CO2 capture from industrial plants for the production of marketable compounds.

Abstract

Carbon Dioxide Reduction (CO2R) is gaining attention as a way to reduce carbon in the environment, especially by turning industrial CO2 emissions into valuable chemicals and fuels. However, the methods to achieve this are still in early development stages. Moreover, there is a lack of process design and techno-economic feasibility studies to assess competitiveness, select the most promising alternatives, and identify research and development gaps. The main goals of this thesis are to create a mathematical model for the CO2R electrochemical cell, study the effects of different operating conditions on the cell’s performance, and design a complete process for turning CO2 into valuable chemicals and fuels. An electrochemical cell model is developed in MATLAB, which incorporates fundamental phenomena inside each part of the cell, such as species and charge transport, charge conservation, and electrochemical reactions. Aspen Plus is then used to study the overall process, including the reaction and the separation stages. Two case studies are presented: one producing methanol, CO, and H2, and the other producing a variety of chemicals including ethanol and ethylene. Detailed models and simulations were performed for each case, leading to a thorough economic analysis. The economic analysis shows a large difference in the minimum estimated selling price between the two case studies, with the production of mixed chemicals being more economical. A main challenge identified is the low concentration of products at the end of the reaction step, which increases the energy needed for separation. The study also finds that the applied voltage plays a crucial role in influencing both product production rates and selectivity in the CO2R process. The flexible models developed in this research can serve as valuable tools for testing different electrolyzer operating conditions, catalysts, and reactions, all of which have an impact on subsequent separation costs. In summary, this study represents a valuable resource for the assessment of CO2R technologies.