Summary Development of a cost‐effective oxygen carrier (OC) for chemical looping combustion (CLC) technology remains an important task to be accomplished. Bauxite waste red mud from the United States has shown promise as an OC, but bauxite waste from China has not been evaluated extensively although huge quantities of it exists. In comparison, the Chinese bauxite waste usually contains low Fe2O3 and high Na concentration. Hence, the purpose of this study was to evaluate a typical red mud (from Zibo, China) with low Fe2O3/Na mass ratio for its potential as a cost‐effective OC during CLC processing. Parametric reactor testing was accomplished with a focus on OC reactivity during CLC, and evaluations were accomplished of morphologies, elemental concentrations, and mechanical strengths before and after reaction testing; special attention was paid to the stability of Na. These results showed that Zibo red mud (a) used as an OC during CLC had satisfactory reactivity particularly after pre‐calcination at 1250°C, (b) had high contents of Na that were stable and uniformly distributed during reaction testing and formed NaAlSiO4 during sample calcination and reaction testing, and (c) showed high mechanical strengths that were similar to those of other oxygen carriers. Considering that huge amounts of this inexpensive Zibo red mud are located within areas near aluminum processing plants, it may become a promising material as an OC for CLC processing.
Current state‐of‐the‐art NH3‐SCR technology based on vanadium catalysts suffers problems associated with NH3 slip and poisoning of the catalyst and blockage of heat recovery steam generators (HRSG). If environmentally‐friendly catalysts capable of efficient operation at lower temperatures could be developed that used a reductant other than NH3, the issues with current state‐of‐the‐art SCR could be significantly lessened. Hence, in this study, activated carbon (AC) supported copper oxide‐based catalysts for SCR while using C2H4 as a reductant was discussed. Reaction testing of catalysts demonstrated high initial NO conversion with steeply declining activity over 2 h of testing when C2H4 was used as the reductant; in comparison, with the same catalyst and NH3 as the reductant, stable, long‐term NO conversion was achieved, but at a lower rate than the initial reactivity with C2H4. As a consequence, catalyst characterization studies were performed to assess deactivation mechanisms when C2H4 was the reductant. These studies included x‐ray diffraction, BET surface area and porosity, temperature programmed reduction, scanning electron microscopy, Raman spectroscopy and x‐ray photoelectron spectroscopy of both fresh and deactivated catalysts. The analytical results showed the surface area and porosity of the catalyst remained unchanged and the initially highly‐dispersed Cu species became agglomerated and more crystalline during reaction testing. Furthermore, carbon black was also detected on the catalyst surface after testing, presumably formed during the decomposition of C2H4. Both agglomeration of the active Cu species and blockage by carbon deposits would decrease the availability of active sites and lead to decreased catalytic activity.
Summary Tremendous amounts of organic residue from manufacturing herbal medicines and inorganic red mud waste from mining bauxite ores are landfilled each year in China. To study the potential for their beneficial co‐use, chemical looping gasification (CLG) was tested in which the organic residue was used as the fuel and the red mud was the oxygen carrier that is needed for CLG. Parametric testing was performed using a thermo‐gravimetric analyzer and a bench‐scale fluidized bed reactor to optimize CLG operations that could maximum syngas production, enrich H2 concentrations and obtain effective conversion of the residue. Physical and chemical characterization of the organic residue and red mud before and after CLG testing showed that some filamentous ash from the organic residue remained on the surface after testing, and potassium from the organic residue migrated onto the surface of the oxygen carrier. The characterization and testing results suggested that CLG may be an advantageous technology to effectively convert an organic waste into syngas and an inorganic waste into a usable product, thereby establishing an approach for beneficial waste resource utilization.
Chemical looping combustion (CLC) technology is a promising CO 2 capture technology with advantages inherent to CO 2 separation and energy gradient utilization. The oxygen carrier itself is considered one of the most important parts of the CLC technology that provides fuel conversion and system economy. Iron-based oxygen carriers are promising candidates for CLC; doping them with Bi 2 O 3 may further improve their reactivities through oxygen vacancy formation that is promoted by high anion conductivity and reducibility. Hence, in this study, the effects of Bi 2 O 3 concentrations and calcination temperatures on the reactivity of iron-based oxygen carriers were parametrically investigated using TGA and bench-scale CLC experiments. Additionally, the oxygen carriers were analytically characterized before and after CLC testing using X-ray diffraction, scanning electron microscopy/energy dispersive spectrometry, and Brunauer−Emmett−Teller surface area/porosity measurements. The analytic results showed that addition of Bi 2 O 3 did not affect surface areas to any significant extent; however, it did increase average pore sizes. The CLC data showed that Bi 2 O 3 addition improved the oxygen carriers' reactivities by decreasing the reduction activation energy and caused BiFeO 3 solid solutions to form which, because of the introduction of more labile lattice oxygen transfer, may increase surface reactivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2025 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.