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Stirred-tank Reactor (stirred-tank + reactor)
Selected AbstractsSimple model to predict gel formation in olefin-diene copolymerizations catalyzed by constrained-geometry complexesAICHE JOURNAL, Issue 5 2010Job D. Guzmán Abstract We have developed an analytical model to predict the onset of gel formation in ethylene/1-octene/1,9-decadiene terpolymerizations using constrained-geometry catalysts. The model relies on three kinetic parameters to characterize the catalyst response. Polymer resins have been synthesized in a continuous stirred-tank reactor to determine the model parameters, and to validate the model predictions for polymer properties and for the onset of gel formation and reactor fouling. The experimental results indicate that the free double bonds in 1,9-decadiene are as reactive as those found in 1-octene, and that the reactivity of 1,9-decadiene double bonds decreases after the 1,9-decadiene molecules become part of a polymer chain. The model predictions of polymer properties agree well with chromatographic, density, and mass-balance data. Moreover, the model was successful in preventing unintended reactor fouling during the duration of the experimental campaign. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Oxygen delignification kinetics: CSTR and batch reactor comparisonAICHE JOURNAL, Issue 10 2007Yun Ji Abstract In the past, oxygen delignification studies were mostly performed in batch reactors, whereby the caustic and dissolved oxygen concentrations are changing during the reaction. Also the lignin content and cellulose degradation of the pulp are only established at the end of an experiment when the sample is removed from the reactor. To overcome these deficiencies, a differential reactor system (called Berty reactor) has been adopted. In this continuous stirred-tank reactor (CSTR), the dissolved oxygen concentration and the alkali concentration in the feed are kept constant, and the rate of lignin removal is determined from the dissolved lignin concentration in the outflow stream measured by UV,vis spectroscopy. The delignification rate is found to be first-order in HexA-free residual lignin content. The delignification rate reaction order in [NaOH] and oxygen pressure are 0.412 ± 0.060 and 0.305 ± 0.260 respectively. The activation energy is 54.5 ± 6.8 kJ/mol. © 2007 American Institute of Chemical Engineers AIChE J, 2007 [source] Municipal sludge degradation kinetic in thermophilic CSTRAICHE JOURNAL, Issue 12 2006Ángeles de la Rubia Abstract The performance of a pilot-scale continuous-flow stirred-tank reactor (CSTR) treating municipal sludge under thermophilic conditions has been studied. Two pilot-scale reactors (CSTR1 (175 L) and CSTR2 (850 L)) were operated at different hydraulic residence times (,: 40 to 15 days). The anaerobic sludge processes are generally affected by variations in the concentration of substrate (determined as influent volatile solids, VS) and volumetric flow, both of which lead to a modification in biomass concentration and VS removal efficiency. This unsteady-state situation is mathematically explained in terms of an autocatalytic kinetic model. The general kinetic equation in this model has been applied to experimental data obtained in CSTR1. The fit of the experimental data to the model was used to estimate kinetic parameters and the yield coefficients (,max, ,, YP/S). The estimated parameters were ,max: 0.175d,1, ,: 0.358, YP/S: 0.309 m3CH4/kgVS). These parameters were subsequently used to model the substrate utilization rate and the methane generation rate in CSTR2. The model with the estimated parameters was found to provide excellent results, and is satisfactory in describing the concentration of VS and the methane generation rate in an actual digestion plant. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] Game theoretic approach to multiobjective designs: Focus on inherent safetyAICHE JOURNAL, Issue 1 2006Anjana Meel Abstract A method for designing processes that are inherently safer,with the primary focus on disturbances having the potential for unbounded hazardous responses,is introduced. In cases where safety is not threatened (as in isothermal fermentation reactors), but product quality can rapidly degrade, this method provides designs that ensure high product quality (as in pharmaceutical processes). Using game theory, the method accounts for the trade-offs in profitability, controllability, safety and/or product quality, and flexibility. For nonlinear processes that are hard to control; that is, have an unstable and/or nonminimum-phase steady state, over a wide range of operating conditions, extended bifurcation diagrams are introduced. When a steady state is nonminimum phase, the process may exhibit inverse response. The steady states of processes are classified on the basis of instability and nonminimum-phase behavior to segregate the operating regimes into distinct zones. Locally optimal designs, one corresponding to each zone, are obtained first. These are compared with other locally optimal designs at alternate operating conditions, and/or process reconfigurations, to obtain the globally optimal design using game theory. Four indices,profitability, controllability, safety and/or product quality, and flexibility,characterize the optimality of a design. A novel index for safe operation and/or product quality at a steady state is formulated as a function of the eigenvalues of the Jacobian of the process model and the Jacobian of the process zero dynamics, providing a quantitative measure of instability and nonminimum-phase behavior. The application of the proposed method to an isothermal, continuous stirred-tank reactor (CSTR) with van der Vusse reactions, an exothermic CSTR, and an anaerobic fermentor with substrate and product inhibition is presented. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Interpolated controllers for the robust transition control of a class of reactorsAICHE JOURNAL, Issue 1 2006Guillermo Fernández-Anaya Abstract Two new theoretical results about interpolated controllers for the transition control and simultaneous stabilization of single input-single output plants with variable operating conditions are shown; recent results are generalized for interpolated controllers. On the basis of these results, an application to the closed-loop transition control of a continuous stirred-tank reactor, where a single exothermic reaction takes place, is presented. A comparison with simple PI controllers is made. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Screening of Different Titanium (IV) Catalysts in the Synthesis of Poly(ethylene terephthalate)MACROMOLECULAR REACTION ENGINEERING, Issue 6 2008Fatemeh Ahmadnian Abstract The polycondensation of bis(hydroxyethylene) terephthalate and its oligomers to PET catalyzed by different chelated and non-chelated titanium catalysts in a lab-scale stirred-tank reactor and differential scanning calorimeter were investigated. Different titanium compounds showed different activity and selectivity. The nature of catalyst ligands plays an important role in catalyst efficiency. Non-chelated titanium derivatives were more active and less selective. Reaction progress is characterized by an initial inhibition period depending on the type of catalyst. The original titanium compounds used are precursors and are probably activated by a ligand exchange reaction. [source] Optimization of fed-batch parameters and harvest time of CHO cell cultures for a glycosylated product with multiple mechanisms of inactivationBIOTECHNOLOGY & BIOENGINEERING, Issue 2 2007Ryan S. Senger Abstract Optimization of fed-batch feeding parameters was explored for a system with multiple mechanisms of product inactivation. In particular, two separate mechanisms of inactivation were identified for the recombinant tissue-type activator (r-tPA) protein. Dynamic inactivation models were written to describe particular r-tPA glycoform inactivation in the presence and absence of free-glucose. A glucose-independent inactivation mechanism was identified, and inactivation rate constants were found dependent upon the presence of glycosylation of r-tPA at N184. Inactivation rate constants of the glucose-dependent mechanism were not affected by glycosylation at N184. Fed-batch optimization was performed for r-tPA production by CHO cell culture in a stirred-tank reactor with glucose, glutamine and asparagine feed. Feeding profiles in which culture supernatant concentrations of free-glucose and amino acids (combined glutamine and asparagine) were used as control variables, were evaluated for a wide variety of set points. Simulation results for a controlled feeding strategy yielded an optimum at set points of 1.51 g L,1 glucose and 1.18 g L,1 of amino acids. Optimization was also performed in absence of metabolite control using fixed feed-flow rates initiate during the exponential growth phase. Fixed feed-flow results displayed a family of optimum solutions along a mass flow rate ratio of 3.15 of glucose to amino acids. Comparison of the two feeding strategies showed a slight advantage of rapid feeding at a fixed flow rate as opposed to metabolite control for a product with multiple mechanisms of inactivation. Biotechnol. Bioeng. 2007;98: 378,390. © 2007 Wiley Periodicals, Inc. [source] Rapid media transition: An experimental approach for steady state analysis of metabolic pathwaysBIOTECHNOLOGY PROGRESS, Issue 1 2010Hannes Link Abstract Commonly steady state analysis of microbial metabolism is performed under well defined physiological conditions in continuous cultures with fixed external rates. However, most industrial bioprocesses are operated in fed-batch mode under non-stationary conditions, which cannot be realized in chemostat cultures. A novel experimental setup,rapid media transition,enables steady state perturbation of metabolism on a time scale of several minutes in parallel to operating bioprocesses. For this purpose, cells are separated from the production process and transferred into a lab-scale stirred-tank reactor with modified environmental conditions. This new approach was evaluated experimentally in four rapid media transition experiments with Escherichia coli from a fed-batch process. We tested the reaction to different carbon sources entering at various points of central metabolism. In all cases, the applied substrates (glucose, succinate, acetate, and pyruvate) were immediately utilized by the cells. Extracellular rates and metabolome data indicate a metabolic steady state during the short-term cultivation. Stoichiometric analysis revealed distribution of intracellular fluxes, which differs drastically subject to the applied carbon source. For some reactions, the variation of flux could be correlated to changes of metabolite concentrations. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Combined Effect of Agitation/Aeration and Fed-Batch Strategy on Ubiquin- one-10 Production by Pseudomonas diminutaCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2010Mahesh V. Bule Abstract The effects of aeration rate and agitation speed on ubiquinone-10 (CoQ10) submerged fermentation in a stirred-tank reactor using Pseudomonas diminuta NCIM 2865 were investigated. CoQ10 production, biomass formation, glycerol utilization, and volumetric mass transfer coefficient (kLa) were affected by both aeration and agitation. An agitation speed of 400,rpm and aeration rate of 0.5,vvm supported the maximum production (38.56,mg,L,1) of CoQ10 during batch fermentation. The fermentation run supporting maximum production had an kLa of 27.07,h,1 with the highest specific productivity and CoQ10 yield of 0.064,mg,g,1h,1 and 0.96,mg,g,1 glycerol, respectively. Fermentation kinetics performed under optimum aeration and agitation showed the growth-associated constant (a,=,5.067,mg,g,1) to be higher than the nongrowth-associated constant (,,=,0.0242,mg,g,1h,1). These results were successfully utilized for the development of fed-batch fermentation, which increased the CoQ10 production from 38.56,mg,L,1 to 42.85,mg,L,1. [source] Microbial community structure of ethanol type fermentation in bio-hydrogen productionENVIRONMENTAL MICROBIOLOGY, Issue 5 2007Nanqi Ren Summary Three continuous stirred-tank reactors (CSTRs) were used for H2 production from molasses wastewater at influent pH of 6.0,6.5 (reactor A), 5.5,6.0 (reactor B), or 4.0,4.5 (reactor C). After operation for 28 days, the microbial community formed ethanol type (C), propionate type (A) and ethanol-butyrate-mixed type (B) fermentation. The H2 production rate was the highest for ethanol type fermentation, 0.40 l (g VSS),1 day,1 or 0.45 l H2 (g COD removed),1. Microbial community dynamics and diversity were analysed using double-gradient denaturing gradient gel electrophoresis (DG-DGGE). Denaturing gradient gel electrophoresis profiles indicated that the community structures changed quickly in the first 14 days. Phylogenetic analysis indicated that the dominant bacterial groups were low G+C Gram-positive bacteria, Bacteroides, ,-Proteobacteria and Actinobacteria; ,-Proteobacteria, ,-Proteobacteria, ,-Proteobacteria and Spirochaetes were also presented as minor groups in the three reactors. H2 -producing bacteria were affiliated with Ethanoligenens, Acetanaerobacterium, Clostridium, Megasphaera, Citrobacter and Bacteroides. An ethanol-based H2 -producing bacterium, Ethanoligenens harbinense CGMCC1152, was isolated from reactor C and visualized using fluorescence in situ hybridization (FISH) to be 19% of the eubacteria in reactor C. In addition, isoenzyme activity staining for alcohol dehydrogenase (ADH) supported that the majority of ethanol-producing bacteria were affiliated with Ethanoligenens in the microbial community. [source] Characterization of flow conditions in 2 L and 20 L wave bioreactors® using computational fluid dynamicsBIOTECHNOLOGY PROGRESS, Issue 1 2010Alper A. Öncül Abstract Characterization of flow conditions is of great importance to control cell growth and cell damage in animal cell culture because cell viability is influenced by the flow properties in bioreactors. Alternative reactor types like Wave Bioreactors® have been proposed in recent years, leading to markedly different results in cell growth and product formation. An advantage of Wave Bioreactors® is the disposability of the Polyethylenterephthalet-bags after one single use (fast setup of new production facilities). Another expected advantage is a lower shear stress compared to classical stirred-tank reactors, due to the gentle liquid motion in the rocking cellbag. This property would considerably reduce possible cell damage. The purpose of the present study is to investigate in a quantitative manner the key flow properties in Wave Bioreactors®, both numerically and experimentally. To describe accurately flow conditions and shear stress in Wave Bioreactors® using numerical simulations, it is necessary to compute the unsteady flow applying Computational Fluid Dynamics (CFD). Corresponding computations for two reactor scales (2 L and 20 L cellbags) are presented using the CFD code ANSYS-FLUENT®. To describe correctly the free liquid surface, the present simulations employ the Volume of Fluid (VOF) method. Additionally, experimental measurements have been carried out to determine liquid level, flow velocity and liquid shear stress, which are used as a validation of the present CFD simulations. It is shown that the obtained flows stay in the laminar regime. Furthermore, the obtained shear stress levels are well below known threshold values leading to damage of animal cells. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] | |||||||||||||