One-dimensional heterogeneous model of a Fischer-Tropsch synthesis reactor with a fixed catalyst bed in the isothermal granules approximation

Abstract

A one-dimensional heterogeneous model has been developed for a cat6alytic fixed-bed Fischer-Tropsch (FT) synthesis reactor in the isothermal granules approximation. The FT process has been simulated for a laboratory-scale reactor. The effects of the linear gas velocity and of the inner diameter of the reactor on the thermal stability of the process are considered. The size of the reactor is limited by the possibility of a “thermal explosion” occurring in the frontal layer of the catalyst. Raising the linear gas velocity enhances heat transfer, thereby reducing the overheating of the catalyst bed. The synthesis of solid hydrocarbons can be conducted in reactors no larger than 18 mm in diameter. According to calculations, the maximum temperature drop in a 3-, 4-, and 6-m-long reactor is 4.7, 4.2, and 3.6°C, respectively. The corresponding CO conversion is 35.0, 34.4, and 33.9%, respectively. For producing liquid hydrocarbons in a high-performance reactor, it is necessary to decrease its inner diameter to 12 mm. In this case, the maximum temperature drop at a reactor length of 3, 4, and 6 m is 9.6, 8.7, and 7.6°C, and the CO conversion is 78.0, 77.4, and 76.7%, respectively. The mathematical model devised here provides means to estimate the necessary design parameters of the reactor and the appropriate FT synthesis conditions for producing liquid or solid hydrocarbons.