| 1. |
- Berguerand, Nicolas, 1978, et al.
(author)
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Chemical Looping Combustion of Solid Fuels in a 10 kWth Unit
- 2011
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In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 66:2, s. 181-191
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Journal article (peer-reviewed)abstract
- Chemical Looping Combustion of Solid Fuels in a 10 kW(th) Unit - The present study is based on previous results from batch experiments which were conducted in a 10 kW(th), chemical looping combustor for solid fuels using ilmenite, an iron titanium oxide, as the oxygen carrier with two solid fuels: a Mexican petroleum coke and a South African bituminous coal. These experiments involved testing at different fuel reactor temperatures, up to 1030°C, and different particle circulation rates between the air and fuel reactors. Previous results enabled modeling of the reactor system. In particular, it was possible to derive a correlation between measured operational data and actual circulation mass flow, as well as a model that describes the carbon capture efficiency as a function of the residence time and the char reactivity. Moreover, the kinetics of char conversion could be modeled and results showed good agreement with experimental values. The purpose of the present study was to complete these results by developing a model to predict the conversion of syngas with ilmenite in the fuel reactor. Here, kinetic data from investigations of ilmenite in TGA and batch fluidized bed reactors were used. Results were compared with the actual conversions during operation in this 10 kW(th) unit.
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| 2. |
- Bodin, Olle, et al.
(author)
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LES of the Exhaust Flow in a Heavy-Duty Engine
- 2014
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In: Oil & gas science and technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 69:1, s. 177-188
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Journal article (peer-reviewed)abstract
- The flow in the exhaust port and the exhaust manifold of a heavy-duty Diesel engine has been studied using the Large Eddy Simulation approach. Some of the flow characteristics in these components are: flow unsteadiness and separation combined with significant geometry-induced secondary flow motion. Detailed analysis of these features may add understanding which can be used to decrease the flow losses and increase the eciency of downstream components such as turbochargers and EGR coolers. Few LES studies of the flow in these components have been conducted in the past and this, together with the complexity of the flow are the motivations for this work. This paper shows that in the exhaust port, even global parameters like total pressure losses are handled better by LES than RANS. Flow structures of the type that afect both turbine performance and EGR cooler efficiency are generated in the manifold and these are found to vary significantly during the exhaust pulse. This paper also clearly illustrates the need to make coupled simulations in order to handle the complicated boundary conditions of these gas exchange components.
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| 3. |
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| 6. |
- Jerndal, Erik, 1980, et al.
(author)
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Using Low-Cost Iron-Based Materials as Oxygen Carriers for Chemical Looping Combustion
- 2011
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In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 66:2, s. 235-248
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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.
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| 7. |
- Leion, Henrik, 1976, et al.
(author)
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Chemical Looping Combustion of Solid Fuels in a Laboratory Fluidized-bed Reactor
- 2011
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In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 66:2, s. 201-208
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Journal article (peer-reviewed)abstract
- Chemical Looping Combustion of Solid Fuels in a Laboratory Fluidized-bed Reactor - When using solid fuel in a chemical looping system, the char fraction of the fuel needs to be gasified before syngas react with the oxygen carrier. This can be done inside the fuel reactor with fuel and oxygen carriers well mixed, and, since this gasification is comparably slow, this will be the time limiting step of such a system. An option is to use an oxygen carrier that is able to release gas-phase oxygen which can react with the fuel by normal combustion giving a significantly faster overall fuel conversion. This last option is generally referred to as Chemical Looping combustion with Oxygen Un-coupling (CLOU). In this work, an overview is given of parameters that affect the fuel conversion in laboratory CLC and CLOU experiments. The main factor determining the fuel conversion, in both CLC and CLOU, is the fuel itself. High-volatile fuels are generally more rapidly converted than low volatile fuels. This difference in fuel conversion rate is more pronounced in CLC than in CLOU. However, the fuel conversion is also, both for CLC and CLOU, increased by increasing temperature. Increased steam and SO(2) fraction in the surrounding gas will also enhance the fuel conversion in CLC. CO(2) gasification in CLC appears to be very slow in comparison to steam gasification. H(2) can inhibit fuel gasification in CLC whereas CO did not seem to have any effect. Possible deactivation of oxygen carriers due to SO(2) or ash also has to be considered.
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| 8. |
- Lyngfelt, Anders, 1955
(author)
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Oxygen Carriers for Chemical Looping Combustion-4000 h of Operational Experience
- 2011
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In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 66:2, s. 161-172
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Journal article (peer-reviewed)abstract
- Oxygen Carriers for Chemical Looping Combustion - 4000 h of Operational Experience - Chemical Looping Combustion (CLC) is a new combustion technology with inherent separation of the greenhouse gas CO(2). The technology involves the use of a metal oxide as an oxygen carrier which transfers oxygen from combustion air to the fuel, and hence a direct contact between air and fuel is avoided. Two interconnected fluidized beds, a fuel reactor and an air reactor, are used in the process. The outlet gas from the fuel reactor consists of CO(2) and H(2)O, and the latter is easily removed by condensation. Considerable research has been conducted on CLC in the last years with respect to oxygen carrier development, reactor design system efficiencies and prototype testing. Today, more than 700 materials have been tested and the technology has been successfully demonstrated in chemical looping combustors in the size range 0.3-140 kW, using different types of oxygen carriers based on oxides of the metals Ni, Co, Fe, Cu and Mn. The total time of operational experience is more than 4000 hours. From these tests, it can be established that almost complete conversion of the fuel can be obtained and 100% CO(2) capture is possible. Most work so far has been focused on gaseous fuels, but the direct application to solid fuels is also being studied. This paper presents an overview of operational experience with oxygen carriers in chemical looping combustors.
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| 9. |
- Ma, Zetao, et al.
(author)
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Convex modeling for optimal battery sizing and control of an electric variable transmission powertrain
- 2019
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In: Oil and Gas Science and Technology. - : EDP Sciences. - 1294-4475 .- 1953-8189. ; 74
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Journal article (peer-reviewed)abstract
- Hybrid Electric Vehicles are being considered a convenient intermediate product in the conversion process from conventional to pure electric vehicles, due to their compromise on cost, fuel consumption, and driving range. Convex modeling steps for the problem of optimal battery sizing and energy management of a plug-in hybrid electric vehicle with an electric variable transmission are presented. Optimal energy management was achieved by a switched model control, with driving modes identified by the engine on/off state. In pure electric mode, convex optimization was employed to find the optimal torque split between two electric machines, to maximize powertrain efficiency. In hybrid mode, optimization was carried out in a bilevel program. One level optimizes speed of a compound unit that includes the engine and electric machines. Another level optimizes the power split between the compound unit and the battery. The proposed method is used to minimize the total cost of ownership of a passenger vehicle for a daily commuter, including costs for battery, fossil fuel and electricity.
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| 10. |
- Monot, F., et al.
(author)
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The NILE Project - Advances in the Conversion of Lignocellulosic Materials into Ethanol
- 2013
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In: Oil & Gas Science and Technology. - : EDP Sciences. - 1294-4475. ; 68:4, s. 693-705
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Journal article (peer-reviewed)abstract
- NILE ("New Improvements for Lignocellulosic Ethanol") was an integrated European project (2005-2010) devoted to the conversion of lignocellulosic raw materials to ethanol. The main objectives were to design novel enzymes suitable for the hydrolysis of cellulose to glucose and new yeast strains able to efficiently converting all the sugars present in lignocellulose into ethanol. The project also included testing these new developments in an integrated pilot plant and evaluating the environmental and socio-economic impacts of implementing lignocellulosic ethanol on a large scale. Two model raw materials - spruce and wheat straw - both preconditioned with similar pretreatments, were used. Several approaches were explored to improve the saccharification of these pretreated raw materials such as searching for new efficient enzymes and enzyme engineering. Various genetic engineering methods were applied to obtain stable xylose- and arabinose-fermenting Saccharomyces cerevisiae strains that tolerate the toxic compounds present in lignocellulosic hydrolysates. The pilot plant was able to treat 2 tons of dry matter per day, and hydrolysis and fermentation could be run successively or simultaneously. A global model integrating the supply chain was used to assess the performance of lignocellulosic ethanol from an economical and environmental perspective. It was found that directed evolution of a specific enzyme of the cellulolytic cocktail produced by the industrial fungus, Trichoderma reesei, and modification of the composition of this cocktail led to improvements of the enzymatic hydrolysis of pretreated raw material. These results, however, were difficult to reproduce at a large scale. A substantial increase in the ethanol conversion yield and in specific ethanol productivity was obtained through a combination of metabolic engineering of yeast strains and fermentation process development. Pilot trials confirmed the good behaviour of the yeast strains in industrial conditions as well as the suitability of lignin residues as fuels. The ethanol cost and the greenhouse gas emissions were highly dependent on the supply chain but the best performing supply chains showed environmental and economic benefits. From a global standpoint, the results showed the necessity for an optimal integration of the process to co-develop all the steps of the process and to test the improvements in a flexible pilot plant, thus allowing the comparison of various configurations and their economic and environmental impacts to be determined.
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