Abstract
The paper presents the results of experimental verification of the simplified set of scaling parameters for which the particle density as well as the cold model length scale may be chosen independently. The tests were carried out on two large scale 1/10 and 1/20 geometrically similar cold models of the Lagisza 966 MWth supercritical CFB boiler. The proposed set of dimensionless quantities allowed the Lagisza 966 MWth CFB boiler to be closely modeled by cold models. However, the agreement between the hot bed and cold model's suspension density distributions is better for the 1/10 scale cold model. That suggests that the choice of the scale of a cold model is not without effect on the macroscopic movements of solids in the riser. Moreover, the study shows that a simplification of the scaling laws which excludes the very important solid-to-gas density ratio can give acceptable results over a wide range of boiler loadings.
Highlights
The main environmental advantage of Circulated Fluidized Bed (CFB) technology is its ability to burn a diverse range of difficult low grade fuels of varying quality with low emissions of NOx, low-cost sulfur capture during combustion in the furnace itself, as well as low CO and CxHy emissions due to turbulent conditions and good mixing (Nowak and Mirek, 2013)
In the bottom part of the combustion chamber (x/H=0.03; x/H=0.05) the scatter of the solids suspension density values is the result of the intense turbulent mixing of particles and rapidly erupting bubbles, whose size in fluidized beds increases with gas velocity (Kunii and Levenspiel, 1991)
In the dilute region (x/H=0.3), the reason for the lower pressure gradient is the influence of the secondary air stream, which at the 100% MCR has the highest value compared to the primary air stream (PA/SA=1.86) and causes considerable dilution of the gas-solid mixture just above the supply region
Summary
The main environmental advantage of Circulated Fluidized Bed (CFB) technology is its ability to burn a diverse range of difficult low grade fuels of varying quality with low emissions of NOx, low-cost sulfur capture during combustion in the furnace itself, as well as low CO and CxHy emissions due to turbulent conditions and good mixing (Nowak and Mirek, 2013). Due to the complex flow behavior that characterizes gas-solid systems, a complete description of circulating fluidized bed hydrodynamics remains a challenging task (Detamore et al, 2001). Horio (1996), there have been three different approaches to the scaling law of fluidized beds: classical dimensional analysis (e.g., Buckingham π-theorem), differential equations (or, non-dimensionalization of the continuum equations that describe multiphase flows) and theoretical solutions and experimental correlations. Taking into consideration the second approach and differential equations derived by Anderson and Jackson (1967), Glicksman and coworkers (1994) formulated the following set of dimensionless quantities describing the state of the full hydrodynamic similarity between two unlike CFB systems: U02 gH
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