On the effect of vapor-liquid equilibria during Fischer-Tropsch synthesis modelling

FERNANDA NEIRA D'ANGELO; ALEJO AGUIRRE

Guilin

Conferencia; 14th International Conference on Gas-Liquid and Gas-Liquid-Solid Reactor Engineering (GLS-14); 2019

Institute of Process Engineering of Chinese Academy of Sciences (CAS)

IntroductionThe Fischer-Tropsch synthesis (FTS) is a process widely applied to convert syngas to liquid fuels and chemicals. The products are mostly paraffins and olefins with a distribution that generally follows the Anderson Schulz Flory (ASF) distribution equation [1].𝑆𝑛𝑛=(1−𝛼)2𝛼𝑛−1(1)However, various research studies demonstrate that the experimentally observed product distribution deviate from the ASF equation, with a break around carbon number of ∼8−11, leading to negative or positive deviations [2,3]. The deviations where attributed to: (i) hot spots in the reactor, (ii) internal mass transfer limitations, (iii) effect of the vapor-liquid equilibria (VLE), among others.Taking into account that the FTS is a highly exothermic reaction that involves three phases, the coupling between chemistry, thermodynamic, hydrodynamics, mass and heat transfer is not straightforward. For a better understanding and optimization of the reactor performance, all these phenomena should be taken into account. Several groups have modelled a fixed-bed FTS reactor using different approaches for validation of experimental data and/or for parametric sensitivity studies. Nevertheless, to the best of our knowledge, a complete mathematical model that considers the position-dependent VLE and the variation of the chain growth probability for a fixed-bed reactor has not been reported yet.In the present work we introduce a complete 1-D reactor model, taking into account the VLE and the deviation of α with the temperature and the H2/CO ratio. The general behavior of the FTS and the influence of the VLE in the product distribution at different process conditions is presented.