(238b) Modeling and Optimization of Fischer-Tropsch Synthesis Processes

A generic process simulation model of a gas-phase Fischer-Tropsch Synthesis (FTS) process has been developed based on previous work at Auburn University. The model consists of the following main sections: 1. Synthesis gas production through reforming, 2. Gas clean-up, 3. Fischer-Tropsch reaction, 4. Separation and recycle of unreacted synthesis gas, 5. Fractionation of fuel range products from heavy waxes, 6. Cracking of heavies and fractionation of fuel range products. The model has been developed using data available in the open literature and its performance is currently being validated against the latest experimental data generated by researchers in the Consortium of Fossil Fuel Science (CFFS). The FTS reactor is modeled using data for the ARGE reactor (Ruhrchemie and Lurgi) and the downstream processing results in two products, i.e. a gasoline range fraction and a jet fuel similar to JP-8. The product distribution is obtained using the Anderson-Schulz-Flory (ASF) distribution for a Cobalt catalyst. A hydrocracking reactor is added to convert the heavier compounds back to fuel range products. In addition, the light fraction is converted to synthesis gas for recycle to the FTS reactor by steam reforming.

The gas-phase model is used as the foundation for a model of the supercritical phase Fischer-Tropsch Synthesis (SCF-FTS) process being developed at Auburn University. By operating the FTS reaction in a dense phase, the direct benefits are two-fold, i.e. vapor-like transport properties and liquid-like thermal properties. This means that the product distribution is much more narrow than traditional gas-phase FTS. Using experimental data generated within CFFS, models have also been developed for analysis of the supercritical water reforming (SCWR) for hydrogen production from biomass. The high-pressure hydrogen produced from supercritical water reforming is intended for injection in the SCF-FTS process during the cracking/isomerization step.

Economic and environmental analysis was performed through quantifying the level of environmental impact using EPA's WAR algorithm. In this way, experimental and theoretical efforts can supplement each other, providing direction for further research.