PRESSURE LOSS AND HOLD-UP POWDERS FOR GAS-POWDER 2 PHASE FLOW IN PACKED-BEDS

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 (F(g-b)) 2) the interaction force between gas and powders (F(g-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 (F(p-k)). F(g-b)) could be given by the Ergun type gas flow resistance, and F(g-p) could be expressed by the Stokes flow law and the Richardson-Zaki's voidage function. Finally, F(p-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 hold-up 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.