Chemical Looping Combustion of a Biomass Char in Fe2O3-, CuO-, and SrFeO3−δ-Based Oxygen Carriers
| Autor: | K. Y. Kwong, A. R. P. Harrison, J. C. Gebers, J. S. Dennis, E. J. Marek |
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| Přispěvatelé: | Marek, EJ [0000-0002-8318-2131], Apollo - University of Cambridge Repository |
| Rok vydání: | 2022 |
| Předmět: | |
| Zdroj: | Energy & Fuels. 36:9437-9449 |
| ISSN: | 1520-5029 0887-0624 |
| Popis: | This research focuses on the combustion of biomass char in fluidised beds of various particulate solids, which, under the conditions of the reaction, were either inert or capable of supplying oxygen to reactions. The latter were termed oxygen carriers. The solids used were SiO2, as an inert material, and three oxygen carriers: (1) Fe2O3 prepared from a natural pyrite ore, (2) CuO supported on mayenite, and (3) SrFeO3-δ strontium ferrite perovskite. Combustion experiments were undertaken by introducing a sample of partially-devolatilised biomass (commercial ‘bio-char’) to a hot bubbling bed (i.d. 30 mm), fluidised by a mixture of oxygen and nitrogen, then analysing the composition of the off-gas and the burnout time of the char sample. In the temperature range investigated in this work (1023 K to 1168 K), CuO and SrFeO3-δ, but not Fe2O3, thermally decomposed, releasing gaseous O2 (so-called ‘chemical looping oxygen uncoupling’, CLOU). Hence, to make the combustion conditions comparable with various oxygen carriers, all experiments were performed using a fluidising gas with a fixed partial pressure of O2, pO2, ~ 0.015 bar. Despite the same nominal pO2, the occurrence of the oxygen uncoupling reaction increased the total net amount of O2(g) available in the process, affecting external mass transfer of O2 to the char particle and accelerating its rate of combustion. The time needed to combust totally 0.1 g of biochar particles in different beds at 1168 K followed the trend CuO < SrFeO3-δ < Fe2O3 ≈ silica sand. The difference in the performance of CuO and SrFeO3-δ was ascribed to the lower oxygen availability via CLOU in the perovskite compared with the copper oxide. Interestingly, combustion in the bed of Fe2O3 particles took a similar amount of time as combustion in the inert bed of SiO2 despite iron oxide playing an active role in the process. The finding is explained by Fe2O3 reacting with the CO produced from incomplete char combustion, which results in the reduced oxide competing with char for O2(g) and effectively decreasing the local pO2. |
| Databáze: | OpenAIRE |
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