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- Johansson, Marcus, 1992, et al.
(author)
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A TEST IMPLEMENTATION OF THE CORE MANUFACTURING SIMULATION DATA SPECIFICATION
- 2007
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In: Proceedings of the 2007 Winter Simulation Conference in Washington D.C. USA, December 9-12 2007. ; , s. 1673-1681
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Conference paper (peer-reviewed)abstract
- This paper describes an effort of testing the Core Manufacturing Simulation Data (CMSD) information model as a neutral data interface for a discrete event simulation model developed using Enterprise Dynamics. The implementation is based upon a model of a paint shop at a Volvo Car Corporation plant in Sweden. The model is built for a Swedish research project (FACTS), which focuses on the work procedure of developing new and modified production systems. FACTS has found standardized simulation data structures to be of high interest to achieve efficient data collection in conceptual stages of production development programs. For the CMSD-development team, implementations serve as an approach to validate the structures in CMSD and to gather requirements for future enhancements. CMSD was originally developed to support job shops, but the results of this implementation indicate a good possibility to extend CMSD to also support flow shops.
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| 6. |
- Rydén, Magnus, 1975, et al.
(author)
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NiO supported on Mg-ZrO2 as oxygen carrier for chemical-looping combustion and chemical-looping reforming
- 2009
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In: Energy and Environmental Sciences. - : Royal Society of Chemistry (RSC). - 1754-5692 .- 1754-5706. ; 2:9, s. 970-981
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Journal article (peer-reviewed)abstract
- Oxygen-carrier particles consisting of 40 wt% NiO supported on 60 wt% Mg-stabilized ZrO2 were produced by freeze granulation and examined as oxygen carrier for chemical-looping applications. Firstly, the particles were examined by oxidation and reduction experiments in a batch fluidized-bed reactor. These experiments indicated very high reactivity with CH4 and low affinity for carbon formation. For highly oxidized particles the products were CO2 and H2O, while for reduced particles they were CO and H2. Secondly, the particles were examined by 40 hours of operation in a small circulating fluidized-bed reactor, using natural gas as fuel. For chemical-looping combustion, there was complete conversion of fuel into products with high selectivity towards CO2 and H2O. At 950ºC, a combustion efficiency of 99.3% was achieved, which is only 0.1%-point below the theoretical maximum, i.e. thermodynamic equilibrium. For chemical-looping reforming, the conversion of fuel was 99.9% or higher, with high selectivity towards CO and H2. Operating at the desired process parameters, which was a fuel reactor temperature of 950ºC and an air ratio of 0.30, worked flawlessly. When only natural gas was used as fuel there was slight formation of solid carbon in the fuel reactor. Adding 30 vol% steam to the fuel removed the carbon formation. The particles retained their physical and chemical structure reasonably well during operation. Approximately 5% of the particles added to the reactor were lost as fines during the first hours of operation. Further, the porosity of the particles increased somewhat during operation. The density was 10% lower for used particles, compared to fresh.
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| 7. |
- Abad, Alberto, 1972, et al.
(author)
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The use of iron oxide as oxygen carrier in a chemical-looping reactor
- 2007
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 86:7-8, s. 1021-1035
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Journal article (peer-reviewed)abstract
- Chemical-looping combustion (CLC) is a method for the combustion of fuel gas with inherent separation of carbon dioxide. This technique involves the use of two interconnected reactors, an air reactor and a fuel reactor. The oxygen demanded in the fuel combustion is supplied by a solid oxygen carrier, which circulates between both reactors. Fuel gas and air are never mixed and pure CO2 can be obtained from the flue gas exit. This paper presents the results from the use of an iron-based oxygen-carrier in a continuously operating laboratory CLC unit, consisting of two interconnected fluidized beds. Natural gas or syngas was used as fuel, and the thermal power was between 100 and 300 W. Tests were performed at four temperatures: 1073, 1123, 1173 and 1223 K. The prototype was successfully operated for all tests and stable conditions were maintained during the combustion. The same particles were used during 60 h of hot fluidization conditions, whereof 40 h with combustion. The combustion efficiency of syngas was high, about 99% for all experimental conditions. However, in the combustion tests with natural gas, there was unconverted methane in the exit flue gases. Higher temperature and lower fuel flows increase the combustion efficiency, which ranged between 70% and 94% at 1123 K. No signs of agglomeration or mass loss were detected, and the crushing strength of the oxygen carrier particles did not change significantly. Complementary experiments in a batch fluidized bed were made to compare the reactivity of the oxygen carrier particles before and after the 40 h of operation, but the reactivity of the particles was not affected significantly.
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| 9. |
- Andersson, Marcus, 1975, et al.
(author)
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Effect of molecular mobility of polymeric implants on soft tissue reactions: An in vivo study in rats
- 2008
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In: Journal of Biomedical Materials Research Part A. - : Wiley. - 1552-4965 .- 1549-3296. ; 84A:3, s. 652-660
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Journal article (peer-reviewed)abstract
- Although numerous different polymers are used as implants or otherwise studied for many other biotechnical applications, there is a lack of basic models that correlate polymer characteristics with foreign body reactions. This study aims at developing one such model by systematically studying surface molecular mobility of polymeric implants in soft tissues in vivo. Changing the length of the alkyl side chain of poly(alkyl methacrylates) (PAMAs), provides an interesting opportunity to study the surface molecular mobility with minimal changes of the hydrophobicity of the surface. Thus, in this study three different PAMAs, with increasingly surface mobility; poly (isobutyl methacrylate) (PIBMA), poly(butyl methacrylate) (PBMA), and poly(lauryl methacralate) (PLMA) along with pure titanium (Ti) substrates were implanted in the dorsum of Sprague-Dawley rats. Inflammatory cell recruitment, cell adhesion, and cytokine release were studied after 1, 3, and 28 days of implantation. Total number of inflammatory cells in the exudate was measured but no correlation between surface mobility and cell recruitment where found. However, the number of surface associated cells where significantly lower on the surfaces with high molecular mobility (PLMA and PBMA). The histological evaluation performed after 28 days revealed thicker fibrous capsule and a higher number of blood vessels on the low molecular mobility surface (PIBMA). After 28 days the cell activity was higher on the high molecular mobility surfaces (PLMA and PBMA) compared with PIBMA, based on the cytokine release. None of the surfaces induced any significant cell-death. On the basis of the results of this study we conclude that there is a significant difference in biological response to surfaces with different in molecular mobility. This might affect the wound healing process and the biocompatibility of biomaterials. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res, 2007 -------------------------------------------------------------------------------- Received: 13 March 2006; Revised: 15 December 2006; Accepted: 29 January 2007 Digital Object Identifier (DOI) 10.1002/jbm.a.31389 About DOI
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| 15. |
- Johansson, Marcus, 1975
(author)
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Screening of oxygen-carrier particles based on iron-, manganese-, copper- and nickel oxides for use in chemical-looping technologies
- 2007
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Doctoral thesis (other academic/artistic)abstract
- Capture and storage of carbon dioxide from combustion will likely be used in the future as a method of reducing emissions of greenhouse gases and thus be part of the overall strategy to stabilize the atmospheric levels of CO2. Chemical-looping combustion is a method of combustion where CO2 is inherently separated from the non-condensable components in the flue gas without the need for an energy intensive air separation unit. This is because nitrogen from the combustion air is never mixed with the fuel. Instead, oxygen carriers, in the form of metal oxide particles, circulate between two interconnected fluidized reactors and transfer oxygen from the air to the fuel through heterogeneous gas-solid redox reactions. The technology could also be adapted for the production of hydrogen from fossil fuels with CO2 separation, i.e. chemical-looping reforming.108 different oxygen-carriers based on iron-, manganese-, copper- and nickel oxides have been investigated. These carriers are prepared with inert material to increase the lifetime and performance of the particles. All particles but one have been produced by a freeze-granulation method. In order to optimize the performance of the particles, the sintering temperature of the particles was varied between 950°C and 1600°C. Normally particles of the size range of 125-180 m have been used for the reactivity investigations. Screening tests were performed in a laboratory fluidized-bed reactor of quartz placed in a furnace. The particles were exposed to an environment simulating a real chemical-looping combustor, by alternating between reducing (50% CH4 / 50 % H2O) and oxidizing conditions (5% O2 in N2). The temperature was varied in the range 600 – 950°C with most experiments conducted at 950°C. In addition the particles were characterized with respect to strength, physical appearance and chemical structure before and after the experiments. Some suitable oxygen carriers were investigated in more detail in the fluidized bed, and parameters such as reaction temperature, particle size, reducing gas and experimental method were varied. With respect to reactivity with methane, the different oxygen carriers can generally be ranked in the order nickel> copper> manganese> iron whereas the crushing strength roughly follows the opposite order. Several types of inert material were used in this work, and this was found to be a very important parameter. It was found that inert material based on alumina and zirconia in general resulted in promising oxygen carriers, whereas titania, silica and magnesia were less promising with respect to reactivity or lifetime of the particles. Using a low sintering temperature in preparation is associated with a high reactivity, but also a low strength. This is because the higher temperatures provoke a breakdown of the internal porous structure which also makes them denser. Twelve out of the initial 108 particles were not useful for different reasons, including melting, lack of structure and lack of reactivity due to formation of non-reducible species.The majority of the investigated oxygen carriers are well suited for chemical-looping combustion taking into consideration the important criteria of reactivity, high conversion of the fuel, relatively high strength and ability to withstand de-fluidization, agglomeration, fragmentation and abrasion.
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| 16. |
- Johansson, Marcus, 1975
(author)
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Selection of oxygen carriers for chemical-looping combustion using methane as a fuel
- 2005
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Licentiate thesis (other academic/artistic)abstract
- In order to meet new demands on clean energy producing technologies, chemical-looping combustion could play an important role. With this technique, CO2 from the flue gases can be separated and collected without excessive energy and efficiency penalty. This is because nitrogen from the combustion air is never mixed with the fuel. Instead, oxygen carriers, in the form of metal oxide particles, circulate between two interconnected fluidized reactors and transfer oxygen from the air to the fuel through solid-gas phase redox reactions. In this thesis, 90 different oxygen-carriers based on nickel-, manganese- and iron oxides have been investigated. These carriers are prepared with inert material to increase the lifetime and performance of the particles. With the exception of one oxygen carrier, all particles have been produced by a freeze-granulation method. The sintering temperature of the particles was between 950°C to 1600°C in order to optimize the strength and porosity. Normally particles of the size range of 125-180 m have been used for the reactivity tests. These tests were performed in a laboratory fluidized-bed reactor of quartz placed in a furnace holding 950°C. There the particles were exposed to an environment simulating a real chemical-looping combustor, by alternating between reducing (50% CH4 / 50 % H2O) and oxidizing conditions (5% O2 in N2). In addition the particles were characterized with respect to strength, physical appearance and chemical structure before and after the experiments. With respect to reactivity the different oxygen carriers with methane can generally be ranked in the order nickel> manganese> iron whereas the strength roughly follows the opposite order. The addition of inert is made to examine if the properties of the particles can be improved. It was found that inert material based on alumina and zirconia gives good results whereas titania, silica and magnesia were less successful. Another important parameter that affects the reactivity of the particles is the sintering temperature used as the last step in manufacturing. Using a low sintering temperature is associated with a high reactivity, but also a low strength. This is because the higher temperatures provoke a breakdown of the internal porous structure which also makes them denser. Ten out of the initial 90 particles were not useful for different reasons including melting, lack of structure and lack of reactivity due to formation of non-reducible species.The majority of the investigated oxygen carriers are well suited for chemical-looping combustion taking into consideration the important criteria of high reactivity (solids inventory in the fuel reactor less than 500 kg/MWCH4), high conversion of the fuel, relatively high strength and ability to withstand de-fluidization, agglomeration, fragmentation and attrition.
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| 18. |
- Johansson, Marcus, 1975, et al.
(author)
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Using continuous and pulse experiments to compare two promising nickel-based oxygen carriers for use in chemical-looping technologies
- 2008
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 87:6, s. 988-1001
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Journal article (peer-reviewed)abstract
- Chemical-looping technologies have obtained widespread recognition as power or hydrogen production units with inherent carbon capture in a future scenario where CO2 capture and storage (CCS) is reality. In this paper three different techniques are described; chemical-looping combustion and two categories of chemical-looping reforming. The three techniques are all based on oxygen carriers that are circulating between an air- and a fuel reactor, providing the fuel with undiluted oxygen. Two different oxygen carriers; NiO/NiAl2O4 (40/60 wt/wt) and NiO/MgAl2O4 (60/40 wt/wt) are compared. Both continuous and pulse experiments were performed in a batch laboratory fluidized bed working at 950 °C using methane as fuel. It was found that pulse experiments offer advantages in comparison to continuous experiments, particularly when evaluating suitable particles for autothermal chemical-looping reforming. Firstly, smaller conversion ranges can be investigated in more detail, and secondly, the onset and extent of carbon formation can be determined more accurately. Of the two oxygen carriers, NiO/MgAl2O4 offers several advantages at elevated temperatures, i.e. higher methane conversion, higher selectivity to reforming and lesser tendency for carbon formation.
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| 19. |
- Leion, Henrik, 1976, et al.
(author)
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The use of ilmenite as an oxygen carrier in chemical-looping combustion
- 2008
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In: Chemical Engineering Research and Design. - 0263-8762 .- 1744-3563. ; 86, s. 1017-1026
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Journal article (peer-reviewed)abstract
- The feasibility of using ilmenite as oxygen carrier in chemical-looping combustion has been investigated. Itwas found that ilmenite is an attractive and inexpensive oxygen carrier for chemical-looping combustion.Alaboratory fluidizedbed reactor system, simulating chemical-looping combustion by exposing the sample to alternating reducing and oxidizing conditions,was used to investigate the reactivity. During the reducing phase, 15 g of ilmenite with a particlesize of 125–180μm was exposed to a flow of 450mLn/min of either methane or syngas (50% CO, 50% H2) and during the oxidizing phase to a flow of 1000mLn/min of 5% O2 in nitrogen. The ilmenite particles showed no decrease in reactivity in the laboratory experiments after 37 cycles of oxidation and reduction. Equilibrium calculations indicate that the reduced ilmenite is in the form FeTiO3 and the oxidized carrier is in the form Fe2TiO5 +TiO2. The theoretical oxygen transfer capacity between these oxidation states is 5%. The same oxygen transfer capacity was obtained in the laboratory experiments with syngas. Equilibrium calculations indicate that ilmenite should be able to give high conversion of the gases with the equilibrium ratios CO/(CO2 + CO) and H2/(H2O+H2) of 0.0006 and 0.0004, respectively. Laboratory experiments suggest a similar ratio for CO. The equilibrium calculations give a reaction enthalpy of the overall oxidation that is 11% higher than for the oxidation of methane per kmol of oxygen. Thus, the reduction fromFe2TiO5 +TiO2 to FeTiO3 with methane is endothermic, but less endothermic compared to NiO/Ni and Fe2O3/Fe3O4, and almost similar to Mn3O4/MnO.
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| 20. |
- Lyngfelt, Anders, 1955, et al.
(author)
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Chemical-looping combustion - status of development
- 2008
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In: 9th International Conference on Circulating Fluidized Beds May 13 - May 16, Hamburg 2008.
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Conference paper (peer-reviewed)abstract
- Chemical-looping combustion (CLC) is a combustion technology with inherentseparation of the greenhouse gas CO2. The technique involves the use of a metal oxide as anoxygen carrier which transfers oxygen from combustion air to the fuel, and hence a directcontact between air and fuel is avoided. Two inter-connected fluidized beds, a fuel reactor andan air reactor, are used in the process. In the fuel reactor, the metal oxide is reduced by thereaction with the fuel and in the air reactor; the reduced metal oxide is oxidized with air. Theoutlet gas from the fuel reactor consists of CO2 and H2O, and almost pure stream of CO2 isobtained when water is condensed. Considerable research has been conducted on CLC in thelast years with respect to oxygen carrier development, reactor design, system efficiencies andprototype testing. In 2002 the process was a paper concept, albeit with some important butlimited laboratory work on oxygen carrier particles. Today more than 600 materials have beentested and the technique has been successfully demonstrated in chemical-looping combustors inthe size range 0.3 – 50 kW, using different types of oxygen carriers based on the metals Ni, Co,Fe, Cu and Mn. The total time of operational experience is more than a thousand hours. Fromthese tests it can be established that almost complete conversion of the fuel can be obtained and100% CO2 capture is possible. Most work so far has been focused on gaseous fuels, but thedirect application to solid fuels is also being studied. Moreover, the same principle of oxygentransfer is used in chemical-looping reforming (CLR), which involves technologies to producehydrogen with inherent CO2 capture. This paper presents an overview of the research performedon CLC and CLR highlights the current status of the technology.
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