| 1. |
- Linderholm, Carl Johan, 1976, et al.
(author)
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Chemical-looping combustion of solid fuel in a 100 kW unit using sintered manganese ore as oxygen carrier
- 2017
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In: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 65, s. 170-181
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Journal article (peer-reviewed)abstract
- Carbon capture and storage (CCS) offers the opportunity to avoid CO2 emissions from for example power plants and cement factories. Chemical-looping combustion (CLC) is one of the most promising capture technologies with potentially very low cost of CO2 capture. In this study we present findings from a solid-fuel 100 kW chemical-looping combustor. A new oxygen carrier - a sintered manganese ore called Sinaus - has been studied in the Chalmers 100 kW unit. The material has been investigated for an operational time of 51.5 h using five fuels: two bituminous coals, two types of wood char, and petcoke. The operational results clearly demonstrate the viability of the CLC process. In comparison to previously used iron-based oxygen carriers, the Sinaus material showed higher gas conversion - up to 88% - and lower loss of char to the air reactor, with carbon capture reaching as high as 100%. Furthermore, the solid-fuel conversion was higher, which is mainly an effect of the choice of fuel size. It was found that the choice of fuel has a crucial impact on performance. Previous experience has shown that the use of large fuel particles gives low carbon capture, whereas pulverized fuel leads to low solid-fuel conversion. By choosing the appropriate - intermediate - size of fuel, it is possible to combine high carbon capture with high solid-fuel conversion. Previous studies indicate that the drawback of many manganese ores is the mechanical stability. Hence, a lot of emphasis was put on an in-depth study of the lifetime of the Sinaus material. Analyzing the production rate of fines, it was found the expected lifetime of the Sinaus particles was 100-400 h. This is lower than what has been found for iron-based material, but most likely sufficient for operation in full-scale chemical-looping applications. Whilst the production of fines was highest during operation with fuel, a lot of fines were produced also during operation without fuel. Seven experiments without fuel, i.e when the observed mechanical degradation was only due to high-velocity impacts and not chemical stress caused by phase transformations, gave a lifetime in the interval 220-1230 h. In conclusion, this first-of-its-kind investigation shows that the lifetime of the oxygen carrier is related to both the change in oxygen-carrier conversion and high-velocity impacts.
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| 2. |
- Lyngfelt, Anders, 1955, et al.
(author)
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Operational experiences of chemical-looping combustion with 18 manganese ores in a 300W unit
- 2023
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In: International Journal of Greenhouse Gas Control. - 1750-5836. ; 127
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Journal article (peer-reviewed)abstract
- Chemical-looping combustion is a novel combustion technology with inherent CO2 capture. The process uses oxygen carriers in the form of metal oxide particles to transfer oxygen from air to fuel. The particles make up the bed material in two fluidized-bed reactors, the air reactor and the fuel reactor, and circulate between the two reactors. Natural minerals of low cost are attractive as oxygen carriers in chemical-looping combustion (CLC), in particular when used for combustion of solid fuels. The presence of ash can restrict the effective lifetime of the oxygen carrier either by loss of bed material associated with the ash removal or by direct reactions between ash and oxygen carrier that impair its reactivity. Independent of the presence of ash, the oxygen carrier lifetime can be limited by attrition leading to loss of fines. Ores considered and used in chemical-looping combustion include ilmenite, iron ore and manganese ore. Manganese ore is the least tested of these, although several studies suggest manganese ores often have higher reactivity as compared to the other two. The present study compares data from operation of 18 different manganese ores in a 300 W chemical-looping combustor, involving 329 h of operation with fuel. Results for 10 of these, involving 148 h of operation, have previously not been published. Some of these manganese ores have also been used in larger pilots, as well as in a 10 MW circulating fluidized-bed boiler. Operational results indicate significant differences between the ores with respect to performance, with syngas conversion ranging between 80 and 100% and methane conversion ranging between 17 and 59% and attrition rates ranging from very high to as low as 0.05%/h. For a few ores formation of fines led to operational failure after only a short period with fuel and for one of the ores agglomeration led to failure. The correlation between performance data and oxygen-carrier characteristics, including elementary analysis, was assessed. Gas conversion for both syngas and methane were correlated to gas conversion in lab testing. However, neither jet cup attrition data nor crushing strength was correlated to attrition in 300 W. This suggests that the mechanisms causing attrition are different at hot conditions and with reactions taking place, which emphasizes the need for pilot testing in the screening of manganese ore oxygen carriers. Fortunately, the correlation between gas conversion and attrition was weak. Thus, high reactivity is not necessarily associated with low attrition assistance and vice versa and several ores show high reactivity in combination with low or moderate attrition. Consequently, screening of manganese ores is well worth while, in order to find materials that can give both high conversion and long life-time. The best four ores were the Chinese Guizhou, South-African UMK, Elwaleed B, and Sibelco´s Braunite having syngas conversion(%)/attrition rate(%/h) of 98.3/0.05, 100/0.33 100/0.5 and 96.7/0.12, respectively.
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| 3. |
- Moldenhauer, Patrick, 1983, et al.
(author)
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Chemical-Looping Combustion of Kerosene and Gaseous Fuels with a Natural and a Manufactured Mn–Fe-Based Oxygen Carrier
- 2018
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In: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 32:8, s. 8803-8816
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Journal article (peer-reviewed)abstract
- Two different oxygen-carrier materials with similar molar ratios of Mn:Fe:Al were tested in continuous chemical-looping combustion operation with different fuels, i.e., syngas (H2/CO), methane, and kerosene. One oxygen carrier was manufactured by spray drying, and the other one was a naturally occurring ore that was crushed. Experiments were conducted in a bench-scale, chemical-looping combustion reactor with continuous fuel addition and continuous circulation of oxygen-carrier particles. In fresh state, i.e., before fuel operation, both materials showed clear CLOU properties. In used state, i.e., after fuel operation, the CLOU properties of the manufactured oxygen carrier were slightly higher than before, whereas those of the natural material decreased significantly. Operation with fuel was conducted for a total of about 47 h between 850 and 950 °C, and clear differences in fuel conversion were observed. At similar oxygen-carrier-to-fuel ratios and temperatures, the manganese ore achieved a clearly higher methane conversion, whereas the manufactured material achieved a higher conversion of H2 and CO. Near-complete conversion of syngas, i.e., >99%, was reached with both materials tested. Particle circulation was indirectly measured and used to estimate solids conversion during continuous operation. The materials were characterized with ICP-SFMS, XRD, and SEM/EDX, and rate indices were calculated based on data obtained in TGA tests with different reactants. Thermodynamic equilibrium calculations were made and used to interpret results from oxygen release and TGA tests. Attrition indices and material porosity were determined for fresh and used samples of the materials used. The manganese ore exhibited a clearly lower structural integrity during redox operation compared to the manufactured material. However, the cost of producing an oxygen carrier from an ore is significantly lower than manufacturing an oxygen carrier by spray drying.
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| 4. |
- Moldenhauer, Patrick, 1983, et al.
(author)
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Oxygen carrier development of calcium manganite-based materials with perovskite structure for chemical looping combustion of methane
- 2017
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In: Proceedings of the 42nd International Technical Conference on Clean Energy, Clearwater, FL, USA, June 11-15, 2017. ; , s. 12-
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Conference paper (other academic/artistic)abstract
- Chemical-looping combustion (CLC) of gaseous fuels could be of interest in industrial processes for heat, power or hydrogen production with carbon capture. For instance, production of steam or hydrogen from refinery gas are possible applications. A series of collaborate European projects has been carried out since 2002, which focused on oxygen-carrier development and upscaling of both theCLC process and oxygen-carrier production with methane or natural gas as fuel. Most recently, in the FP7 SUCCESS project (2013-2017), Ca-Mn-based materials with perovskite structure, CaMnO3, were produced at a larger scale and with cheap and commercial raw materials. The main advantage with this type of oxygen carrier is the ability to release oxygen to the gas phase, hence promoting reactivity in the fuel reactor. In the project, a significant number of such materials were produced and tested. It was found that a perovskite structure can be obtained relatively easy with widely different raw materials for Ca, Mn, Ti and Mg. The produced materials generally had high reactivities and high attrition resistances, but were prone to sulfur poisoning.In this paper, selected results are presented from the different stages of material development and upscaling, i.e., from bench-scale reactors with batch and continuous operation, respectively, as well as from a laboratory-scale unit with continuous operation and a nominal fuel input of 10 kWth. In the 10 kW unit, the gas velocities in the riser and in the grid jet zone of the gas distributor come close to gas velocities of industrial-scale units and, therefore, this unit is used to assess particle lifetime. Results from the 10 kW unit show that very high degrees of fuel conversion can be reached while achieving very high lifetimes.
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| 5. |
- Moldenhauer, Patrick, 1983, et al.
(author)
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Oxygen-Carrier Development of Calcium Manganite–Based Materials with Perovskite Structure for Chemical-Looping Combustion of Methane
- 2020
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In: Energy Technology. - : Wiley. - 2194-4296 .- 2194-4288. ; 8:6
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Journal article (peer-reviewed)abstract
- The present work is related to the upscaling of calcium manganite–based oxygen-carrier materials, which have a perovskite structure, both with respect to the use of inexpensive raw materials, i.e., instead of pure chemicals, and the upscaling of production to multitonne batches. Results are presented from the two different stages of material development, i.e., raw material selection and upscaling. The evaluation involves both operation in chemical-looping combustor units of 300 W and 10 kW, and material characterization. In the latter unit, the gas velocities in the riser and in the grid-jet zone of the gas distributor come close to gas velocities of industrial-scale units and, therefore, this unit is also used to assess particle lifetime. Results from the various chemical-looping combustion units and oxygen-carrier materials produced from various raw materials of both high and low purity show that very high degrees of fuel conversion can be reached while achieving very high oxygen-carrier lifetimes. The composition of the oxygen-carrier materials seems robust and flexible with respect to the precursors used in its manufacturing.
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