A Trickle Fixed-Bed Recycle Reactor Model for the Fischer-Tropsch Synthesis

Abstract

A trickle fixed-bed reactor model for the Fischer-Tropsch synthesis applicable to both cobalt and iron catalysts which accounts for gas and liquid recycle is described. A selection of kinetic models for both iron and cobalt catalysts (4 each) is included in the reactor model and their effect on model predictions is compared. While the model is 1-D and reaction rates are determined for quasi-average radial bed temperatures, a correlation is used to account for radial thermal conductivity and radial convective heat transfer. Traditional pressure drop calculations for a packed column were modified with a correlation to account for trickle-flow conditions. In addition to describing the model in detail and showing validation results, this paper presents results of varying fundamental, theoretically-based parameters (i.e. effective diffusivity, Prandtl number, friction factor, etc.). For example, the model predicts that decreasing effective diffusivity from 7.1E-09 to 2.8E-09 m 2 /s results in a lower maximum temperature (518 K vs. 523 K) and a longer required bed length to achieve 60% conversion of CO (8.5 m vs. 5.7 m). Using molar averages of properties to calculate the Prandtl number for the gas phase (recommended by the authors) results in average bed temperatures up to 10 K higher and reactor lengths 17-45% shorter than assuming a Prandtl number of 0.7. Using the Tallmadge equation to estimate friction losses, as recommended by the authors, results in a pressure drop 40% smaller than using the Ergun equation. Validation of the model was accomplished by matching published full-scale plant data from the SASOL Arge reactors.

Highly active and stable supported iron Fischer–Tropsch catalysts: Effects of support properties and SiO2 stabilizer on catalyst performance

“…Fischer-Tropsch Synthesis (FTS) was conducted in a fixed-bed reactor (stainless steel, 3/8 inch OD) described previously [19]. Each sample (0.25 g, 250-590 lm) was diluted with 1 g quartz sand or silicon carbide to improve isothermality in the catalytic zone.…”

Mathematical model of obtaining a hydrocarbon fuel based on the fischer­tropsch pathway in a stationary layer of the cobalt­based catalyst

“…It is shown that the best catalysts for the FT-synthesis are those catalysts that are based on ferrum and cobalt [6,[8][9][10][11][12]15]. Paper [10] compares these catalysts.…”

Iron Fischer-Tropsch Catalysts Prepared by Solvent-Deficient Precipitation (SDP): Effects of Washing, Promoter Addition Step, and Drying Temperature

“…Fischer-Tropsch Synthesis (FTS) was conducted in a fixed-bed reactor (stainless steel, 3/8 inch OD) described previously [22,23]. Each sample to be tested (0.25 g, 250-590 μm) was diluted with quartz sand (−50/+70 mesh) to improve temperature stability in the catalytic zone.…”

“…A report describing the preparation and performance of one Fe FT catalyst using the SDP method was published earlier this year [22]. It was also the subject of a dissertation [23].…”