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- Lyngfelt, Anders, 1955, et al.
(författare)
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Operational experiences of chemical-looping combustion with 18 manganese ores in a 300W unit
- 2023
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Ingår i: International Journal of Greenhouse Gas Control. - 1750-5836. ; 127
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Tidskriftsartikel (refereegranskat)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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| 2. |
- Roshan Kumar, Tharun, 1995, et al.
(författare)
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Plant and system-level performance of combined heat and power plants equipped with different carbon capture technologies
- 2023
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Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- Installing carbon capture and storage (BECCS) capability at existing biomass-fired combined heat and power (bio-CHP) plants with substantial emissions of biogenic CO2 could achieve significant quantities of the negative CO2 emissions required to meet climate targets. However, it is unclear which CO2 capture technology is optimal for extensive BECCS deployment in bio-CHP plants operating in district heating (DH) systems. This is in part due to inconsistent views regarding the perceived value of high-exergy energy carriers at the plant level and the extended energy system to which it belongs. This work evaluates how a bio-CHP plant in a DH system performs when equipped with CO2 capture systems with inherently different exergy requirements per unit of CO2 captured from the flue gases. The analysis is based upon steady-state process models of the steam cycle of an existing biomass-fired CHP plant as well as two chemical absorption-based CO2 capture technologies that use hot potassium carbonate (HPC) and amine-based (monoethanolamine or MEA) solvents. The models were developed to quantify the plant energy and exergy performances, both at the plant and system levels. In addition, heat recovery from the CO2 capture and conditioning units was considered, as well as the possibility of integrating large-scale heat pumps into the plant or using domestic heat pumps within the local DH system. The results show that the HPC process has more recoverable excess heat (∼0.99 MJ/kgCO2,captured) than the MEA process (0.58 MJ/kgCO2,captured) at temperature levels suitable for district heating, which is consistent with values reported in previous similar comparative studies. However, using energy performance within the plant boundary as a figure of merit is biased in favor of the HPC process. Considering heat and power, the energy efficiency of the bio-CHP plant fitted with HPC and MEA are estimated to be 90% and 76%, respectively. Whereas considering exergy performance within the plant boundary, the analysis emphasizes the significant advantage the amine-based capture process has over the HPC process. Higher exergy efficiency for the CHP plant with the MEA capture process (∼35%) compared to the plant with the HPC process (∼26%) implies a relatively superior ability of the plant to adapt its product output, i.e., heat and power production, and negative-CO2 emissions. Furthermore, advanced amine solvents allow the BECCS plant to capture well beyond 90% of its total CO2 emissions with relatively low increased specific heat demand.
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