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Slurry Concentration (slurry + concentration)
Selected AbstractsGas-Liquid Mass Transfer in a Slurry Bubble Column at High Slurry Concentrations and High Gas VelocitiesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2005C. O. Vandu Abstract The volumetric mass transfer coefficient kLa in a 0.1,m-diameter bubble column was studied for an air-slurry system. A C9 -C11n -paraffin oil was employed as the liquid phase with fine alumina catalyst carrier particles used as the solid phase. The n -paraffin oil had properties similar to those of the liquid phase in a commercial Fischer-Tropsch reactor under reaction conditions. The superficial gas velocity UG was varied in the range of 0.01 to 0.8,m/s, spanning both the homogeneous and heterogeneous flow regimes. The slurry concentration ,S ranged from 0 to 0.5. The experimental results obtained show that the gas hold-up ,G decreases with an increase in slurry concentration, with this decrease being most significant when ,S < 0.2. kLa/,G was found to be practically independent of the superficial gas velocity when UG > 0.1,m/s is taking on values predominantly between 0.4 and 0.6,s,1 when ,S = 0.1 to 0.4, and 0.29,s,1, when ,S = 0.5. This study provides a practical means for estimating the volumetric mass transfer coefficient kLa in an industrial-size bubble column slurry reactor, with a particular focus on the Fischer-Tropsch process as well as high gas velocities and high slurry concentrations. [source] Behaviour and mechanism of Zn(II) adsorption on Chinese loess at dilute slurry concentrationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Xiaowu Tang Abstract BACKGROUND: Zn(II) is commonly present in mining drainage in developing countries. Since loess is abundant and always located near mining sites in China, it would be useful to investigate the possibility and efficiency of using loess to remove Zn(II) from aqueous solution. RESULTS: The Zn(II) adsorption capacity of Chinese loess was determined as 215.9 mg g,1. The adsorption followed pseudo-second-order kinetics and took place mainly by surface diffusion. Generally, higher initial pH and solute concentration resulted in higher % Zn(II) removal, while higher temperature and slurry concentration led to lower % Zn(II) removal. A thermodynamic study revealed that the adsorption process was exothermic, with the predicted enthalpy change ranging from ,20.87 to ,4.06 kJ mol,1. With the assistance of X-ray photoelectron spectroscopy and X-ray diffraction, the high adsorption capacity was ascribed to the growth of micro-organisms and mineral constituents such as kaolinite and goethite. CONCLUSION: Chinese loess proved effective for Zn(II) adsorption in this study. The optimal adsorption conditions included pH > 3.0, temperature ,15 °C and contact time , 400 min. As an abundant natural soil in arid areas with very low population density, it would be appropriate to develop this material into a wastewater-purifying agent. Copyright © 2008 Society of Chemical Industry [source] OPTIMIZATION OF SPRAY DRYING CONDITIONS FOR PRODUCTION OF BIFIDUS MILK POWDER FROM COW MILKJOURNAL OF FOOD QUALITY, Issue 4 2006M. SELVAMUTHUKUMARAN ABSTRACT Bifidus milk powder was prepared by supplementing cow's milk with predetermined level of additives to obtain slurry of desired concentration. The slurry was sterilized, cooled and inoculated with 24-h-old bulk culture of Bifidobacterium bifidum at 10% and incubated at 37C for 24 h, cooled and dried in SM Scientech Lab model spray dryer with predetermined spray drying conditions. The bifidus milk powder contains bifidobacteria counts from 1.88 × 109 to 15.80 × 109 cells/g dry weight and their percent survival was 4.17,35.11%. Maximum survival was obtained by using the following spray drying conditions: inlet temperature of 164.02C, slurry concentration of 25.62% total soluble solids and air pressure of 2.5 kg/cm2. The high temperature and air pressure of spray drying markedly influenced the color and appearance of final product. The inlet temperature and air pressure showed a significant effect on survival of bifidobacteria in the final product. [source] Synthesis of Porous Silicon Nitride with Unidirectionally Aligned Channels Using Freeze-Drying ProcessJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2002Takayuki Fukasawa Porous silicon nitride with macroscopically aligned channels was synthesized using a freeze-drying process. Freezing of a water-based slurry of silicon nitride was done while unidirectionally controlling the growth direction of the ice. Pores were generated subsequently by sublimation of the columnar ice during freeze-drying. By sintering this green body, a porous silicon nitride with high porosity (over 50%) was obtained and its porosity was controllable by the slurry concentration. The porous Si3N4 had a unique microstructure, where macroscopically aligned open pores contained fibrous grains protruding from the internal walls of the Si3N4 matrix. It is hypothesized that vapor/solid phase reactions were important to the formation mechanism of the fibrous grains. [source] Gas hold-up in bubble columns: Operation with concentrated slurries versus high viscosity liquidTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2000Rajamani Krishna Abstract The hydrodynamics of bubble columns with concentrated slurries of paraffin oil (density, ,L = 790 kg/m3; viscosity, ,L = 0.0029 Pa·s; surface tension, , = 0.028 N·m1) containing silica particles (mean particle diameter dp = 38 ,m) has been studied in columns of three different diameters, 0.1, 0.19 and 0.38 m. With increasing particle concentration, the total gas hold-up decreases significantly. This decrease is primarily caused by the destruction of the small bubble population. The hold-up of large bubbles is practically independent of the slurry concentration. The measured gas hold-up with the 36% v paraffin oil slurry shows remarkable agreement with the corresponding data obtained with Tellus oil (,L = 862 kg/m3; ,L = 0.075 Pa·s; , = 0.028 N·m,1) as the liquid phase. Dynamic gas disengagement experiments confirm that the gas dispersion in Tellus oil also consists predominantly of large bubbles. The large bubble hold-up is found to decrease significantly with increasing column diameter. A model is developed for estimation of the large bubble gas hold-up by introduction of an wake-acceleration factor into the Davies-Taylor-Collins relation (Collins, 1967), describing the influence of the column diameter on the rise velocity of an isolated spherical cap bubble. On a étudié dans des colonnes de trois diamètres différents, soient 0,1, 0,19 et 0,38 m, l'hydrodynamique de colonnes à bulles avec des suspensions concentrées d'huile de paraffine (masse volumique, ,L = 790 kg/m3; viscosité, ,L = 0,0029 Pa·s; tension de surface, , = 0,028 N·m,1) contenant des particules de silice (diamètre moyen des particules dp = 38 ,m). Lorsque la concentration de particules augmente, la rétention de gaz totale diminue considérablement. Cette diminution est principalement due à la destruction de la population de petites bulles. La rétention de grosses bulles est pratiquement indépendante de la concentration des suspensions. La rétention de gaz mesurée avec la suspension d'huile paraffine à 36% volumique concorde remarquablement bien avec les données correspondantes obtenues avec de l'huile de Tellus (,L = 86 kg/m,3; ,L = 0,075 Pa·s; , = 0,028 N·m,1) comme phase liquide. Des expériences de dégagement de gaz dynamiques confirment que la dispersion dans l'huile de Tellus se compose essentiellement de grosses bulles. On a trouvé que la rétention de grosses bulles diminuait de manière significative avec l'augmentation du diamètre de la colonne. On a mis au point un modèle pour l'estimation de la rétention de grosses bulles de gaz par l'introduction d'un facteur d'accélération dans le sillage dans la relation de Davies-Taylor-Collins (Collins, 1967), décrivant l'influence du diamètre de colonne sur la vitesse de montée d'une bulle à t,te sphérique isolée. [source] Gas-Liquid Mass Transfer in a Slurry Bubble Column at High Slurry Concentrations and High Gas VelocitiesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2005C. O. Vandu Abstract The volumetric mass transfer coefficient kLa in a 0.1,m-diameter bubble column was studied for an air-slurry system. A C9 -C11n -paraffin oil was employed as the liquid phase with fine alumina catalyst carrier particles used as the solid phase. The n -paraffin oil had properties similar to those of the liquid phase in a commercial Fischer-Tropsch reactor under reaction conditions. The superficial gas velocity UG was varied in the range of 0.01 to 0.8,m/s, spanning both the homogeneous and heterogeneous flow regimes. The slurry concentration ,S ranged from 0 to 0.5. The experimental results obtained show that the gas hold-up ,G decreases with an increase in slurry concentration, with this decrease being most significant when ,S < 0.2. kLa/,G was found to be practically independent of the superficial gas velocity when UG > 0.1,m/s is taking on values predominantly between 0.4 and 0.6,s,1 when ,S = 0.1 to 0.4, and 0.29,s,1, when ,S = 0.5. This study provides a practical means for estimating the volumetric mass transfer coefficient kLa in an industrial-size bubble column slurry reactor, with a particular focus on the Fischer-Tropsch process as well as high gas velocities and high slurry concentrations. [source] Behaviour and mechanism of Zn(II) adsorption on Chinese loess at dilute slurry concentrationsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Xiaowu Tang Abstract BACKGROUND: Zn(II) is commonly present in mining drainage in developing countries. Since loess is abundant and always located near mining sites in China, it would be useful to investigate the possibility and efficiency of using loess to remove Zn(II) from aqueous solution. RESULTS: The Zn(II) adsorption capacity of Chinese loess was determined as 215.9 mg g,1. The adsorption followed pseudo-second-order kinetics and took place mainly by surface diffusion. Generally, higher initial pH and solute concentration resulted in higher % Zn(II) removal, while higher temperature and slurry concentration led to lower % Zn(II) removal. A thermodynamic study revealed that the adsorption process was exothermic, with the predicted enthalpy change ranging from ,20.87 to ,4.06 kJ mol,1. With the assistance of X-ray photoelectron spectroscopy and X-ray diffraction, the high adsorption capacity was ascribed to the growth of micro-organisms and mineral constituents such as kaolinite and goethite. CONCLUSION: Chinese loess proved effective for Zn(II) adsorption in this study. The optimal adsorption conditions included pH > 3.0, temperature ,15 °C and contact time , 400 min. As an abundant natural soil in arid areas with very low population density, it would be appropriate to develop this material into a wastewater-purifying agent. Copyright © 2008 Society of Chemical Industry [source] Gas-Liquid Mass Transfer in a Slurry Bubble Column at High Slurry Concentrations and High Gas VelocitiesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 9 2005C. O. Vandu Abstract The volumetric mass transfer coefficient kLa in a 0.1,m-diameter bubble column was studied for an air-slurry system. A C9 -C11n -paraffin oil was employed as the liquid phase with fine alumina catalyst carrier particles used as the solid phase. The n -paraffin oil had properties similar to those of the liquid phase in a commercial Fischer-Tropsch reactor under reaction conditions. The superficial gas velocity UG was varied in the range of 0.01 to 0.8,m/s, spanning both the homogeneous and heterogeneous flow regimes. The slurry concentration ,S ranged from 0 to 0.5. The experimental results obtained show that the gas hold-up ,G decreases with an increase in slurry concentration, with this decrease being most significant when ,S < 0.2. kLa/,G was found to be practically independent of the superficial gas velocity when UG > 0.1,m/s is taking on values predominantly between 0.4 and 0.6,s,1 when ,S = 0.1 to 0.4, and 0.29,s,1, when ,S = 0.5. This study provides a practical means for estimating the volumetric mass transfer coefficient kLa in an industrial-size bubble column slurry reactor, with a particular focus on the Fischer-Tropsch process as well as high gas velocities and high slurry concentrations. [source] | ||||||||||