Investigation on the internal and external solid flow rates in large-scale circulating fluidized bed with different layouts of suspended heating surfaces

Abstract

Suspended Heating Surfaces (SHSs) in large-scale circulating fluidized bed (CFB) boilers have a significant impact on internal ( G s,i ) and external ( G s,o ) circulating solid flow rates that is important for heat transfer. In this paper, the distribution of G s,i and G s,o in a 650 × 680 × 3500 mm 3 CFB apparatus was simulated and verified by experimentations. On this foundation, the effects of SHSs structural layouts on G s,i and G s,o were investigated in a 350 MW supercritical CFB boiler. Results showed that G s,i increased by 65.8% as SHSs number increased from 0 to 20, whereas G s,o decreased by 17.8%, so G s,o / G s,i decreased correspondingly. Meanwhile, increasing SHSs height had a greater improvement on G s,i than width, which would be more conducive to the heat transfer near SHSs. Finally, empirical formulas of G s,o , G s,i and layout parameters of SHSs were developed, and the research results can provide meaningful reference for the operation optimization of large-scale CFB boilers. • Effects of suspended heating surface layout on circulating flow rates are studied. • The ratio variation of internal and external circulating flow rates is explored. • Internal circulating flow rate increases with increasing surface number and area. • Empirical formula of structural parameters on circulating flow rate is achieved.