Technical analysis of the modified Fischer-Tropsch synthesis process for direct CO2 conversion into gasoline fuel: performance improvement via ex-situ water removal

The modified Fischer-Tropsch synthesis (FTS) process is a promising technology for direct CO2 conversion into liquid fuels. However, the low yield of liquid fuels (below 29%) observed during CO2-FTS process is still of great concern for commercial deployment. Therefore, new strategies are needed to improve both CO2 conversion and liquid fuel yield during CO2-FTS process. A steady-state model based on first principles and a modified Anderson-Schulz-Flory (ASF) distribution was developed for the CO2-FTS process to predict gasoline range hydrocarbons (C5-C11). The model was implemented in Aspen Plus® using Fortran® routines and model validation was performed for different H2/CO2 feed ratios. Two process configurations (including a three-stage reactor in series and a single reactor with recycle) were considered for CO2-FTS performance analysis and improvement through ex-situ water removal. Both CO2-FTS process configurations showed significant improvements in CO2 conversion (from 34 to above 70%) with up to 61.0% gasoline yield. Though the single reactor with recycle achieved a higher CO2 conversion and gasoline production rate than the 3-stage reactor in series, the comparative analysis at the same CO2 conversion of 71.5% revealed that both process configurations have a similar process efficiency of roughly 66.4%.