bluuebunny/crossref_metadata_2025_split huggingface dataset:
A generalised back‐flow model to predict the tracer response in liquid—liquid stagewise contactors
Authors: Das Parichay K. 
Published: March 2009

AbstractA generalized transient back‐flow model to predict the transient tracer concentration in a multistage extraction column has been developed. The model does not assume any extra stage at the end of the contactor and is based on unified formulation. The solution can be obtained in a straight forward way by using the linear operator theoretic approach as opposed to Laplace transform.
Interstage backmixing of an aerated multistage, mechanically‐agitated, compartmented column
Authors: Takriff Mohd Sobri , Penney W. Roy , Fasano Julian B. 
Published: March 2009

AbstractThe interstage backmixing in a multistage, mechanically‐agitated, compartmented (MSAC) column was determined experimentally, using air‐water. The effects of impeller speed, impeller diameter and both superficial liquid velocity and superficial gas velocity through the interstage opening were investigated. Both the counter‐current and co‐current flow of air and water in the column were investigated. As air superficial velocity through the opening increased from zero, the interstage backmixing significantly decreased initially, reached a minimum, then increased slowly to a maximum after which it decreased continually with further increase in superficial gas velocity. The effect of the gas flow on interstage backmixing was correlated in dimensionless form.
Turbulence in stirred tanks: Anisotropic, approximate, and applied
Authors: Kresta Suzanne 
Published: March 2009

AbstractOver the last ten years, many ways of characterizing the turbulence in stirred tanks have been proposed, and the importance of the local rate of dissipation of turbulent kinetic energy (ϵ) to various processes has been clarified. In this paper, our understanding of the role of ϵ is examined for the blend time of miscible fluids, for drop break‐up, for reactor design, for cell damage in bioreactors, for gas dispersion, for crystallization, and for flocculation and coagulation. The conceptual difficulties inherent in approximate measurements of ϵ are discussed with examples and background theory. Particular attention is paid to the various length and time scales present in the tank, the anisotropic nature of the flow field, and the effect of organized structures on turbulence measurements. Progress in the area over the last ten years is reviewed in the context of these limitations.
Theoretical investigation into instability of a refrigeration system with an evaporator controlled by a thermostatic expansion valve
Authors: Ibrahim Ghaleb A. 
Published: March 2009

AbstractA theoretical model is developed and solved to investigate the instability of a refrigeration system with an evaporator controlled by a thermostatic expansion valve. An evaporator time constant is used to account for the delay of the liquid refrigerant distribution along the two phase region. Results show that there is an evaporator critical time constant, below which the system operates in a stable manner. This critical time constant is found to decrease with decreasing the partial load and to increase with increasing the contact thermal resistance and the two‐phase region heat transfer coefficient. The bulb size is also found to have a great effect on the stability.
Kinetics of fructose‐glucose isomerization with sweetzyme type A
Authors: Bravo V. , Jurado E. , Luzón G. , Cruz N. 
Published: March 2009

AbstractA study has been made of the kinetics of fructose‐glucose enzymatic isomerization with an immobilized glucose isomerase, Sweetzyme A, at 60°C and with initial fructose concentrations of between 0.1 and 2.0 M. In the kinetic study, the effects of internal and external transport were considered, and it was found that when the data were fitted to a kinetic of a pseudo‐first‐order type, the non‐enzymatic reaction could not be disregarded at low enzyme and high substrate concentrations. When non‐enzymatic isomerization is taken into account, the true enzymatic‐reaction constant can be calculated, giving values for maximum rate of 1.39 · 10−6 mol (kg·s)−1 and for Michaelis‐Menten constant of 1.24 M. Establishing the influence of the transport in the interior of the catalyzing particles has enabled the determination of a value for effective diffusivity of 0.59 · 10−10 m2·s−1.
Viscous and yield stress properties of athabasca topped heavy oil
Authors: De Kee Daniel , Chornet Esteban , Zhang Wenqi 
Published: March 2009

AbstractThis contribution reports on a study of the rheological behavior of Athabasca topped heavy oil as a prototype oil derived from western Canadian bitumen. Mixtures of crudes with additives such as pentane and toluene are studied. Data obtained using three different rheometers superpose rather well. Observed non‐Newtonian behavior was successfully modeled by a simplified equation, derived from a model proposed by De Kee and Chan Man Fong (1994). Yield stress data were determined using a technique which does not involve extrapolation. Both yield stress as well as viscosity data obey Arrhenius type relations over the temperature range studied.
Liquid—liquid equilibria of ternary ETBE‐ETOH‐H2O and quaternary ETBE‐ETOH‐H2O‐TBA mixtures
Authors: Quitain A. T. , Goto S. 
Published: March 2009

AbstractLiquid‐liquid equilibria of ETBE‐EtOH‐H2O mixtures are measured at 15,25 and 35°C. UNIQUAC and NRTL equations are fitted to the experimental data using ASPEN PLUS. Both the experimental and correlated values of the equilibrium compositions are compared with the values predicted by UNIFAC method. The same procedure is extended to quaternary ETBE‐EtOH‐H2O‐TBA system at low TBA concentration.
Predictions on bubble and solids movement in laboratory polyethylene fluid beds as visualized by X‐ray computer assisted tomography (CAT) scanning
Authors: Zarabi Taghi , Kantzas Apostolos 
Published: March 2009

AbstractSolid and gas distributions are tomographically quantified as a function of position with high resolution in a series of laboratory fluid beds containing air and polyethylene particles. The resolution used is 0.4 mm by 0.4 mm by 3 mm. The laboratory models are Plexiglas columns of 10 cm in diameter and the settling bed L/D ratios vary between one and three. Large particles (up to 1.5 mm in diameter) of high density polyethylene and linear low density polyethylene are used. The superficial gas velocities vary from the minimum fluidization velocity to 50 cm/s. In this paper, the analysis of fluid bed CAT scanner images is extended to show bubble, emulsion and dense phase distribution. The analysis is also used to determine the bubble diameter and to predict the flow direction of solid particles as well as the velocity of descending solids. The voidage frequency distributions of a bed at different gas flow rates are compared to each other and the voidage threshold values corresponding to gas, emulsion and dense phases are determined. These threshold values are used to prepare ternary images that clearly show the parts of the bed cross‐section corresponding to bubble, emulsion and dense phases.
Enhancement of mass transfer in flow channels under thermal gradients
Authors: Bendrich Guido , Shemilt Leslie W. 
Published: March 2009

AbstractOverall mass transfer coefficients, at the solid liquid interface in a rectangular cross‐section flow reactor, were obtained using the limiting current technique. Empirical correlations were developed for single‐phase flow for a full range of surface configurations, for laminar and turbulent flow regimes, and for isothermal and non‐isothermal conditions. Isothermal mass transfer was almost doubled by the selection of the reactor slope and surface configuration. Imposition of up to a 30°C difference at the interface, enhanced mass transfer approximately four times, over the isothermal case. Mathematical simulation for mass transfer in flow reactors, is shown to agree within 15% of experimental values found in the literature and for the experiments reported here.
Mass transfer from spherical particles and reservoirs into quiescent liquids
Authors: Doan Huu D. , Trass Olev , Fayed Muhammad E. 
Published: March 2009

AbstractA continuous weighing technique was developed for measuring urea transfer (carbamide, a fertilizer) from a single opening on a coated sphere in a stagnant liquid. Urea release was determined from the changes of the particle weight with time. Mass transfer coefficients for Rayleigh numbers from 1.8 × 107 to 6.8 × 1010 were measured and compared with those for uncoated urea spheres and literature data. For the opening oriented vertically upward in water, natural convection enhanced the transfer rate by 1.8 times compared to that for urea diffusion only. In other opening orientations (45°, 90°, 135° and 180° to the vertical), natural convection provided the major mechanism for the release. A model for urea diffusion was also developed. It agrees well with experimental data.
A numerical study of the accelerating motion of a dense rigid sphere in non‐newtonian power law fluids
Authors: Chhabra Rajendra P. , Soares Armando A. , Ferreira Jose M. 
Published: March 2009

AbstractThe equations of motion of an accelerating sphere falling through non‐Newtonian fluids with power law index n in the range 0.2 ≤ n ≤ 1.8 were integrated numerically using the assumption that the drag on the sphere was a function of both power law index and terminal Reynolds number, Ret For 10−2 ≤ Ret ≤ 103 both dimensionless time and distance travelled by the sphere under transient conditions showed a much stronger dependence on the flow behaviour index, n, for shear‐thinning than for shear‐thickening fluids. The form of this dependence is investigated here. Furthermore, results in four typical shear‐thinning fluids suggested a strong correlation between the distance and time travelled by the sphere under transient conditions and the value of the fluid consistency index. The analysis reported herein is, however, restricted to dense spheres falling in less dense fluids, when additional effects arising from the Basset forces can be neelected.
Dynamic modelling of consecutive reactions: Application to the acrylonitrile amination
Authors: Kadri Brahim , Fabre Bernard , Accary Armand , Kessler Mathieu 
Published: March 2009

AbstractWhen dealing with optimal control problems to maximize the selectivity of reactions for fine chemical synthesis, representative kinetic and thermodynamic models should be available. While literature appears to be very extensive on theoretical approaches to solve the problem, examples presenting complete models of chemical transformations are scarce. This paper presents the identification of consecutive reactions carried out in a batch reactor. Material and energy balances, satisfying dynamical state evolutions in the temperature range 20‐60°C are deduced, for concentrations of acrylonitrile ranging up to 1.6 kmol·m−3. The stoichiometric network is simplified into two reactions, one reversible and one irreversible. Reaction enthalpies are measured from isothermal runs conducted in the RC1 heat‐flow calorimeter from Mettler Toledo.
Effect of pulp fibres on gas holdup in a flotation column
Authors: Janse Peter , Gomez Cesar O. , Finch James A. 
Published: March 2009

AbstractColumn flotation is an emerging technology in the deinking of recycled paper. Deinking efficiency depends primarily on the effect of four physical variables: gas and accepts flowrates, bubble size distribution, and pulp consistency. Experiments to establish operating ranges for these variables by determining their effect on gas holdup were conducted in a laboratory column installed at Bowater's Gatineau (Quebec) mill which processes a pulp (70% ONP/30% OMG) with about 1% consistency. The results showed the general trends expected from a review of previous studies: gas holdup increases with gas and accepts flowrates and with smaller bubble size, and decreases for higher pulp consistencies. However, the review also demonstrated that the published information is of limited application as the bubble size was much larger than that encountered in industrial flotation practice, primarily because of the use of pure water. Industrial pulps contain in most cases surface active agents which have a substantial effect on forming and preserving a small size bubble population.
An investigation of heat transfer from a vertical tube in a spouted bed
Authors: Macchi Arturo , Bi Hsiaotao T. , Legros Robert , Chaouki Jamal 
Published: March 2009

AbstractAn experimental investigation on heat transfer from a vertical tube in a gas—solid spouted bed has been conducted. Values of heat transfer coefficients (hs) have been found to vary between 95 and 230 W/m2°C. Maximum values of hs are always at the spout axis and decrease monotonically towards the column wall. The drop is most important at the spout‐annulus boundary. Most of the effects from different parameters can be explained by the flow patterns of the gas, although particle convection still contributes to some extent to the heat transfer rate. Equations correlating hs in the spout and the annulus have been developed.
The futility of raffinate reflux revisited
Authors: Rao D. P. 
Published: March 2009

AbstractThe role of reflux in equilibrium separation processes has been examined from a mechanistic viewpoint. The raffinate reflux — presaturation of solvent with raffinate in a separate unit (presaturator) — has been demonstrated to be futile in the past, considering the stages to be ideal. We have examined the utility of raffinate‐like reflux in all the equilibrium separation processes. The nature of mass transfer in these processes with and without presaturator and its implications in the design and analysis have been presented.
Treatment of industrial wastewater using zeolitite and sepiolite, natural microporous materials
Authors: Brigatti Maria Franca , Frigieri Paola , Gardinali Christian , Medici Luca , Poppi Luciano , Franchini Giancarlo 
Published: March 2009

AbstractThis work investigates the ability of natural microporous materials, such as a zeolite‐rich tuff (zeolitite) and a modulated phyllosilicate (sepiolite), to remove heavy‐metal ions from simulated inorganic polluted industrial wastewater. Fixed beds of sepiolite and zeolitite were percolated by a solution of Co2+, Cu2+, Zn2+, Cd2+, and Pb2+ (concentration of each cation, 2 ⊗ 10−3 N; total concentration, 10−2 N) and were regenerated with a 2 ⊗ 10−3 N Na+ solution. The order of decreasing affinity was, for sepiolite: Cu2+ > Zn2+ > Cd2+ > Pb2+ ≅ Co2+, and, for zeolitite: Pb2+ “Cd2+ > Cu2+ > Zn2+ > Co2+. After regeneration with Na+ solution, a fraction of the retained heavy metals was quickly released by the beds as follows: sepiolite, Co2+ ≅ Pb2+ > Cd2+ > Zn2+ > Cu2+; zeolitite, Cd2+ > Cu2+ ≅ Zn2+ > Co2+ > Pb2+. XRD and DTA‐TGA analyses examined structural changes in the natural and final materials.
Resination and decarboxylation reactions in fusion synthesis of ca‐resinates
Authors: Sundqvist Satu , Paatero Erkki , Tenhola Harri 
Published: March 2009

AbstractThe reaction steps in fusion synthesis of Ca‐resinates include a fast, irreversible resination reaction and a slow decarboxylation of rosin acids. The kinetics of the reactions was studied separately in a laboratory scale batch reactor. The kinetic data were obtained by acid number titrations and FTIR measurements. Resination was observed to be a fast irreversible reaction in the temperature range 190 to 235°C. Rate equations for the decarboxylation reaction were derived based on plausible mechanistic reaction steps of free and solvating rosin acids. The parameters of the rate equations were estimated for syntheses at different reaction temperatures (265 to 285°C) and the kinetic model was successfully applied to predict the experimental kinetics of rosin acid decarboxylation.
Pressure and voidage fluctuations in slugging fluidized beds
Authors: Bi Hsiaotao 
Published: March 2009

AbstractIn fully developed slugging fluidized beds, the maximum amplitude of absolute pressure fluctuations is reached with increasing superficial gas velocity when the slug length reaches a maximum, and the separation distance between successive slugs starts to decrease. Uc, the superficial gas velocity at which absolute pressure fluctuations reach a maximum, thus indicates the early stage of transition from slugging to core‐annular flow. Uc, identified based on standard deviations of differential pressure fluctuations or local voidage fluctuations, can be predicted by slug flow models and does not signify a transition to turbulent fluidization.
CFD modeling of flow, macro‐mixing and axial dispersion in a bubble column
Authors: Thakre Shirish S. , Phanikumar Docca V. , Khare Ashok S. , Joshi Jyeshtharaj B. 
Published: March 2009

AbstractThe flow pattern in a bubble column depends upon the column diameter, height, sparger design, superficial gas velocity and the nature of gas–liquid system. In this paper, the effect of some of these parameters have been simulated using Computational Fluid Dynamics (CFD). The relationship of these parameters with the interphase force terms has been discussed. A complete energy balance has been established. Using this methodology, the flow patterns reported by Hills (1974), Menzel et al. (1990), Yao et al. (1991) and Yu and Kim (1991) have been simulated. Excellent agreement has been shown between the CFD predictions and the experimental observations. The above model has been extended to homogenization of an inert tracer. In order to confirm this model, mixing experiments were carried out in a 200 mm i.d. bubble column. A radioactive tracer technique was used for the measurement of mixing time. Tc‐99m (99m Tc), in the form of sodium pertechnate salt, was used as the liquid phase tracer. Good agreement has been shown between the predicted and the experimental values of mixing time. The model was further extended for the estimation of axial dispersion coefficient (DL). Excellent agreement between the simulated and the experimental values of the axial dispersion coefficient confirms the predictive capability of the CFD simulations for the mixing process.
Détermination électrochimique du nombre de sherwood minimum pour un milieu macro‐poreux (fritté — lit fixe de grains)
Authors: Vilar Eudésio Oliveira , Coeuret FrançOis 
Published: March 2009

AbstractLe travail applique la méthode électrochimique de mesure des coefficients de transfert de matiére solide/liquide à la recherche expérimentale de la valeur du nombre de Sherwood pour le transfert stationnaire de matière par diffusion moléculaire entre un matériau poreux et un liquide contenu dans ses pores. Ce nombre de Sherwood minimum est déterminé pour le cas des frittés et pour celui des lits fixes de grains sphériques. Les aspects théoriques s'appuient sur l'analogie du problème considéré avec celui de la compétition entre diffusion moléculaire et réaction chimique hétérogene dans les catalyseurs poreux.
Growth of Rhizobium leguminosarum on peat in rotating bioreactors
Authors: Jauhari Ritika , Gray Murray , Holloway Greg 
Published: March 2009

AbstractThe legume inoculant Rhizobium leguminosarum was grown on peat in roller bottles and a rotating drum bioreactor. Growth conditions were first determined using experiments in roller bottles. The best growth rate and cell count were obtained with peat containing 40% moisture (wet basis) and a volume fraction of moist peat of 0.3 in the roller bottle bioreactors. A cell count of 1.3 to 1.9 × 109 CFU/g was achieved in 4 d or less, from an initial inoculum of 106 CFU/g. In a rotating drum bioreactor, the growth of R.leguminosarum on peat with sucrose as the main carbon source was completed after 4 d. The majority of growth was in the first 2 d, based on carbon dioxide evolution. These results showed that growth of R. leguminosarum was more rapid in the rotating drum than in bags of peat, due to enhanced oxygen transfer.
Amino acids profiles in a ph‐auxostat
Authors: Lin Yen‐Han , Ji Wei 
Published: March 2009

AbstractThe proportions of amino acids changed dramatically in a pH‐auxostat as the dilution rate was increased by feeding a medium with a low buffering capacity. A brief period of auxostatic culturing converts an elective mixed culture to a nearly pure culture, and this selection is accelerated by lowering the buffering capacity. As the specific growth rate was increased, the organisms utilized some of amino acids partially and/or completely, while others were essentially unchanged or even enriched. Such an enrichment effect was greatest at the highest specific growth rate.
Biodegradation and detoxification of wood leachate from pentachlorophenol‐treated poles
Authors: Mollah A. Hamid , Allen D. Grant 
Published: March 2009

AbstractThe pentachlorophenol (PCP) in leachate, generated from size‐reduced PCP‐treated poles, was degraded using a mixed culture containing Arthrobacter sp. in cyclic batch bioreactors in non‐sterile conditions. Complete degradation of PCP was achieved for a five‐month period for a concentration of 50 mg PCP/L and 12 h cycle time. The adsorbable organic halogen (AOX) concentration of the reactor effluent was reduced by two orders of magnitude compared to the feed, and the chemical oxygen demand (COD) was reduced by 50%. The increase in chloride ion concentration also suggests that PCP was mineralized to end products. In tests to increase the process throughput, complete degradation of PCP was also achieved in the cases for 120 mg PCP/L and a 12 h cycle time or 50 mg PCP/L and a 6 h cycle time. Daphnia magna toxicity tests showed that the presence of PCP in leachate caused toxicity, and the biodegradation of PCP resulted in significantly reducing the effluent toxicity to a value similar to that of PCP‐free nutrient solution.
Sequencing batch reactor technology for the purification of concentrated dyehouse liquors
Authors: Hemmi Martin , Krull Rainer , Hempel Dietmar C. 
Published: March 2009

AbstractA sequencing batch reactor (SBR) technology for the purification of concentrated reactive azo‐dye containing residual dyehouse liquors from a padding process was developed and investigated. Within the treatment cycle, the anoxic dye cleavage, the aerobic mineralization of organic compounds, in combination with the biodegradability‐achieving partial oxidation with ozone, are carried out sequentially. Anoxic decolourization of the residual liquor without addition of an auxiliary substrate was observed, and a 90% biological degradation of the dyehouse liquor's recalcitrant organic compounds was achieved. COD decreased by 95% and AOX (adsorbable organohalogenic compounds) by 90%. Within the whole process, the colour of the concentrated wastewater decreased by 98%.
Continuous separation of suspensions containing light and heavy particle species
Authors: Nasr‐El‐Din Hisham A. , Masliyah Jacob H. , Nandakumar Krishnaswamy 
Published: March 2009

AbstractContinuous separation of bidisperse suspensions containing particles of significantly different size and density in a vertical settler was examined. The effects of the feed total solids volume fraction, composition, and flow rate on the performance of the settler were investigated. For feed total solids volume fractions less than 0.1, a kinematic model based on the Patwardhan and Tien (1985) expression for relative velocity was found to predict the experimental measurements fairly well over a wide range of parameters. For feed total solids volume fractions greater than 0.2, a strong local instability was observed in the settler. This local instability significantly improved the performance of the settler in some cases.