| 1. |
- Fleig, Daniel, 1980, et al.
(författare)
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Sulphur chemistry in oxy-fuel combustion
- 2009
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Ingår i: VDI-Berichte. - 0083-5560. - 9783180920566 ; 2056:24. Deutscher Flammentag, s. 289-294
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 2. |
- Fleig, Daniel, 1980, et al.
(författare)
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The Sulphur Mass Balance in Oxy-Fuel Combustion of Lignite
- 2009
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Ingår i: 1st OXYFUEL COMBUSTION CONFERENCE: September 8-11, 2009, Cottbus, Germany.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work presents an experimental study of the sulphur chemistry in oxy-fuel combustion of pulverized lignite. It has been observed that the emission of sulphur dioxide (SO2) by unit energy supplied is lower in oxy-fuel combustion than in air combustion [1-5] but the reason for this is not clear. In order to validate previous work and to clarify this difference the present work compares the amount of emitted SO2 in air and oxy-fuel combustion (wet and dry flue-gas recycle). Furthermore, the amounts of sulphur in the ash and in the water of the flue-gas condenser were determined to make a mass balance and to verify the measured amount of SO2 in the flue gas.
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| 3. |
- Gimenez-López, Jorge, et al.
(författare)
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NO2 Emissions in Oxy-Fuel Combustion
- 2011
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Ingår i: Proceedings of the 5th International Conference on Clean Coal Technologies.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Few studies are available about the chemistry of NO2 in oxy-fuel combustion, despite the thought that the formation of NO2 in oxy-fuel plants is higher than in air combustion. A kinetic modeling study of the NO2 formation and reduction process in oxy-fuel combustion is performed. Calculations are based on experiments carried out in a 100 kW test unit fired with pulverized coal. The modeling approach is performed in order to assimilate the process as a gas-phase flow reactor system. NO2 is mainly formed through the HO2 mechanism. In the high temperature region, all NO2 is reduced, but the low temperatures favor the formation of NO2 in the final section of the boiler. SO2 has an important effect on the in-furnace NO2 formation, while the influence of O2 is minor. According to the model, a much higher formation of NO2 is attained in oxy-fuel compared to air combustion, while similar NOx reduction efficiencies are found with recycled-NO2 than with recycled-NO.
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| 4. |
- Kuehnemuth, Daniel, 1979
(författare)
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Combustion and Nitrogen Chemistry in Oxy-Fuel Flames
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Oxy-fuel combustion is a Carbon Capture and Storage (CCS) technology that recently has shown afast progress towards the industrial scale application. In oxy-fuel combustion, oxygen instead of air isused as oxidizer to burn the fuel. The oxygen is mixed with recycled flue-gas in order to control theoverall combustion and heat transfer conditions. The resulting combustion atmosphere has asignificant impact on the combustion chemistry and its interaction with the nitrogen chemistry. Thiswork investigates the influence of oxy-fuel operation on the formation and oxidation of CO and thenitrogen chemistry with special attention on the reburning conditions. An indication of the effects ofthe CO2-rich atmosphere on the combustion chemistry in oxy-fuel flames is the elevated CO-peakconcentration compared to air fired flames. This work characterizes the reactions with CO2 whichform CO in oxy-fuel flame by modeling. The reduction of nitrogen oxides are investigated bycombining a similar modeling approach with experimental work at the Chalmers 100 kWth oxy-fuelunit.The model results show that CO formation in gaseous fired oxy-fuel flames is dominated by thereaction between CO2 and H-radicals. In oxy-fuel combustion of pulverized lignite, char gasificationby CO2 can be the dominating reason for an increased CO formation. However, the importance ofgasification is dependent on char particle temperature (which is related to char properties such asreactivity and particle size), as well as on the mixing conditions between fuel and oxidizer.The results from the propane fired reburning experiments show that the combustion chemistry of anoxy-fuel flame is disadvantageous for NO reburning compared to an air flame. The reduction of finalNO emissions [mg/MJ] to about 30% of those observed in air firing is caused by the recycle. Theeffect of the recycle ratio is particularly significant for cases with low reduction efficiencies in theflame.
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| 5. |
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| 6. |
- Kuehnemuth, Daniel, 1979, et al.
(författare)
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NOX reburning in oxy-fuel combustion - An experimental investigation
- 2010
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Ingår i: 27th Annual International Pittsburgh Coal Conference 2010, PCC 2010; Istanbul; Turkey; 11 October 2010. - 9781617823213 ; 1, s. 256-270
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This work investigates the reburning reduction of nitric oxide (NO) in a 100 kW propane-fired oxyfuel flame. The conducted experiments include a comprehensive parameter study: NO was injected into the recycled flue-gas, the inlet oxygen concentration was varied between 25 and 37 vol. % and the stoichiometric ratios at the burner inlet ranged from 0.7 and 1.15. The respective influence of inlet oxygen concentration and burner stoichiometry on once-through and total reduction of NO was measured. Furthermore, concentration and temperature in the furnace were mapped to identify important differences between oxy and air-fired conditions. The furnace measurements show that the peak concentration of carbon monoxide may be more than twice as high as in air-fired conditions. The formation paths of CO and its influence on the NO x chemistry are therefore discussed. The results of the parameter study show that reburning is favored by decreased burner stoichiometry. The effect of inlet oxygen concentration on once-through NO reduction is of minor importance. Changes in stoichiometry and oxygen inlet concentration are associated with changes in recycle ratio. The influence of the recycle ratio on the NO reduction is of great importance and is investigated as separate parameter.
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| 7. |
- Kuehnemuth, Daniel, 1979, et al.
(författare)
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On the carbon monoxide formation in oxy-fuel combustion-Contribution by homogenous and heterogeneous reactions
- 2014
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Ingår i: International Journal of Greenhouse Gas Control. - : Elsevier BV. - 1750-5836. ; 25, s. 33-41
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Tidskriftsartikel (refereegranskat)abstract
- This work investigates CO formation mechanisms under oxy-fuel combustion conditions. The importance of the possible explanations for increased inflame CO concentrations in oxy-fuel flames compared to air-firing are discussed. A model based on a detailed gas-phase reaction mechanism is combined with a lignite char combustion model, including apparent surface kinetics for oxidation as well as carbon dioxide and steam gasification and implication of diffusion limitation. In agreement with other authors work, it is concluded that in gas-fired oxy-fuel flames the CO formation is promoted by a homogenous reaction between hydrogen radicals and CO2. Additionally, this work concludes that in lignite-fired oxy-fuel combustion, this gaseous reaction route is of less importance. In oxy-lignite flames, CO2 gasification is the largest contributor to the increased CO formation compared to air firing. The substitution of CO2 with steam in the oxidizer during wet oxy-fuel combustion has moderate influence on the CO2 gasification, whereas the homogenous CO formation is strongly reduced.
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| 8. |
- Kuehnemuth, Daniel, 1979, et al.
(författare)
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Reburning of Nitric Oxide in Oxy-Fuel Firing-The Influence of Combustion Conditions
- 2011
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Ingår i: Energy & Fuels. - : American Chemical Society (ACS). - 1520-5029 .- 0887-0624. ; 25:2, s. 624-631
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Tidskriftsartikel (refereegranskat)abstract
- Experiments were carried out to obtain data on the efficiency of nitric oxide (NO) reduction by reburning under oxy-fuel conditions. The work was carried out in a 100 kW test facility fired with propane. The data were analyzed by means of a combustion model, which included a detailed description of the reburning chemistry. The importance of several combustion parameters on the reburning efficiency was studied: inlet oxygen concentration, flue gas recycle ratio, temperature, and stoichiometric ratio. The inlet oxygen concentration was kept between 25 and 37 vol % and the burner stoichiometric ratio between 0.7 and 1.15. NO was injected in the oxidizer. As expected, similar to air-firing, reburning in oxy-fuel is favored by substoichiometric conditions. A decrease in combustion temperature, caused by a lowered stoichiometric ratio, is shown to be advantageous for reduction of NO under oxy-fuel conditions. The effect of inlet oxygen concentration on reburning is not significant as long as the combustion conditions are fuel-lean. However, the amount of recycled flue gas, which increases with decreasing oxygen content, significantly improves the total reduction. Instead, when the stoichiometric ratio is decreased, the recycle flow of the flue gas is reduced, which, to some extent, counteracts the otherwise positive effect of fuel-rich conditions in the flame zone in oxy-fuel conditions. Thus, during oxygen-rich combustion, the total reburning efficiency in oxy-fuel combustion is superior to once-through reburning in air-firing, but during substoichiometric conditions, the reduction in air and oxy-fuel combustion is comparable.
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| 9. |
- Normann, Fredrik, 1982, et al.
(författare)
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Carbon Monoxide Formation in Oxy-Fuel Combustion
- 2013
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Ingår i: The Proceedings of the 38th International Technical Conference on Clean Coal & Fuel Systems, June 2-6 2013, Clearwater, Florida, USA.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Compared to air-fired flames, an increased in-flame CO concentration has been observed in oxy-fuel combustion. This work analyses the possible explanations for this increase in CO formation. A combustion model is used to investigate the impact of critical combustion parameters on the CO formation routes within a gaseous and lignite fired oxy-fuel flame. In gas-fired oxy-fuel flames the CO formation is promoted by a homogenous reaction between hydrogen radicals and CO2. However, in lignite-fired oxy-fuel combustion, the gaseous reaction route is of less importance to inflame CO formation. Instead CO2 gasification is the largest contributor to the increased CO formation compared to air firing. The substitution of CO2 with steam in the oxidizer during wet oxy-fuel combustion has moderate influence on the CO2 gasification whereas the homogenous CO formation is strongly reduced.
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