Design and systems-level performance analysis of petroleum coke conversion strategies

Abstract

Petroleum coke (petcoke) is a solid waste product of crude oil refinery operations with disposal issues. Therefore, this thesis focuses on systems level performance analysis of design configurations by which petcoke can be disposed of in the most environmentally benign and cost-competitive pathway. In the systems evaluated, we explored the environmental and cost benefits of utilizing the energy stored in the refinery solid waste (petcoke) to produce liquid transportation fuels and electricity. Specifically, we proposed petcoke as a feed to produce liquid fuels via Fischer-Tropsch synthesis. For power generation, we explored the performance of petcoke in an integrated gasification combined cycle (IGCC) and oxy-combustion technology. To minimize greenhouse gas (GHG) emissions, carbon capture and sequestration (CCS) were implemented in some of the designs allowing further performance analysis of the variants of the designs which were operated with and without CCS. In the petcoke to liquid fuels study, three design strategies that operated with and without CCS namely petroleum coke standalone gasification (PSG), petroleum coke gasification integrated natural gas reforming (PG-INGR), and petroleum coke gasification external natural gas reforming (PG-ENGR) were proposed. To compare the performance of the designs, performance metrics such as fuel and thermal efficiencies, net present value, minimum diesel selling price, and direct CO2 emissions were employed. Overall, the PG-INGR design outperformed the other designs and showed to be a feasible candidate design for petcoke to liquids process. Subsequently, a cradle-to-grave environmental life cycle impact assessment of a petcoke derived diesel for a functional unit of 1 km distance driven in a diesel-powered vehicle was investigated for two possible locations in Canada: Ontario and Alberta provinces. These petcoke processes were compared to the conventional crude oil and oil sands derived diesel processes. In terms of GHG emissions, the results showed that there was no clear superior design amongst the three CCS enabled processes for the plants located in Ontario, but they outperformed the conventional crude oil and oil sands derived diesel processes.When the cost of CO2 avoided (CCA) was factored into the analysis for the petcoke processes, the PG-INGR design had lower costs and thus confirms it as the viable design to adapt for liquids production. Exploring the benefits of a waste source of fuel, the techno-economic and life cycle analysis (LCA) of petcoke was further examined in the IGCC power plant operated with CCS. This design performance was compared against the coal based IGCC and supercritical pulverized coal (SCPC) power plants operated with CCS of the same net power output based on its levelized cost of electricity, thermal efficiency, feed consumption rate, and direct GHG emissions. Results showed that the petcoke power plant outperformed both reference systems in both economics and environmental impacts. Finally, petcoke was further explored as fuel in the oxy-combustion power plant designed to operate with and without carbon capture and sequestration. Our study of the oxy-combustion power plant further included the purification of the captured CO2 stream via cryogenic distillation to meet pipeline specifications. This analysis was to compare its performance to that of petcoke IGCC power plant. LCA and CCA of the petcoke oxy-combustion power plant designs were also presented. Overall, the results showed a cost-competitive source of electricity generation even for the design with highly purified CO2. In terms of environmental impacts, the LCA study confirmed the minimal emission tendency of the petcoke oxy-combustion system even when the indirect petcoke emissions were considered.