authors: Cheng C. Y. , Chin D‐T. 
Published: June 2004

AbstractA film model is presented for the analysis of mass transfer to a rotating hemispherical electrode when sinusoidal alternating current (AC) together with direct current (DC) are flowing across the electrode surface. The concentration of a diffusing ion is separated into two independent components: a constant DC component and a periodic AC component. The DC concentration is obtained by solving the steady‐state convective mass transport equation with the perturbation method. The periodic AC concentration distribution is analyzed by the solution to the one‐dimensional transient diffusion equation based on the concept of Nernst diffusion layer. The limiting AC current densities corresponding to a zero surface concentration of a reactive ion are investigated for various DC current densities and AC frequencies. The resulting periodic concentration overpotential wave and its phase shift with respect to the applied AC are examined. A comparison with a previous rigorous model indicates that the film model is a good approximation to the mass transfer calculation in the regimes of a dimensionless AC frequency K = (ω/Ω)Sc1/3 greater than 2 and less than 0.01.
Evolution of pore volume distribution during gasification
Authors: Su Jow‐Lih , Perlmutter D. D. 
Published: June 2004

AbstractA general equation is derived that predicts the evolution of pore volume distribution during isothermal gasification in the regime of kinetic control, starting from a given initial condition. The development takes into account pore enlargement as well as pore intersections. Equations are also derived for the special cases of (1) uniform pore size and (2) bimodal distribution. The results are used to interpret the experimental data of Tomkow et al. (1977) and Kawahata and Walker (1962).
hydrodynamic parameters for gas‐liquid cocurrent flow in packed beds
Authors: Sáez A. E. , Carbonell R. G. 
Published: June 2004

AbstractThe hydrodynamics of cocurrent gas‐liquid flow in packed beds is analyzed by extending the concept of relative permeability to the inertial regime.The relative permeabilities of the gas and liquid phases are functions of the saturation of the liquid phase. These functions are found from an analysis of experimental data. The relations obtained are used to develop empirical correlations for predicting liquid holdup and pressure drop in gas‐liquid cocurrent downflow in packed beds over a wide range of operating conditions. The correlations proposed give very good results when compared to experimental data yielding, in general, mean relative deviations lower than existing correlations. In addition, a new equation is proposed for predicting static holdup in packed beds which is based on a more physically realistic characteristic length than that used in previous studies.
Evaluation of changeover control policies by singular value analysis—Effects of scaling
Authors: Lau Henry , Jensen K. F. 
Published: June 2004

AbstractA method for assessing control performance at different operating conditions in a chemical process is developed using singular value analysis. The control potential of the system is established by analyzing the singular values of the steady‐state system matrix. Dynamic considerations and interaction analysis can be included in the framework of the method described. The approach enables the process engineer to consider controllability of the process as well as economics in synthesizing a changeover control policy. Singular values depend on the scaling of the system, i.e., the definition of the physical dimensions of the system. The effects of scaling on the analysis are first investigated by scaling the steady‐state system matrix with empirical methods, equilibration, and geometric scaling. Using the insights gained from these studies a scaling method, variable normalization and equation equilibration, which is intuitively appealing and suited for the purpose, is devised. Two typical systems, continuous stirred tank reactor and a polymerization reaction system, demonstrate the usefulness of this method.