Process simulation of a near-zero-carbon-emission power plant using CO₂ as the renewable energy storage medium

In this paper, process simulation of a near-zero-carbon-emission power plant using CO₂ as the renewable energy storage medium was carried out. Liquid fuels that can be burned either in boilers or compression ignition engines to generate electricity have been the target products. The CO₂ and H₂O produced from combustion are recirculated back to the synthesis units, thus forming a closed cycle of “renewable energy (unstable energy supply) + CO₂ + H₂O → liquid fuels → electricity (stable supply)”. This novel closed loop energy storage process integrated with a 670 MW supercritical power plant was analyzed using the Aspen Plus software package. Methanol was selected as the targeted liquid fuel through three major synthesis routes: CO + H₂, CO₂ + H₂ and CO₂ + H₂O, in which CO and H₂ came from the electrolysis of CO₂ and H₂O. The performances of the three methanol synthesis routes were thermodynamically analyzed. The results show that the optimal methanol synthesis route is the direct conversion of CO₂ and H₂O through electrocatalysis when CO₂ conversion is above 42%, while when CO₂ conversion is below 42% the best choice turned out to be the CO hydrogenation. The direct conversion of (CO₂ + H₂O) using electrocatalysis method was adopted as the liquid fuel synthesis route for the near-zero-carbon-emission power plant. The overall CO₂ emission from the near-zero-carbon-emission power plant is 44.13 kg/MWh accounting for just 6.45% of the advanced coal fired power plant