A generic process simulation model of a gas-phase Fischer-Tropsch Synthesis (FTS) and supercritical phase Fischer-Tropsch Synthesis (SC-FTS) processes were developed based on previous and ongoing work at Auburn University. The models consist 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 models have been developed using data available in the open literature and their performances are currently being validated against the latest CFFS experimental data. Synthesis gas production from steam reforming is included. The downstream processing results are in two products, i.e. a gasoline and a jet fuel similar to JP-5, including paraffin, olefin and oxygenate products. The product distribution is obtained using the Anderson-Schulz-Flory (ASF) distribution for the gas-phase model. In supercritical phase, the product distribution is much more narrow compared to traditional gas-phase FTS due to the vapor-like transport properties and liquid-like thermal properties in the supercritical phase. A hydrocracking reactor is added to convert the heavier compounds back to fuel range products. Using experimental data generated within the Consortium for Fossil Fuel Science (CFFS), models have been developed for analysis of the supercritical water reforming (SCWR) process. The high-pressure hydrogen produced from supercritical water reforming of biomass is intended for injection in the SC-FTS process during the cracking/isomerization step and will be included in the model as well. In addition, the light fraction from gas-phase model is converted to synthesis gas and recycled to the FTS reactor by steam reforming. 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 experimental work.