Efficient Utilization of Greenhouse Gases in a Gas-to-Liquids Process Combined with CO2/Steam-Mixed Reforming and Fe-Based Fischer–Tropsch Synthesis

• Published in: Environmental science & technology Vol. 48; no. 14; pp. 8251 - 8257
• Main Authors: Zhang, Chundong, Jun, Ki-Won, Ha, Kyoung-Su, Lee, Yun-Jo, Kang, Seok Chang
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-07-2014
• Subjects: Air pollution caused by fuel industries; Alkenes - chemical synthesis; Applied sciences; Carbon Dioxide - chemistry; Chemistry, Inorganic - methods; Energy; Energy. Thermal use of fuels; Exact sciences and technology; Fuel processing. Carbochemistry and petrochemistry; Fuels; Gas processing; Greenhouse Effect; Hydrocarbons - chemical synthesis; Hydrogen - chemistry; Hydrogenation; Iron - chemistry; Methane - chemical synthesis; Models, Theoretical; Oils - chemical synthesis; Pollution reduction; Recycling; Stack gas and industrial effluent processing; Steam; Temperature; Methane; Greenhouse gas; Carbon dioxide; Production; Fischer Tropsch synthesis; Synthetic fuel; Steam reforming; Reforming; Performance; Synthesis gas; Modeling
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es501021u

Two process models for carbon dioxide utilized gas-to-liquids (GTL) process (CUGP) mainly producing light olefins and Fischer–Tropsch (F–T) synthetic oils were developed by Aspen Plus software. Both models are mainly composed of a reforming unit, an F–T synthesis unit and a recycle unit, while the main difference is the feeding point of fresh CO2. In the reforming unit, CO2 reforming and steam reforming of methane are combined together to produce syngas in flexible composition. Meanwhile, CO2 hydrogenation is conducted via reverse water gas shift on the Fe-based catalysts in the F–T synthesis unit to produce hydrocarbons. After F–T synthesis, the unreacted syngas is recycled to F–T synthesis and reforming units to enhance process efficiency. From the simulation results, it was found that the carbon efficiencies of both CUGP options were successfully improved, and total CO2 emissions were significantly reduced, compared with the conventional GTL processes. The process efficiency was sensitive to recycle ratio and more recycle seemed to be beneficial for improving process efficiency and reducing CO2 emission. However, the process efficiency was rather insensitive to split ratio (recycle to reforming unit/total recycle), and the optimum split ratio was determined to be zero.