bluuebunny/crossref_metadata_2025_split huggingface dataset:
A theory for effective solid stresses in the annulus of a spouted bed
Authors: McNab G. S. , Bridgwater J. 
Published: March 2009

AbstractWith a growing interest in the large scale application of spouted beds, it is important to assess the stresses generated in the annular solids. Factors such as bed height, fluid pressure gradient, spout radius, frictional conditions at spout and vessel walls, and the angle of internal friction of the solid particles may all affect the stresses. Here it is shown how all these variables may be included in an analytical model for the vertical stress distribution in a spouted bed. The approach proceeds through the determination of the mean effective stress on a horizontal plane of the bed is a function of height. Distribution factors, as employed by Walker for bins, are used to relate stresses at the spout wall and the vessel wall to the mean effective stress on a horizontal plane.
Quenching of pyrolysis products of p‐xylene in toluene‐kinetic studies of acetone‐soluble products
Authors: Kumar A. , Rao A. N. , Gupta S. K. 
Published: March 2009

AbstractPyrolysis of p‐xylene was carried out in a tubular reactor at partial pressures varying from 0.184 kPa to 2.199 kPa with steam as a diluent. The product stream was quenched in toluene, and the solid products formed in quenching were shown to consist of p‐cyclophane (acetone insoluble) and linear dimer, linear trimer and one immovable component (in TLC analysis) constituting the acetone‐soluble part. Their rates of formation in the quencher were experimentally determined. The kinetic model which was used to explain the rate data of p‐cyclophane formation(1) was extended to include the formation of linear dimer and trimer of p‐xylene. The rate expressions derived from the kinetic model were shown to be consistent with experimental results.
Simulation and design of distillation units for treatment of sulfite pulping condensates to recover methanol and furfural: Part I: Incorporation with an evaporation unit and use of secondary steam
Authors: Zacchi G. , Aly G. 
Published: March 2009

AbstractA distillation unit was simulated using DESTLA, a computer program for steady‐state calculations of general multi‐component distillation units. Vapor‐liquid and liquid‐liquid equilibria were both computed by EQUIL, a computer program for computation and plotting of such equilibria. The simulations resulted in a distillation unit consisting of three columns. Energy consumed in the first column dominates the operating costs of the unit. The first of the three different alternatives studied for satisfying the energy requirements of the first column is presented. Incorporating the first column into an evaporation unit yields low steam consumption. However, a decrease in evaporation capacity due to the temperature drop in the first column and complex control design are the disadvantages associated with this alternative.
Heats of mixing of amine‐alcohol systems. An analytical group solution model approach
Authors: Siman Jaime E. , Vera Juan H. 
Published: March 2009

AbstractMeasured heats of mixing for amylamine with n‐propanol, n‐butanol and n‐pentanol at 15°C and 35°C are reported. This experimental information has been used together with other literature heats‐of‐mixing data on amine‐alcohol systems to test the ability of the extended Analytical Croup Solution Model (AGSM) to correlate and predict exothermic heats of mixing. Predictions for amine‐alcohol systems, not included in the set of reference systems, are good with the exception of the predictions for systems containing methanol.
Excess enthalpies of binary gaseous system ethylene + carbon dioxide by flow calorimetry
Authors: Ba Le B. , Kaliaguine Serge C. , Ramalho R. S. 
Published: March 2009

AbstractExcess enthalpies in the gas phase for the ethylene‐carbon dioxide system have been measured by a continuous‐flow isothermal calorimeter. Excess enthalpies are presented for mol fractions ranging from approximately 0.15 to 0.85, at three temperatures: 298.15, 318.15 and 338.15 K. For each isotherm, measurements were made at four pressures: 1.036 MPa (150 psia), 2.072 MPa (300 psia), 3.454 (500 psia) and 4.835 MPa (700 psia). The experimental results are compared with predictions using the Benedict‐Webb‐Rubin and Redlich‐Kwong equations of state.
Mixing effects and hydrodynamics of vortex rings
Authors: Rohatgi A. , Baird M. H. I. , Wairegi T. 
Published: March 2009

AbstractVortex rings have been formed in water by impulsive flow through an orifice, and mixing effects due to the lings have been measured. Laboratory tests on the mixing of stratified layers of salt solution by vortex rings formed at a 6.35 cm diameter orifice have indicated that Froude number is an important factor in determining the energy efficiency of mixing. Field tests using a 25.4 cm orifice in Hamilton Harbour (18 m depth of water) have shown a small mixing effect. Further experiments with a 25.4 cm orifice in a test tank have shown that the vortex rings have a range of at least 30 m.
Convective heat transfer in a rotary kiln
Authors: Tscheng S. H. , Watkinson A. P. 
Published: March 2009

AbstractAn experimental study of convective heat transfer from hot air to the solid charge and walls in a non‐fired rotary kiln is reported. Ottawa sand was heated by passing it counter‐current to a flow of preheated air in a 2.5 m × 0.19 m I.D. rotary kiln. Axial temperature profiles of gas, wall and solids were measured. Local and average convective heat transfer coefficients from gas to solids and from gas to wall were determined assuming plug flow of gas and solids. Solid feed rates to 1750 kg/m2 h and air rates to 3300 kg/m2 h were investigated at rotational speeds to 6 r/min, holdup ratios to 17% and gas temperatures from 350–590 K. The gas/solids convective coefficient was found to depend on the gas through‐put and to a lesser extent on solids holdup and rotational speed. Over the range tested, the angle of kiln inclination, solids throughput and particle size showed no significant effect on heat transfer. Gas/wall coefficients were about a factor of ten below gas/solid coefficients. Heat transfer results are compared to the limited data available in the literature, and to commonly used equations. Correlations of the experimental data on gas/solids, and gas/wall coefficients are presented; data from the literature on the wall/solids heat transfer coefficient are summarized.
Theoretical analysis of laminar flow heat transfer in a flat‐duct wall reactor
Authors: Mori Shigeru , Inoue Toshiaki , Tanimoto Akira 
Published: March 2009

AbstractConjugated heat transfer in steady state was studied, assuming the interfacial reaction to be instantaneous and the flow to be a fully‐developed laminar condition. The thermal boundary condition at the outer surface of the duct wall is specified as the first kind or the third kind. Influences of the interfacial reaction, the conductance of the wall and the external convection on the heat transfer characteristics were found to be substantial through calculated numerical results of the interfacial temperature and the local Nusselt number. Cases with uniform interfacial heat source and without it were also examined under the third kind boundary condition.
Concentration multiplicity and stability for autocatalytic reactions in a continuous stirred‐tank reactor
Authors: Lin K. F. 
Published: March 2009

AbstractConcentration multiplicity and stability for autocatalytic reactions of the type A + R → R + R with overall rate expression \documentclass{article}\pagestyle{empty}\begin{document}$ -{\rm r}_A = {\rm kC}_A^m {\rm C}_R^n $\end{document} in a continuous stirred‐tank reactor (CSTR) is analyzed in a rigorous way in this paper. Important parameters for multiplicity criteria are reaction orders m and n, dimensionless space time Θ, and the ratio P of feed concentration of R to that of A. Necessary conditions for the system to have multiple exit concentrations (conversions) are defined in the (m, n, P) space. Multiplicity is guaranteed by limiting the dimensionless space time in a proper range in addition to the necessary conditions. Stability analysis shows that there is no periodic oscillation for the system. The upper and lower steady states of multiple solutions are both asymptotically stable. A unique steady state is globally stable.
Cultivation of spirulina maxima in an annular photochemical reactor
Authors: Leduy A. , Therien N. 
Published: March 2009

AbstractAn 8‐L annular photochemical reactor has been designed and built for the cultivation of micro‐ or semi‐microalgae at the laboratory scale. It may be operated in batch or continuous mode and is controlled for pH, temperature, gas mixture ratio (CO2 and air), flow rate, light intensity and also illumination type (daylight or plant growth light) and mode (continuous or intermittent). It behaves as a perfect mixed reactor for all concentrations of algal cells. The reactor was used for the cultivation of the blue‐green alga Spirulina maxima in a synthetic medium in both batch and continuous operations. At the dilution rate of 0.24 day−1, the optimal productivity was 0.91 g/L‐day for biomass or 0.55 g/L‐day for protein. This is equivalent to 14.5 g/m2‐day for biomass or 8.7 g/m2‐day for protein. The optimal productivity as well as the chemical composition of the algal biomass were comparable to results obtained from pilot plant studies and reported in the current literature.
The effectiveness of static hold‐up for absorption with a chemical reaction in a packed trickle bed: General order kinetics
Authors: Patwardhan Vilas S. 
Published: March 2009

AbstractThe effectiveness f of the intetfacial area of the static hold‐up for absorption with a chemical reaction in a packed trickle bed depends upon both the hydrodynamics and the chemical kinetics. The dependence of f on operating conditions is investigated for a general [m,n] order kinetics, for a liquid phase controlled absorption process. The chemical reaction is assumed to be fast. The results are presented graphically for n > 0. Analytical expressions are developed for the special case of n =0.
Cristallisation du trihydrate d'alumine: Concentration d'équilibre et constante cinétique de croissance
Authors: Flament Frederic , Cloutier Leonce , Methot J.‐Claude 
Published: March 2009

AbstractExperimental crystallization of alumina trihydrate from Bayer's process caustic solutions was performed at different temperatures and sodium hydroxide concentrations to obtain equilibrium concentrations of sodium aluminate. A first correlation is presented to predict the equilibrium state, and a second one for estimation of equilibrium concentration from initial crystallization conditions. This last equation can be utilized for mathematical models for industrial crystallization of alumina trihydrate. Results indicate equilibrium concentrations of alumina trihydrate which are 17% higher than those obtained experimentally from synthetic solutions and 10% higher than those from other types of industrial solutions. The apparent growth rate constant of particles has been evaluated for each experiment: results correlated by an empirical relation show that this constant is not only a function of temperature.
Hydroxylamine production by electroreduction of nitric oxide in a trickle bed cell
Authors: Bathia M. L. , Watkinson A. P. 
Published: March 2009

AbstractHydroxylamine was produced in a trickle bed cell by passing nitric oxide gas and sulphuric acid catholyte co‐currently downward through a cathode bed of tungsten carbide particles. The dependence of hydroxylamine concentration and current efficiency on cathode activity and particle size, flow rate and composition of gas and catholyte, bed height, and reactor temperature and pressure are reported. Hydroxylamine concentrations of up to 0.18 mol/L were produced at 62% current efficiency in a single pass through a 0.375 m high cell operated at atmospheric pressure and a current density of 213 A/m2. The hydroxylamine concentration increased with cell pressure, gas flow rate and decreases in catholyte flow and could be raised to 0.4 mol/L by recycling the catholyte. The process appears to be controlled by mass transfer at current densities over 400 A/m2 and by electrochemical reaction below about 300 A/m2.
Catalyst decay in the kinetics of methylcyclohexane dehydrogenation over Pt‐NaY zeolite
Authors: Corma A. , Cid R. , Agudo A. Lopez 
Published: March 2009

AbstractThe kinetics of the dehydrogenation of methylcyclohexane to toluene over platinum on NaY zeolite have been studied at 390°C and atmospheric pressure. Cumulative conversion data obtained at constant space velocity and various reaction times on stream was treated using the “Time on Stream” theory. In this way the rate constants for both dehydrogenation and catalyst decay have been determined.The reaction has been shown to occur via a series of consecutive partial dehydrogenations, with the first dehydrogenation as the rate controlling step. The influence of the partially dehydrogenated products as well as the influence of the toluene, on the deactivation of the catalyst is discussed.
Steady pressure driven two‐phase stratified laminar flow through a pipe
Authors: Ranger K. B. , Davis A. M. J. 
Published: March 2009

AbstractThe two phase pressure driven flow in a circular pipe in which the interface occupies an arbitrary horizontal position has, as shown by earlier authors, an explicit analytical solution in which the velocities are expressed as Fourier integrals. Here this is used to express the volumetric fluxes of each fluid as one‐variable integrals whose values can be easily computed. The results agree with those obtained by Gemmell and Epstein by numerical integration of the differential equations.
The simulation of turbulent mixing with simultaneous reaction of miscible reactant streams
Authors: Radford R. D. , Harris I. J. 
Published: March 2009

AbstractThe use of stochastic models to predict chemical conversion in turbulent tubular reactors with separate but miscible reaction feed streams has been limited by the inefficiency of the computational processes. This is despite the advantages of the stochastic approach when compared to the more popular diffusional based techniques. Mathematic analysis of the stochastic process leading to direct algabraic representation of the stochastic model is presented which considerably reduces the computational time requirement of the stochastic approach.
Conjugated heat transfer to laminar flow with internal heat source in a parallel plate channel
Authors: Mori Shigeru , Kawamura Yuhji , Tanimoto Akira 
Published: March 2009

AbstractA steady heat transfer problem was analyzed as a conjugated problem between a fully‐established laminar flow and the duct wall, under two kinds of boundary conditions at the outer wall surface. The internal heat generation is described as a linear function of the fluid temperature.The influence of the heat conduction in the wall was found to be important for the case with small wall conductance under a boundary condition of the first kind, and also for the large wall‐conductance case under the second condition. Such influence is more significant for the case with an internal heat source.
A comparison of methods used to measure pore size in solids
Authors: Ternan M. , Fuller O. M. 
Published: March 2009

AbstractThe size of pores in a number of solid samples has been measured by nitrogen adsorption, oxygen adsorption, mercury porosimetry, scanning electron microscopy, and optical microscopy. All the pores in each of the solid samples investigated were straight, had a circular cross‐section, and had similar dimensions. By assuming the existence of contact angle hysteresis, agreement between the microscopy pore radii and mercury porosinietry radii measured both from penetration and from retraction was obtained. Dimensional changes in the solid may have contributed to the pore radii determined by nitrogen adsorption and oxygen adsorption being larger than the radii determined by microscopy.
Optimization of design and operating policy of an industrial two‐bed co‐shift reactor
Authors: Sterckx L. M. , Van Rompay P. V. 
Published: March 2009

AbstractThe optimal operating policy for a two‐bed adiabatic CO‐converter is computed using the Discrete Maximum Principle. The problem is then extended to determine also the optimal design of the system. A sensitivity analysis of the optimal solutions is presented, showing the influence of the principal process parameters. Economical, chemical and physical data have been obtained from an existing CO‐converter in a standard 1000 short Tons/day NH3 plant.
Particle deposition on a single spherical collector a three‐dimensional trajectory calculation
Authors: Beizaie Masoud , Tien Chi 
Published: March 2009

AbstractAerosol deposition from a flowing stream onto a single spherical collector with gravitational force acting transverse to the direction of flow was studied. The effects of inertial impaction, gravitation, interception and electrostatic forces were examined. In contrast to the case where gravitational force acts along the direction of the flow, the particle trajectories are not axisymmetrical and the trajectory equations are three‐dimensional. The formulation and numerical solutions of such equations represent the main task of this work.
Drag coefficient of relatively contaminated gas bubbles
Authors: Ishii Tsutomu , Pei David C. T. 
Published: March 2009

AbstractBased on the velocity profiles around clean and relatively contaminated gas bubbles, the tangential and normal stress, pressure distribution at the surface around the gas bubbles, and finally the viscous, form and total drag coefficient of the gas bubbles were calculated and compared with experimental values for dilute aqueous solutions of alcohols. The theory verifies the experimental observation that the total drag coefficient of single gas bubbbles increases with the contamination factor. The effect of the void fraction of the gas bubble swarm on the total drag coefficient was examined by the use of a void function. Most of the void functions for the relatively contaminated gas bubble swarms were between the values of potential flow and that of solid spheres.
Continuous emulsion polymerization of vinyl acetate. Part: II Parameter estimation and simulation studies
Authors: Kiparissides C. , Macgregor J. F. , Hamielec A. E. 
Published: March 2009

AbstractConversion data obtained over a wide range of operation of a continuous latex reactor for vinyl acetate polymerization were used to estimate the unknown kinetic parameters of a transient CSTR reactor model. Conversion‐time histories were adequately fitted by models of two levels of sophistication: a comprehensive model which solves for the age distribution function of polymer particles, and a simplified model that neglects the effect of particle size distribution for the case of continuous particle nucleation. These models were then used for simulation and control studies in an attempt to devise a practical control strategy(11). The existence of sustained oscillations was investigated by examining the behavior of the state variables in the phase‐plane.
Oxidation of low concentrations of hydrogen sulfide over activated carbon
Authors: Coskun I. , Tollefson E. L. 
Published: March 2009

AbstractThe oxidation of low concentrations of hydrogen sulfide with air over activated carbon was studied over the temperature range 24‐200°C using both fixed and fluid bed reactors. The predominant reaction, H2S + ½ Oa → H2O + S, was found to have an order of 0.5 with respect of H2S concentration. Activity of the catalyst decreased as the amount of sulfur deposited on it increased. Indirect evidence suggests that adsorption of water by the carbon also decreases its activity as a catalyst at lower temperatures. Values of the activation energy and the frequency factor were determined for various sulfur loadings using the fixed bed reaction system. Regeneration of the carbon loaded with sulfur was studied at temperatures between 150 and 500°C using steam as a carrier gas. Bright yellow sulfur was recovered. The regenerated carbon was shown to have its original activity.
Direct coking of athabasca tar sand
Authors: Filby J. E. , Flynn P. C. , Goldman J. M. 
Published: March 2009

AbstractYield patterns and product quality have been determined for the direct coking of Athabasca tar sand. Temperature and vapor residence time are the key variables affecting yield; tar sand residence time has a minor impact in yield provided that a minimum contact time is achieved. Yields are not sensitive to the composition of tar sand feed. Yields from direct coking are similar to those from commercial bitumen coking processes; previously reported variations in direct coking yields can be reconciled when liquid product endpoint and coking severity are considered.Coke deposited on the sand is readily burned, producing a flue gas high in SO2 and particulates, and a free‐flowing sand. The sand settles readily from a slurry and disposal presents no obvious environmental concerns.
Coal gasification in a spouted bed
Authors: Foong S. K. , Lim C. J. , Watkinson A. P. 
Published: March 2009

AbstractLow Btu gas has been produced by gasifying coal in a spouted bed reactor. Coal of size 0.8‐3.6 mm is fed continuously to a 0.15 m diameter spouted bed of inerts and gasified using mixtures of steam and air. Tests of the process with Western Canadian coals of free swelling index 0, 4 and 7 are reported. Gases of heating value to 3.61 MJ/m3 were produced at coal throughputs of 0.188 kg/m2s with the reactor operating at atmospheric pressure and temperatures to 930°C. Characteristics of the spouted bed gasifier are presented and results compared to commercial moving and fluidized bed systems. A simple mathematical model based on the two‐region spouted bed model of Mathur and Lim is used to predict the effect on steam utilization of bed composition, bed height and diameter, and particle size.
Rigorous design of high pressure natural gas pipelines using bwr equation of state
Authors: Moore R. G. , Bishnoi P. R. , Donnelly J. K. 
Published: March 2009

AbstractA model is presented for the prediction of pressure and temperature profiles in a high pressure gas pipeline. Using the BWR equation of state to predict the properties of the gas, an analytical approach reduces the problem to two nonlinear equations which can be solved numerically. Rigorous thermodynamic treatment of the energy and flow equations results in a model which yields good agreement with published data for high pressure natural gas pipelines. The model is also shown to predict frictional heating during the adiabatic flow of dense phase hydrocarbons.
Sedimentation of droplet dispersions in counter—current spray columns
Authors: Kumar A. , Vohra D. K. , Hartland S. 
Published: March 2009

AbstractA simple model is presented for the prediction of hold‐up and slip velocity in spray columns in which the continuous phase moves counter‐current to the dispersed phase. Analysis of 591 data points for 16 systems from 8 different sources show that the slip velocity is given in terms of the average drop diameter of the drop swarm and the physical properties of the system by:

for 7 < Re < 2450 and 0.01 < ϵd < 0.75. This equation predicts the slip velocity to within 10% for 70% of the data points and to within 20% for 92% of the data points.