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Showing papers in "Canadian Journal of Chemical Engineering in 2009"


Journal ArticleDOI
TL;DR: In this paper, the authors proposed a method for adjusting the Di Felice drag law in a multi-fluid model of FLUENT V6.3.26 (FLUENT, 2007).
Abstract: In computational fluid dynamics modelling of gas-solid two phase flow, drag force is one of the dominant mechanisms for interphase momentum transfer. Despite the profusion of drag models, none of the available drag functions gives accurate results in their own original form. In this work the drag correlations of Syamlal and O'Brien (Syamlal and O'Brien, Int. J. Multiphase Flow. 1988; 14(4):473-481), Gidaspow (Gidaspow, Appl. Mech. Rev. 1986; 39:1-23), Wen and Yu (Wen and Yu, Chem. Eng. Prog. Symp. Ser. 1966; 62(2):100-111), Arastoopour et al. (Arastoopour et al., Powder Technol. 1990; 62(2): 163-170), Gibilaro et al. (Gibilaro et al., Chem. Eng. Sci. 1985; 40:181 7-1823), Di Felice (Di Felice, Int. J. Multiphase Flow. 1994; 20(1):153-159), Zhang-Reese (Zhang and Reese, Chem. Eng. Sci. 2003; 58(8):1641-1644) and Hill et al. (Hill et al., J. Fluid Mech. 2001; 448:243-278) are reviewed using a multi-fluid model of FLUENT V6.3.26 (FLUENT, 2007. Fluent 6.3 User's Guide, 23.5 Eulerian Model, Fluent, Inc.) software with the resulting hydrodynamics parameters being compared with experimental data. The main contribution of this work is to propose an easy to implement and efficient method for adjustment of Di Felice drag law which is more efficient compared to the one proposed by Syamlal-O'Brien. The new method adopted in this work showed a quantitative improvement compared to the adjusted drag model of Syamlal-O'Brien. Prediction of bed expansion and pressure drop showed excellent agreement with results of experiments conducted in a Plexiglas fluidized bed. A mesh size sensitivity analysis with varied interval spacing showed that mesh interval spacing with 18 times the particle diameter and using higher order discretization methods produces acceptable results.

108 citations


Journal ArticleDOI
TL;DR: In this paper, a model based on the film theory is used to predict the rate of absorption of CO/sub 2/ into mixed amine solutions, which accounts for the variation of amine concentration in the film.
Abstract: Absorption rates for CO/sub 2/ into aqueous solutions of TEA, MDEA and blends of MEA with MDEA and TEA were measured in a stirred cell by a method similar to that used. Second-order rate constants for CO/sub 2/- TEA and CO/sub 2/-MDEA were obtained for temperatures in the range 25-60{sup 0}C. A model based on the film theory is used to predict the rate of absorption of CO/sub 2/ into mixed amine solutions. This model accounts for the variation of amine concentration in the film. Bulk liquid concentrations of the various species present are obtained from a simplified thermodynamic model. Predicted rates are in reasonable agreement with measurements.

101 citations


Journal ArticleDOI
TL;DR: In this paper, the true kinetics of methane steam reforming was measured in powder of Ni/Al 2 O 3 catalyst ("Octolyst 1001" from Degussa) at different temperatures (733-890 K) for several operating conditions.
Abstract: The true kinetics of methane steam reforming was measured in powder of Ni/Al 2 O 3 catalyst ("Octolyst 1001" from Degussa) at different temperatures (733-890 K) for several operating conditions. New reaction rate constants were determined for this catalyst. The observed reaction rate was measured on catalyst extrudates to determine diffusion effects within the porous structure of the particle. A non-isothermal model with diffusion was used to determine effectiveness factors for each reaction. The objective was to measure all necessary data to model the performance of the catalyst in a Sorption Enhanced Reaction Process (SERP) for H 2 production with in situ CO 2 capture.

85 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the affinity of clay minerals in oil sands for the water-continuous tailings and hydrocarboncontinuous froth streams produced from the extraction of bitumen from oil sands.
Abstract: This study investigates the affinity of clay minerals in oil sands for the water-continuous tailings and hydrocarbon-continuous froth streams produced from the extraction of bitumen from oil sands. Clay minerals in oil sands processing impact bitumen flotation in separation vessels, emulsion formation during froth treatment, and fine tailings behaviour. X-ray diffraction of oriented clay slides and random powder samples were used to quantify the clay minerals in the oil sands ore and process streams. Particle size distribution and clay activity balances were also conducted around the extraction process. The degree of partitioning during the conditioning and flotation stages in a batch extractor was determined by the surface properties of the clay minerals present. The water-continuous tailings stream was further separated into fine and coarse tailings fractions through sedimentation. The bulk of the clay minerals reported to the fine tailings stream. Illite and mixed layered illite-smectite partitioned less to the hydrocarbon-continuous froth than kaolinite. Also, the illite-smectite in the froth stream appeared to be different from the illite-smectite in the water continuous streams. On a etudie dans ce travail l'affinite des mineraux argileux dans les sables bitumineux pour les courants de residus continus dans l'eau et les courants d’ecume continus dans les hydrocarbures produits par l'extraction de bitume des sables bitumineux. Les mineraux argileux dans le traitement des sables bitumineux ont un impact sur la flottation du bitume dans les cuves de separation, la formation des emulsions lors du traitement de l'ecume et le comportement des residus. La diffraction X de preparation microscopique d'argile orientee et des echantillons de poudres aleatoires ont ete utilises pour quantifier les mineraux argileux dans le minerai de sables bitumineux et les courants de procedes. La distribution de taille des particules et les bilans d'activite de l'argile ont egalement ete determines autour du procede d'extraction. Le degre de separation durant les etapes de conditionnement et de flottation dans un extracteur discontinu a ete determine par les proprietes de surface des mineraux argileux presents. Le courant de residus continus dans l'eau a ensuite ete separe en fractions de residus fins et grossiers par sedimentation. La grande partie des mineraux argileux se retrouve dans le courant de residus fins. L'illite et l'illitesmectite en couches melangees se separent moins de l'ecume continue dans les hydrocarbures que la kaolinite. Par ailleurs, l'illitesmectite dans le courant d'ecume semble etre differente de l'illitesmectite dans les courants d'eau continus.

72 citations


Journal ArticleDOI
TL;DR: In this paper, the removal of chromium from aqueous solution by nanoparticles of iron was studied and the process of removal was governed by first and pseudo-second-order kinetic equations and their rate constants were determined.
Abstract: Due to rapid industrialisation, the presence of heavy metals in water and wastewater is a matter of environmental concern. Though some of the metals are essential for our system but if present beyond their threshold limit value (TLV), they are harmful and their treatment prior to disposal becomes inevitable. The present communication has been addressed to the removal of Cr(VI) from aqueous solutions by nanoparticles of iron. Nanoparticles of iron were prepared by sol-gel method. The characterisation of the nanoparticles was carried out by XRD and TEM analysis. Batch experiments were adopted for the adsorption of Cr(VI) from its solutions. The effect of different important parameters such as contact time and initial concentration, pH, adsorbent dose, and temperature on removal of chromium was studied. The removal of chromium increased from 88. 5% to 99.05% by decreasing its initial concentration from 15 to 5 mg L -1 at optimum conditions. Removal of Cr(VI) was found to be highly pH dependent and a maximum removal (100%) was obtained at pH 2.0. The process of removal was governed by first and pseudo-second-order kinetic equations and their rate constants were determined. The process of removal was also governed by intraparticle diffusion. Values of the thermodynamic parameters viz. ΔG°, ΔH°, and ΔS° at different temperatures were determined. The data generated in this study can be used to design treatment plants for chromium rich industrial effluents. Adsorption results indicate that nanoiron particles can be effective for the removal of chromium from aqueous solutions.

71 citations


Journal ArticleDOI
Mostafa Mahmoud1
TL;DR: In this article, the influence of radiation and temperature-dependent viscosity on the problem of unsteady MHD flow and heat transfer of an electrically conducting fluid past an infinite vertical porous plate taking into account the effect of viscous dissipation was investigated.
Abstract: This article investigates the influence of radiation and temperature-dependent viscosity on the problem of unsteady MHD flow and heat transfer of an electrically conducting fluid past an infinite vertical porous plate taking into account the effect of viscous dissipation. The governing equations are converted into a system of nonlinear ordinary differential equations via a local similarity parameter which is taken as a function of time. The resulting system of coupled nonlinear ordinary differential equations is solved numerically using the fourth order Runge-Kutta integration scheme with the shooting method. The numerical results for the velocity and the temperature are displayed graphically showing the effects of various parameters. The results show that increasing the Eckert number and decreasing the viscosity of air leads to a rise in the velocity, while increasing in the magnetic or the radiation parameters is associated with a decrease in the velocity. Also, an increase in the Eckert number leads to an increase in the temperature, whereas an increase in radiation parameter leads to a decrease in the temperature.

69 citations


Journal ArticleDOI
TL;DR: Agglomeration is a major problem in biomass-fired fluidized bed combustors and gasifiers as discussed by the authors, and it can be classified broadly into three types: defluidization induced, melt-induced and coating-induced agglomerations.
Abstract: Agglomeration is a major problem in biomass fired fluidized bed combustors and gasifiers. Mechanism, reduction options and detection techniques of agglomeration are reviewed. Agglomeration may be classified broadly into three types: defluidization induced agglomeration, melt-induced agglomeration and coating-induced agglomeration. Sodium and potassium content of the biomass are the major contributors to the agglomeration in biomass fired fluidized beds. Higher temperature, lower fluidizing velocity and coarser bed particles also increase the risk of agglomeration. Alternative bed materials, additives or the co-combustion of biomass with other fuels can reduce agglomeration potential of a fluidized bed. Two agglomeration detection techniques are discussed: controlled fluidized bed agglomeration and early agglomeration recognition system.

69 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of the interparticle interaction on the bed dynamics, by considering a variable restitution coefficient, was studied by using an extended discrete element model (DEM).
Abstract: In this article we study the effect of the inter-particle interaction on the bed dynamics, by considering a variable restitution coefficient. The restitution coefficient is varied in time and space depending on the moisture content due to the particle-droplet interaction and evaporation. This study is done computationally, by using an extended discrete element model (DEM). The examined flow regimes comprise the intermediate/spout-fluidization regime (B1), spouting-with-aeration regime (B2) and the jet-in-fluidized-bed regime (B3). For all flow regimes, the averaged bed height increases with decreasing restitution coefficient. Moreover, the averaged bed height for a variable restitution coefficient is larger for all flow regimes compared to a case with a constant restitution coefficient, indicating that the distribution of the restitution coefficient influences the bed dynamics. The effect of evaporation on the distribution of the restitution coefficient is only observed for the jet-in-fluidized-bed regime (B3), where the background velocity is relatively high leading to enhanced evaporation from the particles in the annulus region. This is reflected in the averaged bed height for the evaporation test case, which is larger compared to a test case without evaporation. A larger bed height for cases with variable restitution coefficient is due to the pressure build up in the spout region caused by the longer closing period of the spout channel. This is confirmed by the recorded pressure fluctuation signal and its root mean square which are larger for the cases with the variable restitution coefficient.

66 citations


Journal ArticleDOI
TL;DR: In this article, the patterns of solids and gas flows in a spouted bed were numerically simulated using the 3D Eulerian multiphase model and the minimum spouted condition was identified by the simulated solids volume fraction and pressure profiles.
Abstract: Numerical simulation using computational fluid dynamics (CFD) technique associated with experimental verification is a useful tool for analysis of gas-solid multiphase flows. Simulations of the spouted bed fluid dynamic using two-dimensional computational grids were accomplished in our previous works with good results. In this article, the patterns of solids and gas flows in a spouted bed were numerically simulated using the three-dimensional (3D) Eulerian multiphase model. The minimum spouted condition was identified by the simulated solids volume fraction and pressure profiles. The simulated results show good agreement with experimental data and higher accuracy when compared with 2D simulations.

62 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of manganese and potassium promoters on the performance of iron catalysts for hydrogenation of carbon dioxide was investigated, and it was shown that the distribution of hydrocarbon products did not change significantly in the presence of a new promoteur, while the selectivity toward olefins and long chain hydrocarbons was remarkably enhanced.
Abstract: The effect of addition of manganese and potassium promoters onto iron catalysts for hydrogenation of carbon dioxide was investigated. Catalyst characterizations were performed using BET surface area measurement, carbon monoxide chemisorption, temperature-programmed reduction and Mossbauer spectroscopy. It was noted that metallic iron catalysts were carburized to θ-Fe3C and χ-Fe5C2 as well as oxidized to Fe3O4 during the course of reaction. The promotional effect of manganese was reflected in stabilization of catalytic behavior owing to a higher resistance to bulk oxidation. However, the distribution of hydrocarbon products did not change significantly in the presence of manganese promoter. With further addition of potassium promoter, the bulk phase was more likely to transform to carbides, and the selectivity toward olefins and long-chain hydrocarbons was remarkably enhanced. On a etudie l'effet de l'ajout de promoteurs au manganese et potassium sur des catalyseurs de fer pour l'hydrogenation du gaz carbonique. La caracterisation des catalyseurs a ete realisee par une mesure BET de la zone de surface, la chimisorption de l'oxyde de carbone, une reduction a temperature programmee et la spectroscopie Mossbauer. On a remarque que les catalyseurs de fer metallique sont cementes en θ-Fe3C et χ-Fe5C2 et qu'ils sont oxydes en Fe3O4 lors de la reaction. L'effet promotionnel du manganese se reflete dans la stabilisation du comportement catalytique en raison d'une plus haute resistance a l'oxydation en masse. Cependant, la distribution des hydrocarbures ne change pas de facon significative en presence du promoteur au manganese. Avec un nouvel ajout de promoteur de potassium, la phase principale est plus susceptible de se transformer en carbures, et la selectivite vers les olefines et les hydrocarbures de chai'nes longues est remarquablement amelioree.

57 citations


Journal ArticleDOI
TL;DR: Equilbrium isotherms are reported for adsorption of water vapour on several different activated alumina adsorbents in this article, which conform closely to simple idealized models, thus providing a rational basis on which to compare different samples and the effects of different regeneration procedures.
Abstract: Equilbrium isotherms are reported for adsorption of water vapour on several different activated alumina adsorbents. The experimentally measured isotherms represent the sum of the contributions from water vapour held in several ways but these contributions can be resolved by detailed analysis. The individual isotherms conform closely to simple idealized models (Langmuir for chemisorption, BET for physisorption), thus providing a rational basis on which to compare different samples and the effects of different regeneration procedures. The apparent complexity in the behaviour of these systems arises from the superposition of the different contributions, the relative importance of which depends upon the nature of the sample and the regeneration conditions. By contrast, the behaviour of the resolved isotherms is relatively straightforward.

Journal ArticleDOI
TL;DR: A mathematical model based on the diffusion of nutrients is developed by considering the physiological changes accompanying the growth of avascular tumour and is validated using in vitro tumour growth data and Gompertzian empirical relationship parameters available in the literature.
Abstract: In this paper, a mathematical model based on the diffusion of nutrients is developed by considering the physiological changes accompanying the growth of avascular tumour. Avascular tumour growth involves the formation of three different zones namely proliferation, quiescent and necrotic zones. The main processes on which avascular tumour growth depends are: (i) diffusion of nutrients through the tumour from the contiguous tissues, (ii) consumption rate of the nutrients by the cells in the tumour, and (iii) cell death by apoptosis and necrosis. In the model, we consider the tumour to be spherical and the principal nutrients responsible for its growth are oxygen and glucose. By solving for the concentration profiles using the model developed, we are able to compute the radii of the quiescent and necrotic zones as well as that of the tumour. The proposed model is also validated using in vitro tumour growth data and Gompertzian empirical relationship parameters available in the literature. Our model is also successful in capturing the saturated volume of the avascular tumour for different nutrient concentrations at the tumour surface.

Journal ArticleDOI
TL;DR: In this article, the influence of the gas flow rate (GFR) on the conversion, the elimination capacity (EC) and the carbon dioxide production, during the biofiltration of methane using a biofilter charged with an inorganic packing material, has been investigated.
Abstract: The influence of the gas flow rate (GFR), when varied between 1 and 5.5 L/min, on the conversion, the elimination capacity (EC) and the carbon dioxide production , during the biofiltration of methane using a biofilter charged with an inorganic packing material, has been investigated. The methane concentrations considered for this purpose were selected from the operating range of 1300–12 000 ppmv. The experiments involved were conducted, using a nitrogen minimal salt nutrient solution, for the biofilter periodic irrigation, in which the nitrogen concentration was maintained at 0.75 g/L, and the phosphorus concentration was of 0.3 or 1.5 g/L. The results obtained from this study have confirmed the view that the GFR is a important parameter, the optimum values found, leading to methane conversions of ≥90%, being ≤2 L/min for inlet loads ≤55 g/m3/h. Based on this result, it was then established that the maximum volumetric load (VL) of methane in the biofilter must be estimated at around 0.075 m3 (methane)/m3 (biofilter)/h, that is, 6.8 m3 (polluted gas)/m3 (biofilter)/h. In addition, when the GFR is selected between 1 and 4.2 L/min, it has an influence on the EC. However, the GFR does not affect the within the biofilter. It has also been established that the high phosphorus level (i.e., 1.5 g/L), present in the nutrient solution, is to be preferred in the biofilter. Lors de la biofiltration du methane utilisant un biofiltre garni avec un materiau inorganique, l'influence du debit de la phase gazeuse, lorsque varie entre 1 et 5.5 L/min, sur la conversion, la capacite d'elimination ainsi que la production de dioxyde de carbone a ete etudiee. Les concentrations de methane ont ete selectionnees dans la gamme operatoire de 1300 et 12000 ppmv. Lors de ces experiences, une solution nutritive de type «Nitrogen Minimal Salt» (NMS), dans laquelle la concentration d'azote etait maintenue a 0.75 g/L et celle de phosphore a 0.3 ou 1.5 g/L, a ete utilisee pour l'irrigation periodique du biofiltre. Les resultats obtenus de cette etude confirment que le debit du gaz pollue est un parametre de grande importance. Les valeurs de debit gazeux ≤2 L/min ont ete identifiees comme celles permettant d'atteindre des conversions de methane ≥90% pour des charges de methane a l'entree du biofiltre ≤55 g/m3/h. S'appuyant sur ces resultats, iJ a ete deduit que la charge volumetrique maximale de methane se situe autour de 0.075 m3 (methane)/m3 (biofilter)/h, soit 6.8 m3 (gaz pollue)/m3 (biofiltre)/h. De plus, lorsque le debit gazeux est compris entre 1 et 4.2 L/min, il a une influence sur la capacite d'elimination. Neanmoins, le debit des gaz pollues n'influence pas la production de dioxyde de carbone dans le biofiltre. Il a egalement ete prouve qu'une concentration de phosphore dans la solution nutritive autour de 1.5 g/L est preferable a celle de 0.3 g/L, pour les conditions operatoires utilisees dans cette etude.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the feasibility of a freeze-thaw process as a concentration operation and used aqueous dye solution as a model binary eutectic solution to determine the localised concentration in the frozen matrix.
Abstract: The concentration phenomena during freezing and thawing were investigated to study the feasibility of freeze–thaw process as a concentration operation An aqueous dye solution was employed as a model binary eutectic solution The localised concentration in the frozen matrix was determined, and the concentration profile of the melting solution during thawing was examined It was found that the solution obtained during thawing showed higher concentration than the original solution, and the concentration did not correspond to the amount of solute localised in the frozen matrix It was suggested that the concentration phenomena during thawing would be governed by the melting droplet growth rate at the melting interface and by the diffusion rate of solute from eutectic phases to the droplet On a observe le phenomene de la concentration durant le gel et le degel afin de determiner la faisabilite du processus de gel et de degel en tant qu'operation de concentration On a utilise une solution colorante aqueuse comme solution eutectique binaire de modele On a determine la concentration localisee dans la matrice congelee et examine le profil de concentration de la solution durant la decongelation On a note que la solution obtenue durant la decongelation presentait une concentration superieure a la solution d'origine, et que la concentration ne correspondait pas a la quantite de solute localisee dans la matrice congelee Il a ete suggere que le phenomene de concentration durant le degel serait regi par le taux de croissance des gouttelettes issues de la fonte a la surface et par le taux de diffusion du solute a partir des phases eutectiques a la gouttelette

Journal ArticleDOI
TL;DR: In this article, the stability of penicillin G acylase (PGA) from Escherichia coli in their native form and free Candida antarctica lipase B (CaLB) in ionic liquids (ILs) at low water content was evaluated.
Abstract: In this work we attempted to evaluate the stability of penicillin G acylase (PGA) from Escherichia coli in their native form and free Candida antarctica lipase B (CaLB) in ionic liquids (ILs) at low water content. The hydrolysis of penicillin G to 6-aminopenicillanic acid (6-APA), and phenyl acetic acid (PAA) catalysed by PGA and the synthesis of butyl butyrate from vinyl butyrate and 1-butanol catalysed by CaLB were chosen as activity tests. The influence of these new solvents on enzyme stability was studied by incubating the enzyme (PGA or CaLB) in ILs based on dialkylimidazolium cations associated with perfluorinated and dicyanamide anions at a given temperature. Stability studies indicate that CaLB and PGA exhibited greater stability in water-immiscible ILs than in water-miscible ILs. Specifically, native PGA shows greater stability in IL media than in organic solvents. For example, a half-life time of 23 h was obtained in 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, , which was about 2000-fold higher than that in 2-propanol. The higher half-life time of CaLB was observed in (t1/2 = 84 h). Les presents travaux visent a evaluer la stabilite de l'acylase de penicilline G (APG) d'Escherichia coli dans sa forme native et de la lipase B de Candida antarctica (LBCa) dans des liquides ioniques a faible teneur en eau. L'hydrolyse de la penicilline G menant a l'apparition d'acide aminopenicillanique 6 (AAP-6) et d'acide phenylacetique (APA) catalysee par APG et la synthese de butyrate de butyle a partir de butyrate de vinyle et d'alcool butylique en utilisant la LBCa comme catalyseur sont les essais qui ont ete choisis. L'effet de ces nouveaux solvants sur la stabilite de l'enzyme a ete etudie en incubant l'enzyme en question (APG ou LBCa) dans des liquides ioniques contenant des cations de dialkylimidazolium associes a des anions perfluores et du dicyanamide, a une temperature donnee. Les etudes portant sur la stabilite indiquent que la LBCa et l'APG possedent une stabilite dans les liquides ioniques immiscibles avec l'eau superieure a leur stabilite dans les liquides ionique miscibles avec l'eau. Plus precisement, l'acylase de penicilline G native possede une stabilite dans les milieux LI superieure a sa stabilite dans les solvants organiques. Par exemple, on a obtenu une demi-vie de 23 dans le 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}imide, [emim+][NTf2−], ce qui est approximativement 2000 fois plus eleve que sa stabilite dans l'isopropanol. La demi-vie la plus longue de la LBCa a ete observee dans le [omim+][PF6−] (t 1/2 = 84 h).

Journal ArticleDOI
TL;DR: In this paper, a numerical study of the hydrodynamic of spouted beds using computational fluid dynamics (CFD) simulation is presented, where the scaling relationships proposed by He et al. [He et al., Chem. Eng. Sci. 1997;52:329-339] for spouted bed systems based on similitude method are numerically investigated using CFD simulation.
Abstract: This work presents a numerical study of the hydrodynamic of spouted beds using computational fluid dynamics (CFD) simulation. Scaling relationships proposed by He et al. [He et al., Chem. Eng. Sci. 1997;52:329-339] for spouted bed systems based on similitude method are numerically investigated using CFD simulation. In the present work it is verified that the spouted bed scale-up relationships of He et al. [He et al., Chem. Eng. Sci. 1997;52:329-339] produce good numerical results when all of the scale-up relationships are satisfied. It is also verified the behaviour of the numerical results when the scaling procedure is applied in a practical condition. In this case, the properties of fluid and solid are kept constant, which is a real situation of a scale-up procedure in a spouted bed used for drying of grains. In this work it is possible to verify that CFD simulation is a useful tool to evaluate similitude methods in spouted bed (multiphase flow) systems. The commercial package FLUENT 6.3.26 was used in all simulations.

Journal ArticleDOI
TL;DR: In this paper, the efficiency of gas-solid contact and solids circulation rate in the spouted bed were considerably improved by inserting a conical-cylindrical porous draft tube into the bed.
Abstract: Flow characteristics of a spouted bed with a porous draft tube have been investigated experimentally. In this study, both a cylindrical tube and a conical-cylindrical tube were used as the draft tube. As a result, the efficiency of gas-solid contact and solids circulation rate in the bed were considerably improved by inserting a conical-cylindrical porous draft tube into the bed. Moreover, it was confirmed that the gas flow rate through the annulus reached nearly the level of a conventional spouted bed by using conical-cylindrical porous draft tube.

Journal ArticleDOI
TL;DR: In this paper, the effect of particle size on the viscosity of oil sands slurries is investigated, and the results showed that increasing particle size led to higher viscosities and higher yield stress values.
Abstract: The success of the separation process conventionally used in Alberta for oil sands extraction is highly influenced by the rheology of the oil sands slurry. In the gravity separation vessel, high slurry viscosities can hinder the rise of aerated bitumen and reduce the efficiency of the recovery process. In this study, the effect of particle size on the viscosity of oil sands slurries is investigated. Solids from mature fine tails (MFT) obtained from tailings pond were fractionated into three fractions of different particle size distributions and their rheological properties were studied. The solids in each fraction were characterized by XRD analysis which showed the presence of different types of clays in each fraction. For the rheological measurements, dispersions of the three fractions were prepared in the supernatant water decanted from centrifuged MFT to maintain the solution chemistry of the solids. Suspensions of each fraction showed a non-Newtonian shear thinning behaviour as well as yield stress that is characteristic of structure formation within the suspensions. For all solids fractions, increasing solids concentration led to higher viscosities and higher yield stress values. Viscoelastic properties of the suspensions showed stronger solid-like behaviour at higher particle concentrations. Among the three fractions numbered from 1 to 3, solids in fraction 3 were coated with organic matters, exhibiting the highest suspension viscosities. Also for fraction 3, higher gelling potency was observed at much lower weight fractions of solids as compared to the other fractions.

Journal ArticleDOI
TL;DR: In this article, the authors measured the gas flow in a 3:1 aspect ratio vessel agitated by triple Rushton turbines by using an ultrasound Doppler probe and by means of residence time studies.
Abstract: The gas flow in a 3:1 aspect ratio vessel agitated by triple Rushton turbines has been measured by an ultrasound Doppler probe and by means of residence time studies. Strong recirculation around each impeller is found which fits in well with the compartmentalisation found in earlier liquid mixing studies. Surprisingly, when two axial A315 impellers above a Rushton turbine were used, gas recirculation around each impeller was still found. Study of the liquid phase mixing by a decolourisation technique confirmed that the gas flow essentially destroyed the strong axial liquid flow expected. Indeed, even under unaerated conditions, compartmentalisation was found between each impeller. On a mesure a l'aide d'une sonde Doppler a ultrasons et par des etudes du temps de sejour l'ecoulement gazeux dans un reservoir (rapport des dimensions caracteristiques de 3:1) agite par trois turbines Rushton. On a observe une forte recirculation autour de chaque turbine que correspond bien a la compartimentalisation trouvee dans les etudes de melange liquide precedentes. Etonnamment, lorsqu'on utilise deux turbines axiales A315 au-dessus d'une turbine Rushton, on constate encore une recirculation du gaz autour de chaque turbine. L'etude du melange de la phase liquide par une technique de decoloration confirme que l'ecoulement gazeux detruit essentiellement le fort debit axial attendu. En effet, meme dans des conditions non aerees, une compartimentalisation est observee entre chaque turbine.

Journal ArticleDOI
TL;DR: In this article, guest particles were partially coated onto the surfaces of cohesive particles using a patent-pending dry particle coating method to reduce the cohesiveness and enhance the ability of cohesive host particles.
Abstract: Very fine guest particles were partially coated onto the surfaces of cohesive particles using a patent-pending dry particle coating method involvingshear force. It was observed that partial coating on the surfaces could significantly reduce the cohesiveness and hence enhance the flowabilityof cohesive host particles. Based on different contacting status of the guest particles in relation to the host particles, two contact models wereproposed. Inter-particle forces based on these models were employed to discuss the possible roles of the guest particles, partially coated on thehost particle surfaces, in reducing the cohesiveness of the host particles.De tr`es fines particules invit ´ees ont ´et e partiellement impr´ egn´ ´ees sur les surfaces de particules coh esives au moyen d’une m´ ethode d’impr´ egnation´de particules s`eches dont le brevet est en instance et mettant en cause la force de cisaillement. On a observ e que l’impr´ ´egnation partielle sur lessurfaces pouvait r´eduire consid ´erablement les propri et´ es de coh´ esion et, par le fait m´ eme, accroˆ ˆitre la coulabilit ´e des particules h otes cohˆ esives.´En s’appuyant sur l’etat diff´ erent de l’entr´ ´ee en contact des particules invit ees, par rapport aux particules h´ ˆotes, deux mod eles d’entr` ´ee en contactont et´ ´e propos es. On a employ´ e les forces interparticulaires s’appuyant sur ces mod´ `eles pour discuter des r ˆoles possibles des particules invit ees,´partiellement impregn´ ees sur les surfaces des particules h´ ˆotes, en r ´eduisant les propri et´ es de coh´ ´esion des particules h otes.ˆKeywords: surface coating, flowability, cohesive particles, group C particles, interparticle forces

Journal ArticleDOI
TL;DR: In this article, the velocity and diameter of clusters in a fluidized bed of sand particles were measured using an optical fiber probe and the locus of the inversion point at which the directions of cluster motion changed was determined.
Abstract: The local solid flow structure of the bubbling fluidized bed of sand particles was investigated in order to identify and characterize the clusters. Extensive experiments were carried out using an optical fibre probe, measuring the velocity and the diameter of clusters. Under all operating conditions, ascending and descending clusters co-existed at all measurement locations. The locus of the inversion point at which the directions of cluster motion changed was determined. The velocity of the ascending clusters was a function of both superficial gas velocity and the radial and axial position. With increasing superficial gas velocity, both the velocity and the diameter of ascending clusters decreased near the wall. However, the velocity of descending clusters depended mainly on superficial gas velocity and the largest clusters existed closer to the wall. The results of this study help to explain cluster hydrodynamics in fluidized beds. On a etudie la structure locale de l'ecoulement des solides dans un lit fluidise bullant de particules de sable dans le but de determiner et caracteriser le phenomene d'agregation. Des experiences approfondies ont ete menees a l'aide d'une sonde a fibres optiques, qui mesure la vitesse et le diametre des agregats. Les resultats montrent dans toutes les conditions operatoires la coexistence d'agregats qui montent et qui descendent aux endroits ou ont ete prises les mesures. L'emplacement du point d'inversion ou se produisent les changements de direction des agregats a ete determine. La vitesse des agregats ascendants est fonction a la fois de la vitesse de gaz superficielle et de la position tant radiale qu'axiale. Avec l'augmentation de la vitesse de gaz superficielle, la vitesse des agregats ascendants diminue pres des parois. La meme tendance est observee pour le diametre des agregats ascendants. Toutefois, la vitesse des agregats descendants depend principalement de la vitesse de gaz superficielle et les plus gros agregats se trouvent plutot pres des parois. Les resultats de cette etude contribuent a la comprehension des agregats dans les lits fluidises.

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TL;DR: In this paper, the effect of operating parameters (superficial gas velocity in the range 2.2 - 4.0 m/s, solids circulation flux in range 5 - 50 kg/m2 · s and solids inventory, in range 80 - 180 kg) on the components of the pressure balance was analyzed around the loop of a circulating fluidized bed with 152 mm ID riser and L-valve fecuer.
Abstract: Pressure measurements around the loop of a circulating fluidized bed with 152 mm ID riser and L-valve fecuer were analysed to determine the effect of operating parameters (superficial gas velocity in the range 2.2 - 4.0 m/s, solids circulation flux in the range 5 - 50 kg/m2 · s and solids inventory, in the range 80 - 180 kg) on the components of the pressure balance. The riser pressure drop, and hence, riser solids holdup were not affected by changes in the inventory of solids in the system, provided riser superficial gas velocity and solid circulation flux were held constant. The mean suspension concentration in the riser was found to be directly proportional to the ratio of solids flux to superficial gas velocity (G / U) in the riser. On a analyse les mesures de pression autour de la boucle d'un lit fluidise circulant muni d'une colonne montante de 152 mm de diametre interieur et d'un distributeur comportant un robinet en L afin de determiner l'effet des parametres operatoires (vitesse de gaz superficielle entre 2,2 et 4,0 m/s, flux de circulation des solides entre 5 et 50 kg/m2 s et bilan des solides entre 80 et 180 kg) sur les composantes du bilan de pression. La perte de charge dans la colonne montante et par voie de consequence la retention des solides ne sont pas modifiees par les changements survenant dans le bilan des solides dans le systeme, tout au moins tant que la vitesse de gaz superficielle et le flux de circulation des solides de la colonne montante demeurent constants. La concentration moyenne de suspensions dans la colonne montante s'avere directement proportionnelle au rapport entre le flux de solides et la vitesse de gaz superficielle (G / U) dans la colonne.

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TL;DR: In this paper, an attempt has been made to seek a performance comparison of two devices of acoustic cavitation, namely, ultrasonic bath and ultrasonic horn with regard to their ability to upgrade the petroleum residues to lighter, more value-added products mainly the hydrocarbons boiling in the range of gas oil fraction.
Abstract: Conventional processes for the upgradation of residual feedstocks, viz., thermal cracking and catalytic cracking are carried out in the temperature range of 400–520°C. Such high temperatures can in principle be substituted by acoustic cavitation. In the present work, two vacuum residues, namely, Arabian mix vacuum residue (AMVR) and Bombay high vacuum residue (BHVR) and one asphalt, viz., Haldia asphalt (HA) were subjected to acoustic cavitation for different reaction times from 15 min to 120 min at ambient temperature and pressure. An attempt has been made to seek a performance comparison of two devices of acoustic cavitation, namely, ultrasonic bath and ultrasonic horn with regard to their ability to upgrade the petroleum residues to lighter, more value-added products mainly the hydrocarbons boiling in the range of gas oil fraction. Another attempt has been made to study the effect of ultrasound on the upgradation of the residue when it is emulsified in water with the help of different surfactants. For all the cases, a kinetic model has been developed based on the constituents of the residue so as to get an insight into the reaction mechanism. The study revealed that ultrasonic horn is more effective in bringing about the upgradation than ultrasonic bath and that the acoustic cavitation of the aqueous emulsified hydrocarbon mixture could reduce the asphaltenes content to a greater extent than the acoustic cavitation of non-emulsified hydrocarbon mixture. The reduction in asphaltenes content of BHVR was found to be more followed by AMVR followed by HA. The variation in the rate constants was found to be feed specific and the rate constants for the conditions of maximum conversion of asphaltenes to gas oil for AMVR, BHVR and HA were found to be 0.29 × 10−4 s−1, 1.4 × 10−4 s−1 and 0.23 × 10−4 s−1, respectively. Les procedes traditionnels visant a enrichir la concentration des matieres premieres residuelles, c.-a-d. le craquage thermique et le craquage catalytique, se font a des temperatures variant entre 400 et 520°C. Des temperatures aussi elevees peuvent, en principe, etre substituees par la cavitation acoustique. Dans le cadre de cette etude, deux residus sous vide, a savoir le melange arabe de residus sous vide (MARSV) et le residu de vide pousse de Bombay (RVPB) et un asphalte, c.-a-d. l'asphalte Haldia (AH), ont ete soumis a la cavitation acoustique selon differents temps de reaction, variant entre 15 et 120 minutes, a la temperature et la pression ambiantes. Une tentative a ete faite pour chercher a obtenir une comparaison du rendement des deux dispositifs de cavitation acoustique, a savoir un bain a ultrasons et une sonde a ultrasons, en ce qui a trait a leur capacite a enrichir la concentration des residus de petrole de facon a obtenir des produits plus legers a valeur ajoutee accrue, principalement les hydrocarbures en ebullition dans la gamme de fractions gaz-petrole. Une autre tentative a ete faite pour etudier l'effet des ultrasons sur l'enrichissement de la concentration du residu lorsqu'il est en emulsion dans l'eau avec l'aide de differents agents de surface. Dans tous les cas, on a elabore un modele cinetique fonde sur les elements constitutifs du residu de facon a obtenir un apercu du mecanisme de reaction. L'etude a revele que la sonde a ultrasons est plus efficace pour provoquer l'enrichissement de la concentration que le bain a ultrasons et la cavitation acoustique du melange d'hydrocarbures en emulsion aqueuse pouvait reduire le contenu en asphaltenes dans une plus grande mesure que la cavitation acoustique d'un melange d'hydrocarbures non en emulsion. La reduction du contenu en asphaltenes du RVPB s'est averee etre la plus grande, suivie du MARSV et de l'AH. La variation des constantes de vitesse de reduction s'est averee etre propre a la charge et les vitesses de reduction concernant les conditions de la conversion maximale des asphaltenes en gaz-petrole du MARSV, du RVPB et de l'AH se sont averees etre de 0,29 × 10−4 s−1, 1,4 × 10−4 s−1 et 0,23 × 10−4 s−1, respectivement. Mots-cles: ultrason, cavitation, residu de petrole, agent de surface, emulsion, cinetique.

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TL;DR: In this paper, the long-chain amine collector appears in the form of colloidal particles, and the hydrophobicity of sylvite surfaces critically depends on whether the amine is placed onto the solid surface or onto the surface of a bubble.
Abstract: This study shows that in the potash flotation system, in which long-chain amine collector appears in the form of colloidal particles, the hydrophobicity of sylvite surfaces critically depends on whether the amine is placed onto the solid surface or onto the surface of a bubble. The transportation of amine collector on the surface of bubbles was found to be beneficial for the bubble/KCl particle attachment.

Journal ArticleDOI
TL;DR: In this paper, an empirical model for the production of xanthan polysaccharide by batchwise cultivation of Xanthomonas campestris was developed, and the effects of oxygen depletion in the liquid and bacterial growth rate on the xanththan production rate and the time-course of the xanathan molar mass were taken into account.
Abstract: An empirical model for the production of xanthan polysaccharide by batchwise cultivation of Xanthomonas campestris was developed. The effects of oxygen depletion in the liquid and bacterial growth rate on the xanthan production rate and the time-course of the xanthan molar mass were taken into account. When the oxygen transfer was rate limiting in the non-growth phase, the molar mass of the final xanthan product was lower than that observed in the absence of oxygen limitation. A constant feed of medium, containing citric acid, increased the xanthan productivity and allowed a polysaccharide concentration of 50 kg/m3 to be reached within 57 h. Low productivity observed in a 3 m3 reactor with small-diameter Rushton turbines was attributed to stagnant zones in the wall region. On a mis au point un modele empirique pour la production de polysaccharide de xanthane par culture discontinue de Xanthomonas campestris. On a pris en compte les effets de l'epuisement de l'oxygene dans le liquide et de la vitesse de croissance bacterienne sur la vitesse de production du xanthane et l'evolution de la masse molaire du xanthane. Une alimentation constante du milieu, contenant de l'acide citrique, augmente la productivite en xanthane et permet une concentration en polysaccharide de 50 kg/m3 pouvant e'tre atteinte en 57 h. La faible productivite observee dans un reacteur de 3 m3 muni de turbines Rushton de petit diametre a ete attribuee aux zones stagnantes dans la region de la paroi.

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TL;DR: In the current project the ability of white-rot fungus Ganoderma lucidum IBL-05 was investigated for the decolourisation of some direct textile dyes and Manganese peroxidase was found to be the only enzyme secreted by the fungus.
Abstract: In the current project the ability of white-rot fungus Ganoderma lucidum IBL-05 was investigated for the decolourisation of some direct textile dyes. In the initial time course study maximum decolourisation (83.78 ±5%) was observed for Solar golden yellow R at pH 4 and temperature 30°C after 6th day. Various process parameters like optimum pH, incubation time, temperature and additional carbon and nitrogen additives were optimized to achieve maximum decolourisation of the dye by G. lucidum IBL-05. Addition of starch (1 %) accelerated the dye decolourisation (96 ± 3%). All the nitrogen sources showed an inhibitory effect on dye decolourisation and enzyme induction. Manganese peroxidase (MnP) was found to be the only enzyme (256 ± 5 U/mL) secreted by G. lucidum IBL-05.

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TL;DR: In this article, the authors used magnetic resonance (MR) images to image the motion of particles and gas just above the distributor of 3D beds of particles fluidized by air.
Abstract: Magnetic resonance (MR) was used to image the motion of particles and gas just above the distributor of 3D beds of particles fluidized by air. Three different distributors were used: (i) a single-orifice distributor, with orifice diameters 1.0–4.0 mm, (ii) a plate, drilled with a triangular array of 79 holes, each of 0.35 mm diameter, with a central nozzle containing a single hole of diameter 1.0, 2.5, or 9.0 mm, (iii) distributors with two or three orifices and diameters of 1.0 or 2.5 mm. It proved possible to extract geometrical information, such as the length of a jet, from MR images, each averaged over ∼5 min. Also, light was shed on the question of why is there such a discrepancy between reported jet-lengths. The fluidization state, the “start-up” procedure and also the number of holes all play a significant role in determining the measured distance a jet penetrates into a bed. The question as to whether the observed voids represent permanent jets or streams of bubbles was considered. The evidence from ultra-fast MR measurements strongly suggests that only the lower part of a jet from an orifice in a multi-orifice distributor is permanent; bubbles form at the top of the jet. Consequently, the top of each jet is transient. However, most of the jet from a single orifice is a permanent cavity when the bed of particles is not fluidized. The length of a jet was successfully correlated with operating variables using dimensional analysis. Finally, the flow of particles around a single jet was measured with high resolution MR. La resonance magnetique (RM) a servi pour illustrer le deplacement des particules et des gaz au-dessus du distributeur de lits de particules fluidisees par l'air en trois dimensions. On a utilise trois distributeurs differents: (i) un distributeur a orifice unique dont les diametres des orifices varient entre 1 et 4 mm, (ii) une plaque percee d'un reseau triangulaire de 79 trous d'un diametre de 0,35 mm avec une buse centrale comportant un trou unique d'un diametre de 1, 2,5 ou 9 mm et (iii) des distributeurs munis de deux ou trois orifices de 1 ou 2,5 mm de diametre. Il s'est avere possible d'extraire des informations geometriques, comme la longueur d'un jet, a partir d'images prises par RM, de moyenne superieure a 5 minutes chacune. On a egalement eclairci la question sur le grand ecart entre les longueurs de jet observees. L'etat de fluidisation, la procedure de mise en marche et aussi le nombre de trous jouent tous un role important dans la determination de la distance de penetration mesuree d'un jet dans un lit. On a etudie la question de savoir si les vides observes representent des jets permanents ou des flots de bulles. La preuve obtenue a partir de mesures par RM ultra-rapides porte fortement a croire que seule la partie inferieure d'un jet provenant d'un orifice d'un distributeur a orifices multiples est permanente; des bulles se forment sur le dessus du jet. Par consequent, le dessus de chaque jet est transitoire. Cependant, la majeure partie du jet provenant d'un seul orifice est une cavite permanente lorsque le lit de particules n'est pas fluidise. On est parvenu a mettre la longueur d'un jet en correlation avec des variables de fonctionnement au moyen de l'analyse dimensionnelle. Enfin, on a mesure le flux de particules autour d'un jet unique au moyen de la RM a haute resolution. Numeros dans le Systeme de reperage de l'information PACS: 45,70.-n, 47,55.Kf, 83,85.Fg

Journal ArticleDOI
TL;DR: In this paper, the authors compared the adsorption efficiency of a low cost adsorbent, periwinkle shell-based granular activated carbon (PSC), compared to the adhesion efficiency of commercial activated carbon and a ratio 1:1 mixture of PSC and CAC with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of industrial wastewater.
Abstract: The present investigation was undertaken to compare the adsorption efficiency of a low cost adsorbent, periwinkle shell-based granular activated carbon (PSC) with the adsorption efficiency of the commercial activated carbon (CAC) and a ratio 1:1 mixture of PSC and CAC (PSC/CAC) with respect to uptake of the organic components responsible for the chemical oxygen demand (COD) of industrial wastewater. The influence of treatment time, adsorbent dose, pH of the media, agitation speed and adsorbent particle size on the rate of percent COD removal is evaluated. PSC has shown quite effective adsorbent capacity for COD removal with 77.5% efficiency. Though its capacity is slightly lower than that of CAC with 79% efficiency, however the low material cost makes it an attractive option for the treatment of COD. The equilibrium adsorption study can be described by the Linear, Langmuir and Freundlich models. The mechanisms of the rate of adsorption of COD were analysed using the Elovich equation and a pseudo-second-order model. The models provided a very high degree of correlation of the experimental adsorption rate data suggesting either model could be used in design applications.

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TL;DR: The complex spectral refractive index (absorption index) of fly ash from two generating stations burning Canadian lignite and sub-bituminous coals has been examined by two different techniques as mentioned in this paper.
Abstract: The complex spectral refractive index (absorption index) of fly ash from two generating stations burning Canadian lignite and sub-bituminous coals have been examined by two different techniques. Ash samples collected at different combustion conditions were analyzed. It is shown that the absorption index of both ashes is in the range of 0.004 to 0.018 in the wavelength range of 0.7-2.5 μm. The effects of presence of carbonaceous material in ashes, iron content and different operating (combustion) conditions are reported. L'indice de refraction spectral complexe (indice d'absorption) de la cendre volante provenant de deux centrales thermiques bru'lant de la lignite et des charbons sous-bitumineux canadiens, a ete examine au moyen de deux techniques differentes. Des echantillons de cendres recueillis dans differentes conditions de combustion ont ete examines. On montre que l'indice d'absorption de deux cendres est compris entre 0,004 et 0,018 dans des gammes de longueur d'ondes allant de 0,7 a 2,5 m. On indique les effets de la presence de matieres carboneuses dans les cendres, de la teneur en fer et des differentes conditions de fonctionnement (combustion).

Journal ArticleDOI
TL;DR: Based on an Eulerian-Eulerian method, a three-dimensional kinetic model involving mass transfer, momentum transfer, heat transfer, and chemical reaction is developed to simulate the process of coal gasification in a 2 MW th pressurized spout-fluid bed of 450 mm in diameter with bed pressure up to 0.5 MPa as discussed by the authors.
Abstract: Based on an Eulerian-Eulerian method, a three-dimensional kinetic model involving mass transfer, momentum transfer, heat transfer, and chemical reaction is developed to simulate the process of coal gasification in a 2 MW th pressurized spout-fluid bed of 450 mm in diameter with bed pressure up to 0.5 MPa. The effects of operating pressure and bed temperature on coal gasification are investigated. The high operating pressure is beneficial to coal gasification due to the fact that the fluidization in the reactor becomes better. On one hand, a higher bed temperature can accelerate the rate of reaction. On the other hand, more air will be taken in the gasifier to keep the higher bed temperature which will consume part of combustible gases produced by coal pyrolysis or gasification. Experimental verification was carried out in a 2 MW th thermal input pressurized spout-fluid bed under the same operating condition. The comparison of calculation results with experimental results shows that most of the calculation errors are within the range of 15%.