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A 3D Model of Combustion in Large-Scale Circulating Fluidized Bed Boilers
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Karsten Luecke
Published/Copyright:
March 8, 2004
In a circulating fluidized bed (CFB) combustor the reacting solids are locally fed into the combustion chamber. These reactants have to be dispersed across the reactor's cross-sectional area. Since the rate of mixing is limited this leads to a mal-distribution of the reactants and to locally varying reaction conditions. In order to describe the influence of mixing a three-dimensional model of the combustion chamber is suggested. The model is divided into three sub-topics. First, the flow structure in terms of local gas and solids velocities and solids volume concentrations is described. Second, mixing of the solids and the gas phase is quantified by defining dispersion coefficients, and finally the combustion process itself, i.e. the reaction kinetics, is modelled. The model was validated against data from measurements in the large-scale combustor of Chalmers University of Technology in Göteborg/Sweden. Insufficient fuel mixing generated mal-distributions of locally released volatiles, which were the basis for the uneven reactants distribution at steady-state. In the case of two-stage operation, the injected secondary air did not reach immediately the reactor's center but was slowly mixed with the main gas flow. The concentration gradients hardly vanish before the exit of the combustion chamber.
Published Online: 2004-3-8
©2011 Walter de Gruyter GmbH & Co. KG, Berlin/Boston
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Keywords for this article
circulating fluidized bed;
CFB;
combustion;
gas mixing;
solids mixing;
model
Articles in the same Issue
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- Industrial Applications of Reactive Distillation: Recent Trends
- Phase Mixing Modeling in Multiphase Reactors Containing Gas Bubble: a Review.
- Article
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- Reactor Operating Strategy and Secondary Nucleation in Emulsion Polymerization
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- Conversion of Synthesis Gas into Light Hydrocarbons. Modelling of the Catalytic Reaction Network
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- Short Communication or Note
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