Influence of Channeling Factor on Liquid Hold-ups in an Initially Unsoaked Bed

Abstract

One of the important factors for minimum energy consumption and CO 2 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 ( F c ) was proposed and defined as follows: F c 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 F c , hold-ups in initially unsoaked bed were described as the following correlation equations.Static hold-up H S(I-UB) (%)ϭ0. , 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°u nder initially unsoaked bed.KEY WORDS: channeling factor; empirical equation; initially unsoaked bed; liquid hold-up; liquid path; blast furnace.ber 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. Experimental Visualization of Liquid Paths through Initially Unsoaked BedThe visualization method was used in order to investigate liquid flow behavior and to measure F c in initially unsoaked bed. A packed vessel for visualization was two-dimensional model (2D model) with a rectangular parallelepiped made of transparent acrylic resins as shown in Fig. 1. The size of the packed bed is 400 mm in width, 100 mm in depth and 175 mm in height. A liquid distributor of the visualization model installed above the packed bed was composed of 773 injection needles of 0.5 mm I.D. and 25 mm in length to disperse liquid uniformly on the top surface of the packed bed. The filtered tap water was dyed with red ink for easy visualization of liquid paths. Liquid flow behavior and liquid paths were photographed continuously from the front of the packed bed by using a CCD video camera. A digital camera was also used. Solid/liquid contact angles (q) of tap water were about 70°and 10°for fluorine-coated particles and non-coated particles, respectively. In the visualization model, both q decreased to about 65°and 5°, respectively, because the water was dyed with red ink, which is a surface-active agent.To reduce the wall surface effect of the packed column on the liquid flow distribution and hold-ups, the inner surface was ...

Characteristics of Liquid Hold-ups in a Soaked and Unsoaked Fixed Bed

“…Even if D p increases up to 40, 50 and 60 mm such as the dripping zone in BF, H S and H t for initially unsoaked bed are estimated at about 90 % of those for initially soaked bed by author's equation. 15) On the other hand, H d in both cases of initially unsoaked (ᮀ) and soaked beds () have almost the same values except for D p ϭ5.4 mm. In the near future, the significant difference in H d for D p ϭ5.4 mm should be investigated.…”

Static Holdup of Liquid Slag in Carbonaceous Beds

“…Dynamic holdup is the volume fraction of the liquid in the bed, which drains out from the bed when Kawabata et al reported that when there is no gas injection from the bottom, the static holdup, which is much larger than the dynamic holdup, is a dominant factor determining the total holdup. 8,9) Moreover, when the static and dynamic holdups are investigated simultaneously, the reliability of the obtained results becomes lower. [14][15][16] Therefore, in this study, only the static holdup is considered.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Shulman et al 2) suggested that the liquid holdup is composed of static and operating (dynamic) hold-up. Because of the difficulties encountered in high temperature experiments, many cold model studies have been widely carried out.…”

“…Because of the difficulties encountered in high temperature experiments, many cold model studies have been widely carried out. [1][2][3][4][5][6][7][8][9][10][11][12] In the cold model studies, aqueous solutions and alumina or waxed spheres were generally used instead of liquid slags and carbonaceous materials, respectively. However, in the cold model studies, the density of the liquid is smaller than the solid particles, whereas the density of the liquid slag in the BF operations is larger than the solid carbonaceous materials.…”

Numerical Simulation of Dripping Behavior of Droplet in Packed Bed Using Particle Method

“…suggests that the liquid flow phenomenon comprises various phenomena, such as branching and coalescence of flow paths, which are collections of droplets, deformation of droplets, and the like. 9,10) Accordingly, when attempting to express the total liquid flow, there are limits to the conventional stochastic approach based on a distribution of spheres. Furthermore, wettability with the coke packed bed, the physical properties of the liquid phase, and other factors have a complex effect on the liquid flow in the bottom of the blast furnace.…”