Computational Investigation of Gas-Solid Flow and Cracking Reaction of Fischer-Tropsch Wax in an Industrial Scale Riser

Thisstudy presents a computational investigation ofthe gas-solidflow and cracking reaction of Fischer-Tropsch wax in an industrial-scaleriser reactor. Based on the two-fluid model together with the lumpingkinetic model of wax cracking, a gas-solid flow, heat transfer,and reaction model is built. CFD simulations are carried out, andthe impacts of the process parameters are evaluated. The results indicatethat velocity, temperature, and species concentration exhibit considerablenonuniformity in the Fischer-Tropsch wax riser. Primary crackingand secondary reactions mainly occur in the lower zone of the riser.Owing to its high reaction activity, the Fischer-Tropsch waxexhibits a high conversion of above 99.0%. The yields of gasolineand liquefied petroleum gas (LPG) reach up to 54.97 and 40.68 wt% at the reaction temperature of 683.15 K, the ratio of catalyst tooil of 4.0, and the reaction time of 1.65 s. Low reaction temperatureand short reaction time favor more gasoline, although the olefin contentin gasoline is high. Considering the liquid yield and olefin reduction,a moderate catalyst-to-oil ratio might be appropriate for Fischer-Tropschwax cracking.