Process Modeling and Evaluation of Plasma-Assisted Ethylene Production from Methane

Evangelos Delikonstantis,Marco Scapinello,Georgios Stefanidis

doi:10.3390/pr7020068

Abstract

The electrification of the petrochemical industry, imposed by the urgent need for decarbonization and driven by the incessant growth of renewable electricity share, necessitates electricity-driven technologies for efficient conversion of fossil fuels to chemicals. Non-thermal plasma reactor systems that successfully perform in lab scale are investigated for this purpose. However, the feasibility of such electrified processes at industrial scale is still questionable. In this context, two process alternatives for ethylene production via plasma-assisted non-oxidative methane coupling have conceptually been designed based on previous work of our group namely, a direct plasma-assisted methane-to-ethylene process (one-step process) and a hybrid plasma-catalytic methane-to-ethylene process (two-step process). Both processes are simulated in the Aspen Plus V10 process simulator and also consider the technical limitations of a real industrial environment. The economically favorable operating window (range of operating conditions at which the target product purity is met at minimum utility cost) is defined via sensitivity analysis. Preliminary results reveal that the hybrid plasma-catalytic process requires 21% less electricity than the direct one, while the electric power consumed for the plasma-assisted reaction is the major cost driver in both processes, accounting for ~75% of the total electric power demand. Finally, plasma-assisted processes are not economically viable at present. However, future decrease in electricity prices due to renewable electricity production increase can radically affect process economics. Given that a break-even electricity price of 35 USD/MWh (without considering the capital cost) is calculated for the two-step plasma process and that current electricity prices for some energy intensive industries in certain countries can be as low as 50 USD/MWh, the plasma-assisted processes may become economically viable in the future.

Highlights

In view of preventing a global temperature rise of 2 ◦ C [1], efforts should be pursued to mitigate the greenhouse gas emissions (GHGs) [2]
Challenges associated with catalyst utilization such due to carbon formation and accumulation; one unit will be in operation, while the other one will be as catalyst activation, regeneration, poisoning and aging do not disturb the continuous operation
Catalyst regeneration cycles are usually longer the two-step process, the hydrogenation catalyst clogging by carbon or other viscous hydrocarbons than the operating cycle of Nanosecond pulsed discharge (NPD)-R, which makes the continuous production even more complicated

Summary

Introduction

In view of preventing a global temperature rise of 2 ◦ C [1], efforts should be pursued to mitigate the greenhouse gas emissions (GHGs) [2]. Due to high GHGs share the ethylene industry possesses among the other chemical processes, decarbonization of ethylene production processes could significantly impact the chemical industry’s carbon footprint. Reduction in energy intensity [5] and thereby lower GHGs. Deep decarbonization of the ethylene industry can only be achieved via carbon capture and storage, use of bio-based feedstock, increase in the recycling of plastics, and shifting to zero-carbon electricity [6,7,8,9]. In conventional ethylene production process, GHGs are primarily sourced from the fuel and other off-gases (formed in ethylene production process), which are burned to provide the heat required for the oil-based feedstock cracking in high-temperature pyrolytic furnaces. Switching from the conventional thermally driven furnaces to electricity-driven reactors, and from fuels combustion for heat generation to zero-carbon electricity for electron-impact reactions activation may be the solution towards CO2 -neutral ethylene production

Methods

Results

Conclusion