| 61. |
- Hallberg, Peter, 1984, et al.
(författare)
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A method for determination of reaction enthalpy of oxygen carriers for chemical looping combustion - Application to ilmenite
- 2011
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Ingår i: Thermochimica Acta. - : Elsevier BV. - 0040-6031. ; 524:1-2, s. 62-67
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Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion (CLC) is a method for combustion with inherent CO(2) separation. In CLC an oxygen carrier supplies the oxygen necessary for fuel conversion. A method to determine the enthalpy of the reaction of oxygen carriers was developed. This method utilizes the fact that for many oxygen carriers the reaction enthalpy with CO is exothermic while it is endothermic with CH(4). By measuring the temperature change for reduction of different mixtures of CO and CH(4) it is possible to find the mixing ratio giving a thermally neutral reaction. From the known reaction enthalpies of CO and CH(4) with oxygen it is then possible to deduce the reaction enthalpy of the oxygen carrier. The reaction enthalpy for a NiO based oxygen carrier is estimated to 475 +/- 8 kJ (mol O(2))(-1). The expected value of 469 kJ (mol O(2))(-1) is in the error range and thus verified the method. The reaction enthalpies for three different ilmenite particles were also determined to 453 +/- 12 kJ (mol O(2))(-1) for synthetic ilmenite and 469 +/- 5 kJ (mol O(2))(-1) for natural ilmenite. A natural ilmenite that has previously been long term tested ended up with the reaction enthalpy 468 +/- 9 kJ (mol O(2))(-1).
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| 62. |
- Hallberg, Peter, 1984, et al.
(författare)
-
CaMnO3-δ Made from Low Cost Material Examined as Oxygen Carrier in Chemical-looping Combustion
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 63, s. 80-86
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Konferensbidrag (refereegranskat)abstract
- Carbon Capture and Storage is a promising method to limit the increasing amount of greenhouse gases in the atmosphere. In this method high purity carbon dioxide is captured at large emission sources, e. g. fossil fuelled power plants. The carbon dioxide can then be transported to a long term storage site, rather than being emitted to the atmosphere. Among the different alternatives for obtaining high purity carbon dioxide during combustion of fossil fuels, Chemical-looping Combustion (CLC) is one of the most promising. Here, the oxygen needed to oxidize a fuel is provided by a solid oxygen carrier. The oxygen carrier is subsequently circulated to another reactor where it is reoxidized with air. By separating these two operations mixing of the combustion products and the nitrogen in the air is avoided. An energy demanding gas separation is thus not necessary.The most crucial part of Chemical-looping Combustion is the solid oxygen carrier. The oxygen carrier should have high reactivity with fuel and oxygen, sufficient oxygen carrying capacity and preferably also low cost. Furthermore it is important that it is able to withstand the tough conditions it is exposed to in a hot fluidizing environment, both with respect to physical attrition and chemical degradation. The most commonly suggested setup of Chemical- looping Combustion is a dual fluidized bed system where gas velocities and mechanical abrasion can be high. When the technology was first demonstrated, nickel oxide based oxygen carriers were typically used. But as nickel is quite costly as well as potentially harmful, alternatives have been sought after.In 2009 Leion et al. [1] investigated an oxygen carrier based on calcium manganite of perovskite structure CaMnO3-δ for chemical looping combustion. The results were very promising and similar materials have since then been successfully tested in pilot rigs up to 120 kWth, including extended operation in continuously operating 10 kWth reactor with very positive results, see Källén et al. [2]. A key feature of these materials is that they are able to release gas phase oxygen at relevant conditions, so called Chemical-looping with Oxygen Uncoupling, see Rydén et al. [3]. Having gas phase oxygen available for fuel oxidation makes gas-solid mixing less critical and thus makes it easier to reach complete fuel conversion.Most studies in which CaMnO3-δ based oxygen carriers have been examined have been using particles manufactured from high quality chemicals. While that is reasonable in the early stages of development, cheaper raw materials would be favourable for industrial applications. Promising oxygen carriers based on manganese ores have been manufactured and characterized by Fossdal et al. [4] and Mohammad Pour et al. [5].This study aims to further examine CaMnO3-δ based oxygen carriers made from low cost, commercial raw materials available in large quantities such as manganese ore. The materials are examined during continuous Chemical- looping Combustion and Oxygen Uncoupling in an experimental reactor with the nominal fuel power 300 Wth. The reactor has previously been used in numerous studies which make comparisons with materials made from high purity chemicals straightforward. During operation several gas concentrations as well as temperatures and pressure drops are measured which allows monitoring of the chemical reactions and fluidization behaviour in the reactor.Fines (particles
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| 63. |
- Hallberg, Peter, 1984, et al.
(författare)
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Chemical Looping Combustion and Chemical Looping with Oxygen Uncoupling Experiments in a Batch Reactor Using Spray-Dried CaMn1–xMxO3−δ (M = Ti, Fe, Mg) Particles as Oxygen Carriers
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:3, s. 1473-1481
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Tidskriftsartikel (refereegranskat)abstract
- Chemical looping combustion and chemical looping with oxygen uncoupling (CLOU) with oxygen carrier particles consisting of CaMn1-xMxO3-delta (M = Ti, Fe, Mg) has been studied by consecutive oxidation and reduction experiments in a fluidized-bed batch reactor. The examined particles were produced by spray drying, and all did show a significant release of gas-phase oxygen to the inert atmosphere at 900 and 1000 degrees C. All particles also provided very high reactivity with syngas and methane. Some of the examined particles showed unfavorable fluidization characteristics, i.e., they formed dust during operation or showed agglomeration or defluidization tendencies. The crushing strength of the particles that formed dust was typically
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| 64. |
- Hallberg, Peter, 1984, et al.
(författare)
-
Experimental investigation of CaMnO3-δ based oxygen carriers used in continuous Chemical-Looping Combustion
- 2014
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Ingår i: International Journal of Chemical Engineering. - : Hindawi Limited. - 1687-806X .- 1687-8078. ; 2014:412517
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Tidskriftsartikel (refereegranskat)abstract
- Three materials of perovskite structure, (M = Mg or Mg and Ti), have been examined as oxygen carriers in continuous operation of chemical-looping combustion (CLC) in a circulating fluidized bed system with the designed fuel power 300 W. Natural gas was used as fuel. All three materials were capable of completely converting the fuel to carbon dioxide and water at 900°C. All materials also showed the ability to release gas phase oxygen when fluidized by inert gas at elevated temperature (700–950°C); that is, they were suitable for chemical looping with oxygen uncoupling (CLOU). Both fuel conversion and oxygen release improved with temperature. All three materials also showed good mechanical integrity, as the fraction of fines collected during experiments was small. These results indicate that the materials are promising oxygen carriers for chemical-looping combustion.
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| 65. |
- Hallberg, Peter, 1984, et al.
(författare)
-
Investigation of a calcium manganite as oxygen carrier during 99 h of operation of chemical-looping combustion in a 10 kWth reactor unit
- 2016
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 53, s. 222-229
-
Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping with oxygen uncoupling is a technology for combustion with inherent carbon dioxide separation. A solid oxygen carrier circulates between the fuel reactor, where it provides oxygen for fuel oxidation, and the air reactor, where it is reoxidized. In this study a 10 kWth pilot reactor was used to examine a calcium manganite based oxygen carrier in continuous operation with natural gas as fuel during 99 h. The composition of the oxygen carrier can be described by the formula CaMn0.775Ti0.125Mg0.1O3-δ. The main part of the material forms a perovskite crystal structure which has oxygen releasing properties. The fuel conversion was generally above 95% and full conversion was reached for certain operating conditions. The elutriation of fines, defined as particles smaller than 45 μm, decreased over time to eventually be below detection limit. That suggested a loss of fines of less than 0.011 wt%/h, indicating a lifetime of over 9000 h. A high fuel conversion with no thermodynamic limitation, good mechanical strength, low cost and very low toxicity shows that this calcium manganite material qualifies as a very promising oxygen carrier.
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| 66. |
- Hanning, Malin, 1987, et al.
(författare)
-
CaMn0.9Mg0.1O3-δ as Oxygen Carrier in a Gas-Fired 10 kWth Chemical-Looping Combustion Unit
- 2013
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 52:21, s. 6923-6932
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Tidskriftsartikel (refereegranskat)abstract
- Spray dried particles of the perovskite material CaMn0.9Mg0.1O3-δ have been examined as oxygen carrier for chemical-looping combustion of natural gas. The experiments have been conducted in a continuously operating reactor with the nominal size 10 kWth. The oxygen carrier particles showed excellent ability to convert fuel and complete combustion was reached at certain conditions. In general, the CO2 yield increased with increased fuel reactor temperature and with increased circulation rate. The oxygen carrier was able to release gaseous oxygen through the so called CLOU-mechanism (Chemical-Looping with Oxygen Uncoupling). When the fuel reactor was fluidized by inert gas, there was oxygen release at temperatures above 700°C, reaching a maximum of more than 3% for temperatures above 850°C. Gas phase oxygen was also measured during operation with fuel, as long as the fuel conversion was complete. When the fuel reactor temperature was above 900°C and a high enough circulation rate was maintained, complete combustion of the fuel was achieved with an oxygen concentration in the outlet stream from the fuel reactor of more than 1%. This suggests that a substantial part of the fuel is converted by gaseous oxygen released from the particles. The oxygen carrier particles were subject to more than 350 h of fluidization, of which more than 175 h was at high temperature and more than 55 h with addition of fuel. The particles did not show any tendencies to form hard agglomerations or break down to fines due to attrition during the experiments. Operational problems included high rate of particle elutriation, which was likely an effect of a mismatch between the size and density of the particles, the air flow and the cyclone.
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| 67. |
- Hanning, Malin, 1987, et al.
(författare)
-
Chemical-looping combustion using combined iron/manganese/silicon oxygen carriers
- 2015
-
Ingår i: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 157, s. 330-337
-
Tidskriftsartikel (refereegranskat)abstract
- Combined oxides of iron, manganese and silicon have been used as oxygen carriers for chemical-loopingcombustion. Three materials with varying composition of iron, manganese and silicon have been evaluatedin oxygen release experiments and during continuous operation with syngas and natural gas as fuels. The concentration of oxygen released increased as a function of temperature and the highest concentrations of oxygen were measured with the material with the highest fraction of manganese. It was also this material which gave the best conversion of both syngas and natural gas; essentially full conversion of syngas and above 95% conversion of natural gas above 900° C. The other two materials showedsimilar performance, albeit with higher syngas conversion for the material with the lowest manganesefraction and the lowest conversion of natural gas for the same material. The materials lasted for 10–14 h of operation with fuel addition before circulation disruption occurred, which was likely caused byparticle attrition in all three cases. A phase diagram of the iron–manganese–silicon–oxide system wasconstructed and the possible relevant phase transitions were identified. This analysis showed that morephase transitions could be expected for the materials with higher manganese content which couldexplain the superior performance during fuel operation of the material with the highest manganese content.It should however be noted that this material was operated with the highest fuel reactor inventoryper thermal power which could also be a contributing factor to the better performance of this material.The study shows that it is possible to achieve very high fuel conversion with combined oxides of iron,manganese and silicon as oxygen carrier. The mechanical stability of the particles was rather poor thoughand would need to be improved. On the other hand the findings relating to material stability is not necessaryvalid for natural materials containing a number of additional elements. The results are also of interestas an indication of how natural materials with similar composition, i.e. manganese ores, wouldperform as oxygen carriers.
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| 68. |
- Hanning, Malin, 1987, et al.
(författare)
-
Chemical-Looping Using Combined Iron/Manganese/Silica Oxygen Carriers
- 2014
-
Ingår i: 3rd International Conference on Chemical Looping, 9-11 September 2014, Göteborg.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Combined oxides of iron, manganese and silica have been used as oxygen carriers for chemical-looping combustion. Three materials with varying composition of iron, manganese and silica have been evaluated in oxygen release experiments and during continuous operation with syngas and natural gas as fuel. The concentration of oxygen released increased as a function of temperature and the highest concentrations of oxygen were measured with the material with the highest fraction of manganese. It was also this material which gave the best conversion of both syngas and natural gas; essentially full conversion of syngas and above 95% conversion of natural gas above 900°C. The other two materials showed similar performance, albeit with higher syngas conversion for the material with the lowest manganese fraction and the lowest conversion of natural gas for the same material. The materials lasted for 10-14 h of operation with fuel addition before circulation disruption occurred, which was likely caused by particle attrition in all three cases. A phase diagram of the iron-manganese-silica system was constructed and the possible relevant phase transitions were identified. This analysis showed that more phase transitions could be expected for the materials with higher manganese content which could explain the superior performance of the material with the highest manganese content. This could possibly also explain the much higher oxygen release of this material. It should however be noted that this material was operated with the highest fuel reactor inventory per thermal power which could also be a contributing factor to the better performance of this material.The study shows that it is possible to achieve very high fuel conversion with combined oxides of iron, manganese and silica as oxygen carrier. The mechanical stability of the particles was rather poor though and would need to be improved. On the other hand the findings relating to material stability is not necessary valid for natural materials containing a number of additional elements. The results are also of interest as an indication of how natural materials with similar composition, i.e. manganese ores, would perform as oxygen carriers.
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| 69. |
- Hanning, Malin, 1987, et al.
(författare)
-
Combined Oxides of Iron, Manganese and Silica as Oxygen Carriers for Chemical-Looping Combustion
- 2014
-
Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 124:August 2014, s. 87-96
-
Tidskriftsartikel (refereegranskat)abstract
- Spray-dried particles with the chemical compositions of Fe0.66Mn1.33SiO3 and FeMnSiO3 have been examined as oxygen carrier materials for chemical-looping combustion. The performance of the materials was examined in oxygen release experiments and during fuel operation with natural gas and syngas. The experiments were carried out in a fluidized-bed chemical-looping reactor system designed for a thermal power of 300 W. The reactor system includes an air reactor and a fuel reactor, as well as loop seals and means for circulation of the oxygen carrier particles. Both materials were able to release gas phase oxygen in inert atmosphere at temperatures between 800-950°C, and with approximately equal oxygen concentrations. Fe0.66Mn1.33SiO3 provided higher conversion of natural gas as compared to FeMnSiO3 and the fuel conversion increased with temperature for both materials. During natural gas operation with Fe0.66Mn1.33SiO3 the conversion reached 100% at around 950°C with a fuel reactor inventory of 235 kg/MW. The fuel conversion was improved when the solids inventory was increased; this improvement could especially be observed for FeMnSiO3 as the fuel conversion was lower for this material. Fe0.66Mn1.33SiO3 provided higher fuel conversion than FeMnSiO3 also when syngas was used as fuel. The fuel conversion increased with temperature for both materials and full conversion was reached above 800°C with a fuel reactor inventory of 225 kg/MW for Fe0.66Mn1.33SiO3, while FeMnSiO3 was incapable of providing full conversion. A rather large elutriation of fines and a significant change in particle size distribution could be observed during operation for both materials.Both materials could work as oxygen carrier for chemical-looping with oxygen uncoupling. Fe0.66Mn1.33SiO3 would be preferred as it has higher conversion of both syngas and natural gas, but the attrition behavior of the material would need to be further investigated.
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| 70. |
- Hanning, Malin, 1987, et al.
(författare)
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Operation with Combined Oxides of Manganese and Silica as Oxygen Carriers in a 300 Wth Chemical-looping Combustion Unit
- 2014
-
Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 63, s. 131-139
-
Konferensbidrag (refereegranskat)abstract
- Chemical-looping combustion is a carbon capture technology which has received increased attention during the last years. The technology is based on fuel oxidation with oxygen provided by solid oxygen carrier particles. In this study two such oxygen carrier materials have been examined in a continuously circulating chemical-looping reactor system designed for a thermal power of 300 W. The two materials consisted of manganese and silica oxides, with an addition of titania in one of them. The oxygen carrier particles were produced by spray drying, followed by calcination and sintering. Both materials released gas phase oxygen in inert atmosphere at 800-950 °C, with the highest concentration at 1.8% observed at 850 °C. The oxygen carrier consisting of only manganese and silica gave the highest fuel conversion for both syngas and natural gas. Full fuel conversion was achieved at 950 °C for syngas and at 900 °C for natural gas with this oxygen carrier material. The fuel conversion increased with temperature for both materials. The material consisting of only manganese and silica suffered from severe attrition and could only be operated for seven hours with fuel. The addition of titania increased the mechanical stability of the particles considerably, and this material was operated for 24 h with fuel. No large production of fines was observed with this material. Combined oxides of manganese and silica are shown to be promising as oxygen carriers for chemical- looping. The mechanical stability can be increased by adding titanium to the MnSi material. The composition would however need to be further examined to optimize the performance of the oxygen carrier.
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