(21c) Development of a Multi-Scale Modeling Approach for Fixed-Bed Fischer Tropsch Reactor: Modeling and Experimental Verification

Development of a Multi-scale Modeling Approach for Fixed-Bed Fischer Tropsch Reactor: Modeling and Experimental Verification

Rehan Hussain, and Nimir O. Elbashir*

Chemical Engineering Program, Texas A&M University at Qatar, PO Box 23874, Doha, Qatar

*Corresponding author. E-mail: nelbashir@tamu.edu

Despite the long history of Fischer Tropsch Synthesis (FTS), there remained comparatively few studies done on modeling the conventional gas-phase FTS fixed-bed reactor until recent years, wherein several significant modeling studies appeared in the literature (e.g. [1-6]]). In many of these studies, the ‘psuedo-homogeneous’ approach, whereby the catalyst, reactants and products are treated as a single phase in the conservation equations, remains the preferred means for modeling fixed-bed FTS reactors. The formation of liquid wax in the FTS reactor may lead to ‘trickle-bed’ behavior whereby a co-current flow of both gas and liquid phases is present. Modeling of trickle-bed reactors usually involves the use of continuous gas- and liquid-phase expressions assuming axial dispersive mixing of heat and mass, with pressure drop, local inter-phase contacting efficiencies and liquid holdups estimated using semi-empirical correlations (e.g. [7]). To-date, multiple research groups have extended this approach to describing fixed-bed FTS reactors operating under trickle-flow conditions (e.g. [1]). In the current study, we aim to model the fixed-bed FTS reactor using a multi-scale approach whereby we combine the use of a detailed mechanistic kinetic model with a particle diffusion model to account for heat and mass transfer limitations both locally and in the whole reactor bed. We developed an experimental campaign to validate the model under typical gas-phase FTS conditions using experimental data generated from our high-pressure FTS reactor unit. This work represents a first step towards developing a comprehensive model for FTS capable of accounting for the presence of different reaction media such as supercritical fluid (SCF) solvents, which have been shown to provide several advantages over operation in the conventional gas-phase FTS [8].

Acknowledgements

The authors are grateful to Dr. Dragomir Bukur for providing the 15 wt% Co/Al₂O₃ catalyst used in experiments and for Dr. Jan Blank for the support in the experimental campaign. This paper was made possible by a NPRP award [NPRP 4-1484-2-590] from the Qatar National Research Fund (a member of the Qatar Foundation). The statements made herein are solely the responsibility of the authors.

References:

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