Comparative reactor, process, techno-economic, and life cycle emissions assessment of ethylene production via electrified and thermal steam cracking

Abstract

Decarbonizing thermal steam cracking (TSC) of hydrocarbons – the primary pathway for ethylene production – remains essential for reducing the carbon footprint of the global chemical industry. Proposed decarbonization strategies include CO₂ capture and storage (CCS) as well as the use of electricity to provide high-temperature heat for the reaction in lieu of fossil fuel combustion. Here, we undertake a multi-scale assessment of recently proposed internal electric-resistance-heated (i-ERH) reactors for enabling electrified steam cracking (ESC), assessing both reactor-level performance and process-level integration. We compare the ESC process against the conventional TSC process with and without post-combustion CO₂ capture using ethane as the feed, in terms of process design, product yield, energy requirements, cost, and life cycle emissions. Reactor-level modeling indicates that i-ERH reactors can increase ethylene yield compared to conventional externally heated reactors using fuel combustion while also reducing reactor size. These reactor-level improvements translate into lower process-level capital expenditures (12% lower than TSC in our base case) and reduced feedstock consumption (16% lower than TSC), which can partially or fully offset the cost of increased energy imports (91% higher) under the evaluated electricity and fuel supply scenarios. While higher ethylene yields reduce chemical (C₃+) co-product revenues for the ESC process, this can be mitigated by the sale of hydrogen and methane byproducts that are otherwise combusted in the TSC process. The emissions impacts of ESC versus TSC, and TSC-CCS are sensitive to the emissions intensity of the electricity supply: under 2022 Texas grid conditions, ESC emissions would be 50% higher than TSC, but future grid electricity supply scenarios for 2035 result in 20.8–47.7% lower emissions. Through sensitivity analysis, we identify the combinations of electricity price (75–113 $ per MWh), ESC reactor capital cost, and electricity emissions intensity (≤0.2 t CO₂-equivalent (CO₂-eq) per MWh) that enable carbon abatement costs of $100 per tonne CO₂ or lower relative to the TSC process. We also find that reactor configurations maximizing ethylene yield do not always correspond to the lowest process levelized cost, underscoring the importance of integrating detailed reactor- and process-level modeling for economic and environmental assessment of novel processes like ESC.