| 1. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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CaxLa1−xMn1−yMyO3−δ (M = Mg, Ti, Fe or Cu) as Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2013
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 27:8, s. 4097-4107
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Tidskriftsartikel (refereegranskat)abstract
- Perovskite materials of the type CaxLa1−xMn1−yMyO3−δ (M = Mg, Ti, Fe or Cu) have been investigated as oxygen carriers for the chemical-looping with oxygen uncoupling (CLOU) process. The oxygen carrier particles were produced by mechanical homogenization of primary solids in a rotary evaporator followed by extrusion and calcination at 1300°C for 6 h. The chemical-looping characteristics of the substituted perovskites developed in this work were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900−1000°C during alternating reducing and oxidizing conditions. The oxygen carriers showed oxygen releasing behaviour (CLOU) in inert atmosphere between 900−1000°C. In addition, their reactivity with methane was high, approaching complete gas yield for all of the materials at 950°C, the exception being the Cu-doped perovskite which defluidized during reduction. The rates of oxygen release were also investigated using devolatilized wood char as solid fuel, and were found to be similar. The required solids inventory in the fuel reactor for the perovskite oxygen carriers is estimated to be 325 kg/MWth. All of the formulations exhibited high rates of oxidation and high degree of stability with no particle fragmentation or agglomeration. The high reactivity and favourable oxygen uncoupling properties make these oxygen carriers promising candidates for the CLOU process.
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| 2. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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CaZrO3 and SrZrO3-based CuO Oxygen Carriers for Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2014
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Ingår i: Energy Procedia. - : Elsevier BV. - 1876-6102. ; 51, s. 75-84
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Konferensbidrag (refereegranskat)abstract
- The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are novel solutions for efficient combustion with inherent separation of carbon dioxide. In this work, oxygen carriers based on CuO supported by zirconates of SrZrO3 and CaZrO3 are investigated. The oxygen carriers were produced by mechanical homogenization of primary solids in a rotary evaporator followed by extrusion, drying and calcination at 950 and 1030 degrees C for 6 h. Their chemical-looping performance was evaluated in a laboratory-scale fluidized-bed reactor at 900 and 925 degrees C under cyclic oxidizing, inert (N-2) and reducing (CH4) conditions. All oxygen carriers exhibited rapid release of oxygen in the inert environment (CLOU) with high conversion of methane. The carrier calcined at 1030 degrees C with SrZrO3 as support showed no agglomeration or deactivation and exhibited the highest reactivity. Thus, the use of this oxygen carrier could be of interest for the CLOU process.
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| 3. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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Evaluation of CuAl2O4 as an Oxygen Carrier in Chemical-Looping Combustion
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 51:43, s. 13924-13934
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Tidskriftsartikel (refereegranskat)abstract
- The chemical-looping combustion (CLC) process is a novel solution for efficient combustion with intrinsic separation of carbon dioxide. The process uses a metal oxide as an oxygen carrier to transfer oxygen from an air to a fuel reactor where the fuel, or gasification products of the fuel, reacts with the solid oxygen carrier. In this work, copper(II) aluminate (CuAl2O4) was assessed as a potential oxygen carrier using methane as fuel. The carrier particles were produced by freeze–granulation and calcined at 1050 °C for a duration of 6 h. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized-bed reactor in the temperature range of 900–950 °C during 45 alternating redox cycles. The oxygen carrier exhibited reproducible and stable reactivity behavior in this temperature range. Neither agglomeration nor defluidization was noticed in any of the cycles carried out at 900–925 °C. However, after reactivity tests at 950 °C, soft agglomeration and particle fragmentation were observed. Systematic phase analysis of the Cu–Al–O system during the redox cycle was carried out as a function of duration of reduction and oxygen concentration during the oxidation period. It was found that the CuAl2O4 is reduced to copper(I) aluminate (CuAlO2; delafossite), Cu2O, and elemental Cu. The CuAlO2 phase is characterized by slow kinetics for oxidation into CuO and CuAl2O4. Despite this kinetic limitation, complete conversion of methane with reproducible reactivity of the oxygen carrier is achieved. Thus, CuAl2O4 could be a potential oxygen carrier for chemical-looping combustion.
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| 4. |
- Arjmand, Mehdi, 1986, et al.
(författare)
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Prospects of Al2O3 and MgAl2O4-Supported CuO Oxygen Carriers in Chemical-Looping Combustion (CLC) and Chemical-Looping with Oxygen Uncoupling (CLOU)
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 25:11, s. 5493-5502
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Tidskriftsartikel (refereegranskat)abstract
- The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are attractive solutions for efficient combustion with direct separation of carbon dioxide. In this work, the feasibility of CuO supported on Al2O3 and MgAl2O4 for CLC and CLOU processes is investigated. The oxygen carriers were produced by freeze-granulation and calcined at 950 and 1050 degrees C. The chemical-looping characteristics were evaluated in a laboratory-scale fluidized bed at 900 and 925 degrees C under alternating reducing and oxidizing conditions. Tendencies toward agglomeration, defluidization, and loss of active phase were analyzed by changing the experimental process variables, such as reaction time, temperature, and reducing and inert environments. Complete conversion of methane was obtained for all oxygen carriers investigated in this work Three out of four oxygen carriers also featured the rapid release of oxygen in an inert environment (CLOU). In the case of Al2O3) as support, a CLC and a CLOU oxygen carrier were obtained depending on the calcination temperature. In addition, analyses of the CuO-Al2O3 phase equilibria system under oxidizing and reducing conditions have been carried out. At the investigated temperatures, it is inferred for the case of Al2O3 as support that part of the active phase (either CuO or CuAl2O4 is bound as CuAlO2 during incomplete reduction with slow kinetics for reoxidation. However, when complete reduction is attained, the original active phase composition is rejuvenated upon oxidation. As a result, the use of CuAl2O4 is suggested for CLC processes from the point of agglomeration and attrition-free functioning of the oxygen carrier. In the case of MgAl2O4 as support, the oxygen carrier exhibited a stable oxygen-releasing behavior due to the existence of relatively intact CuO. Together with the absence of agglomeration and major morphological changes, the use of MgAl2O4-supported CuO is suggested as a suitable oxygen carrier for CLOU processes.
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| 5. |
- Azad, Abdul-Majeed, 1957, et al.
(författare)
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Examining the Cu-Mn-O Spinel System as an Oxygen Carrier in Chemical Looping Combustion
- 2013
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Ingår i: Energy Technology. - : Wiley. - 2194-4296 .- 2194-4288. ; 1:1, s. 59-69
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Tidskriftsartikel (refereegranskat)abstract
- Chemical-looping combustion (CLC) and chemical-looping combustion with oxygen uncoupling (CLOU) are attractive alternatives to conventional combustion that provide efficient and direct separation of CO2. Both processes use metaloxides as oxygen carriers to transfer oxygen between two reactor vessels: the air and fuel reactors. Although monometallic oxides (such as Mn3O4, Fe2O3, NiO, and CuO) have been successfully employed as oxygen carriers, double oxides of the general formula CuxMn3_xO4 in the CuO–Mn2O3 system are examined in this work. The carrier was produced by mixing, extruding, and calcining a 1:1 molar (30.8:69.2 mass ratio) mixture of CuO and Mn2O3 at 950 8C for 6 or 12 h in static air. XRD analysis revealed that spinels of the general formula CuxMn3_xO4 were formed with 0.1_x_2.5 in which x=3Cu/(Cu+Mn). The chemical-looping performance was evaluated in a laboratory-scale fluidized-bed reactor from 800–850 8C over several alternating redox cycles using CH4 as the fuel. The oxygen carrier exhibited reproducible and stable reactivity behavior for both reducing and oxidizing periods in this temperature range. This characteristic makes the system an ideal oxygen-carrier material for CLOU. Moreover, the spinels in the CuxMn3_xO4 series are endowed with favorable physicochemical attributes (such as fast redox processes, high crushing strength, and demonstrated CLOU behavior) and may be viable alternatives to CuO–Cu2O and Mn2O3–Mn3O4 as potential CLOU materials.
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| 6. |
- Hedayati, Ali, 1984, et al.
(författare)
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Evaluation of Novel Ceria-Supported Metal Oxides As Oxygen Carriers for Chemical-Looping Combustion
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 51:39, s. 12796-12806
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Tidskriftsartikel (refereegranskat)abstract
- Oxygen carrier particles consisting of 60 wt % copper, iron, or manganese oxide supported on 40 wt % ceria (CeO2) or gadolinia doped-ceria (Ce0.9Gd0.1O1.9) have been manufactured and examined as oxygen carrier materials for chemical-looping combustion (CLC). Unlike conventional support materials, such as alumina (Al2O3), these ceria-based support materials are active under prevailing conditions in the fuel reactor and have the ability to participate in redox reactions. The oxygen carrier materials were synthesized via extrusion and were examined by successive oxidation and reduction cycles in a bench-scale fluidized bed reactor made of quartz. The experiments were conducted at 900 and 925 degrees C for copper-based materials, and at 950 degrees C for iron- and manganese-based materials. Methane or syngas (50% CO and 50% H-2) using a flow rate of 900 mL/min for Cu-based materials and 450 mL/min for Mn- and Fe-based materials was used as the fuel. For all experiments, 15 g of oxygen carrier was used. The oxidation was performed with a gas mixture of 5% O-2 and 95% N-2. The results show that CeO2 and Ce0.9Gd0.1O1.9 are viable support materials for the oxides of copper and iron. Moreover, the active particles supported on Ce0.9Gd0.1O1.9 were more reactive compared to those supported on CeO2. CH4 was completely converted to CO2 and H2O by CuO supported on Ce0.9Gd0.1O1.9, while the conversion of CH4 for Fe2O3 supported on Ce0.9Gd0.1O1.9 was as high as 90%. Ceria-supported Mn3O4 particles showed poor performance when CH4 was used as fuel. Syngas was fully converted to CO2 and H2O by all the oxygen carriers synthesized and examined in this work. The ability of CuO and Mn2O3 to release O-2 in gas phase when fluidized in inert background was also investigated; in the case of copper oxide, substantial oxygen release was observed. Analysis of fresh and used particles by X-ray diffractometry did not reveal the formation of any unexpected phases. All particles showed good fluidization properties with low attrition and little tendency toward agglomeration.
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| 7. |
- Leion, Henrik, 1976, et al.
(författare)
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Investigation on ceria- and doped ceria-supported oxygen carriers for CLC applications
- 2011
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Ingår i: Technical Workshop at the 3rd Meeting of the IEA-GHG Network on High Temperature Solids Looping Cycles.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In the area of chemical-looping combustion as a pathway to CO2 sequestration and subsequent storage, major efforts have concentrated on investigating various oxygen carriers supported on inert materials. So, it would be innovative to utilize supports that are participating in the combustion process and thus can act as a minor but additional oxygen carrier or as a facilitating oxidizing catalyst during CLC operation. One of these materials is cerium dioxide (ceria, CeO2), which is used extensively as an integral component of 3-way catalyst in automobiles. In order to exploit the synergy of a composite made up of the active carrier and the participating support, formulations consisting of two-phase mixtures of copper oxide, iron oxide and manganese oxide with pure or doped ceria were fabricated and evaluated for their reactivity in methane and syngas fuel streams. Relevant parameter of significance to CLC process, such as fuel conversion, oxygen release measurement, fluidization properties and, temperature variations during fuel and oxidation cycles, were examined.All the samples showed very good fluidization properties during tests without any agglomeration. Copper oxide-based oxygen carriers showed nearly full conversion of methane with high oxygen release and no sign of defluidization, while iron-based systems exhibited unusually high conversion of methane together with favourable reactivity during oxidation periods after the fuel cycles. The superiority of the GDC-supported materials over those supported on ceria could be interrelated to the better oxygen transport capability of the GDC support due to the oxygen ion vacancies in it by virtue of doping.
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| 8. |
- Mattisson, Tobias, 1970, et al.
(författare)
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Using CaxLa1-xMn1-yM'yO 3-δ as oxygen carriers for chemical-looping combustion
- 2012
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Ingår i: Conference Proceedings. 2012 AIChE Annual Meeting, AIChE 2012, Pittsburgh, 28 October - 2 November 2012. - 9780816910731
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Konferensbidrag (refereegranskat)abstract
- Oxygen carriers of the type CaxLa1-xMn 1-yM'yO3-δ (CLMM') were investigated as oxygen carrier materials. A matrix of potential substituted Ca xLa1-xMn1-y M'yO3-δ (M' = Fe, Ti, Cu, Mg) perovskites were synthesized using mechanical homogenization of primary solids in a rotary evaporator followed by drying and calcination. The resulting powders were subjected to particle fabrication via extrusion followed by crushing and sieving. The oxygen release properties and the reactivity with methane and syngas was investigated using a batch fluidized batch reactor made of quartz. A sample of 15 g of particles and a fuel flow of 450 Nml/min was used for all reactivity experiments. All of the materials showed high rates of oxygen release in gas phase at 900°C, exhibiting so called oxygen uncoupling behavior. In addition, the reactivity with methane was high, approaching 100% gas yield for all of the materials at 950°C, except the Cu-doped material which defluidized during reduction. All materials also exhibited high rate of oxidation. It can be concluded that the CLMM' materials reacted with fuel through both conventional chemical-looping (direct gas-solid reactions) and via chemical-looping with oxygen uncoupling (with the oxygen released from the particles). The stability of the materials was excellent with very little or no attrition. No agglomeration was noticed for most of these materials. High reactivity and very good oxygen uncoupling properties in combination with the low cost of the primary materials, make this system very interesting for chemical-looping combustion of different types of fuel.
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