| 1. |
- Adanez-Rubio, Inaki, et al.
(författare)
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Cu-Mn oxygen carrier with improved mechanical resistance: Analyzing performance under CLC and CLOU environments
- 2021
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 217
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Tidskriftsartikel (refereegranskat)abstract
- Chemical Looping Combustion process allows combustion of gaseous, liquid or solid fuels with CO capture. The oxygen necessary for combustion can be supplied using lattice oxygen (CLC) or oxygen uncoupling (CLOU) mechanisms. The present work studies the effects of kaolin addition on Cu–Mn oxygen carrier behavior for CLC and CLOU processes. Cu–Mn oxygen carrier was prepared by granulation with a composition: 27.2 wt% CuO, 52.8 wt% Mn O and 20 wt% kaolin. Oxygen release rates and fluidization behavior were analyzed by TGA and batch fluidized bed reactor. The oxygen carrier was studied for CH and synthetic biogas combustion in a 500 W CLC continuous unit for 50 h of combustion at temperatures up to 930 °C. No agglomeration problems were observed. Results found during biogas combustion were similar to methane combustion. The addition of 20 wt% kaolin changed the mixed oxide chemical composition generating Cu Mn O and improved significantly the oxygen carrier mechanical resistance, increasing the extrapolated lifetime to 19,000 h, 3.6 times over the value found for any Cu based oxygen carrier in CLC. However, the oxygen carrier reactivity had an important decrease with respect to a similar oxygen carrier without kaolin addition, whose fraction in oxygen carrier must be optimized. 2 3 4 4 th 1.2 1.8 4
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| 2. |
- Adanez-Rubio, Inaki, et al.
(författare)
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Development of new Mn-based oxygen carriers using MgO and SiO 2 as supports for Chemical Looping with Oxygen Uncoupling (CLOU)
- 2023
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 337
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Tidskriftsartikel (refereegranskat)abstract
- Chemical Looping with Oxygen Uncoupling (CLOU) is a technological adaptation of CLC, most applicable for the combustion of solid fuels. In the CLOU process, an oxygen carrier in the fuel reactor, avoiding the direct contact of the fuel with the air, releases the oxygen needed for the fuel combustion. The oxygen carrier is regenerated with air in the interconnected air reactor. The present work explores the behavior of the system Mn/Mg/Si as oxygen carriers for chemical-looping with oxygen uncoupling (CLOU). Six different mixed oxides of the system Mn/Mg/Si were investigated for the CLC/CLOU process. Materials were prepared by spray drying with different metal ratios used in the investigation. The properties of interest for the viability of these materials are the lattice oxygen supply for CLC and the gaseous oxygen release for CLOU, properties that were explored in a TGA. Further, the fluidization behavior and the mechanical resistance were investigated in a batch fluidized bed reactor. In the TGA it was observed that the most reactive oxygen carriers for the CLOU process were materials without Si in the structure, more specifically M24Mg76 and M48Mg51 which had a molar ratio of Mn/Mg of 0.17 and 0.51 respectively. It was also observed that for the oxygen carriers with Si in the composition, the regeneration was very poor. Oxygen carriers M24Mg76 and M48Mg51 were selected for batch fluidized bed reactor testing showing good behavior with respect to the CLOU reactivity, and mechanical stability. One of the materials, the M24Mg76 showed activation during the experiments in the batch fluidized bed reactor experiments, increasing the oxygen transport capacity by 20 % during the experiment. However, 10 vol% of O2 was needed to regenerate both oxygen carriers at 850 °C. No agglomeration tendencies were seen, and the attrition rate was low, obtaining high-extrapolated lifetime values. The fact that highly reactive oxygen carriers can be made with cheap and highly available metals oxides, i.e. Mn and Mg, makes this system very promising and a possible alternative to benchmark Cu-based CLOU materials.
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| 3. |
- Adanez-Rubio, Inaki, et al.
(författare)
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Use of a high-entropy oxide as an oxygen carrier for chemical looping
- 2024
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Ingår i: Energy. - 0360-5442 .- 1873-6785. ; 298
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Tidskriftsartikel (refereegranskat)abstract
- One mixed oxide with 5 cations in equimolar proportions in the sublattice, to fulfil high-entropy oxide (HEO) criteria, has been developed and investigated as oxygen carrier for chemical looping combustion processes. As far as we know, nobody has explored this class of material for chemical looping combustion. Material is prepared by direct mixing of five metal oxides (CuO, Mn2O3, Fe2O3, TiO2, MgO), followed by calcination at 1000, 1100 and 1200 °C for 6 h in air. XRD characterization provides strong evidence that the synthesized oxygen carriers possess the hallmark properties of HEO, and SEM-EDX analysis shows an overall homogeneous metal distribution. Materials have one main cubic phase with the empirical formula MnCuMgFeTiO7, dominating under all conditions. One of the key objectives of this study is achieved, reduce chemical stress during redox cycles. Oxygen transfer capability is investigated by thermogravimetric analysis and batch fluidized bed reactor experiments for different fuels and atmospheres. Mass-based oxygen transport capacities for lattice oxygen and oxygen uncoupling are around 5.5 wt% and 1.1 wt%, respectively. This work opens up a new dimension for the future preparation of oxygen carriers for chemical looping processes, since the vast compositional space of HEO provides opportunities to tune both chemical and physical characteristics.
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| 4. |
- Adanez-Rubio, Inaki, et al.
(författare)
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Investigation of Combined Supports for Cu-based Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:7, s. 3918-3927
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Tidskriftsartikel (refereegranskat)abstract
- The chemical-looping with oxygen uncoupling (CLOU) process is a novel solution for efficient combustion with inherent separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor. In the fuel reactor, the metal oxide releases gas phase oxygen which oxidizes the fuel through normal combustion. In this study, Cu-based oxygen carrier materials that combine different supports of MgAl2O4, TiO2 and SiO2 are prepared and characterized with the objective of obtaining highly reactive and attrition resistant particles. The oxygen carrier particles were produced by spray-drying and were calcined at different temperatures ranging from 950 to 1030oC for 4 h. The chemical-looping performance of the oxygen carriers was examined in a batch fluidized-bed reactor in the temperature range of 900-950oC under alternating reducing and oxidizing conditions. The mechanical stability of the oxygen carriers was tested in a jet-cup attrition rig. All of the oxygen carriers showed oxygen uncoupling behaviour with oxygen concentrations close to equilibrium. During reactivity tests with methane, oxygen carriers with lower mechanical stability showed higher reactivity, yielding almost complete fuel conversion. Oxygen carrier materials based on support mixtures of MgAl2O4/TiO2, MgAl2O4/SiO2 and TiO2/SiO2 showed a combination of high mechanical stability, low attrition rates, good reactivity with methane and oxygen uncoupling behaviour.
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| 5. |
- Stanicic, Ivana, 1994, et al.
(författare)
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Investigating the Interaction between Ilmenite and Zinc for Chemical Looping
- 2023
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Ingår i: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 37:11, s. 7856-7870
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Tidskriftsartikel (refereegranskat)abstract
- The iron and titanium oxide ilmenite is a benchmark oxygen carrier for chemical looping combustion (CLC) and oxygen carrier-aided combustion (OCAC). Both of them are combustion technologies for biomass and waste fuels with lower emissions and low costs for carbon capture. Here, the interaction between the ash component zinc and oxygen carrier ilmenite is studied in a two-staged vertical tube reactor. Three types of ilmenites─Norwegian rock ilmenite, synthesized ilmenite, and ilmenite extracted after 200 h of OCAC in a full-scale fluidized bed unit─were exposed to gas-phase Zn and ZnCl2. Following the exposure, samples were analyzed concerning morphology, chemical distribution, composition, and crystalline phases. The observations were complemented with thermodynamic equilibrium calculations. It is observed that the iron-rich layer formed on the external surface of rock ilmenite after activation promotes the reaction with both gaseous zinc compounds, with zinc ferrite formed in the external Fe-rich layer. In contrast, ilmenite with no segregation of Fe and Ti showed to interact less with zinc species. Metallic Zn penetrated the particles, while the interaction depth was shallow with ZnCl2 for all investigated ilmenite oxygen carriers. The gaseous conditions, particle ash layer composition, and iron availability are shown to play an important role in the interaction between zinc compounds and ilmenite particles. Based on these results, interaction mechanisms for Zn and ZnCl2 are proposed. This interaction could have environmental implications for the toxicity of ash streams from waste combustion in addition to possibilities for Zn recycling.
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