Heating – Shaft type
Patent
1996-06-27
1998-11-03
Bennett, Henry A.
Heating
Shaft type
432 98, 414203, 266184, F27D 108
Patent
active
058299688
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a charging device for a shaft furnace. More particularly, it relates to a charging device for a shaft furnace comprising two superposed hoppers, the lower hopper of which is equipped with a bell capable, in a closed position, of blocking the opening for the discharge of the lower, hopper into the shaft furnace and, in an open position, of distributing the charging material over the surface of the charge.
Conventional charging devices for a shaft furnace, particularly a blast furnace, generally comprise a lower bell of large diameter and an upper bell of smaller diameter. The two bells are fitted into a lower hopper which forms a charging chamber for the shaft furnace. The large bell provides for the sealing off from the shaft furnace and for the distribution of the charging material over the surface of the charge. The small bell provides for the sealing off from an upper hopper which is in direct communication with the atmosphere.
This upper hopper, which is fed by skip elevators, is normally a rotating hopper in order to ensure a more symmetrical feeding of the charging chamber. In fact, it is known that the charging of a static hopper by skip elevators, off-set from the axis of the blast furnace, produces very asymmetrical charging profiles in this hopper, which entails an asymmetrical charging of the charging chamber and hence an asymmetrical distribution of the charging material by the large bell over the surface of the charge in the shaft furnace. Now, it is known that deviations from symmetry in the charge in the shaft furnace have harmful repercussions on the functioning of this furnace.
These conventional charging devices have the disadvantage that the lower bell inadequately fulfills its function as a lower sealing device for the charging chamber. In fact, because of the large diameter of the lower bell and of abrasion by the charging material flowing along the lower bell, it is almost impossible to provide for a durable seal between the lower bell and its seating formed try the lower edge of the charging chamber.
In order to rectify this lack of sealing, it has been proposed to duplicate the charging chamber. In other words, it has been proposed that the rotating upper hopper should be made in the form of a closed vessel, which can be isolated from the atmosphere by using upper sealing valves. A device of this type is described, for example, in the patent specifications US-A-4,878,655 and US-A-4,881,869.
According to these two US patent specifications, the lower bell is suspended from a rod positioned along the axis of the shaft furnace. The upper hopper is suspended above the lower hopper in such a way that it can be driven in rotation around the axis of the shaft furnace. A first sealed rotating joint is provided for this purpose between the lower hopper and the upper hopper. At its upper end, the upper rotating hopper is connected in a sealed manner, using a second sealed rotating joint, to a fixed cap fitted with two feeding tanks for skip elevators. These feeding tanks are fitted with upper sealing valves. The lower means for blocking off the rotating hopper essentially comprise a bell which can be moved along the is axis of the furnace below the rotating hopper, between an upper position blocking a discharge opening, and a lower position, in which it unblocks an annular discharge opening and is located directly in the flux of material. For this purpose, the upper bell is suspended from a sleeve surrounding the suspension rod for the lower bell. It simultaneously fulfills a function as a material retention device add a sealing device between the upper rotating hopper and the lower fixed hopper and also forms, in the open position, at the discharge opening, a kind of radial expansion device for the flux of material flowing from the upper hopper into the lower hopper.
The charging device described above makes it possible in a natural way, thanks to its upper rotating hopper, to avoid large deviations from symmetry in the charge in the shaft furnace. However, it does no
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Bernard Gilbert
Lonardi Emile
Solvi Marc
Thillen Guy
Bennett Henry A.
Paul Wurth S.A.
Wilson Gregory A.
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