bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dehydration of sodium carbonate decahydrate to monohydrate in a fluidized bed
Authors: Hartman M. , Veselý V. , Svoboda K. , Trnka O. , Beran Z. 
Published: April 2004

AbstractKinetics of the thermal dehydration of sodium carbonate decahydrate to monohydrate is investigated at temperatures between 15 and 30°C in a batch, fluidized‐bed, 140‐mm‐ID reactor. Effects of particle size, mass of bed, and gas velocity on the dehydration rate are also explored. A simple correlation based on the collected experimental data is developed. The proposed rate law formula makes it possible to estimate the dehydration rate that would be needed to design the performance of a fluidized‐bed drying unit. The produced monohydrate is subjected to textural analysis, and pore volume and surface‐area data are presented.
Mathematical model for the nonsteady decomposition of intumescent coatings
Authors: Di Blasi Colomba , Branca Carmen 
Published: April 2004

AbstractA 1‐D transient mathematical model was studied for a composite system consisting of a substrate (steel) and an intumescent coating exposed to radiative heating. By applying a simple heat conduction equation for the first material, a general model proposes the coating consisting of three components, which degrade according to independent finite‐rate reactions. Mass and heat transfer take place across a variable volume medium, including a simplified mechanism for bubble dynamics and material swelling. A parametric analysis clarifies the role of several parameters on the fire retardancy performance of the coating. Good agreement is obtained between predictions and measurements of the substrate temperature profiles.
Prediction of phase equilibria for binary mixtures by molecular modeling
Authors: Fermeglia Maurizio , Pricl Sabrina 
Published: April 2004

AbstractTwo new procedures based on quantum/COSMO calculations and on molecular mechanics/dynamics simulations, respectively, for estimating the PHSCT EOS parameters and to predict VLE behavior for binary mixtures are presented. The quality of the predictions achieved with both methods, in conjunction with the confined computational time aspects involved, can be considered satisfactory so that these strategies can be judged as promising routes toward an on‐line coupling between molecular and process simulation.
Internal annular wall jets: Radial flow in a stirred tank
Authors: Kresta Suzanne M. , Bittorf Kevin J. , Wilson David J. 
Published: April 2004

AbstractSimilarity solutions are derived for internal annular wall jets and compared with experimentally determined velocity profiles at the wall of a stirred tank with radial flow. The first similarity solution considers a geometry where the thickness of the wall jet is small relative to the diameter of the cylinder and the fluid flows relative to a free stream velocity of zero. In the second solution, the free stream velocity opposes the direction of the jet flow, as is observed in the recirculating flow in a stirred tank. The internal annular wall jet model agrees very well with the flow at the wall of a stirred tank agitated with a Rushton turbine. The free stream counter flow is driven by the wall jet, and a single velocity and length scale define the self‐similar velocity profiles for the flow in the jet and in the recirculating flow. Both the analytical model and experimentally observed expansion rates are linear and the maximum velocity in the jet decays as [U ∝ (z/T)−0.5], where (z/T) is the dimensionless streamwise distance. This decay can be contrasted with the faster decay [U ∝ (z/T)−1] observed in the 3‐D wall jets produced by axial impellers. These results provide a basis for validating computational fluid dynamic simulations in stirred tanks and for estimating the largest length scales of turbulence in the bulk of the tank.
Synthesis of ZnO particles in a quench‐cooled flame reactor
Authors: Hansen Jens P. , Jensen Joakim R. , Livbjerg Hans , Johannessen Tue 
Published: April 2004

AbstractThe quench cooling of a flame by injection of cold air was studied in a flame reactor for the formation of ZnO particles in a premixed flame with a precursor jet. A rapid temperature drop downstream from the temperature peak is advantageous for the attainment of a large specific surface area. Computational fluid dynamics simulations were used to design a quench ring with nozzles directed slightly upward and at a small tangential angle from the direct line to the center. This novel design avoids distortion of the flow pattern below the quenching plane and effectively cools the flame immediately above. At the highest tested production rate, the specific surface area of the ZnO particles increases from 20 to 60 m2/g when quenching is employed. The particles are characterized by BET surface area measurements, TEM images, and the size distributions of particle aggregates are measured by a scanning mobility particle sizer.
Influence of functional group on the electrification of organic pigments
Authors: Tanoue Ken‐ichiro , Morita Kenshi , Maruyama Hiroyuki , Masuda Hiroaki 
Published: April 2004

AbstractElectrification of phthalocyaninatocopper derivative‐powders was investigated based on the measurement of contact potential difference (CPD) between the powder and reference gold electrode. The powder‐introduced halogen substituents in the end group show negative CPD values. The value of CPD increases negatively as the number of chlorine substituents increases, while the value increases negatively as the number of bromine substituents increases. Powders having hydrogens in the end groups are initially positively electrified and tend to their respective CPD values as time elapses, while powders fully substituted by halogens are negatively electrified. It is found that the charge decay data are well represented by a sum of two exponential functions. Charge‐decay speed depends greatly on the number of substituents. Molecular orbital calculation has showed that the measured contact potential difference changes linearly with the calculated Fermi level.
Numerical scale‐up study for orthokinetic agglomeration in stirred vessels
Authors: Hollander E. D. , Derksen J. J. , Portela L. M. , Van den Akker H. E. A. 
Published: April 2004

AbstractScale‐up of orthokinetic agglomeration in stirred‐tank reactors was studied numerically. A computer code based on the lattice‐Boltzmann method was used to perform large eddy simulations. To account for the dependence of agglomeration on hydrodynamics, the kinetic relation proposed by Mumtaz et al. was applied locally. The convection‐reaction equation governing the evolution of the particle‐number concentration was solved at the same resolution as the flow field. Three scale‐up rules were studied: scale‐up at constant Re‐number, constant specific power input, and constant impeller tip speed. Vessel sizes varying from 1 to 10,000 L were simulated. The use of two types of impellers (Rushton turbine and Pitched Blade turbine) allowed for investigating the dependence of agglomeration on the macroscopic flow pattern in a reactor. Inhomogeneities in stirred‐tank flow caused unpredictable scale‐up behavior. Scale‐up at constant power input yielded the most constant reactor performance. Impeller geometry had a drastic impact on the observed agglomeration rate, even if the difference in Po number was taken into account.
Advantages and risks in increasing cyclone separator length
Authors: Hoffmann A. C. , de Groot M. , Peng W. , Dries H. W. A. , Kater J. 
Published: April 2004

AbstractThe effect of cyclone length on separation efficiency and pressure drop has been investigated experimentally and theoretically by varying the length of the cylindrical segment of a cylinder‐on‐cone cyclone. Experimental results based on cyclone lengths from 2.65 to 6.15 cyclone diameters showed a marked improvement in cyclone performance with increasing length up to 5.5 cyclone diameters; beyond this length the separation efficiency was dramatically reduced. Experimental data agreed well with the predictions of a range of models and CFD simulations. This helps to assess the benefit of prolonging a given cyclone. The physical mechanisms behind the observed trends are elucidated. The dramatic fall in separation performance for the longest length was caused by the “natural turning” phenomenon.
Dynamics of molecular weight distributions for polymer scission
Authors: Mehta Khamir , Madras Giridhar 
Published: April 2004

AbstractThe dynamics of molecular weight distributions (MWDs) for polymer degradation is of interest to various applications. The time evolutions of MWDs can be determined by solving the governing population balance equations, which are generally solved by moment techniques wherein the initial distribution is represented by a gamma distribution. The evolution of MWD is determined by the time dependence of the gamma distribution parameters. The population balance equations (PBEs) can also be solved numerically by converting them to partial differential equations (PDEs). The degradation rate coefficient in the PBE depends on the molecular weight x as (x − xo)λ or as a quadratic polynomial in x. The solutions obtained with the moment technique, which are inaccurate for certain cases, are compared with the solutions determined by solving the PDEs. The utility of the numerical scheme is also discussed for cases where the initial distribution cannot be represented satisfactorily by a gamma distribution.
Removal of surface adhered particles by surfactants and fluid motions
Authors: Batra Ashish , Paria Santanu , Manohar C. , Khilar Kartic C. 
Published: April 2004

AbstractRemoving or detaching particles from a surface is of interest in filter bed regeneration, cleaning of semiconductor surfaces, migration of fines in underground reservoirs, and detergency. A two‐stage removal process proposed involves penetration of the surfactant solution, diffusion and adsorption of surfactant molecules, followed by the particle removal by hydrodynamic force. The particle‐substrate system, considered here as a plate‐plate system, takes into account the surface roughness of the substrate in the form of asperities. The concept of critical hydrodynamic force required to remove or detach a particle adhering to a substrate in the presence of surfactant solution is discussed, as well as its calculation of typical values. The critical hydrodynamic force depends on the surface roughness, particle size, and other parameters of the system. When asperity size is comparable to the equilibrium distance of separation, the critical hydrodynamic force becomes very large in magnitude, indicating that particle removal is very difficult. Higher critical hydrodynamic force is required for the removal of particles of small size.
Prediction of the density for natural gas and liquefied natural gas mixtures
Authors: Eslami Hossein 
Published: April 2004

AbstractExperimental liquid densities and compressibility factors of natural gas and liquefied natural gas mixtures were reproduced using an analytical equation of state, based on the statistical‐mechanical perturbation theory of Weeks, Chandler and Andersen. The temperature‐dependent parameters of the equation of state were calculated using our previous corresponding‐states correlation, based on the normal boiling point parameters. This article shows that the equation of state for multicomponent natural gas and liquefied natural gas mixtures would be predictable with minimal input information, namely the normal boiling temperature and the liquid density at the normal boiling point. The calculated results agreed well with the experiment. From a total of 590 data points for natural gases and 203 data points for liquefied natural gases examined in this work, the average absolute deviations were 0.33% and 2.48%, respectively, and the maximum deviations were 2.63% and 4.61%, respectively.
Segment‐based excess Gibbs energy model for aqueous organic electrolytes
Authors: Chen Chau‐Chyun , Bokis Costas P. , Mathias Paul 
Published: April 2004

AbstractThe aqueous electrolyte nonrandom two‐liquid (NRTL) model of Chen et al. is extended to represent the excess Gibbs energy of aqueous organic electrolytes. These organic electrolytes exhibit very different solution nonideality from typical aqueous electrolytes with elemental ions. The proposed extension is an integration of the electrolyte NRTL model for aqueous electrolytes and the polymer NRTL model (Chen, 1993) for oligomers and polymers. Organic ions are treated as oligomers that consist of hydrocarbon segments and ionic segments that each exhibit distinctive physical interactions with neighboring species. This integrated NRTL model captures the nonideal phase behavior of aqueous organic electrolytes, including micelle formation. The model further provides a versatile thermodynamic framework to correlate solution nonideality of electrolyte systems, organic or inorganic, and complex systems containing both electrolytes and polymers.
Control of vertical acceleration (effective gravity) between normal and microgravity
Authors: Wakayama Nobuko I. , Zhong Chengwen , Kiyoshi Tsukasa , Itoh Kikuo , Wada Hitoshi 
Published: April 2004

AbstractWhen an upward magnetization force Fm is imposed on a liquid, the force acting on the liquid is the difference between the gravitational and magnetization forces. Thus, the magnitude of vertical acceleration acting on the liquid can be varied from 1 g to 0 g by changing the upward Fm. To verify this vertical acceleration‐control method, behavior of bubbles formed by injecting gas from a nozzle was examined. By decreasing the magnitude of vertical acceleration, the number of bubbles formed per unit time decreased and their size increased. These results confirm that vertical acceleration can be changed from normal gravity to near‐zero gravity. The method to generate low‐gravity conditions will find many applications over a wide range of research.
Product‐oriented process synthesis and development: Creams and pastes
Authors: Wibowo Christianto , Ng Ka M. 
Published: April 2004

AbstractA systematic procedure is presented for the synthesis and development of manufacturing processes for creams and pastes. The procedure integrates the skills of a chemist and a chemical engineer to produce a product with specified properties. The desired functional and sensorial performance of the product is first identified in terms of quality factors. Then, the requisite ingredients are selected, and the process flowsheet, as well as the operating conditions, is synthesized. There are four steps in the procedure: identification of product quality factors, product formulation, flowsheet synthesis, and product and process evaluation. Design guidelines, as well as physical models describing relevant phenomena, are used to assist decision‐making at each step of the procedure.
Dynamic discharge and performance of a new adsorbent for natural gas storage
Authors: Biloe S. , Goetz V. , Mauran S. 
Published: April 2004

AbstractPerformance of a new highly conductive adsorbent matrix for ANG systems was evaluated. The adsorbent composite block (ACB) was a mixture of superactivated carbon, labeled MAXSORB and expanded natural graphite (ENG), followed by consolidation. ENG was used both as a very high conductive matrix and as support for adsorbents. Thermal conductivity is 30 times higher than that of activated carbon packed bed. Dynamic methane discharges were studied experimentally with a 2‐L vessel filled with ACB. The influence of both the discharge flow rate and heat‐exchange conditions at the reactor wall on the delivered methane capacity was investigated. The modeling of the discharge process, validated from experimental results, shows the efficiency of this ACB with a 100‐V/V delivered methane capacity under various working conditions.
Simultaneous adsorption of SO2NOx from flue gases in a riser configuration
Authors: Das Asit K. , De Wilde Juray , Heynderickx Geraldine J. , Marin Guy B. , Iversen Steen B. , Felsvang Karsten 
Published: April 2004

AbstractSimultaneous adsorption of SO2–NOx is a new, promising process in treating industrial flue gases in a short‐contact‐time dilute phase riser with Na/γ‐Al2O3 sorbent particles of 50–100 μm diameter at 370–430 K. A major part of the sorbent is recycled for maximum utilization of the sorbent capacity before regeneration. A steady‐state model for the riser adsorber is developed by combining independently determined rate equations with a 1‐D, two‐phase hydrodynamic model of the riser. The simulation was validated with the operating data from a pilot‐scale installation of 4.2 Nm3/s flue‐gas capacity and solid fluxes between 1 and 3 kg·m−2·s−1. The riser operates in an extremely dilute phase with a solid volume fraction below 7.0 × 10−4 and a slip velocity that is constant for almost the entire riser length, indicating fully developed flow. The experimental observation that an increase in the SO2–NO ratio in the feed gas leads to a higher NO removal efficiency is explained as resulting from an increased concentration of the adsorbed SO2. The SO2 removal efficiency, however, may drop if free adsorption sites are not sufficiently available. Recycling of the sorbent has only a marginal effect on the NO removal, but helps to maximize the SO2 adsorption. For the first time, the simultaneous removal of SO2 above 95% and of NOx above 80% is reported using a dry, regenerable sorbent in a riser reactor.
In situ infrared measurements on TiO2 flames: Gas and particle concentrations
Authors: Arabi‐Katbi Osama I. , Pratsinis Sotiris E. , Morrison Philip W. 
Published: April 2004

AbstractFourier transform infrared spectroscopy was performed on premixed flames of titanium tetraisopropoxide, methane and oxygen. A combination of emission/transmission (E/T) measurements yields gas temperature, gas concentrations, soot temperature, soot concentration and absorption features of TiO2 particles. To validate the temperature measurements, a thermocouple is inserted into the IR path within the flame, and its temperature is compared to the surface temperature from E/T analysis which agrees quite well. The HITEMP and HITRAN databases are used to determine the gas mol fractions in the flame. Soot is observed in the emission spectra of the flame, and its concentration decreases with its increasing position above the burner. The soot temperature is always less than the gas temperature. The IR feature of TiO2 particles is hard to observe, because it is very small relative to H2O and CO2 features. Interfering features, however, were removed using either calculated spectra or by experimentally generating a reference flame using an acetone–methane flame.
Shortcut experimental method for designing chiral SMB separations
Authors: Migliorini Cristiano , Mazzotti Marco , Zenoni Gianmarco , Morbidelli Massimo 
Published: April 2004

AbstractThe simulated moving‐bed (SMB) chromatographic separation of the Tröger's base enantiomers with ethanol as eluent on microcrystalline triacetate cellulose was studied. An experimental technique to design nonlinear SMB separations with few column experiments is presented. This shortcut technique allows the rigorous solution of the Equilibrium Theory model to be approximated without knowing the adsorption equilibria, and therefore can be useful in developing new separations. The predictions of the shortcut method are compared with the experimental results of the SMB separation. The effect of the feed concentration and of the nonideal contributions, such as mass‐transfer resistance and extracolumn band broadening, are elucidated.
Model for gas hydrate equilibria using a variable reference chemical potential: Part 1
Authors: Lee Sang‐Yong , Holder Gerald D. 
Published: April 2004

AbstractA new model developed for predicting the dissociation pressure of gas hydrates proposes that the host–host interaction can be affected by the guest molecules, thus requiring different values of the reference properties, Δμ and Δh, for each gas hydrate. We presume that the primary impact of the guest is to distort the lattice, although other factors, such as guest polarity, can have an impact. Experimentally based Δμ and Δh values for each gas hydrate show that these values vary from guest to guest, generally increasing with guest size. Using these experimentally determined reference values, the error between calculated and experimental dissociation pressures is reduced. A correlation between Δμ and the molecular size of the guest molecule (or the Kihara hard‐core diameter ‘a’) is also developed for estimating values of Δμ, where experimental data are absent (that is, methane in structure II hydrate with no other guests).
Investigation of postflooding conditions in countercurrent gas–liquid flow
Authors: Maharudrayya S. , Jayanti S. 
Published: April 2004

AbstractSystematic experiments were conducted to study the postflooding situation in air–water countercurrent flow in a tube of 0.025 m internal diameter with smooth inlet and outlet conditions for the two phases. The downflow rate of water and the pressure gradient were measured over a range of flow rates for test‐section lengths of 0.6, 1.2 and 2.0 m. Additional experiments were conducted with increasing and decreasing water flow rates at a constant air flow rate. The length of the test section or the way the flooding point was approached did not significantly affect the onset of flooding. The data show that, as the gas flow rate is increased, the pressure gradient can fall significantly in the postflooding situation due to depleting the downflow rate of liquid. Dimensionless correlations are proposed to calculate the downflow rate and the pressure gradient given for overall flow parameters.
Influence of sieve trays on the mass transfer of single drops
Authors: Henschke Martin , Pfennig Andreas 
Published: April 2004

AbstractMass transfer on single drops was studied experimentally in a conical glass test cell on a laboratory scale. To determine the influence of internals on the mass transfer, two different sieve trays with hole diameters of 3 and 6 mm, respectively, were inserted into the cell. In the experiments the resting times the drops stayed under and above a sieve tray were varied. Through the evaluation of the experimental results with a model, it is possible to determine the influences of the flow field and the sieve‐tray passage on mass transfer separately. The mixing inside the drops while they passed through the holes is relatively small even if the drops are a little larger than the hole diameter. The influence of changes of the flow field caused by the sieve trays on mass transfer is larger, and its quantitative magnitude depends on the system used.
Continuous protein recovery with a liquid–solid circulating fluidized‐bed ion exchanger
Authors: Lan Qingdao , Bassi Amarjeet S. , Zhu Jing‐Xu (Jesse) , Margaritis Argyrios 
Published: April 2004

AbstractA liquid–solid circulating fluidized‐bed (LSCFB) ion‐exchange system was developed for continuous protein recovery. It contains a downcomer for protein adsorption and a riser for protein desorption, with ion‐exchange particles circulating continuously between the two columns. Effects of the operating conditions on the hydrodynamics and the continuous ion exchange of bovine serum albumin (BSA) in the system were investigated. Under typical operating conditions, up to 98% BSA was adsorbed in the downcomer (showing a very high efficiency of protein removal from the feed), and an overall protein recovery of up to 84% was obtained in the LSCFB system, indicating that the LSCFB system was a very promising strategy for the continuous recovery of proteins.