JP5594812B2 - Rotary hearth furnace and operating method thereof - Google Patents

Description

  The present invention mainly relates to a rotary hearth furnace for producing reduced iron from an iron oxide-containing raw material such as iron ore and ironmaking waste and an operating method thereof.

  For example, as disclosed in Patent Document 1, a rotary hearth furnace for producing reduced iron from iron oxide-containing raw materials such as iron ore and ironmaking waste has been put into practical use for a long time. The rotary hearth furnace includes an annular rotary hearth, an outer peripheral fixed wall disposed along the outer peripheral surface of the rotary hearth, an inner peripheral fixed wall disposed along the inner peripheral surface of the rotary hearth, Is provided. The gap between the outer peripheral surface and inner peripheral surface of the rotary hearth and the outer peripheral fixed wall and inner peripheral fixed wall around it is sealed by water-sealing the seal plates 11 disposed on both sides as shown in FIG. In this structure, the atmosphere outside the furnace is sucked into the furnace and the gas inside the furnace is prevented from leaking out of the furnace.

  However, the ironmaking waste generated at steelworks contains impurities such as zinc oxide. When iron oxide-containing raw materials containing zinc oxide are processed in a rotary hearth furnace, zinc vapor filled in the furnace rotates. When entering the gap between each peripheral surface of the hearth and each fixed wall, it is unavoidably deposited as a solid that is cooled by the cold radiation of the water seal and adheres to each peripheral surface and each fixed wall of the rotary hearth. It was. This deposit (symbol 12 in FIG. 2) grows with long-term operation, and eventually clogs the gap between each peripheral surface of the rotary hearth and each fixed wall, causing rotation failure of the rotary hearth. It was. Moreover, a great deal of labor was required for the deposit removal work performed when the furnace was stopped.

Japanese Patent Publication No. 45-19569

  A problem to be solved by the present invention is a rotary hearth furnace capable of preventing deposits of vaporized zinc and the like from adhering to the outer peripheral surface and inner peripheral surface of the rotary hearth and the outer peripheral fixed wall and inner peripheral fixed wall around the outer peripheral surface and inner peripheral surface. And providing an operation method thereof.

The rotary hearth furnace of the present invention includes an annular rotary hearth, an outer peripheral fixed wall disposed along the outer peripheral surface of the rotary hearth, and an inner peripheral fixed disposed along the inner peripheral surface of the rotary hearth. In a rotary hearth furnace comprising a wall, heating means for heating the gap between the outer peripheral surface of the rotary hearth and the outer peripheral fixed wall, and the gap between the inner peripheral surface of the rotary hearth and the inner peripheral fixed wall, It is characterized by being provided over the entire circumference .

  In this way, by heating the gaps by the heating means, the vaporized zinc in the furnace is cooled and precipitated in the gaps, and the outer peripheral surface and inner peripheral surface of the rotary hearth and the outer peripheral fixed wall around it and It can prevent adhering to the inner peripheral fixed wall.

In this invention, a heating means is provided over the perimeter below each said clearance gap . That is, by providing the heating means over the entire circumference of each gap, the entire circumference of each gap can be heated, so that precipitation and adhesion of vaporized zinc and the like can be prevented more reliably. Furthermore, by providing a heating means below each of the gaps, a high temperature rising air flow is generated in each of the gaps, so that it is difficult for zinc vapor or the like in the furnace to enter each of the gaps, and precipitation and adhesion thereof can be prevented. .

  As such a heating means, a burner or a hot air blowing device can be used.

  Moreover, the operating method of the rotary hearth furnace of the present invention is characterized in that combustion gas or hot air is blown upward from the lower side of each gap over the entire circumference of each gap. Accordingly, the entire circumference of each gap is heated and an updraft is generated over the whole circumference of each gap, so that precipitation and adhesion of zinc vaporized or the like can be prevented.

  In this case, the temperature of the combustion gas or hot air is preferably 900 ° C. or higher. By setting the temperature at 900 ° C. or higher, it is possible to more reliably prevent particularly problematic zinc vapor deposition. There is no particular upper limit to the temperature of the combustion gas or hot air, but in reality, the upper limit is about 1350 ° C.

  Moreover, it is preferable that the flow velocity of combustion gas or hot air shall be 0.7 m / s or more. According to the experiment by the present inventor, it has been confirmed that by setting the flow rate to 0.7 m / s or more, a sufficient ascending airflow is generated and the effect of preventing precipitation and adhesion of zinc vapor or the like is improved. There is no particular upper limit to the flow velocity of the combustion gas or hot air, but even if the flow velocity is made higher than 4 m / s, the effect is saturated. From this point, 5 m / s can be considered as the upper limit.

  In the present invention, providing the heating means over the entire circumference of each gap means that the heating means is provided continuously over the entire circumference of each gap, and the heating means is provided in the circumferential direction of each gap. It also includes providing a plurality at substantially equal intervals along the line. Similarly, blowing the combustion air or hot air over the entire circumference of each gap means that the combustion air or hot air is blown into all parts of the circumference of each gap and the combustion air or hot air is blown around the gap. It includes blowing into a plurality of locations at substantially equal intervals in the direction.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent that deposits, such as zinc vapor, adhere to the outer peripheral surface and inner peripheral surface of a rotary hearth, the outer peripheral fixed wall around it, and an inner peripheral fixed wall. Therefore, the rotation obstacle of the rotary hearth due to the growth of deposits can be eliminated, and it is not necessary to perform the deposit removal operation that has been conventionally performed when the furnace is stopped.

Embodiment of the rotary hearth furnace of this invention is shown, (a) is the schematic by the plane perspective, (b) is AA sectional drawing of (a), and shows an example of a heating means, (c) [FIG. 4] It is AA sectional drawing of (a), Comprising: Another example of a heating means is shown. It is sectional drawing which shows the structure of the clearance gap part of the outer peripheral surface of a rotary hearth, and an outer peripheral fixed wall in the conventional rotary hearth furnace.

  Embodiments of the present invention will be described below with reference to the drawings.

  Fig.1 (a) is the schematic by planar seeing which shows embodiment of the rotary hearth furnace of this invention. The rotary hearth furnace includes an annular rotary hearth 1, an outer peripheral fixed wall 2 arranged along the outer peripheral surface of the rotary hearth 1, and an inner circumference arranged along the inner peripheral surface of the rotary hearth 1. And a fixed wall 3. The iron oxide-containing raw material is supplied onto the rotary hearth 1 by the raw material supply device 4. In the embodiment, the rotary hearth 1 rotates clockwise, and while the rotary hearth 1 rotates, the iron oxide-containing raw material is reduced to become reduced iron and is discharged out of the furnace by the reduced iron discharge device 5.

  Below the gap between the outer peripheral surface of the rotary hearth 1 and the outer peripheral fixed wall 2 and the gap between the inner peripheral surface of the rotary hearth 1 and the inner peripheral fixed wall 3, heating means 6 for heating the respective gaps, Eight points are provided at equal intervals in the circumferential direction of each gap.

  As the heating means 6, as shown in FIGS. 1B and 1C, a burner 6a and a hot air blowing device 6b can be arranged. 1B and 1C show the heating means on the outer peripheral fixed wall 2 side, the cooling means on the inner peripheral fixed wall 2 side can also have the same configuration.

  The heating means 6 heats the entire circumference of each gap during the operation of the rotary hearth furnace, and an upward air flow is generated over the entire circumference of each gap, so that precipitation and adhesion of zinc vapor and the like can be prevented. .

  In this embodiment, the heating means 6 is provided at eight positions at equal intervals in the circumferential direction of each gap, but the number of the heating means 6 is not limited to this. However, from the viewpoint of heating the entire circumference of each gap substantially uniformly, it is preferable to provide the heating means at 8 to 50 locations at equal intervals in the circumferential direction of each gap.

  Of course, the heating means can be provided continuously in all the circumferences in each gap. For example, in the hot air blowing device 6b shown in FIG. 1 (c), hot air blowing ports may be provided continuously all around the lower part of each gap.

  In the rotary hearth furnace of the present invention shown in FIG. 1 (a), the hot air blowing device 6b shown in FIG. The state of deposits in the vicinity of each gap was observed. The temperature of the hot air was 1350 ° C.

  The state of the deposit was observed by dividing it into three areas A to C. Region A is a region above the upper surface of the rotary hearth, region B is lower than the upper surface of the rotary hearth and above the intermediate height of the cart that supports the rotary hearth 1 in rotation, and region C is the middle of the cart. It is an area below the height.

  Table 1 shows the state of deposits in each of the areas A to C. As shown in Table 1, when the flow rate of hot air was 0, that is, when hot air was not blown, strong deposits were observed in regions A and B, but when hot air was blown, no strong deposits were observed. . In particular, when the flow velocity of hot air was set to 0.7 m / s or more, deposits disappeared in the regions B and C.

DESCRIPTION OF SYMBOLS 1 Rotary hearth 2 Outer peripheral fixed wall 3 Inner peripheral fixed wall 4 Raw material supply apparatus 5 Reduced iron discharge apparatus 6 Heating means 6a Burner 6b Hot air blowing apparatus 11 Seal plate 12 Deposit

Claims (5)

In a rotary hearth furnace comprising an annular rotary hearth, an outer peripheral fixed wall disposed along the outer peripheral surface of the rotary hearth, and an inner peripheral fixed wall disposed along the inner peripheral surface of the rotary hearth The heating means for heating the gap between the outer peripheral surface of the rotary hearth and the outer peripheral fixed wall and the gap between the inner peripheral surface of the rotary hearth and the inner peripheral fixed wall is provided over the entire circumference below the respective gaps. Rotating hearth furnace.   The rotary hearth furnace according to claim 1, wherein the heating means is a burner or a hot air blowing device disposed below each of the gaps.   A rotary hearth furnace comprising an annular rotary hearth, an outer peripheral fixed wall disposed along the outer peripheral surface of the rotary hearth, and an inner peripheral fixed wall disposed along the inner peripheral surface of the rotary hearth In the operation method, combustion gas or hot air is blown in from the lower part of the clearance between the outer peripheral surface of the rotary hearth and the outer peripheral fixed wall and the lower surface of the inner peripheral surface of the rotary hearth and the inner peripheral fixed wall over the entire periphery of each of the clearances. A method for operating a rotary hearth furnace. The operating method of the rotary hearth furnace of Claim 3 which makes the temperature of the said combustion gas or a hot air 900 degreeC or more. The operation method of a rotary hearth furnace according to claim 3 or 4 , wherein a flow velocity of the combustion gas or hot air is 0.7 m / s or more.

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