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Tubular Reactors (tubular + reactor)

Distribution by Scientific Domains

Chemistry	44%
Polymers and Materials Science	41%
Engineering	10%

Selected Abstracts

Nitroxide-Mediated Bulk and Miniemulsion Polymerization in a Continuous Tubular Reactor: Synthesis of Homo-, Di- and Triblock Copolymers

MACROMOLECULAR REACTION ENGINEERING, Issue 3-4 2010
Thomas E. Enright
Abstract In previous work, a modified nitroxide-mediated miniemulsion polymerization was demonstrated in a continuous tubular reactor to prepare a latex of polystyrene homopolymer dispersed in water. There, the initial reaction step (low conversion bulk polymerization to prepare the macroinitiator) was done in a batch reactor while the miniemulsion polymerization step was done in a continuous tubular reactor. The present paper describes an extension of that work in which all the reaction steps have been achieved in the continuous tubular reactor. Chain extension of the polystyrene latex to give polystyrene- block -poly(butyl acrylate) diblock and polystyrene- block -poly(butyl acrylate)- block -polystyrene triblock copolymers is also described. [source]

High-Pressure Polymerization of Ethylene in Tubular Reactors: A Rigorous Dynamic Model Able to Predict the Full Molecular Weight Distribution

MACROMOLECULAR REACTION ENGINEERING, Issue 7 2009
Mariano Asteasuain
Abstract A rigorous dynamic model of the high-pressure polymerization of ethylene in tubular reactors is presented. The model is capable of predicting the full molecular weight distribution (MWD), average branching indexes, monomer conversion and average molecular weights as function of time and reactor length. The probability generating function method is applied to model the MWD. This technique allows easy and efficient calculation of the MWD, in spite of the complex mathematical description of the process. The reactor model is used to analyze the dynamic responses of MWD and other process variables under different transition policies, as well as to predict the effects of process perturbations. The influence of the material recycle on the process dynamics is also shown. [source]

"Living" Radical Polymerization in Tubular Reactors, 2 , Process Optimization for Tailor-Made Molecular Weight Distributions

MACROMOLECULAR REACTION ENGINEERING, Issue 5 2008
Mariano Asteasuain
Abstract "Living" radical polymerization is a relatively new polymerization process that can be used to prepare resins with controlled structures. In this work, a mathematical model developed previously to describe nitroxide-mediated "living" radical polymerizations performed in tubular reactors is used for the optimization of the process and obtainment of tailor-made MWDs. Operating conditions and design variables are determined with the help of optimization procedures in order to produce polymers with specified MWDs. It is shown that bimodal and trimodal MWDs, with given peak locations, can be obtained through proper manipulation of the operating conditions. This indicates that the technique discussed in this work is suitable for detailed design of the MWD of the final polymer. [source]

"Living" Free Radical Polymerization in Tubular Reactors.

MACROMOLECULAR REACTION ENGINEERING, Issue 6 2007

Abstract This is the first of a series of works aiming at developing a tool for designing "living" free radical polymerization processes in tubular reactors, in order to achieve tailor-made MWDs. A mathematical model of the nitroxide-mediated controlled free radical polymerization is built and implemented to predict the complete MWD. It is shown that this objective may be achieved accurately and efficiently by means of the probability generating function (pgf) transformation. Comparison with experimental data is good. The potential of the resulting model for optimization activities involving the complete MWD is also shown. [source]

Particles from fires,a screening of common materials found in buildings

FIRE AND MATERIALS, Issue 6 2003
Tommy Hertzberg
Abstract Small combustion generated particles are known to have a negative impact on human health and on the environment. In spite of the huge amount of particles generated locally in a fire accident, few investigations have been made on the particles from such fires. In this article, 24 different materials or products, typically found in buildings have been exposed to burning conditions in order to examine their particle generating capacity. In addition, a carbon fibre based composite material was tested in order to investigate if asbestos-resembling particles could be generated in a fire situation. The majority of the experiments were performed in the small-scale cone calorimeter, and some further data were collected in intermediate scale (SBI) and full scale (room-corner) tests. Additional testing of the composite material was made in a small-scale tubular reactor. The amount of particles and particle size distributions were measured by the use of a low-pressure impactor and particle aerodynamic diameter sizes from 30 nm to 10 ,m were measured. The results from the project show that the yield of particles generated varied significantly between materials but that the shape of mass and number size distributions were very similar for all the materials tested. The maximum amount of particles was obtained from materials that did not burn well (e.g. flame retarded materials). Well-burning materials, e.g. wood materials, tend to oxidize all available substances and thereby minimize the amount of particles in the smoke gas. It was found that asbestos-resembling particles could be produced from under-ventilated combustion of the composite material tested. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Fluid dynamic numerical simulation coupled with heat transfer and reaction in the tubular reactor of industrial cracking furnaces

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 4 2010
Chufu Li
Abstract The thermal cracking furnace is the heart of the ethylene production process in a petrochemical plant. This paper presents a comprehensive mathematical model containing equations for mass, momentum and heat transfer combined with Kumar molecular kinetic model to describe dynamic behaviors of fluid flow, heat transfer and reaction in the tubular reactor of thermal cracking furnaces. The ,flow-reaction' decomposition strategy is adopted to solve the complex model for implementing the fluid dynamic simulation coupled with heat transfer and reaction in the tubular reactor by a conventional procedure. The proposed mathematical model and the decomposition algorithm are successfully applied to the fluid dynamic simulation in the tubular reactor of a millisecond industrial cracking furnace. The results of dynamic simulation reveal the various transient behaviors of fluid flow, temperature change and species content variation in the tubular reactor under the step disturbance of inlet feedrate. Finally, the performance of the decomposition algorithm is also investigated. Copyright © 2009 John Wiley & Sons, Ltd. [source]

Thermal and mass transients in the developing region of a homogeneous tubular chemical reactor

AICHE JOURNAL, Issue 3 2010
Mohammad K. Alkam
Abstract The current investigation presents a finite difference simulation of a homogeneous tubular reactor under laminar flow conditions. The present simulation considers the unsteady operation where transients in flow hydrodynamics, temperature field, and species concentrations have been considered. Flow development in the entrance region of the present reactor has been considered. Present results exhibit reactant concentration and mixing cup temperature profiles for a variety of operating conditions. Effects of several parameters on the performance of the current reactor have been examined, including, reaction parameter, order of reaction, and Schmidt number. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

Nonstationary model of the semicontinuous depolymerization of polycarbonate

AICHE JOURNAL, Issue 12 2006
Raúl Piñero-Hernanz
Abstract The experimental work for the depolymerization process of Bisphenol A polycarbonate pellets and CD/DVD wastes in a semicontinuous reactor and a novel nonstationary model to describe the process is presented. The different steps of the process to develop the model are analyzed thoroughly. The kinetics of the alkali-catalyzed methanolysis of polycarbonate was determined. The reactor and kinetic models were validated by a series of 21 experiments performed in a laboratory semicontinuous tubular reactor at isothermal conditions from 90 to 180°C and pressures from 1.0 to 20.0 MPa in liquid phase, with and without NaOH concentrations of 1 × 10,3 to 5 × 10,3 kg/L, flow rates from 2.3 × 10,3 to 10.2 × 10,3 L/min, and CO2 molar fractions from zero to 0.374. The effects of temperature, pressure, catalyst amount, mass transfer (solvent flow rate), and CO2 addition in kinetics were investigated. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

Decomposition of monochlorobiphenyl isomers in supercritical water in the presence of methanol

AICHE JOURNAL, Issue 7 2004
Gheorghe Anitescu
Abstract Comprehensive studies of monochlorobiphenyl (MCB) decomposition in supercritical water in the presence of methanol and other cosolvents, both with and without oxygen, are being conducted to understand the reaction kinetics and pathways of individual PCB isomers and to determine the structure,reactivity relationships. In the present study the disappearance rate of MCBs, delivered in an isothermal plug-flow tubular reactor as methanolic solutions, is investigated at 25 MPa and temperatures of 673, 723, and 773 K. Experiments are conducted at nominal MCB feed concentrations of 1,100 ,mol/L (reaction conditions) using MCB/MeOH and H2O2/H2O solutions (1,3 g/L and 0,10 wt. %, respectively). Molar conversions of these isomers vary from 3% (2-CB, 773 K, 2 s) to 30% (4-CB, 773 K, 46 s) without oxygen (SCWT) and from 1% (2-CB, 673 K, 3.8 s) to 97% (4-CB, 773 K, 24.5 s) with oxygen (SCWO). For SCWT the overall conversion follows apparent first order, whereas for SCWO the conversion is second order. The regressed data lead to Arrhenius parameters of frequency factor and activation energy with values of 1020.5,1021.3 s,1 and 320,331 kJ/mol for SCWT and 1024.1,1024.8 s,1 (mol/L),1 and 281,292 kJ/mol for SCWO, respectively. The reactivity of the MCB isomers increases in the order 2-MCB < 3-MCB < 4-MCB. The positively identified reaction products by GC-MSD and GC-FID/ECD/TCD analyses are mainly biphenyl, open-ring biphenyl compounds such as acetophenone and benzaldehydes, and mineral products (CO, CO2, and HCl). More studies are in progress regarding the role of the second solvent on reaction rates and reaction mechanisms and pathways. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1536,1544, 2004 [source]

Nitroxide-Mediated Bulk and Miniemulsion Polymerization in a Continuous Tubular Reactor: Synthesis of Homo-, Di- and Triblock Copolymers

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

MACROMOLECULAR SYMPOSIA, Issue 1 2009
Yefim Brun
Abstract Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene,vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene,methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers. [source]

Simulation of fine particle formation by precipitation using computational fluid dynamics

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 5 2000
Damien Piton
Abstract The 4-environment generalized micromixing (4-EGM) model is applied to describe turbulent mixing and precipitation of barium sulfate in a tubular reactor. The model is implemented in the commercial computational fluid dynamics (CFD) software Fluent. The CFD code is first used to solve for the hydrodynamic fields (velocity, turbulence kinetic energy, turbulent energy dissipation). The species concentrations and moments of the crystal size distribution (CSD) are then computed using user-defined transport equations. CFD simulations are performed for the tubular reactor used in an earlier experimental study of barium sulfate precipitation. The 4-EGM CFD results are shown to compare favourably to CFD results found using the presumed beta PDF model. The latter has previously been shown to yield good agreement with experimental data for the mean crystal size at the outlet of the tubular reactor. On a appliqué un modéle de micromélange généralisé à 4 environnements (4-EGM) afin de décrire le mélange turbulent et la précipitation du sulfate de baryum dans un réacteur tubulaire. Ce modéle a été implanté dans le logiciel de CFD commercial Fluent. Le programme de CFD est d'abord utilisé pour calculer les champs hydrodynamiques (vitesse, énergie cinétique de turbulence, dissipation d'énergie turbulente). Les concentrations d'espéces et les moments de la distribution de taille des cristaux (CSD) sont ensuite calculés par ordinateur à l'aide des équations de transport définies par l'usager. Des simulations de CFD sont réalisées pour le réacteur tubulaire utilisé dans une étude expérimentale antérieure de la précipitation du sulfate de baryum. On montre que les prédictions du 4-EGM se comparent favorablement à celles du modéle béta PDF. II a été montré antérieurement que ce dernier présentait un bon accord avec les donnés expérimentales pour la taille moyenne des cristaux à la sortie du récteur tubulaire. [source]

Optimal operation of tubular reactors for naphtha cracking by numerical simulation

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009
G.-Y. Gao
Abstract Process gas temperature profile and steam-to-hydrocarbon ratio in the feed have important impact on product yields and coking rate in tubular reactors for naphtha cracking. This study is to evaluate these effects quantitatively based on numerical simulation. Steady-state operation of the tubular reactor in an industrial thermal cracking furnace was first simulated in HYSYS with a molecular reaction scheme. Various case studies then investigate the influence of process gas temperature profile and inlet steam-to-hydrocarbon ratio so that the ethylene/propylene product yields and coking rate can be evaluated. Finally, steady-state optimization was applied to the operation of this industrial furnace. The optimal process temperature profile and the optimal inlet steam-to-naphtha ratio were found to maximize the operation profit. This study will provide significant guidance to process engineers in the ethylene industry. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

Concept, Design and Manufacture of a Prototype Hydrogen Storage Tank Based on Sodium Alanate

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 8 2009
C. Na Ranong
Abstract In the framework of the EC project STORHY (Hydrogen Storage for Automotive Applications), the prototype of a solid storage tank for hydrogen based on sodium alanate was developed. A storage tank containing 8,kg sodium alanate was designed and manufactured with the objective of fast refueling. To obtain the optimum design of the storage tank a simulation tool was developed and validated by experiments with a laboratory-scale tubular reactor. Application of the simulation tool to different storage concepts and geometries yielded the final design. The chosen concept is modular, enabling simple scale-up. This is the basis for the future development of fuel cell vehicle storage tanks containing 5,kg of hydrogen. [source]

A Novel Radial-Flow, Spherical-Bed Reactor Concept for Methanol Synthesis in the Presence of Catalyst Deactivation

CHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 11 2008
R. Rahimpour
Abstract A radial-flow, spherical-bed reactor concept for methanol synthesis in the presence of catalyst deactivation, has been proposed. This reactor configuration visualizes the concentration and temperature distribution inside a radial-flow packed bed with a novel design for improving reactor performance with lower pressure drop. The dynamic simulation of spherical multi-stage reactors has been studied in the presence of long-term catalyst deactivation. Model equations were solved by the orthogonal collocation method. The performance of the spherical multi-stage reactors was compared with a conventional single-type tubular reactor. The results show that for this case study and with similar reactor specifications and operating conditions, the two-stage spherical reactor is better than other alternatives such as single-stage spherical, three-stage spherical and conventional tubular reactors. By increasing the number of stages of a spherical reactor, one increases the quality of production and decreases the quantity of production. [source]

Experimental study of reactive chaotic flows in tubular reactors

AICHE JOURNAL, Issue 8 2005
C. Boesinger
For many reactive processes, fluid mixing has a significant effect on the rate of a chemical reaction and on the quality of the product. Mixing in a chaotic flow reactor is a promising phenomenon to control and optimize chemical processes. The effect of three-dimensional (3-D) chaotic flow advection on mixing efficiency and on chemical reaction advancement is examined. An experimental comparison is made, for low Reynolds number flows, between two tubular reactors made of successive bends, with the same number of bends (equal to 80) mounted in different configurations : a helical configuration (for regular flow) and a chaotic flow configuration with bends in perpendicular planes. We show that the mixing and the chemical reaction (for an instantaneous bimolecular chemical reaction) are more efficient in the chaotic flow reactor than in the helical reactor. The different effects of chaotic advection, molecular diffusion and reaction are discussed in view of laboratory findings. © 2005 American Institute of Chemical Engineers AIChE J, 2005 [source]

PDF simulations of ethylene decomposition in tubular LDPE reactors

AICHE JOURNAL, Issue 2 2005
Nitin H. Kolhapure
Abstract The present study deals with turbulent reacting flow simulation inside low-density polyethylene (LDPE) tubular reactors, based on a detailed computational fluid dynamics (CFD) technique,transported probability density function (PDF) methods. The ability of the PDF methods to provide an exact representation of chemical source terms is ideally suited for coupling complex LDPE chemistry with small-scale fluid dynamic fluctuations in turbulent flow. LDPE chemistry with a total of 16 scalars provides an ideal test case for illustrating the applicability of an efficient chemistry algorithm based on in-situ adaptive tabulation. A particle-based Monte Carlo algorithm is used to solve the joint-composition PDF equation, whereas a finite-volume code is used to obtain hydrodynamic fields from the standard k,, turbulence model. The influence of feed temperature, initiator concentration, and degree of premixing is investigated to gain detailed knowledge of micromixing effects on steady-state reactor performance. The computational approach provides a low-cost alternative to experimental and pilot-plant tests for exploring a variety of design options when making important design and operational decisions, or for investigating unstable reactor operating conditions. The ability of a simplified, but otherwise equivalent multi-environment-presumed PDF model to predict turbulence,chemistry interactions close to physical reality is validated using the detailed transported PDF simulations. The transported PDF method is shown to be an excellent tool for obtaining fundamental information on turbulent reacting flows, as well as for deriving simplified models for faster and easier interpretation of these flows when developing safe and efficient chemical processes. © 2005 American Institute of Chemical Engineers AIChE J, 51: 585,606, 2005 [source]

High-Pressure Polymerization of Ethylene in Tubular Reactors: A Rigorous Dynamic Model Able to Predict the Full Molecular Weight Distribution

"Living" Radical Polymerization in Tubular Reactors, 2 , Process Optimization for Tailor-Made Molecular Weight Distributions

"Living" Free Radical Polymerization in Tubular Reactors.

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

A stochastic flow model for a tubular solution polymerization reactor

POLYMER ENGINEERING & SCIENCE, Issue 11 2007
Ardson dos S. Vianna Jr.
Residence time distributions were evaluated experimentally for three tubular solution polymerization reactors to analyze aspects of the fluid-dynamic behavior of these reactors. The analysis of the available experimental data indicates that the flow characteristics of these reactors may be subject to stochastic perturbations. A stochastic flow model is then proposed by assuming that a viscous polymer layer is formed in the proximities of the reactor walls and that plugs of polymer material are released at random during the operations. This model is able to represent the available experimental data fairly well for three tubular reactors with different configurations. POLYM. ENG. SCI., 47:1839,1846, 2007. © 2007 Society of Plastics Engineers [source]

Industrial high pressure ethylene polymerization initiated by peroxide mixtures: A reduced mathematical model for parameter adjustment

POLYMER ENGINEERING & SCIENCE, Issue 5 2001
M. Asteasuain
We present a method for the adjustment of parameters in the mathematical modeling of industrial tubular reactors for high pressure polymerization of ethylene. We propose a reduced mathematical model for these reactors that aids in the task of model parameter update commonly done periodically in industrial plants. This reduced model was built from a detailed model for multiple peroxide and oxygen initiator systems we had developed before. Some of the assumptions in that rigorous model were reviewed in order to minimize computational effort. Good and faster predictions were obtained by assuming different constant jacket temperatures and pressures at each zone. Pressure pulse equations had to be included in the model. A simplification of the adjustment procedure is also proposed here. It consists in using only the reactions considered crucial for the description of this polymerization. The peroxide initiator and solvent mixtures were treated as fictitious unique initiator and solvent respectively. A procedure was established for the quick estimation of the kinetic parameters that represent initiator and solvent mixtures of different compositions. This resulted in a model that can be adjusted rapidly to predict the behavior of a specific industrial reactor. The reduced model was validated using experimental runs initiated by oxygen either alone or together with peroxide mixtures. [source]

Optimal operation of tubular reactors for naphtha cracking by numerical simulation

Effect of Elicitation on Growth, Respiration, and Nutrient Uptake of Root and Cell Suspension Cultures of Hyoscyamusmuticus

BIOTECHNOLOGY PROGRESS, Issue 2 2002
Edgard B. Carvalho
The elicitation of Hyoscyamus muticus root and cell suspension cultures by fungal elicitor from Rhizoctonia solani causes dramatic changes in respiration, nutrient yields, and growth. Cells and mature root tissues have similar specific oxygen uptake rates (SOUR) before and after the onset of the elicitation process. Cell suspension SOUR were 11 and 18 ,mol O2/g FW·h for non-elicited control and elicited cultures, respectively. Mature root SOUR were 11 and 24 ,mol O2/g FW·h for control and elicited tissue, respectively. Tissue growth is significantly reduced upon the addition of elicitor to these cultures. Inorganic yield remains fairly constant, whereas yield on sugar is reduced from 0.532 to 0.352 g dry biomass per g sugar for roots and 0.614 to 0.440 g dry biomass per g sugar for cells. This reduction in yield results from increased energy requirements for the defense response. Growth reduction is reflected in a reduction in root meristem (tip) SOUR, which decreased from 189 to 70 ,mol O2/g FW·h upon elicitation. Therefore, despite the increase in total respiration, the maximum local oxygen fluxes are reduced as a result of the reduction in metabolic activity at the meristem. This distribution of oxygen uptake throughout the mature tissue could reduce mass transfer requirements during elicited production. However, this was not found to be the case for sesquiterpene elicitation, where production of lubimin and solavetivone were found to increase linearly up to oxygen partial pressures of 40% O2 in air. SOUR is shown to similarly increase in both bubble column and tubular reactors despite severe mass transfer limitations, suggesting the possibility of metabolically induced increases in tissue convective transport during elicitation. [source]