Life cycle assessment of carbon capture and utilization from ammonia process in Mexico

Abstract

Post-combustion CO₂ capture (PCC) of flue gas from an ammonia plant (AP) and the environmental performance of the carbon capture utilization (CCU) technology for greenhouse gas (GHG) emissions to an enhanced oil recovery (EOR) system in Mexico was performed as case study. The process simulations (PS) and life cycle assessment (LCA) were used as supporting tools to quantify the CO₂ capture and their environmental impacts, respectively. Two scenarios were considered: 1) the AP with its shift and CO₂ removal unit and 2) Scenario 1 plus PCC of the flue gas from the AP primary reformer (AP-2CO₂) and the global warming (GW) impact. Also, the GW of the whole of a CO₂-EOR project, from these two streams of captured CO₂, was evaluated. Results show that 372,426 tCO₂/year can be PCC from the flue gas of the primary reformer and 480,000 tons/y of capacity from the AP. The energy requirement for solvent regeneration is estimated to be 2.8 MJ/kgCO₂ or a GW impact of 0.22 kgCO_2e/kgCO₂ captured. GW performances are 297.6 kgCO_2e emitted/barrel (bbl) for scenario one, and 106.5 kgCO_2e emitted/bbl for the second. The net emissions, in scenario one, were 0.52 tCO_2e/bbl and 0.33 tCO_2e/bbl in scenario two. Based on PS, this study could be used to evaluate the potential of CO₂ capture of 4080 t/d of 4 ammonia plants. The integration of PS-LCA to a PCC study allows the applicability as methodological framework for the development of a cluster of projects in which of CO₂ could be recycled back to fuel, chemical, petrochemical products or for enhanced oil recovery (EOR). With AP-2CO_2, "CO₂ emission free" ammonia production could be achieved.

Keywords: Ammonia process; Carbon capture and utilization (CCU); Enhanced oil recovery; Global warming; Life cycle assessment; Process simulation.