Bubble Behavior in Vertical Tube Banks Installed in a Fluidized Bed.

Abstract

Fluidized bed combustion is one of advantageous technologies for coal and/or incineration firing especially with respect to the environmental protection of emissions, such as NOx/SOx. Bed material movement in such fluidized bed has a prime importance in the heat transfer process. Thus the quantitative measurements of bed material movement and void fraction are indispensable for better understanding fluidized-bed. In this investigation, neutron radiography is applied to visualize the bed material movement in a simulated fluidized bed heat exchanger installed with vertical tubes. Bubble behavior and void fraction profile are obtained by using the image processing technique. Bubble movement is highly restrained by these vertical tubes to that the bubbles rise up along the tube. The bubble diameter is well correlated by modified Mori&Wen's correlation taking into account the pitch of tube arrangement. The bubble rise velocity and void fraction are well correlated by applying the drift-flux model.