Techno-Economic Evaluation of Deoxygenation Methods of Pyrolysis Oil

Sammanfattning

This master’s thesis investigates deoxygenation strategies for biomass-derived pyrolysis oil (PO). The study focuses on industrial scalability, economic feasibility, and compatibility with existing refinery infrastructure. It was conducted in collaboration with Preem AB, aligning with their renewable fuel initiatives. The high oxygen content and instability of PO present challenges when integrated into conventional refining units, such as catalyst deactivation and corrosion. Therefore, this work evaluates approaches that can stabilize and improve the properties of PO in order to be introduced to conventional refinery processes, while remaining economically and environmentally viable. The first part of the thesis consists of a literature review, analyzing current upgrading technologies. This includes evaluation of current scale, results and up-scaling challenges. Based on this review and technical assessment, a process scheme is proposed that includes an initial stabilization step followed by mild hydrotreating and catalyst recycling. The findings recommend early onsite stabilization at the PO production facility, organic solvent addition proposed, to prevent aging and polymerization reactions. This is followed by a hydrotreating step, using slurry hydrocracking at the refinery. This approach offers robust method for upgrading PO so that it can be co-processed in existing refinery infrastructure, such as fluid catalytic cracker, agreeing with Preem’s ambition to reduce dependence on fossil feedstocks. A techno-economic analysis of an upscaled version of the process was conducted to identify key cost drivers, investment and operational costs. Further on, a net carbon dioxide emission assessment was performed to evaluate the environmental impact of the process. The analysis was based on two scenarios: one using fossil-derived feedstocks and utilities, and the other using renewably based sources, to enable comparisons on price differences and carbon dioxide reductions. The total capital cost was calculated to 197 million SEK, assumingly underestimated due to simplifications and uncertainties. Nevertheless, the analysis identified the primary cost drivers during operation which is highly valuable for future work. In both scenarios, the cost of PO was the dominating cost, which cannot be avoided. Additionally, methanol and bio-methanol were identified as the second largest cost contributors. The estimated price of PO was 23 SEK/kg PO in the fossil scenario, and 28 SEK/kg PO in the renewable scenario. The carbon dioxide emissions varied significantly between the two cases, estimated to 4.8 kg CO2/kg PO and 0.2 kg CO2/kg PO in the fossil and green scenario respectively. These results demonstrate that a greener operation does not result in an unacceptable cost increase, but offers a dramatical reduction in emissions. Further on, the results highlight the importance of early stabilization to prevent oil degradation and equipment corrosion. Further on, this is followed by a hydroprocessing stage resistant to coke formation that can manage feedstock with variations in content. The study concludes that, with optimized process design and conditions, upgraded PO can play a significant role in Sweden’s transition toward a renewable energy future while cost competing with fossil fuel.