Pressure Loss and Hold-up Powders for Gas-Powder Two Phase Flow in Packed Beds

Abstract

Flow characteristics of gas-powder two phase flow in packed beds were experimentally examined for clarifying the aerodynamic behavior of powders in a blast furnace. It was found that two phase flow showed higher pressure loss compared with clean gas flow. Based on the experimental results, a mathematical model for gas-powder two phase flow in packed beds was developed. In this model, three kinds of interaction forces were considered, including: 1) the interaction force between gas and packed particles (Fg_b) 2) the interaction force between gas and powders (Fg_p), and 3) the restraint force of powder motion due to (i) the gravitational force of powders and (ii) the collision and the friction between powders and packed particles (Fp-k). Fg_b could be given by the Ergun type gas flow resistance, and Fs_p could be expressed by the Stokes flow law and the Richardson-Zaki's voidage function. Finally, Fp_k could be empirically correlated by using the Fanning equation and the Froude number. This model allows satisfactory prediction of the pressure loss and the hold-up of powders in the packed bed. Furthermore, it was confirmed that the increase in the pressure loss was mainly caused by the increase in the holdup of powders in the region of low gas velocity and by the interaction force between powders and packed particles in the region of high gas velocity. © 1991, The Iron and Steel Institute of Japan. All rights reserved.