PURPOSE: To improve and uniformize reduction ratio by stabilizing the fluidity of iron ore by arranging two sets of preliminary reduction furnaces and many pieces of gas supplying ports.
CONSTITUTION: The powdery iron ore is supplied into a first circulating tube 31 connected with the lower part of a second cyclone 30, and further, supplied into the first preliminary reduction furnace 10. At this time, larger granule iron ore is reduced while forming bubble or a turbulent flow fluidized bed in the first pre-reduction furnace 10 by adjusting the flowing speed of a reducing gas, and a part thereof is discharged through a first discharging port 13. During the time when middle/finer granule iron ores are supplied under scattering state accompanied with the flowing reduction gas in the first pre-reduction furnace 10 to the lower part of the second pre-reduction furnace 20 through a second circulating tube 14, they are reduced under high speed fluidized bed state with the summarized reducing gas flow of the first pre-reduction furnace 10 and the second pre-reduction furnace 20, which is above the grain terminal velocity. In the second circulating tube 14 and a third circulating tube 41, in order to prevent the tube clogging caused by the middle/finer granule iron ore, a small quantity of reducing gas is supplied from a supplying branch tube S through many pieces of gas supplying ports P.
RI IRU OKU
BAKU MUN DOKU
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