Showing papers in "Canadian Journal of Chemical Engineering in 2010"

Structure–process–yield interrelations in nanocrystalline cellulose extraction

Abstract: In order to improve the extraction of nanocrystalline cellulose (NCC) from sulfuric acid hydrolysis of chemical pulps, we have studied the effect of hydrolysis conditions on the degree of polymerization (DP), the extent of sulfation, morphological, and solid-state characteristics of the extracted materials vis-a-vis yield. Our results demonstrate that sulfation plays a significant role in (i) determining the yield of, and (ii) imparting the unique solid-state characteristics to, the extracted, H2O-insoluble cellulose nanomaterial from sulfuric acid hydrolysis. The hydrolysis process is itself proven to be highly reproducible, and NCC with high crystallinity (>80%) and a yield between 21% and 38% could be extracted from a fully bleached, commercial softwood kraft pulp using 64 wt.% sulfuric acid at 45–65°C after freeze drying. The NCC aggregates, with iridescent patterns typical of chiral nematic materials, are parallelepiped rod-like structures which possess cross-sections in the nanometer range and lengths orders of magnitude larger, resulting in high aspect ratios. The Ruland–Rietveld analysis was employed to precisely resolve X-ray diffraction patterns and obtain information on crystallite size, crystalline and amorphous areas, and crystallinity of the extracted materials. Afin d'ameliorer l'extraction de la cellulose nanocristalline (CNC) a partir de l'hydrolyse a l'acide sulfurique des pulpes chimiques, nous avons etudie l'effet des conditions d'hydrolyse sur le degre de polymerisation (DP), l'ampleur de la sulfatation et les caracteristiques morphologiques et a l'etat solide des materiaux extraits, vis-a-vis du rendement. Nos resultats demontrent que la sulfatation joue un role significatif dans (i) la determination du rendement et (ii) la transmission des caracteristiques a l'etat solide uniques au nanomateriau extrait de la cellulose insoluble dans l'eau provenant de l'hydrolyse a l'acide sulfurique. Le processus d'hydrolyse est lui-meme prouve etre hautement reproductible et de la CNC de haute cristallinite (>80%) avec un rendement variant entre 21 et 38% pouvait etre extraite d'une pulpe kraft commerciale et totalement blanchie de bois tendre, en utilisant de l'acide sulfurique a 64 % en poids a une temperature de 45–65°C apres lyophilisation. Les agregats de CNC, portant des modeles iridescents typiques des materiaux chirals nematiques, sont des structures en forme de tiges parallelepipediques dont les sections transversales sont de l'ordre du nanometre et les longueurs sont d'ordres superieurs, ce qui entraine des rapports de forme eleves. L'analyse Ruland–Rietveld a ete employee pour resoudre precisement les modeles de diffraction des rayons X et obtenir de l'information sur la taille des cristallites, les zones cristallines et les zones amorphes ainsi que sur la cristallinite des materiaux extraits.

Biomimetic gradient hydrogels for tissue engineering

Abstract: During tissue morphogenesis and homeostasis, cells experience various signals in their environments, including gradients of physical and chemical cues. Spatial and temporal gradients regulate various cell behaviours such as proliferation, migration, and differentiation during development, inflammation, wound healing, and cancer. One of the goals of functional tissue engineering is to create microenvironments that mimic the cellular and tissue complexity found in vivo by incorporating physical, chemical, temporal, and spatial gradients within engineered three-dimensional (3D) scaffolds. Hydrogels are ideal materials for 3D tissue scaffolds that mimic the extracellular matrix (ECM). Various techniques from material science, microscale engineering, and microfluidics are used to synthesise biomimetic hydrogels with encapsulated cells and tailored microenvironments. In particular, a host of methods exist to incorporate micrometer to centimetre scale chemical and physical gradients within hydrogels to mimic the cellular cues found in vivo. In this review, we draw on specific biological examples to motivate hydrogel gradients as tools for studying cell–material interactions. We provide a brief overview of techniques to generate gradient hydrogels and showcase their use to study particular cell behaviours in two-dimensional (2D) and 3D environments. We conclude by summarizing the current and future trends in gradient hydrogels and cell–material interactions in context with the long-term goals of tissue engineering.

On MHD heat and mass transfer over a moving vertical plate with a convective surface boundary condition

Abstract: In this paper, the magnetohydrodynamics (MHD) boundary layer flow with heat and mass transfer over a moving vertical plate in the presence of magnetic field and a convective heat exchange at the surface with the surrounding has been studied. The similarity solution is used to transform the system of partial differential equations, describing the problem under consideration, into a boundary value problem of coupled ordinary differential equations, and an efficient numerical technique is implemented to solve the reduced system. The results are presented graphically and the conclusion is drawn that the flow field and other quantities of physical interest are significantly influenced by these parameters. Dans ce document, on a etudie l'ecoulement dans la couche limite magnetohydrodynamique (MHD) avec transfert de chaleur et de masse sur une plaque verticale mobile en presence d'un champ magnetique et d'un echange de chaleur par convection a la surface avec les alentours. La solution de similitude est utilisee pour transformer le systeme d'equations aux derivees partielles, decrivant le probleme qui est considere, dans un probleme de la valeur au bord d'equations differentielles ordinaires couplees et une technique numerique efficace est mise en place pour regler le systeme reduit. Les resultats sont presentes de facon graphique et la conclusion tiree est que le champ d'ecoulement et les autres quantites d'interet physique sont considerablement influences par ces parametres.

Modelling and control of different types of polymerization processes using neural networks technique: A review

Abstract: Polymerization process can be classified as a nonlinear type process since it exhibits a dynamic behaviour throughout the process Therefore, it is highly complicated to obtain an accurate mechanistic model from the nonlinear process This predicament always been a “wall” to researchers to be able to devise an optimal process model and control scheme for such a system Neural networks have succeeded the other modelling and control methods especially in coping with nonlinear process due to their very conciliate characteristics These characteristics are further explained in this work The predicament that is encountered by researchers nowadays is lack of data which consequently lead to an imprecise mechanistic model that scarcely conforms to the desired process The implementations of the neural network model not only restrict to polymerization reactor but to other difficult-to-measure parameters such as polymer quality, polymer melts index and mixture of initiators This work is aimed to manifest ascendancy of neural networks in modelling and control of polymerization process Le processus de polymerisation peut etre categorise comme un processus de type non lineaire, puisqu'il affiche un comportement dynamique tout au long du processus Par consequent, il est tres complique d'obtenir un modele mecaniste precis du processus non lineaire Cette situation fâcheuse a toujours represente un « mur » pour les chercheurs qui souhaitent concevoir un schema de controle et de modelisation du processus optimal pour un tel systeme Les reseaux neutres ont succede aux autres methodes de modelisation et de controle, surtout pour s'occuper du processus non lineaire en raison de leurs caracteristiques tres conciliantes Ces caracteristiques sont expliquees plus en detail dans ce travail La situation fâcheuse rencontree par les chercheurs aujourd'hui est le manque de donnees, ce qui mene par consequent a un modele mecaniste imprecis qui est a peine conforme au processus souhaite Les mises en œuvre du modele des reseaux neutres se limitent non seulement au reacteur de polymerisation, mais aux autres parametres difficiles a mesurer, comme la qualite du polymere, l'indice de fluidite du polymere et le melange des initiateurs Ce travail cherche a manifester l'ascendance des reseaux neutres en modelisant et controlant le processus de polymerisation

Multiphase flow at the edge of a steam chamber

Abstract: The use of steam-assisted gravity drainage (SAGD) to recover bitumen from Athabasca deposits in Alberta has been growing. Butler [Butler, J. Can. Pet. Tech. 1985;24:42–51] derived a simple theory to calculate the production rate of oil during SAGD in an ideal reservoir. This simple and useful theory made several assumptions about the properties of the reservoir and operating conditions of the process. The theory also assumed that the highest mobility oil is at the edge of the steam chamber and that the oil phase velocity is highest at the chamber edge and reduces with distance into the oil sand. This research examines flow conditions at the edge of the steam chamber. Specifically, a new theory is derived that takes into account the impact of oil saturation and relative permeability on the oil mobility profile at the edge of a steam chamber. It is shown that the flow behaviour at the edge of a steam chamber is more complex and is not fully represented by Butler's theory. Contrary to Butler's theory, the oil mobility has its maximum some distance away from the edge of the steam chamber. The results reveal that the higher the thermal diffusivity of the oil sand, the deeper the location where the oil phase velocity is maximum. The developed model has been validated against published experimental and field data.

Effects of higher order chemical reaction on micropolar fluid flow on a power law permeable stretched sheet with variable concentration in a porous medium

Abstract: An analysis has been carried out to obtain the effects of higher order chemical reaction on flow and mass transfer characteristics of micropolar fluids past a nonlinear permeable stretching sheet immersed in a porous medium with variable concentration of the reactant. The local similarity solutions for the flow, microrotation and mass transfer are obtained numerically and are illustrated graphically for various material parameters. Comparisons carried out with results from previously published work present excellent agreement. The results show that rate of mass transfer from the sheet to the surrounding fluid decreases significantly with the increase of nonlinear stretching parameter and increases with the increase of concentration parameter. The mass transfer of the reactive species strongly depends on the reaction rate parameter as well as order of the chemical reaction. It is stronger for the first-order reaction than that for the higher order reaction. The rate of surface mass transfer decreases with the increase of the Darcy parameter. The results also show that the effect of these parameters on the micropolar fluids are less compared to the Newtonian fluids. Une analyse a ete realisee pour obtenir les effets d'une reaction chimique de plus haut ordre sur les caracteristiques de transfert de masse et de debit de fluides micropolaires traversant une feuille etirable permeable non lineaire immergee dans un media poreux avec concentration variable au reactant. Les solutions de similarite locale pour les transferts de masse, de microrotation et de debit sont obtenues numeriquement et illustrees graphiquement en fonction de parametres de divers materiaux. Des comparaisons dressees a partir des resultats d'ouvrages publies anterieurement presentent une excellente concordance. Les resultats montrent que le taux de transfert de masse de la feuille au fluide environnant diminue de facon significative en augmentant le parametre d'etirement non lineaire et augmente avec l'augmentation du parametre de concentration. Le transfert de masse de l'espece reactive depend largement du parametre de taux de reaction ainsi que de l'ordre de la reaction chimique. Il est plus eleve pour la reaction de premier ordre que pour la reaction d'ordre plus eleve. Le taux de transfert de masse de surface diminue avec la hausse du parametre de Darcy. Les resultats montrent egalement que l'effet de ces parametres sur les fluides micropolaires est moins eleve si on le compare aux fluides newtoniens.

Investigation of enzymatic biodiesel production using ionic liquid as a co‐solvent

Abstract: In this study, the lipase catalysed esterification reaction for biodiesel production was investigated in the presence of the ionic liquid [BMIM][PF6]. Unlike regular organic solvents, many ionic liquids have no vapour pressure, and are therefore considered non-volatile. When used in systems with enzyme catalysts, ionic liquids may enhance their activity, selectivity, and stability. The use of an enzyme (lipase) as a catalyst, and the ionic liquid as a solvent/immobilization agent also represents an environmentally friendly, “green” technology. Methyl acetate was used as the acyl acceptor as opposed to the more commonly used methanol due to the negative effects methanol and the glycerol by-product has on lipase enzyme activity. The results of this research indicate that methyl oleate (i.e., biodiesel) was successfully produced, with an 80% overall biodiesel yield in the presence of ionic liquid, at a 1:1 ratio (v/v) to the amount of oil. This verified that the presence of an ionic liquid, at a specified amount, improved the activity of the lipase and the overall biodiesel yield. Results also indicate the addition of ionic liquid facilitated the separation of the methyl esters from the triacetylglycerol by-product. The best conditions investigated was found to be: 14:1 molar ratio between oil and acyl acceptor; 20% (w immobilised lipase/w of oil; and a temperature in the range of 48–55°C. However, additional purification is required in order for the produced biodiesel to meet ASTM standards. Dans cette etude, on a examine la reaction d'esterification catalysee par lipase pour la production de biodiesel, en presence du liquide ionique [BMIM][PF6]. Contrairement aux solvants organiques ordinaires, un bon nombre de liquides ioniques n'ont pas de pression de vapeur et sont par consequent consideres comme non-volatils. Lorsqu'ils sont utilises dans des systemes comportant des catalyseurs enzymatiques, les liquides ioniques peuvent rehausser leur activite, leur selectivite et leur stabilite. L'utilisation d'un enzyme (lipase) comme catalyseur et du liquide ionique comme solvant/agent d'immobilisation represente egalement une technologie « verte » et ecologique. L'acetate de methyle a ete utilise comme accepteur d'acyle, au lieu du methanol plus couramment utilise, en raison des effets negatifs du methanol et du produit derive du glycerol sur l'activite enzymatique de la lipase. Les resultats indiquent que de l'oleate de methyle (soit du biodiesel) a ete produit avec succes, avec un rendement general de biodiesel de 80%, en presence de liquide ionique, et ce, a un rapport de 1:1 (v/v) par rapport a la quantite d'huile. Cela a permis de confirmer que la presence d'un liquide ionique, a un montant specifie, augmentait l'activite de la lipase et le rendement general de biodiesel. Les resultats indiquent egalement que l'ajout d'un liquide ionique facilitait la separation des esters de methyle du produit derive du triacetyle-glycerol. Les meilleures conditions enregistrees etaient les suivantes : rapport molaire 14:1 entre l'huile et l'accepteur d'acyle; 20% (poids de lipase immobilisee /poids d'huile) et une temperature dans l'intervalle 48–55°C. Cependant, une purification supplementaire est necessaire pour que le biodiesel produit soit conforme aux normes ASTM.

Polymer aids for settling and filtration of oil sands tailings

Abstract: Commercial Magnafloc 1011 (Percol 727) polymer and in-house synthesised Al-PAM polymer were used to flocculate oil sands tailings that were derived from low and high fines oil sands ores. Fines are defined as mineral solids less than 44 µm. The performance of polymers was evaluated in terms of tailings settling, filtration rate, and final moisture content of tilter cakes. Both polymers were shown to effectively flocculate the derived oil sands tailings and hence to enhance tailings settling. Al-PAM performed very well as a filtration aid. The final moisture content of the filter cake obtained from tailings derived from the low fines ore was 6.6 ± 1.2 wt.% and that from the high fines ore was 16.9 ± 0.8 wt.%. This class of polymer can provide an alternative approach for oil sands tailings disposal that has the potential to eliminate tailings ponds. However, the commercial Magnafloc 1011 polymer was found ineffective as a filtration aid for the two tailings tested in this study.

Optimum design of integrated liquid recovery plants by variable population size genetic algorithm

Abstract: Increase in the price of energy sources as well as economic problems have caused cryogenic natural gas plants to become more complex and efficient. After selecting the process configuration, the flow rate, pressure, and temperature of the process fluid streams are determining factors which should be tuned in order to find the optimum condition. Products specification and operating costs of the plant are two significant parameters which should be considered in an optimal design. Moreover, process design limitations contribute to the problem being more difficult. This paper shows how the optimal operating point in an integrated NGL recovery plant can be found through solving a complex constrained optimization problem. A Variable Population size Genetic Algorithm (VPGA) was used for optimization. As well, the role of VPGA algorithm parameters in solving the process design problems is investigated in this study. The analysis showed that the VPGA method has better performance compared to the general GA methods. The plant-wide net profit increases 12493360 $/year only by changing the selected operating conditions to its optimal value. En raison de l'augmentation du prix des sources d'energie, ainsi que des problemes economiques, des usines de gaz naturel cryogeniques sont devenues plus complexes et efficaces. Une fois la configuration des procedes choisie, le debit, la pression et la temperature des courants de fluides des procedes sont des facteurs determinants que l'on doit regler pour trouver la condition optimale. La caracterisation des produits et les frais d'exploitation de l'usine constituent deux parametres importants que l'on doit considerer dans une conception optimale. De plus, les limites de la conception des procedes contribuent au fait que le probleme devient de plus en plus difficile. Ce document indique la facon a laquelle on peut trouver le point d'exploitation optimal dans une usine de recuperation de LGN integree en reglant un probleme d'optimisation sous contraintes complexe. Un algorithme genetique de population de taille variable (VPGA) a ete utilise pour l'optimisation. De meme, le role des parametres de l'algorithme VPGA dans la resolution des problemes de conception des procedes est analyse dans cette etude. L'analyse a demontre que la methode VPGA a offert un meilleur rendement en comparaison avec les methodes d'algorithme genetique generales. Le benefice net des usines augmente de 12493360 $/annee uniquement en changeant les conditions d'exploitation choisies a sa valeur optimale.

Numerical simulation of viscous fingering of shear‐thinning fluids

Abstract: The viscous fingering instability of miscible shear-thinning fluids has been examined using a pseudo-spectral numerical technique based on the Hartley transform. The instability was studied for a flow in a rectilinear Hele-Shaw cell, and the shear-thinning character of the fluids has been modelied using the Carreau equation. New mechanisms of viscous fingering not previously observed in the case of similar Newtonian flow displacements have been identified. These mechanisms, which are reminiscent of the fractal patterns observed in experimental studies, were interpreted in terms of the velocity-dependent mobility of the flow. On a etudie l'instabilite de la digitation visqueuse pour des fluides rheofluidifiants miscibles en utilisant une technique numerique pseudo-spectrale basee sur la transformation de Harley. L'instabilite a ete etudiee pour un ecoulement dans une cellule rectiligne de Hele-Shaw, et le caractere rheofluidifiant des fluides a ete modelise par le modele de Carreau. De nouveaux mecanismes de digitation visqueuse non observes anterieurement dans le cas de deplacements d'ecoulements newtoniens similaires ont ete identifies. Ces mecanismes, qui rappellent les schemas fractals observes dans des etudes experimentales, ont ete interpretes en termes d'une mobilite dependant de la vitesse de l'ecoulement.

Adsorption performance of nickel and cadmium ions onto brewer's yeast

Abstract: The brewer’s yeast was used as adsorbent for the removal of Ni(II) and Cd(II) metal ions from aqueous solution. The surface of the brewer’syeast had three main functional groups of sulfonate, carboxyl, and amine groups. The pH of solution played an important role on the uptake ofmetal ions, and optimum adsorption was obtained at pH 6. Acid solution (pH 3) was efficient for the desorption of Ni(II) and Cd(II) ions fromloaded brewer’s yeast and the desorption efficiency was higher than 90%. The rate of metal ions adsorption onto brewer’s yeast was rapid withshort contact time. The kinetics of the adsorption process was found to follow the pseudo-second-order kinetic model. Langmuir and Freundlichisotherm models were used to fit the experimental data with Langmuir isotherm model having a better fit. The maximum uptakes of Ni(II) andCd(II) by brewer’s yeast were estimated to be 5.34 and 10.17mg/g, respectively.La levure de brasserie a et´ e utilis´ ee comme absorbant pour le retrait des ions m´ ´etalliques de Ni(II) et de Cd(II) d’une solution aqueuse. La surfacede la levure de brasserie avait trois principaux groupes fonctionnels des groupes sulfonate, carboxyle et amine. Le pH de la solution jouait un roleˆimportant sur le captage d’ions metalliques, et l’adsorption optimale´ etait atteinte au pH 6. Une solution acide (pH´ =3) ´etait efficiente pour ladesorption des ions de Ni(II) et de Cd(II) de la levure de brasserie charg´ ´ee et l’efficacit edelad´ esorption d´ ´epassait 90%. Le taux d’adsorption d’ionsm´etalliques sur la levure de brasserie ´etait rapide avec un temps de contact court. La cin etique du proc´ ´ed e d’adsorption s’est d´ ´emontr ´ee suivrele pseudo-modele cin` etique de deuxi´ eme ordre. Les mod` `eles d’isothermes de Langmuir et Freundlich etaient utilis´ es en fonction des donn´ ees´experimentales o´ `ulemod `ele d’isotherme de Langmuir offrait une meilleure correspondance. Le captage maximum de Ni(II) Cd(II) par la levure a´et e estim´ ´e ˆetre 5.34mg/g et de 10,17mg/g, respectivement.Keywords: adsorption, nickel, cadmium, brewer’s yeast, metal ions

Application of support vector regression for developing soft sensors for nonlinear processes

Abstract: The field of soft sensor development has gained significant importance in the recent past with the development of efficient and easily employable computational tools for this purpose. The basic idea is to convert the information contained in the input–output data collected from the process into a mathematical model. Such a mathematical model can be used as a cost efficient substitute for hardware sensors. The Support Vector Regression (SVR) tool is one such computational tool that has recently received much attention in the system identification literature, especially because of its successes in building nonlinear blackbox models. The main feature of the algorithm is the use of a nonlinear kernel transformation to map the input variables into a feature space so that their relationship with the output variable becomes linear in the transformed space. This method has excellent generalisation capabilities to high-dimensional nonlinear problems due to the use of functions such as the radial basis functions which have good approximation capabilities as kernels. Another attractive feature of the method is its convex optimization formulation which eradicates the problem of local minima while identifying the nonlinear models. In this work, we demonstrate the application of SVR as an efficient and easy-to-use tool for developing soft sensors for nonlinear processes. In an industrial case study, we illustrate the development of a steady-state Melt Index soft sensor for an industrial scale ethylene vinyl acetate (EVA) polymer extrusion process using SVR. The SVR-based soft sensor, valid over a wide range of melt indices, outperformed the existing nonlinear least-square-based soft sensor in terms of lower prediction errors. In the remaining two other case studies, we demonstrate the application of SVR for developing soft sensors in the form of dynamic models for two nonlinear processes: a simulated pH neutralisation process and a laboratory scale twin screw polymer extrusion process. A heuristic procedure is proposed for developing a dynamic nonlinear-ARX model-based soft sensor using SVR, in which the optimal delay and orders are automatically arrived at using the input–output data. Le domaine du developpement des capteurs logiciels a recemment gagne en importance avec la creation d'outils de calcul efficaces et facilement utilisables a cette fin. L'idee de base est de convertir l'information obtenue dans les donnees d'entree et de sortie recueillies a partir du processus dans un modele mathematique. Un tel modele mathematique peut servir de solution de rechange economique pour les capteurs materiels. L'outil de regression par machine a vecteur de support (RMVS) constitue un outil de calcul qui a recemment ete l'objet de beaucoup d'attention dans la litterature des systemes d'identification, surtout en raison de ses succes dans la creation de modeles de boite noire non lineaires. Dans ce travail, nous demontrons l'application de la RMVS comme outil efficace et facile a utiliser pour la creation de capteurs logiciels pour les procedes non lineaires. Dans une etude de cas industrielle, nous illustrons le developpement d'un capteur logiciel a indice de fluidite a etat permanent pour un processus d'extrusion du polymere d'acetate de vinyle-ethylene a l'echelle industrielle en utilisant la RMVS. Le capteur logiciel fonde sur la RMVS, valide sur une vaste gamme d'indices de fluidite, a surclasse le capteur logiciel fonde sur les moindres carres non lineaires existant en matiere d'erreurs de prediction plus faibles. Dans les deux autres etudes de cas, nous demontrons l'application de la RMVS pour la creation de capteurs logiciels sous la forme de modeles dynamiques pour deux procedes non lineaires: un processus de neutralisation du pH simule et un processus d'extrusion de polymere a deux vis a l'echelle laboratoire. Une procedure heuristique est proposee pour la creation d'un capteur logiciel fonde sur un modele ARX non lineaire dynamique en utilisant la RMVS, dans lequel on atteint automatiquement le delai optimal et les ordres en utilisant les donnees d'entree et de sortie.

Investigation of hydrodynamics of binary fluidized beds via radioactive particle tracking and dual‐source densitometry

Abstract: The mixing and hydrodynamic behaviour of binary fluidized beds of particles of same size and differing density has been investigated experimentally by using radiation based non-invasive techniques, viz. radioactive particle tracking (RPT) and dual-source densitometry. The effect of air inlet velocity and bed composition has been investigated. RPT experiments are performed individually for both the solids by tracking one particle at a time. Many interesting findings are discussed, for example, such as the heavier (jetsam) phase is seen to be fluidized by action of the lighter (flotsam) phase even below its minimum fluidization velocity. Further, it has been found that while with increase in air inlet velocity, the extent of mixing of solid phases increases; even at very high air velocities the jetsam phase is not completely mixed. The important role played by the particle–particle collisions in the fluidization of binary mixtures is quantitatively highlighted. Le melange et le comportement hydrodynamique des lits fluidises binaires de particules de meme taille et de differentes densites ont ete etudies experimentalement en utilisant une technique non invasive a base de rayonnements par le suivi des particules radioactives et la densitometrie a double foyer. L'effet de la vitesse d'admission d'air et de la composition du lit a ete etudie. Des experiences de suivi des particules radioactives sont executees individuellement pour chacun des deux solides par le suivi d'une particule a la fois. Plusieurs resultats interessants sont discutes, comme par exemple, il est observe que la phase plus lourde (jetsam) est fluidisee par l'action de la phase plus legere (flotsam), meme en dessous de sa vitesse minimum de fluidisation. De plus, il a ete constate que, tandis qu'avec l'accroissement de la vitesse d'admission d'air, l'ampleur du melange des phases solides augmente, la phase jetsam n'est pas completement melangee meme a des vitesses d'air tres elevees. Le role important joue par les collisions particule-particule dans la fluidisation des melanges binaires est quantitativement mis en evidence.

Effect of tube diameter on two-phase flow patterns in mini tubes

Abstract: The effect of tube diameter on two-phase flow patterns was investigated in circular tubes with inner diameters of 0.6, 1.2, 1.7, 2.6, and 3.4 mm using air and water. The gas and liquid superficial velocity ranges were 0.01–50 and 0.01–3 m/s, respectively. The gas and liquid flow rates were measured and the two-phase flow pattern images were recorded using high-speed CMOS camera. The flow patterns observed were dispersed bubbly, bubbly, slug, slug-annular, wavy-annular, stratified, and annular flows. These flow patterns were not observed in all the test diameters, but were found to be unique to particular tube diameters, confirming the effect of tube diameter on the flow pattern. The data obtained were compared to existing experimental data and flow regime transition maps which show generally reasonable overall agreement at the larger diameters, but significant differences were observed with the smaller diameter tubes. On a analyse l'effet du diametre des tubes dans des modeles d'ecoulement biphase dans des tubes circulaires avec des diametres internes de 0,6, 1,2, 1,7, 2,6 et 3,4 mm en utilisant de l'air et de l'eau. Les ecarts de vitesse superficielle de gaz et de liquide etaient de 0,01–50 m/s et 0,01–3 m/s respectivement. Les debits de gaz et de liquide ont ete mesures et les images des modeles d'ecoulement biphase ont ete enregistrees a l'aide d'un appareil photo CMOS haute vitesse. Les modeles d'ecoulement observes etaient l'ecoulement a bulles, a bulles, en piston, en piston annulaire, ondule annulaire, stratifie et annulaire. Ces modeles d'ecoulement n'ont pas ete observes dans tous les parametres d'essai, mais on a constate qu'ils etaient uniques aux diametres de tubes particuliers, ce qui confirme l'effet du diametre des tubes sur le modele d'ecoulement. Les donnees obtenues ont ete comparees aux donnees experimentales existantes et aux cartes de transition des regimes d'ecoulement qui demontrent un accord global raisonnable de facon generale aux parametres plus grands, mais des differences importantes ont ete observees dans les tubes aux diametres plus petits.

Study on corrosion rate of carbon steel pipe under turbulent flow conditions

Abstract: The effect of time (or corrosion products formation) on corrosion rate of carbon steel pipe in aerated 0.1 N NaCl solution under turbulent flow conditions was investigated. Tests were conducted using electrochemical polarisation technique by determining the limiting current density of oxygen reduction in Reynolds number (Re) range of 15 000 to 113 000 and temperature range of 30–60°C. The effect of corrosion products formation on the friction factor increase was studied and discussed. Empirical correlations for limiting current density as a function of Re were obtained at various solution temperatures for clean surface and for corroded surface. It was found that formation of corrosion products with time decreases the corrosion rate at low Re and temperature, while it increases the corrosion rate at high Re and temperature. As the corrosion products formed the surface roughness increased leading to increase the friction factor depending on temperature, Re, and corrosion rate. On a analyse l'effet du temps (ou la formation de produits de corrosion) sur la vitesse de corrosion d'un tuyau d'acier au carbone dans une solution 0.1 N NaCl aeree dans des conditions d'ecoulement turbulent. Des essais ont ete realises a l'aide de la technique de polarisation electrochimique en determinant la densite de courant limite de la reduction de l'oxygene dans l'ecart de nombres de Reynolds de 15000 a 113000 et dans l'echelle de temperature de 30°C a 60°C. L'effet de la formation de produits de corrosion sur l'augmentation du facteur de frottement a ete etudie et discute. Les correlations empiriques pour la densite de courant limite comme fonction du nombre de Reynolds ont ete obtenues a diverses temperatures de solution pour une surface propre et une surface corrodee. On a decouvert que la formation de produits de corrosion avec le temps reduit la vitesse de corrosion a une temperature et un nombre de Reynolds bas tout en augmentant la vitesse de corrosion a une temperature et nombre de Reynolds eleves. Pendant que les produits de corrosion se formaient, la rugosite de la surface augmentait, ce qui a mene a une augmentation du facteur de frottement selon la temperature, le nombre de Reynolds et la vitesse de corrosion. © 2010 Canadian Society for Chemical Engineering

Bitumen content estimation of athabasca oil sand from broad band infrared reflectance spectra

Abstract: Oil sand is a mixture of quartz grains, clay minerals, bitumen, water, and minor accessory minerals. There is a need in oil sands mining operations for a robust method to estimate total bitumen content in real time; and so modelling of the total bitumen content (TBC) in Athabasca oil sands of Western Canada was undertaken on the basis of hyperspectral reflectance spectra. A selection of different bitumen, water, and clay mineral spectral features (3.0–30.0 µm) was used to develop broad-band TBC predictive models that have good accuracy, with less than 1.5% error with respect to laboratory methods of bitumen assay. These models are also robust, in that they are independent of mine location. Simple broad band models, based upon previously identified Gaussian features or wavelet features, provide an incremental improvement over the currently deployed industry two-band ratio model. An improved two-band model was also developed, which makes use of a combination of the same two bands but normalised to their mean. A wavelet-based, broad-band model comprised of indices and five bands, where the bands are normalised to the mean of the bands, adequately addresses the influence of water, clay, and textural variation on selected bitumen features. This five-band model appears to produce the most robust estimator of TBC, with a dispersion of ∼1.1–1.5%, which can be applied to different sites within a mine and to different mines without additional tuning or calibration, as evidenced by regression slopes of 0.99–1.0 for modelling, validation, and blind data sets.

Mixing intensification for the mineral industry

Abstract: The modern mineral industry uses hydrometallurgical processes to extract metals from ores. Typically, a large volume of ore slurry is treated in mixing tanks in a mineral processing plant, for leaching, digestion, precipitation, and other chemical processing to obtain pure metals or concentrated ores. This paper discusses mixing intensification as a means to achieve process intensification for the mineral process industry. Areas where mixing intensification can be applied are illustrated with case examples. Among them, it was suggested that for slowly reacting slurry systems typical in the mineral processing operations, high solid loadings should be considered to boost throughput. Improved agitator energy efficiency can be achieved by removing baffles, at very high solid loadings. Slurry stratification in tanks can be used to boost either solids residence time or slurry through flow. L'industrie moderne des mineraux utilise des procedes hydrometallurgiques pour extraire les metaux des minerais. Typiquement, un gros volume de boues de minerai est traite dans des reservoirs de melange d'une usine de traitement des mineraux. Ces boues subissent de nombreux traitements dont lixiviation, digestion, precipitation et autres traitements chimiques en vue d'obtenir des metaux purs. Cet article propose d'adopter l'intensification du melange pour permettre une intensification des procedes de l'industrie du traitement des mineraux. Les domaines pour lesquels l'intensification du melange peut etre applique sont identifies et des exemples sont fournis pour illustrer le concept.

Effect of solid material and surfactant presence on interactions of bubbles with horizontal solid surface

Abstract: The interaction of a bubble with an immersed horizontal solid surface is studied experimentally. The effect of presence of a surfactant (limited to a specific nonionic surfactant, α-terpineol, of various concentrations) and of surface material (cleaned glass, polypropylene, polyethylene, and Teflon) is investigated. The study focuses on two particular stages of the interaction, (i) the process of bubble bounce, which includes a collision and subsequent rebound from the solid surface, and (ii) the bubble attachment, which occurs after collision in time much longer than the duration of bounce and also after disappearance of all visible bubble movement. It is observed that the effect of the surface material on the bouncing is minor, possibly due to the liquid film separating the bubble and the solid surface. The presence of surfactant significantly affects the bouncing process. It not only decreases the initial bubble velocity, but also diminishes the bubble deformation after the collision and suppresses the bubble rebound from the surface. No rebound from the surface is observed in the most concentrated (1 x 10- 3 mol/L) α-terpineol solution. The adhesion time depends both on the solid material and α-terpineol concentration. If the α-terpineol concentration is increased, the adhesion time increases in the case of polypropylene surface, while it decreases in the case of polyethylene and Teflon surfaces. Results of this study are relevant for the description of attachment mechanism and to determine the proper conditions for selective flotation of plastics.

Co-current descending two-phase flows in inclined packed beds: Experiments versus simulations

Abstract: The effect of inclination angle of a packed bed on its corresponding gas–liquid flow segregation and liquid saturation spatial distribution was measured in co-current descending gas–liquid flows for varying inclinations and fluid velocities, and simulated using a two-phase Eulerian computational fluid dynamics framework (CFD) adapted from trickle-bed vertical configuration and based on the porous media concept. The model predictions were validated with our own experimental data obtained using electrical capacitance tomography. This preliminary attempt to forecast the hydrodynamics in inclined packed bed geometries recommends for the formulation of appropriate drag force closures which should be integrated in the CFD model for improved quantitative estimation. Resume: Nous analysons l'effet de l'angle d'inclinaison d'un milieu poreux soumis a un ecoulement biphasique gaz-liquide de haut en bas. L'analyse s'est attardee en particulier sur l'aptitude a la segregation gaz-liquide et l'evolution de la saturation liquide en fonction de l'angle d'inclinaison et des vitesses de fluides. Une analyse theorique du phenomene de segregation y est effectuee par simulation de type mecanique des fluides numerique selon une approche Eulerienne de l'ecoulement biphasique dans l'espace poreux du milieu granulaire. Un debut de validation des simulations est discute sur la base de la distribution spatiale des saturations liquides mesurees par tomographie electrique a capacitance. Les premieres conclusions de ce travail montrent l'inadequation relative des lois de fermeture sur les forces de frottement telles qu'elles ont ete formulees pour les ecoulements biphasiques descendants verticaux; ce qui requiert des efforts futurs a developper des lois de frottement plus adaptees aux geometries biphasiques inclinees.

Properties of uniaxially stretched polypropylene films: effect of drawing temperature and random copolymer content

Abstract: Cast films of two linear polypropylenes (PP) having different molecular weights and their blends with 20 wt% random copolymer were prepared by extrusion. The produced cast films were then uniaxially hot drawn at T = 110 and 140°C under a draw ratio (DR) of 6 using a machine direction orientation (MDO) unit. The effects of drawing temperature and addition of random copolymer on the properties of the films were investigated. The type of crystals (spherulites or fibrils) was studied using differential scanning calorimetry (DSC). The drawing process generated a highly oriented fibrillar crystalline structure, resulting in an increase in the melting point of the films by about 10°C. The films drawn at 140°C revealed coexisting lamellae and fibrils whereas at 110°C mainly a fibrillar structure was observed. Tensile measurements showed a greater strength for the sample stretched at lower temperature (i.e., 110°C). The effect of drawing temperature and copolymer content on tear resistance was also explored. The medium-molecular weight PP film stretched at 110°C showed greater tear resistance than at 140°C. The addition of the random copolymer into the medium-molecular weight PP reduced the tear resistance significantly whereas the impact for the high-molecular weight was not noticeable. Adding the random copolymer significantly decreased the haze for the films and hence drastically improved the clarity. Des feuilles coulees de deux polypropylenes (PP) lineaires avec des poids moleculaires differents et leurs melanges avec 20% d'equivalent en poids de copolymere aleatoire ont ete preparees par extrusion. Les feuilles coulees produites ont alors ete etirees a chaud de facon uniaxiale a T = 110 et 140°C en vertu d'un rapport d'etirage de 6 a l'aide d'une unite d'orientation de sens machine. On a etudie les effets de la temperature d'etirage et l'ajout du copolymere aleatoire sur les proprietes des feuilles. Le type de cristaux (spherulites ou fibrilles) a ete etudie a l'aide de la calorimetrie a balayage differentiel (CBD). Le processus d'etirage a produit une structure cristalline fibrillaire fortement orientee, menant a une augmentation du point de fusion des feuilles d'environ 10°C. Les feuilles etirees a 140°C ont revele des lamelles et fibrilles coexistantes, tandis qu'a 110°C, on a observe principalement une structure fibrillaire. Les mesures de la traction ont indique une resistance superieure pour l'echantillon etire a une temperature basse (c.-a-d., 110°C). On a egalement explore l'effet de la temperature d'etirage et du contenu en copolymere sur la resistance au dechirement. La feuille de PP de poids moleculaire moyen etiree a 110°C a demontre une resistance au dechirement superieur qu'a 140°C. L'ajout du copolymere aleatoire dans le PP de poids moleculaire moyen a reduit la resistance au dechirement de facon considerable, tandis que l'effet pour le poids moleculaire eleve n'etait pas visible. L'ajout du copolymere aleatoire a considerablement reduit le trouble des feuilles et, par consequent, a ameliore radicalement la clarte. Can. J. Chem. Eng. © 2010 Canadian Society for Chemical Engineering

Production of H2 and medium heating value gas via steam gasification of lignins in fixed‐bed reactors

Abstract: In this work, steam gasification of Alcell and Kraft lignins were carried out in a fixed-bed reactor in order to produce H2 and medium heating value gas. The conversion of lignins increased from a low of 64 wt% for Alceil lignin to a high of 88 wt% for Kraft lignin with increasing steam flow rate and temperature. Maximum H2 production of 60.7 mol% was obtained at 800°C and at a steam flow rate of 15 g/h/g of Kraft lignin, whereas maximum heating value of 18000 kl/m3 of the product gas was obtained at 650°C and at 5 g/h/g of Alcell lignin. Also, the performance of a Ni-based steam reforming catalyst for the production of H2 was studied for both types of lignin in a dual fixed-bed reaction system. A maximum H2 production of 63 mol% was obtained at a catalyst bed temperature of 750°C and at a catalyst loading of 0.3 g for Alcell lignin. The sulfur present in Kraft lignin had detrimental effect on the catalyst performance. On a effectue dans ce travail la gazeification a la vapeur de lignines Alcell et Kraft dans un reacteur a lit fixe afin de produire du H2 et du gaz de pouvoir calorifique moyen. La conversion des lignines augmente d'une valeur basse de 64 % en poids pour la lignine Alcell a une valeur haute de 88 % en poids pour la lignine Kraft lorsqu'on augmente le debit de vapeur et la temperature. On obtient une production de H2 maximale de 60,7 mol % a 800°C et a un debit de vapeur de 15 g/h/g de lignine Kraft, tandis qu'une valeur de pouvoir calorifique maximale de 18000 kj/m3 de gaz de produit est obtenue a 650°C et a 5 g/h/g de lignine Alcell. On a egalement etudie la performance d'un catalyseur de reformage a la vapeur base sur du Ni pour la production de H2, pour les deux types de lignines dans un systeme de reaction a lit fixe double. Une production de H2 maximale de 63 % mol % est obtenue a une temperature de lit de catalyseur de 750°C et a une charge de catalyseur de 0,3 g pour la lignine Alcell. Le soufre present dans la lignine Kraft a un effet nuisible sur la performance du catalyseur.

Energy efficient high solids loading agitation for the mineral industry

Abstract: This paper presents results of a study on minimising the specific power for off-bottom solids suspension in mixing tanks at a high solids concentration. It was found that major savings in the specific power required to suspend solids at high concentrations can be achieved by removal of baffles. This is particularly relevant to applications where chemical reaction rate is not affected by the mixing rate, such as that often occurs in the mineral industry. The specific power at the just off-bottom solids suspension condition was found to decrease with the tank diameter at a rate a lot faster than previously reported in the literature. It appears that a larger power number axial flow impeller is more energy efficient than a lower power one to suspend solids at a very high solids loading. A mineral processing full-scale tank is used as a benchmark in the study. Emphasis was placed on applications to the mineral industry, although results are also relevant to other industrial applications. Cet article presente les resultats d'une etude sur la minimisation de la puissance massique pour une suspension de solides sans contact avec le fond de reservoirs de melange contenant une solution a forte concentration de solides. On a conclu que des economies majeures de puissance massique necessaire pour mettre des solides en suspension a de fortes concentrations pouvaient etre faites en retirant les deflecteurs. Ceci est particulierement pertinent pour les applications dans lesquelles la vitesse de reaction chimique n'est pas affectee par le taux du melange, comme cela se produit suivant dans l'industrie miniere. On a decouvert que dans les conditions exactes de suspension totale des solides, la puissance massique diminuait avec le diametre du reservoir, et ce a un taux beaucoup plus rapide que ceux rapportes dans la litterature. Il semble qu'un agitateur a ecoulement axial de puissance superieure est plus efficient au niveau energetique qu'un agitateur moins puissant pour mettre en suspension des solides a des concentrations tres elevees. Un reservoir de traitement mineral de pleine taille est utilise comme reference pour l'etude. L'emphase a ete placee sur les applications de l'industrie miniere, bien que les resultats soient aussi pertinents pour d'autres applications industrielles.

A pipeline transport correlation for slurries with small but dense particles

Abstract: Most correlations/models for minimum transport or critical velocity of slurry were developed for slurries composed of particles greater than ∼100–200 µm diameter with narrow particle-size distributions which is typical of the minerals industry. Many other process industries handle smaller particles. In particular waste slurries at the U.S. Department of Energy's Hanford Site have broad size distributions and significant fractions of smaller particles. Despite the size of these wastes, recent studies at Pacific Northwest National Laboratory indicate that the small particles might be of sufficient density to pose a significant risk for pipeline deposition and plugging. To allow predictive assessment of deposition of fine dense particles for waste slurry transport at the U.S. DOE Hanford site, a pipeline-transport correlation for critical velocity was developed using a simple power-law between two dimensionless numbers important for slurry transport, the deposition Froude and Archimedes numbers. The correlation accords well with experimental data for slurries with Archimedes numbers <80 and is an adequate pipeline design guide for processing Hanford waste slurry. La plupart des correlations/modeles pour le transport minimum ou la vitesse critique des boues liquides ont ete developpes pour des boues liquides composees de particules de diametre superieur a ∼100–200 µm avec des distributions etroites des tailles des particules qui sont typiques de l'industrie miniere. De nombreuses autres industries de transformation gerent les particules plus petites. En particulier, les boues liquides des dechets du site de Hanford du Departement americain de l'Energie (DOE) presentent de larges distributions de taille et des fractions significatives de particules plus petites. En depit de la taille de ces dechets, des etudes recentes du Pacific Northwest National Laboratory indiquent que les petites particules pourraient etre de densite suffisante pour poser un risque significatif de blocage et de depot des canalisations. Pour permettre une evaluation predictive des depots de petites particules denses pour le transport des boues liquides des dechets au site de Hanford du DOE americain, une correlation pipeline-transport pour la vitesse critique a ete developpee en utilisant une simple relation exponentielle entre deux nombres adimensionnels importants le transport des boues liquides, le depot Froude et les nombres d'Archimede. La correlation correspond bien avec les donnees experimentales pour les boues liquides presentant des nombres d'Archimede <80 et constitue un guide de conception adequat des canalisations pour le traitement des boues liquides des dechets de Hanford.

COD reduction of petrochemical industry wastewater using Fenton's oxidation

Abstract: Reduction of chemical oxygen demand (COD) value of petrochemical industry wastewater (COD ∼11 500 mg/L) by Fenton's oxidation has been investigated. Batch tests were conducted on the effluent samples to determine the optimum process conditions. Fenton's oxidation process was found to effectively reduce the COD by 97.5% in 100 min. Effects of different process parameters: pH, H2O2 dosage, Fe2+ dosage, H2O2/Fe2+ ratio, temperature were investigated. The optimum conditions were at pH 3, H2O2 concentration 3 M, Fe2+ concentration 0.06 M and temperature 30°C. Optimum molar ratio [H2O2/Fe2+] was 50:1. At optimum conditions, 97.5% COD reduction was achieved for the typical effluent sample from nearby industry manufacturing mainly PET resins. On a analyse la reduction de la valeur demande chimique en oxygene (DCO) des eaux usees de l'industrie petrochimique (DCO ∼11 500 mg/L) par oxydation de Fenton. Des essais par lots ont ete realises sur les echantillons d'effluent dans le but de determiner les conditions de processus optimales. On a decouvert que le processus d'oxydation de Fenton a reduit efficacement la DCO de 97,5% en 100 min. Les effets de differents parametres de processus, soit pH, dose de H2O2, dose de Fe2+, rapport H2O2/Fe2+ et temperature ont ete analyses. Les conditions optimales etaient pH 3, concentration de H2O2 3 M, concentration de Fe2+ 0,06 M et temperature 30°C. Le rapport molaire optimal [H2O2/Fe2+] etait de 50:1. A des conditions optimales, on est parvenu a une reduction de DCO de 97,5% pour l'echantillon d'effluent typique de l'industrie a proximite qui fabrique principalement des resines de PET. Can. J. Chem. Eng. © 2010 Canadian Society for Chemical Engineering

The effects of impeller speed and holdup on mean drop size in a mixer settler with spiral‐type impeller

Abstract: An experimental investigation has been carried out in order to analyse the drop size distributions of liquid–liquid dispersion in a single stage mixer settler extractor. In this paper, the effects of the impeller speed and the holdup on mean drops size, D32, have been investigated. D32 was decreased with an increase in the impeller speed. Furthermore, D32 was increased with an increase in the holdup. In addition, a new and modified correlation was established based on these results. The average absolute relative deviation is 3.36%. Une etude experimentale a ete effectuee pour analyser la repartition de la taille des gouttes pour la dispersion liquide-liquide dans un extracteur-decanteur-melangeur a etage unique. Dans cet article, on etudie les effets de la vitesse d'agitation et la retenue d'une goutte de taille moyenne, D32. D32 diminuait avec l'augmentation de la vitesse d'agitation. De plus, D32 augmentait avec l'augmentation de la retenue. Par ailleurs, une correlation nouvelle et modifiee a ete mise en place en se basant sur ces resultats. L'ecart relatif absolu moyen est de 3,36%.

A new methodology for hydrodynamic similarity in bubble columns

Abstract: A new hypothesis has been proposed in this work for hydrodynamic similarity that can be subsequently used for scale-up of bubble column reactors. The proposed hypothesis takes into account both global (by matching overall gas holdup) as well as local hydrodynamics (by matching time-averaged radial profile/cross-sectional distribution of gas holdup) to maintain similarity in two systems. The evaluation of proposed hypothesis has been accomplished utilising advanced diagnostic techniques such as gamma-ray computed tomography (CT) and computer automated radioactive particle tracking (CARPT). In this work, we experimentally demonstrate that similarity based only on global hydrodynamics does not necessarily ensure similar mixing and turbulence in two systems. It is essential to maintain similar global as well as local hydrodynamics. The hydrodynamic similarity that can be obtained by matching the commonly used dimensionless groups was also evaluated at these experimental conditions. Une nouvelle hypothese a ete proposee dans ce travail pour une similitude hydrodynamique qui peut etre utilisee ulterieurement pour la mise a l'echelle des reacteurs a colonnes a bulles. L'hypothese proposee prend en compte a la fois l'hydrodynamique globale (en harmonisant le volume mort general) et locale (en harmonisant le profil radial a moyenne temporelle/la distribution transversale du volume mort) pour maintenir la similitude dans deux systemes. L'evaluation de l'hypothese proposee a ete accomplie en utilisant des techniques diagnostiques avancees comme la tomographie par ordinateur a rayons gamma et le tracage des particules radioactives assiste par ordinateur (CARPT). Dans ce travail, nous demontrons experimentalement que la similitude fondee uniquement sur l'hydrodynamique globale n'assure pas necessairement un melange et une turbulence semblables dans deux systemes. Il est essential de maintenir une hydrodynamique globale et locale semblable. La similitude hydrodynamique que l'on peut obtenir en harmonisant les groupes adimensionnels couramment utilises a egalement ete evaluee a ces conditions experimentales.

Removal of lead ions from aqueous solutions using powdered corn cobs

Abstract: This paper is a report on an investigation conducted on adsorption of lead ions (Pb 2+ ) onto powdered corn cobs (PCC). Corn cobs were collected from a selected location in Nigeria. The corn cobs were crushed and pulverised into different particle sizes. Its compositions and adsorption properties of Pb 2+ onto PCC were studied. The effects of pH, particle size of PCC, and initial concentration of Pb 2+ on the adsorption properties were monitored. The adsorption capacities were analysed by using standard adsorption models. The models were evaluated statistically (total error, coefficient of determination (CD), model of selection criterion (MSC), and root mean square error). The study revealed that PCC contained 2.33%, 86.89%, 10.78%, 0.52%, and 4.56% ash, volatile, moisture, solubility in water, and solubility in 0.25 M of HCl by mass, respectively. Acid digestion of a gram of PCC indicated that PCC contained no chromium and lead, but contained 131 mg Fe, 54.79% carbon, 8.03% hydrogen, 0.41% nitrogen, 0.010 mg of Al, and 1.70 mg calcium. The isotherm models parameters were 28.509 L/mg and 0.141 mg/g; 0.138 mg/g and 11.494 L/mg; 0.142 L/mg and 0.013 mg/g; 0.129 mg/g and 25.641 L/mg, 28.509 L/mg, 3.795 mg/g and 2.336 for Langmuir, Freundlich, Temkin, activated sludge, and Redlich–Peterson. The PCC particle size, initial pH, and initial Pb 2+ concentration had effects on the adsorption parameters. The statistical evaluations showed that the best model for adsorption of lead ions from raw water onto PCC based on lower errors, high CD (0.88), reliability (97.5%), and MSC (1.86) was Freundlich and followed by activated sludge model. It was concluded that PCC is a good adsorbent like powdered eggshell and other carbon-based materials.

Destabilisation of homogeneous bubbly flow in an annular gap bubble column

Abstract: Experimental results are presented to show that there are very significant differences in the mean gas void fractions measured in an open tube and a annular gap bubble column, when operated at the same gas superficial velocity, using a porous sparger. Measurements were carried out in a vertical 0.102 m internal diameter column, with a range of concentric inner tubes to form an annular gap, giving diameter ratios from 0.25 to 0.69; gas superficial velocities in the range 0.014-0.200 m/s were investigated. The mean gas void fraction decreases with increasing ratio of the inner to outer diameter of the annular gap column and the transition to heterogeneous flow occurs at lower gas superficial velocities and lower void fractions. Two reasons are proposed and validated by experimental investigations: (1) the presence of the inner tube causes large bubbles to form near the sparger, which destabilise the homogeneous bubbly flow and reduce the mean void fraction; this was confirmed by deliberately injecting large bubbles into a homogeneous dispersion of smaller bubbles, and (2) the shape of the void fraction profiles changes with gap geometry and this affects the distribution parameter in the drift-flux model. Both of these effects serve to reduce the mean gas void fraction in an annular gap bubble column compared to an open tube at the same gas superficial velocity.

Absorption of water/methanol binary system on ion‐exchange resins

Abstract: Polymeric ion-exchange resins are widely used in important industrial processes for both separation and reaction applications. Due to their particular cross-linked structure, these materials are subjected to a remarkable swelling phenomena when are contacted with polar solvents like methanol or water. The high liquid volume retained and the selectivity towards the absorption of particular substances can results in a significant alteration of the liquid reactive mixture composition when polymeric resins are used as catalysts. In this situation the bulk liquid phase and the absorbed phase are different in composition and the kinetics could be strongly affected as the chemical reaction occurs mainly on the internal surface of the resin particles. The correct description of the kinetics for such systems requires additional information regarding the phase partitioning of the various components between the liquid and the absorbed phase. In this work, experimental absorption data, concerning the binary system methanol-water partitioned in the presence of Amberlyst 15 and Relite CFS, two sulphonic ion-exchange resins, typically used as esterification catalysts, are presented. This mixture is of great interest in the esterification reaction of free fatty acids (FFAs) that is nowadays considered a suitable pre-treatment of cheap feedstock for biodiesel production. The data collected on binary systems water-methanol, at different temperatures, have then been successfully correlated by a multicomponent competitive absorption model that could be useful, in the future, in a wider kinetic study. The same model has also been tested on data taken from the literature.

Optimization of silver cementation yield in fixed bed reactor using factorial design and central composite design

Abstract: This work deals with cementation of silver onto iron grid in fixed bed reactor. The influence of several parameters is studied namely: initial concentration of silver [Ag+]0, flow rate, solution pH, and mass of iron. Moreover, their influence on the yield of the reaction of cementation is investigated statistically by the experimental design in view of industrial application. The estimation and the comparison of the parameter's effects are realised by using two-level factorial design. The analysis of these effects permits to state that the most influential factor is the mass of iron with an effect of (+5.642), the second in the order is the initial concentration of silver ions (Ag+) with an effect of (+4.005), the third is the flow rate of the electrolytic solution with an effect of (+3.824). A central composite design methodology is employed to determine the optimum conditions for a silver cementation yield onto iron grid. For this end, the experimental results were approximated by a second-order model as well as the surface contour plots and surface responses are drowned. The optimal conditions found for initial silver concentration, such as a flow rate, pH of the solution and mass of iron, are respectively: 21.25 mg/L, 4.43 L/min, 3.6 and 50 g. Under these conditions, the obtained silver cementation yield is 96.851%. Ce travail concerne la cementation de l'argent sur une grille de fer dans un reacteur a lit fixe. L'influence de plusieurs parametres est etudiee, a savoir: la concentration initiale d'argent [Ag+]0, le debit, le pH de la solution et la masse du fer. De plus, leur influence sur le rendement de la reaction de la cementation est analysee de facon statistique par le plan experimental en egard a l'application industrielle. L'estimation et la comparaison des effets des parametres sont realisees en utilisant un plan factoriel a deux niveaux. L'analyse de ces effets permet de declarer que le facteur presentant le plus d'influence est la masse du fer avec un effet de (+5.642), le deuxieme dans l'ordre est la concentration initiale d'ions argent (Ag+) avec un effet de (+4.005), le troisieme est le debit de la solution electrolytique avec un effet de (+3.824). Une methodologie de plan composite centrale est utilisee pour determiner les conditions optimales pour un rendement de cementation de l'argent dans la grille en fer. A cette fin, les resultats experimentaux ont ete approximes par un modele de deuxieme ordre ainsi que les traces de lignes hypsometriques et les reponses de surface sont inondees. Les conditions optimales que l'on trouve pour la concentration d'argent initiale, comme le debit, le pH de la solution et la masse de fer sont respectivement: 21,25 mg/L, 4,43 L/min, 3,6 et 50 g. Dans ces conditions, le rendement de cementation d'argent obtenu est de 96,851%.