Abstract: The burning of fossil fuels, and the clearing of land for agriculture and urbanization, have released enough CO2 to the atmosphere to potentially alter the global patterns of weather and oceanic life. This creates two challenges, the first is to slow the release of fossil derived carbon dioxide from anthropogenic sources, and the second is to remove it from air if we are unable to reduce emissions enough to avoid reaching catastrophic atmospheric concentrations. One possible way to meet these two challenges is to design highly efficient CO2 capture processes. The design challenges for a large point source flue gas with 10-15% CO2 concentration are different from those for a distributed source air capture system operating at 400ppm CO2, yet both share important features of large gas flows and the need to maximize energy efficiency. In this talk I will describe the modeling, analysis and designs of solid sorbent systems for these two situations. The first is a rapid thermal swing adsorption (RTSA) system based on an innovative contactor design. The contactor uses hollow fibers which combines the advantages of high affinity and capacity sorbents with a scalable process technology. Specifically, the sorbent is embedded in silica particles that are themselves mixed with polymer dope and spun into a hollow fiber with dimensions of roughly 1micron outer diameter and 300 micron inner diameter. The inner bore of the fiber is made waterproof with a lumen layer of impervious polymer to create a channel down which water can be pumped. The polymer is very porous, with a volume fraction of 50-60%, and a high silica loading, which enables it both to have a high surface area for sorption and relatively fast mass transfer into the annulus. The organization of the sorbent into hollow fibers and their parallel arrangement in a module, rather than as a packed bed, dramatically reduces the pressure drop on the flue gas side of the module. It also allows for water to be circulated through the fiber bore which provides two advantages. Rapid cooling during adsorption, allowing the capacity of the sorbent to remain high, and rapid heating during desorption, allowing the rapid thermal swing of the process and hence much reduced process volume and therefore capital cost. The air capture system is a honeycomb structure, similar to a catalytic converter, where the sorbent is embedded in the walls of the channel. It requires a different adsorption isotherm, and heat generation and removal during adsorption is of less concern compared to pressure drop. I will present models of the cyclic operation and the important phenomena that govern the overall system behavior and the key parameters for design and operational optimization. I will show validation of the model using experimental data for small scale modules and the challenges associated with developing models for this process. I will present an overall system concept for integrating the RTSA process into a 550MW coal fired power plant and a preliminary technoeconomic analysis of the cost of CO2 capture using this process.
Biography: Dr. Matthew J Realff is a Professor of Chemical and Biomolecular Engineering at Georgia Tech and David Wang Senior Faculty Fellow. He has been at Georgia Tech since 1993, after completing his Bachelor’s degree at Imperial College London, a Ph.D. in chemical engineering at MIT in 1992. He was an National Science Foundation (NSF) program director from 2005-2007 in the division of Civil Mechanical and Manufacturing Innovation where he ran programs in environmentally benign design and service enterprise systems. In December 2013 he was appointed as the Associate Director of the Georgia Tech Strategic Energy Institute with responsibility for advanced materials and separations applications for energy systems and in 2014 appointed as an Associate Director of the Renewable Bioproducts Institute to help develop programs in chemicals and fuels.