Defense Committee:

Abstract

The global energy mix remains predominantly reliant on fossil fuels. While this dependence has driven industrial and economic growth, it has resulted in an increase in CO₂ emissions, a decline in energy return on investment, and degradation of the environment. Addressing these challenges requires a gradual shift toward a sustainable and circular carbon management model. While there is extensive literature on individual processes, there is considerable room for further investigation into how processes can be integrated. This research focuses on integrating vacuum residue (VR) gasification, CO₂ capture, and CO₂-plume geothermal (CPG) processes.

This dissertation presents a developed comprehensive process simulation to analyze the performance of each subsystem. First, an Arabian VR gasification model was constructed to study the impact of varying operational conditions, such as gasifier temperature and equivalence ratio, on the conversion of heavy residue to hydrogen-rich syngas. After that, the H₂ yield and associated CO₂ emissions of Arabian VR gasification were determined under optimized conditions. Then, the CO₂ capture process using a physical solvent was modeled to determine the capture efficiency. After that, a techno-economic analysis (TEA) of the integrated processes was conducted to assess the overall economic viability.  Next, a CPG model combined with an organic Rankine cycle (ORC) was developed to study the effects of varying surface and subsurface properties on geothermal energy recovery. This included conducting a sensitivity and statistical analysis on various parameters (e.g., permeability, heterogeneity, ORC working fluid, and turbine inlet conditions) to understand their influence on heat extraction.

The economic assessment in this work indicated a levelized cost of H₂ of 2.425 $/kg with carbon capture and 2.329 $/kg without. Furthermore, the findings of this research revealed that mass flow rate and temperature influence power output, while pressure and CO₂ fraction exhibit complex, non-linear interactions, especially at lower CO₂ purities. The presence of water was found to enhance expansion work under specific conditions but may introduce operational challenges. In addition, the addition of ORC enhanced CPG system performance, with cyclopentane and R-245FA demonstrating distinct performance. The findings of this research demonstrated how process integration can contribute to circular carbon strategies. They provided the basis for conducting a TEA of such a complex system to determine the feasibility of this holistic approach, bottlenecks, and advantages over standalone systems.