| 1. |
- Jing, Dazheng, 1986, et al.
(författare)
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Innovative Oxygen Carrier Materials for Chemical-Looping Combustion
- 2013
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 37:2013, s. 645-653
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Konferensbidrag (refereegranskat)abstract
- In chemical-looping combustion, the oxygen needed for combustion of fuel is provided by metal oxides called oxygen carriers, and inherent separation of CO2 is achieved without energy penalty. For gaseous fuels, such as natural gas, Ni-based oxygen carriers have generally been shown to be the most reactive. But as Ni-based materials are burdened by high costs and environmental risks with respect to toxicity, it is of high importance to find viable non-Ni alternatives. In the EU-financed project INNOCUOUS, one of the key issues is to find novel non-Ni based oxygen carriers. In this paper results from reactivity investigations of three groups of oxygen carrier materials are reported. The materials were prepared by spray-drying, and are based on 1) CuO, 2) Ca-Mn-X-O where X = Cu, Fe, Ti and Mg, and 3) Mg-Mn-O. A number of materials showed a combination of sufficient mechanical strength, high release of gas phase oxygen and high reactivity with methane, and can thus be considered viable alternatives to Ni-based materials.
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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. |
- 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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| 4. |
- Hallberg, Peter, 1984, et al.
(författare)
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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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| 5. |
- 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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| 6. |
- Hallberg, Peter, 1984, et al.
(författare)
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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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| 7. |
- Hallberg, Peter, 1984, et al.
(författare)
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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
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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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| 8. |
- Hallberg, Peter, 1984
(författare)
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Mixed Oxide Oxygen Carriers for Chemical-Looping Combustion
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Chemical-Looping Combustion is a promising method for combustion with inherent carbon dioxide capture. Oxygen is provided to the fuel with a solid oxygen carrier. The oxygen carrier is circulated between the reactor for fuel oxidation and another reactor where it is reoxidized with air. A good performing oxygen carrier is vital for this process. An oxygen carrier is typically a metal oxide and this work focus on evaluating oxygen carriers based on mixed metal oxides. A method was developed to determine the reduction reaction enthalpy of oxygen carriers in a fluidized-bed batch reactor. The method was verified using a nickel based oxygen carries with known enthalpy. Different oxygen carriers based of the iron-titanium oxide ilmenite were evaluated to determine the reaction enthalpy in a chemical-looping process. Oxygen carriers manufactured with spray drying technology were developed through a screening process. Starting with 79 different materials those deemed promising were tested in a fluidized-bed batch reactor. The ability to release oxygen, reactivity with fuel and fluidization behavior were the most important parameters and based off the results 10 materials were chosen to be investigated in a small continuous Chemical-Looping reactor system. Based off these results 2 materials were examined in a larger continuous Chemical-Looping reactor system where fuel power up to 6 kW were used. Oxygen carrier particles based on calcium manganite performed best with substantial release off oxygen and high to complete conversion on fuel. The material CaMn0.775Ti0.125Mg0.1O3-δ performed best in all three reactor systems. In addition to the oxygen release and reactivity these particles also proved durable with unaffected reactivity and low attrition after 99 h of continuous chemical-looping operation.
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| 9. |
- Hanning, Malin, 1987, et al.
(författare)
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Combined Oxides of Iron, Manganese and Silica as Oxygen Carriers for Chemical-Looping Combustion
- 2014
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 124:August 2014, s. 87-96
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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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| 10. |
- Jing, Dazheng, 1986, et al.
(författare)
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Development of CaMn0.775Mg0.1Ti0.1Ti0.125O3-delta oxygen carriers produced from different Mn and Ti sources
- 2016
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Ingår i: Materials and Design. - : Elsevier BV. - 1873-4197 .- 0264-1275. ; 89, s. 527-542
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite CaMa(0.775)Mg(0.1)Ti(0.125)O(3-delta) has attracted great interest as an oxygen carrier. To apply this material to a commercial scale chemical-looping unit, one key challenge is to find raw materials which are cheap and available in large quantities for production. Considering the content and price, Mn- and Ti-oxides are likely the raw materials having the major effect. Twelve Mn-oxide sources and four different TiO2 powders were evaluated for production of CaMa(0.775)Mg(0.1)Ti(0.125)O(3-delta) in this work. Particles with perovskite structure were successfully spray dried. All oxygen carriers showed oxygen uncoupling characteristics and most of them had a high reactivity, i.e. over 90% methane conversion already at 950 degrees C with a bed mass corresponding to 57 kg/MW, when examined in a batch fluidized-bed system at 900-1050 degrees C. Furthermore bulk density, crushing strength and resistance against attrition were studied. Although the attrition index varied, materials with good attrition resistance were identified. The rates of reaction were analyzed using two pseudo-first order apparent rate constants. The rates varied in a wide range, and are generally lower than with optimized Ni-based materials, but higher than with ilmenite. Still, the added oxygen uncoupling likely has a large positive effect at high degrees of solid conversion, something not seen with Ni-based materials.
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