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Operating Variables (operating + variable)
Selected AbstractsSolid,liquid mass transfer characteristics of an unbaffled agitated vessel with an unsteadily forward,reverse rotating impellerJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008Shuichi Tezura Abstract To develop an enhanced form of solid-liquid apparatus, an unbaffled agitated vessel has been constructed, fitted with an agitation system using an impeller whose rotation alternates unsteadily in direction, i.e. a forward-reverse rotating impeller. In this vessel, solid-liquid mass transfer was studied using a disc turbine impeller with six flat blades. The effect of impeller rotation rate as an operating variable on the mass transfer coefficient was evaluated experimentally using various geometrical conditions of the apparatus, such as impeller diameter and height, in relation to the impeller power consumption. Mixing of gas above the free surface into the bulk liquid, i.e. surface aeration, which accompanied the solid-liquid agitation, was also investigated. Comparison of the mass transfer characteristics between this type of vessel and a baffled vessel with a unidirectional rotating impeller underscored the sufficient solid-liquid contact for prevention of gas mixing in the forward-reverse rotation mode of the impeller. Copyright © 2008 Society of Chemical Industry [source] Testing a Vapour-fed PBI-based Direct Ethanol Fuel CellFUEL CELLS, Issue 5 2009J. Lobato Abstract This work is focused on the application and performance of a high temperature PBI-based direct ethanol fuel cell, studying the influence of some operating variables such as the temperature, ethanol concentration and oxygen partial pressure. An increase in the temperature resulted in an improvement of the cell performance due to the enhanced electrodic kinetic and electrolyte conductivity. An ethanol/water weight ratio between 0.25 and 0.5 was found to be suitable for providing both enough water and fuel availability to make the ethanol oxidation possible. Measurements of the ethanol crossover at different temperatures and concentrations were carried out. An intermittent lifetime test showed that the cell, after several hours, was able to reach stability. Moreover, its performance was completely reversible with no perceptible losses for 7,days. Finally, tests using bio-ethanol as fuel were performed, with no significant power losses. This final feature is of special interest from a practical ,green' point of view. [source] Parametric analysis of a coal based combined cycle power plantINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 1 2006T. Srinivas Abstract In the present paper thermodynamic analyses, i.e. both energy and exergy analyses have been conducted for a coal based combined cycle power plant, which consists of pressurized circulating fluidized bed (PCFB) partial gasification unit and an atmospheric circulating fluidized bed (ACFB) char combustion unit. Dual pressure steam cycle is considered for the bottoming cycle to reduce irreversibilities during heat transfer from gas to water/steam. The effect of operating variables such as pressure ratio, gas turbine inlet temperature on the performance of combined cycle power plant has been investigated. The pressure ratio and maximum temperature (gas turbine inlet temperature) are identified as the dominant parameters having impact on the combined cycle plant performance. The work output of the topping cycle is found to increase with pressure ratio, while for the bottoming cycle it decreases. However, for the same gas turbine inlet temperature the overall work output of the combined cycle plant increases up to a certain pressure ratio, and thereafter not much increase is observed. The entropy generation, the irreversibilities in each component of the combined cycle and the exergy destruction/losses are also estimated. Copyright © 2005 John Wiley & Sons, Ltd. [source] Evaluation of a novel Bacillus strain from a north-western Spain hot spring as a source of extracellular thermostable lipaseJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 10 2009Francisco J. Deive Abstract BACKGROUND: Thermophilic microorganisms are receiving significant attention as a source of useful thermostable enzymes. However, the number of known strains is still limited, and very often their most interesting biocatalysts are intracellular or membrane-bound and produced at low levels. Thus, the isolation and study of novel extracellular enzyme-producing thermophilic microorganisms is very interesting. Moreover, the assessment of bioreactor performance is crucial, given the scarce information on the large-scale culture of these strains. RESULTS: The production of a thermostable extracellular lipase in submerged cultures of a thermophilic microorganism, recently isolated in north-west Spain, was investigated. The strain was identified by 16S rDNA sequencing as belonging to genus Bacillus. The influence of operating variables (i.e. pH, temperature, aeration) on lipase biosynthesis was analysed. Enzyme production at bioreactor scale was investigated, special attention being paid to the effect of aeration and agitation rates. CONCLUSION: The best conditions for the studied process were determined in shake flasks as pH 7.0, 55 °C and high aeration levels. Also, the non-association between lipase production and cell growth was ascertained. The culture of this novel strain was successfully carried out in laboratory-scale bioreactors, thus proving its potential for further applications. Copyright © 2009 Society of Chemical Industry [source] Separation of fatty acids from binary melts using physical vapour deposition (PVD)JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2009Young Han Kim Abstract BACKGROUND: The use of fatty acid mixtures, natural biochemical compounds, will be extended to various chemical industries for the production of a wide variety of products, and various mixtures of fatty acids are necessary for production. Separation of a binary fatty acid mixture of lauric acid and myristic acid using physical vapour deposition (PVD) on a cold quartz crystal resonator is examined. The extremely small amount of deposits can be measured with the quartz crystal resonator. The vapour phase is prepared by vaporizing a calculated composition of melt according to the vapour-liquid equilibrium (VLE). RESULTS: The composition of lauric acid in the melt and the melt temperature were utilized as operating variables in the PVD. The growth rate of deposit increases when melt temperature and the composition of lauric acid in the melt are increased. The composition of lauric acid in the deposit is significantly lower than that of the melt of 19% lauric acid, but the composition of lauric acid in the deposit is much higher than that of the melts of 50% and 75% lauric acid. CONCLUSION: The distribution coefficient of lauric acid between solid and vapour phases can be correlated as a function of the growth rate of deposit. The possibility of separation of fatty acid mixtures by PVD is suggested experimentally and theoretically. Copyright © 2008 Society of Chemical Industry [source] Study of operating variables in the transformation of aqueous ethanol into hydrocarbons on an HZSM-5 zeoliteJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 2 2002Andres T Aguayo Abstract With the aim of determining the possibilities of directly upgrading the liquid obtained from carbohydrate fermentation, the effect of operating conditions (temperature, space time, water content in the feed) has been studied in the catalytic transformation of aqueous ethanol into hydrocarbons on an HZSM-5 zeolite in an isothermal fixed bed reactor. Special attention has been paid to the effect of water content on the yield, product distribution and catalyst deactivation. Although deactivation by coke decreases as the water content is increased, this content must be limited at 450,°C and higher temperatures in order to avoid irreversible deactivation of the catalyst by dealumination. © 2002 Society of Chemical Industry [source] Modeling l-dopa purification by chiral ligand-exchange chromatographyAICHE JOURNAL, Issue 3 2007Nooshafarin Sanaie Abstract A model describing elution-band profiles that combines multiple chemical equilibria theory with the nonideal equilibrium,dispersion equation for solute transport is used to predict and characterize the separation of l,d-dopa by chiral ligand-exchange chromatography (CLEC). Formation constants and stoichiometries for all equilibrium complexes formed in the interstitial volume and pore liquid are taken from standard thermodynamic databases and independent potentiometric titration experiments. Formation constants for complexes formed with the stationary phase ligand (N-octyl-3-octylthio-d-valine) are determined from potentiometric titration data for a water-soluble analogue of the ligand. This set of pure thermodynamic parameters is used to calculate the spatially discretized composition of each column volume element as a function of time. The model includes a temperature-dependent pure-component parameter, determined by regression to a single elution band for the pure component, that corrects for subtle effects associated with immobilizing the N-octyl-3-octylthio-d-valine ligand onto the stationary phase. The model is shown to accurately predict elution chromatograms and separation performance as a function of key column operating variables. The model is then used to better understand the connection between chemical equilibria within the system and changes in band profiles and band separation resulting from changes in column operating conditions. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Data mining of fractured experimental data using neurofuzzy logic,discovering and integrating knowledge hidden in multiple formulation databases for a fluid-bed granulation processJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 6 2008Q. Shao Abstract In the pharmaceutical field, current practice in gaining process understanding by data analysis or knowledge discovery has generally focused on dealing with single experimental databases. This limits the level of knowledge extracted in the situation where data from a number of sources, so called fractured data, contain interrelated information. This situation is particularly relevant for complex processes involving a number of operating variables, such as a fluid-bed granulation. This study investigated three data mining strategies to discover and integrate knowledge "hidden" in a number of small experimental databases for a fluid-bed granulation process using neurofuzzy logic technology. Results showed that more comprehensive domain knowledge was discovered from multiple databases via an appropriate data mining strategy. This study also demonstrated that the textual information excluded in individual databases was a critical parameter and often acted as the precondition for integrating knowledge extracted from different databases. Consequently generic knowledge of the domain was discovered, leading to an improved understanding of the granulation process. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:2091,2101, 2008 [source] A NEW APPROACH TO CORRELATE TEXTURAL AND COOKING PARAMETERS WITH OPERATING CONDITIONS DURING DOUBLE-SIDED COOKING OF MEAT PATTIESJOURNAL OF TEXTURE STUDIES, Issue 5 2000SUSANA E. ZORRILLA Cooking and textural parameters during double-sided cooking of hamburger patties were correlated with volume-averaged temperature at the end of the cooking process and gap thickness between plates. Frozen patties were cooked in a clamshell grill set at different plate surface temperatures (177C; 191C; 204C; 218C), for different gap thicknesses (9.65 mm; 10.55 mm; 10.55 mm; 11.05 mm) for 120 s. A decrease in the gap thickness and an increase in the plate surface temperature resulted in an increase in the cooking loss values (24,36%) and in a decrease of press juice values (8,25%). The values of peak load (183,215 N), modulus (16,19 N/mm), work needed in shearing (2300,2800 Nmm), hardness (25,32 N), cohesiveness (0.76,0.83), and chewiness (107,152 Nmm) of the patties increased when the gap thickness decreased and the plate surface temperature increased. There was no effect of the variables studied on springiness. The correlation equations involving the operating variables and quality parameters obtained are simple and useful in developing optimal process conditions. [source] Process modeling and optimization of industrial ethylene oxide reactor by integrating support vector regression and genetic algorithmTHE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009Sandip Kumar Lahiri Abstract This article presents an artificial intelligence-based process modeling and optimization strategies, namely support vector regression,genetic algorithm (SVR-GA) for modeling and optimization of catalytic industrial ethylene oxide (EO) reactor. In the SVR-GA approach, an SVR model is constructed for correlating process data comprising values of operating and performance variables. Next, model inputs describing process operating variables are optimized using Genetic Algorithm (GAs) with a view to maximize the process performance. The GA possesses certain unique advantages over the commonly used gradient-based deterministic optimization algorithms The SVR-GA is a new strategy for chemical process modeling and optimization. The major advantage of the strategies is that modeling and optimization can be conducted exclusively from the historic process data wherein the detailed knowledge of process phenomenology (reaction mechanism, kinetics, etc.) is not required. Using SVR-GA strategy, a number of sets of optimized operating conditions leading to maximized EO production and catalyst selectivity were obtained. The optimized solutions when verified in actual plant resulted in a significant improvement in the EO production rate and catalyst selectivity. On présente dans cet article des stratégies de modélisation et d'optimisation de procédés reposant sur l'intelligence artificielle, à savoir la méthode basée sur la régression des vecteurs de soutien et l'algorithme génétique (SVR-GA) pour la modélisation et l'optimisation du réacteur d'oxyde d'éthylène (EO) industriel catalytique. Dans la méthode SVR-GA, un modèle de régression des vecteurs de soutien est mis au point pour corréler les données de procédé comprenant les valeurs des variables de fonctionnement et de performance. Par la suite, les données d'entrée du modèle décrivant les variables de fonctionnement du procédé sont optimisées à l'aide de l'algorithme génétique (GA) dans l'optique de maximiser la performance du procédé. Le GA possède certains avantages uniques par rapport aux algorithmes d'optimisation déterministes basés sur les gradients communément utilisés. La SVR-GA est une nouvelle stratégie pour la modélisation et l'optimisation des procédés. Le principal avantage de ces stratégies est que la modélisation et l'optimisation peuvent être menées exclusivement à partir des données de procédés historiques, et il n'est pas nécessaire de connaître en détail la phénoménologie des procédés (mécanisme de réaction, cinétique, etc.). À l'aide de la stratégie SVR-GA, plusieurs séries de conditions opératoires optimisées conduisant à une production d'EO et une sélectivité de catalyseur maximisées ont été obtenues. Les solutions optimisées vérifiées en installations réelles permettent une amélioration significative du taux de production d'EO et de la sélectivité du catalyseur. [source] Equilibrium and kinetic study for the removal of malachite green using activated carbon prepared from Borassus flabellofer male flowerASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 3 2010P. E. Jagadeesh Babu Abstract Activated carbon was prepared from dried Borassus flabellofer male flower and batch adsorption experiments were conducted to study its potential to remove malachite green (MG) dye. The process was further optimized by studying the operating variables like initial pH of the stock solution, activation temperature, initial dye concentration, adsorbent loading and contact time. The optimized pH and activation temperatures were found to be 7.55 and 450 °C respectively, where further analysis was made using these optimal variables. Linear, Freundlich and Langmuir isotherms were studied and it was found that the Langmuir isotherms have the highest correlation coefficients compared to the others. Further, the sorption kinetics were analysed using pseudo-first-order and pseudo-second-order kinetic models. The data showed that the second-order equation was the more appropriate, which indicate that the intra-particle diffusion is the rate limiting factor. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Gas,liquid mass transfer in three-phase inverse fluidized bed reactor with Newtonian and non-Newtonian fluidsASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010V. Sivasubramanian Abstract Liquid-phase volumetric mass transfer coefficients, kLa were determined in three-phase inverse fluidized beds of low-density polyethylene (LDPE) and polypropylene (PP) spheres fluidized by a countercurrent flow of air and Newtonian (water and glycerol solutions) or non-Newtonian liquids [carboxy methyl cellulose (CMC) solutions]. The effects of liquid and gas velocities, particle size, solid loading and addition of organic additives (glycerol and CMC) on the volumetric mass transfer coefficient, kLa were determined. The superficial liquid velocity had a weak effect on the mass transfer whereas the gas flow rate affected the mass transfer positively. kLa increased with increase in particle diameter and decreased with increase in initial bed height (solid loading). kLa decreased as the concentration of glycerol (viscosity) and CMC increased. Empirical correlations are presented to predict the gas,liquid volumetric mass transfer coefficient in terms of operating variables. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Studies on the effect of pH, temperature and metal ions on the production of pectinase from tamarind kernel powder by submerged fermentation using Aspergillus foetidus (NCIM 505)ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2010P. E. JagadeeshBabu Abstract Filamentous fungi Aspergillus foetidus NCIM 505 was studied for its capacity to produce exo-pectinase in submerged fermentation (SMF) from a new substrate of tamarind kernel powder (TKP). The process was further studied to optimize the initial operating variables like pH, time and temperature. Maximum pectinolytic activity was reached at 72 h of growth and the best fungal strain was found to be A. foetidus NCIM 505. Further, to increase the production rate of pectinase, the effects of metal ions were studied. Metal ions like Cu++, Mg++, Fe++, Co++ and Zn++ at different concentrations were used. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source] Multi-objective optimization of an industrial penicillin V bioreactor train using non-dominated sorting genetic algorithmBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2007Fook Choon Lee Abstract Bulk of the penicillin produced is used as raw material for semi-synthetic penicillin (such as amoxicillin and ampicillin) and semi-synthetic cephalosporins (such as cephalexin and cefadroxil). In the present paper, an industrial penicillin V bioreactor train is optimized for multiple objectives simultaneously. An industrial train, comprising a bank of identical bioreactors, is run semi-continuously in a synchronous fashion. The fermentation taking place in a bioreactor is modeled using a morphologically structured mechanism. For multi-objective optimization for two and three objectives, the elitist non-dominated sorting genetic algorithm (NSGA-II) is chosen. Instead of a single optimum as in the traditional optimization, a wide range of optimal design and operating conditions depicting trade-offs of key performance indicators such as batch cycle time, yield, profit and penicillin concentration, is successfully obtained. The effects of design and operating variables on the optimal solutions are discussed in detail. Biotechnol. Bioeng. 2007;98: 586,598. © 2007 Wiley Periodicals, Inc. [source] Cell Separator Operation within Temperature Ranges To Minimize Effects on Chinese Hamster Ovary Cell Perfusion CultureBIOTECHNOLOGY PROGRESS, Issue 6 2007Hans Drouin A cell retention device that provides reliable high-separation efficiency with minimal negative effects on the cell culture is essential for robust perfusion culture processes. External separation devices generally expose cells to periodic variations in temperature, most commonly temperatures below 37 °C, while the cells are outside the bioreactor. To examine this phenomenon, aliquots of ,5% of a CHO cell culture were exposed to 60 s cyclic variations of temperature simulating an acoustic separator environment. It was found that, for average exposure temperatures between 31.5 and 38.5 °C, there were no significant impacts on the rates of growth, glucose consumption, or t-PA production, defining an acceptable range of operating temperatures. These results were subsequently confirmed in perfusion culture experiments for average exposure temperatures between 31.6 and 38.1 °C. A 25,1 central composite factorial design experiment was then performed to systematically evaluate the effects of different operating variables on the inlet and outlet temperatures of a 10L acoustic separator. The power input, ambient temperature, as well as the perfusion and recycle flow rates significantly influenced the temperature, while the cell concentration did not. An empirical model was developed that predicted the temperature changes between the inlet and the outlet of the acoustic separator within ±0.5 °C. A series of perfusion experiments determined the ranges of the significant operational settings that maintained the acoustic separator inlet and outlet temperatures within the acceptable range. For example, these objectives were always met by using the manufacturer-recommended operational settings as long as the recirculation flow rate was maintained above 15 L day,1 and the ambient temperature was near 22 °C. [source] Catalytic Liquid Phase Oxidation of Toluene to Benzoic AcidCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 3 2008A. Gizli Abstract The production of benzoic acid from toluene in the liquid phase with pure oxygen was studied. Investigations have been carried out with a view to determining the most suitable reaction conditions with respect to operating variables including oxygen flow rate, reaction temperature, batch time and catalyst loading. In a series of batch experiments carried out at 4,atm, the optimum values of mole ratio of oxygen to toluene, temperature, reaction time, and catalyst loading were found to be 2, 157,°C, 2,h and 0.57,g/L, respectively. In addition, a kinetic study was carried out by taking into consideration the optimum reaction conditions. The model dependent on the formation of benzyl radical was found to be feasible for describing the catalytic oxidation of toluene to benzoic acid in the liquid phase. The activation energy was determined as 40,kJ/mol. [source] New Predictive Correlations for the Drop Size in a Rotating Disc Contactor Liquid-Liquid Extraction ColumnCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 2 2007M. Ismail Al-Rahawi Abstract Sauter mean drop sizes (d32) generated from a hole distributor in liquid extraction RDC columns were studied under various conditions. Experiments were designed to generate data required to determine the main variables that control the drop sizes in RDCs. Two precise correlations were proposed for predicting d32 in a RDC extraction column. The first was based on operating variables, hole-distributor diameter, disc speed, column geometry, and system physical properties. The second one considered the same variables, except the column geometry. This model can be used for design purposes. The two correlations are the first of their type to consider the distributor hole inlet diameter in a RDC column. This diameter has been neglected by previous investigators. The maximum standard deviation for all data is 0.75,%, with a maximum absolute error of 6.8,%. [source] | |||||||||||||