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.