Integration of co-electrolysis in a Power-to-Fuel process

The growing concern about greenhouse gas emissions and their consequences on climate change has driven the interest in this work. Over the past few decades, CO2 emissions from human activities have steadily increased, particularly in developing countries. Globally, emissions rose from 25.2 in 2000 to 37.4 Gt in 2023. In Europe, a slight decrease in greenhouse gas emissions has been observed, but this reduction is not uniform across all economic sectors. While the industrial and energy production sectors have seen significant decreases in emissions, the transportation sector has not followed this trend. Currently, transportation accounts for 23.6% of European emissions, compared to 18.0% in 2000.In the transportation sector, there are two main categories: light and heavy transportation, including maritime and aviation. While light transportation can be directly electrified using batteries, heavy transportation cannot be due to the high energy demands and long distances involved. Instead, green hydrogen, produced by electrolysis using renewable electricity, offers a viable alternative for powering trucks, tankers or trains while decarbonizing these sectors. However, for aviation, replacing kerosene is challenging due to its high volumetric energy density. Therefore, indirect electrification relies on producing synthetic kerosene. This can be achieved through two pathways: methanol-to-jet and Fischer-Tropsch. Currently, only the Fischer-Tropsch process is approved by regulations. Both pathways require CO2 to supply the carbon needed for hydrocarbon synthesis, making CO2 capture a crucial element in creating sustainable aviation fuels. CO2 concentrations in the atmosphere can be reduced through carbon capture and storage or utilization (CCUS). In the case of utilization, CO2 is transformed into valuable products. Carbon capture can occur at the emission source or directly from the atmosphere, in this case it is called Direct Air Capture. A limitation of kerosene production via the Fischer-Tropsch process is that CO2 must first be converted into the more reactive molecule CO. This reaction, used to produce CO, is called reverse water gas shift and is an energy and hydrogen consuming unit, the hydrogen is provided in excess to have a mixture of CO and H2 known as syngas. One way to reduce the energy cost of this process is to reduce CO2 and water simultaneously, in a process called co-electrolysis taking place in a high-temperature electrolyser. Chapter 1 will present the reason and the context of this work. Chapter 2 will focus on the simulation of a centralized Power-to-Jet Fuel plant. This work is the first in the literature to propose a process focused on the production of jet-fuel. The Fischer-Tropsch process is a mature and reliable pathway for hydrocarbon synthesis, with a wide spectrum of technological options and high plant efficiency exceeding 80% e-kerosene selectivity. This efficiency is estimated through a combination of plant simulation with Aspen Hysys and the simulation of the reactor with Matlab. Chapter 3 will focus on the techno-economic analysis and the life cycle assessment of the fuel produced from such a pathway, along with the legal context of the production of sustainable aviation fuel. An economic and environmental comparison is conducted between two different technologies of electrolyser: PEM and SOEC. Chapter 4 will discuss the modelling and simulation of co-electrolysis in the presence of methane. Methane and other light gaseous hydrocarbons could represent a large fraction of the production of a Fischer-Tropsch reactor, generally between 10 and 30% by mass, these molecules being less valuable have to be recycled. This chapter will present the model and will cover the experimental validation of the model. The addition of methane to the SOEC could provide a means to increase the efficiency of the process and reduce the installed CAPEX. In chapter 5, the model of methane reforming will be used in the simulation of jet fuel production with biogas upgrading, the impact of this reforming on the system will be studied, and a techno-economic analysis of the decentralized process will be performed. Finally, the conclusion will discuss the outlook of this PhD research and suggest directions future work.