| 1. |
- Hildor, Fredrik, 1992, et al.
(författare)
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Steel converter slag as an oxygen carrier in a 12 MWth CFB boiler – Ash interaction and material evolution
- 2019
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 88, s. 321-331
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 Elsevier Ltd Steel converter slag or LD slag is a byproduct of the basic oxygen steel production process, where raw iron from the blast furnace is converted to steel. LD slag contains mainly calcium and iron compounds and smaller amounts of magnesium, silicon, manganese and vanadium. The iron content, about 17 wt.% of the slag, makes this material a potential oxygen carrier for combustion processes such as Oxygen Carrier Aided Combustion (OCAC) or Chemical Looping Combustion (CLC). This study will present an investigation of the use of LD slag as an oxygen carrier in OCAC at semi-industrial scale. The Chalmers 12 MWth biomass circulating fluidized bed boiler was operated using LD slag as bed material under OCAC conditions. During the operation, bed samples from the boiler were extracted and analyzed with ICP-SFMS, SEM-EDS, XRD and different mechanical tests to analyze chemical and physical changes of the bed material as a function of time. The samples were also investigated in a laboratory fluidized bed reactor to determine the change in reactivity towards common volatile fuel components, i.e. CO, H2, CH4 and C6H6. It was found that LD slag can be utilized as an oxygen carrier in a combustion process for biofuel. However, the reactivity towards syngas, CH4 and C6H6 is reduced as a function of time in the boiler, which is believed to be caused by accumulation of, and interaction with, alkali from the biofuel ash. Sulfur addition may decrease the adverse effects of alkali on combustion efficiency, but not eliminate them completely.
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| 2. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Chemical-Looping Technologies using Circulating Fluidized Bed Systems: Status of Development
- 2017
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Ingår i: 12th International Conference on Fluidized Bed Technology, CFB 2017. ; , s. 11-22
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Konferensbidrag (refereegranskat)abstract
- In chemical-looping combustion (CLC), an oxygen carrier provides lattice oxygen for complete combustion of a fuel for heat and power production. The reduced metal oxide is then oxidized in a separate reactor. The combustion products CO2 and H2O are obtained in pure form, without any nitrogen in the gas. As no gas separation work is needed, this could be a breakthrough technology for carbon capture (CCS). Normally, the fuel- and air-reactor are designed utilizing inter-connected fluidized beds. The same underlying reversible redox reactions of CLC can be used for other fuel conversion technologies. These include fluidized bed processes for gas, solid and liquid fuels for heat, power, syngas or hydrogen production. Some of these concepts were suggested as far back as the 1950’s, while others have just recently been proposed. Chalmers University of Technology has been involved in CLC research for over 18 years, and this paper will provide a review of some recent developments with respect to CLC with gaseous, liquid and solid fuels. Further, the paper will provide an overview some related technologies where Chalmers is conducting research: i) Chemical-looping gasification (CLG), ii) Chemical-looping reforming (CLR) and iii) Chemical-looping tar reforming (CLTR). In these processes, a pure syngas/hydrogen can be produced effectively, which could be utilized for chemical or fuel production.
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| 3. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Chemical-looping technologies using circulating fluidized bed systems: Status of development
- 2018
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 172, s. 1-12
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Forskningsöversikt (refereegranskat)abstract
- In chemical-looping combustion (CLC), an oxygen carrier provides lattice oxygen for complete combustion of a fuel for heat and power production. The reduced metal oxide is then oxidized in a separate reactor. The combustion products CO 2 and H 2 O are obtained in pure form, without any nitrogen in the gas. As no gas separation work is needed, this could be a breakthrough technology for carbon capture (CCS). Normally, the fuel- and air-reactor are designed utilizing inter-connected fluidized beds. The same underlying reversible redox reactions of CLC can be used for other fuel conversion technologies. These include fluidized bed processes for gas, solid and liquid fuels for heat, power, syngas or hydrogen production. Some of these concepts were suggested as far back as the 1950's, while others have just recently been proposed. This paper will provide a review of some recent developments with respect to CLC with gaseous, liquid and solid fuels, with focus on operational experience. Today, more than 35 continuous units have been used worldwide, with over 9000 h of operational time. Although most experience has been reported for methane and natural gas, significant testing has now also been performed with various solid fuels. Some recent developments include i) shift from Ni-based materials to more benign metal oxide oxygen carriers, ii) use of different types of biomass and iii) operation at semi-commercial scale. Furthermore, this paper will also provide an overview some related technologies which also utilize oxygen carriers in interconnected fluidized beds: i) Chemical-looping gasification (CLG), ii) Chemical-looping reforming (CLR) and iii) Chemical-looping tar reforming (CLTR). In these processes, a pure syngas/hydrogen can be produced effectively, which could be utilized for chemical or fuel production.
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| 4. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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Screening of Combined Mn-Fe-Si Oxygen Carriers for Chemical Looping with Oxygen Uncoupling (CLOU)
- 2015
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 29:3, s. 1868-1880
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Tidskriftsartikel (refereegranskat)abstract
- Combined oxygen carriers of Mn, Fe, and Si were screened for the chemical looping with oxygen uncoupling process with the objective of identifying materials with high reactivity and sufficient attrition resistance. Eleven oxygen carrier materials were produced by spray-drying and then calcined for 4 h at 1100 and 1200 degrees C. The ability of the oxygen carriers to release oxygen and to convert gaseous fuels was investigated in a batch fluidized-bed reactor under alternating reducing and oxidizing conditions for temperatures ranging from 850 degrees C to 1050 degrees C. The attrition behavior of the different materials was evaluated in a jet-cup attrition rig. All investigated oxygen carriers proved to release oxygen and showed high reactivity toward synthesis gas (50% CO in H-2). Oxygen carrier materials with comparably lower mechanical stability were found to have a higher reactivity toward methane. One of the investigated formulations showed to have both high mechanical stability and resistance toward attrition, as well as good methane conversion and oxygen release.
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| 5. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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Standard Enthalpy of Formation of CuAl2O4 Revisited
- 2015
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Ingår i: Chemical Engineering Communications. - : Informa UK Limited. - 0098-6445 .- 1563-5201. ; 202:5, s. 694-697
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Tidskriftsartikel (refereegranskat)abstract
- Due to discrepancy in the standard enthalpy of formation, ΔH_f^0, of copper(II) aluminate (CuAl2O4) reported in thermodynamic databases, the calculated reaction enthalpy, ΔH_r, of CuAl2O4 with reducing gases varies considerably. In this work, the standard enthalpy of formation, ΔH_f^0, of copper(II) aluminate (CuAl2O4) is reassessed using the reaction enthalpy, ΔH_r, of CuAl2O4 with CO measured by differential scanning calorimetry (DSC). A value of –1824.4±4.1 kJ/mol was found for the standard enthalpy of formation, ΔH_f^0, of CuAl2O4.
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| 6. |
- Azimi, Golnar, 1985, et al.
(författare)
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Comprehensive study of Mn–Fe–Al oxygen-carriers for chemical-looping with oxygen uncoupling (CLOU)
- 2015
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 34, s. 12-24
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Tidskriftsartikel (refereegranskat)abstract
- The reactivity and attrition resistance of Mn–Fe oxygen carriers with addition of Al2O3 as support have been investigated. Spray-dried oxygen-carrier particles with Mn:Fe molar ratios of 80:20 and 33:67 were prepared using different amounts of Al2O3. Each material was calcined for 4 h at 950 °C, 1100 °C or 1200 °C. The oxygen carriers were studied in a batch fluidized bed reactor to investigate their reactivity with wood char, CH4, syngas and also their oxygen release in N2. In order to measure the mechanical stability of the different materials, the attrition resistance was measured in a jet-cup apparatus. Addition of Al2O3 to materials with a Mn:Fe molar ratio of 80:20 was not advantageous. Generally oxidation of these materials was problematic. The Al2O3 supported materials with a Mn:Fe molar ratio of 80:20 calcined at 950 °C and 1100 °C showed poor attrition resistance and were highly fragmented or turned to dust, whereas those calcined at 1200 °C showed high attrition resistance but poor gas conversion.Materials with a Mn:Fe molar ratio of 33:67 supported with Al2O3 generally showed better attrition resistance. Also their oxidation with 5 vol% of oxygen was possible at temperatures higher than 850 °C. Furthermore, some of these materials showed good reactivity with methane, syngas and char. Low attrition, good reactivity and CLOU properties in combination with potentially low raw materials costs, make these materials interesting for CLC.
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| 7. |
- Cheng, M., et al.
(författare)
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Oxidation of Ammonia by Ilmenite under Conditions Relevant to Chemical-Looping Combustion
- 2015
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 29:12, s. 8126-8134
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Tidskriftsartikel (refereegranskat)abstract
- The oxidation of ammonia to NOx and N-2 was investigated under conditions that pertain to the fuel reactor during the chemical-lopping combustion of coal with ilmenite. The catalytic decomposition of NH3, the oxidation of NH3 over ihnenite, and the reduction of NO by reduced ilmenite and NH3 were studied experimentally. The catalytic decomposition of NH3, NO reduction by NH3, and reduced ilmenite were found to be important for N-2 formation. NH3 oxidation over ilmenite was the only way in which NO could be formed in this systerri, with around 18% the NH3 being converted to NO at 850-950 degrees C, The oxidation of NH3 was only slightly influenced by the reactor temperature but was strongly influenced by the concentrations of NH3 and syngas. NO formation was,promoted by high concentrations of NH3 and decreased by high concentrations of syngas. The selectivity of the NH3 toward-NO formation was favored at low concentrations of NH3 and syngas. The conversion of NH3 was complete in most cases, although 15-25% of the NH3 was not converted when the inlet syngas concentration increased to levels higher than 10-30%.
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| 8. |
- Darwish, Esraa, 1986, et al.
(författare)
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Experimental and Thermodynamic Study on the Interaction of Copper Oxygen Carriers and Oxide Compounds Commonly Present in Ashes
- 2019
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 33:3, s. 2502-2515
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Tidskriftsartikel (refereegranskat)abstract
- The chemical looping combustion (CLC) and chemical looping oxygen uncoupling (CLOU) processes are unique and efficient methods for the direct separation of carbon dioxide in combustion. In these processes, metal oxides are used under reducing atmosphere as an oxygen carrier to transfer oxygen between air and a fuel reactor. The fuel is converted by oxygen provided by the oxygen carrier. In the case of using coal or any ash-containing fuel, interaction between coal-derived ash and the oxygen carrier is likely to occur and can lead to deactivation and agglomeration of the oxygen carriers. As the amount of the possible compounds and compositions of ash can vary widely, thermodynamic equilibrium calculations can be used to represent the formed compounds during the CLC process to reveal the interaction between the oxygen carrier and the commonly present oxide compounds in ash. In this study, the interaction between the oxide compounds commonly present in ash and CuO oxygen carriers was studied both experimentally and thermodynamically. CuO is a widely used oxygen carrier with CLOU properties, the ability to release gaseous oxygen under inert atmosphere. Experiments were carried out at 900 degrees C under both oxidizing and inert atmosphere using CuO or Cu2O (CuO/Cu2O) as the oxygen carrier and SiO2, Al2O3, Fe2O3, CaO, and K2O to represent the oxide compounds present in ashes. To observe the interaction of the oxygen carriers with each oxide compound used, equal moles of copper oxide and oxide compound were mixed. Further, oxide compound fractions with the elemental composition relevant to coal ash were mixed with oxygen carriers to investigate the interaction under conditions approaching realistic operation. In all cases, a significant amount of copper oxides survived without any interaction. However, it was observed that silicate-based formations, especially potassium silicates, lead to strong agglomeration which most likely would decrease the lifetime and oxygen-releasing ability of the oxygen carriers. As the results showed that the thermodynamic equilibrium-based calculations were well in line with the experiments, these calculations can be a good first approach in these types of investigations.
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| 9. |
- Frick, Volkmar, 1983, et al.
(författare)
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Investigation of Cu-Fe and Mn-Ni oxides as oxygen carriers for chemical-looping combustion
- 2016
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Ingår i: Fuel Processing Technology. - : Elsevier BV. - 0378-3820. ; 150, s. 30-40
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Tidskriftsartikel (refereegranskat)abstract
- Combined Cu-Fe and Mn-Ni oxygen carriers were investigated as bed" materials for-chemical-looping combustion.,The aim was to identify material combinations which yield oxygen carriers with a high reactivity towards gaseous fuels, such as CO, H-2 and CH4, as well as sufficient mechanical durability. For this purpose, 18 different oxygen carriers were spray-dried and calcined at defined temperatures. Gas conversion as well as release of gaseous oxygen was-investigated in a batch fluidized bed reactor setup at temperatures between 850 and 1050 degrees C. For testing the mechanical durability; a jet-cup attrition rig was used. Moreover, properties like specific surface area, oxygen transfer capacity and crystalline phase composition were examined to physically and chemically characterize the oxygen carrier particles. For both the Cu-Fe and Mn-Ni-based materials, oxygen carriers could be produced which showed a high reactivity with gaseous fuels like CO or CH4 while having a sufficiently high mechanical strength. These properties make them interesting candidates for application in chemical-looping combustion. (C) 2016 Elsevier B.V. All rights reserved.
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| 10. |
- Frick, Volkmar, 1983, et al.
(författare)
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Screening of supported and unsupported Mn-Si oxygen carriers for CLOU (chemical-looping with oxygen uncoupling)
- 2015
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Ingår i: Energy. - : Elsevier BV. - 0360-5442. ; 93, s. 544-554
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen carriers based on oxides of Mn and Si in combination with Mg, Al, Ca and Ti (Mn0.63Si0.27X0.1, X = Ca(OH)2, TiO2, MgO, AlOOH) were examined for CLOU (chemical-looping with oxygen uncoupling), in terms of oxygen uncoupling ability and ability to convert both methane and syngas. The focus was on the optimization of the production process to yield mechanically strong oxygen carrier particles with a reasonable activity. For this purpose, 15 types of oxygen carriers were produced by spray-drying and calcined for different time periods and at different temperatures. The oxygen uncoupling behavior and gas conversion of the materials were investigated in a batch fluidized-bed reactor under alternating oxidizing and reducing conditions in the temperature range 850-1050 °C. To determine attrition resistance and mechanical stability, a jet-cup attrition rig was used. Furthermore, physical and chemical properties such as specific surface area and crystal phase composition have been determined. For the oxygen carriers with additives of Mg, Al, Ca, Ti, some material combinations showed a significant increase in reactivity and improved mechanical stability compared to the unsupported Mn-Si particles. Changing the production process (milling process and calcination time) just caused slight difference in attrition resistance, gas conversion as well as oxygen release.
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