bluuebunny/crossref_metadata_2025_split huggingface dataset:
Maximum likelihood data rectification: Steady‐state systems
Authors: Johnston Lloyd P. M. , Kramer Mark A. 
Published: June 2004

AbstractA maximum likelihood rectification (MLR) technique that poses the data‐rectification problem in a probabilistic framework and maximizes the probability of the estimated plant states given the measurements is proposed. This approach does not divide the sensors into “normal” and “gross error” classes, but uses all of the data in the rectification, each sensor being appropriately weighted according to the laws of probability. In this manner, the conventional assumption of no sensor bias is avoided, and both random errors (noise) and systematic errors (gross errors) are removed simultaneously. A novel technique is introduced that utilizes historical plant data to determine a peior probability distribution of the plant states. This type of historical plant information, which contains the physical relationships among the variables (mass balances, energy balances, thermodynamic constraints), as well as statistical correlations among the variables, has been ignored in prior data‐rectification schemes. This approach can use the historical plant information to solve a new class of data‐rectification problems in which there are no known model constraints. The MLR method is demonstrated on data from a simulated flow network and a simulated heat‐exchanger network. The MLR technique provides considerably improved performance over existing data‐reconciliation schemes in these examples.
Synthesis of separation system flowsheels
Authors: Douglas J. M. 
Published: June 2004

AbstractA hierarchical decision procedure for the synthesis of separation system flowsheets for vapor–organic liquid– aqueous liquid– solid mixtures is proposed. An expanded set of synthesis rules that can be used to obtain a first design is discussed, but the final goal of the procedure is to generate a complete list of separation alternatives (by changing the decisions) that when coupled with short‐cut screening techniques, can be used to identify the best few process flowsheets. The procedure is based on a decomposition of the separation system synthesis problem by phase splitting into a vapor recovery system, a solid recovery system, and liquid separation systems. A general superstructure presented for these subsystems includes all of the common unit operations for petrochemical processes. The procedure focuses on the development of a complete flowsheet for the separation system: which separation system recycle loops (in contrast to reactor system recycle loops) are required, as well as interactions among separation subsystems and those between the separation system and remainder of the process. An example presented illustrates the procedure, and the opportunities for pollution prevention at the source are noted.
Electrochemically modulated complexation process for gas removal and concentration
Authors: Terry Patricia A. , Walis H. Jeremy , Noble Richard D. , Koval Carl A. 
Published: June 2004

AbstractAn electrochemically modulated complexation process was designed to extract and concentrate a gas‐phase solute. The process was based on flowthrough electrolysis cells that electrochemically modulate a liquid‐phase mass‐transfer agent between high and low solute affinity forms. The liquid phase in the high‐affinity form contacts a feed gas phase for the extraction and contacts the receiving gas phase in the low‐affinity form. The chemical system used to demonstrate the general process was a Cu(II)/Cu(I) redox couple in an acidic chloride electrolyte to both concentrate carbon monoxide against a pressure gradient and selectively separate it from a mixture with nitrogen. Experimental results and modeling of this process are reported. The kinetics of the electrolysis reactions in the flow cells are discussed within the context of rotating ring disk voltammetry experiments.
Modeling and dynamic simulation of a bleach plant
Authors: Wang R. X. , Tessier P. J.‐C. , Bennington C. P. J. 
Published: June 2004

AbstractA dynamic model of five‐stage (C+D)EDED bleach plant was developed using SIMNON a dynamic simulation language developed at Lund Institute of Technology, as a platform. The model is composed of individual modules that represent each bleaching stage. Each module includes chemical addition and mixing, diffusion and reaction in a retention towel, and washing. These unit operations are coupled with chemical kinetics for each bleaching stage using appropriate models. A relationship between the (C+D)E Kappa number and the input absorption coefficient to the D1 stage was used to link the delignification and brightening partial sequences of the bleach plant. The model, verified using steady‐state data, was used to model the dynamic response of the plant to step changes in production rate, (C+D) chemical addition, and incoming Kappa number, as well as the open‐loop response of the plant to a simulated variation in incoming Kappa number. The modular structure of the program allows a variety of bleach plants to be assessed once flow parameters and chemical kinetics are known. The dynamic model can also be used to develop and compare control strategies before being implemented at the mill.
Asphalt flocculation and deposition: I. The onset of precipitation
Authors: Rassamdana Hossein , Dabir Bahram , Nematy Mehdi , Farhani Minoo , Sahimi Muhammad 
Published: June 2004

AbstractFormation of asphalt aggregates and their deposition on the pore surfaces of a porous medium, which alter the structure of the medium and its effective properties, is a critical problem to catalytic and oil recovery and refinery processes. Extensive new experimental data for the amount of precipitated asphalt formed with crude oil and various solvents are presented. Results indicate that, contrary to the previous assumptions, asphalt formation is at best partially reversible. A thermodynamic model based on the Flory–Huggins theory of polymer solutions is used, together with the Soave equation of state, to predict the data. Critical evaluation of the model shows that its predictions do not agree well with our data. As an alternative, we propose a new model that employs a scaling equation, somewhat similar to those encountered in aggregation and gelation phenomena. The scaling function takes on a very simple form, and its predictions are in very good agreement with the data. It also predicts that the onset of precipitation may obey a simple universal equation.
Velocity profiles in a baffled vessel with single or double pitched‐blade turbines
Authors: Armenante Piero M. , Chou Chun‐Chiao 
Published: June 2004

AbstractA laser‐Doppler velocimetry (LDV) apparatus and a computational fluid dynamic (CFD) software package (FLUENT) were used to experimentally determine and numerically predict the velocities in a baffled vessel agitated by one or two 45° pitched‐blade turbines. The flow characteristics in the impeller regions were measured by LDV and used as boundary conditions in the numerical computations. Turbulence effects were simulated using either the k‐ε model or algebraic stress model (ASM). The CFD predictions were compared to the LDV measurements in terms of average velocities in all three directions as well as turbulent kinetic energies. Predictions based on ASM were typically in closer agreement with the experimental data than those based on the k‐ε model. Flow patterns in both configurations were dominated by the axial and tangential components. The presence of the upper impeller altered the flow considerably, producing a strong vertical recirculation pattern between the impellers and significantly reducing the circulation flow below the lower impeller.
Journal review. Azeotropic distillation
Authors: Widagdo Soemantri , Seider Warren D. 
Published: June 2004

AbstractRecent and ongoing research in the distillation of nonideal mixtures is reviewed focusing on advances in the methodologies for the synthesis, design, analysis and control of separation sequences involving homogeneous and heterogeneous azeotropic towers. Maps of residue curves and distillation lines are examined, as well as geometric methods for the synthesis and design of separation sequences, trends in the steady‐state and dynamic analysis of homogeneous and heterogeneous towers, the nonlinear behavior of these towers, and strategies for their control.Emphasis is placed on the methods of computing all of the azeotropes associated with a multicomponent mixture, on the features that distinguish azeotropic distillations from their zeotropic counterparts, on the potential for steady‐state multiplicity, and on the existence of maximum and minimum reflux bounds. Important considerations in the selection of entrainers are examined. For the synthesis of separation trains, when determining the feasible product compositions, the graphical methods are clarified, especially the conditions under which distillation boundaries can be crossed and bounding strategies under finite reflux. The application of geometric theory to locate the fixed points, at minimum reflux, is reviewed in connection with homotopy‐continuation algorithms for this purpose. The use of homotopy‐continuation algorithms, especially for the steady‐state simulation of heterogeneous azeotropic distillations, is justified. Methods for phase stability analysis are reviewed in connection with the location of real bifurcation points at phase transitions, an important feature of algorithms for the dynamic simulation of heterogeneous azeotropic distillations.
Drying with internal heat generation: Theoretical aspects and application to microwave heating
Authors: Constant T. , Moyne C. , Perré P. 
Published: June 2004

AbstractA model of simultaneous heat and mass transfer presented describes drying with internal heat generation. Since a liquid expulsion phase is observed, a numerical procedure was developed to account for saturated and unsaturated zones and to model the liquid expulsion. The model was validated by a drainage experiment. An experimental rig was built to conduct microwave drying experiments in well‐controlled conditions using capillary porous body (light concrete) as test material. Two types of drying (high and low power) were distinguished, depending on whether or not boiling occurred in the sample. The heat source term in the medium was determined from the experimental results. The numerical results agree with the experimental observations in terms of drying kinetics and transfer mechanisms. This allows a very accurate description of the transport phenomena and the liquid expulsion phase associated with high‐power drying.
Adsorption of carbon monoxide on activated carbon impregnated with metal halide
Authors: Tamon Hajime , Kitamura Kenji , Okazaki Morio 
Published: June 2004

AbstractActivated carbon was impregnated with a metal halide, and adsorption and desorption characteristics of CO on the carbon were measured by fixed‐bed runs. It was found that the impregnation of PdCl2 or CuCl effectively increases CO absorption. PdCl2/CuCl‐impregnated carbons were characterized by N2 adsorption, SEM, EPMA, and XPS. Adsorption isotherms of CO were also measured on these carbons, and the influence of the loading of impregnant on CO adsorption was experimentally elucidated. A selection procedure of impregnant was proposed based on the frontier orbital theory. The perturbation energy for molecular orbital mixing was estimated by the HOMO – LUMO interaction. CO adsorption on impregnated carbons was qualitatively interpreted using the perturbation energy, and the energy was regarded as an index of impregnant selection.
Predictive control of quality in batch polymerization using hybrid ANN models
Authors: Tsen Andy Yen‐Di , Jang Shi Shang , Wong David Shan Hill , Joseph Babu 
Published: June 2004

AbstractTwo issues involving the methodology used for on‐line control of product quality in batch manufacturing processes are addressed: the generation of fast, data‐driven process models and the use of such process models for on‐line feedback control of product quality. The methodology is investigated using the example of the control of dispersity and molecular weight distribution in a batch reactor for emulsion polymerization of vinyl acetate. An artifical neural network (ANN) is used as a model to predict the quality as a function of the manipulated variables and on‐line measurements. This model is constructed using an augmented dataset that integrates experimental information and knowledge from a mathematical model. The proposed model is compared with other types such as a theoretical model whose key parameters are fitted to experimental data. The hybrid ANN is superior to the parameter‐fitting approach for this case. Experimental and simulation studies confirm the advantage of using the proposed model and the predictive control algorithm.
Radiative transfer in photocatalytic systems
Authors: Pasquali Matteo , Santarelli Francesco , Porter John F. , Yue Po‐Lock 
Published: June 2004

AbstractRadiation absorption at the surface of catalytic particles is the initial step of photocatalytic oxidation reactions currently considered for their potential effectiveness in the treatment of polluted water with traces of highly toxic organics. Owing to the presence of catalyst particles within the fluid phase, the radiation field within a photocatalytic reactor results from the absorption and scattering within the participating medium. An annular reactor with a coaxial central lamp was considered, and the resulting 2‐D radiation field was analyzed using a Monte Carlo technique to solve the radiative transfer equation. Results are discussed based on the relevant optical parameters, and a heuristic is derived for the design and rating of a photocatalytic reactor. To exploit the reaction volume effectively, the order of magnitude of the optical thickness should be close to unity, and for a given value of the absorption coefficient the catalyst with the lowest albedo should be selected; however, a precise evaluation of the phase function is not crucial to a relable representation of the radiation field.
Phase equilibria and volumetric properties of aqueous CACl2 by an equation of state
Authors: Jiang Shaoyi , Pitzer Kenneth S. 
Published: June 2004

AbstractA comprehensive equation of state was developed to represent the phase equilibria and volumetric properties of aqueous calcium chloride solutions at temperatures above 523 K. The equation consists of a reference part and a perturbation contribution. The reference function is developed from the statistical mechanical theory for mixtures of dipolar and quadrupolar hard spheres, which agrees well with the Monte Carlo simulation results. In this treatment, calcium chloride is described by the completely undissociated model. The empirical perturbation function is a truncated series of virial expansion terms. Thus, mixing rules are guided by those of virial coefficients, which are derived rigorously from statistical mechanics. The equation reproduces experimental saturated vapor pressures and volumetric data within experimental uncertainty for temperatures to 623 K. At higher temperatures, few and less accurate experimental data are available, but values of the saturated vapor pressures of the liquid have been reported and are represented satisfactorily.
Leveling of a film with stratified viscosity and insoluble surfactant
Authors: Joos F. Miguel 
Published: June 2004

AbstractThe evolution of a film with insoluble surfactant on a wavy horizontal wall differs from flow without surfactant (the way it usually is studied) in that the film passes through different stages. The first stage is as if the surfactant were absent. Once the surface tension gradient—induced by the nonuniform surfactant concentration adsorbed at the free surface—starts resisting the flow effectively, the evolution enters a transitional stage. A final stage is reached once the free surface becomes rigid due to the surface‐tension gradient (high elasticity limit) or becomes virtually leveled before the surface‐tension gradient is released (low elasticity limit). The velocity profile through the film changes with time, sol fluid is depleted or accumulated at different strata in the film as the flow evolves. The velocity profile and resulting deformations throughout the film can be influenced significantly by the viscosity distribution or stratification, which occurs, for example, when multiple layers of different viscosity are coated simultaneously. A model and applications for the leveling of such a film are presented. The evolution is described in general terms for a film of uniform viscosity and for a film of two discrete layers of different viscosity. Then the three limiting cases are established. For two of these limits, the effect on the exponential decay rate of the flow and the deformation of the different strata or layers is examined when the viscosity is changed in an infinitesimally thin layer or stratum, and in a layer of finite thickness in films of two and three discrete layers.
Absorption of chlorine into aqueous bicarbonate solutions and aqueous hydroxide solutions
Authors: Ashour Sami S. , Rinker Edward B. , Sandall Orville C. 
Published: June 2004

AbstractThe absorption of Cl2 into aqueous bicarbonate and aqueous hydroxide solutions was studied both experimentally and theoretically. The rate coefficient of the reaction between Cl2 and OH− was estimated over the temperature range of 293–312 K and fitted by the Arrhenius equation:

.If Cl2 were assumed to react only with water and OH− in an aqueous bicarbonate solution, the predicted absorption rate would be much lower than that experimentally measured. This suggests that Cl2 reacts with HCO3− in an aqueous bicarbonate solution. The rate coefficient of the reaction between Cl2 and HCO3− was estimated over the temperature range of 293–313 K and fitted by the Arrhenius equation:

.More importantly, under absorption conditions, the amount of hydroxide consumed for absorbing a specific amount of Cl2 into an aqueous hydroxide solution is almost twice the amount of bicarbonate consumed for absorbing the same amount of Cl2 into an aqueous bicarbonate solution.
Thermal frequency response method for the study of mass‐transfer kinetics in adsorbents
Authors: Bourdin V. , Grenier Ph. , Meunier F. , Sun L. M. 
Published: June 2004

AbstractThe frequency response method measuring the temperature and pressure of an adsorbent sample determines the mass‐ and heat‐transfer kinetics in adsorbents, especially in zeolites. The temperature of the sample (large crystals or monolayers of pellets) is measured by infrared detection. The main aspects of the in‐phase and out‐of‐phase functions as given by an analytical bidispersed model are described. They depend on characteristic times related to kinetic paprameters. Experimental results on adsorption of water on NaX zeolite (crystals or pellets) show that this method allows heat transfer to be very clearly delineated from mass‐transfer modes and the separation of different mass‐transfer modes. For a bidispersed sample, macro‐ and microporous mass‐transfer parameters may be obtained with the same sample. Results on a contaminated 5A zeolite‐propane system show the presence of mass‐transfer resistance at the pellet surface. The infrared temperature measurement associated with the frequency response appears to be powerful in determining kinetic adsorption, and gives more information than the pressure measurement.
Adsorption of associating molecules in micropores and application to water on carbon
Authors: Talu Orhan , Meunier Francis 
Published: June 2004

AbstractA general theory for the adsorption of self‐associating molecules in microporous structures is developed. The approach is similar to the “chemical” interpretation of nonideality of vapor and liquid phases. The theory displays Type 5 isotherm behavior and can explain Types 1 and 5 transition. Isothermal data are represented by only three parameters: Henry's law constant, saturation capacity, and reaction constant for “cluster” formation in the micropores. When isotherms at different temperatures are available, the theory can be used with five temperature‐independent parameters to describe the entire phase behavior including the heat of adsorption. Water adsorption on activated carbon, the most common display of Type 5 behavior, is used to test the theory. Analysis of several data sets indicates that the theory can closely correlate data, provide physically meaningful parameter values in line with carbon properties, and it is highly effective in correlating temperature variation. The reaction enthalpy for water dimerization in the carbon micropores is lower than that in vapor phase. This preliminary conclusion with the theory needs to be supported with more accurate data when available.
Effects of mixing on the composition and morphology of tissue‐engineered cartilage
Authors: Vunjak‐Novakovic Gordana , Freed Lisa E. , Biron Robert J. , Langer Robert 
Published: June 2004

AbstractCartilage constructs were grown using isolated chondrocytes and biodegradable polymer scaffolds made of fibrous polyglycolic acid in the form of 1‐cm‐dia × 5‐mm‐thick discs. The scaffolds were seeded in a mixed cell suspension and cultured for up to 8 weeks under static or mixed tissue culture conditions in petri dishes and spinner flasks. Turbulent mixing significantly improved the biochemical compositions and altered morphologies of the cartilage constructs, which were the thickest ones cultured to date in vitro. Constructs from mixed cultures were more regular in shape and contained up to 70% more cells, 60% more sulfated glycosaminoglycan, and 125% more total collagen when compared to constructs from static cultures. Mixing also induced the formation of an outer capsule with multiple layers of elongated cells and collagen fibrils around the inner tissue phase, while statically grown constructs consisted of round cells embedded in cartilaginous matrix. Mixing during cell seeding and tissue culture is thus an important parameter for the cultivation of tissue‐engineered cartilage in a range of sizes, shapes and compositions for a variety of clinical applications (e.g., fibrous cartilage for reconstructive surgery or articular cartilage for joint resurfacing).
Fickian diffusion in binary mixtures that form two liquid phases
Authors: Pertler Manfred , Blass Eckhart , Stevens Geoffrey W. 
Published: June 2004

AbstractNew data on the variation of the diffusion coefficient with concentration in binary nonideal liquid mixtures are presented. The diffusion coefficients were measured with laser holography with an improved analysis procedure and are primarily in systems that form two liquid phases. The results show that for such systems the diffusion coefficient is constant if a chemical‐potential driving force is used. If, however, the miscibility gap is wide, the Schreiner equation (Schreiner, 1922) is shown to be more accurate than relations that consider the variation of viscosity. Cluster theories developed for diffusion behavior near critical points were found to explain the data well only in water‐organic systems on the water‐rich side.
Wall effects on the sedimentation velocity of suspensions in viscous flow
Authors: Di Felice Renzo , Parodi Enrico 
Published: June 2004

AbstractThe sedimentation velocity of multiparticle suspensions was investigated experimentally for cases where the column wall is likely to have a nonnegligible effect. The experiments demonstrate that the container wall diameter influeces the falling velocity only for dilute systems, which is in contrast with a widely used, established empirical relationship.