bluuebunny/crossref_metadata_2025_split huggingface dataset:
Coating on a rough surface
Authors: Clarke Andrew 
Published: April 2004

AbstractCommercial products such as photographic materials and speciality papers manufactured by single or multilayer coating processes, all have some surface topographic structure. Nevertheless, for many materials, a uniform plane approximates their surface, and analyses of dynamic wetting, a fundamental physical process which determines coating process limits, usually assume this condition. It is demonstrated here that under certain combinations of coating process parameters, the maximum coating speed is not predicted even qualitatively by using this assumption. Furthermore, the experiments indicate that a second coating mechanism supersedes complete wetting and promotes extremely high coating speeds.
Modeling and optimizing submerged hollow fiber membrane modules
Authors: Chang S. , Fane A. G. , Vigneswaran S. 
Published: April 2004

AbstractThe filtration behavior of submerged hollow fiber membranes with constant permeate flow operational mode was modeled on two different conditions: the maximum initial flux along the fiber is smaller than the critical flux (Jimax < Jcr); the maximum initial flux along the fiber is greater than the critical flux, but the averaged imposed flux is smaller than the critical flux (Jimax > Jcr but Jmi < Jcr). When the maximum initial flux along the fiber is lower than the critical flux, no particle deposition occurs and the flux distribution can be characterized by a dimensionless parameter ξ = 4LRR. On the other hand, for Jmi < Jcr and Jimax > Jcr, a steady state can be achieved after some initial deposition. The theoretical model shows that the filtration resistance caused by the initial deposition can be affected by Jmi/Jcr and fiber characteristics (L, Ri and Rm) and becomes significant for narrow and long fibers with a high Jmi/Jcr. The models were also used to determine the optimal fiber length and radius for the submerged hollow fiber module. The simulation suggests that the optimal fiber lumen radius for fiber lengths of 0.5–3 m is 0.2–0.35 mm. These results should be relevant to the design of submerged hollow fiber modules.
Adsorption of mixtures containing subcritical fluids on activated carbon
Authors: Do D. D. , Do H. D. 
Published: April 2004

AbstractA theoretical analysis of adsorption of mixtures containing subcritical adsorbates into activated carbon is presented as an extension to the theory for pure component developed earlier by Do and coworkers. In this theory, adsorption of mixtures in a pore follows a two‐stage process, similar to that for pure component systems. The first stage is the layering of molecules on the surface, with the behavior of the second and higher layers resembling to that of vapor–liquid equilibrium. The second stage is the pore‐filling process when the remaining pore width is small enough and the pressure is high enough to promote the pore filling with liquid mixture having the same compositions as those of the outermost molecular layer just prior to pore filling. The Kelvin equation is applied for mixtures, with the vapor pressure term being replaced by the equilibrium pressure at the compositions of the outermost layer of the liquid film. Simulations are detailed to illustrate the effects of various parameters, and the theory is tested with a number of experimental data on mixture. The predictions were very satisfactory.
Optimization of a simulated moving bed based on an approximated langmuir model
Authors: Yu Hong Wei , Ching Chi Bun 
Published: April 2004

AbstractBased on the “triangle method,” a shortcut method was developed to establish the possible optimal operating condition of a SMB unit, because the theoretical optimal operating condition was diverted from the actual complete separation region by too many unexpected disturbances. A new CSP was used in the simulated moving bed for the enantioseparation of fluoxetine. Good separation results were obtained. The effects of the difference between m2 and m3 on performance parameters were studied. The results show that this method is useful for establishing the operating conditions. It can be concluded that the new CSP is efficient for the enantioseparation of chiral drugs.
New MILP formulation for instrumentation network design and upgrade
Authors: Bagajewicz Miguel , Cabrera Enmanuel 
Published: April 2004

AbstractThe problem of instrumentation network design and upgrade consists of determining the optimal set of instruments to obtain sufficiently accurate and reliable estimates of variables. An existing formulation of the cost optimal sensor network design and upgrade problem (Bagajewicz, 1997) is in the form of a mathematical programming problem, but it has the disadvantage that the constraints are not stated explicitly in analytical form, forcing therefore a special tree search solution procedure. An alternative MILP formulation is presented, which is useful for small to medium size problems, where all constraints are explicit.
Oxidative coupling of methane in dense ceramic membrane reactor with high yields
Authors: Akin F. T. , Lin Y. S. 
Published: April 2004

AbstractOxidative coupling of methane (OCM) was studied with dense tubular Bi1.5Y0.3Sm0.2O3 (BYS) membranes at various temperatures (870–930°C). BYS powders were synthesized by a citrate method. Tubular‐shaped dense membranes of BYS in the fluorite‐type FCC phase structure were fabricated by cold isostatic pressing with green machining. The best one‐pass C2 (C2H4 + C2H6) yield achieved for OCM in the BYS dead‐end membrane reactor was 35% at a C2 selectivity of 54% at 900°C. At the same C2 yield, the membrane reactor mode gives C2 selectivity of over 200% higher than the cofeed mode in the same membrane reactor under similar conditions. The oxygen permeation fluxes through tubular BYS membrane reactors under OCM reaction conditions are approximately 1.5 to 3.5 times higher than those under oxygen permeation conditions with He as the purge. After 6 days of OCM, BYS membrane remained in good integrity with minor phase segregation observed at the reaction side of the membrane.
Measurement and calculation of critical points for binary and ternary mixtures
Authors: Horstmann Sven , Fischer Kai , Gmehling Jürgen 
Published: April 2004

AbstractThe critical lines (temperatures and pressures) for the three binary mixtures ethane + sulfur hexafluoride (SF6), SF6 + propane, and carbon dioxide (CO2) + SF6, and the critical surface for the ternary system CO2 + ethane + SF6 were determined experimentally by a flow method. The binary data were compared to predictions using the predictive Soave‐Redlich‐Kwong (PSRK) group contribution equation of state (EoS). For the system CO2 + SF6, where no phase equilibrium information is available, the critical points were used to optimize the required PSRK group interaction parameters. Using these binary parameters, the ternary critical plane was predicted reliably.
Immunoadsorption model for a novel fluidized‐bed blood detoxification device
Authors: Grovender Eric A. , Cooney Charles L. , Langer Robert , Ameer Guillermo A. 
Published: April 2004

AbstractA multicompartment Taylor‐Couette flow hemofilter was designed to remove toxins from a patient's bloodstream via immunoadsorption. This device (Vortex Flow Plasmapheretic Reactor, VFPR) treats blood plasma with a fluidized‐bed of small (45–165×10−6 m diameter) particles, while protecting fragile blood cells from lysis. The potential application for the VFPR is dialysis‐related amyloidosis, a disease associated with the systemic accumulation of beta‐2‐microglobulin in patients with long‐term kidney failure. The equilibrium behavior of immunoadsorptive gel beads is characterized experimentally and theoretically using confocal microscopy and the Langmuir adsorption isotherm. The importance of external mass‐transfer resistance within the active compartment is assessed through dissolution studies conducted with benzoic acid particles. These results are combined with mass‐transfer fundamentals to develop a dynamic immunoadsorption model. The modeling results, without the use of adjustable parameters, agree with the experimental data and provide a foundation for further development and eventual application.
Colloid‐Associated contaminant transport in porous media: 1. Experimental studies
Authors: Sen Tushar Kanti , Mahajan S. P. , Khilar Kartic C. 
Published: April 2004

AbstractMany studies have identified colloid‐associated transport of contaminants as an important mechanism of contaminant migration through groundwater. It is a complex phenomenon in porous media involving several basic processes such as adsorption of contaminants, release and migration of colloidal fines, and entrapment of fines at the pore constrictions. The effects of these basic processes on the contaminant transport are studied. Column experiments are conducted to study the effects of the mobilization and migration of colloidal fines, kaolin on the transport of contaminant, and Ni2+ metal ion through the sand beds containing kaolin particles under both nonplugging and plugging conditions. As reported in literature, colloidal fines can facilitate the contaminant transport when they migrate with the flow. In the absence of migration, kaolin‐sand beds retard Ni2+ transport in comparison to sand beds due to their higher adsorption capacity, but the sand‐kaolin composite bed acts like an inefficient adsorption column with percentage saturation (which is in general below 25%). It is interesting to note that under plugging conditions, which can be induced by using a lower bead size to particle‐size ratio, the breakthrough curves are more flattened and delayed at a higher kaolin content of the bed.
Batch extractive distillation of maximal azeotrope with middle boiling entrainer
Authors: Lelkes Z. , Rev E. , Steger C. , Fonyo Z. 
Published: April 2004

AbstractSeparation of maximum boiling azeotropes using batch extractive distillation (BED) is feasible in a rectifying column with intermediate boiling entrainer. The main difference between BED and solvent‐enhanced batch distillation (SBD) is the application of continuous entrainer feeding to the column or still. Finding a well‐working intermediate boiling entrainer is more difficult than finding a heavy or light entrainer. The test mixture, selected according to didactic viewpoints, is chloroform and ethyl acetate with 2‐chlorobutane. Operation steps (sequencing), limiting flows, and limiting stage numbers are determined by a feasibility study, based on profile maps; the design is validated by rigorous simulation. Results of parametric studies and comparison of SBD and BED, according to effectiveness, are presented. Separation of maximum boiling azeotropes in SBD and BED is feasible with an intermediate boiling entrainer, but the application of continuous feeding (characteristic to BED) makes the process more efficient. Pure‐component A cannot be produced in SBD or BED, but producing component A mixed with entrainer and free of component B is feasible in both processes. The operation steps are similar in the two processes except for continuous feeding of the entrainer in step 2 of BED. With identical specification and comparable operation parameters, BED produces the same products in a shorter time and with a significantly smaller amount of maximum holdup in the still.
Effect of mixing on efficiencies for reactive tray contactors
Authors: Fisher Kevin S. , Rochelle Gary T. 
Published: April 2004

AbstractThe relationship between point efficiencies and Murphree tray efficiencies was studied for systems where reactions take place in the liquid within a tray column. For nonreactive systems, several well‐known mixing models are available for predicting Murphree tray efficiency from point efficiencies. For reactive systems, the magnitude and nature of the effect of mixing on tray efficiency are different. An analytical representation is developed of the mixed‐pool and plug‐flow mixing models for reactive systems with first‐order kinetics, and there are different regimes, depending on the reaction kinetics. For each of these regimes, the effect of mixing on tray efficiency differs in magnitude and arises from different mechanisms. The resulting tray efficiencies predicted for reactive systems using the methods may differ by an order of magnitude or more from the values predicted when standard methods for nonreactive trays are applied to reactive trays.
Sectional and overall reachability for systems with S‐shaped distillation lines
Authors: Hoffmaster Warren R. , Hauan Steinar 
Published: April 2004

AbstractTotal and minimum reflux bounds serve as limiting case scenarios for determining feasibility in azeotropic distillation columns. Specifically, all reachable feed compositions in a staged rectifying or stripping section have been reported as the union of points enclosed by the distillation and pinch‐point curves through a desired product. By eigenvalue considerations of pinch bifurcations and geometric analysis of fundamental region structures, the region of all reachable compositions has seemingly been identified. Additional insights are needed to fully characterize the feasible compositions in a subset of azeotropic mixtures. This article describes how sectional profiles can actually cross pinch‐point curves and generate a region of additional feasibility outside the one previously reported. It also demonstrates how a substantially larger region between the distillation line and pinch‐point curve after the intersection is only accessible by composition profiles going through the extended region. This extended reachable region is explained by evaluating the conditions for a fixed point in composition space. The effect on sectional profiles is illustrated for both an artificially parametric VLE manifold and a nonideal azeotropic system with more than one simple distillation region. Sectional profiles extended beyond the traditional bounds affect coupled sections in a distillation cascade.
Modeling of fouling on packings in absorption columns
Authors: Heberle Arthur , Schaber Karlheinz 
Published: April 2004

AbstractA model describing the fouling in irrigated columns with random packings was applied successfully to the description of the increase in pressure drop when fouling occurs during the absorption of CO2 in a suspension of Ca(OH)2. It is based on the Darcy–Weisbach law and the channel model. A mass balance around a fouling layer on the packings leads to a time‐dependent equation including the hydraulic radius from the channel model. A removal term is introduced in the fouling model. To approach the experimental results, the removal term had to be extended by an empirical parameter. It can be interpreted as a removal efficiency factor and is obtained by easy numerical fitting.
Free‐surface turbulence and mass transfer in a channel flow
Authors: Tamburrino Aldo , Gulliver John S. 
Published: April 2004

AbstractFree‐surface turbulence in a fully developed, open‐channel flow was measured for Reynolds numbers of 8,500–45,000. An analysis method of the 2‐D divergence on the free surface has been developed to extract Hanratty's β values, or the velocity gradient into the free surface, from these measurements. Hanratty's β is the parameter that relates most directly to the turbulence effect on the liquid‐film coefficient. Its measurement is a direct measurement of surface renewal. The spatial scales of β were 3 to 5 times smaller than those of the large upwelling events (boils) normally identified as surface renewal. The hypothesis is that the large upwelling events do not have the high‐vorticity gradients associated with large β values. Instead, the locations of high‐vorticity gradients on the free surface will also create the divergence required for high β values, occurring at the edges of a large upwelling event. Because the β frequency spectrum has properties to characterize the liquid‐film coefficient, it was normalized to be determined from its maximum value, the wave number of this maximum value, and a shape factor used to scale the frequency. Measurements of the liquid‐film coefficient from prior studies were also used to characterize the liquid‐film coefficient by measured β values for this nonsheared surface. The larger β scales predominantly influence the liquid‐film coefficient, in contrast to a previous study of a shear‐free surface published by McCready et al. in 1986, where all β frequencies were equally important. Generally, higher frequency turbulence is more significant at a sheared water surface than at a water surface with minimal shear stress.
Experimental validation of 3‐D lagrangian VOF model: Bubble shape and rise velocity
Authors: van Wachem B. G. M. , Schouten J. C. 
Published: April 2004

AbstractA novel 3‐D computational fluid dynamics model using an advanced Lagrangian interface tracking scheme was studied to find the time‐dependent behavior of gas bubbles rising in an initially quiescent liquid. A novel least‐square approach is used to determine the normal behavior at the interface for an accurate reconstruction and advection of the interface based on mollification of the color function by convolution. The incompressible Navier–Stokes equations are solved using an accurate discretization scheme to obtain the flow field of the gas and liquid phase. Detailed experiments of single rising bubbles of different sizes were performed to compare the shape, rise velocity and pressure signal of the bubble with the performed simulations. The developed Lagrangian volume‐of‐fluid model could accurately track the motion and shape of the gas–liquid interface embedded in a flow field with significant vorticity.
Standing‐wave design of tandem SMB for linear multicomponent systems
Authors: Hritzko Benjamin J. , Xie Yi , Wooley Robert J. , Wang Nien‐Hwa L. 
Published: April 2004

AbstractThe standing‐wave design was extended to achieve any desired split of mixtures containing three or more components in a single‐ring and a tandem two‐ring simulated moving bed (SMB). Mass‐transfer effects were considered in the design for nonideal systems. The separation of a four‐component mixture of glucose, xylose, acetic acid and sulfuric acid was chosen to illustrate the design method. Rate‐model simulations confirmed that the standing‐wave design method could guarantee high purity and high yield. If all the components in a ternary mixture need to be recovered with high purity and high yield, the easier separation should be performed in the first ring of a tandem SMB to achieve the lowest desorbent consumption and the highest product concentration. If only the intermediate component needs to be recovered in high purity, one of the impurities should be allowed to distribute between the two product ports in the first ring to achieve a lower desorbent consumption and a higher product concentration. These strategies also apply to the separation of a mixture containing more than three components.
Optimization of multiple‐fraction batch distillation with recycled waste cuts
Authors: Diehl Moritz , Schäfer Andreas , Bock Hans Georg , Schlöder Johannes P. , Leineweber Daniel B. 
Published: April 2004

AbstractA strategy for the optimal operation of multiple‐fraction batch distillation processes with waste cut recycling is presented. The processes are modeled by differential algebraic equations formulated in the gPROMS modeling language. A cost function based on economic criteria is developed. Recycling of the waste cuts is formulated as a cyclically repeated batch distillation process, where the waste cuts are recycled at intermediate points in time. The resulting multipoint boundary value optimization problem is efficiently solved by using the dynamic optimization package MUSCOD‐II. A comparison of optimization results for the separation of a ternary mixture shows that considerable gains in profits can be obtained by a complete recycling of the waste cuts. Computation times are in the range of minutes on a standard workstation.
Uncertainty considerations for describing complex reaction systems
Authors: Balakrishnan S. , Georgopoulos P. , Banerjee I. , Ierapetritou M. 
Published: April 2004

AbstractModels that accurately describe chemical processes are often intricate involving numerous reacting species and reaction steps. For complex reaction mechanisms, output‐species concentration profiles can change dramatically based on the set of values chosen for inputs if they are nondeterministic. A systematic uncertainty analysis can provide insight into the level of confidence of model estimates and aid mechanism reduction. Response surface methods and variants, thereof, require much fewer simulations for the adequate estimation of system uncertainty characteristics. This article focuses on reaction rate constant uncertainty using the stochastic response surface method (SRSM), whereby, uncertain outputs are expressed in terms of a polynomial chaos expansion of Hermite polynomials and engenders such useful properties as the mean and variance and computation of sensitivity information. SRSM determines the uncertainty propagation characteristics very accurately, while using an order‐of‐magnitude fewer model simulations than traditional Monte Carlo techniques. Since uncertainty in kinetic rate parameters largely affects the reduction of kinetic models, a framework of analysis is also developed for mechanism reduction considering uncertainty using sensitivity information from SRSM to create good initial sets of reactions for the efficient solution of a multiperiod optimization problem. Two case studies—an isothermal supercritical wet oxidation process and a nonisothermal H2/CO/air combustion process—elucidate the application of this framework of analysis to complex kinetic mechanisms and illustrate the possible ease of computational burden associated with mechanism reduction under uncertainty.
Mechanistic understanding of degradation in bioerodible polymers for drug delivery
Authors: Larobina Domenico , Mensitieri Giuseppe , Kipper Matt J. , Narasimhan Balaji 
Published: April 2004

AbstractA new model was developed to understand the mechanism of erosion in bioerodible polymers, which is essential to accurately predict drug release and precisely design controlled release devices. This model takes into account the phenomenon of microphase separation observed for polyanhydrides of certain copolymer compositions, and assumes that erosion is dominated by degradation and, thus, in a system with a fast eroding and a slow eroding species, two rate constants—one for each species—essentially control the evolution of the polymer microstructure. Expressions were derived for the fraction of each monomer released, as well as for the porosity in the system. A partition coefficient accounts for thermodynamic partitioning of a drug into the microdomains. The solutions of the model equations were fitted to experimental data on monomer release kinetics from two polyanhydride systems to obtain the erosion rate constants. Drug release kinetics experiments are compared to the model solution for drug release, and the partition coefficient of the drug is obtained from the fits. The comparisons to the data are promising, while pointing out the limitations of the model. The model does not account for oligomer formation prior to monomer release or for the dependence of the rate constants on parameters such as the degree of crystallinity, the local pH, and the polymer molecular weight.