| 1. |
- Johnsson, Filip, 1960, et al.
(författare)
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Characteristics of the formation of particle wall-layers in CFB boilers
- 1995
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Ingår i: Proc of the 2nd International Conference on Multiphase Flow. ; 3, s. FB1-25-FB1-32-
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Konferensbidrag (refereegranskat)abstract
- The character of the vertical two-phase flow in circulating fluidized bed (CFB)boiler furnaces is compared with results from small CFB risers presented in literature. The particle flow in furnaces as well as in the smaller risers shows a core/wall-layer structure. In the CFB boilers the particle flow pattern develops up through the furnace with the major back-flow caused by separation to the furnace walls. Both the particle wall-layer thickness and the downward flux within this layer increase downwards along the furnace walls. In the smaller units this downward increase is either absent or much smaller, a consequence of a more developed particle flow profile, which, typically, is parabolic in shape.
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| 2. |
- Johnsson, Filip, 1960, et al.
(författare)
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Optical and momentum probe measurements in a CFB boiler
- 1996
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Ingår i: Proc of the 5th International Conference on Circulating Fluidized Bed. ; , s. 652-657
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Konferensbidrag (refereegranskat)abstract
- Methods for the characterization of the two-phase flow in the transport zone of circulating fluidized bed (CFB) boilers are discussed based on measurements of fluctuations in local solids concentration and momentum flux using an optimum probe and a momentum probe. Both probes were designed to withstand the environment inside a furnace during combustion. The dynamic information on the flow obtained by the two probes was in agreement. The time-resolved measurements in the core region as well as in the wall layer by continuous increases and decreases in solids concentration and momentum flow from a base level at low solids concentration.
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| 3. |
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| 4. |
- Zhang, Wennan, 1962, et al.
(författare)
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Characteristics of the Lateral Particle Distribution in Circulating Fluidized Red Boilers
- 1993
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Ingår i: Proc of the 4th International Conference on Circulating Fluidized Beds. ; , s. 266-273
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Konferensbidrag (refereegranskat)abstract
- The local time-averaged solids volume fraction was measured in the 12MW~1 Circulating Ruidized Bed (CFR) boiler at Chalmers University of Technology. It was found that the corelwall-layer structure of the flow pattern observed in small-scale beds also characterizes large-scale CFR boilers. The local solids volume fractions close to the wall and in the core region of the furnace were found to be directly proportional to the cross-sectional average solids volume fraetjon, c, as ohtained from pressure rneasurements. If the shape of the membrane-tube wall is taken into account, the relationship for the solids fraction close to the wall (related to a plane wall) is c~=3.6c, which is similar to that reported in literature for plain walls.
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| 5. |
- Zhang, Wennan, 1962, et al.
(författare)
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Fluid-dynamic boundary layers in CFB boilers
- 1995
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 50:2, s. 201-210
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Tidskriftsartikel (refereegranskat)abstract
- The characteristics of the fluid-dynamic boundary layer (FBL) were studied in the 12 MW circulating fluidized bed boiler at Chalmers University of Technology. For a comparison, some additional measurements were made in a 165 MW CFB boiler. The FBL consists mainly of the falling film of particles at the furnace wall. The distance from the wall to the zero net particle flux position is used as a measure of the thickness of the layer. Horizontal profiles of particle flux, velocity and concentration were measured in the transport zone of the furnace. It was found that the FBL thickness varies only slightly or not at all with particle concentration, gas velocity and height in the furnace. An estimation of the thickness is given as a function of the horizontal bed dimension. The particle falling velocity inside the FBL is about 0.9–1.6 m/s depending on location. There is a sharp increase in particle concentration in the FBL all the way towards the wall. The disparity between the particle flux profile normal to a plain refractory-lined wall and the corresponding profile normal to a membrane-tube wall can be compensated for by taking the fin-tube configuration into account. From this point of view, the particle redistribution mechanism at the membrane-tube wall is discussed
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| 6. |
- Zhang, Wennan, 1962, et al.
(författare)
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Momentum probe and sampling probe for measurement of particle flow properties in CFB boilers
- 1997
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Ingår i: Chemical Engineering Science. - 0009-2509. ; 52:4, s. 497-509
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Tidskriftsartikel (refereegranskat)abstract
- With the aim of making local particle flow structure studies in commercial scalecirculating fluidized-bed (CFB) boilers, a momentum probe and a non-isokinetic particlesampling probe have been designed to measure local momentum flux of gas-solids flow andparticle flux. The time-averaged, local particle velocity and concentration are deduced from themeasurement results of these two probes. The two probes were calibrated and validated in situin a CFB boiler furnace. In order to better understand the principle of the momentum probeand to ensure reliable measurements, a theoretical model is established by focusing on theparticle deceleration movement inside the probe tip. This model is able to predict the relationshipbetween the gas-solids momentum flux and the impact pressure as obtained from thecalibration.
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