Catalyst-scale modeling and simulation of a fixed-bed reactor for Fischer-Tropsch synthesis.

摘要

In this work, a wall-cooled fixed-bed reactor was simulated using a 1-D heterogeneous model for Fischer-Tropsch synthesis based on a Fe-based microkinetic model. As a first step, 1-D and 2-D particle models for different catalyst shapes (sphere, solid cylinder, hollow cylinder, 4-hole cylinder, modified 4-hole cylinder and 7-hole cylinder) were simulated to compare the particle-level performance for the Fischer-Tropsch Synthesis (FTS). A Fe-based micro-kinetic olefin re-adsorption model developed by Wang et al. (2008) was coupled with the Soave-Redlich-Kwong (SRK) equation of state to describe the particle-scale transport-kinetic interactions and phase behavior for the gas-phase FTS. The intra-particle effectiveness factor, liquid-to-vapor ratio, CO conversion and intra-particle volume-averaged concentration of diesel were analyzed at different process conditions to compare the performance of different catalyst particle shapes. The wall-cooled fixed-bed reactor with cylindrical pellets was modeled by using the experimental conditions of Jess et al. (2009). The axial temperature profiles showed hot spots at the entrance of the reactor, and the hot spot temperature increased with increase in reactor operating pressure. It has been established through this work that microkinetic rate equations, when coupled with intraparticle transport effects and vapor-liquid equilibrium phenomena, capture the transport-kinetic interactions and phase behavior for gas-phase FT catalysts.