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Integrated Carbon Capture and Conversion To Produce Syngas: Novel Process Design, Intensification, and Optimization

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journal contribution
posted on 12.07.2017, 00:00 by Shachit S. Iyer, Ishan Bajaj, Priyadarshini Balasubramanian, M. M. Faruque Hasan
An integrated, modular, and multifunctional process is conceptually designed, simulated, and optimized for direct utilization of CO2 from dilute flue gas to produce high-quality syngas, a precursor for many value-added chemicals and liquid transportation fuels. The process is intensified to simultaneously capture and convert CO2 using methane, natural gas, or excess fuel gas from the same plant, or using nearby unconventional methane from biogas or landfill gas. It is an integrated adsorption-purge-reaction system where CO2 is first adsorbed and then desorbed using methane-rich feed leading to a mixture suitable for dry-reforming. The merging of concentration-based CO2 desorption with the reactor feed premixing step eliminates the need for pressure or temperature swings and significantly reduces the energy penalty and cost of CO2 capture and utilization. The process is simulated at different conditions using a high-fidelity process model to elucidate the effects of key decision variables as well as the trade-offs and interactions between the capture and reforming sections. The technology is flexible to handle different feedstock compositions, and is amenable to both centralized and distributed production of syngas. A constrained grey-box optimization method is employed to achieve a maximum of 99.7% net overall CO2 utilization considering auxiliary emissions at a total cost ranging from $110–130 per ton of syngas. As much as 14.6% of the total CO2 input to the process comes “directly” from flue gas without additional cost for CO2 capture while maintaining about 91% overall CO2 utilization. The technology is also computationally found to be robust in terms of CO2 utilization and cost for different natural gas feeds with CO2 contamination as high as 60%. This can be attributed to the novel process intensification concept and the gray-box constrained optimization method presented in this work.