Evaluation of Environmental performance of Hypothetical Canadian Oxy-Fuel Combustion Carbon Capture with Risk and Cost Analyses
Faculty of Graduate Studies and Research, University of Regina
For at least the next few decades, fossil fuels will be used to supply energy globally, and without appropriate greenhouse gas control techniques, carbon dioxide (CO2) atmospheric emissions will continue to increase and pose an even more serious threat to humans and their environment. Therefore, the use of an effective CO2 capture technology has become important in ensuring the reduction of CO2 emissions. However, more raw materials and energy are required for the CO2 capture systems operation. Consequently, it is necessary to evaluate the environmental performance of the complete life cycle of the CO2 capture process in order to fully understand its environmental impacts. This research presents a life cycle assessment (LCA) study on a hypothetical oxy-fuel combustion CO2 capture system in Saskatchewan, Canada. The study analyses the oxy-fuel carbon dioxide capture and compares it with a lignite coal fired electrical generating station that has no capture system, as well as with post-combustion capture. The oxy-fuel combustion CO2 capture scenario showed a dramatic reduction of CO2 and other emissions to air. Thus, the impact on the categories of human health related to air quality and ecotoxicity in air were decreased compared to the “no capture” scenario. In addition, since the oxy-fuel combustion CO2 capture is an oxygen-based combustion and a closed loop system together with electrostatic precipitator (ESP), flue gas desulphurization (FGD), and CO2 purification and compression units, reductions were observed in the acidification of air, eutrophication, and smog air impact categories. However, the processes and operations in the CO2 capture system consumed additional energy and materials, which increased the environmental impacts in the ozone depletion air category. Furthermore, more emissions were transferred from air to soil and water, which increased the environmental impacts in the ecotoxicity and human health categories associated with soil and water. In terms of the human health risks of the oxy-fuel carbon dioxide capture in comparison to the post-combustion CO2 capture technology, the results showed that the oxy-fuel system performed better with regard to human health risks compared to the post-combustion system due to capturing more emissions. These health implications help provide support for improving the Estevan region air quality. In terms of cost analysis, capital cost, cost of electricity (COE), and cost of CO2 avoided (COA) were compared between the oxy-fuel and post-combustion CO2 capture technologies. The oxy-fuel combustion system showed significantly higher capital cost than that of the post-combustion system since the air separation unit (ASU) required a greater investment. In addition, the unit capital costs decreased with the size of the electrical generating plant. In terms of COE and COA, normally an oxy-fuel combustion system has lower COE and COA than that of a post-combustion system because of the amount of solvent used in the post-combustion system. However, in this study, when the smaller plant applied the oxy-fuel combustion CO2 capture technology, higher COE and COA were shown.
A Thesis Submitted to the Faculty of Graduate Studies and Research in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in Industrial Systems Engineering, University of Regina. xxiii, 349 p.