Decarbonization in Carbon-Intensive Industries - An Assessment Framework for Enhanced Early-Stage Identification of Optimal Decarbonization Pathways

Licentiatavhandling, 2024

Carbon-intensive industries currently account for a quarter of global annual CO2 emissions. Achieving mandated climate targets necessitates the rapid implementation of decarbonization technologies in these industries. Such deployments typically involve substantial upfront investments amidst technical, economic, and policy uncertainties. Consequently, careful selection of decarbonization technologies or a combination thereof, coupled with measures like process electrification and energy efficiency, becomes increasingly crucial. In this context, numerous early-stage comparative assessment studies utilizing process integration and techno-economic methods to identify cost-optimal decarbonization technologies in unabated industries often overlook key considerations at the systems, plant, and site levels.

This thesis presents limitations in existing methodological approaches for comparing decarbonization pathways, spanning systems, plant, and site-level considerations. A generalized hybrid assessment framework was developed that addresses these limitations with individual framework methodologies developed in the appended papers. At the systems level, extended boundaries and exergy as a metric were used to compare two CO2 capture technologies with inherently different exergy requirements per unit of CO2 captured, considering plant owner and end-user perspectives. At the plant level, an iterative exergy-pinch analysis combined with techno-economic analysis was developed to identify promising process modifications in unabated process plants that maximize overall exergy utilization and CO2 avoidance with successive designs towards net-zero emissions. Finally, a site-specific techno-economic analysis was developed incorporating site-specific factors expected to impact the final cost of CO2 avoidance. These frameworks were demonstrated with industrial case studies on bio-CHP in a district heating system, propane dehydrogenation, and steam cracker plant, respectively.

The case study results show that preserving electric power in bio-CHP plants through the integration of amine-based CO2 capture technology, complemented with industrial heat pumps, would not only ensure a greater potential for district heat delivery but also provide greater product flexibility in terms of both heat and power production, and negative CO2 emissions. The iterative exergy-pinch analysis applied to the propane dehydrogenation plant revealed unconventional process modifications, resulting in a substantial reduction in CO2 avoidance cost (58–70%) compared to CO2 capture from the highly diluted flue gas stream from the unmodified process (167–181 €/tCO2). Finally, utilizing site-specific techno-economic analysis, the cost escalation due to site-specific factors, in terms of CO2 avoidance, was approximately 80% higher for the post-combustion CO2 capture process (43 €/tCO2) compared to the alternative of hydrogen-firing in the cracker furnaces, through the pre-combustion CO2 capture process (24 €/tCO2). These findings reveal that cost factors that are commonly neglected could significantly influence the choice of decarbonization technology at an early stage. In summary, the proposed assessment framework, combining these individual framework methodologies, can be utilized to obtain a comprehensive early-stage indication of the optimal decarbonization pathway for specific industrial sites.