Multiple Steady States in Non-Isothermal Ft Slurry Reactor

Abstract

A model for a non-isothermal, semi-batch (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 0/. (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 0/. (1986), Deckwer et 0/. (1982, 1986) and Karandikar eI al. (1987) for the IT slurry system. The model is used to evaluate the relevant kinetic constants and the heat generation parameters forthe IT reaction from the experimental data of Bhattacharjee er 0/. (1986). The nature of the heat generation curves indicates that multiple steady states are likely to occur in a non-isothermal IT slurry reactor. The ignition temperatures are calculated as functions of gas hourly space velocity, activation energy for the Ff reaction, reactor pressure, and coolant temperature and flow rate. In general, these temperatures are in good agreement with those reported by Bhattacharjee er at. (1986). The exact values of the ignition temperature are strongly affected by the magnitudes of the activation energy and the heat of IT 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.

Power to Fuels: Dynamic Modeling of a Slurry Bubble Column Reactor in Lab-Scale for Fischer Tropsch Synthesis under Variable Load of Synthesis Gas

“…In the above equations, A i denotes the Henry's constant (H i ) for syngas and light hydrocarbons (CO, H 2 , H 2 O, C 1 and C 2 ). By employing Henry's law solubility factor (P i = x i × H ∞ i ), the Henry's constant for each reactant gas was calculated based on the heat of solution for each component and operating temperature [25].…”

“…where, the value of parameters H * i and ∆H s,i are listed in reference [25]. For heavier components (C + 4 ), Ai was calculated using Raoult's law for gas-liquid phase at the equilibrium as follows:…”

Diagnostic nonlinear analysis of Fischer‐Tropsch synthesis in stirred‐tank slurry reactors

“…Shah et al 1990 have previously made an attempt to address multiplicity behavior of FT reactors. Rather than base such an investigation on the methods of nonlinear analysis, they limited themselves to interpretations based entirely on the heat generation and dissipation curves identified from the Ž .…”

“…For a complete elucidation of the multiplicity and stability features of the multidimensional FT reaction system, the thermal analy-Ž . sis of Shah et al 1990 does not constitute an alternative to the application of rigorous bifurcation theory.…”

“…This issue has been theoretically Ž . treated by Shah et al 1990 based on the experimental ob-Ž . servation by Bhattacharjee et al 1986 , where the critical conditions for ignition and extinction are provided in terms of the various process parameters, such as CO feed concentration, gas space velocity, and activation energy.…”