| 1. |
- Andersson, Bengt-Åke, et al.
(författare)
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Bed-to-wall heat transfer in a 10m2 bubbling fluidized bed
- 1994
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Ingår i: Congreso Europeo de Fluidización. - 8478060936 ; 1, s. 251-260
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Konferensbidrag (refereegranskat)abstract
- The heat transfer is measured on the membrane tube wall in contact with a bubbling fluidized bed boiler. Measurements are carried out by heat transfer meters through holes in the wall both in the bed and above the bed in the splash zone and freeboard. Heat transfer coefficients are given and compared with previous measurements of material loss at the same wall and under the same conditions (typical for a fluidized bed boiler)
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| 2. |
- Andersson, Bengt-Åke, et al.
(författare)
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Experimental methods of estimating heat transfer in circulating fluidized bed boilers
- 1992
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Ingår i: International Journal of Heat and Mass Transfer. - 0017-9310. ; 35:12, s. 3353-3362
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Tidskriftsartikel (refereegranskat)abstract
- Four different experimental methods have been used for the estimation of the bed-to-membranewall heat transfer in a 12 MW,, circulating fluidized bed boiler. The methods are compared for a case ofnormal operating conditions and the measured heat transfer coefficients are presented. In the central partof the combustion chamber where most of the cooling surface is located, the cross-sectional averagesuspension density normally varies in the range of 10-20 kg m -’ and the heat transfer coefficient is around130 W m ’ K-’ with a scatter of + 15% due to the different methods. The methods are critically analyzedand the heat transfer data are compared with relevant literature data.
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| 3. |
- Andersson, Bengt-Åke, et al.
(författare)
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Fluidized bed combustion of coals and alternative fuels
- 1985
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Ingår i: Proc of the 8th International Conference on Fluidized-Bed Combustion held in Houston Texas USA, March 18-21, 1985. ; 2, s. 1019-1029
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Konferensbidrag (refereegranskat)abstract
- The 16 MW demonstration plant at Chalmers University of Technology was designed to burn coal but measures were taken also to allow the use of alternative fuels. Results of comparative tests, with bituminous coal and alternative fuels, brown coal, peat, and wood chips, are presented. The combustion characteristics of the various fuels are illustrated with temperature and heat flux profiles in the freeboard. It is found that the volatile fuels tend to burn to a large extent above the bed and secondary air is necessary to complete the combustion. However, -if secondary air is used, a combustion efficiency close to 100% is easily obtained. Bituminous coal, on the other hand, does not readily burn with a high combustion efficiency in the boiler used.
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| 4. |
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| 5. |
- Andersson, Bengt-Åke, et al.
(författare)
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Local lateral distribution of heat transfer on tube surface on membrane walls in CFB boilers
- 1993
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Ingår i: Proc of the 4th International Conference on Circulating Fluidized Beds. ; , s. 311-318
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Konferensbidrag (refereegranskat)abstract
- The wall to bed heat transfer was investigated in a 12 MWth CFB boiler at different locations in the combustion chamber and under various operating conditions. At high levels in the furnace the lateral distribution of heat flow to the tube and fin was found to be a result of radiation from the hot bed bulk, especially at low bulk densities. The local heat flow to the fin decreased considerably with decreasing height in contrast to the heat flow to the crest of the tube. This is due to the large down-flow of particles in the fin region and the growth of the boundary layer. The average heat transfer coefficient across the membrane wall was found to decrease with decreased bulk density, but at low bulk densities the decrease is very small since radiation dominates heat transfer.
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| 6. |
- Andersson, Bengt-Åke, et al.
(författare)
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Particle mass flux in the freeboard of a fluidized bed boiler
- 1989
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Ingår i: Powder Technology. - 1873-328X .- 0032-5910. ; 58:1, s. 25-37
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Tidskriftsartikel (refereegranskat)abstract
- The flux of descending particles has beenmeasured in the freeboard of a fluidized bedboiler. The lateral and vertical distributionsof the flux were studied and the influence ofthe superficial gas velocity and the static bedheight analyzed. A tube bundle located in thebed surface region made it possible to investigatethe effects of tubes on the entrainmentof particles from the surface of the bed.The particle flux was relatively constantacross the freeboard except near the wall,where it was about twice as large as the average.In the vertical direction, the flux decreasedexponentially with height exceptclose to the bed, where the rate of decay wasless than at higher elevations. The tube bundlewas found to inhibit the splashing of bedparticles when the bed is below the tubes.A model is used for the estimation of thevertical particle flux and concentrationprofiles in the freeboard. It is based on separatetreatment of small and coarse particlesand calculation of trajectories of ejected bedparticles. The calculated freeboard valuesdescribe the experimental data satisfactorilyexcept close to the bed, where a considerablediscrepancy is observed.
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| 7. |
- Andersson, Bengt-Åke, et al.
(författare)
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Use of a conductivity heat-flow meter in fluidised-bed boilers
- 1989
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Ingår i: Transactions of the Institute of Measurement and Control. - : SAGE Publications. - 1477-0369 .- 0142-3312. ; 11:2, s. 108-112
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Tidskriftsartikel (refereegranskat)abstract
- The usefulness of a conductivity type of heat-flow meter for measurements in fluidised-bed boilers is investigated. The design and the calibration of the meter are described. Results from measurements of the local heat tranfer at the walls of fluidised-bed boilers are presented. An error analysis shows that the accuracy of the heat-flow meter is +-9%.
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| 8. |
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| 9. |
- Andersson, Klas, 1977, et al.
(författare)
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Radiation intensity of lignite-fired oxy-fuel flames
- 2008
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777. ; 33:1, s. 67-76
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Tidskriftsartikel (refereegranskat)abstract
- The radiative heat transfer in oxy-fuel flames is compared to corresponding conditions in air-fuel flames during combustion of lignite in the Chalmers 100 kW oxy-fuel test facility. In the oxy-fuel cases the flue-gas recycle rate was varied, so that, in principle, the same stoichiometry was kept in all cases, whereas the oxygen fraction in the recycled flue-gas mixture ranged from 25 to 29 vol.%. Radial profiles of gas concentration, temperature and total radiation intensity were measured in the furnace. The temperature, and thereby the total radiation intensity of the oxy-fuel flames, increases with decreasing flue-gas recycle rate. The ratio of gas and total radiation intensities increases under oxy-fuel conditions compared to air-firing. However, when radiation overlap between gas and particles is considered the ratios for air-firing and oxy-fuel conditions become more similar, since the gas-particle overlap is increased in the CO2-rich atmosphere. A large fraction of the radiation in these lignite flames is emitted by particles whose radiation was not significantly influenced by oxy-fuel operation. Therefore, an increment of gas radiation due to higher CO2 concentration is not evident because of the background of particle radiation, and, the total radiation intensities are similar during oxy-fuel and air-fuel operation as long as the temperature distributions are similar.
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| 10. |
- Andersson, Klas, 1977, et al.
(författare)
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Radiation Intensity of Propane-Fired Oxy-Fuel Flames: Implications for Soot Formation
- 2008
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Ingår i: Energy & Fuels. ; 22:3, s. 1535-1541
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Tidskriftsartikel (refereegranskat)abstract
- The changes in the soot-related radiation intensity between two different oxy-fuel flames and an air-fired flame were investigated in a 100 kW oxy-fuel test unit firing propane. The oxy-fuel test cases with 21 and 27 vol % O2 in the recycled flue gas (RFG) were run with different amounts of dry RFG, which in principle only consisted of CO2 from combustion and some excess O2. The stoichiometric oxygen-to-fuel ratio was kept at 1.15 in all cases. Total radiation intensity was measured with a narrow angle radiometer. Temperature and gas composition measurements served as inputs to computations of gas radiation. A comparison of the computed gas radiation with the measured total radiation intensity enabled estimation of the radiation related to soot. Clear differences were observed in the amount of soot formed in the two oxy-fuel flames (also compared to the air flame). In the oxy-fuel flame with 21 vol % O2 in the RFG, soot formation is almost completely suppressed, but when the total flow through the burner is reduced by about 20% (by volume) (i.e., from 21 to 27 vol % O2 in the RFG), the amount of soot present in the flame becomes significant. This change in soot volume fraction affects the radiation emitted from the flames; images of the flames qualitatively confirm these differences in the flame luminosity. Thus, carbon dioxide not only increases the gas radiation, but it can also drastically influence soot formation and the radiation originating from soot during oxy-fuel combustion.
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