(149a) Optimal Synthesis of Integrated Reactive Distillation Systems for Fischer-Tropsch Process

Fischer-Tropsch synthesis (FTS) is an area that is receiving revived interest as a technology alternative to produce transportation fuels as well as chemicals from syngas.

Reactive distillation (RD) combines separation and reaction in a single unit, which is ideal for process intensification systems. As heat removal is an essential task for FT reactors, this paper aims to prove that RD can be an advantageous candidate in driving separation of products from the exothermic reaction process, as well as improving selectivity and enhance product yields.

A steady-state adiabatic reactive distillation model is proposed for the FTS. The calculation of the vapor-liquid equilibrium (VLE) through cubic equation of state is used to describe the phase behavior. Rate expressions for the FT and the water gas shift reactions are taken from literature and expressed in terms of fugacities. Product selectivity of catalysts are implemented based on Anderson-Schulz-Flory (ASF) distribution and experimental data. The mass, equilibrium, heat and summation (MESH) model, which is extended by considering bypass streams for non-reactive trays, is used to integrate column structure blocks. A step-by-step initialization procedure is proposed to accommodate for the complexity of the RD column and the high nonlinearity of the model.

Studies of operating variables are conducted to enlighten optimization over performance of the RD model. A typical low-temperature Fischer-Tropsch (LTFT) process which favors diesel production is implemented in the RD model. Results obtained using the RD for FTS are compared against conventional CSTR models, the results showed that RD would have a potential edge in industrial processes.

Keywords: Fischer-Tropsch Synthesis, Reactive Distillation, Vapor–Liquid Equilibrium, Kinetic Modeling, Initialization Procedures.