Effect of elevated pressure on bubble properties in a two-dimensional gas–solid fluidized bed

Abstract

Pressurized fluidization has been developed in quite a few industrial applications, such as newly proposed pressurized oxy-fuel combustion for CO2 capture. Quite a few studies reported that there are some differences of hydrodynamics between the pressurized and the atmospheric conditions. However, it is not very clear whether the correlations of the bubble size and rise velocity originally developed for the atmospheric condition can be used in pressurized condition. In this work, the effects of elevated pressure on the minimum fluidization velocity (umf), bubble properties (bubble size (Db) and bubble rise velocity (ub)) and bed expansion ratio are investigated in a lab-scale, pressurized fluidized bed, covering a range of 0.1–0.6MPa. Results show that the umf, bed expansion ratio (H/H0), Db and ub decrease with increasing pressure, and this change trend is more obvious for the larger particles. The predictions of the average bubble diameter in pressurized conditions are close to the prediction of the Cai correlation. The bubble rise velocity is well predicted by the Shen correlation and Davidson correlation without the (ug−umf) term. The relationships between the average bubble rise velocity and bubble diameter at different pressures satisfy the form of correlation ub=kgDb. With the pressure increasing from 0.1MPa to 0.6MPa, the coefficient k decreases slightly for different particles.