Process design and economic assessment of converting CO2 to liquid fuels

Abstract

Conversion of CO2 to fuels is one of the long-term solutions to reduce dependence on fossil fuels and mitigate climate change. Our previous study has already assessed the Power-to-Liquid (PtL) process by means of water electrolysis, reverse water-gas shift (RWGS) reaction and Fischer-Tropsch (FT) synthesis. However, the source of CO2 supply has not been identified and the net production cost (NPC) of such synthetic fuels remains much higher than that via conventional petrochemical process. In this work, we have extended our study with advanced CO2 capture technologies and optimised process integration. Several commercial acid gas separation technologies such as amine scrubbing and Selexol® as well as novel methods using phase change solvents have been evaluated and adopted for PtL process. To reduce the energy demand, various process designs and heat integration concepts have been conducted. For example, using process heat from FT reactor for solvent regeneration in the thermal desorber can save more than 80 % of the total energy requirement for the entire CO2 capture system. Aspen Plus® process simulation of the optimised system design has been implemented and the in-house assessment programme TEPET (Techno-Economic Process Evaluation Tool) has been employed for the detailed analysis. The capital expenditure (CAPEX), operational expenditure (OPEX) and fuel NPC are hence estimated upon industrial standards, literature data and simulation results. Cost estimation according to class III and IV of the ICEAA is achieved, offering an 30 % accuracy. To minimise the cost of the overall CO2-to-Fuels process, the potential of using low price industrial CO2 sources with novel carbon capture technologies and improved system integration of all process units has been extensively evaluated. The sensitivity analysis has also been carried out to predict the possibility of future NPC reduction.