Interaction between a Fluidized Bed and Its Air-Supply System: Some Observations

Abstract

The interaction between a fluidized bed and its air-supply system was studied in a cold one-ninth-scale model of a 12-MWth circulating-fluidized-bed (CFB) boiler and in a 0.7 × 0.12 × 8.5 m cold unit. Simultaneous measurements were carried out of pressure fluctuations in the bed and in the air plenum; of flow fluctuations in the air-supply ducts; and in the scale model, of bubble dynamics by an optical probe. It is shown that the fluid dynamics of the bed, represented by power spectra of pressure fluctuations in the bed and in the air plenum, depend significantly on the configuration of the air-supply system. In the scale model, three modes of bubble flow were identified: (1) the single-bubble regime, with the presence of one bubble at a time in the bed and with an interaction between the bed and the air-supply system at the bubble frequency; (2) a regime in which single bubbles still dominate the spectrum but another type of structure becomes significant at a frequency of its own (so-called exploding bu...