2005 Volume 45 Issue 10 Pages 1474-1481
One of the important factors for minimum energy consumption and CO2 emission of a blast furnace (BF) is to elucidate the liquid flow phenomena and liquid hold-ups in the dripping zone of BF. Liquid hold-ups were studied by using a cold model of a fixed bed soaked prior to experiments (hereinafter called initially soaked bed), but the existing correlation equations derived from liquid hold-ups under initially soaked bed do not agree with liquid hold-ups under initially unsoaked bed such as the dripping zone of BF.
In the present study, correlation equations for liquid hold-ups in initially unsoaked bed were experimentally derived by a new approach, in which channeling factor (Fc) was proposed and defined as follows: Fc is the ratio of the number of liquid paths per one horizontal line to the number of voids between particles per the same horizontal line, and was measured by using the moving image of liquid paths photographed by a CCD video camera.
By using empirical equation for Fc, hold-ups in initially unsoaked bed were described as the following correlation equations.
Static hold-up HS(I-UB) (%)=0.9 · HS(I-SB) · F0.8c · Nc-1m
Dynamic hold-up Hd(I-UB) (%)=0.9 · Hd(I-SB) · F0.5c
Total hold-up is the sum of Hs and Hd Ht (%)=Hs+Hd
where, Ncm=1+(cosθ)3, and subscripts I-SB and I-UB designate quantities associated with initially soaked and unsoaked beds, respectively.
The comparison with the previous liquid hold-ups shows that the estimated hold-ups are in good agreement with the experimental values for any particle diameters used and both contact angles of 10° and 70° under initially unsoaked bed.