bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass transfer in external‐loop airlift bioreactors using static mixers
Authors: Chisti Yusuf , Kasper Michael , Moo‐Young Murray
Published: March 2009

The influence of static mixers on the overall gas‐liquid volumetric mass transfer coefficient (KLaL) was examined in an external‐loop type airlift bioreactor (approximately 15 L volume, 1.8 m static liquid height, Ar/Ad = 0.444). The study was conducted with aqueous salt solution (0.15 kmol ṁ m−3 NaCl) and with pseudoplastic solutions of carboxymethyl cellulose (0.2 − 0.6 wt./vol. % (g/100 mL) CMC).

Over a broad range of power law parameters K (10−3 − 10 Pa ṁ sn) and n (0.5 − 1.0), the presence of static mixers in the riser was found to enhance the KLaL relative to mixer‐free mode of operation. The extent of increase in KLaL depended on the fluid “thickness”, K: the higher the K, the greater the KLaL intensification due to static mixers. For otherwise identical conditions, the presence of static mixers improved KLaL by 30‐500%, depending on the fluid. The boost in KLaL was associated with increased gas holdup and gas‐liquid interfacial area, which arose due to bubble breakup accomplished by the static mixing elements. Potential advantages of static mixers in upgrading the performance of oxygen‐limited fermentations were pointed out.
Characteristics of circulating vortex in the through‐flow between two concentric rotating spheres
Authors: Nakabayashi K. , Tsuchida Y.
Published: March 2009

The flow pattern and velocity distributions in the annulus of two concentric rotating spheres with meridional through‐flow have been studied by a finite difference solution based on the full Navier‐Stokes equations. These results were compared with these from an available but necessarily more approximate analytical solution. The flow fields near the inlet and outlet were elucidated and the effect of the through‐flow Reynolds number on the radial and azimuthal velocity components were clarified. These latter results were unobtainable by the analytical solution.
pH and conductivity of concentrated aqueous sodium sulfide/sodium carbonate solutions undergoing carbonation
Authors: Norman Jack C. , Sell Nancy J. , Ciriacks John A.
Published: March 2009

The extent of conversion of Na2S to H2S in a concentrated aqueous solution of sodium sulfide and sodium carbonate undergoing carbonation can be monitored by measuring the pH and conductivity. A simple linear equation has been developed to correlate the percentage of Na as Na2S with the temperature, pH, and conductivity. The apparent hydrolysis constants for carbonate and sulfide were calculated at temperatures ranging between 25°C and 65°C, and the reaction enthalpies and entropies determined.
Phase equilibria predictions for the CO2‐H2O‐NaCl‐bitumen system
Authors: Nighswander John A. , Kalogerakis Nicolas , Mehrotra Anil K.
Published: March 2009

Predictions of vapour‐liquid, liquid‐liquid and vapour‐liquid‐liquid phase equilibria are presented for the quaternary CO2‐H2O‐NaCI‐Peace River bitumen system at reservoir conditions. Henry's law correlations are regressed from available data for the CO2‐H2O, CO2‐(H2O + NaCl) and CO2‐bitumen binary sub‐systems. These correlations are incorporated into a model for predicting the phase behaviour of the quaternary system at temperatures of 80‐200°C, NaCl concentrations of 0‐10.5 mass% and pressures up to 10 MPa. It is shown that temperature, salt concentration and the global CO2 concentration significantly affect the distribution of CO2 in the liquid‐liquid region. The proposed model is simple and computationally less demanding than those based on equations of state.
Absorption of CO2 in some hybrid solvents
Authors: Yogish K.
Published: March 2009

Physico‐chemical absorption data of CO2 in three industrially important hybrid (physical + chemical) solvents were obtained in the temperature range of 0‐25°C and at a constant partial pressure of the gas of 95.59 kPa. The systems studied were N‐methyl 2‐pyrrolidone, sulfolane and methanol with a minute quantity of 40% aqueous dimethyl amine (aq.DMA). The CO2 uptake increased by two to three fold as compared to that of the pure physical solvents, and decreased with increases in temperature. Absorption also increased with the amount of aq.DMA added.
Flow regimes, hold–up and pressure drop for two phase flowin helical coils
Authors: Saxena A. K. , Schumpe A. , Nigam K. D. P. , Deckwer W. D.
Published: March 2009

Experimental results on flow pattern, hold–up and pressure drop are presented for cocurrent upward and downward air water flow in helical coils. A tube of 0.01 m internal diameter was used and the ratio of coil to tube diameter was varied from 11 to 156.5. Water flow rate was varied from 4.9 × 10‐6 m3/s to 92 × 10‐6 m3/s while the range of gas flow rate covered was 83 × 10‐6 m3/s to 610 × 10‐6 m3/s.

A new mechanistic approach is proposed to correlate pressure drop data in coils. The proposed model retains the identity of each phase and separately accounts for the effects of curvature and tube inclination resulting from the torsion of the tube. This makes it possible to use a single model to predict pressure drop for both upward and downward two–phase flow in coiled tubes. Required correlations for hold–up, interfacial friction factor and friction factors for individual phases are provided.
Absorption accompanied by a zero–order reaction
Authors: Landau J.
Published: March 2009

Simultaneous interphase mass transfer and a zero–order reaction is described by the film model of mass transfer. The analysis leads to the conclusion that three regimes of the process need to be considered. At low rates of absorption the reaction goes to completion in the film, and at higher rates it goes to completion in the bulk and proceeds there at zero apparent concentration of the reactant. At still higher rates of absorption the reaction does not go to completion and the reactant is present also in the bulk in appreciable concentration.

Design procedures based on the results obtained are discussed for a well–mixed CSTR and for a column with con–tinuous change.
Characterization of hydrodynamic parameters in a multistage column contactor
Authors: Tsouris C. , Ferreira R. , Tavlarides L. L.
Published: March 2009

Accurate knowledge of hydrodynamic parameters is of major importance for the performance study of liquid‐liquid column extractors. The effects of operating parameters on dispersed phase holdup profiles, drop size distributions, and axial mixing in both phases were investigated in a 127 mm diameter multistage contactor of pilot plant scale for the toluene‐water physically equilibrated system. Correlations for the mean holdup, the mean drop size, and the continuous phase backmixing were obtained. A stronger dependence of holdup and drop size on the operating conditions and especially on the agitation speed was observed as compared to previous investigations for the same type of contactor. The axial mixing for the single phase flow was found to follow adequately an existing correlation, while the continuous‐phase axial mixing in two‐phase flows showed some deviations from other existing correlations. Also, flooding criteria, important for the control of the extraction process, were determined based on the shape of the holdup profiles.
A kinetic investigation of styrene/butyl acrylate copolymerization
Authors: Dubé Marc A. , Penlidis Alexander , O'driscoll Kenneth F.
Published: March 2009

An experimental investigation of the kinetics of the bulk free radical copolymerization of styrene/butyl acrylate initiated with 2,2′‐azobisisobutyronitrile (AIBN) was conducted at 50°C using various initiator concentrations and initial monomer ratios including the azeotropic composition.

Reactivity ratios were determined by analyzing composition data using the error‐in‐variables model. The experiments, designed using the Tidwell‐Mortimer criterion, were conducted in sealed ampoules at 50°C to low conversion levels (< 7%).

From the calculated reactivity ratios, the azeotropic composition was determined and further experiments were run at these conditions as well as at two other initial monomer feed compositions in order to collect composition, rate and molecular weight data. The experiments were run through the full conversion range at two different initiator concentrations.
A method for flexibility analysis of continuous processing plants
Authors: Chien D. C. H. , Douglas P. L. , Penlidis A.
Published: March 2009

A methodology has been developed for the analysis of operational flexibility of a continuous processing plant. An application has been demonstrated for a multipurpose plant with uncertain operating conditions. A practical flexibility analysis procedure using a direct search optimization algorithm is proposed to solve the problem. The method provides a heuristic screening technique that makes it possible to avoid the exhaustive enumeration of every constraint vertex, while the direct search optimization offers a simple and effective means to identify bottlenecks. A refinery multiperiod plant problem has been investigated in order to highlight the procedures which lead to the construction of flexibility indices for each operating mode.
Laminar flow of a liquid rivulet down a vertical solid surface
Authors: Doniec Andrzej
Published: March 2009

Conditions for an energy minimum of a liquid rivulet flowing down a vertical solid surface have been considered. The solution of the equation may yield a constant value equal to the maximum rivulet thickness and the curve z(x) representing the shape of the rivulet cross section (profile). The profile describes the smallest rivulet which may be formed for a given system. “Composed” solutions correspond to wider rivulets, e.g. finite films. Numerical integration has been performed over a wide range of the parameter characterizing the liquid, at contact angles ranging from 5° to 90°. The minimum rivulet concept, which makes it possible to describe a finite‐width laminar film of minimum thickness, extends the Nusselt theory.
Mass transfer in the entrance region for axial and swirling annular flow
Authors: de Sa M. S. , Shemilt L. W. , Soegiarto I. V.
Published: March 2009

Rates of mass transfer to the inner core of an annular flow system have been determined for the mass transfer entry region using the limiting current density method. Both in laminar and turbulent flow, the hydrodynamic and concentration boundary layers were not fully developed. The variation of the mass transfer coefficients with length of core section has been demonstrated, and the data for swirling flow correlated by the equation

for 1500<Re < 14000, 1500 < Sc < 6200 and 1.75 < L/De < 10.14. The data for axial flow in the entry region have been correlated by the equation.

for 1800 < Re < 12500 and Sc = 2604. Mass transfer enhancement in the entry region due to swirl when compared to axial flow‐systems with a jetting transverse inlet is only noticeable for Re > 6000, but is very significant compared to systems with fully developed boundary layers in axial or swirling flow.
Reactor design and operation for gas‐phase ethylene polymerization using ziegler‐natta catalysts
Authors: Lynch David T. , Wanke Sieghard E.
Published: March 2009

A well‐instrumented, semi‐batch reactor has been constructed for studying the gas‐phase polymerization of ethylene using solid Ziegler—Natta type catalysts. This reactor can be operated over the entire range of temperatures and pressures used in the commercial production of linear low, and high density polyethylenes. Successful operation of the reactor depends on careful control of the reaction temperature which in turn is mainly dependent on the total rate of polymerization. If this rate is too large, then the reaction temperature increases uncontrollably (thermal runaway) until catalyst deactivation occurs when melting polymer encapsulates the catalyst particles. Operating conditions are described which resulted in precise and reproducible kinetic measurements for a δ‐TiCl3 δ 1/3AlCl3 catalyst (Stauffer AA Type 2.1) with diethylaluminum chloride (DEAC) as the co‐catalyst. This system displayed first‐order kinetic behavior over the temperature range 20 to 90°C with an activation energy of 32.6 kJ/mol.
Hydrogenation of carbon dioxide by hybrid catalysts, direct synthesis of aromatics from carbon dioxide and hydrogen
Authors: Kuei Chi‐Kung , Lee Min‐Dar
Published: March 2009

Direct synthesis of aromatics from carbon dioxide hydrogenation was investigated in a single stage reactor using hybrid catalysts composed of iron catalysts and HZSM‐5 zeolite. Carbon dioxide was first converted to CO by the reverse water gas shift reaction, followed by the hydrogenation of CO to hydrocarbons on iron catalyst, and finally the hydrocarbons were converted to aromatics in HZSM‐5. Under the operating conditions of 350°C, 2100 kPa, and CO2/H5 = 1/2, the maximum aromatic selectivity obtained was 22% with a CO2 conversion of 38% using fused iron catalyst combined with the zeolite. Together with the kinetic studies, thermodynamic analysis of the CO2 hydrogenation was also conducted. It was found that unlike Fischer Tropsch synthesis, the formation of hydrocarbons from CO2 may not be thermodynamically favored at higher temperatures.
Immobilization of hybridoma cells in chitosan alginate beads
Authors: Overgaard S. , Scharer J. M. , Moo‐Young M. , Bols N. C.
Published: March 2009

A new method for immobilizing hybridoma cells using chitosan‐stabilized calcium alginate beads was developed. The ionotropic gelation of chitosan and calcium with alginate resulted in the formation of highly cross‐linked, porous beads that were mechanically and chemically stable in phosphate buffered medium. Hybridomas entrapped in these beads were cultured semi‐continuously using periodic medium exchange. Viable population densities in the order of 5 × I07 cells/mL were attained within the beads and up to two‐fold increases in volumetric monoclonal antibody (MAb) productivity over batch suspension cultures were observed. Oxygen mass transfer limitations within the chitosan‐alginate beads were evaluated by considering biokinetics and diffusive transport. Model equations were developed and used to evaluate the effect of bead diameter on the contained cells. The predictions were consistent with experimental observations of maximum viable population densities attained in beads of various size.
Characterizing bubbles in bioreactors using light or ultrasound probes: Data analysis by classical means and by neural networks
Authors: Bugmann G. , Lister J. B. , Von Stockar U.
Published: March 2009

The applicability of neural networks to a typical biochemical engineering problem was investigated. The data treatment required for a novel technique for measuring the mean bubble size and the specific interfacial area in aerobic bioreactors was chosen as an appropriate example in case. The new measuring technique is based on either light or ultrasound transmission measurements through the dispersion. The function relating the results of such measurements to bubble size cannot be explicitly modelled. It was therefore approximated by a purely mathematical function fitted to numerically simulated examples. By training neural networks, the same unknown relationship could be mapped with similar or better precision without any prior knowledge of its structure or form and without any physical understanding of the problem.
The economics of ethanol production by extractive fermentation
Authors: Daugulis Andrew J. , Axford Darryl B. , McLellan P. James
Published: March 2009

Extractive fermentation is a processing strategy in which reaction and recovery occur simultaneously in a fermentation vessel through the use of a water‐immiscible solvent which selectively removes an inhibitory product. We have developed an ethanol extractive fermentation process incorporating continuous operation, the ability to ferment concentrated feedstocks, and greatly reduced energy and water use. This article provides a detailed economic assessment of this process relative to current technology for an annual capacity of 100 million litres of ethanol. Extractive fermentation provides significant economic advantages for both grass roots and retrofitted plants. Producing anhydrous ethanol without distillation is a prospect.
NADH fluorescence in a fed batch fermentation by C. acetobutylicum
Authors: Srivastava A. K. , Volesky B.
Published: March 2009

The existing process kinetics model of the acetone‐butanol fermentation was adjusted and adapted for the fed‐batch mode of operation. The optimal sugar feeding strategy for maximum solvent production was determined from the model and implemented in an experiment where the fluorescent features of the culture were also determined. While the model predictions agreed with experimentally observed trends, the actual data did not compare well. The characterisation of the culture physiological state under dynamic growth conditions was attempted by utilizing on‐line fluorescence measurements and the concept of stoichiometric metabolic pathway rates. This methodology served well in assessing the NADH related culture metabolic activity and the substrate consumption rate in the solventogenic phase.
Analysis of final settling tank in relation to control of metal inhibition in the activated sludge process
Authors: Tyagi R. D. , Couillard D. , Tran F. T.
Published: March 2009

The design choices for the bioreactor and the final cell separator or settler in an activated sludge process are interrelated. Any physical or chemical disturbance in the bioreactor and subsequent use of parameters to control the disturbance will affect the performance of the settler. This paper shows how these factors can be integrated into a design concept leading to an optimum settler size. Mathematical relationships between sludge solids concentration, recycle, ratio, and sludge settling velocity in relation to metal inhibition have been derived, and the utility of a rational analysis of final settling tank thickening performance has been demonstrated. First laboratory batch sediment tests are used to characterize sludge sedimentation, then the mathematical expressions are used to estimate the performance of the final settling tank.
A mathematical model of a spouted bed gasifier
Authors: Lim C. J. , Lucas J. P. , Haji‐Sulaiman M. , Watkinson A. P.
Published: March 2009

A mathematical model of the spouted bed gasifier has been constructed based on simplified first order reaction kinetics for the gasification reactions and the stream tube hydrodynamic model of Mathur and Lim. This two region model treats the spout as an isothermal plug flow reactor with cross flow into a series of streamtubes forming the annulus. Each streamtube is considered as a plug flow reactor. The effects of kinetic and hydrodynamic parameters on model predictions are illustrated, and a comparison made with experimental gas composition profiles obtained in a 0.30‐m dia. gasifier.
Determination of reaction models from experimental measurements
Authors: Makino Mitsunori , Silveston P. L.
Published: March 2009

It is demonstrated through the use of transformation relations, function approximation and error limits that it is impossible to distinguish among rival gasification models using just a single temperature programmed reaction experiment. Two experiments at different heating rates must be used and the ratio between rates is important. These depend on the models to be distinguished.
The relationship between chemical structure and reactivity of alberta bitumens and heavy oils
Authors: Gray M. R. , Jokuty P. , Yeniova H. , Nazarewycz L. , Wanke S. E. , Achia U. , Krzywicki A. , Sanford E. C. , Sy O. K. Y.
Published: March 2009

Long residues (424°C +) from Athabasca, Cold Lake, Lloydminster, and Peace River were hydrocracked over a commercial NilMo on y‐alumina catalyst at 430°C, 13.9 MPa (2000 psia). The conversion of residue fraction ranged from 55 to 68%, and was correlated with the concentration of carbon bound to aromatic rings in the feeds. Conversions of sulfur, Micro‐Carbon Residue, and metals were all highest for Peace River feed, following the same ranking as residue conversion. Estimates for the breakage of carbon‐carbon bonds and the uptake of hydrogen were diagnostic in interpreting the reactor performance.
Circulating fluidized bed combustion of a high‐sulphur eastern canadian coal
Authors: Brereton C. M. H. , Lim C. J. , Legros R. , Zhao J. , Li H. , Grace J. R.
Published: March 2009

Combustion tests were carried out with Minto coal in combination with three different limestones in the University of British Columbia (UBC) pilot scale (152 mm square x 7.3 m tall) circulating fluidized bed combustion (CFBC) unit. Operating conditions were chosen to be typical of those employed in large‐scale CFBC power boilers. Recycling of fine particles captured by the secondary cyclone was found to be of considerable importance in increasing sulphur capture, enhancing combustion efficiency and reducing the amount of calcium sulphide in the solids residues. NOx emissions increased as the Ca:S ratio increased. Local gas concentrations inside the reactor were strongly influenced by the core‐annulus solids distribution patterns which characterize circulating fluidized beds.
The effect of Nb2O5 and ZrO2 additions on the behaviour of Li/MgO and Li/Na/MgO catalysts for the oxidative coupling of methane
Authors: Mcnamara D. J. , Korf S. J. , Seshan K. , Van Ommen J. G. , Ross J. R. H.
Published: March 2009

Incorporation of Nb2O5 or ZrO2 into both Li/MgO and Li/Na/MgO systems produced ternary and quaternary catalysts, respectively, capable of attaining optimal C2 yields and selectivities at lower temperatures relative to the unpromoted materials. The degree of enhancement effected by these metal oxide additives was compared to that produced by Li/MgO and Li/Na/MgO catalysts promoted with SnO2 or Co3O4. At reaction temperatures < 700°C, the Li/Co/MgO ternary system showed marked differences in behaviour compared to the other ternary catalysts tested. This was particularly evident in the variation in C2 selectivity with time on stream during ageing studies of (i) untreated materials, (ii) materials pretreated in CO2, and (iii) materials dosed periodically with CHCI3.
Modelling of the pyrolysis of biomass particles. Studies on kinetics, thermal and heat transfer effects
Authors: Koufopanos C. A. , Papayannakos N. , Maschio G. , Lucchesi A.
Published: March 2009

The present work provides a rationally‐based model to describe the pyrolysis of a single solid particle of biomass. As the phenomena governing the pyrolysis of a biomass particle are both chemical (primary and secondary reactions) and physical (mainly heat transfer phenomena), the presented model couples heat transport with chemical kinetics. The thermal properties included in the model are considered to be linear functions of temperature and conversion, and have been estimated from literature data or by fitting the model with experimental data. The heat of reaction has been found to be represented by two values: one endothermic, which prevails at low conversions and the other exothermic, which prevails at high conversions. Pyrolysis phenomena have been simulated by a scheme consisting of two parallel reactions and a third reaction for the secondary interactions between charcoal and volatiles. The model predictions are in agreement with experimental data regarding temperature and mass‐loss histories of biomass particles over a wide range of pyrolysis conditions.
Trickle‐bed reactors: Tracer study of liquid holdup and wetting efficiency at high temperature and pressure
Authors: Ring Z. E. , Missen R. W.
Published: March 2009

Liquid holdup and wetting efficiency were measured by means of stimulus‐response (pulse‐tracer) experiments in a trickle‐bed reactor, packed with a commercial hydrodemetallization catalyst, and operated at 10 MPa and 330–370°C, with a superficial liquid velocity of 1.4 to 8.3 × 10−4 m/s. The total liquid holdup was obtained from the first moments, and the external wetting efficiency from the second moments, of the response curves. The dynamic holdup obtained from the total holdup lies within the range described by existing correlations, but wetting efficiency is significantly lower than literature data obtained at ambient conditions.
Direct catalytic conversion of methane
Authors: Poirier Michel G. , Sanger Alan R. , Smith Kevin J.
Published: March 2009

Processes are being developed for the direct catalytic oxidative conversion of methane to higher hydrocarbons and oxygenates. The role of the catalyst in generating methyl radicals is established, and subsequent gas‐phase reactions are well understood. However, the role of several catalyst surface species remains a subject of interest. Application of present process technology using the most promising catalysts shows that direct methane conversion is not yet competitive with conventional processes. Increased yields of desirable products using new process configurations are required to obtain an economically viable process.
Catalytic palladium‐based membrane reactors: A review
Authors: Shu J. , Grandjean B. P. A. , Neste A. Van , Kaliaguine1 S.
Published: March 2009

This paper is an extensive review of the literature dealing with the class of catalytic membrane reactors which involves hydrogen permeable membranes made of palladium and palladium alloys. The fundamental factors which affect hydrogen permeability are first discussed. A classification of the many reactions which have been conducted in such reactors at both laboratory and commercial scales is then presented. The various techniques for the preparation of palladium‐ based membranes are described and the literature on modeling and design of these reactors is also reviewed.
Selectivity improvement using alternate flushing and reactant cycle steps
Authors: Lang X. ‐S. , Silveston P. L. , Hudgins R. R.
Published: March 2009

When a reactor is operated by alternately exposing the catalyst to hydrocarbon and oxygen, selectivity has been found to increase, but not for all partial oxidation products and not for all systems. In this study, multi‐step periodic operation in which the catalyst is alternately exposed to hydrocarbon and air with an inert gas pulse between either or both of the reactant gases is examined. Partial oxidation of butadiene over a promoted vanadia molybdate catalyst was used. The influence of cycle period as well as the location and duration of the inert flush upon oxygenate production and yield was studied. Multi‐step periodic operation using an inert gas for flushing was found not to be an attractive option for maleic anhydride from butadiene unless an increase in the yield of furan is desired.
Influence of particle size distribution on the performance of fluidized bed reactors
Authors: Grace J. R. , Sun G.
Published: March 2009

This paper reviews recent results obtained in our laboratory and elsewhere which show the importance of particle size distribution (PSD) in fluidized beds. Fines content in itself, often used as a descriptor, is not a sufficient parameter to characterize the PSD effect. Broadening the PSD affects gas flow through the dense phase, produces smaller bubbles, leads to more particles in the dilute phase and causes earlier transition to the turbulent hydrodynamic regime of fluidization. Chemical conversion is therefore enhanced by broadening the PSD, and the enhancement increases when the bed operates in the turbulent regime.
A high pressure solubility apparatus for gases of high solubility
Authors: Hayduk W. , Asatani H. , Miyano Y.
Published: March 2009

An apparatus is described for measuring gas solubilities at high pressure for gases of moderate to high solubility. Solvent, supplied by a metering pump, is continuously saturated with gas as it flows down a spiral rod. Gas is continuously supplied by means of a calibrated piston pump to provide a constant pressure. The solubility is determined from the relation between the solvent rate and the gas consumption required to achieve saturation. The solubilities of two chemically reactive gases, propene and isobutene, are reported for the solvents n‐butanol, chlorobenzene and n‐octane for three temperaturres, 298, 323 and 343 K, and a range of pressures from 0.2 to 1.9 MPa.
Transitional packed bed flow in standpipes
Authors: Zhang J. Y. , Rudolph V.
Published: March 2009

A quantitative criterion distinguishing stable from unstable transitional packed bed flow in standpipes is presented. This criterion can be used as an working guideline in actual standpipe operation. A fundamental and simple model based on stress free surface (SFS) theory has been developed. This model also provides a quantitative prediction method for the standpipe voidage.
Equilibrium solubility of H2S and CO2 and their mixtures in a mixed solvent
Authors: Macgregor Rosalynn J. , Mather Alan E.
Published: March 2009

The solubility of hydrogen sulphide, carbon dioxide, and their mixtures has been measured at 40° and 100°C in a mixed solvent consisting of 20.9 wt% MDEA (methyldiethanolamine), 30.5 wt% sulfolane (tetrahydrothiophene‐1, 1‐dioxide), and 48.6 wt% water. The results have been compared with those for aqueous 2.0 mol/dm3 MDEA and an analogous mixed solvent, containing AMP (2‐amino‐2‐methyl‐1‐propanol), which are available in the literature. These data were used to modify the solubility model of Deshmukh and Mather (1981) to account for the mixed solvent effects on the system thermodynamics. Results show that the model is useful as a first approximation in predicting acid gas solubilities; agreement with experiment was generally found to be within £15%.
Binary liquid–liquid equilibria of aniline–paraffin and furfural–paraffin systems
Authors: Sen Subhash C. , Maity Soumen , Ganguli Kausik , Goswami Kausik , Ray P.
Published: March 2009

Binary liquid‐liquid‐equilibria data for several aniline‐paraffin and furfural‐paraffin systems have been taken. These data along with data for other aniline‐hydrocarbon and furfural‐hydrocarbon systems from literature have been correlated using UNIFAC model. The UNIFAC group interaction parameters have been found to have a linear temperature dependence. The CH2 groups in cyclo and non cyclo paraffins require different interaction parameters. It was also found that a scaling of the combinatorial term is necessary for higher molecular weight hydrocarbons.
Void‐size distribution in two‐dimensional random packings of equal‐sized disks
Authors: Alonso M. , Satoh M. , Miyanami K.
Published: March 2009

The void‐size distribution in a random packed assembly of disks is expressed here as the distribution of the probabilities of finding circular voids of given sizes. A theoretical void‐size distribution is derived and compared with the distribution obtained through computer simulation. The two‐dimensional case discussed in this paper is applicable to the study of the kinetics of fines transfer and the characterization of the coating layer structure in powder coating systems.
Correlations for liquid‐phase mass transfer coefficients in bubble column reactors with newtonian and non‐newtonian fluids
Authors: Kawase Y. , Moo‐Young M.
Published: March 2009

The earlier work of Calderbank and Moo‐Young (1961) dealing with the liquid‐phase mass transfer coefficient in gas‐liquid dispersions is examined. Their well‐known empirical correlations for small and large bubbles which are free to move under gravity are theoretically derived. The analyses are based on the approach for natural convection mass transfer, and include the case where the fluid is non‐Newtonian. The predictions of the models are compared with reported experimental data and correlations.
Heat and mass transfer between bubbles and a liquid
Authors: Guy C. , Carreau P. J. , Paris J.
Published: March 2009

The understanding of the heat and mass transfer phenomena between hot bubbles and a liquid is particularly relevant to the design of direct contact heating and evaporation systems such as submerged combustion equipment. In this process, exhaust gas from a burner is dispersed in a liquid to be heated or evaporated. Various models for the prediction of the temperature and vapor content of the bubbles as a function of their residence time in the liquid are presented. Based on the experimental measurements of the bubble size and of the heating time and evaporation rate in an actual submerged combustion system, models using spherical, ellipsoidal and spherical‐cap bubbles, with or without internal circulation, are discussed and assessed. It is found experimentally that the bubbles are of a spherical cap shape. Bubble equivalent diameters between 15 and 25 mm and bubble velocities between 0.4 and 1.2 m/s are observed. The proposed models are used to compute the heating time and evaporation rate of the bath during a submerged combustion operation; the predictions are then compared to the experimental values. The rigid spherical cap bubble model is found to predict satisfactorily the heat and mass exchanges between the bubbles and the liquid.
Prediction of minimum velocity and minimum bed pressure drop for gas‐solid fluidization in conical conduits
Authors: Singh R. K. , Suryanarayana A. , Roy G. K.
Published: March 2009

Experimental investigations have been carried out for spherical and non‐spherical particles using beds comprised of single‐sized particles and mixtures in the size and particle density ranges of 439 to 1524 μm and 1303 to 4948 kg/m3, respectively. Five conical fluidizers with varying apex angles of 8.86, 14.77, 19.60, 32.0 and 43.2 degrees were used. Experimental values of minimum velocity and bed pressure drop with air as the fluidizing medium have been compared with their respective values obtained from different models available in the literature. Deviations for each chosen model have been presented.
Study of the gas circulation patterns in a uniflow cyclone
Authors: Gauther T. A. , Galtier P. , Briens C. L. , Crousle O. , Bergougnou M. A.
Published: March 2009

A uniflow cyclone is being studied to achieve the separation of hot solids from the gaseous products of ultra‐rapid fluidized (URF) processes. An experimental method with hot wire probes was developed to study the gas flow around the gas outlet, where the solids exit. The vortex penetration in the solids exit could be determined. The presence of solids greatly reduced the vortex penetration in the uniflow cyclone. Restricting gas circulation around the gas outlet dramatically impaired the cyclone collection efficiency. Therefore, good cyclone performance requires a proper design below the gas outlet.
Plate wettability and droplet diameter in a pulsed perforated‐plate extraction column
Authors: Ikeda Hidematus , Suzuki Atsuyuki
Published: March 2009

The liquid‐liquid‐plate contact angles of several plate materials were measured using a “preferential wetting method” proposed by the authors. The adhesional work (ISL), calculated on the basis of contact angles was utilized to evaluate plate wettability. The experimental results indicate that different plate materials affect differently plate wettability. The plate wettability of stainless steel in an aqueous phase was observed to be different from that in an organic phase. The droplet diameter in the mixer‐settler region of operation of a pulsed perforated‐plate extraction column using several different plate materials, was measured. An empirical correlation of mean droplet diameter: dp = 0.222(af/lSL1/3)−0.13 is proposed except for alumina plates with dispersed aqueous phase operation.
Batch adsorption of trichlorotrifluoroethane (freon‐113) onto activated carbon — surface diffusivity and pore diffusivity
Authors: Kodama K. , Kaguei S. , Wakao N.
Published: March 2009

Activated carbon was found more active than molécular sieve 13X and silica gel in adsorbing 1,1,2 trichloro‐1,2,2 trifluoroethane (CFE). Batch adsorption experiments were carried out with activated carbon to adsorb CFE at 15, 25 and 30°C. The adsorption isotherms of CFE on activated carbon were of the Langmuir type: q(C) = qm KC / (1 + KC) where qm and K were evaluated for the three temperatures. The measured bulk concentration‐time data were interpreted equally well with the surface diffusion model and the pore diffusion model; for the former model the surface diffusivity increased with increasing initial CFE concentration, and for the latter the pore diffusivity was independent upon the initial CFE concentration.
Momentum/heat transfer analogy for drag reducing fluids during turbulent boundary layer flow with small pressure gradients
Authors: Shenoy A. V.
Published: March 2009

There have been many attempts in the literature to develop analogies for momentum, heat and mass transfer to drag reducing fluids; however, none have considered the presence of a pressure gradient when formulating the analogies. In the present work, a momentum/heat transfer analogy has been developed under the influence of small pressure gradient for drag reducing fluids using the Nakayama et al. (1984) solution methodology for Newtonian fluids. The results of the present analysis have been found to compare well with existing theoretical expressions.
Settling of cylinders in power law liquids
Authors: Chhabra R. P.
Published: March 2009

New measurements on drag coefficient and wall effects on the free settling motion of cylinders in two shearthinning polymer solutions are reported. The ranges of conditions covered in this study are: 1 < Re∞∞ < 40; 0.25 < (LID) < 2; 0.079 < dID < 0.4, and n = 0.65 and 0.74. Both wall correction factor and drag coefficient results are in line with the Newtonian behavior provided a modified Reynolds number is used to represent the results.
Analysis of one dimensional grain model
Authors: Rao T. Rajeswara
Published: March 2009

Model equations for slab type pellet consisting of spherical grains are solved numerically. It is shown that some of the generalised equations reported in the literature for slab type pellets with slab type grains and spherical pellets with spherical and slab type grains are equally applicable to a slab type pellet with spherical grains. A sensitivity analysis of the model to various parametric changes has been made and compared with experimental data on zinc sulphide oxidation to indicate the significance of the various assumptions. It is also shown that the model can be extended to solid‐consuming reactions as well. Experimental results on gasification of carbon with carbon dioxide reported in the literature were verified satisfactorily with the present model equations.
The design of experiments when there are errors in all the variables
Authors: Keeler Scott E. , Reilly Park M.
Published: March 2009

The Error‐in‐Variables Model (EVM) applies to a large class of problems in parameter estimation in which there is error in all the variables. This property makes it of more general applicability than the widely used technique of ordinary Least Squares. While there is a voluminous literature on EVM there is nothing on a general method for designing experiments when EVM applies. In this paper we present an extension of the concept of D‐optimality to provide such a general method. It is illustrated by applying it to the estimation of copolymer reactivity ratios and to fitting an ellipse.
Signal processing considerations for extrusion pressure measurement
Authors: Pabedinskas A. , Cluett W. R.
Published: March 2009

This paper presents some important aspects of pressure signal measurement in an extrusion system, including work that has been done to identify the types and causes of the pressure fluctuations using spectral analysis, and the steps taken to obtain reliable pressure measurements when digital data acquisition equipment is used. It is shown that pressure fluctuations associated with the extruder screw rotation may appear as lower frequency fluctuations in the sampled pressure signal. This well‐known phenomenon called aliasing must be reduced or eliminated in order to avoid making erroneous conclusions about the cause of the fluctuations. A combination analog‐digital anti‐aliasing filter has been designed and implemented on an extrusion system equipped with an In‐line Wedge Rheometer.
Spouting of two‐dimensional beds with draft plates
Authors: Kalwar M. I. , Raghavan G. S. V. , Mujumdar A. S.
Published: March 2009

Two slotted two‐dimensional spouted bed units with flexible bed dimensions were used with draft plates to study spouting pressure drop and minimum spouting superficial velocity. The data were collected while varying slant angle, spout width, separation distance, length of bed, height of bed, and size of bed (geometrical similarity) using shelled corn, soybean, and wheat. The variables which affect the spouting pressure drop and air flow through the beds are discussed. Empirical correlations are developed following the principles of dimensional analysis and similitude. The developed correlations agree closely with the collected data.
Pyrolysis with partial combustion of oil shale fines in a spouted bed
Authors: Lisbôa A. C. L. , Watkinson A. P.
Published: March 2009

Pyrolysis with partial combustion of oil shale fines from the Irati Formation in Brazil has been investigated in a 30 cm diameter spouted bed reactor. Experiments were carried out at atmospheric pressure and temperatures between 450 and 600°C. The oi] shale particle size was less than 6.35 mm. Spouting gas temperatures ranged from 20 to 565°C. Three inlet gas pipe diameters and two spouted bed heights were studied. Operation of the process was found to be stable over a wide range of test conditions. Results are presented for oil and gas quality, efficiency of retorting and overall performance of the plant.
The british coal spouted fluidised bed gasification process
Authors: Arnold M. S. T. J. , Gale J. J. , Laughlin M. K.
Published: March 2009

British Coal Corporation has been developing an air‐blown spouted fluidised bed gasification process for the production of low calorific value fuel gas. Development of the gasifier at atmospheric pressure for the industrial market has established the commercial basis for a flexible gasification process, which can achieve coal conversion efficiencies of up to 95%. For larger‐scale use, a pressurised gasifier is under development as part of an integrated partial gasification combined cycle, coal‐fired, electricity generating system. Known as the British Coal Topping Cycle, the system offers significant advantages in terms of improved thermal efficiency, reduced generating costs and low environmental impact. The paper outlines the gasifier development programme for both applications.
Mixed convection heat and Mass transfer in a vertical channel with film evaporation
Authors: Yan Wei‐Mon
Published: March 2009

Numerical results are presented for effects of latent heat transport associated with film vaporization on laminar mixed convection heat and mass transfer in a vertical channel with a half channel width b = 0.01 m. The influences of the inlet liquid mass flowrate and wall temperature on the film vaporization and the associated heat and mass transfer characteristics are examined for air‐water and air‐ethanol systems with gas Reynolds number Reg = 2000. 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 in Lin et al. (1988) and Yan and Lin (1989) is only valid for systems having small liquid mass flow rates. Additionally, it is found that the interfacial heat flux is predominantly determined by latent heat transfer connected with film evaporation.
Heterogeneous nucleation of organic vapours on a cold substrate
Authors: Shinagawa Hideo , Okuyama Kikuo , Kawamura Yuji
Published: March 2009

The heterogeneous phase transition of the organic vapours, cyclohexane and p‐xylene, on a cold substrate was observed by cooling the substrate at a slow rate under reduced pressure conditions. Either organic vapour at a vapour pressure lower than 130 Pa formed directly solid crystals but p‐xylene vapour at a higher vapour pressure formed liquid condensates with subsequent formation of solid crystals. The dependence of the critical supersaturation ratios on the critical temperatures and the physical properties of the organic vapours has been clarified by the equation derived on the basis of classical nucleation theory.
Effet de la pression sur la transition ruisselant‐pulsé dans les réacteurs catalytiques à lit fixe arrosé
Authors: Wild Gabriel , Midoux NoËL , Laurent AndrÉ , Larachi FaÏÇAl
Published: March 2009

Les modèles théoriques et corrélations empiriques existants actuellement sont incapables de prévoir correctement ľinfluence de la pression sur le déplacement de la transition entre les régimes ruisselant et pulsé (Trp) dans les réacteurs catalytiques à lit fixe arrosé (Rclfa). Basé sur les données disponibles à ce jour de la Trp à haute pression, le diagramme de Charpentier modifié que nous proposons ici, constitue un moyen direct pour quantifier ľeffet de la pression dans le cas de systèmes non‐moussants.
A systematic approach for the efficient estimation of interaction parameters in equations of state using binary vle data
Authors: Englezos Peter , Kalogerakis Nicolas , Raj Bishnoi P.
Published: March 2009

A systematic and computationally efficient approach for the estimation of the interaction parameters in equations of state using binary vapor liquid equilibrium (VLE) data is presented. Initially, the best set of interaction parameters is estimated by implicit least squares. Subsequently, the VLE calculations are performed using these parameters. Based on the quality of the fit it is decided whether these estimates suffice or implicit maximum likelihood estimation should be performed to obtain the statistically best values. Estimation subject to the liquid phase stability constraint is performed when erroneous phase behavior is computed. The approach is illustrated with typical examples.
Surface‐to‐suspension heat transfer model in lean gas–solid freeboard flow
Authors: Farag Ihab H. , Tsai Kun‐Yung
Published: March 2009

Heat transfer in dense fluidized beds have been extensively studied. However, there is not much detailed information about the mechanism of surface‐to‐suspension heat transfer in the freeboard region. In the present work, a newly designed heating plate was used to measure the plate‐surface‐to‐particle‐suspension heat transfer coefficients in the freeboard.The experimental unit consisted of a 30 cm i.d. fluidized bed reactor packed with fluidized catalytic particles of mean particle size 90 μm. Three types of plate orientations were used to test directional effects of surface on heat transfer rate. Height of the freeboard was 171 cm, and the superficial gas velocity was varied from 0.28 to 0.64 m/s. Local solids concentrations in the freeboard were also obtained by a nozzle‐type sampling probe. Data on axial distribution of solids concentration were used to find out the solids kinematics in the freeboard region. Finally, a surface‐to‐suspension heat transfer model was developed to elucidate the surface to particle heat transfer mechanism in this lean phase system.The model is based on the transient gas‐convective heating of single particles when sliding over the heating plate and the assumption of instantaneous attachment–detachment equilibrium between particles and the plate surface.
A new constrained self‐tuning pid controller
Authors: Katende Edward , Jutan Arthur
Published: March 2009

A new constrained self‐tuning PID controller is developed based on Clarke and Gawthrop's (1975) generalized minimum variance (GMV) controller. Convergence properties for the new algorithm are derived and the effect of the constraint parameter is evaluated. Extension of the controller to include more than the usual three PID parameters occurs naturally. No process model information is required for our algorithms except the dead time. This is an improvement over other algorithms which impose severe constraints on the process structure.

The controller algorithm is tested on a variety of models using simulation as well as under experimental conditions. The algorithm is easy to implement and compares favourably with the more complex GMV controller.