bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractExperimental 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

AbstractSimultaneous 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

AbstractAccurate 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

AbstractAn 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

AbstractA 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

AbstractConditions 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

AbstractRates 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

AbstractA 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

AbstractDirect 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

AbstractA 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

AbstractThe 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

AbstractExtractive 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

AbstractThe 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

AbstractThe 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

AbstractA 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.
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

AbstractLong 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

AbstractCombustion 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

AbstractIncorporation 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

AbstractThe 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

AbstractLiquid 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

AbstractProcesses 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

AbstractThis 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

AbstractWhen 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

AbstractThis 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

AbstractAn 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

AbstractA 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.