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Träfflista för sökning "WFRF:(Leion Henrik 1976 ) ;pers:(Hallberg Peter 1984)"

Sökning: WFRF:(Leion Henrik 1976 ) > Hallberg Peter 1984

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1.
  • Hallberg, Peter, 1984-, et al. (författare)
  • A method for determination of reaction enthalpy of oxygen carriers for chemical looping combustion - Application to ilmenite
  • 2011
  • Ingår i: Thermochimica Acta. - 0040-6031. ; 524:1-2, s. 62-67
  • Tidskriftsartikel (refereegranskat)abstract
    • Chemical looping combustion (CLC) is a method for combustion with inherent CO(2) separation. In CLC an oxygen carrier supplies the oxygen necessary for fuel conversion. A method to determine the enthalpy of the reaction of oxygen carriers was developed. This method utilizes the fact that for many oxygen carriers the reaction enthalpy with CO is exothermic while it is endothermic with CH(4). By measuring the temperature change for reduction of different mixtures of CO and CH(4) it is possible to find the mixing ratio giving a thermally neutral reaction. From the known reaction enthalpies of CO and CH(4) with oxygen it is then possible to deduce the reaction enthalpy of the oxygen carrier. The reaction enthalpy for a NiO based oxygen carrier is estimated to 475 +/- 8 kJ (mol O(2))(-1). The expected value of 469 kJ (mol O(2))(-1) is in the error range and thus verified the method. The reaction enthalpies for three different ilmenite particles were also determined to 453 +/- 12 kJ (mol O(2))(-1) for synthetic ilmenite and 469 +/- 5 kJ (mol O(2))(-1) for natural ilmenite. A natural ilmenite that has previously been long term tested ended up with the reaction enthalpy 468 +/- 9 kJ (mol O(2))(-1).
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2.
  • Jing, Dazheng, 1986-, et al. (författare)
  • Effect of Production Parameters on the Spray-Dried Calcium Manganite Oxygen Carriers for Chemical-Looping Combustion
  • 2016
  • Ingår i: Energy & Fuels. - 0887-0624. ; 30:4, s. 3257-3268
  • Tidskriftsartikel (refereegranskat)abstract
    • The oxygen carrier CaMn0.9Mg0.1O3-delta was successfully tested in different chemical-looping units. High methane conversion and oxygen uncoupling properties have been found for this type of material. Most of the CaMn(0.9)Mg(0.1)O(3-delta)oxygen carrier particles tested so far have been produced' using the spray-drying method. In this work, the focus has been on studying the effects of production parameters on the properties of this important oxygen carrier. The effects of three production parameters, i.e., milling time, calcination temperature, and calcination time, were examined for the spray-dried particles. The time of ball milling for the slurry prepared for spray-drying was varied from 5 to 45 min, the calcination temperature from 1300 to 1350 degrees C, and the calcination time from 4 to 16 h. None of these parameters had any influence on the final crystalline phases of the oxygen carrier, yet some of the properties were clearly changed. The bulk density, crushing strength, and resistance against physical attrition can be enhanced by increasing the calcination temperature, calcination time, or milling time. Further, the BET specific surface area and porosity of the oxygen carrier particles decreased when the slurry was milled or particles were calcined for extended periods. The average methane conversion of the oxygen carrier varied in a wide range, from 99% to 55% at 950 degrees C, depending upon the production parameters used. However, no obvious influence of the examined production parameters was observed for the oxygen uncoupling property of the oxygen carrier, which may be due to the thermodynamic limitation during testing.
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3.
  • Schwebel, Georg, et al. (författare)
  • Kinetic description derived from fluidized bed experiments for ilmenite as oxygen carrier in chemical-looping combustion
  • 2011
  • Ingår i: Proceedings of the 36th International Technical Conference on Clean Coal and Fuel Systems.
  • Konferensbidrag (övrigt vetenskapligt)abstract
    • Chemical-looping combustion (CLC) is one of the most promising methods for CO2- capture from power production as well as from industrial applications. Most work on CLC so far has been oxygen carrier development carried out in laboratory scale units. In parallel, process modeling and simulation are important to gain information on possible reaction steps as well as for predicting the operation of large scale applications. Regarding the use of solid fuels in CLC, it is assumed that some oxygen carrier material will be lost by ash removal. Due to this fact, low cost and environmental sound materials are preferred. Natural minerals or ores as well as industrial residues can be promising oxygen carriers. For example the naturally occurring iron-titanium mineral ilmenite is one of the most used oxygen carriers in tests with solid fuels. In this work data from laboratory experiments is used to derive kinetics describing the conversion of a natural rock ilmenite while utilizing CO and H2 as fuel gases. The reactivity with CO and H2 is particularly important in solid fuel CLC since these are gasification intermediates. The ilmenite was provided by Titania A/S and has been used as oxygen carrier in former studies. The particles used whilst the experiments were sized in the range between 125 and 180 μm. The experimental setup consists of a tubular batch quartz glass reactor. The ilmenite sample was placed on a porous quartz plate in the center of the reactor. The reactor was heated to the desired temperature electrically. CO and H2 were used as fuel gases since this are the primary gasification gases. All experiments were carried out under fluidized bed conditions. Different fuel gas concentrations were achieved by diluting the fuel flow with nitrogen and the bed temperature was varied from 850 to 950°C. The fuel conversion rates were used to calculate kinetic parameters. A comparison with published parameters is accomplished. The results for H2 and CO as fuel also allow modeling of intermediate steps in CLC of solid fuels.
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