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Loop Reactor (loop + reactor)

Distribution by Scientific Domains

Chemistry	72%

Kinds of Loop Reactor

airlift loop reactor

Selected Abstracts

Sensitivity Study on Modeling an Internal Airlift Loop Reactor Using a Steady 2D Two-Fluid Model

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 12 2008
Q. Huang
Abstract The sensitivity study of bubbly flow in an internal airlift loop reactor is presented using a steady Reynolds averaging two-fluid model. Comparative evaluation of different drag formulations, drag coefficient correlations, turbulence effect on the drag coefficient, outlet slip velocity, and bubble size is performed and the respective influence to the simulation results is highlighted. It is found that a complicated drag formulation may not result in reliable predictions. All the drag coefficient correlations underpredict the gas holdup if the influence of turbulence on the drag coefficient is not well incorporated. Fortunately, the global hydrodynamics is not sensitive to the outflow slip velocity for a wide range, so a steady two-fluid model can be used to simulate the bubbly flow when the flow field is fully developed. The correct estimation of bubble size with properly selected correlations play an important role in successful simulation of gas-liquid bubbly flow in airlift loop reactors. [source]

Modeling of Kinetic Expressions for the Reduction of NOx by Hydrogen in Oxygen-Rich Exhausts Using a Gradient-Free Loop Reactor

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2003
E. Frank
Abstract The reduction of NOx by hydrogen under lean conditions is investigated in a gradient-free loop reactor. Using this computer-controlled reactor, the reaction rates can be measured under exact isothermal conditions. Systematic variation of the input concentrations of hydrogen, nitric oxide, oxygen as well as reaction temperature provides a complete data set of reaction rates for the given reaction system. A number of kinetic rate expressions were evaluated for their ability to fit the experimental data by using toolboxes of MATLAB. The temperature influence on reaction rate constants and adsorption equilibrium constants were correlated simultaneously using Arrhenius and van't Hoff equations, respectively. The kinetic rate expression based on a Langmuir-Hinshelwood-type model describes the data and the model can be improved by introducing a correction term in square root of hydrogen partial pressure over the range of conditions investigated. [source]

Coupled Single-Particle and Population Balance Modeling for Particle Size Distribution of Poly(propylene) Produced in Loop Reactors

MACROMOLECULAR REACTION ENGINEERING, Issue 2 2010
Zheng-Hong Luo
Abstract A comprehensive model was developed for the PSD of PP produced in loop reactors. The polymeric multilayer model (PMLM) was first applied to calculate the single particle growth rate under intraparticle transfer limitations. In order to obtain the comprehensive model, the PMLM was solved together with a steady-state particle population equation to predict the PSD in the loop reactors. The simulated PSD data obtained under steady-state polymerization conditions agreed with the actual data collected from industrial scale plant. The comprehensive model was also used to predict the effects of some critical factors, including the intraparticle mass and heat transfer limitations, the feed catalyst particle size and the catalyst deactivation, etc., on the PSD. [source]

Preparation of sorbitol from D -glucose hydrogenation in gas,liquid,solid three-phase flow airlift loop reactor

JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2004
Jian-Ping Wen
Abstract A new process for D -glucose hydrogenation in 50 wt% aqueous solution, into sorbitol in a 1.5 m3 gas,liquid,solid three-phase flow airlift loop reactor (ALR) over Raney Nickel catalysts has been developed. Five main factors affecting the reaction time and molar yield to sorbitol, including reaction temperature (TR), reaction pressure (PR), pH, hydrogen gas flowrate (Qg) and content of active hydrogen, were investigated and optimized. The average reaction time and molar yield were 70 min and 98.6% under the optimum operating conditions, respectively. The efficiencies of preparation of sorbitol between the gas,liquid,solid three-phase flow ALR and stirred tank reactor (STR) under the same operating conditions were compared. Copyright © 2004 Society of Chemical Industry [source]

Computational and experimental fluid dynamics of jet loop reactor

AICHE JOURNAL, Issue 10 2009
Channamallikarjun S. Mathpati
Abstract A computational analysis using standard k-, model, RSM and LES has been carried out for jet loop reactors (JLR) to investigate the mean and turbulence quantities. These simulations have revealed that the flow in JLR was different from the self-similar round jets. RSM and LES showed better agreement with PIV measurements compared with standard k-, model. The modeled turbulence production and transport in k-, model overpredicted those estimated from LES data. To reduce the limitations, modified k-, models have been evaluated for JLR. Also, a hybrid k-, model has been suggested, which was found to perform better than other modified k-, models. This model was also found to hold for stirred tank reactors (STRs). Mixing time analysis has been carried out for JLR and STR at same power consumption. It has been shown that JLR can be inferior to STR if proper nozzle diameter is not selected. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

(Mini)emulsion Polymerization: Effect of the Segregation Degree on Polymer Architecture

MACROMOLECULAR REACTION ENGINEERING, Issue 6 2007
Iker González
Abstract A continuous loop reactor was used for the production of 2-ethylhexyl acrylate (2-EHA), methyl methacrylate (MMA) and acrylic acid (AA) pressure sensitive adhesive by both emulsion and miniemulsion polymerization. Similar high monomer conversions were achieved in both processes, but striking differences in polymer architecture were found. A mathematical model was used to analyze these differences concluding that because the costabilizer suppressed monomer diffusion from miniemulsion droplets, the average polymer concentration in the polymerization loci was lower in the miniemulsion process. This resulted in less chain transfer to polymer, and hence in lower sol molecular weight and gel content. [source]

Combined PIV/PTV-Measurements for the Analysis of Bubble Interactions and Coalescence in a Turbulent Flow

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 3-4 2003
Dirk Bröder
Abstract In order to allow more reliable modeling of coalescence processes in turbulent bubbly flows, detailed experiments in a double loop reactor were performed. Narrow and essentially monomodal bubble size distributions in the range of 2 to 4 mm were created. For simultaneous measurements of bubble size, bubble velocity and liquid velocity a combined system of PIV and PTV was developed and applied. It was possible to determine bubble size distributions and mean, as well as fluctuating velocities for both phases. The spatial changes of the bubble size distribution, due to the influence of bubble coalescence, was analyzed and coalescence rates were calculated. Afin d'améliorer la fiabilité de la modélisation des procédés de coalescence dans les écoulements bouillonnants turbulents, des expériences poussées ont été menées dans un réacteur à double boucle. Des distributions de taille des bulles étroites, essentiellement monodisperses, dans la gamme de 2 à 4 mm, ont été créées. Pour les mesures simultanées de la taille des bulles, de la vitesse des bulles et de la vitesse du liquide, on a mis au point et appliqué un système combiné de PIV et PTV. Il a été possible de déterminer les distributions de taille des bulles et la moyenne mais également les vitesses fluctuantes pour les deux phases. Les changements spatiaux de la distribution de la taille des bulles dus à l'influence de la coalescence des bulles ont été analysés et les vitesses de coalescence ont été calculées. [source]

Study on flow patterns in different types of direct coal liquefaction reactors

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2009
Xiangkun Ren
Abstract Hot mold flow patterns in bubble reactor, ebullated reactor and loop reactor have been researched and compared in hydrogen,oil system and hydrogen,oil coal slurry system of direct coal liquefaction (DCL) pilot plant under high temperature and high pressure. The results demonstrate that the ebullated reactor and loop reactor (on the condition of optimum recycle ratio) show good performance of back-mixing, which can not only reduce temperature differences between top and bottom in the reactor, but also avoid big solid particles deposition that easily occurs during liquefaction process. The ebullated reactor used in the first demonstration plant has good performance. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Design of a Tubular Loop Bioreactor for Scale-up and Scale-down of Fermentation Processes

BIOTECHNOLOGY PROGRESS, Issue 5 2003
Maria Papagianni
Microorganisms traveling through circulation loops in large-scale bioreactors experience variations in their environment such as dissolved oxygen concentration and pH gradients. The same changes are not experienced in small bioreactors, and it is suggested that herein lies one of the major reasons for the problems encountered when translating fermentation data from one scale to another. One approach to study this problem is to look at the circulation loop itself. The present work concerns an attempt to simulate the circulation loops inside stirred tank reactors, using a tubular loop reactor specially constructed for the purpose. The reactor carries a number of ports and probes along its length for the determination of concentration gradients within. The broth is circulated around the loop by the use of peristaltic pumps, and the circulation time (tc, s) is used as a measure of simulated reactor size. The reactor system has been evaluated using the citric acid fermentation by Aspergillus niger as a test process. Acid production and fungal morphology, in terms of the mean convex perimeter of mycelial clumps quantified by image analysis, were used as the parameters of evaluation for the two systems in comparison. From comparative experiments carried out in 10 and 200 L stirred tank bioreactors, it appears that the loop reactor simulates the corresponding stirred tank representing a valuable tool in scaling up and scaling down of fermentation process. [source]

Sensitivity Study on Modeling an Internal Airlift Loop Reactor Using a Steady 2D Two-Fluid Model

Incorporation of Dynamic Flexibility in the Design of a Methanol Synthesis Loop in the Presence of Catalyst Deactivation

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2008
P. Parvasi
Abstract A typical methanol loop reactor is analyzed in this study. All basic equipment in the Lurgi-type methanol loop is included in the proposed model. A detailed dynamic model described by a set of ordinary differential and algebraic equations is developed to predict the behavior of the overall process. The model is validated against plant data. A new deactivation model is proposed and its parameters are estimated using daily plant data. The interesting feature of this model is that it incorporates the effect of carbon dioxide and carbon monoxide on the catalyst deactivation. Using the model, the effect of various factors to compensate for the reduction of production rate due to catalyst deactivation has been examined. Some improvements can be achieved by adjusting the operating conditions. Finally, a strategy is proposed for prevention of reduced production due to catalyst deactivation. [source]

Application of Residence Time Distribution for Measuring the Fluid Velocity and Dispersion Coefficient

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 1 2007
W. Zhang
Abstract Most studies on residence time distribution (RTD) have focused on the tail of the RTD curve, and very little attention has been paid to the effect of white noise on the measured results. The aim of this work is to study the effect of white noise on the calculated parameters with different data processing methods. The anti-disturbance abilities of the moment method and the least squares method are compared. The results show that the anti-disturbance ability of the least squares method was better than that of the moment method. As a result of peak overlapping in the RTD curve of a loop reactor, the moment method cannot be used to calculate the fluid velocity and dispersion coefficient. Experiments show that the least squares method is still applicable in a loop reactor. [source]