Assessing the efficiency of CO₂ hydrogenation for emission reduction: Simulating ethanol synthesis process as a case study

Hydrogenation of CO₂ to synthesize ethanol is a potential way to reduce CO₂ emissions while producing value-added fuels and chemicals. However, the emission of tail gas as well as the consumption of heat and electricity may also generate additional CO₂ emissions. This raises the question of how efficient this process is in reducing CO₂ emissions. In this study, Aspen Plus is used to investigate the efficiency of this process towards reduction of CO₂ emission. The effect of key parameters such as single pass CO₂ conversion, tail gas splitting ratio, and reaction temperature on CO₂ conversion efficiency, hot utility/electricity consumption, as well as CO₂ emission reduction/utilization rate is examined. It is recommended that a medium single pass conversion (e.g., 15%), a high splitting ratio (e.g., 0.8), and a relatively high reaction temperature (e.g., 250 ℃) for practical applications of this technology. With an annual CO₂ processing capacity of 268 kt, our study suggests that up to 86.9% of CO₂ emissions can be eliminated, resulting in the production of 141 kt/year of ethanol, demonstrating the high efficiency of this process in reducing CO₂ emissions.