JP2001254114A - Rotary hearth furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary hearth furnace, in which the service life of the rotary hearth is extended, and the maintenance is easily performed and the cost needed to this maintenance is reduced. SOLUTION: In this rotary hearth furnace in which pellet 8 obtained by mixing and granulating metal oxide and reducing agent, is charged on the rotary hearth 3 in the furnace and carried in the furnace by rotating this rotary hearth, and heated to a high temperature to reduce the metal oxide into the metal, dolomite grain 7 having 5-40 mm outer diameter is laid on the rotary hearth and the pellet is charged on the laid dolomite grain.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary hearth structure for reducing and recovering metal oxides such as steelmaking waste.

[0002]

2. Description of the Related Art The metal reduction treatment method conventionally called the inmeteco method is disclosed in Japanese Patent Publications Nos. 64-5233 and 8-3337827.
A powdery metal oxide (iron oxide, nickel oxide, etc.) and a reducing agent (coal, coke, etc.) are mixed with a binder and granulated to form pellets having a diameter of about 10 to 30 mm. It is intended to reduce and recover metals by charging them into a floor furnace and heating them to a high temperature.

[0003]

By the way, in the metal reduction treatment, a rotary bed furnace has been conventionally used. However, since the pellets melted by heating may be welded to a refractory constituting the rotary bed, Maintenance work for removing the refractory required a great deal of labor. In addition, a slit for absorbing thermal expansion is conventionally formed in the rotating bed, but if pellets fall into the slit, it will not be able to absorb the expansion at the next temperature rise in the case of a rigid refractory, and the refractory May cause damage. Further, there is a problem that the hearth refractory is liable to be worn when the pellet is sandwiched between the hearth refractory and a screw conveyor for discharging the pellet. For this reason, in the past, the life of the refractory on the rotating bed was short, maintenance was not easy, and high cost was required. Therefore, the present invention is to solve the above-mentioned problems, prolong the life of the rotating bed, facilitate maintenance, and reduce the cost.

[0004]

For this purpose, the present invention provides a method in which a pellet formed by mixing and granulating a metal oxide and a reducing agent is charged on a rotating bed in a furnace, and the rotating bed is rotated. A rotary bed furnace used to reduce the metal by transporting the pellets in a furnace and heating the pellets to a high temperature. Dolomite grains having an outer diameter of 5 to 40 mm are laid on the rotary bed, and the pellets are placed thereon. It is characterized by being arranged.

[0005]

Next, an embodiment of a rotary hearth furnace according to the present invention will be described. As shown in the horizontal sectional plan view of FIG. 1 and the sectional view taken along line AA of FIG.
A furnace body 1 having a circular plane shape is formed, wheels 2 are fixed to the bottom of the furnace body, and an annular rotating floor 3 is supported on the wheels 2. The rotating floor 3 is driven by a power source (not shown). Are configured to rotate at a low speed in the direction of arrow a in the furnace.

The rotary floor 3 is constructed of fire-resistant bricks, and convex ridges 4 and 5 are formed on an outer peripheral edge and an inner peripheral edge of an upper surface thereof to form a concave portion 6 having a depth of about 50 mm. Dolomite grains 7 having an outer diameter of 5 to 40 mm are laid therein. The dolomite grains 7 are made of SiO, CaO, MgO.
It is a brick made of dolomite (kukai stone) whose main component is calcined. It is inexpensive and easily available, and has characteristics such as being chemically stable and having high heat resistance.

Reference numeral 8 denotes pellets of metal oxide to be reduced in the rotary bed furnace. The pellets are used to reduce powdery or granular materials such as steelmaking dust or waste car pulverized chips to a carbon-based reducing agent such as coal, coke or charcoal, and bentonite. It is formed into a pellet having an outer diameter of 10 to 30 mm by mixing and granulating with an inorganic binder such as.

Reference numeral 9 denotes a pellet loading opening formed on the ceiling wall of the furnace body 1, 10 a burner provided on the side wall of the furnace body, 11 a combustion gas discharge port, and 12 provided so as to span the rotary bed 3. The screw conveyor 13 provided is a pellet extraction port provided at one end of the screw conveyor. A heating zone and a reduction zone are formed in the furnace body 1 according to the rotation direction of the rotary bed 3 indicated by the arrow a. Then, the pellets 8 are loaded from the charging port 9 and placed on the dolomite grains 7 laid on the rotating bed 3, and are heated to a high temperature of about 1000 ° C. in a heating zone as the rotating bed 3 rotates, The metal oxide in the pellets is reduced and metallized by contact with a carbon-based reducing agent under the atmosphere gas kept reducible in the reduction zone. Then, it is scraped to the extraction port 13 by the screw conveyor 12 and discharged out of the furnace.

In the rotary bed 3, even if the pellets 8 are melted by heating, they only penetrate between the dolomite grains 7 laid on the rotary bed 3. Without welding to itself, there is no danger that the pellets will fall on the slits for absorbing thermal expansion and damage the hearth, making maintenance easier.
Further, even if the dolomite grains 7 adhere to the pellets 8 and are directly carried into a blast furnace or a smelting furnace, SiO, CaO,
Since it is mainly composed of MgO, there is no adverse effect.

As shown in FIG. 3, when the pellets 8 are scraped by the screw conveyor 12 to the extraction port 11, even if the pellets are pressed down by the screw conveyor, the dolomite granules laid under the pellets are crushed. Since the 7 can move freely, there is no danger that the pellets 8 will bite and hinder the rotation of the screw conveyor 12 or wear the rotating bed itself. The size of the dolomite particles to be laid on the rotating bed is desirably 5 to 40 mm in outer diameter. When the size is approximately in this range, the dolomite particles can move freely, and the above-described action is performed. , To be able to absorb shrinkage.

[0011]

As described above, according to the present invention, a pellet obtained by mixing and granulating a metal oxide and a reducing agent is charged on a rotary bed in a furnace, and the pellet is rotated by rotating the rotary bed. A rotary bed furnace used to reduce metal by being transported in a furnace and heated to a high temperature, and having an outer diameter of 5 to 4 on a rotary bed.
Since the dolomite grains of 0 mm are laid and the pellets are placed thereon, there are beneficial effects such as extending the life of the rotating bed, facilitating maintenance, and reducing the cost.

[Brief description of the drawings]

FIG. 1 is a horizontal sectional plan view showing an embodiment of a rotary bed furnace of the present invention.

FIG. 2 is a sectional view taken along the line AA of the rotary bed furnace of FIG.

FIG. 3 is a cross-sectional view of the rotary bed furnace of FIG. 1 taken along line BB.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace body 3 Rotating floor 4, 5 Convex ridge 6 Depression 7 Dolomite grain 8 Pellet

Claims (1)

[Claims] 1. A pellet formed by mixing and granulating a metal oxide and a reducing agent is loaded on a rotary bed in a furnace, and the rotary bed is rotated to convey the pellets in the furnace to a high temperature. A rotary bed furnace used for reducing a metal by heating, wherein dolomite grains having an outer diameter of 5 to 40 mm are laid on the rotary bed, and pellets are placed thereon. Rotary hearth furnace.