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

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Jess, Andreas ; Kern, Christoph:
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.
In: Chemical Engineering & Technology. Bd. 35 (2012) Heft 2 . - S. 369-378.
ISSN 1521-4125
DOI: https://doi.org/10.1002/ceat.201100615

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Abstract

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.