| 1. |
- Jerndal, Erik, 1980, et al.
(author)
-
Using Low-Cost Iron-Based Materials as Oxygen Carriers for Chemical Looping Combustion
- 2011
-
In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 66:2, s. 235-248
-
Journal article (peer-reviewed)abstract
- In chemical looping combustion with solid fuels, the oxygen-carrier lifetime is expectedto be shorter than with gaseous fuels. Therefore, it is particularly important to use low-cost oxygencarriers in solid fuel applications. Apart from being cheap, these oxygen carriers should be able toconvert the CO and H2 produced from the solid fuel gasification and be sufficiently hard to withstandfragmentation. Several low-cost iron-based materials displayed high conversion of syngas and highmechanical strength and can be used for further development of the technology. These materials includeoxide scales from Sandvik and Scana and an iron ore from LKAB. All tested oxygen carriers showedhigher gas conversion than a reference sample, the mineral ilmenite. Generally, softer oxygen carrierswere more porous and appeared to have a higher reactivity towards syngas. When compared withilmenite, the conversion of CO was higher for all oxygen carriers and the conversion of H2 was higherwhen tested for longer reduction times. The oxygen carrier Sandvik 2 displayed the highest conversion ofsyngas and was therefore selected for solid fuel experiments. The conversion rate of solid fuels washigher with Sandvik 2 than with the reference sample, ilmenite.
|
|
| 2. |
- Hallberg, Peter, 1984, et al.
(author)
-
Experimental investigation of CaMnO3-δ based oxygen carriers used in continuous Chemical-Looping Combustion
- 2014
-
In: International Journal of Chemical Engineering. - : Hindawi Limited. - 1687-806X .- 1687-8078. ; 2014:412517
-
Journal article (peer-reviewed)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.
|
|
| 3. |
- Hallberg, Peter, 1984, et al.
(author)
-
Investigation of a calcium manganite as oxygen carrier during 99 h of operation of chemical-looping combustion in a 10 kWth reactor unit
- 2016
-
In: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 53, s. 222-229
-
Journal article (peer-reviewed)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.
|
|
| 4. |
- Hanning, Malin, 1987, et al.
(author)
-
Biomass ash interactions with a manganese ore used as oxygen-carrying bed material in a 12 MWth CFB boiler
- 2018
-
In: Biomass and Bioenergy. - : Elsevier BV. - 1873-2909 .- 0961-9534. ; 119, s. 179-190
-
Journal article (peer-reviewed)abstract
- Oxygen carrier aided combustion (OCAC) is a combustion concept which utilises oxygen carriers as bed material in existing fluidised bed boilers. In this study, a manganese ore was used in a 12 MWthCFB boiler. During the experimental session with the manganese ore, the boiler was operated with wood chips as fuel for more than a week without replacement of the bed material. Bed samples were extracted each day in order to investigate interactions between the manganese ore and the wood ash components. The samples were examined with SEM/EDX to follow the chemical distribution of ash elements in the bed particles. Physical properties such as density, size distribution and attrition resistance were followed as well. The impact on the reactivity of the oxygen-carrier bed particles was examined in a batch fluidised bed reactor at laboratory scale with gaseous fuels. Elemental composition analysis of the samples showed that common ash elements such as silicon, calcium, potassium, magnesium and sulphur had been accumulated in the manganese ore. Silicon, calcium and potassium were found throughout the particles as well as in formed surface layers. Sulphur was only found at the surface of the particles. The reactivity of the oxygen-carrying particles was affected during operation and showed a continuous decrease with increasing residence time in the boiler. The decrease in reactivity could be coupled to the layers of ash formed. Thus, this is an important issue when developing novel combustion concepts, such as OCAC and chemical-looping combustion (CLC), for biomass fuels.
|
|
| 5. |
- Hanning, Malin, 1987, et al.
(author)
-
CaMn0.9Mg0.1O3-δ as Oxygen Carrier in a Gas-Fired 10 kWth Chemical-Looping Combustion Unit
- 2013
-
In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 52:21, s. 6923-6932
-
Journal article (peer-reviewed)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.
|
|
| 6. |
- Hanning, Malin, 1987, et al.
(author)
-
Chemical-looping combustion using combined iron/manganese/silicon oxygen carriers
- 2015
-
In: Applied Energy. - : Elsevier BV. - 1872-9118 .- 0306-2619. ; 157, s. 330-337
-
Journal article (peer-reviewed)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.
|
|
| 7. |
- Hanning, Malin, 1987, et al.
(author)
-
Chemical-Looping Using Combined Iron/Manganese/Silica Oxygen Carriers
- 2014
-
In: 3rd International Conference on Chemical Looping, 9-11 September 2014, Göteborg.
-
Conference paper (other academic/artistic)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.
|
|
| 8. |
- Hanning, Malin, 1987, et al.
(author)
-
Combined Oxides of Iron, Manganese and Silica as Oxygen Carriers for Chemical-Looping Combustion
- 2014
-
In: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 124:August 2014, s. 87-96
-
Journal article (peer-reviewed)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.
|
|
| 9. |
- Hanning, Malin, 1987, et al.
(author)
-
Improved Performance in Fluidised Bed Combustion by the Use of Manganese Ore as Active Bed Material
- 2015
-
In: 22nd International Conference on Fluidized Bed Conversion, 14-17 June 2015, Turku.
-
Conference paper (peer-reviewed)abstract
- Insufficient mixing between fuel and air during combustion results in carbon monoxide and unburnt hydrocarbons in the flue gases. In order to minimize these emissions commercial combustion plants are operated with an excess of air added to the furnace. This increases the heat loss associated with the flue gas and thus decreases the overall efficiency of the plant. If combustion is carried out in a fluidised bed, the mixing between fuel and oxygen could be facilitated by using an active bed material with the ability to absorb and release chemically bonded oxygen, depending on the local oxygen concentration. Such active oxygen carriers would also facilitate conversion of relatively stable fuel components such as methane inside the bed, where ignition may be hampered by thermal inertia. This technology, Oxygen Carrier Aided Combustion (OCAC), which is a spin-off technology from Chemical-Looping Combustion (CLC), has recently been proposed.In this study, the potential of using manganese ores as active bed material has been investigated. Combustion of methane in a fluidised bed was carried out with two mixtures of manganese ore and silica sand (50/50 wt.%) in a laboratory circulating fluidised bed combustor. The performance of the manganese ores as active bed materials was compared with the performance of only silica sand in the same experimental unit.The main conclusion drawn from these experiments is that it was possible to significantly reduce the exhaust concentration of carbon monoxide by replacing 50 wt.% of the bed inventory of silica sand with manganese ore. Both ores released gaseous oxygen in inert atmosphere and oxygen was present in the exhaust gas at all times during combustion. The use of the active bed materials thus increased the fuel conversion for a given air-to-fuel ratio.
|
|
| 10. |
- Hanning, Malin, 1987
(author)
-
Manganese Combined Oxides as Oxygen Carriers for Chemical-Looping Combustion
- 2014
-
Licentiate thesis (other academic/artistic)abstract
- The global emissions of greenhouse gases are increasing and the development of mitigation measures is becoming more important. One of the alternatives proposed is carbon capture and storage, where the carbon dioxide emitted from large point sources is captured, compressed and stored in underground storage sites. Many of the largest point sources of carbon dioxide are power plants fuelled by fossil fuels. There are several technologies for adapting the combustion process to capture carbon dioxide. Chemical-looping combustion is one such option and has the advantage of keeping the fuel and the combustion air apart, thus avoiding energy consuming carbon dioxide-nitrogen separation. This is achieved by transferring oxygen from the air to the fuel by a cyclic oxidation and reduction of a solid metal oxide. The oxygen-carrying material needs to meet a number of requirements in order to achieve an efficient combustion process.Manganese oxides have promising properties as oxygen-carrier material and these can be further improved by combining the manganese with for example iron, silica and calcium. Chemical-looping combustion is mainly developed as a technology for fluidised-bed combustion with the oxygen carrier present as the bed material in the form of small particles. To perform well in a circulating fluidised bed the oxygen carrier needs to be mechanically stable as well as have good reactivity with the fuel. During the development of manganese combined oxides, materials with such properties have been identified.The work presented in this thesis examines the performance of manganese combined oxides as oxygen carriers in interconnected fluidised beds with continuous circulation. The operation has been carried out in two reactor systems with gaseous fuels, in which the properties of the materials have been evaluated. It has been shown that full conversion of the fuel can be achieved during chemical-looping combustion in a 10 kWth reactor unit with a calcium manganite of perovskite structure as oxygen carrier. Furthermore, combined oxides of iron-manganese-silica and manganese-silica have been examined in a 300 Wth reactor unit. High fuel conversion was achieved with both combined oxides systems, but the mechanical stability of these materials was not satisfactory. It was found that the mechanical stability of combined oxides of manganese-silica could be improved by adding titania to the material. Future work would include further investigation regarding the effect of the material composition on the performance.
|
|
