bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified analytical prediction of distillation column startup time at total reflux
Authors: Iribarren Oscar A. , Chiotti Omar J.
Published: March 2009

A short‐cut explicit expression is presented for distillation at total reflux that predicts the time it takes to shift the reboiler composition from an initial charge composition to the final steady state composition.

The prediction is of interest when handling low relative volatility mixtures, as in isomeric or isotopic distillations, where the startups involve times in the order of a day or more.
Gas‐liquid mass transfer in the bubble column with viscoelastic liquid
Authors: Suh I.‐S. , Schumpe A. , Deckwer W.‐D. , Kulicke W.‐M.
Published: March 2009

The effects of liquid‐phase viscosity, pseudoplasticity, and viscoelasticity on gas‐liquid mass transfer in a bubble column have been investigated using aqueous solutions of sucrose, xanthan, polyacrylamide, and mixtures of xanthan and polyacrylamide. The elastic properties, considered in the form of the Weissenberg number, decreased the volumetric mass transfer coefficient by a factor of up to 5. The effect was strong even at low Weissenberg numbers encountered in many liquids, the elasticity of which is usually neglected.
Experimental simulation of large‐scale bioreaetor environments using a Monte Carlo method
Authors: Namdev Pradyumna K. , Yegneswaran Pallavur K. , Gray Murray R. , Thompson B. G.
Published: March 2009

Cells grown in production‐scale stirred bioreactors experience fluctuating concentrations due to local variations in supply and consumption of oxygen and nutrients. A new method for studying the effects of fluctuations in local conditions on growth and productivity of cells was developed using a Monte Carlo approach to simulate circulation within a fermenter. A small fermenter was driven through cycles of aeration and feeding, with the time of each cycle controlled by a Monte Carlo method to give a log‐normal distribution. Experiments with Monte Carlo supply of air to batch and fed‐batch cultures of Saccharomyces cerevisiae showed that the method gave reproducible results which were different from both periodic cycling and continuous supply. When substrate was provided to a fed‐batch culture of S. cerevisiae according to the Monte Carlo method, the yields of biomass were higher than experiments with continuous feeding or periodic feeding.
Desulfurization of benzothiophene with molybdenum naphthenate. Application of statistical analysis to evaluate the role of donor solvent
Authors: Ng F. T. T. , Walker G. R.
Published: March 2009

The activities of molybdenum naphthenate and cobalt naphthenate for benzothiophene desulfurization are studied at 350 to 400°C and 6.9 to 13.8 MPa pressure. Molybdenum is found to be more active than cobalt naphthenate for desulfurization. At 400°C, using 104 mg/kg Mo on benzothiophene in tetralin under 6.9 MPa H2, over 90 mol % conversion of benzothiophene to ethylbenzene is observed. No styrene is detected. The dominant pathway for desulfurization is proposed to be via the initial hydrogenation to dihydrobenzothiophene, followed by elimination of H2S to generate ethylbenzene.

The relative roles of donor solvent and molecular hydrogen in desulfurization are evaluated using a novel application of statistical analysis and fractional factorial design. At 4000 mg/kg Mo on benzothiophene, statistical analysis clearly isolates hydrogen atmosphere as the dominant factor affecting benzothiophene conversion. This result is also in agreement with thermodynamic predictions where benzothiophene conversion proceeds more favorably with hydrogen relative to tetralin.
Thermodynamic analysis of the thermochemical decomposition of H2S in the presence of iron sulphide
Authors: Berk Dimitrios , Heidemann Robert A. , Svrcek William Y. , Behie Leo A.
Published: March 2009

The decomposition of H2S by a two‐step closed loop thermochemical decomposition process was investigated. In the first step, H2S decomposes by reacting with iron sulphide to produce hydrogen and a solid solution consisting of FeS and S2. In the second step, the solid solution is decomposed at high temperature to recover sulphur and the iron sulphide which is reused in the first step. The thermodynamics of the first reaction were studied in detail by taking into account 12 gas phase chemical reactions and the phase equilibrium that is established between the sulphur in the gas and in the solid solution. The non‐linear system of 13 equations, which relate the fugacities of the components at equilibrium to the equilibrium constants, were numerically solved by the Newton‐Raphson iteration technique. The calculation results showed that the gas phase at equilibrium contains predominantly H2S, H2, and H2S2. The equilibrium conversion was found to decrease with increasing temperature; however, when the sulphur content of the solid solution was small, high hydrogen yields were possible even at high temperatures.
Kinetic studies of the pyrolysis of sewage sludge by tga and comparison with fluidized beds
Authors: Dümpelmann Ralf , Richarz Werner , Stammbach Marc R.
Published: March 2009

The pyrolysis of sewage sludge was examined by thermogravimetric analysis using different heating rates, particle sizes and final temperatures. A semi‐empirical model was developed with four global consecutive/competitive reactions to volatile and solid products including also a heat balance. This model was extrapolated to isothermal reactor conditions and compared to experimental data on fluidized bed pyrolysis. Depending on the particle size and reactor temperature, about 90% of the maximum conversion in a fluidized bed takes place under external heat transfer control, the rest under kinetic control. Incomplete conversion occurs at short particle residence times, which were calculated approximately by the model.
Vapor phase reaction of cyclohexanone oxime over boria modified HSZM‐5 zeolites
Authors: Takahashi Takeshige , Ueno Kazuhiko , Kai Takami
Published: March 2009

The vapor phase Beckmann rearrangement of cyclohexanone oxime has been carried out over zeolites and boria modified HZSM‐5 zeolites to elucidate the effects of acidity and acid strength distribution on the conversion and ε‐caprolactam selectivity. Although ε‐caprolactam selectivity was increased with the SiO2Al2O3 ratio in a HZSM‐5 zeolite, the highest selectivity in the study was accomplished over a boria modified HZSM‐5. The selectivity was dependent on the ratio of weak acid sites to strong acid sites. The boria played an important role in controlling the acid strength distribution of the zeolites.

It was found that the production of a polymer over strong acid sites caused a decrease in ε‐caprolactam selectivity during the reaction.
Boundary layer model for char combustion and gasification
Authors: Özüm B. , Chambers A. , Kovacik G. , Oǧuztöreli M.
Published: March 2009

A non‐steady boundary layer model is developed for numerical simulation of combustion and gasification of a single shrinking char particle. The model considers mass and energy conservation coupled with heterogeneous char reactions producing CO and homogeneous oxidation of CO to CO2 in the boundary layer surrounding the char particle. Mass conservation includes accumulation, molecular diffusion, Stefan flow and generation by chemical reaction. Energy conservation includes radiation transfer at the particle surface and heat accumulation within the particle. Simulation results predict experimentally measured conversion and temperature profiles of a burning Spherocarb particle in a laminar flow reactor. Effects of bulk oxygen concentration and particle size on the combustion process are addressed. Predicted particle temperature is significantly affected by boundary layer combustion of CO to CO2. With increasing particle size, char gasification to char combustion ratio increases, resulting in decreasing particle temperature and increasing peak boundary layer temperature.
Constrained chemical equilibrium and incompletely specified elemental abundance data
Authors: Norval G. W. , Phillips M. J. , Missen R. W. , Smith W. R.
Published: March 2009

A general method for the computation of equilibrium composition in the presence of linear equilibrium constraints on chemical potentials is described for use in a standard general‐purpose algorithm. The existence of constraints, implied by product specifications or measured product distribution, is related to incomplete specification of elemental abundances and has implications for feed composition. The method is illustrated by two examples: SO2 removal from stack gas and catalytic reforming. The distinction between equilibrium subject to equilibrium constraints on chemical potentials and that subject to stoichiometric restrictions is emphasized.
Mass transfer in structured corrugated packing
Authors: Nawrocki P. A. , Xu Z. P. , Chuang K. T.
Published: March 2009

The performance of structured corrugated packing has been simulated by establishing mechanistic models for liquid distribution, liquid flow on the packing surface and mass transfer. The models were used to investigate the effect of packing height, liquid load, initial maldistribution as well as differing initial distribution and solid‐liquid contact angle on the packed column performance.

Wetted surface area is the primary value of interest and the simulated results compare very well with those predicted by Onda (1968). The results clearly demonstrate that the wetted surface area is a strong function of the solid‐liquid contact angle. Other predicted values such as mass transfer coefficients and overall height of a transfer unit show reasonable agreement with published data.
Phase equilibria calculations for ill‐defined mixtures using the prsv equation of state
Authors: Cheluget E. L. , Vera J. H.
Published: March 2009

A method for the calculation of vapor‐liquid equilibria (VLE) for multicomponent systems using continuous thermodynamics is presented. The Extended Spline Fit Technique (ESFT) is used to represent the molar distribution curve of petroleum fluids. A continuous version of the Peng‐Robinson‐Stryjek‐Vera (PRSV) equation of state (EOS) with Generalized Single Carbon Number Properties (GSCNP) is utilized. For continuously distributed components, following the suggestion of Hendriks (1987), the number of equations solved is reduced through integration over the range of the distributing variable using Legendre‐Gauss quadrature. Integrated equations are solved using accelerated successive substitution. Flash, dew and bubble point calculations for an imaginary and a real system yield satisfactory results.
Interaction between bubbles and fibre optic probes in a bubble column
Authors: Chabot J. , Lee S. L. P. , Soria A. , de Lasa H. I.
Published: March 2009

Spherical bulb fibre optic probes, developed and applied for bubble characterization in a bubble column and a slurry bubble column at high temperature, were investigated. The principle of operation of these new optical fibre probes is based on the difference in refractive indices between the gas and the liquid phases. The interaction between the gas bubbles and the fibre optic probes in a bubble column was studied using photographic techniques. The first objective of these experiments was to study the response of the sensors upon contact with gas bubbles of various sizes. The second objective of this study was to establish, under controlled situations, the optical probe bubble detection performance and ability for local quantitative measurements of the bubble rise velocity and the gas hold‐up.
Prediction of axial mixing coefficients in rotating disc and asymmetric rotating disc extraction columns
Authors: Kumar Arun , Hartland Stanley
Published: March 2009

The correlation of axial mixing in the continuous and dispersed phases of rotating disc and asymmetric rotating disc columns is presented. Published experimental results on continuous‐phase axial mixing for both single‐ and two‐phase flows, obtained with tracer injection methods and by solute concentration profiles, are considered. The correlation developed is based on 1055 data points for 32 liquid systems obtained by 19 different investigators. The axial mixing in rotating disc columns is found to be up to 20% larger than in asymmetric rotating disc columns.

Data for the dispersed phase are harder to correlate than those for the continuous phase. Since the available results are often contradictory, the correlation for the dispersed‐phase coefficient is thus less accurate than that for the continuousphase coefficient.
Modelling of mass transfer in extraction columns with drop forward‐mixing and coalescence‐redispersion
Authors: Qian Yu , Wang Jiading
Published: March 2009

The objective of this work is to model the effect of simultaneous drop forward‐mixing and coalescence‐redispersion on the hydrodynamics and mass transfer efficiency of a two phase countercurrent extraction process. Based on the flow mechanism and drop size distribution in extraction columns, a novel model with a simplified sequential algorithm is developed. It is much easier to use, and computationally less expensive, than a direct simulation technique which would typically be a tedious boundary‐value iteration method. A new concept of Effective Mass Transfer Coefficient is presented, from which the effect of drop forward‐mixing and coalescence‐dispersion on extraction performance is directly evaluated from an analytical expression. The results calculated from the model are satisfactorily compared to experimental results obtained from three actual extraction system in two pulsed sieve‐plate extraction columns. The relationship between the present model and the diffusion model is discussed and a parameter transformation equation for the two models is given.
Gas‐liquid mass transfer in taylor flow through a capillary
Authors: Irandoust Said , Ertlé Sylvie , Andersson Bengt
Published: March 2009

The gas‐liquid mass transfer in two‐phase flow through a capillary has been measured for water‐air, ethanol‐air and ethylene glycol‐air systems. A semi‐theoretical model has been developed and compared with experimental results. and a full computer simulations of the flow pattern and mass transfer using a flow simulation program have been made. The measured values are about 30% less than the calculated values.
Application of controlled cooling and seeding in batch crystallization
Authors: Bohlin Martin , Rasmuson Åke C.
Published: March 2009

Some aspects of batch cooling crystallization in the industrial practice are analysed by computer simulations. The results indicate that without appropriate kinetics and very accurate process control, even the qualitative effects of applying controlled cooling and seeding are highly unpredictable. An increase in product size by applying controlled cooling is likely to be successful only rather randomly and the size distribution becomes broader. A linear or weakly non‐linear cooling curve usually produces larger crystals than a natural cooling curve, and a better reproducibility than a controlled cooling curve. Seeding increases both size and reproducibility, but is also likely to increase significantly the coefficient of variation of the product distribution. The product weight mean size and coefficient of variation may increase or decrease at increasing amount of seeds, depending on governing kinetics.
Optimum CFST bioreactor design: Experimental study using batch growth parameters for saccharomyces cerevisiae producing ethanol
Authors: Wall Jason B. , Hill Gordon A.
Published: March 2009

An optimum CFST bioreactor design equation is presented which can be used with linear growth‐associated product inhibition models. Batch experiments were performed to determine Saccharomyces cerevisiae growth parameters required for solving the optimum design equation.

The three bioreactors were designed in decreasing volumes to achieve theoretical glucose conversions of 99.9% and 99.99%. At steady state, the bioreactors appeared to reach the theoretical conditions as long as the flowrates were held equal or slightly below the optimum conditions. At very low flowrates, biomass death was observed in downstream reactors while at high flowrates, the theoretical conversions were not achieved. The experimental results confirm that optimally designed bioreactors can offer lower processing volumes to achieve high substrate conversions as compared to single CFST bioreactors.
Interactive behaviour of the α‐methylstyrene‐toluene mixture
Authors: Bui V. T. , Hamdouni A. , Léaonard J.
Published: March 2009

The Flory‐Huggins polymer solution theory can be extended to be applicable to a binary liquid mixture, yielding a parameter which represents the interactive behaviour of the mixture over the entire concentration range. Static vapour pressures of α‐methylstyrene‐toluene mixture were measured from 20 to 40°C by using a MKS Baratron manometer. The interaction parameter was then computed by means of the Wilson's equation. Positive values of the parameter and its concentration dependence may be explained by a lack of intermolecular interaction as well as by the free volume effect on mixing. These findings can also be supported by positive volume excess of the mixture, deduced from density measurements using a SODEV densimeter. The interactive pattern of the present mixture will be compared with that of other mixtures of α‐methylstyrene in tetrahydrofuran, cyclohexane and p‐dioxan.
Mixing rules for predicting the viscosity of bitumens saturated with pure gases
Authors: Mehrotra Anil K.
Published: March 2009

Mixing rules are developed and evaluated for predicting the viscosity of Alberta bitumens saturated with each of N2, CO, CH4, CO2 and C2, H6. The viscosity‐temperature variation for all bitumens and gases is expressed as [log(μ + 0.8) = ± 10 T]. A linear cross‐correlation between parameters b1 and b2 in the above relationship is identified and used subsequently to derive a one‐parameter viscosity equation: [log(μ + 0.8) = θ(ΦT)b]. where θ = 160, Φ = 0.008 for all bitumens and θ = ‐0.1, Φ = 0.015 for all gases. The two mixing rules examined in this study are: \documentclass{article}\pagestyle{empty}\begin{document}$ \log \left( {\bar \mu + 0.8} \right) = \sum v_i \,\log \left( {\mu _i + 0.8} \right) $\end{document} and \documentclass{article}\pagestyle{empty}\begin{document}$ \log \left( {\bar \mu + 0.8} \right) = \sum v_i \,\log \left( {\mu _i + 0.8} \right) + \sum \sum v_i v_j B_{ij} $\end{document}, where v represents the geometric mean of mass and mole fractions and Bij is a binary viscous interaction term. Predictions for the viscosity of gas‐saturated bitumens are validated with over 400 experimental data points for five Alberta bitumens at temperatures from 12 to 120°C and pressures up to 10 MPa.
Gas phase complete catalytic oxidation of aromatic hydrocarbon mixtures
Authors: Barresi Antonello A. , Mazzarino Italo , Baldi Giancarlo
Published: March 2009

In this work oxidation of benzene and ethenylbenzene (IUPAC name for styrene) as single compounds and in binary mixtures over a Pt honeycomb catalyst were investigated.

Both aromatic compounds showed zero‐order kinetics over a wide concentration range. The ethenylbenzene reaction rate was affected weakly by the presence of benzene, whereas benzene oxidation was inhibited strongly by ethenylbenzene. The Mars‐van Krevelen mechanism (which is generally accepted for single aromatic compound oxidation kinetics) gave rise to inconsistencies in describing mixture behaviour.

A different kinetic model is proposed, where benzene reacts from the gas phase and ethenylbenzene is adsorbed on the catalyst competing with oxygen for active sites. This model was able to interpret the oxidation of mixtures quite satisfactorily.
Solubilities of solids in supercritical fluids
Authors: Burk Robert , Kruus Peeter
Published: March 2009

The solubilities of several low‐volatility compounds in supercritical fluids were measured. The fluids used were pure carbon dioxide or carbon dioxide modified with small amounts of organic liquids. Some enthalpies of solution of solids in carbon dioxide at a density of 0.80 g/mL are presented. The enthalpy of solution of fluoranthene in carbon dioxide was found to be less endothermic at higher CO2 density. The order of solubilities in the modified fluids was the same as that in the pure liquid modifiers. The same apparatus was used to measure vapor pressures of some substances as well as solubilities.
The effect of liquid film vaporization on natural convection heat and mass transfer in a vertical tube
Authors: Yan Wei‐Mon
Published: March 2009

A numerical analysis was carried out to investigate the effects of film vaporization on natural convection heat and mass transfer in a vertical tube. Results for interfacial Nusselt and Sherwood numbers are presented for air‐ethanol and air‐water systems for various conditions. Predicted results show that heat transfer along the gas‐liquid interface is dominated by the transport of latent heat in association with the vaporization of the liquid film. Additionally, the predicted results obtained by including transport in the liquid film are contrasted with those where liquid film transport is neglected, showing that the assumption of an extremely thin film made by Chang et al. (1986) and Yan and Lin (1990) is only valid for systems with small liquid mass flow rates. For systems with a high liquid film Reynolds number, Re10, the assumption of an extremely thin film is seriously in error.
Spouted bed and spout‐fluid bed behaviour in a column of diameter 0.91 m
Authors: He Y‐L. , Lim C. J. , Grace J. R.
Published: March 2009

Hydrodynamic measurements were obtained in a half‐column of diameter 0.91 m equipped with a conical base using particles of diameter 3.3 to 6.7mm with operation both as pure spouted beds and in the spout‐fluid bed mode. Comparison of the experimental results for minimum spouting velocity with equations in the literature generally gave unsatisfactory agreement. On the other hand, the correlations of McNab (1972) and Hadžisdmajlović et al. (1983) gave reasonable predictions of spout diameters in spouted and spout‐fluid beds respectively. Hydrodynamic regimes with auxiliary air present were broadly similar to those determined in smaller columns. However, there were substantial dead regimes at the bottom of the column. A finite difference model based on the vector form of the Ergun equation gave good predictions of air flow distribution and longitudinal pressure profiles.
Separation and residence times of larger particles in a spout‐fluid bed
Authors: Waldie B.
Published: March 2009

Optimum conditions for the separation of added large particles from a spout‐fluid bed of Geldart Type B powder have been determined. A shallow bed, 100 mm in diameter, with porous conical distributor was used. Mean and distributions of residence time of the large particles depend on the two gas flow rates, especially that to the distributor, and on spout inlet diameter and large particle size. Bed regimes studied were mainly spouting with aeration and spout‐fluidization. In the latter regime an optimum range of fluidizing gas flow rates that minimised mean and spread of residence times was identified. RTD data were correlated by a model incorporating a minimum time supplemented by a distribution for an ideally mixed system.
Fluid flow pattern and solids circulation rate in a liquid phase spout‐fluid bed with draft tube
Authors: Grbavčić Ž. B. , Vuković D. V. , Jovanović S. Dj. , Garić R. V. , Hadžismajlović Dž E. , Littman H. , Morgan M. H.
Published: March 2009

The fluid flow pattern and solids circulation rate in a liquid phase spout‐fluid bed with a draft tube were studied in a semi‐circular column 196 mm in diameter equipped with a semi‐circular draft tube 34.5 mm in diameter using water and spherical glass particles 1.20, 1.94 and 2.98 mm in diameter. Both the solids circulation rate and fluid distribution between the draft tube and the annulus are influenced by the location of the draft tube, the relative magnitude of the inlet spouting and annulus flowrates, and the total fluid flowrate entering the bed.

A one‐dimensional steady state model of vertical non‐accelerating liquid‐solids flow predicts the solids mass flux in the draft tube with a mean deviation of 12.3% when experimental values of the axial pressure gradients in the draft tube and annulus are specified. A simple correlation for the fountain height is also presented.
Fluid dynamics characterization of a pneumatic bed using a spouted bed type solid feeding system
Authors: Ferreira M. C. , Freire J. T.
Published: March 2009

The development of a bed is reported, in which characteristics from spouted beds and pneumatic conveying are combined. The apparatus can be described as a pneumatic transport bed modified by the introduction of a recirculation process for inert materials, which leads to a final configuration akin to that of spouted beds. The dependency of the particle recirculation rates on the air flow rates and on the distance between the air inlet and the lower end of the central tube (z0) was investigated. Also studied was the variation of the total pressure drop with air flow rate, for different loads of inert materials (glass spheres, dp = 2.8 mm) and different z0 values.
Hydrodynamics and interphase heat transfer in a swirled spouted bed
Authors: Dolidovich A. F.
Published: March 2009

A new modification of a spouting technique, a swirled spouted bed (SSB), is developed and proposed to increase the efficiency of heat treatment of polyfractional and fine particles and to reduce their entrainment. It is shown that under the developed spouting conditions the SSB pressure drop is 20‐30% and incipient spouting velocity is 40‐50% lower whereas an interphase heat transfer rate is 15‐25% higher as compared to a classical spouted bed (CSB). An empirical correlation is proposed to determine the SSB pressure drop under developed conditions.
Batch and continuous spouted bed drying of cereal grains: The thermal equilibrium model
Authors: Zahed Adnan H. , Epstein Norman
Published: March 2009

A complete set of equations with no adjustable parameters are written for numerically predicting the variation of grain temperature and moisture content with time for batch drying of well mixed deep beds of three cereal grains, as well as the exit grain and air moisture contents and temperatures for continuous drying. Unlike previous studies, the surface moisture content of the grains is not assumed constant.

Agreement with both batch and continuous spouted bed drying data from the literature is good, in the continuous case especially when the assumed exit age distribution of the isothermal bed solids is specific to spouting.
Prediction of spouted bed reactor performance using kinetic models
Authors: Gorshtein A. E.
Published: March 2009

The form of the equation governing the kinetic model of a reactor depends on the mixing regime of the reacting phases and the conversion kinetics. The formation of detached flow in a spouted‐bed reactor results in backmixing of the solid material. Therefore, the processes in a spouted‐bed reactor can be described by a diffusion (quasihomogeneous) model equation. The paper compares the values of the production capacity of a spouted‐bed reactor calculated using the diffusion model with experimental values of the efficiency of green ultramarine oxidation (kinetic region), of oxidative calcination of some metal sulphides (mixed region), and of the ion exchange extraction of copper from solutions (diffusion region). The kinetics of the corresponding conversions are also described.
Mass transfer in tube banks with two‐phase flow
Authors: Giorgio Ana Chiappori De Del , Cavatorta Omar N. , Böhm Ursula
Published: March 2009

The fluid dynamic behaviour and the liquid‐solid mass transfer to horizontal cylinders, under bubble induced convection, was investigated. The gas void fraction was measured and overall mass transfer coefficients were determined for single cylinders as well as for banks of tubes with various characteristics.
Multiple reactor testing of a synthetic sorbent for regenerative sulfur capture in fluidized bed combustion of coal
Authors: Wolff E. H. P. , Gerritsen A. W. , Van Bleek C. M. Den
Published: March 2009

A new synthetic regenerable sorbent was developed as an alternative to limestone and dolomite for regenerative sulfur capture in fluidized bed combustion (FBC of coal. The sorbent consists of CaO (8‐9 wt%) on a spherical 3 mm diameter γ‐Al2O3 support. A shrinking unreacted core model (SURE2) is proposed to describe the sulfation process. Experiments have been carried out in a 12 mm internal diameter fixed bed reactor, a 0.05 m ID fluidized bed reactor and a thermobalance. The results obtained for all three reactors are in good agreement with the predictions of the SURE2 model.
Comportement thermique et chimique de particules solides subissant une réaction de décomposition endothermique sous ľaction ďun flux de chaleur externe
Authors: J. Lédé  , Villermavx J.
Published: March 2009

Le présent article a pour objet ľétude théorique et expérimental des conditions thermiques et chimiques dans lesquelles s ' effectue la décomposition endothermique de particules solides sous ľaction ďun flux de chaleur extérieur. La réaction, du type Solide1 → Solide2 + Fluides est supposée s ' effectuer en régime chimique. Après une phase de chauffage pur, le grain solide commence à réagir dès q 'il atteint une certaine température seuil TR. La réaction s ' effectue alors dans des conditions quasi isothermes. Les variations de TR ainsi que ľeffet de stabilisation de température dépendent des propriétés des particules, de la réaction chimique (cinétique et thermodynamique) et des conditions de transfert de chaleur, que ľon fait apparaǐtre sous forme de trois critères adimensionnels: critère ďactivation, de thermicité et nombre de Damköhler. Les prévisions théoriques sont en très bon accord avec les résultats de mesures expérimentales effectuées sur la réaction de décarbonatation de NaHCO3 en réacteur cyclone.
Gas hold‐up behavior of mechanically agitated gas‐liquid reactors using pitched blade downflow turbines
Authors: Rewatkar V. B. , Deshpande A. J. , Pandit A. B. , Joshi J. B.
Published: March 2009

Fractional gas holdup was measured in 0.57, 1.0, and 1.5 m i.d. vessels. Pitched blade downflow turbines (PTD) were used as the impeller. Design details of the impeller, such as the impeller diameter (0.22 T to 0.5 T) and blade width (0.25 D to 0.4 D), were studied. The effect of sparger type, geometry and size on fractional gas hold‐up has been investigated in detail. Four different types of spargers (pipe, conical, ring and concentric ring spargers) were used. Sparger location was varied for all the types studied. Further, design details of the ring sparger, which gave the highest hold‐up were then studied in detail. These included ring diameter, number of holes and hole size. All the reported correlations for fractional gas hold‐up in mechanically agitated gas‐liquid reactors were tested and compared. A better correlation has been developed for pitched blade turbines.
Measurement of air bubble size using densitometer
Authors: Zhu S. , Pelton R. H. , Ajersch M. , Towers M. , Baird M. H. I.
Published: March 2009

A simple mass‐transfer model is derived which gives the initial air bubble size distributions in a dispersion of air bubbles in water from the density/time responses to a step increase of pressure. Bubble size distributions from the model showed reasonable agreement with direct optical measurements. This work is applicable to dilute dispersions of bubbles which experience a sufficiently large increase in pressure such that the resulting solution is unsaturated with air.
Solubility of H2S in n‐hexadecane at elevated pressure
Authors: Feng Guo‐Xiang , Mather Alan E.
Published: March 2009

The solubility of H2S in n‐hexadecane has been determined at 50, 100 and 150°C at pressures up to 7.4 MPa. The results were correlated with the Peng‐Robinson (1976) equation of state and Henry's constants were derived for comparison with low pressure data in the literature.
Performance of a divided flow exchanger
Authors: Subramaniyan N. M. , Changrani Rajnish , Narayan Rashmi , Vishavanath Shekhar , Kurdikar Somdatt , Suburamaniyan V. , Sankholkar Yatin
Published: March 2009

An analysis is presented of a 1‐2 divided flow exchanger where the temperature of shell and tube streams depend on tube arrangement. Effect of having unbalanced tube passes is assessed for two possible cases. Graphs are plotted that show the variation of thermal effectiveness and logarithmic mean temperature difference correction factor with ratio of heat capacity rates and number of transfer units. Combination of such exchangers is also studied.
Heat and mass transfer on the wavy film absorption process
Authors: Yang Ru , Jou Derming
Published: March 2009

Recently the absorption heat pumps and chillers have received considerable attention due to their low electricity consumption rate. Therefore, it is important to understand the transport mechanism of an absorption process. In this paper, a numerical study of the heat and mass transfer taking place on a wavy falling liquid film of an absorption process is presented. With previously solved periodic wavy film flow solutions, the finite difference method is employed to solve the heat and mass transport equations. The numerical solution indicates that the waves significantly increase the transport rates. A comparison of the transfer rates of the wavy film to that of the smooth film is presented to show that the mass transfer rate can be doubled.
A mathematical model of fluidized bed biomass gasification
Authors: Bilodeau J.‐F. , Thérien N. , Proulx P. , Czernik S. , Chornet E.
Published: March 2009

A mathematical model of biomass gasification in a fluidized bed has been developed. It considers axial variations of concentrations and temperature in the bubble and emulsion phases. The mass balance involves instantaneous oxidation and equilibrium devolatilization of the biomass, kinetics of solid‐gas gasification reactions as well as of gaseous phase reactions and interphase mass transfer and gas convection. The energy balance is solved locally for each vertical volume element, and globally on the reactor by iteration on the temperature at the bottom of the bed. Three parameters have been adjusted based on the experimental results: the heat transfer coefficient at the wall, the weighting of the kinetics of the water‐gas shift reaction and the fraction of biomass carbon remaining as char after devolatilization. The model is used to simulate a pilot scale (50 kg/h) biomass gasifier, and its predictions compared to experimental measurements. The temperature and gaseous concentrations are estimated with good accuracy for the experiments using a wood feedstock, except for the concentration of hydrogen which is overestimated.
Evaluation of capital cost data. part 7: Liquid waste disposal with emphasis on physical treatment
Authors: Wright David G. , Woods Donald R.
Published: March 2009

Capital cost correlations are given for oil‐water separators, equalization basins, primary clarifiers, clarifiers and clarifier mechanisms, reverse osmosis unit, ultrafiltration units, gravity filters and miroscreens. Data are included for raw sewage, intermediate and recirculation pumping stations and for preliminary treatment (or bar screens, grit removal, overflow and bypass chamber and Parshall flume), for grit removal, comminution and gas stripping. The correlations are accurate to ± 30%, expressed in Canadian dollars and adjusted to a Marshall and Swift value of 1000. Details as to what components are included in the cost are given. Data are given for the labour and material costs to create a working process module.

For inflation indices, a critique of the Engineering News Record, EPA small city, Marshall and Swift, Chemical Engineering and Southam inflation indices suggested that the Marshall and Swift index is most appropriate for the construction and process equipment studied here. Concerning the currency exchange, for the equipment and processes in this study, equipment costs the same whether expressed directly in US or Canadian dollars.

To put the current data into perspective, several hundred sources of cost data were analyzed. The major correlations are compared, on a consistent basis, with current data.
Modeling of unsteady flow around accelerating sphere at moderate reynolds numbers
Authors: Li R. , Boulos M.
Published: March 2009

The flow around an accelerating spherical particle of diameter ranging from 50 to 200 m̈m is studied in the range of Reynolds number between 0.1 and 100. The flow around the sphere is assumed to be laminar and two‐dimensional axisymmetric. The calculated drag coefficient is compared with the theoretical predictions of added mass term and Basset history term. Appropriate corrections for those two terms are proposed as function of the acceleration rate and the particle diameter.
Excess pressure losses in capillary flows
Authors: Kozicki W. , Kuang P. Q.
Published: March 2009

Accurate determinations of excess pressure losses at the entry and exit of capillary flows are essential for rheological characterization of fluids by capillary viscometry. A modification of Bagley's end correction method is presented which accounts for the effects of slight variations in the diameters of the tubes of varying length used in the evaluations. The method was applied to capillary flows of dilute aqueous Polyox solutions using the three homologues WSR 301, Coagulant and FRA of Polyox. The excess pressure losses were found to increase with increase in the apparent shear rate, polymer concentration and tube diameter.
Effect of oil viscosity on the rheology of oil‐in‐water emulsions with added solids
Authors: Yan Yuhua , Masliyah Jacob H.
Published: March 2009

This paper reports an experimental study on the effect of oil viscosity on the rheology of oil‐in‐water (o/w) emulsions with added solids. Four oils having a viscosity range of 0.0024 to 306 Pa . s were used. The size ratio of the solids to oil droplets was varied from 2 to 16. The addition of smaller size solids to the emulsions yielded a higher viscosity than that of larger solids at the same solids volume fraction. However, when the solids were sufficiently large such that the emulsions behaved as a continuous phase towards the solids, the viscosity of the emulsion‐solids mixtures tended to be independent of the solids size.

The critical size ratio of the solids to oil droplets, above which the emulsions behaved as a continuous phase towards the solids, increased with the oil viscosity. The critical size ratio varied between 3 and 10.
Acid hydrolysis of cellulose. part i. experimental kinetic analysis
Authors: Dadach Zin‐Eddine , Kaliaguine Serge
Published: March 2009

The main objective of this investigation is to obtain experimental data for the sulfuric acid hydrolysis of cotton and mechanically pretreated cotton fibres. These data indicate that some glycosidic bonds of cellulose have very high accessibility to catalytic ions. It was also shown that milling increases the accessibility of some glycosidic bonds of cellulose and decreases the volume of the crystalline regions of cotton. From the glucose yield versus time data, it was found that the effect of milling on the rate of cellulose depolymerization depends on the reactivity and accessibility of the glycon rings of cellulose. It was also found that at 1OO°C, the rate of cellulose depolymerization was not affected by the extraction of cotton wax and this was related to a rolling up process of cotton wax caused by melting. The kinetic constants of glucose degradation and cellobiose hydrolysis have been determined for the stochastic simulation of cellulose depolymerization which is the subject of the second part of this work.
Anaerobic fermentation of xylose by pichia stipitis: The effect of forced cycling of ph
Authors: Ryding Per‐Ola , Nlklasson Claes , Lidén Gunnar
Published: March 2009

Xylose fermentation by Pichia stipitis was examined using a two‐stage batch process. The cells were first grown aerobically on D‐xylose (5 g/L), whereafter additional xylose (10 g/L) was added and fermented during anaerobic conditions (T=30°C). The optimum pH value for a fermentation with constant pH was found to be 4.5 (maximum specific ethanol production rate 0.21 g/(g h). Forced square wave cycling of the pH between 4 and 5, and 3.5 and 5.5 (cycle time 30 min) during the fermentation stage resulted in a fermentation rate lower than the maximum rate, but with unchanged ethanol yields.
Kinetic modelling of gold cyanide multi‐cycle adsorption and elution using activated carbon in the presence of foulants
Authors: Otu Emmanuel O. , Byerley John J. , Robinson Campbell W.
Published: March 2009

A novel procedure was used to study the kinetics of multiple exposure of a granular activated carbon in a laboratory‐scale packed bed to solutions containing gold and sodium cyanide, or in addition one of several organic reagents commonly used in mineral processing. The repeated use of a carbon sample simulated the practice in industrial gold recovery operations. A batch, unsteady state adsorption model which assumed constant intraparticle diffusivity of Au(CN)2‐ was used to model the kinetics of gold uptake. Upon repeated exposure of a carbon sample, up to a 3‐ to 4‐fold decrease in the intraparticle diffusivity of Au(CN)2‐ was observed, combined with a much smaller loss of adsorption capacity.
Determination of mutual solubilities in aniline + n ‐hexane and furfural + cyclohexane systems by a laser light scattering technique
Authors: Ochi Kenji , Momose Masatoshi , Kojima Kazuo , Lu Benjamin C.‐Y.
Published: March 2009

A newly developed laser light scattering technique was used for the determination of mutual solubilities in two liquid systems at moderate pressures. The solubility data and the upper critical solution temperatures are reported for the aniline + n‐hexane and furfural + cyclohexane systems. The experimentally determined cloud points were satisfactorily correlated by the NRTL equation.
Local mass transfer for tube banks in two‐phase flow
Authors: Giorgio Ana Chiappori De Del , Cavatorta Omar N. , Böhm Ursula
Published: March 2009

The local mass transfer rate to tubes immersed in gas‐liquid two‐phase systems was studied using the electrochemical method. It was found that the mass transfer distribution around the tube perimeter is not uniform and depends on the geometry of the system, the properties of the liquid phase and the superficial gas velocity.

Taking into account the analogy between heat and mass transfer, these results may be useful in both fields.
On‐line determination of supersaturation of a kcl‐nacl aqueous solution based on density measurement
Authors: Redman Terry P. , Rohani Sohrab
Published: March 2009

A method is developed for the calculation of the saturation temperature of a KCI‐NaCI aqueous solution, based on the measurement of the density and temperature of a sample solution, and prior knowledge of the NaCl concentration. Experimental density and solubility data for solutions saturated with KCI in the temperature range of 299 to 321 K with concentrations of NaCl greater than 0.200 kg/kg H2O were used to develop the empirical correlation allowing the calculation of the solution saturation level.

The method is applicable in the on‐line determination of the level of supersaturation in a KCI crystallizer in which the NaCl concentration is known. Knowledge of the prevailing supersaturation is necessary for the control of crystal purity and crystal size distribution in industrial potash crystallizers.
Analysis of the mechanism of rare earth metal permeation through a liquid membrane with a chelating agent in the
Authors: Kojima Toshinori , Nakayama Chikako , Uemiya Shigeyuki
Published: March 2009

The effect of adding a water‐soluble chelating agent, diethylenetriaminepentaacetic acid (DTPA), to the feed phase was studied on the selective permeation of rare earth metal ions (Ln3+) through a supported liquid membrane (SLM) containing 2‐ethylhexyl phosphoric acid mono‐2‐ethylhexyl ester (PC‐88A). High selectivity of Pr to Nd was observed at a pH of 2.0 in the stripping phase, and selective permeation of La was observed at higher pH values. The permeation mechanism of the Ln3+ was analyzed, and the above results were explained by the change in the concentrations of free Ln3+ in the feed phase and Ln3+/PC‐88A complexes in the SLM with pH.
Measurement and prediction of the density of aqueous ternary mixtures of methyldiethanolamine and diethanolamine at temperatures from 25°c to 80°c
Authors: Teng T. T. , Maham Y. , Hepler L. G. , Mather A. E.
Published: March 2009

Densities have been measured for mixed aqueous solutions of N‐methyldiethanolamine (MDEA) and diethanolamine (DEA) at 25, 30,40,50, 60,70, and 80°C. The compositions of the ternary solutions are near 30 mass% solute, because of industrial applications for the absorption of acid gases.

The isopycnotic (same density) method, for predicting densities of multicomponent aqueous systems at 25°C has been used to predict the densities of the present non‐electrolyte mixed solutions at other temperatures. Predicted and observed density values are in good agreement (<0.06% error). The method has also been used to predict densities of some aqueous sea salt mixtures at temperatures ranging from 5 to 95°C. Again the predicted and observed values are in good agreement (generally <0.1% error).
A correlation to the solution of the two‐phase dispersion model
Authors: Qabazard Hasan , Johnson Marvin M. , Meier Paul F.
Published: March 2009

A correlation to the solution of the two‐phase dispersion model has been developed for gas‐solid fluidized bed reactors operating in the bubbling regime. An analytical solution was obtained for fractional gas conversion by using an exponential function to characterize the dense phase gas concentration profile. The coefficient of the exponential function was found to depend on gas axial dispersion and, in order to determine this parameter, a Peclet number correlation was developed. Model predicted gas conversions were in excellent agreement with experimental conversions for a variety of fluidized bed reaction data over a conversion range from 2.5 to 99%.
Drag on individual cubic assemblies of spheres in non‐newtonian tube flow
Authors: Subramaniam Girish , Zuritz Carlos A.
Published: March 2009

An obstacle in modeling aseptic processing of particulate foods is the lack of a reliable estimator for the drag force of the non‐Newtonian liquid phase on the suspended particles as they flow through the holding tubes of such systems. The objective was to develop an expression for the drag force on cubic assemblies of spherical particles suspended in a pseudoplastic fluid flowing in a tube.

An apparatus was assembled for direct measurement of the drag force exerted by solutions of sodium carboxymethyl cellulose (CMC) on the assemblies inside a tube. An empirical drag correction factor, as a function of particle volume fraction (applicable to Stokes' law), was developed.
Non‐newtonian liquid flow through globe and gate valves
Authors: Banerjee Tapan Kumar , Das Manas , Das Sudip Kumar
Published: March 2009

Experimental data on the pressure drop across 1/2‐in. globe and gate valves in the horizontal plane for non‐Newtonian pseudoplastic fluids in laminar flow are presented. Generalized correlations in terms of the various physical and dynamic variables of the system have been developed for prediction of the frictional pressure drop for each valve. Statistical analysis of the correlations suggest that they are of acceptable accuracy.