Techno-economic analysis of CO2/steam co-electrolysis process and synfuel production process coupled with steel manufacturing process

Over the past few decades, reducing CO2 emissions has attracted attention at an industrial level worldwide. This study focuses on utilizing both the byproduct gas, including CO2, and waste heat produced from the steel-making process to produce synthetic fuel by integrating solid oxide electrolyzer cell (SOEC) technology with downstream Fischer-Tropsch and hydrocracking processes. CO2 can be collected from the byproduct gas and used as a feed for the SOEC, and waste heat from the steel-making process can be utilized as the main heat source for operation of the SOEC at high temperatures and to generate electrical power through heat recovery and steam generation (HRSG) as an energy source for the SOEC. The syngas (H-2 and CO) produced from the SOEC is then converted to synthetic oil through the FT process, and the yield of the synthetic oil is increased via the hydrocracking process by converting heavy oil to lighter fractions. The entire process was modeled using Aspen HYSYS software, and pinch technology was adopted to maximize the energy efficiency of the process. As a result, CO2 release was reduced by 452 tons/day and syngas was produced by 336.8 tons/day. The syngas produced was then converted to synthetic oil (306.7 tons/day) and light gas (44.24 tons/day). Economic assessment was completed based on the discounted cash flow method for two cases: electricity tariffs and new renewable energy prices. When the electricity tariff is implemented, profit is achieved in seven years, whereas the system becomes profitable in four years when newly regenerated surplus energy is utilized. If the price of renewable energy is reduced, profits may be achieved earlier.