In most previous works, liquid hold-ups were studied by using a cold model of a fixed bed soaked prior to experiments. However, they did not consider that the dripping zone of a blast furnace is saturated with liquids or with evenly distributed droplets. In the present study, the characteristics of liquid hold-ups and liquid flow were investigated by using a one-dimensional cold model of a fixed bed soaked and unsoaked prior to experiments (initially soaked and unsoaked beds). Packed balls were five kinds, the diameters (D p ) of which ranged from 5.4 to 30 mm. Tap water was used as liquid. Contact angles (q) for these particle/liquid systems were about 70°and 10°for fluorine-coated particles and non-coated particles, respectively.Although, under bad wettability condition (q Լ 70°), total and static hold-ups for initially unsoaked bed packed with small balls are remarkably smaller than those for initially soaked bed, the difference in their hold-ups between initially unsoaked and soaked beds decreases with increasing ball size in the bed. In initially soaked bed, total and static hold-ups increase monotonically as ball size decreases, which means the specific surface area increases. On the other hand, in initially unsoaked bed, total and static hold-ups under bad wettability condition indicate maximum values at about D p ϭ10 mm and decrease abruptly in proportion to a decrease in particle size, despite an increase in the specific surface area. Only restricted liquid droplets and/or liquid rivulets are formed within the packed bed with good wettability condition (qԼ 10°) for initially unsoaked bed, nevertheless liquid is easy to spread out on the solid surface. The influence of the initial bed condition, soaked or unsoaked bed, on liquid hold-ups is great under bad wettability condition.KEY WORDS: ironmaking; blast furnace; dripping zone; fixed bed; liquid hold-ups; particle/liquid wettability; initially soaked and unsoaked beds.
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 ...
It is necessary to reexamine basically an ironmaking process in order to reduce C02 emission and energy consumption in a blast furnace. Especially, direct reduction from wustite (FeO) to iron (Fe) stage of iron ore sinter with solid earbon in the blast furnace is a strong endothermic reaction. H, injection from the lower part of the shaft at temperatures from 1173 to 1373K can be considered more effective for the increase of the reduction degree from FeO to Fe. The effective conditions of H2 ratio in CO-C02-H2-N2 mixture and the reduction temperatures have been investigated in the bed packed with sinter by comparlng the reduction degrees from FeO to Fe between one method blown all the gases into the alumina ball bed (all gas mixed injection method or Method A) and the other method blown only H, through another nozzles into the lower end of the sinter bed without mixing (H2 non-mixed injection method or Method N).In the gas composition (C0+H2)/(C0+CO,+H,)=0.75 at 11 73 K determined by taking into account those in the blast furnace, the reduction rate was enhanced in the case of Method N. In the present work, the effective conditions of H2 ratio in CO-COrH2-N2 mixture and the reduction temperatures have been investigated in the bed packed with sinter (Fig, l) by comparing the reduction degrees from FeO to Fe between one method blown all the gases into the alumina ball bed (all gas mixed injection method ; Method A) and the other method blown only H2 through another nozzles into the lower end of the sinter bed without mixing (H , nonmixed injection method ; Method N).
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