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- Lyngfelt, Anders, 1955, et al.
(author)
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Dependence of Sulphur Capture Performance on Air Staging in a 12 MW Circulating Fluidised Bed Boiler
- 1993
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In: Gas Cleaning at High Temperatures, Eds. R. Clift and J.P.K. Seville, Blackie Academic & Professional, Glasgow, ISBN 0 7514 0178 1.. - 0751401781 ; , s. 470-491
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Book chapter (other academic/artistic)abstract
- Three cases of air staging were examined in a 12 MW circulating fluidised bed boiler: i) no staging, ii} normal staging and iii) intensified staging. The conditions inside the combustion chamber were investigated by zirconia cell measurements of the oxygen partial pressure, 0.35, 0.65 and 8 m above the bottom air distributor plate. A significant effect of the degree of staging was seen in the two lower locations: At 0.65 m height the fraction of time under substoichiometric conditions was low in the no-staging case (2-35%), at normal staging it was 70-90%, whereas at intensified staging it was 100Y.. At 0.35 m height, i.e. in the dense bed, a similar effect was seen, although the fraction of time under reducing conditions was lower. The fraction of time under reducing conditions was low in the top of the combustion chamber in all three cases . The increase in the fraction of time under reducing conditions with a higher degree of staging is associated with a decrease in sulphur capture. It is assumed that a release of SO2 from CaSO4 takes place during the transitions between oxidising and reducing conditions. Thus, the rapid alternations between oxidising and reducing conditions, as seen with the zirconia cell, offer an explanation of the reductive decomposition and, accordingly, of the dependence of sulphur capture on temperature and on the extent of staging.
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| 2. |
- Lyngfelt, Anders, 1955, et al.
(author)
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Low N2O, NO and SO2 emissions from circulating fluidized bed boilers
- 1995
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In: Proc. Int. Conf. Fluid. Bed Combustion. - 0197-453X. - 0791813053 ; 13, s. 1049-1057
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Conference paper (other academic/artistic)abstract
- A new method, reversed staging, for decreasing N2O without increasing the emission of the other pollutants, NOx and SO2, was investigated in the 12 MW circulating fluidized bed boiler at Chalmers University of Technology. It was possible to reduce the emission of N2O to one fourth (25 ppm), NO to half (about 40 ppm) compared to normal staging and normal temperature, without significantly affecting the sulphur capture efficiency (about 90%). Air staging, which is normally used in circulating fluidized bed boilers means that only a part of the combustion air, primary air, is added to the bottom zone, resulting in a lower oxygen concentration in the bottom part, while the secondary air results in more oxidizing conditions in the upper part of the combustion chamber and the cyclone. The principal idea of reversed staging is to reverse the conditions in top and bottom, i.e. to decrease the oxygen concentration in the upper part and to increase it in the bottom part. Such a reversal is accomplished by adding air in the bottom corresponding to an air ratio of approximately unity. No secondary air is added to the combustion chamber which means that the oxygen concentration will be low in the upper part of the combustion chamber and the cyclone. Air for final combustion is added in the cyclone outlet.
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| 3. |
- Lyngfelt, Anders, 1955, et al.
(author)
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Nitrous oxide from fluidized bed boilers
- 1998
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In: Ecyclopedia of Environment Analysis and Remeditation / Meyers, R.A.. ; 5, s. 3053-3062
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Book chapter (other academic/artistic)
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| 4. |
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| 5. |
- Åmand, Lars-Erik, 1957, et al.
(author)
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Fuel Loading of a Fluidized Bed Combustor Burning Bituminous Coal, Peat or Wood Chips
- 1997
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Reports (other academic/artistic)abstract
- Characterisation of gas- and particle phases in the combustion chamber of a commercial size circulating fluidized bed (CFB) boiler has been carried out during tests with three different fuels: bituminous coal, peat and wood chips, for typical operating conditions of a CFB boiler. The evaluation of the test results aims at presenting data on the fuel loading in parallel with the vertical profiles of oxygen concentration to be used for validation of models and for modelling of the fuel loading. The measurements show that the char loading during peat combustion is 13% of the amount found during coal combustion. Wood combustion results in even less char, only 3.5% of the concentration during coal combustion. For all fuels, more than 80% of the mass of char is retained in the lower part of the combustion chamber, below 2 meter from the bottom plate. The oxygen concentration profiles show large variations over the cross section for all three fuels, explained as an effect of insufficient penetration of secondary air in combination with partial plugging of some of the secondary air nozzles. In the peat and wood cases some of the variation over the cross section is caused by the high volatile content of the fuel in combination with a fuel supply from only one of the furnace walls.
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