Process integration and life cycle assessment of ethane thermal cracking, carbon capture, green hydrogen, CO2 hydrogenation and methanol to olefins

Abstract

The olefins production relies on thermal cracking, which emits significant greenhouse gas. This study proposed a novel clean olefins production process, which utilizes cracked hydrogen from ethane cracking, to converted captured CO₂ from flue gas into methanol and finally to produce olefins. A real industrial plant with production rates of 819200 t/y of ethylene and 77520 t/y of propylene is selected for case study. The proposed processes are simulated in Aspen Plus, with consideration of heat integration. By generating two optimal heat exchanger networks for high-capacity and low-capacity operations scenarios, increased heat recovery of 35.11 MW and 29.33 MW can be achieved compared to the base cases. This results in an improvement in process energy efficiency through effective heat integration between the ethylene, CCS, and MTO processes. The life cycle assessment shows that all cracked hydrogen can convert 70 % CO₂ from flue gas. In this scenario, the global warming potential (GWP) is 1.64 kg CO₂ eq/kg of olefins, slightly higher than demonstration industrial plant (1.53). If 85 % of CO₂ is converted with support of electrolyzer and photovoltaic power, although the GWP during production process decreases to 1.47, the manufacture of electrolyzer leads to significant emission and which is undesirable.