UNS: Collaborative Research: Multiple-Scale Investigation of Chemical Looping with Oxygen Carrier Uncoupling

Collaborative Proposals

#1511818 / P.I.: Tian, Hanjiang

#1510900 / P.I.: Li, Fanxing

This research is expected to provide fundamental knowledge and scientific foundation for addressing CO2 capture and sequestration (CCS) from coal combustion, one of the most crucial areas of environmental sustainability. Among various CCS technologies, CLOU, a CLC scheme optimized for solid-fuel combustion (e.g., coal), represents one of the most promising options. Enabled by metal-oxide-based oxygen carriers capable of oxygen release and uptake under varying oxygen partial pressures, CLOU indirectly converts coal into separate streams of sequestration-ready CO2- and N2-rich flue gas via cyclic reactions. Consequently, the energy penalty associated with CO2 separation is inherently avoided. Compared to oxy-fuel combustion, the energy-intensive cryogenic oxygen separation is replaced by facile oxygen transfer enabled by the oxygen carrier, leading to significant improvement of carbon-capture efficiency. To date, most research in this area follows a trial-and-error approach due to lack of scientific understanding on the mechanism of coal-oxygen carrier interaction. Such an inefficient approach not only introduces potential uncertainties in technology and economics, but it also limits the progress of the development and implementation of CLC. The research is driven by the urgent needs for developing new scientific understanding and innovative tools and methodologies to investigate coal-oxygen carrier interaction and kinetics, oxygen-carrier optimization, and reactor and process simulations. The research will establish a solid theoretical groundwork for CLOU development from atomic level to reactor and process scales. These fundamental studies also are expected to lead to exciting discovery of novel catalytic-system and reactor configurations benefiting other research areas such as novel schemes for oxygen production, biomass combustion, coal/biomass gasification, and SOx/NOx emission control.

Chemical Looping Combustion with Oxygen Carrier Uncoupling, a.k.a. CLOU, represents a unique combustion scheme that is directly related yet notably different from conventional combustion processes. It allows efficient fossil fuel combustion with minimal energy penalty for CO2 separation. Initiated by six leading U.S./Chinese research groups in the areas of both conventional and Chemical Looping Combustion (CLC), this multidisciplinary team brings together top chemical engineers, thermal engineers, mechanical engineers, and catalysis scientists to answer critical, interrelated scientific questions in combustion kinetics, surface reactions, oxygen-carrier development, thermal engineering, and reactor/process modeling, spanning from atomic level to reactor and process scales. Fundamental findings obtained from the proposed research are expected to significantly accelerate the development and deployment of CLOU for efficient coal combustion with integrated CO2 capture. The fundamental research focuses on four aspects: 1) lattice oxygen diffusion, surface reaction, and gas-phase combustion kinetics in a metal-oxide-assisted char/volatile oxidation scheme; 2) oxygen-carrier interactions with coal ash and impurities; 3) oxygen-carrier stability and performance evaluation in circulating fluidized bed CLC reactors, and 4) reactor and process modeling.

These collaborative grants are co-funded by the Global Venture Fund (GVF) of NSF's International Science and Engineering section (ISE) and the CBET/ENG Combustion and Fire and Environmental Sustainability programs.