Classifying – separating – and assorting solids – Magnetic – Paramagnetic
Reexamination Certificate
2001-04-26
2003-06-24
Nguyen, Tuan N. (Department: 3653)
Classifying, separating, and assorting solids
Magnetic
Paramagnetic
C209S219000, C075S749000, C075S758000
Reexamination Certificate
active
06581779
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed to a method of magnetically loading a sintering material into a Dwight-Lloyd sintering apparatus in which a sintered ore is produced as one of the sintered materials for use in a blast furnace. The invention has particular reference to a method wherein magnetically susceptible sinterable substances such as ferrous metal-rich mill scale, calcium ferrite-containing returned ore and the like, and fine or particulate sinterable substances are charged on a pallet mounted on the sintering apparatus in such a manner that the two different types of substances are segregated in large amounts in an upper portion of a sintering material layer deposited on the pallet.
2. Description of the Related Art
In the production of a sintered ore using a sintering apparatus of a Dwight-Lloyd type (referred to hereinbelow as a DL sintering apparatus), ferrous metal-containing iron sources such as particulate iron ore, iron sand, mill scale and the like are first intermixed with secondary materials such as limestone, serpentine, returned ore and the like and further with fuel sources such as coke dust, gas ash and the like, whereby a sintering material is prepared which is then adjusted in its water content to about 7% and placed in granulated form. As shown in
FIG. 28
of the accompanying drawings, a sintering material
2
that has been put in an ore supplying hopper
1
mounted on a DL sintering apparatus is cut by means of a drum feeder
3
and supplied to a sloping chute
4
of a plate type. The sintering material
2
is segregated in regard to its particle sizes upon percolation (filtration or penetration) when it is slidably dropped out of the sloping chute
4
, and hence, such sintering material becomes rich in fine sinterable substances in its lower layer portion and rich in coarse sinterable substances in its upper and intermediate layer portions.
The sintering material
2
thus segregated upside down is subjected to inverse segregation of the particle sizes when it is charged from a lower end of the sloping chute
4
to a pallet
5
disposed to continuously travel in an arrowed direction. Thus, a sintering material layer
7
of a given thickness is formed with relatively fine sinterable substances segregated in its upper portion and relatively coarse sinterable substances segregated in its intermediate and lower portions. The sintering material layer
7
is subsequently ignited on its surface portion with a pilot burner (not shown) and sintered, while the pallet
5
is caused to move toward a rear end of the sintering apparatus, with air above the layer
7
being suctioned downwardly of a grate bar located on the pallet, the suctioning being conducted by the use of an exhauster (not shown). In this way, a sintered ore is produced.
In the sintering operation, the particle size distribution and compositional distribution of a sintering material deposited to correspond to the height of a sintering material layer bring about an important effect on successful sintering. Namely, at an initial stage of ignition in an igniting furnace, air is allowed to pass through the sintering material layer
7
from its ignited surface to its bottom upon suction at a lower part of the pallet
5
. In this course of sintering, air of normal temperature is supplied without preheating to a sintered melt zone (for example, a region of higher than 1,200° C.) that has been defined in an upper portion of the sintering material layer
7
. At middle and last stages of sintering, however, air to be suctioned downwardly of the layer
7
is passed through a completely sintered region in that upper portion and hence preheated, followed by feeding to sintered melt zones defined in the intermediate and lower portions of the layer
7
.
Consequently, the upper portion of the sintering material layer is lower in the bulk temperature and besides shorter in the length of time for exposure to elevated temperature than the intermediate and lower portions. This leaves the problem that a sintered ore formed in the upper portion is low in melt bonding and hence small in mechanical strength with reduced sintering yield.
In recent years, as a certain method of the loading of a sintering material, segregation loading has been highly reputed in which the particle size distribution and carbon content of a sintering material layer deposited on a pallet can be varied at will. Such method has been found effective in alleviating the problems discussed above.
Japanese Unexamined Patent Publication No. 61-223136 discloses, for instance, that a sintering material layer to be formed on a pallet should be reduced in its density by means of a screen constituted with a plurality of wire materials extending along a flow of sintering material being loaded on the pallet, and at the same time, the sintering material should be segregated with fine particles held in an upper layer and with coarse particles held in intermediate and lower layers so as to make the upper layer highly permeable to air with eventual improvement of yield and productivity of a sintered ore. This prior art method, however, has the problem that since a sintering material of 7% or so in water content is prone to get adhered to the wire materials, the resultant sintering material layer is difficult to stably retain in a segregated state as originally desired.
Japanese Unexamined Patent Publication No. 63-263386 discloses that a sintering material layer to be formed on a pallet should be reduced in density with fine particles segregated in an upper layer portion and with coarse particles segregated in a lower layer portion by use of a plurality of wires disposed perpendicular to a flow of sintering material being loaded on the pallet and by proper adjustment of the wire-to-wire openings to thereby improve the yield and productivity of a sintered ore owing to increased air permeability in the upper layer.
Such known method is contrived to remove part of the sintering material having been adherent to the wires by causing the latter to be displaced with use of a wind-up drum. However, since the wire openings once clogged with the sintering material are extremely difficult to free from the latter, the resulting sintering material layer cannot be stably retained in an initially expected segregated state.
On the other hand, in Japanese Unexamined Patent Publication No. 5-311257, a method is disclosed wherein a mixture of a combustible gas and a low-melting material is sprayed onto an upper portion of a sintering material layer deposited on a pallet with use of a sintering material in common use. In this instance, the heat of the combustible gas and the low-melting material are successively supplied to the upper portion of that layer. This means that sintering reaction improves in the upper layer portion, leading to a sintered ore of high strength. Such method, however, has rather a different but serious problem in that supply of a combustible gas, mixing of a low-melting material therewith, and transportation of and spraying of both gas and material require added equipment, thus entailing increased cost for installation or remolding of the new or existing equipment.
Furthermore, Japanese Unexamined Patent Publication No. 58-133333 discloses loading a sintering material on a pallet by applying a magnetic force, through an electromagnet disposed on a loading device, to a sintering material on dropping. More specifically, the electromagnet is secured to a roll feeder or the like located downwardly of an ore supplying hopper, and the magnetic force is given via the electromagnet to the content of ferrous metal (Fe) present in the sintering material being loaded. The drop speed of Fe is hence reduced with gentle loading of the sintering material ensured. Fine particles are relatively susceptible to higher magnetization than are coarse particles, and therefore, the lower the drop speed is, the particles become finer. This denotes that the coarse particles drop on the pallet earlier and enter a lower portion of
Fujii Norifumi
Igawa Katsutoshi
Kumeda Takahiro
Nushiro Kouichi
Ono Rikio
Kawasaki Steel Corporation
Nguyen Tuan N.
Orum & Roth
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