Wall heat transfer to chemical reactors

Chao, Raúl E.; Cabán, Reinaldo; Irizarry, M. M.

doi:10.1002/cjce.5450510111

Cited by 19 publications

(5 citation statements)

References 18 publications

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“…Hofmann and Chao found that under reaction conditions k bed /k g is smaller than without reaction [34,35]. Apparently, there is an interaction between this static thermal conductivity and the kinetics [36].…”

Section: Ft Fixed-bed Reactor Model (Multitubular Reactor)mentioning

confidence: 99%

Influence of Particle Size and Single‐Tube Diameter on Thermal Behavior of Fischer‐Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa

Jess

Kern

2011

Chem Eng & Technol

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Simulation of a single tube of a wall-cooled multitubular Fischer-Tropsch (FT) reactor with a cobalt catalyst indicates that the reactor performance is improved by enlarging the catalyst particle diameter. This aspect is studied for variation of the particle size for a fixed tube diameter and vice versa. For a syngas conversion per pass of about 30 % as target and a typical industrially used single-tube diameter of 40 mm, a particle size of > 3 mm is appropriate with regard to a high production rate of higher hydrocarbons. For a particle diameter of < 3 mm, a temperature runaway can only be avoided by rather low cooling temperatures, and the target conversion cannot be reached. In addition, the pressure drop then gets rather high. The reasons for this behavior are: (i) the heat transfer to the cooled tube wall for a given tube size is considerably enhanced by increasing the particle size; (ii) the influence of pore diffusion on the effective rate gets stronger with rising particle size which decreases the danger of temperature runaway.

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Section: Ft Fixed-bed Reactor Model (Multitubular Reactor)mentioning

confidence: 99%

Influence of Particle Size and Single‐Tube Diameter on Thermal Behavior of Fischer‐Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa

Jess

Kern

2011

Chem Eng & Technol

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“…This formulation is called the lumped parameter model in the chemical engineering literature. It has been found that these lumped parameter models often overpredict the temperature of hot spots in the reactors [37,38], which implies that the models underestimate the heat transfer rate at the wall. Some investigators [42][43][44][45][46] have attributed the disparity of the theoretical and experimental results in a wall-cooled catalytic reactor to the assumption of a flat velocity profde (Plug flow) in the lumped parameter model, which does not take into consideration the nonuniform velocity distribution near the wall due to the channeling effects.…”

Section: 2mentioning

confidence: 99%

“…A rational design of this type of reactor is essential in order to avoid disastrous runaway temperature, low conversion rate and catalyst damages [37,38].…”

mentioning

confidence: 99%

Forced Convection in Packed Tubes and Channels with Variable Porosity and Thermal Dispersion Effects

Cheng

Chowdhury

Hsu³

1991

Convective Heat and Mass Transfer in Porous Media

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ABSTRACT. Previous work in chemical engineering literature on the determination of the effective transverse thermal conductivity and Nusselt number for forced convection in packed tubes and channels are reviewed. Discrepancies in existing Nusselt number correlation equations are discussed. Some of the existing experimental data are reanalyzed based on the recent thermal dispersion theory developed by Hsu and Cheng with variable porosity effects Iaken into considmltion in an approximate manner. Numerical results are obtained for forced convection of air and water in packed tubes and channels. For forced convection in a packed column, it is found that the avemge Nusselt number depends not only on the Reynolds number, but also on the dimensionless particle diameter, the dimensionless length of the tube, the thermal conductivity ratio of the fluid phase to the solid phase, and the Prandd number of the fluid. IN1RODUcnONForced convection in packed tubes and channels have been the subject of intensive study in chemical engineering literature during the past six decades [I]. As early u 1931, Colbmn [2] found that the heat transfer rate for forced convection of air through a packed tube is about eight times higher than that of an empty tube. The substantial increase in the heat transfer rate hu been attributed to the mixing of fluid owing to the presence of the solid matrix known u the thermal dispersion process. During the ensuring years, more than thirty experiments have been performed on forced convection through cylindrical , annular [33][34][35]

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“…The heat removal from the reactor had to be increased in the model for fast reaction or high temperature conditions. This interaction between heat transfer and reaction rate is not unusual and has been seen by other workers (Paterson and Carberry, 1983;Hofmann, 1979;Panthel, 1977;Hlavacek and Votruba, 1977;Chao, et al, 1973). Therefore, estimation of both heat transfer parameters and kinetic parameters are necessary under reactive conditions.…”

Section: Experiments Without Reactionmentioning

confidence: 78%

Steady State and Dynamic Modelling of a Packed Bed Reactor for the Partial Oxidation of Methanol to Formaldehyde Ii. Experimental Results Compared With Model Predictions

Schwedock

Windes

Ray

1989

Chemical Engineering Communications

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Heterogeneous and pseudohomogeneous two-dimensional models are compared to steady state and dynamic experimental data from a packed bed reactor for the partial oxidation of methanol to formaldehyde over an iron oxide-molybdenum oxide catalyst. Highly effective parameter estimation software was used to fit selected model parameters to large sets of experimental data so as to obtain small residuals. Heat transfer parameters which were successful in matching data from experiments without reaction were not capable of fitting data from experiments with reaction, and it was necessary to increase the radial heat transfer for higher temperatures or reaction rates. Axial composition profile data was represented by estimating the preexponential factors and activation energy in a half-order redox rate expression for methanol oxidation. After some decline in catalyst activity, a time-varying axial catalyst activity profile was determined from the data. A redox-type rate expression for the oxidation of formaldehyde to carbon monoxide was proposed to fit the data. The dynamics of the reactor temperature profile were accurately represented by the model. The heterogeneous and pseudohomogeneous models gave similar results in fitting experimental data, although the parameters determined for the two models were somewhat different.

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Wall heat transfer to chemical reactors

Cited by 19 publications

References 18 publications

Influence of Particle Size and Single‐Tube Diameter on Thermal Behavior of Fischer‐Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa

Influence of Particle Size and Single‐Tube Diameter on Thermal Behavior of Fischer‐Tropsch Reactors. Part I. Particle Size Variation for Constant Tube Size and Vice Versa

Forced Convection in Packed Tubes and Channels with Variable Porosity and Thermal Dispersion Effects

Steady State and Dynamic Modelling of a Packed Bed Reactor for the Partial Oxidation of Methanol to Formaldehyde Ii. Experimental Results Compared With Model Predictions

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