Risto V Filkoski
580 California St., Suite 400
San Francisco, CA, 94104
Modelling of Circulating Fluidised Beds Using CFD Technique
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Abstract
The paper is concerned with the potential of computational fluid dynamics (CFD) modelling as a tool for investigation and analysis of circulating fluidised bed (CFB) units. An assessment of where CFD may, or may not, be a helpful tool for developing the needed understanding, is furnished. A brief clarification of what composes a CFD analysis is provided. Two examples of CFD applications concerning the processes in circulating fluidised beds are shortly described in this study. The scope of the investigation in the first case is CFD modelling of aerodynamic and thermal processes in a riser of a laboratory gas-solid circulating fluidised bed unit. The second one is simulation of a small-scale coal fired CFB boiler with application of CFD. Both simulations were carried out in a 3D domain. Comparative analysis shows that CFD simulation is able to predict aerodynamic and heat transfer conditions with a satisfactorily accuracy and in a reasonable agreement with available corresponding experimental data.
FAQs
AI
What process parameters significantly influence heat transfer in CFB furnaces?
The simulation identifies bed density and solid material concentration near furnace walls as critical factors affecting heat transfer, particularly at elevated temperatures.
How does the Eulerian approach support CFB modelling in simulations?
The Eulerian approach allows for dynamic simulation of continuum phases while tracking solid particles, ensuring accurate representation of gas-solid interactions that are crucial in CFB operations.
What improvement does CFD provide over traditional experimental methods in thermal systems?
CFD enables faster turnaround and reproducibility, yielding insights into complex interactions without extensive hardware changes, allowing for exploration of more design alternatives.
How does particle size distribution affect model accuracy in CFB simulations?
Particles assume a Rosin-Rammler distribution; inaccuracies were noted in solid concentration predictions near the distributor where dense regions exist, affecting overall model reliability.
What were the main findings regarding temperature profiles in the CFB boiler?
CFD simulations showed expected temperature profiles aligned with 800-900 °C in the upper combustor, yet also highlighted disturbances due to secondary air injections at lower levels.
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