New Supercritical Method to Capture CO₂ from N₂ and H₂ Gas Mixture in Ammonia/Urea Production Plants

Abstract

Great efforts are being made to reduce anthropogenic carbon dioxide (CO2) emissions to the atmosphere to mitigate climate change. Different CO2 capturing techniques are available; however, they have many drawbacks. Through this study, a new method to physically separate CO2 from its mixture with nitrogen (N2) and hydrogen (H2) gases at supercritical conditions is investigated. This new separation method was tested experimentally at 38 °C and 200 bar. Through a two-stage separation, a high-purity CO2 stream of 99% concentration and pure H2 and N2 streams of 96.6 and 91% concentration were obtained, respectively. By using the Aspen Hysys software, the economics of the integration of this new method in an ammonia and urea production plant was compared with that of a traditional plant having CO2 absorption units in place. The captured CO2 is utilized in the urea production plant, and the separated pure N2/H2 stream is utilized in the ammonia production plant. A reduction in the capital and operating costs was achieved, with a total savings of $3.32 × 108, which corresponds to 44.6% of the total cost compared to conventional amine-based capture. Our new supercritical phase separation method is economically feasible and could be useful in many energy-related industries.