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| 2. |
- 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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| 3. |
- Berguerand, Nicolas, 1978, et al.
(author)
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Chemical-Looping Combustion of Petroleun Coke using Ilmenite in a 10 kWth unit - High Temperature Operation
- 2009
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In: Energy & Fuels. - 1520-5029 .- 0887-0624. ; 23:10, s. 12-
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Journal article (peer-reviewed)abstract
- Chemical-looping combustion with solid fuel was investigated in a 10 kWth chemical-looping combustor using a petroleum coke as fuel and ilmenite, an iron titanium oxide, as oxygen-carrier. The fuel reactor was fluidized by steam to gasify the coke and the oxygen carrier reacts with the gasification products CO and H2. The temperature in the fuel reactor was normally 950°C. Testing involved variation of operational parameters such as particle circulation, fluidizing velocity in the fuel reactor and most important, fuel reactor temperature. In particular, successful testing was performed at a fuel reactor temperature of 1000°C without any operation difficulty and the positive effect of temperature on carbon capture and solid fuel conversion was verified. The oxygen demand corresponds to the fraction of oxygen lacking to achieve full gas conversion and averaged at 32%, due to presence of CH4, CO, H2 and H2S at the outlet of the fuel reactor. During these tests, the CO2/CO ratios usually reached in the fuel reactor ranged between 8 and 9 at stable operation. Most of the oxygen demand is associated with the volatiles released from the fuel and never in contact with oxidized particles. Indeed, investigation based on gas concentration measurements during transitions phases, which correspond to start respectively stop of fuel addition, indicate that as much as 80% of the total oxygen demand can be associated with the volatiles. The oxygen demand for the actual char oxidation is estimated to be 5-9%, if sulphur is excluded.
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| 4. |
- Berguerand, Nicolas, 1978, et al.
(author)
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Design and Operation of a 10 kWth Chemical-Looping Combustor for Solid Fuels - Testing with South African Coal
- 2008
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In: Fuel. - : Elsevier BV. - 0016-2361. ; 87:12, s. 14-2726
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Journal article (peer-reviewed)abstract
- This paper presents the results obtained for the operation of a 10 kWth chemical-looping combustor using a South African coal as the solid fuel and an oxygen carrier of ilmenite, a natural iron titanium oxide. A chemical-looping combustor for solid fuels was designed and built. It consists of two interconnected fluidized beds, an air reactor where the oxygen carrier is oxidized and a fuel reactor where the coal is gasified by steam and the syn-gases react with the oxygen carrier. A constant coal flow corresponding to a thermal power of 3.3 kW was introduced into the fuel reactor. The tests were conducted at temperatures above 850°C and for a total test duration of 22 h. The particle integrity of ilmenite and the particle circulation between the two reactors were investigated and verified. The effects of particle circulation on coal conversion, gas conversion of the fuel reactor and carbon separation or CO2 capture between the air and fuel reactors were investigated. The actual CO2 capture ranged between 82.5 and 96% while the gas conversion from the fuel reactor was in the range 78 to 81%, based on measurements of unconverted CO and CH4.
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| 5. |
- Berguerand, Nicolas, 1978, et al.
(author)
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Operation in a 10 kWth Chemical-Looping Combustor for Solid Fuel - Testing with a Mexican Petroleum Coke
- 2009
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In: Energy Procedia: 9th International Conference on Greenhouse Gas Control Technologies, GHGT-9; Washington DC; United States; 16 November 2008 through 20 November 2008. - : Elsevier BV. - 1876-6102. ; 1:1, s. 407-414
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Conference paper (peer-reviewed)abstract
- Solid fuel chemical-looping combustion was investigated in a 10 kWth combustor using petroleum coke as fuel and ilmenite as oxygen carrier. Testing involved operational parameters variations, such as particle circulation, fluidizing velocities, fuel load and fuel reactor temperature.Key parameters indicating the performance include CO2 capture, solid fuel and gas conversions from the fuel reactor. The CO2 capture averaged at 75%, the solid fuel conversion at 65-70% while incomplete gas conversion led to an oxygen demand averaging at 29-30%, due to presence of CH4, CO, H2 and H2S. Effect of fuel reactor temperature on the solid fuel conversion was verified.
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| 6. |
- Berguerand, Nicolas, 1978, et al.
(author)
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The Use of Petroleum Coke as Fuel in a 10 kWth Chemical-Looping Combustor
- 2008
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In: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 2:2, s. 11-179
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Journal article (peer-reviewed)abstract
- Tests were made in a 10 kWth chemical-looping combustor with a petroleum coke as the solid fuel and the oxygen carrier ilmenite, an iron titanium oxide. The fuel reactor is fluidized by steam and the oxygen carrier reacts with the volatiles released as well as the gasification intermediates CO and H2. A constant fuel flow corresponding to a thermal power of 5.8 kW was introduced into the fuel reactor and a total of 11 h of operation was reached. The effects of particle circulation and carbon stripper operation on solid fuel conversion, conversion of gas from the fuel reactor and CO2 capture were investigated. The actual CO2 capture ranged between 60% and 75% while the solid fuel conversion was in the range 66 to 78%. The low values of solid fuel conversion reflect loss of char due to low efficiency of the fuel reactor cyclone. The incomplete conversion of the gas from the fuel reactor is expressed as oxygen demand. The oxygen demand corresponds to the fraction of oxygen lacking to achieve full gas conversion and was typically 25%, due to presence of CH4, CO and H2 from the fuel reactor. Typical ratios of CH4, CO and H2 over the total gaseous carbon from the fuel reactor are respectively 5, 10 and 25%. Low loss of non-combustible fines from the system indicates very low attrition of the oxygen carrier.
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| 7. |
- Berntsson, Thore, 1947, et al.
(author)
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Towards Sustainabel Oil Refinery - Pre-study for larger co-operation project
- 2008
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Reports (other academic/artistic)abstract
- In this report, the Chalmers EnergiCentrum (CEC) presents the results of a pre-study commissioned by Preem relating to the effective production of future vehicle fuels.This pre-study was made up of three studies focusing on energy streamlining, the utilisation of waste heat and carbon-dioxide separation and biorefinement relating to the gasification and hydration of vegetable oils. One of the common starting points for these studies was the current situation at the Preem refineries in Göteborg and Lysekil from where the measurement data were obtained and analysed. The report summarises the knowledge situation based on current research in the individual technical fields. The results present some interesting future opportunities for developing the sustainable production of future vehicle fuels. The sections vary, as the areas that have been examined differ and the sections have been written by different people. The reports ends with some joint conclusions and a number of questions which could be included and answered in a more extensive future main study, as part of a developed research partnership between Preem and the Chalmers University of Technology. The preliminary results of this work were analysed with the client at workshops on 1 October and 29 November 2007. The report is written in English combined with an extensive summary in Swedish including a proposal on a future main study. The study was conducted by the Chalmers EnergiCentrum (CEC), in collaboration with a number of researchers in the CEC’s network. They included Thore Berntsson, Jessica Algehed, Erik Hektor and Lennart Persson Elmeroth, all from Heat and Power Technology, Börje Gevert, Chemical and Biological Engineering, Tobias Richards, Forest Products and Chemical Engineering, Filip Johnsson and Anders Lyngfelt, Energy Technology, and Per-Åke Franck and Anders Åsblad, CIT Industriell Energianalys AB. The client, Preem, was represented by Bengt Ahlén, Sören Eriksson, Johan Jervehed, Bertil Karlsson, Gunnar Olsson, Ulf Kuylenstierna, Stefan Nyström, Martin Sjöberg and Thomas Ögren. Tobias Richards was responsible for compiling the report and Bertil Pettersson was the project manager.
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| 8. |
- Cho, Paul In-Young, 1970, et al.
(author)
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Carbon Formation on Nickel and Iron Oxide-Containing Oxygen Carriers for Chemical-Looping Combustion
- 2005
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 44:4, s. 668-676
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Journal article (peer-reviewed)abstract
- For combustion with CO2 capture, chemical-looping combustion with inherent separation of CO2 is a promising technology. Two interconnected fluidized beds are used as reactors. In the fuel reactor, a gaseous fuel is oxidized by an oxygen carrier, e.g., metal oxide particles, producing carbon dioxide and water. The reduced oxygen carrier is then transported to the air reactor, where it is oxidized with air back to its original form before it is returned to the fuel reactor. Carbon deposition on oxygen-carrier particles was investigated to assess whether it could have adverse effects on the process. The oxygen-carrier particles used were based on oxides of nickel and iron and produced by freeze granulation. They were sintered at 1300 degreesC for 4 h and sieved to a size range of 125-180 mum. The study of carbon deposition was performed in a laboratory fluidized-bed reactor, simulating a chemical-looping combustion system by exposing the sample to alternating reducing and oxidizing conditions. The particles with nickel oxide were tested at 750, 850, and 950 degreesC, and the particles with iron oxide at 950 degreesC. On the oxygen carrier with nickel oxide, only minor amounts of carbon formed during most of the reduction. However, when more than 80% of the oxygen available was consumed, significant carbon formation started. The formation of carbon was also clearly correlated to low conversion of the fuel. No carbon was formed on the oxygen carrier based on iron oxide. The interpretation for the actual application of this process is that carbon formation should not be a problem, because the process should be run under conditions of high conversions of the fuel.
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| 9. |
- Cho, Paul In-Young, 1970, et al.
(author)
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Defluidization conditions for fluidized-bed of iron, nickel, and manganese oxide containing oxygen-carriers for chemical-looping combustion
- 2006
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In: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 1520-5045 .- 0888-5885. ; 45:3, s. 968-977
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Journal article (peer-reviewed)abstract
- For combustion with CO2 capture, chemical-looping combustion with inherent separation Of CO2 is a promising technology. Chemical-looping combustion uses oxygen carriers that are composed of metal oxide to transfer oxygen from the combustion air to the fuel. The defluidization of oxygen-carrier particles was investigated to improve the understanding of when particle agglomeration may occur. The study was made in a laboratory fluidized-bed reactor at 950 degrees C, simulating a chemical-looping combustion system by exposing the sample to reducing and oxidizing conditions in an alternating manner. The oxygen-carrier particles used were based on oxides of iron, nickel, and manganese and produced by freeze granulation. For iron oxide particles, there was no defluidization of the bed when the content of available oxygen in the particle was high. The defluidization occurred during the oxidation period after long reduction periods, in which a significant reduction of the magnetite to wustite occurred. This is an important observation, because the reduction to wustite is not expected in chemical-looping combustion with high fuel conversion. Thus, laboratory experiments with iron oxide performed with long reduction times may give an unduly exaggerated impression of the risks of agglomeration. For nickel oxide, the defluidization was dependent on the sintering temperature with no defluidization in experiments conducted with particles sintered at 1300 and 1400 degrees C. The nickel oxide particles that were sintered at 1500 degrees C only defluidized once in a total of 49 cycles, whereas the particles that were sintered at 1600 degrees C defluidized already in the first cycle. For the nickel oxide particles, it was not possible to see any effect of the length of the reducing period on the defluidization. There was no defluidization of the manganese oxide particles. The defluidization of the bed leads to agglomeration for the iron oxide particles, but not for the particles of nickel oxide, where the bed was still loosely packed. Carbon was formed on the particles based on nickel oxide and manganese oxide.
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| 10. |
- Eide, Lars, et al.
(author)
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Novel Capture Processes
- 2005
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In: Oil and Gas Science and Technology. ; 60:3, s. 497-508
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Journal article (peer-reviewed)
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