PDF modeling of turbulent‐mixing effects on initiator efficiency in a tubular LDPE reactor

Tsai, Kuochen; Fox, Rodney O.

doi:10.1002/aic.690421020

Cited by 41 publications

(89 citation statements)

References 37 publications

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“…These tables store the DI results over the entire composition space, and the result of the computation during the simulation is obtained by multilinear interpolation. 6 This method works well for kinetic schemes involving low numbers of species (e.g., less than six). However, for the detailed chemistry scheme with 38 species considered in this work, the storage space required for even reasonable accuracy (around 39 × 100 39 real numbers) is infeasible.…”

Section: Introductionmentioning

confidence: 99%

“…However, faster computers and more efficient algorithms have made such simulations considerably easier. [4][5][6] Although several authors have reported 7 successful CFD simulations of methane chlorination reactors, most studies have been limited to smaller reaction schemes or onedimensional models. In general, previous studies have concluded that, unless a detailed kinetic scheme is employed, CFD does a poor job of predicting finite-rate chemistry effects, minor species formation, and reactor extinction.…”

Section: Introductionmentioning

confidence: 99%

“…The convection and diffusion terms are simulated using a full PDF method, as described in detail elsewhere. 6 The contribution due to the chemical source term results in a set of nonlinear, stiff ordinary differential equations (ODEs) of the form where the chemical source term is given by and R i (O) is the reaction rate corresponding to the ith reaction. The source term for the temperature is derived from an enthalpy balance equation and has the form where h is the specific enthalpy of the th chemical species.…”

Section: Introductionmentioning

confidence: 99%

“…6,8 In a CFD simulation, continuity and momentum transport equations of the form and are solved for the flow field, and a species transport equation of the form is solved for each species in the kinetic scheme. At high Reynolds numbers, a turbulence model is required to represent the flow field.…”

Section: Introductionmentioning

confidence: 99%

“…These fields are required as input to the full PDF code for the simulation of the turbulent transport of the chemical species. 6 In the more general case of a variable-density flow, a hybrid CFD-PDF approach is used where in the mean density field is found from the PDF code. An iteration procedure is then required to find the mean velocity.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

CFD Analysis of Premixed Methane Chlorination Reactors with Detailed Chemistry

Raman¹,

Fox

Harvey

et al. 2001

Ind. Eng. Chem. Res.

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With the implementation of efficient algorithms for the accurate calculation of reaction source terms, computational fluid dynamics (CFD) is now a powerful tool for the simulation and design of chemical reactors with complex kinetic schemes. The example studied in this work is the methane chlorination reaction for which the detailed chemistry scheme has 152 reactions and 38 species. The adiabatic, jet-stirred chlorination reactor used for the CFD simulations is an insulated right cylinder with a coaxial premixed feed stream at one end. In order for this reactor to remain lit, recirculation of hot products is crucial, and hence, reactor stability is sensitive to both macroscale and microscale mixing. By neglecting density variations, a Lagrangian composition probability density function (PDF) code with a novel chemistry tabulation algorithm (in-situ adaptive tabulation or ISAT) for handling complex reactions is used to simulate the species concentrations and temperature field inside of the reactor. In addition, a reduced mechanism with 21 reactions and 15 species is tested for accuracy against the detailed chemistry scheme, a simplified CSTR model is used to illustrate the shortcomings of zero-dimensional models, and a pair-wise mixing stirred reactor (PMSR) model is used to show the stabilizing effect of micromixing on reactor stability. The CFD simulations are generally in good agreement with results from pilot-scale reactors for the outlet temperature and major species. Albert D. Harvey and David H. WestThe Dow Chemical Company, Freeport, With the implementation of efficient algorithms for the accurate calculation of reaction source terms, computational fluid dynamics (CFD) is now a powerful tool for the simulation and design of chemical reactors with complex kinetic schemes. The example studied in this work is the methane chlorination reaction for which the detailed chemistry scheme has 152 reactions and 38 species. The adiabatic, jet-stirred chlorination reactor used for the CFD simulations is an insulated right cylinder with a coaxial premixed feed stream at one end. In order for this reactor to remain lit, recirculation of hot products is crucial, and hence, reactor stability is sensitive to both macroscale and microscale mixing. By neglecting density variations, a Lagrangian composition probability density function (PDF) code with a novel chemistry tabulation algorithm (in-situ adaptive tabulation or ISAT) for handling complex reactions is used to simulate the species concentrations and temperature field inside of the reactor. In addition, a reduced mechanism with 21 reactions and 15 species is tested for accuracy against the detailed chemistry scheme, a simplified CSTR model is used to illustrate the shortcomings of zero-dimensional models, and a pair-wise mixing stirred reactor (PMSR) model is used to show the stabilizing effect of micromixing on reactor stability. The CFD simulations are generally in good agreement with results from pilot-scale reactors for the outlet temperature and major spe...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

CFD Analysis of Premixed Methane Chlorination Reactors with Detailed Chemistry

Raman¹,

Fox

Harvey

et al. 2001

Ind. Eng. Chem. Res.

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Prediction of the Spatial Distribution of the Average Molecular Weights in Living Polymerisation Reactors using CFD Methods

Meszena

Johnson²

2001

Macromol. Theory Simul.

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Polymerisation reactor design and mode of operation are particularly important for polymerisation processes where the lifetime of the growing species is long compared to the mean residence time of reactants in the reactor. For these reasons, reactor control strategies can be devised for living polymerisation processes in order to tailor the nature of the polymer produced, for example, molecular weight distribution. The strategies can only be devised for ideal reaction and reactor behaviour. Since neither are ideal, it is necessary to understand those factors which cause deviation from ideality. In this work, the influence of the spatial distribution of temperature and flow velocity is examined for an ideal classical living polymerisation reaction carried out in a tubular reactor under steady‐state reactor conditions using a computational fluid dynamics (CFD) code (PHOENICS) to explore the influence of the spatial distribution of species and temperature on the product with all other reactor features being ideal. Particular attention is given to the problem of describing the spatial distribution of the dispersity index (moments of the molecular weight distribution) of the polymer in addition to flow velocity, temperature, component concentrations and kinematic viscosity. Comparisons are made between the CFD predictions, simulations based on the ideal behaviour of the process, and the experimental results from a laboratory‐scale reactor. It is shown that the CFD predictions give a more realistic description of the tubular reactor behaviour for the conditions employed. The limitations of the CFD approach and the additional problems still needing to be addressed, such as mixing quality, are discussed.

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Free‐Radical Polymerization: Homogeneous

Hutchinson¹

2005

Handbook of Polymer Reaction Engineering

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Free-radical polymerization (FRP) is one of the most important commercial processes for preparing high molecular weight polymers. It can be applied to almost all vinyl monomers under mild reaction conditions over a wide temperature range and, although requiring the absence of oxygen, is tolerant of water. Multiple monomers can be easily copolymerized via FRP, leading to the preparation of an endless range of copolymers with properties dependent on the proportion of the incorporated comonomers. This chapter will provide an overview of the kinetics and mechanisms, and the techniques used to construct mathematical representations of bulk and solution FRP. The description will also serve as a good base for the suspension and emulsion FRP chapters that follow. FRP Properties and ApplicationsPolymers produced via free-radical chemistry include the following major families:Low-density polyethylene (LDPE) and copolymers, used primarily in films and packaging applications. LDPE has density of <0.94 g cm À3 , and is produced via high-pressure free-radical polymerization; polyethylenes of higher density (and polypropylene) are produced via transition metal catalysis, as described elsewhere (see Chapter 8). Poly(vinyl chloride) and copolymers, used primarily to produce pipe and fittings, flooring material, and films and sheet. Polystyrene and its co-and terpolymers with acrylonitrile and butadiene. Homopolymer is used for packaging and containers, while the acrylonitrile-containing polymers are used for various molded products in the appliance, electronics, and

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PDF modeling of turbulent‐mixing effects on initiator efficiency in a tubular LDPE reactor

Cited by 41 publications

References 37 publications

CFD Analysis of Premixed Methane Chlorination Reactors with Detailed Chemistry

CFD Analysis of Premixed Methane Chlorination Reactors with Detailed Chemistry

Prediction of the Spatial Distribution of the Average Molecular Weights in Living Polymerisation Reactors using CFD Methods

Free‐Radical Polymerization: Homogeneous

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