Experimental investigation of bed-to-wall heat transfer in fluidized beds of a Geldart B sorbent particle under a full spectrum of fluidization regime

Fluidization technology has been used in CO₂ capture processes, the successful design and operation of the heat exchangers involved in this process require much information on the bed-to-wall heat transfer of the sorbent particles in fluidized states. In this study, the bed-to-wall heat transfer coefficient (h) of a solid amine sorbent was measured by a heat transfer probe in a large-scale circulating fluidized bed cold model unit, where full spectrum of fluidization regimes can be realized. The corresponding hydrodynamic signals were also studied by pressure sensors and optical fiber probes to further explain the newly discovered phenomenon. The results show that in a dense bed, due to the counterbalanced effect of time fraction of packet and packet renewal frequency, h of the Geldart B particle reaches a peak within the bubbling fluidized regime, and the radial distribution of h are opposite in bubbling and turbulent fluidized regimes. In a fast fluidization regime, gas convection becomes the dominant factor affecting h when the solids holdup is low enough. Correlations were provided or recommended to guide the design of heat exchangers in the fluidized bed CO₂ capture processes.