Bench-scale Development of a Transformational Switchable-hydrophilicity Solvent-enabled Absorption Process for Energy-efficient CO2 Capture and Fixation

Thermisoln LLC, in partnership with the University of Kentucky (UK), is working together to develop a switchable-hydrophilicity solvent (SHS) which can energy-efficiently capture and fixate CO2 from point sources burning fossil fuels, and meanwhile enables the upcycling of gypsum wastes and the cogeneration of a value-added, carbon-free, non-volatile soil fertilizer. Traditional amine scrubbing solvents are more effective for CO2 capture as aqueous solutions due to reduced working viscosity and consequently enhanced CO2 mass transfer rate. However, the regeneration of rich solvents poses a grand challenge in the presence of water cosolvent, and is commonly regarded as an energy-intensive process. To circumvent this issue, a smart SHS is proposed in Phase I that can responsively switch from hydrophobicity to hydrophilicity in nature with the aid of a CO2 trigger. While operating, the intrinsic hydrophobicity of the original SHS will spontaneously create phase separation between the excess or regenerated SHS and associated aqueous phase, which means that complex separation processes such as traditional energy-intensive distillations are unnecessary to recover the SHS from relevant aqueous phase. In addition, to further minimize energy penalty, another innovative strategy is herein proposed to regenerate the spent SHS roughly at room temperature by using a secondary solvent instead of commonly adopted high-temperature stripping routes. This will significantly reduce evaporative loss of solvent, its thermal and oxidative degradation, and equipment corrosion. In the proposed CO2 capture process, besides the direct capture of CO2 off-gas, part of the CO2 present in flue gas is chemically immobilized by mineral carbonation to form limestone that could be used as a sorbent for DeSOx from coal-fired power plants. The facile availability of adequate limestone sorbents on site will promote the direct burning of cheap and abundant high-sulfur coals or natural gases. The utilization of these low-grade fossil fuels can in turn make more profits for the power plants and reduce the costs of power generation. Alternatively, the limestone byproduct can be safely and permanently sequestered in depleted oil/natural gas reservoirs or ore wells deep underground as another means of carbon fixation. Furthermore, the coproduction of a widely used agricultural fertilizer is favorable for healthier and faster plant growth, thereby promoting more effective biological CO2 capture and fixation. The combined process, CO2 capture coupled with beneficial use of the process byproducts, will reach the DOE's cost objective of ~$30/ton of CO2 captured. The recent dramatic increase in the cost of fertilizers will make the proposed process even more cost-effective. During Phase I, we will demonstrate the technical viability by optimizing the parameters of the SHS-based CO2 capture technology, and then investigate in depth how CO2 can be efficiently removed from the flue gas in different power plants. Furthermore, the co-benefits from this CO2 capture process will be extensively exploited to help reduce the overall energy consumption of this technology. As soon as the feasibility is identified in Phase I, the whole process will be systematically optimized in Phase II to further improve process efficiencies. We will also transition the capture process from a bench-top scale in Phase I to a larger pilot scale in Phase II by collaborating with the industrial partners identified during the Phase I effort. The end goal will be an affordable and energy-efficient CO2 capture process ready to enter into the marketplace as more competitive alternatives to existing CO2 capture technologies.