bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous, random oscillations in the rate of CO oxidation over Pt/Alumina
Authors: Chakrabarty T. , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractThis note reports a study of the effect of inert diluents alone or in mixtures on the well known spontaneous oscillations in CO oxidation over a Pt catalyst. Irregular oscillations were observed with a nitrogen diluent but not when this diluent was replaced by argon. Adding SF6 at levels above 3.3% to argon induced oscillations, but when a similar level of CO2 or H2O was added to the argon diluent, oscillations were not found. Oscillations were observed only at the feed composition where one of the bifurcated steady states vanished.
Flow in the annulus of a bed of fine particles spouted with water
Authors: Kim Seung Jai , Littman Howard 
Published: March 2009

AbstractThe flow in the annulus of a water spouted bed of glass particles (275 to 774 μm) was studied experimentally in a cylindrical half‐column 50.8 mm in diameter.An axisymmetric model, which assumes Darcy flow in the annulus and uses the experimental spout pressure distribution, predicts the flow and pressure fields in the annulus. The substantial differences between this flowfield and that for coarse particle beds that are observed are caused by differences in the normalized interfacial pressure profile.The model predicts that both the fluid velocity and the normalized fluid velocity at the top of the annulus decrease as the particle size and bed height are reduced. Particles are observed to enter the spout primarily near the spout inlet in agreement with predictions of the axial spout voidage distribution.The residence time distribution of the fluid in the annulus is relatively broad and the measured residence times are about 25% higher than those calculated.
The onset of slugging in horizontal condensers
Authors: Rashwan F. A. , Soliman H. M. 
Published: March 2009

AbstractA mechanism is proposed suggesting that the wavy‐slug transition during horizontal condensation is initiated by a hydraulic jump. Based on this mechanism, a simple empirical correlation is developed and shown to be consistent in magnitude and trend with data for different fluids and different tube diameters. Further, a theoretical model is constructed for stratified two‐phase flow near the end of the condensation path utilizing the principles of mass, momentum and energy conservation. Results from the model together with the proposed slugging mechanism succeeded in defining a theoretical wavy‐slug transition line which agrees well with experimental flow regime data for a wide range of operating conditions.
Recent developments in packed columns
Authors: Kunesh J. G. 
Published: March 2009

AbstractHighlights of a recently concluded four year experimental program on random packings are presented. They include (a) a revised definition of loading to achieve better reproducibility; (b) discussion of the erratic behavior near the “flood” point which helps explain the scatter in the published “flood” data; (c) new data showing that with proper distribution, efficiency is stable over a broad range; and (d) controlled maldistribution studies leading to guidelines for distributor design, fabrication and installation. The need to precisely define commonly used terms is emphasized.
Adsorption‐desorption studies on the radium‐silica system
Authors: Nirdosh I. , Trembley W. B. , Muthuswami S. V. , Johnson C. R. 
Published: March 2009

AbstractAdsorption of radium‐226 on quartz is investigated. Adsorption isotherms are obtained for crystalline and sulphuric and hydrochloric acid‐treated quartz samples at pH 1 and 10. Desorption of radium‐226 from silica with EDTA and an EDTA‐KC1 mixture is also studied. It is found that radium‐226 adsorbed on silica is difficult to desorb whereas radium deposited on silica as radium sulphate is easily removed in EDTA solutions.
Particle transport in fouling caused by kaolin‐water suspensions on copper tubes
Authors: Melo L. F. , Pinheiro J. D. 
Published: March 2009

AbstractParticulate fouling tests were carried out using kaolin‐water suspensions flowing through an annular heat exchanger with a copper inner tube. The flow rate was changed from test to test, but the fluid temperature and pH, as well as the particle concentration, were maintained constant.In the lower range of fluid velocities (<0.5 m/s), the deposition process seemed to be controlled by mass transfer. The corresponding experimental transport fluxes were compared to the predictions obtained with several models, showing that diffusion governed particle transport. The absolute values of the mass transfer fluxes and their dependences on the Reynolds number were satisfactorily predicted by some of the models.
Attrition of spherical electrode carbon particles during batch fluidized combustion
Authors: Halder P. K. , Salatino P. , Arena U. 
Published: March 2009

AbstractSpherical electrode carbon particles prepared from carbon rods of dry cell batteries have been used to study the attrition behaviour in a bubbling fluidized bed combustor. Experiments have been conducted in a 40 mm I.D. and 1 m high fluidized bed combustor operated at 1 m/s superficial velocity. The bed was operated with nitrogen and with two different oxygen concentrations at 850°C to study the effect of combustion on attrition of these particles. The experimental technique used allowed the time resolution of attrited fines generation, providing detailed curves of attrition rates as a function of time. Attrition rate constants have been evaluated. Results show an enhancement of attrition due to combustion even for spherical, homogeneous and smooth particles.
Dehydration of 1‐phenylethanol over solid acidic catalysts
Authors: Takahashi Takeshige , Kai Takami , Tashiro Masashi 
Published: March 2009

AbstractDehydration of 1‐phenylethanol has been carried out over a solid acidic catalyst in order to examine the effect of the concentration of effective acid sites on the reaction rate, styrene selectivity and catalyst fouling. The reaction rate increased with the concentration of effective acid sites, while styrene selectivity decreased. The catalyst deactivation depended upon the concentration of the effective acid sites and also the size of the micro pores in the catalyst. Taking into account the reaction rate and selectivity, ALO‐4 alumina was the most suitable catalyst for the present reaction. An activation energy for the dehydration over ALO‐4 alumina was 83.8 kJ mol−1. The dehydration reaction could be a useful tool for the characterization of the nature of the acid sites.
A pyrolysis process for tar sands
Authors: Lechner C. A. , Liapis A. I. , Findley M. E. 
Published: March 2009

AbstractA thermal processing system for tar sands is developed and analyzed. Based on the Utah tar sands studied, the process is found to be operable using combustion of coke and unconverted bitumen as the energy source. It is estimated that about 80% of the spent sand is required to be recycled to the pyrolyzer to provide this energy source.The volumes for the pyrolyzer and kiln are calculated for appropriate descriptions of tar sand characteristics, and the kiln volume is found to be particularly sensitive to the choices of temperature, air supply, and particle size.
Studies on the inhomogeneous nature of the silent discharge reactor: Part 1. Experimental investigations
Authors: Khan A. A. 
Published: March 2009

AbstractCommercial application of the silent discharge reactor is confined to its use for the manufacture of ozone. Free electron concentration in the reaction space is determined by the occurrence of electron avalanches between the dielectrics and generation of transient primary reaction zones (PRZ) where the electron –‐ molecule collision reactions take place. Experimental studies have been carried out in order to increase the frequency of occurrence of PRZs as well as to enhance the mean electron energy within an individual avalanche. The dielectric surface has been treated with P.T.F.E. to reduce the recombination rate of O‐atoms. Results indicated that both methods of modifying the current pulse train have influenced the pattern of utilization of electrical energy. Similarly a P.T.F.E. coated dielectric has been found to be more efficient than an ordinary glass dielectric.
A new approach to jet phenomena gas entrainment and recirculation in a bidimensional spouted fluidized bed
Authors: Freychet N. , Briens C. L. , Bergougnou M. A. , Large J. F. 
Published: March 2009

AbstractAlthough gas jets injected into fluid beds fluctuate, previous models assumed that they were steady. A new model separates the bed in a zone in which the jet is never present and a zone in which the jet fluctuates (a point in this zone will alternately be in the jet and in the emulsion phase). Its predictions matched the rate of gas entrainment into the jet and the rate of gas recirculation between emulsion and jet which were observed in a large 2 dimensional bed equipped with a “V” grid and a central jet.
Multiplicity in the partial oxidation of propylene over a copper‐molybdena catalyst
Authors: Labastida‐Bardales J. R. , Hudgins R. R. , Silveston P. L. 
Published: March 2009

AbstractMeasurement of rates of formation of acrolein and acetaldehyde in the partial oxidation of propylene over a copper molybdate catalyst were made under steady‐state and transient modes. These measurements disclosed a rate of product formation multiplicity apparently attributable to the oxidation state of the catalyst and not to surface phenomena usually thought to be the source of hysteresis in catalytic systems.
A nonlinear pi(d) controller
Authors: Jutan Arthur 
Published: March 2009

AbstractThe PID control algorithm remains the most widely used in the process industries. This is due to its simplicity (three tuning parameters, fixed structure) and its ability to satisfy the majority of process control needs. Here, a new nonlinear algorithm (the PI(D)) is presented, which maintains the simplicity of the PID, but is nevertheless able to outperform it in both load and set point changes. Tuning formulae and response curves for the PI(D) controller are presented.
Quench time modeling in propane ultrapyrolysis
Authors: Nighswander John A. , Huntrods Richard S. , Mehrotra Anil K. , Behie Leo A. 
Published: March 2009

AbstractPyrolysis products from industrial cracking furnaces are commonly quenched indirectly in transfer line heat exchangers (TLX). To assess the performance of a TLX for a high severity furnace, a rigorous computer simulation of a TLX tube has been developed. The primary objective was to determine whether this method of indirect quenching can provide the extremely small quench times required for fast ultrapyrolysis reactions. Results indicate that extremely small quench times of approximately 10–15 ms can be achieved, typically dropping the temperature from 1100 to 900K. The model takes into account the effect of the thermal entrance region on heat transfer characteristics and can employ either a 10 equation molecular reaction scheme or an 80 equation radical reaction scheme for propane pyrolysis. The effects of adjusting the main process variables and of coke deposition on quenching performance are also discussed.
The effects of surface active agents on jet breakup in liquid‐liquid systems
Authors: Skelland A. H. P. , Walker Perry G. 
Published: March 2009

AbstractAn experimental study has been made of the effects of anionic, cationic and nonionic surface active agents on jet length, jet contraction and drop size resulting from the formation and breakup of liquid jets in another immiscible liquid, while undergoing mass transfer.Correlations previously established for uncontaminated systems with various rates of mass transfer successfully fitted the present data, when used with the diminished value of interfacial tension caused by the surfactant. Variables included nozzle size, flow rate, and type and concentration of surfactant. Data were obtained from measurements on over 3,000 drops, plus jet lengths and jet diameters from 501 photographs.
Minimum tank volumes for CFST bioreactors in series
Authors: Hill Gordon A. , Robinson Campbell W. 
Published: March 2009

AbstractThe primary reactor type currently used in the production of microorganisms or microbial products is the stirred tank reactor (STR). If operated on a continuous flow basis (CFSTR) they become similar in performance to the primary reactor configuration used in most of the chemical industry.In this work, microbial kinetics are considered in the design of CFSTRs in series. An equation is derived to predict the minimum possible total residence time to achieve any desired substrate conversion. The equation permits the use of a wide variety of growth kinetic models and is applied here to Monod, substrate inhibition and product inhibition cases. For the majority of cases, it is found that three optimally designed CFSTRs in series provide close to the minimum possible residence time for any desired substrate conversion.A comparison to the use of a PFR is made for cases of both no‐recycle and biomass recycle to the CFSTR train. It is found that three CFSTRs, which are not equi‐volume, provide the same required total mean residence time as a PFR for Monod kinetics, but are significantly superior (i.e., less total volume required) to a PFR for substrate‐inhibited growth.
Letter to the editor: Re: Can. J. Chem. Eng. 66, No. 4, 703; Book Reviews. Editor, Can. J. Chem. Eng.
Authors: Habashi F. 
Published: March 2009

AbstractRe: Can. J. Chem. Eng. 66, No. 4, 703; Book Reviews. Editor, Can. J. Chem. Eng.
Explicit forms for the calculation of heat and momentum transfer coefficients for vapour condensation on surfaces of various forms
Authors: de Souza‐Santos Marcio L. 
Published: March 2009

AbstractA relatively simple method to calculate the heat and momentum transfer coefficients for the laminar condensation of pure vapours on surfaces of various forms is presented.It can be applied generally to surfaces having a variety of geometrical forms. Examples of such applications are presented for the cases of: plane and exponential curved plate profiles, horizontal cylinders, sinusoidal plates and rotating discs and cones.The mathematical treatment leads to explicit expressions for the parameters of the process, among them the heat transfer coefficients. It considers the effects of film acceleration and energy convection.It must be stressed that the method is not intended to bring more precision than existing methods which take into account the mentioned effects, but is proposed as a generalized procedure for geometrical surface forms and also to speed the calculations for complicated condensation surface geometries. A guide for equipment designers is also provided.
Control of crystal size distribution in a batch cooling crystallizer
Authors: Rohani Sohrab , Tavare N. S. , Garside John 
Published: March 2009

AbstractA control scheme for crystal size distribution (CSD) in a batch crystallizer, based on indirect measurement of fines suspension density and manipulation of fines dissolving rate, is proposed and implemented on a 27 L laboratory batch cooling crystallizer using the potash alum‐water system. The measured variable was a temperature difference related to the fines suspension density detected by a new fines sampling/suspension density measuring device proposed by Rohani and Paine (1987). Servo‐control of the fines suspension density was achieved using a conventional PI control mode. Two different cooling policies, namely, linear cooling and isothermal operation were examined and improvement in the final CSD was observed in both cases. The weight‐mean crystal size and the coefficient of variation of the end product showed a maximum improvement (larger mean size and smaller coefficient of variation) of 80% and 31% over the uncontrolled experiments, respectively. The weight fraction of fines (smaller than 150 μm) in the end product was decreased by a maximum of 99% over the uncontrolled run. Higher overall rates of fines dissolution led to a more uniform product with a larger weight‐mean crystal size at the expense of a small reduction in the rate of solids make.
The effect of the level of micromixing on the optimal design of cstr's performing michaëlis‐menten reactions
Authors: Malcata F. Xavier 
Published: March 2009

AbstractAn analytical formula for the calculation of the substrate conversion under complete segregation conditions in a CSTR performing a biochemical reaction following Michaëlis‐Menten kinetics is obtained. The errors on the expected conversion arising from using an optimal reactor design based on the assumption of complete micromixing conditions are discussed. Methods for the determination of the optimal reactor size profile for a series of CSTR's under complete segregation conditions are reported, using the minimum of the overall space time as the objective function.
Scale‐up of liquid‐liquid dispersions in stirred tanks
Authors: Okufi S. , De Ortiz E. S. Perez , Sawistowski H. 
Published: March 2009

AbstractA study of local drop size, drop size distribution and holdup fraction was conducted for liquid‐liquid dispersions in three geometrically similar stirred tanks of standard configuration over a range of stirrer speeds and dispersed phase volume fractions. The tanks had diameter ratios 1:2:4, the smallest diameter being 11 cm. Two liquid‐liquid systems were used: n‐heptane‐water and n‐heptane containing different concentrations of di‐(2‐ethylhexyl) phosphoric acid dispersed in an aqueous sulphate solution. No significant local variations of the three parameters investigated were observed at constant stirrer speed and constant dispersed phase volume fraction. Measurements in the three tanks indicated that the rule of equal impeller tip speed provides the best scale‐up criterion for equal interfacial areas per unit volume of dispersion. A correlation was also proposed for the Sauter mean diameter.
The effect of the droplet volume and hydrocarbon chain length on the detachment force in the sulphur/hydrocarbon drop/sulphur system
Authors: Bialopiotrowicz Tomasz , Janczuk Bronislaw 
Published: March 2009

AbstractUsing a device constructed in our laboratory, measurements of the detachment force of a small sulphur plate from hydrocarbon drops of various volumes located on a large sulphur plate were carried out. Eleven aliphatic hydrocarbons in the series from n‐hexane to n‐hexadecane were used. Using the literature data for hydrocarbon‐water interfacial tensions and the contact angles for the system sulphur/hydrocarbon drop/water, the detachment force was also calculated from the Laplace equation. On the basis of the measured results it was found that the detachment force depends on the hydrocarbon drop volume and the type of hydrocarbon and that in the many cases there is a good agreement between the measured and calculated values of the detachment force. It was also found that there is a stepwise relationship between the detachment force and the number of carbon atoms in the hydrocarbon molecule.
Removal of fine particles from aqueous medium by flotation: Sodium dodecylbenzenesulfonate‐barium sulfate system
Authors: Kubota Katsuyuki , Harima Toshihiro , Hayashi Shinya 
Published: March 2009

AbstractInsoluble barium sulfate particles were removed from water by a batch flotation technique using an anionic surfactant as a frother and collector. The measured particle concentrations are presented as a function of the elapsed time and compared with values predicted by a simple hydrodynamic collision model. The model predictions were in reasonable qualitative agreement with the experimental results. However, the attachment efficiency observed was found to be much smaller than unity, suggesting that an electrical repulsive force may affect the flotability. Accordingly, electrical mobilities for the air bubbles and the particles were measured by the electrophoresis method, and the energy barrier between the particles and the bubble surfaces was found to be relatively large.
Structure des écoulements dans une cuve à fond bombé agitée par une turbine de rushton
Authors: Magni F. , Costes J. , Bertrand J. , Couderc J. P. 
Published: March 2009

AbstractLa structure des écoulements générés par une turbine de Rushton est étudiée dans une cuve chicanée à fond bombé. contenant un volume d'eau de 50 litres. La technique de mesure utilisée est la vélocimétrie Doppler à laser.Pour une vitesse de rotation de 65 tours par minute, les composantes radiale, tangentielle et axiale de la vitesse moyenne et de la moyenne quadratique des fluctuations de vitesse ont été déterminées en divers points du plan médian entre deux chicanes et dans deux plans verticaux voisins des chicanes. Les débits de circulation radiale, axiale et tangentiellc ont été calculés.L'ensemble de ces résultats a permis de determiner trés finement les caractéristiques des écoulements moyen et fluctuant dans tout le volume de la cuve et de précker les influences des chicanes et du fond bombé.
Investigation of interfacial area and void fraction in upward, cocurrent gas‐liquid flow
Authors: Dejesus J. M. , Kawaji M. 
Published: March 2009

AbstractInterfacial area was measured in cocurrent, gas‐liquid upward flow through a vertical, 2.54 cm I.D. and 2.67 m long tube by absorption of CO2 diluted in air into aqueous sodium hydroxide solution. Void fraction and pressure drop were also measured for superficial liquid velocities up to 1.3 m/s. Although the interfacial area exhibited a maximum and minimum with increasing superficial gas velocities at relatively high liquid flow rates as in previous experiments, several significant differences were found. Since the dissipation parameters proposed in the past to correlate interfacial area were found to be less than satisfactory, a new empirical relation is proposed, which can correlate most of the present data within ± 20%.
Performance of thermal energy storage unit using CaCl2‐NH3 system mixed with Ti
Authors: Yamamoto Hideki , Sanga Seiji , Tokunaga Junji , Sakamoto Yuuki 
Published: March 2009

AbstractIn order to develop an energy storage system using the reaction of solid CaCl2 with ammonia gas, various properties such as volume expansion of CaCl2 with ammoniation, activity of the chemical reaction for repeated cycles and influence of a metal additive on the heat transfer rate of the ammoniated salt were studied experimentally. The maximum volume after the reaction was 14–16 times of the ideal volume of CaCl2. No deactivation was observed on repeated cycles. The heat transfer rate of ammoniated salts (CaCl2 · nNH3) was improved by adding the metal, titanium. The time required for ammoniation of CaCl2 mixed with Ti was 10–30% shorter than for CaCl2 alone. Similar results were obtained by repeating the cycles of ammoniation and deammoniation.
Types of dispersion in agitated liquid‐liquid systems
Authors: Kato Satoru , Nakayama Eiichi , Kawasaki Junjiro 
Published: March 2009

AbstractThis paper describes phase inversion phenomena in stirred vessels. In particular, the effects of mechanical operating‐parameters on dispersion types were investigated. It was found that when the impeller stirring speed was lower than 400 rpm, the aqueous phase became continuous, while when it was higher than 1050 rpm, the phase which had the higher viscosity became dispersed. Surface active agents have strong effects on phase inversion phenomena.
Gas liquid contacting in reciprocating plate columns: I. hydrodynamics
Authors: Gomaa H. G. , Landau J. , Al Taweel A. M. 
Published: March 2009

AbstractThe hydrodynamic characteristics of a 10‐cm reciprocating plate column used for counter‐current gas‐liquid contacting was investigated. The values of gas holdup, interfacial area and maximum throughputs achievable in this unit put it in a favourable position in comparison with other types of contactors.