MULTIPLE STEADY STATES IN NON-ISOTHERMAL FT SLURRY REACTOR

Abstract

A model for a non-isothermal, semi-balch (stagnant slurry and flowing gas), laboratory scale Fischer-Tropsch (FT) slurry reactor is developed. The model assumes the existence of FT and water-gas shift (WGS) reactions. The reactor configuration is assumed to be the same as one used by Bhattacharjee et at. (1986). Gas-slurry mass transfer coefficients, solubility parameters and other physical transport and kinetic parameters used in the model are obtained from the reported studies of Lieb and Kuo (1984), Bhattacharjee et al. (1986), Deckwer et al. (1982, 1986) and Karandikar et al. (1987( for the FT slurry system The model is used to evaluate the relevant kinetic constants and the heat generation parameters for the FT reaction from the experimental data of Bhattacharjee et al. (1986). The nature of the heat generation curves indicates that multiple steady states are likely to occur in a non-isothermal FT slurry reactor. The ignition temperatures are calculated as functions of gas hourly space velocity, activation energy for the FT reaction, reactor pressure, and coolant temperature and flow rate. In general, these temperatures are in good agreement with those reported by Bhattacharjee et al. (1986). The exact values of the ignition temperature are strongly affected by the magnitudes of the activation energy and the heat of FT reaction. Once the reactor is ignited, the catalyst changes its character leading to the multiple branches of heat generation and product distribution curves. The extinction temperature was, therefore, not observed in Bhattacharjee's experiments.