(42a) Reactor Design for Supercritical Fischer Tropsch

Authors: 
Durham, E., Auburn University
Eden, M. R., Auburn University
Roberts, C. B., Auburn University


Fischer Tropsch Synthesis (FTS) is a mature process for the production of fuels and chemicals from syngas.  In low temperature mode (LTFT) it is used primarily for the production of diesel fuel and wax.  The FTS reaction is strongly exothermic, and managing this heat is a major factor in LTFT reactor design.  The traditional fixed bed design utilizes a high gas velocity in a high number of narrow tubes.  This reactor suffers from poor economies of scale and high pressure drop.  Fixed bed reactors have been utilized by Sasol and Shell for LTFT.  To address problems associated with fixed-bed LTFT, Sasol developed a slurry reactor.  This reactor offers superior economies of scale, pressure drop, and thermal uniformity, but also increased development cost and the technical challenge of separating produced wax from the catalyst.

 In an attempt to realize the advantages of each reactor design, Kaoru Fujimoto’s research group pioneered the use of a supercritical fluid as the reaction media for LTFT (SC-FTS) in a fixed-bed reactor.  This has been shown to give suppress methane and CO2 formation, to enhance the selectivity of the reaction to potentially valuable primary products, and to improve activity maintenance.  Two issues preventing the industrial utilization of SC-FTS are higher capital cost of the SC-FTS reactor (relative to the Sasol ARGE reactor) due to the higher pressure and higher operating cost due to compression of the media and syngas.

 We will present work that we have done to decrease the capital cost of the SC-FTS reactor to improve its potential for industrial utilization.

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