@article{cai_krzystowczyk_braunberger_li_neal_2024, title={Techno-economic analysis of chemical looping air separation using a perovskite oxide sorbent}, volume={132}, ISSN={["1878-0148"]}, DOI={10.1016/j.ijggc.2024.104070}, abstractNote={Air separation is a costly process that is difficult to operate efficiently at small scales. Chemical looping air separation (CLAS) is a promising process for small-footprint oxygen production with low energy consumption. CLAS has potential applications in a promising carbon capture technology, oxyfuel combustion (oxy-combustion). In oxy-combustion, high-concentration oxygen from an air separation unit is used to combust a carbonaceous fuel into an easily-separated, nitrogen-free exhaust stream. In this paper, a techno-economic analysis was conducted in conjunction with reactor modeling to determine the cost of oxygen from a CLAS plant as a modular air separation unit for a 5 MW thermal coal-based oxy-combustion plant. The effects of different length-to-diameter ratios were investigated. The cost of oxygen from CLAS was projected to be as low as $65/ton O2 under baseline assumptions, which was much lower than typical current delivered oxygen at similar scales. Although higher in capital cost, CLAS also compares favorably to pressure swing adsorption, which has much larger parasitic energy losses. Further analysis indicates that air and steam demand and the sorbent reactor L/D ratio are key to optimizing the costs.}, journal={INTERNATIONAL JOURNAL OF GREENHOUSE GAS CONTROL}, author={Cai, Runxia and Krzystowczyk, Emily and Braunberger, Beau and Li, Fanxing and Neal, Luke}, year={2024}, month={Feb} }
 @article{cai_bektas_wang_mcclintock_teague_yang_li_2023, title={Accelerated Perovskite Oxide Development for Thermochemical Energy Storage by a High-Throughput Combinatorial Approach}, volume={3}, ISSN={["1614-6840"]}, url={https://doi.org/10.1002/aenm.202203833}, DOI={10.1002/aenm.202203833}, abstractNote={Abstract}, journal={ADVANCED ENERGY MATERIALS}, author={Cai, Runxia and Bektas, Hilal and Wang, Xijun and McClintock, Kyle and Teague, Lauren and Yang, Kunran and Li, Fanxing}, year={2023}, month={Mar} }
 @article{li_cai_ahn_lu_jung_jeon_zhu_2023, title={Hydrodynamics in the transport zone of a large-scale circulating fluidized bed boiler}, volume={414}, ISSN={["1873-328X"]}, DOI={10.1016/j.powtec.2022.118099}, abstractNote={To investigate the hydrodynamics in large-scale CFB boilers, the pressure drops in the transport zone of a 550-MWe CFB boiler were measured by conducting five field tests. The circulating rates Gs were calculated based on the pressure drop in the transport zone and then compared with the estimations via the correlations of the elutriation constant in single-particle elutriation theory and those of the saturation-carrying capacity in fast fluidization theory. The Colakyan & Levenspiel correlation of elutriation constant exhibited a good agreement with the experiments within ±14.02% error range. It's reasonable to use it for calculating Gs in large-scale CFB boilers because of its wide experimental conditions. The flow regime remained uncertain due to the discrepancies in the saturation-carrying capacity estimated by different correlations. The effect of riser diameter on Gs was discussed, including the dimension of Dt, ind, beyond which the circulating rate was suggested to be independent of the riser diameter.}, journal={POWDER TECHNOLOGY}, author={Li, Dongfang and Cai, Runxia and Ahn, Seokgi and Lu, Xiaofeng and Jung, Sungmook and Jeon, Chung-Hwan and Zhu, Xing}, year={2023}, month={Jan} }
 @article{cai_brody_tian_neal_bose_li_2023, title={Numerical modeling of chemical looping oxidative dehydrogenation of ethane in parallel packed beds}, volume={469}, ISSN={["1873-3212"]}, url={https://doi.org/10.1016/j.cej.2023.143930}, DOI={10.1016/j.cej.2023.143930}, abstractNote={Chemical looping oxidative dehydrogenation (CL-ODH) of ethane has the potential to be a highly efficient alternative to steam cracking for ethylene production. Accurate reactor modeling is of critical importance to efficiently scale up and optimize this new technology. This study reports a one-dimensional, heterogeneous packed bed model to simulate the CL-ODH of ethane to ethylene with a Na2MoO4-promoted CaTi0.1Mn0.9O3 redox catalyst. The overall reaction kinetics was well-described by coupling the gas-phase steam cracking of ethane with the reduction kinetics of the redox catalyst by H2 and C2H4. The impact of H2 on the formation rate of CO2 byproduct from C2H4 conversion was also thoroughly investigated to validate the applicability of the kinetic model under operational environments. The temperature variation within the different CL-ODH steps and the temperature distribution along the bed were also carefully considered. The accuracy of the model was validated by experiments conducted in a large lab-scale packed bed reactor (200 g catalyst loading), with an average deviation of 2.8% in terms of ethane conversion and ethylene yield. The model was subsequently used to optimize the operating parameters of the CL-ODH reactor, indicating that up to 63.7% single-pass C2 + olefin yield can be achieved with the current redox catalyst bed whereas further optimization of the redox catalyst to inhibit C2H4 activation can result in 69.4% single-pass C2 + yield while maintaining low CO2 selectivity.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Cai, Runxia and Brody, Leo and Tian, Yuan and Neal, Luke and Bose, Arnab and Li, Fanxing}, year={2023}, month={Aug} }
 @article{brody_rukh_cai_bosari_schomaecker_li_2023, title={Sorption-enhanced steam reforming of toluene using multifunctional perovskite phase transition sorbents in a chemical looping scheme}, volume={5}, ISSN={["2515-7655"]}, url={https://doi.org/10.1088/2515-7655/acdbe9}, DOI={10.1088/2515-7655/acdbe9}, abstractNote={Abstract}, number={3}, journal={JOURNAL OF PHYSICS-ENERGY}, author={Brody, Leo and Rukh, Mahe and Cai, Runxia and Bosari, Azin Saberi and Schomaecker, Reinhard and Li, Fanxing}, year={2023}, month={Jul} }
 @article{cai_dou_krzystowczyk_richard_li_2022, title={Chemical looping air separation with Sr0.8Ca0.2Fe0.9Co0.1O3-delta perovskite sorbent: Packed bed modeling, verification, and optimization}, volume={429}, ISSN={["1873-3212"]}, DOI={10.1016/j.cej.2021.132370}, abstractNote={Chemical looping air separation (CLAS) represents a promising approach for efficient O2 production from the air. The present study aims at optimizing the absorber/desorber operations and the separation process with extensive experimental validation. Specifically, a one-dimensional packed bed model was developed to investigate the CLAS operation with a Sr0.8Ca0.2Fe0.9Co0.1O3-δ perovskite sorbent. The redox thermodynamics of perovskite sorbent was measured by TGA and then incorporated into a linear driving force model to describe the O2 absorption and desorption rates. Both 4-step and 5-step air separation cycle configurations, with various cyclic structures, were performed in a subpilot-scale packed bed. The model predicted O2 purity and productivity were consistent with experimental results, supporting its accuracy and applicability. Parametric analysis and multi-objective optimization were further carried out to assess the performance of CLAS. Both O2 purity and recovery increased monotonically with the cycle time, airflow rate, steam flow rate, and absorption pressure. Meanwhile, optimal O2 productivity and power consumption can only be achieved by specific combinations of these parameters. The optimized results showed that CLAS can be highly competitive when compared to conventional pressure swing adsorption (PSA) or cryogenic distillation. The 5-step cycle configuration achieved a minimum power consumption of 118 kW·h for producing 1 ton O2 with ≥ 95% purity. The maximum O2 productivity reached 0.0932 gO2/(gsorbent·h) with 390 kW·h/ton O2 of energy consumption (95% pure). The optimization results also indicate that CLAS can potentially be more efficient than cryogenic distillation even when the required O2 purity is above 99%.}, journal={CHEMICAL ENGINEERING JOURNAL}, author={Cai, Runxia and Dou, Jian and Krzystowczyk, Emily and Richard, Anthony and Li, Fanxing}, year={2022}, month={Feb} }
 @article{wang_gao_krzystowczyk_iftikhar_dou_cai_wang_ruan_ye_li_2022, title={High-throughput oxygen chemical potential engineering of perovskite oxides for chemical looping applications}, volume={2}, ISSN={["1754-5706"]}, url={https://doi.org/10.1039/D1EE02889H}, DOI={10.1039/d1ee02889h}, abstractNote={Integrating DFT, machine learning and experimental verifications, a high-throughput screening scheme is performed to rationally engineer the redox properties of SrFeO3−δ based perovskites for chemical looping applications.}, number={4}, journal={ENERGY & ENVIRONMENTAL SCIENCE}, publisher={Royal Society of Chemistry (RSC)}, author={Wang, Xijun and Gao, Yunfei and Krzystowczyk, Emily and Iftikhar, Sherafghan and Dou, Jian and Cai, Runxia and Wang, Haiying and Ruan, Chongyan and Ye, Sheng and Li, Fanxing}, year={2022}, month={Feb} }
 @article{brody_cai_thornton_liu_yu_li_2022, title={Perovskite-Based Phase Transition Sorbents for Sorption-Enhanced Oxidative Steam Reforming of Glycerol}, volume={10}, ISSN={["2168-0485"]}, DOI={10.1021/acssuschemeng.2c01323}, abstractNote={Sorption-enhanced steam reforming represents an efficient strategy to produce concentrated hydrogen from superfluous carbonaceous feedstocks. However, commonly used CaO-based sorbents are prone to sintering, leading to a rapid loss in CO2 sorption capacity and activity under repeated reaction cycles. Herein, we report perovskite-based phase transition sorbents (PTSs) capable of avoiding sintering and retaining both catalytic activity and sorption capacity. Specifically, A- and B-site doped SrFeO3−δ, that is, Sr1–xCaxFe1–yNiyO3−δ (SCFN), were evaluated as PTSs for the sorption-enhanced steam reforming of glycerol. Packed bed reactor experiments were performed in conjunction with redox, bulk, surface, and morphology characterizations to evaluate SCFN’s performance and the underlying phase transition scheme. These characterizations revealed that reduced oxides from the A-site of the PTS (SrO, CaO) are carbonated during the reforming step before reversibly undergoing decarbonation at a higher temperature under an oxidizing environment. This study demonstrates that SCFN is a trifunctional material capable of (i) catalyzing the reforming of glycerol, (ii) absorbing CO2 in situ, and (iii) reversibly releasing oxygen from lattice sites to enhance glycerol conversion. While all of the screened compositions achieved >87 vol % pre-breakthrough H2 purities, SCFN-4691 (Sr0.4Ca0.6Fe0.9Ni0.1O3−δ) and SCFN-5591 (Sr0.5Ca0.5Fe0.9Ni0.1O3−δ) showed particularly high (95.6–97.3%) H2 purities with stable CO2 sorption capacities.}, number={19}, journal={ACS SUSTAINABLE CHEMISTRY & ENGINEERING}, author={Brody, Leo and Cai, Runxia and Thornton, Alajia and Liu, Junchen and Yu, Hao and Li, Fanxing}, year={2022}, month={May}, pages={6434–6445} }
 @article{wang_gao_wang_cai_chung_iftikhar_wang_li_2021, title={Liquid Metal Shell as an Effective Iron Oxide Modifier for Redox-Based Hydrogen Production at Intermediate Temperatures}, volume={11}, ISSN={["2155-5435"]}, url={https://doi.org/10.1021/acscatal.1c02102}, DOI={10.1021/acscatal.1c02102}, abstractNote={This study reports molten metals (bismuth, indium, and tin) as effective modifiers for iron-based redox catalysts in the context of chemical looping-based hydrogen production at intermediate temperatures (450–650 °C) from low-calorific-value waste gas (e.g., blast furnace gas). The effects of the bismuth promoter on both the surface and bulk properties of iron oxides were studied in detail. Transmission electron microscopy and energy-dispersive spectroscopy (TEM-EDS), low-energy ion scattering (LEIS), Raman spectroscopy, and 18O2 exchange experiment revealed that the bismuth modifier forms an overlayer covering the bulk iron (oxides), leading to better anti-coking properties compared to reference La0.8Sr0.2FeO3- and Ce0.9Gd0.1O2-supported iron oxides. The Bi-modified sample also exhibited improved anti-sintering properties and high redox activity, resulting in a 4-fold increase in oxygen capacity compared to pristine Fe2O3 (28.9 vs 6.4 wt %) under a cyclic redox reaction at 550 °C. Meanwhile, a small amount of bismuth is doped into the iron oxide structure to effectively enhance its redox properties by lowering the oxygen vacancy formation energy (from 3.1 to 2.1 eV) and the energy barrier for vacancy migration, as confirmed by the experimental results and density functional theory (DFT) calculations. Reactive testing indicates that Bi-modified redox catalysts are highly active to convert low-calorific-value waste gases such as blast furnace gas. Our study also indicates that this strategy can be generalized to low-melting-point metals such as Bi, In, and Sn for iron oxide modification in chemical looping processes.}, number={16}, journal={ACS CATALYSIS}, publisher={American Chemical Society (ACS)}, author={Wang, Iwei and Gao, Yunfei and Wang, Xijun and Cai, Runxia and Chung, Chingchang and Iftikhar, Sherafghan and Wang, Wei and Li, Fanxing}, year={2021}, month={Aug}, pages={10228–10238} }