(390b) Pathway to Sustainable Olefin Production Via Sector Coupling: Techno-Economic and Life Cycle Assessments of Naphtha-Methanol to Olefin Process Utilizing Blast Furnace Gas

The steel and petrochemical industries are major sources of greenhouse gas (GHG) emissions in South Korea, accounting for 60.6% of total industrial emissions ^[1]. Reducing these emissions is crucial for achieving the net-zero emission target. We introduce a novel sector-coupling process, namely, the low-carbon process (LCP), that utilizes blast furnace gas (BFG) from a steel mill plant to manufacture light olefins. In the LCP, carbon monoxide (CO) is recovered from BFG through multiple separation steps, including membrane contactor, gas separation membrane, and vacuum pressure swing adsorption (VPSA), and mixed with additional syngas produced via steam methane reforming (SMR). The prepared syngas is subsequently utilized to synthesize methanol. Afterward, light olefins (ethylene and propylene) are produced through the naphtha-methanol to olefin (NMTO) process, which requires approximately 30% less thermal energy than conventional steam naphtha cracking (SNC) processes. We conduct a techno-economic analysis (TEA) and life cycle assessment (LCA) to evaluate its GHG reduction potential and economic feasibility, respectively. We assess the climate change impact of the LCP using EF 3.1 and compare it with the baseline scenario. System expansion and mass allocation are applied with the system boundary defined as cradle-to-gate focusing on the Republic of Korea. In addition, we comprehensively analyze the olefin production cost and net present value to evaluate the profitability.

Major GHG emission sources include direct emissions from the heat supply in the SMR unit and indirect emissions associated with the production of naphtha used as a feedstock in the NMTO process. Meanwhile, it was found that carbon dioxide (CO₂) present in the BFG, which is removed in the CO separation process, still acts as a factor hindering the mitigation of GHG emissions. Since this CO₂ can be separated at high purity (95 mol.%) within the LCP, we consider a scenario of carbon capture and storage (CCS) to mitigate GHG emissions further. Economic analysis shows that naphtha constitutes the largest portion of the production costs among raw materials, followed by fixed costs and depreciation. Moreover, a Sobol sensitivity analysis is conducted to identify which life cycle inventories (LCIs) used in our LCA and material prices affect the results primarily. We then evaluate the feasibility of adopting carbon-reducing olefin production processes in different countries (such as China, USA, and Germany) and specific price conditions for sustainable operation.

Reference

[1] Korea Energy Agency. (2023). 2022 statistics on energy consumption and greenhouse gas emissions in the industrial sector: Mining and manufacturing. Korea Energy Agency.