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- Johnsson, Filip, 1960, et al.
(author)
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An experimental study of in-furnace processes and dynamic behaviour of a 235 MWe CFB boiler
- 2004
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In: VGB PowerTech. - 1435-3199. ; 84:3, s. 82-87
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Journal article (peer-reviewed)abstract
- In a project funded by the 5th Framework Programme of the European Union, a 235 MWe Circulating Fluidized Bed (CFB) boiler is investigated with respect to in-furnace processes and dynamic response to load changes. The purpose of the project is to assess the insufficiently known features of large-scale CFB boilers. The furnace of the boiler has a cross-section of 21 x 10 meters and a height of 44 meters. The boiler is located in Turow, Poland, and is operated on a local brown coal.The project is unique in that several measurement ports were opened in the walls of the large CFB furnace for measurements in various locations inside the furnace. Also, a number of techniques were employed with new probes developed for this type of measurements to form a basis for studies of hydrodynamic processes as well as local variations in gas components (such as O2, CO, THC) and solid bed materials. The paper describes the measurement techniques and provides examples of results obtained from the in-situ measurements and from the dynamic response study.
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- Johnsson, Filip, 1960, et al.
(author)
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In-furnace processes in a 235 MWe CFB boiler
- 2002
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In: Proc. of the 7th International Conference on Circulating Fluidized Beds. - 9780920804988 ; , s. 607-614
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Conference paper (peer-reviewed)abstract
- In an experimental project funded by the 5th Framework Programme of the European Community (EC), different measurement techniques are used to analyze in-furnace processes in a 235 MWe Circulating Fluidized Bed (CFB) boiler in Turow, Poland. The purpose of the project is to assess the insufficiently known features of large-scale CFB boilers. The furnace of the boiler has a cross-section of 21 x 10 meters and a height of 43 meters. The boiler is operated on a local brown coal. Steady state, as well as dynamic conditions, are studied. The project is unique in two respects: Firstly, several measurement ports are provided in the large CFB furnace for in-situ measurements in various locations on the furnace. Secondly, a number of measurement techniques are employed. These facilitate studies of hydrodynamic processes as well as local variations in gas components (such as O2, CO, THC) and solids materials. The paper describes the measurement techniques and provides examples of the first (hydrodynamic) results obtained by the in-situ measurements.
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- Sternéus, Johan, 1970
(author)
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Gas Mixing in a Circulating Fluidised Bed Boiler
- 2001
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Doctoral thesis (other academic/artistic)abstract
- The present thesis is a study on the gas-mixing behaviour in a circulating fluidised bed (CFB) boiler. The aim is to describe how gas is spread in different regions of a CFB furnace and to explain variations in the mixing rate under different operating conditions. The results are based on pressure measurements, tracer-gas measurements and smoke visualisation. Experiments have been carried out in the Chalmers 12 MWth CFB boiler and in two experimental rigs, of which one is a scale model of the boiler. The units were operated under both non-circulating and circulating conditions. In the boiler, the superficial gas velocity ranged from 1.2 to 4.3 m/s and the bed material was silica sand with an average particle diameter of 0.32 mm. The mixing of gas is characterised by fluctuations of various scales. Gas, traced from a point source, flows in a plume that gets wider by small-scale fluctuations at the same time as the whole plume changes direction in a large-scale motion. The large-scale motion is due to large velocity fluctuations created by the bubble flow in the bottom-bed and by the explosions and collapses of bubbles at the surface of the bottom bed. Consequently, the dispersion is high in the bottom part of the riser with a maximum dispersion just above the surface of the bottom bed. The large-scale fluctuations in the gas-phase prevail, but with decreased amplitude, all the way up to the upper part of the riser. A similar trend in mixing rate (during operation with a bottom bed) is found in the core of the transport zone in the scale model and in the boiler. At low velocities, below circulating conditions, the mixing rate is high but falls steeply with increased gas velocity and levels out when circulating conditions are reached. The mixing rate during circulating conditions is found to be in the same range as previous literature data on gas mixing in CFB-risers, but at low velocities the mixing rate in the present units is higher because of the great contribution from large-scale motion under non-circulating conditions. In the transport zone, the dispersion of gas is influenced by several variables in a rather complex way.
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