| 1. |
- Gogolev, Ivan, 1984, et al.
(författare)
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Chemical-looping combustion in a 100 kW unit using a mixture of synthetic and natural oxygen carriers - Operational results and fate of biomass fuel alkali
- 2019
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 88, s. 371-382
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Tidskriftsartikel (refereegranskat)abstract
- Biomass fuel use in chemical looping combustion enables negative CO2 emissions through BECCS (Bio-Energy Carbon Capture and Storage). Effective biomass utilization in CLC requires an economical and effective oxygen carrier to achieve high fuel conversion, effective CO2 capture, and management of the harmful effects of biomass alkali release (bed agglomeration, oxygen carrier deactivation, fouling and corrosion). These issues were addressed in 100 kW CLC pilot experiments. Building on previous work, a mixture of a synthetic calcium manganite perovskite and natural ilmenite was used as the oxygen carrier. Four biomass fuels of varied alkali content were tested: black pellets of steam-exploded stem wood (BP), BP impregnated with K2CO3, a mixture of 50% BP with 50% straw pellets, and wood char. Experiments showed high fuel conversion and very high CO2 capture, with overall performance exceeding that of ilmenite and manganese ore. More than 95% gas conversion was achieved with black pellets at around 950 degrees C. The fate of biomass alkali, previously virtually unknown in CLC research, was explored by implementing online surface-ionization-based measurement of alkali released in the flue gases of the fuel reactor (FR) and air reactor (AR). Release levels were found to correlate with the fuel alkali content. The flue gas measurements and bed material elemental analyses suggest that most of the fuel alkali are accumulated in the oxygen carrier. Unexpectedly, it was found that flue gas alkali release occurs in both the FR and AR, with AR exhibiting an equal or higher rate of release vs. the FR.
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| 2. |
- Schmitz, Matthias, 1984, et al.
(författare)
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Chemical-Looping Combustion of Solid Fuels using Manganese Ores as Oxygen Carriers
- 2016
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 30:2, s. 1204-1216
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Tidskriftsartikel (refereegranskat)abstract
- n chemical looping combustion (CLC), the choice of the oxygen carrier material is crucial with respect to overall system performance and cost. Materials based on manganese ores are promising candidates due to their favorable thermodynamic properties, high availability, and low price. As these ores tend to be comparably soft and prone to attrition, the challenge is to find materials which combine the above-mentioned advantages with sufficient mechanical durability. In this study, three manganese materials were screened for their suitability as oxygen carriers in the chemical looping process. The materials were subjected to continuous operation with fuel in a 10 kW chemical looping unit and evaluated in terms of gas conversion, carbon capture efficiency, and particle lifetime. All oxygen carriers showed good performance and reached more than 90% gas conversion at relevant conditions. Particle lifetime based on fines production was in the range of 99–284 h, which is a considerable improvement compared to a manganese ore previously tested in this unit. One material was ruled out as a potential candidate for up-scaling due to agglomeration tendencies.
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| 3. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Chemical-looping combustion in a 100-kW unit using a mixture of ilmenite and manganese ore as oxygen carrier
- 2016
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 166, s. 533-542
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is a novel carbon-capture technology with potential to drastically reduce the cost of CO2 capture. Relying on interconnected fluidized bed technology, CLC systems can achieve CO2 capture by using oxygen carrying bed material. This so-called oxygen carrier transports oxygen from combustion air to fuel, thus making carbon capture inherent to the CLC process. In this study, we present findings from a 100 kW chemical-looping combustor for solid fuels. The 100 kW unit uses the dual-CFB concept, where both air reactor and fuel reactor are designed as circulating fluidized beds. The oxygen carrier material used in this study consisted of a mixture of ilmenite - which has been used in several studies in CLC - and a manganese ore. Previous studies have shown that gas conversion can be significantly increased by using manganese ore particles as oxygen carrier. However, previous testing has also shown that the production of fines, i.e. particle attrition, may be high when using manganese ore. The reason for mixing the two materials is thus to obtain an oxygen carrying material that has high reactivity, and yet does not produce too much fines during fuel operation. The 100 kW unit was operated in total for 18 h with fuel. Three fuels were used in the experiments: two bituminous coals and wood char. Gas conversion was high, and increased with increasing fraction of manganese ore in the oxygen-carrier mixture. At the end of the experiments, the fraction of manganese ore in the bed material was approximately 8%, which also was the highest fraction during all tests. The mixture of ilmenite and manganese ore gave significant improvements in gas conversion in comparison to only ilmenite. The highest gas conversion observed during testing with bituminous coal was 91.5%, as compared to 84% with only ilmenite as oxygen carrier during similar conditions in the 100 kW unit. These test results indicate that the addition of manganese ore could almost halve the fraction of unconverted gas. Thus, mixing mechanically stable ilmenite with more reactive manganese ore can give reductions in costs as compared to using manganese ore only, and still give significantly reduced oxygen demand as compared to ilmenite. In the present case - mixing of ilmenite and manganese ore - the high reactivity was also possible to combine with improved operability of the material, primarily manifested as lower production rate of fines. (C) 2015 Elsevier Ltd. All rights reserved.
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| 4. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Chemical-looping combustion of biomass in a 100 kW pilot
- 2017
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Ingår i: European Biomass Conference and Exhibition Proceedings. - 2282-5819. ; 2017:25thEUBCE, s. 412-415
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Konferensbidrag (refereegranskat)abstract
- Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the cost of capture. By using a circulating bed material to transfer oxygen from the combustion air to the fuel, air and fuel are never mixed and the CO 2 can be obtained as a separate flue gas stream, undiluted by N 2 . In other words, in contrast to other capture technologies, which are burdened with a significant energy penalty, carbon capture is inherent to the CLC process. Chemical-looping combustion of biomass in combination with carbon capture and storage would lead to so called negative emissions. Manganese ores are highly promising oxygen-carrier candidates due to high reactivity and high availability. Here, we present findings from a 100 kW chemical-looping combustor for solid fuels, using a sintered manganese ore called “Sinaus” as oxygen carrier and two kinds of wood pellets as fuel. Preliminary results from 6 h of operation with steam-exploded wood pellets show fuel conversion up to 75%, and essentially complete CO 2 capture. The expected lifetime of the oxygen carrier particles was found to be 100-400 hours.
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| 5. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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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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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 65, s. 170-181
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Tidskriftsartikel (refereegranskat)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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| 6. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Chemical-looping combustion of solid fuels in a 100 kW dual circulating fluidized bed system using iron ore as oxygen carrier
- 2016
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Ingår i: Journal of Environmental Chemical Engineering. - : Elsevier BV. - 2213-3437 .- 2213-2929. ; 4:1, s. 1029-1039
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the cost of capture. By using a circulating bed material to transfer oxygen from the combustion air to the fuel, air and fuel are never mixed and the CO2 can be obtained as a separate flue gas stream, undiluted by N2. In other words, carbon capture is inherent to the CLC process. Here, we present findings from a 100 kW chemical-looping combustor for solid fuels. The oxygen carrier used in the present tests was an iron ore from Tierga, Spain. In total, 26 h of operation using bituminous coal and wood char as fuel was achieved. The highest gas conversion with bituminous coal was 87%, and the highest gas conversion using wood char as fuel was 93%. The carbon capture efficiency with bituminous coal was 94-98%, which is lower than what has been observed with ilmenite. For the wood char, the carbon capture was even lower. The fate of nitrogen and sulfur was investigated. It was found that 84 wt% of the S-containing gas was SO2, and only 16 wt% was H2S. The nitrogen analysis indicates that the fuel-N converted to gas was distributed as 10 wt% NO, 37 wt% NH3, and 53 wt% N2. It was found that the oxygen-carrier particles retained their high reactivity throughout the operational period. Furthermore, the expected lifetime of the iron ore was found to be approximately 300 h.
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| 7. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Estimating the Solids Circulation Rate in a 100-kW Chemical Looping Combustor
- 2017
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Ingår i: Chemical Engineering Science. - : Elsevier BV. - 0009-2509. ; 2017, s. 351-359
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Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) is a technology of CO2 capture that can drastically reduce its cost. The solids circulation inside a 100-kW chemical looping combustor was investigated using a novel oxygen carrier called Sinaus by adding fuel batches to the fuel reactor. The decline and subsequent rise of oxygen concentration in the air reactor after each addition was used to determine the residence time of solids in the fuel reactor and adjacent vessels. The obtained residence time, in combination with the solids inventory, determined the solids circulation for a particular batch experiment. After performing a number of such experiments, the above circulation was correlated with other experimental data, revealing a good correlation between the solids flow at the top of the air reactor riser and the actual circulation obtained using batch tests. The relationship between global circulation, , and the mass flow in the air reactor riser, (riser), was found to be linear within the investigated interval, being described as = 6.6 + 0.057 (riser). Although this correlation was valid only for the investigated reactor system, the approach used to obtain the solids circulation could be used to derive a similar correlation for any dual fluidized bed system.
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| 8. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Material balances of carbon, sulfur, nitrogen and ilmenite in a 100 kW CLC reactor system
- 2014
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 27, s. 188-202
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) is an unmixed combustion concept where fuel and combustion air are kept separate by means of an oxygen carrier, and the CO2 capture is inherently achieved. This work presents findings from a 100 kW chemical-looping combustor, which was operated with Colombian bituminous coal for 12 h, using ilmenite as oxygen carrier. The focus of the study is on a 4.7-h experiment with stable operating conditions, during which inbound and outbound gaseous, liquid, and solid flows of carbon, sulfur, nitrogen and ilmenite were carefully monitored and analyzed. The fuel power during this experiment was 71 kW. The gas conversion reached 83%, the carbon capture efficiency was 98-99%, and the solid fuel conversion based on carbon was 65%. The carbon balance confirms that a large fraction of the fuel escapes the reactor system unconverted. It also demonstrates that essentially all in- and outbound flows of carbon have been accounted for. The sulfur balance shows that the conversion in the fuel reactor of inbound sulfur is around 72%. Furthermore, it is found that 75% of the S-containing gas is SO2, and only 25% is H2S. The nitrogen analysis indicates that 62% of the nitrogen fed with the coal is converted to gas, and that the nitrogen in this gas is distributed as 1 wt-% HCN, 11 wt-% NO, 26 wt-% NH3, with the balance probably being N-2. In addition, the present work includes a comprehensive study on the structural integrity of ilmenite in circulating fluidized beds. It is found that the expected lifetime of ilmenite is approximately 700-800 h.
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| 9. |
- Linderholm, Carl Johan, 1976, et al.
(författare)
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Use of Low-Volatile Solid Fuels in a 100 kW Chemical-Looping Combustor
- 2014
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 28:9, s. 5942-5952
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Tidskriftsartikel (refereegranskat)abstract
- Carbon capture and storage (CCS) can be used to mitigate climate change. Chemical-looping combustion (CLC) is an innovative carbon-capture technology with potential to drastically reduce the capture cost. In CLC, oxygen is transported from combustion air to fuel by means of metal-oxide particles, called oxygen carrier. This work presents findings from a 100 kW CLC reactor system, which is designed as interconnected fluidized beds. The 100 kW unit was operated with ilmenite as the oxygen carrier. Swedish wood char and Mexican petcoke, both having low volatile content, were used as fuel. High gas conversion was achieved with both fuels. The carbon capture efficiency was high with wood char, but not as high with petcoke. The duration of operation was 34.5 h with fuel, of which the majority, 31 h, was achieved with wood char. Oxygen demand was strongly correlated with the solids inventory in the fuel reactor, as has been observed in previous works. Using wood char as fuel, gas conversion was 90-95.3%, except during high fuel power, and carbon capture efficiency was 93-97%, except during high fuel power. The gas conversion should be compared to what has previously been observed in the 100 kW unit, where the highest gas conversion was 84%, using a bituminous coal. Furthermore, comparatively high solid fuel conversion was seen in many tests with wood char-the highest value was 89%. Using petcoke as fuel, high gas conversion was achieved even when employing very high fuel power, 148 kW. The highest gas conversion for petcoke was 89%. The carbon capture efficiency was, however, much lower than what has been observed with pulverized coal and wood char. In summary, this study shows that important improvements can be achieved regarding gas conversion in the 100 kW unit by using low-volatile fuels.
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| 10. |
- Schmitz, Matthias, 1984, et al.
(författare)
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Chemical looping combustion of biomass in 10-and 100-kW pilots - Analysis of conversion and lifetime using a sintered manganese ore
- 2018
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Ingår i: Fuel. - : Elsevier BV. - 0016-2361. ; 231, s. 73-84
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Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) is a type of carbon capture technology that employs metal oxide particles in a redox reaction to transport oxygen to the fuel. As opposed to first-generation carbon capture concepts, CLC does not include a gas separation step and thus offers the advantage of having no thermodynamic energy penalty in the capture process. Manganese-containing oxygen carriers have been shown to offer a good compromise of gas conversion performance, availability, and cost. On the other hand, previously tested manganese materials have often been challenged with high attrition in continuous CLC. By sintering the ore prior to its use as oxygen carrier, the structure of the particles can be reinforced to increase their durability in the process. In this study, a sintered manganese ore was tested for 56 h in two pilot units of different size. The oxygen carrier worked well in the process, was easily fluidized, and did not exhibit any tendency towards agglomeration. Compared to other manganese materials tested in the same units, a higher lifetime based on fines production was reached, while gas conversion performance was similar. Different biomass fuels, mainly biochar of different sizes and black wood pellets, were employed in the study. A clear correlation between gas conversion and the fuel volatile content was detected; this is consistent with results reported in previous studies. The highest gas conversion reached in both units was similar to 93.5% using wood char. The highest carbon capture efficiency, 99% and 100% in the 10- and 100-kW unit, respectively, was reached with black pellets. To compare the tested material with the state-of-the-art oxygen carrier ilmenite, some tests were conducted with a bituminous coal that had been used in the same pilot with ilmenite. The results indicate a higher conversion performance for the tested manganese material.
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