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| 222. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Influence of heat treatment on manganese ores as oxygen carriers
- 2019
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 87, s. 238-245
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Tidskriftsartikel (refereegranskat)abstract
- Manganese ores have been identified as promising oxygen carriers for chemical-looping processes with solid fuels, including combustion and gasification systems. Such Mn-based minerals are readily available globally and could thus be a cheap alternative to other naturally occurring oxygen carriers, such as ilmenite. These ores are usually highly heterogeneous, with varying phase composition, both on the inter-particle as well as intra-particle level. Further, manganese ores contain Mn in many forms and states, including combined or mixed oxides. The content of Fe, Al, Si, Mg and Ca can be high, but also vary significantly. Thus, it can be expected that there will be transformations of the chemical and physical structures during heating from room temperature to operational conditions. In fact, natural materials are often calcined in air prior to use in CLC systems, to avoid agglomeration and defluidization. In this work the effect of heat treatment is investigated for four different manganese ores that have widely different compositions. The mass losses during heat-up in a batch, fluidized-bed reactor and a thermogravimetric analyzer (TGA) were measured. In addition, the change in reactivity over 21 redox cycles with both methane and a syngas (CO/H2) was investigated for both heat treated and fresh ores. During the batch experiments, the defluidization tendency of the ores was investigated as well. The ores were characterized with X-ray diffraction (XRD) and ICP-SFMS. It was found that there was a release of CO2 and O2 from the ores during heat up in the batch experiment, likely originating from carbonates and thermodynamic unstable manganese oxides respectively. Also, significant mass losses were observed for the untreated ores in the TGA, and in addition to the release of CO2 and O2, a release of H2O was observed at lower temperatures. Reactivity was similar between heat treated and untreated ores, especially when considering the mass loss during heat-up. Still, the reactivity varied significantly among the different ores tested. Defluidization was observed only for one of the ores, when a blend of manganese ore and quartz sand was used as bed material during testing with syngas. However, no defluidization was observed during heat-up. In summary, depending upon the ore used, significant mass losses can be expected, which may need to be accounted for during operation with solid fuels.
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| 223. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Innovative oxygen carriers uplifting chemical-looping combustion,Chemical-looping combustion, natural gas, integrated project, oxygen carrier development
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 63, s. 113-130
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Konferensbidrag (refereegranskat)abstract
- This paper reports on the main results of the EU-financed project INNOCUOUS (Innovative Oxygen Carriers Uplifting Chemical-Looping Combustion). The project follows a series of successful projects with the aim of developing chemical-looping combustion (CLC) with gaseous fuels rich in methane. The project has included a wide range of experimental and modelling tasks, which included i) extensive screening of spray-dried and impregnated oxygen carriers, ii) production of impregnated and spray-dried oxygen carriers at >100 kg scale, iii) operation of several oxygen carriers at industrial conditions up to 120 kW scale and iv) techno-economic study of the next-scale CLC. One area of focus in the project has been the search for viable oxygen carriers which have low or no Ni. A large portfolio of interesting metal oxide systems has been found. Two oxygen carriers of CaMnxTiyMg1-x-yO3 were successfully produced in larger amounts by spray-drying and an oxygen carrier of Fe2O3/Al2O3 was produced in similar quantity using impregnation. The Ca-based material showed excellent behavior in a 10 kW and 120 kW unit, where complete combustion was achieved. With respect to the aim of replacing the bench-mark Ni-based material the project was thus very successful, as complete combustion has never been achieved in these units using Ni-based material.
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| 224. |
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| 225. |
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| 226. |
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| 227. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Oxygen carriers for chemical-looping combustion of solid fuels
- 2012
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Ingår i: Conference Proceedings. 2012 AIChE Annual Meeting, AIChE 2012, Pittsburgh, 28 October - 2 November 2012. - 9780816910731
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Konferensbidrag (refereegranskat)abstract
- The main economic advantage of CLC is likely realized for combustion of solid fuels such as coal, petroleum coke and biomass. In a process where the fuel and air reactor are designed as interconnected fluidized beds and where the solid fuel is well-mixed with the oxygen carrier particles there are two main mechanisms for char and volatile conversion: i) Normal CLC where the volatiles and gasification intermediates react directly with the oxygen carrier particles through a gas-solid reaction and ii) through CLOU or chemical-looping with oxygen uncoupling, where the oxygen carrier particles release gaseous oxygen which reacts with the solid fuel components through normal combustion. In addition, several oxygen carriers have been identified to have some CLOU properties, and for these so-called semi-CLOU materials, it could be speculated that the solids and volatiles react through both CLC and CLOU processes in parallel. The role of the oxygen carrier is thus different and depends upon the process which is used above. For route i) the oxygen carrier needs to convert the intermediate syngas components, mainly H2 and CO, as well as volatiles at a sufficient rate to achieve high gaseous yield to carbon dioxide. Here the oxygen carrier may have a limited effect on the char conversion. For route ii), or CLOU, the oxygen carrier needs to supply oxygen to the fuel at a sufficient rate to achieve a high rate of char and volatile conversion. For semi-CLOU materials, the role of the oxygen carrier material could depend upon a variety of factors, including the rate of oxygen release, and where it is released. The paper discusses the three processes described above and proposes a simple generic analytical model to evaluate the three types of processes above. From the model, quantitative reactivity criteria for oxygen carrier particles can be obtained. It is suggested that it is likely a substantial advantage to utilize oxygen carriers with CLOU properties to process solid fuels, both with respect to char and volatile components. The advantage of semi-CLOU materials is less clear.
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