Optimization of coal-to-liquid processes; A way forward towards carbon neutrality, high economic returns and effective resource utilization. Evidences from China

Abstract

As the world's largest consumer of coal, China is committed to developing a carbon–neutral coal industry. For this purpose, upgrading the carbon emission-intensive coal-chemical industries, such as coal-to-liquids (CTL) is imperative. This study develops a technical–economic framework to model and test four promising CTL upgrading processes. First and second processes involve low-temperature Fischer-Tropsch (FT) synthesis practices with larger gasifiers and air-separating units than the current level. Third, the process combines olefin and fuel co-production practices that utilize low- and high-temperature FT synthesis processes. Finally, the process produces both electricity and fuel by sending the tail gas of the synthesis process to an integrated cycle. Aspen Plus® is used to simulate the chemical processes, and the financial cost accounting model of the American Association of Cost Engineers is utilized to estimate the financial costs accurately. The results show that the upgraded processes can achieve an energy efficiency of more than 48 %, which is 6 % higher than the existing coal-to-oil process. Additionally, the break-even point is 2 %–14.45 % lower than the actual process, reducing carbon emissions by 2.78 %–10.34 %. According to these findings, the upgrade can help China reach its carbon neutrality targets and significantly contribute to global climate change and sustainable development goals.