JP4351569B2 - Device for discharging reduced agglomerates in a metal reduction furnace with a rotary hearth - Google Patents

Description

  The present invention relates to a reduced iron ingot obtained by heating and reducing an iron oxide agglomerate made of a reducing material such as iron ore or ironmaking waste such as iron ore or carbonaceous material on a rotary hearth in a metal reduction furnace having a rotary hearth. The present invention relates to a discharge device for a metal reduction furnace that discharges the composition outside the furnace.

  As a process for producing reduced iron and alloyed iron, a highly productive rotary hearth method has been implemented, but this rotary hearth method lacks a central part under fixed refractory ceilings and sidewalls. This is a process mainly composed of a calcination reduction furnace (hereinafter referred to as a rotary furnace) in which a disk-shaped refractory hearth rotates on a rail at a constant speed, and is used for reduction of metal oxide. Many of these rotary furnaces have a hearth diameter of 10 to 50 m and a width of 2 to 6 m.

  The powder containing the metal oxide of the raw material is mixed with a carbon-based reducing agent, and then made into raw material pellets and supplied to the rotary furnace. In addition to the advantage that the raw material pellets are placed on this hearth and left to stand so that the raw material pellets are not easily disintegrated in the furnace, the powdered raw material does not adhere to the hearth and the product yield of the lump is increased. There is a strong merit. In addition, the use of coal-based reducing agents and powder raw materials, which are high in productivity and inexpensive, can be used. Furthermore, this rotary hearth method is effective in reducing iron impurities generated in blast furnaces, converters, and electric furnaces, and thickener sludge in rolling processes and removing impurities, and is also used as a dust processing process. It is also an effective process for recycling.

  The operation of this rotary hearth method involves first mixing a raw material ore, dust, sludge metal oxide with a carbon-based reducing agent in an amount necessary for the reduction of the oxide, and then a granulator such as a pan pelletizer. A pellet having a diameter of several to several tens of mm is manufactured, and this is supplied onto the hearth of a rotary furnace and laid in layers. The pellets laid on the hearth are rapidly heated, baked at a high temperature of about 1200 to 1300 ° C. for 5 to 20 minutes, and discharged outside the furnace by a discharge device provided in the rotary furnace.

  The entire process of the rotary furnace passes through the molding apparatus 1, the drying apparatus 2, the rotary furnace 3, and the side of the rotary furnace 3, as shown in FIG. 1 (a), (b), and (c). It comprises a discharge device 4. This discharge device has a screw and is arranged on the furnace. It rotates in a high-temperature atmosphere of about 1200 to 1300 ° C., and contacts and rotates the hearth 5 while reducing agglomerates such as reduced iron outside the furnace. To be discharged. At this time, the granulated material is partly pulverized due to collapse during transportation, explosion in the furnace, etc., and the metal oxide in the powder is reduced in a reducing atmosphere to become metal, which is sintered at a high temperature. As a result, the phenomenon that the hearth becomes rocky occurs.

  The spiral screw system is usually adopted for the discharge device, and there are two types of blade mounting of the spiral screw, welding type and bolt mounting type. For reasons of ease of maintenance and thermal distortion reduction, bolt mounting type Is recommended. The material of the spiral blade is a heat-resistant cast steel, heat-resistant special cast steel, or heat-resistant cast steel with a heat-resistant or wear-resistant material built up on its surface. Furthermore, the surface temperature of the rotary hearth is 700-900 ° C even near the location where the discharge device is installed, and the hearth is rocked. Therefore, the spiral blade is worn and damaged by any material, and the life is several months to 1 The year is short. Replacement of worn or damaged spiral blades requires a dedicated replacement facility to replace the interior of the furnace at a high temperature, and a facility outage of several days to a week is necessary to replace the interior of the furnace at a normal temperature. Become.

  Thus, for example, a reduced iron discharging apparatus as described in Patent Document 1 has been proposed. As shown in the schematic configuration diagram of the discharge device in FIG. 2A and the enlarged view of FIG. 2B, this discharge device has a coating layer 7 made of an amorphous refractory having a high thermal conductivity on the outer periphery of the water-cooled rotary shaft 6. And a spiral blade 9 formed of a heat-resistant material spirally attached to a blade attachment lug 8 protruding from the water-cooled rotary shaft 6 in order to absorb thermal expansion on the outer periphery of the water-cooled rotary shaft 6. It is proposed that a plurality of these spiral blades 9 are fixed with bolts and nuts 10 so that a continuous spiral blade is formed. However, it is proposed that these spiral blades, bolts, and nuts are made of a material having high-temperature strength, thereby avoiding the trouble of broken bolts.

  However, no matter how such a configuration is, the wear / damage of the spiral blades provided on the outer periphery of the water-cooled rotary shaft of the discharge device is not improved, and there is still a situation where frequent replacement work is forced.

JP 2000-129326 A

  In order to solve the above problems, the present invention provides a metal reduction furnace having a rotary hearth, and an iron oxide agglomerate comprising a reduction material such as iron ore and ironmaking waste such as iron ore and carbonaceous material on the rotary hearth. In a metal reduction furnace discharge device that discharges reduced iron agglomerates that have been heated and reduced to the outside of the furnace, the tip of the rotating spiral blade protruding from the water-cooled rotating shaft is made ceramic, thereby reducing the wear and damage of the rotating spiral blade. It is an object of the present invention to provide a metal reduction furnace discharge apparatus that can withstand a long life.

  The present invention has been made to solve the above problems, and the gist thereof is as follows.

(1) In a metal reduction furnace discharge apparatus having a rotary hearth in which a screw for discharging reduced agglomerates is disposed on the hearth , a plurality of ceramic chips are provided at the tip of the base material of the spiral blade of the screw. In a metal reduction furnace having a rotary hearth , wherein the ceramic chip is attached by casting at least one row in the longitudinal direction of the spiral blades, and the ceramic chip has a structure having at least one constriction in the depth direction . A device for discharging reduced agglomerates.

(2) Reduction in a metal reduction furnace having a rotary hearth according to (1), wherein the ceramic chip is made of at least one of nitride, oxide, carbide, boride, or a composite thereof. Agglomerate discharge device.

( 3 ) An arrangement of ceramic chips cast at the tip of the base material of the spiral blade is arranged in at least one row in the longitudinal direction of the spiral blade and in a staggered or random manner. ( 1) Or the discharge | reduction apparatus of the reduction agglomerate in the metal reduction furnace which has a rotary hearth as described in (2) .

( 4 ) Any one of ( 1) to (3), wherein the cross-sectional shape of the surface of the ceramic chip that contacts the rotary hearth is arranged as one or more of a circle, an ellipse, and a polygon. An apparatus for discharging reduced agglomerates in a metal reduction furnace having the rotary hearth described in the above item .

( 5 ) The ratio of the total cross-sectional area (A) of the ceramic chip and the cross-sectional area (B) of the spiral blade on the surface contacting the rotary hearth: A / B is 0.3 to 0.8, A reduction agglomerate discharging apparatus in a metal reduction furnace having a rotary hearth according to any one of ( 1) to (4) .

( 6 ) The ratio of the individual cross-sectional area (a) of the ceramic chip on the surface in contact with the rotary hearth to the casting depth (H): a / H is 0.5 to 8 ( 1) to (5) reducing agglomerates discharge device for the metal reduction furnace having a rotary hearth according to any one of.

( 7 ) The material of the base material of the spiral blade is made of any one of high chromium cast iron, high nickel alloy-based grain cast iron, martensitic high-speed steel, stainless steel, or a combination thereof. The apparatus for discharging reduced agglomerates in a metal reduction furnace having the rotary hearth according to any one of (1) to ( 6 ).

( 8 ) The rotation according to any one of (1) to ( 7 ), wherein a ratio of a linear expansion coefficient of the base material of the spiral blade to the ceramic chip is 0.5 to 2.0. An apparatus for discharging reduced agglomerates in a metal reduction furnace having a hearth.

( 9 ) The reduced mass in the metal reduction furnace having the rotary hearth according to any one of (1) to ( 8 ), wherein the spiral blade is attached to a blade attachment lug by a bolt. Compound discharger.

  The present invention has good manufacturing cost performance by ceramicizing only the rotating spiral blade or the tip of the spiral blade base material protruding from the water-cooled rotating shaft of the discharge device installed in the metal reduction furnace having the rotary hearth However, it is possible to reduce wear in a high temperature atmosphere and extend the life several times as compared with the conventional product, and to improve the operating rate of the rotary furnace equipment.

  The entire process of the rotary furnace according to the present invention is the same as that described in the background art except for the portion related to the discharge device.

  The actual condition of wear and damage of the rotating spiral blade of the discharge device installed in a metal reduction furnace with a rotary hearth is about one month when the wear and damage in the height direction of the rotating spiral blade is heat-resistant cast steel. Rotating shaft cooling, heat-resistant metallization, and build-up are as short as about 3 months, and there is a problem of replacement of the rotating spiral blades and the accompanying shutdown of the rotary furnace. It was necessary to search for many materials excellent in high temperature strength and high temperature hardness.

  Accordingly, the present inventors have found that ceramic is the most suitable material that can satisfy both of these characteristics in searching for a material having wear resistance, high temperature strength, and high temperature hardness. The present invention has been made based on this finding. In the present invention, in the metal reduction furnace discharge apparatus having a rotary hearth, the entire spiral blade of the screw is made of ceramic or the material of the spiral blade base material of the screw. Is made of high-Cr cast iron, high-Ni alloy-based grain cast iron, martensitic high-speed steel, or stainless steel, or a combination thereof, and the tip of the spiral blade of the screw is made of ceramic. It is the biggest feature that is attached to the tip of the spiral blade in a special form. In particular, alumina-based and silicon nitride-based ceramic materials are about 1/10 in relative wear compared to conventional hard metals such as high-Cr cast iron, and the hardness (Hv) is about three times as high-temperature strength and high-temperature hardness. It has very excellent characteristics. It was also found that among ceramic materials, the fracture toughness value increased in the order of alumina, silicon nitride, silicon carbide, and cemented carbide. As described above, in the present invention, the tip of the screw spiral blade or the screw spiral blade is made of ceramic, so that the wear resistance is about 5 times that of a conventional hard metal material. It has also been found to exert an excellent effect of extending. Thus, in the present invention, the ceramic material used for the screw spiral blade or the tip of the screw spiral blade is any material of nitride, oxide, carbide or boride, or a composite thereof. Any material may be used as long as it is superior in wear resistance as compared with a hard metal such as high Cr cast iron. In addition, it is preferable that the ratio of the linear expansion coefficient with respect to the ceramic of the said spiral blade base material shall be 0.5-2.0, when ensuring the high temperature strength and high temperature hardness of a spiral blade base material.

  Also in the present invention, like the conventional method, the spiral blade itself is bolted to the blade mounting lug, so that maintainability is improved and deformation due to thermal strain is also alleviated.

  Furthermore, in the present invention, it has been described that the ceramic is attached to the tip of the spiral blade or the base material of the spiral blade in a special form, but a method of attaching the ceramic or ceramic chip as shown in FIG. 3 was examined. In FIG. 3, (a) is a standard small chip pasting mold, (b) is an all-ceramic mold, (c) is a partial ceramic simplified mold, (d) is a partially ceramicized inlay mold, and (e) is a chip casting mold. is there. However, each of these types has advantages and disadvantages as described below. That is, in (a), the cost of the ceramic chip is low, but if the method of fixing the chip is a ceramic adhesive or welding, the bonding strength tends to be weak, and the fitting tends to increase the machining cost. is there. In (b), there is an advantage that the wear allowance can be maximized, but if the ceramic curved surface and oblique machining are machined, the machining cost tends to increase. In (c), there are some mounting bolt wear, joint wear, etc., but the processing cost of the ceramic is relatively low. In (d), there is an advantage that the ceramic does not easily fall off, but there is a tendency that both the ceramic and the hardware need to be processed and the processing cost increases. In (e), there is a possibility of joint wear and cracking of the ceramic chip during casting, but there is an advantage that the ceramic is hardly dropped off. Therefore, in the present invention, (a) to (e) can be selected according to the required purpose. However, (c) to (e) are preferable, and (e) in terms of the balance between cost and reliability. Is more preferable.

  Further, when the chip casting mold of (e) is adopted, the chip casting method is as shown in FIG. 4A, and the chip 11 is seen in a plan view in the longitudinal center of the tip of the spiral blade 9. The simplest method is to cast at a linear interval. (B) is a sectional view of (a). Further, as shown in FIG. 5 (a), when viewed in a plane, the chips 11 are linearly spaced in the longitudinal direction of the tip of the spiral blade 9 and overlapped in the width direction so as to be cast in a staggered pattern. Abrasion can also be further improved. (C) is a sectional view of (a). Further, as shown in FIG. 5 (b), it is possible to improve wear resistance by casting a plurality of staggered arrangements shown in FIG.

Next, the shape of the ceramic chip 11 is a polygonal (rectangular) shape such as a circle (a), an ellipse (b), a square (c), or a hexagon (d) in a longitudinal section as shown in FIG. However, from a practical viewpoint such as workability of the ceramic chip, a circular shape as shown in FIG. 6 (a) or an elliptical shape as shown in FIG. 6 (b) is preferable.

  Furthermore, the shape of the ceramic chip 11 in the depth direction is such that, as shown in FIG. 7, the taper method (a) having a divergent shape in which the area expands in the depth direction of the spiral blade, at least in the depth direction of the spiral blade. A constriction method (b) having one or more constricted portions 12 can be employed.

When the ceramic chip 11 having a circular or rectangular cross-sectional shape as shown in FIGS. 5 and 6 is cast in the spiral blade 9, the total ceramic cross-sectional area (A) (shown in FIG. 4 (a)). Ratio of spiral blade cross-sectional area (B) (total cross-sectional area including the ceramic portion of spiral blade 9 shown in FIG. 4 (a)) to 5 (total cross-sectional area of ceramic chip 11): A / B is 0.3 to It is preferable to set it to 0.8. In addition, the cross-sectional area (a) of each ceramic chip casted on the spiral blade (individual cross-sectional area of the ceramic chip 11 shown in FIG. 4A: cm ² ) and the depth of casting (H) (FIG. 4B The ratio of the depth of the ceramic chip 11 indicated by: cm): a / H is preferably 0.5-8. This is because the ratio is experimentally obtained from the viewpoints of the strength and toughness of the spiral blade and the wear resistance of the ceramic chip, and a long life can be practically secured.

In this embodiment, a method of casting a ceramic chip having a rectangular cross section as shown in FIGS. 3 (e) and 4 (a), which is a chip casting mold, in a spiral blade will be described. 5 straight ceramic chips 11 having a rectangular cross section of 3 cm length and 2 cm width on the surface of the spiral blade 9 having a length of 18 cm, a width of 3 cm and a total cross-sectional area of 54 cm ^{2 at} the tip end section. For example, it was cast at a depth (H) of 3.5 cm. The total cross-sectional area of the ceramic chip at this time was 30 cm ² , and the ratio of the spiral blade cross-sectional area (B) to the ceramic total cross-sectional area (A): A / B was 0.56. The ratio of the cross-sectional area (a) of the ceramic chip to the depth of casting (H): a / H was 1.7. Thus, the wear test of the spiral blade was carried out for about 10 months with the actual device using the discharging device in which the ceramic chip was cast on the surface of the spiral blade. As a result, as shown in FIG. 8, the wear amount of the conventional heat-resistant cast steel spiral blade reached about 60 mm in 10 months, whereas the wear amount of the ceramic chip cast-in spiral blade according to the present invention has passed 6 months. Even so, a remarkable effect of only a few millimeters could still be obtained.

(A) is the whole process schematic diagram of the metal reduction furnace which has a rotary hearth, (b) is the schematic diagram of a rotary furnace main body, (c) is sectional drawing before and behind the discharge apparatus of a rotary furnace main body. (A) is a schematic block diagram of the discharge apparatus of a metal reduction furnace, (b) is an enlarged view of a spiral blade part. (A)-(e) is a figure which shows the ceramic chip attachment method to the front-end | tip part of the base material of a spiral blade or a spiral blade. (A), (b) is a figure which shows the state which cast the ceramic chip to the front-end | tip part of the base material of the spiral blade by this invention. (A), (b), (c) is a figure which shows another aspect which cast the ceramic chip | tip to the spiral blade front-end | tip part by this invention. (A)-(d) is a figure which shows the cross-sectional shape of a ceramic chip | tip. (A), (b) is a figure which shows the shape in the depth direction which cast the ceramic chip | tip to the front-end | tip part of the spiral blade by this invention. The figure which shows the abrasion test result of a discharge screw.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Molding device 2 ... Drying device 3 ... Rotary furnace 4 ... Discharge device 5 ... Hearth 6 ... Water-cooled rotating shaft 7 ... Coating layer 8 ... Blade attachment lug 9 ... Spiral blade 10 ... Bolt, nut 11 ... Ceramic chip 12 ... Narrow part 13 ... Reduced agglomerate

Claims (9)

In a metal reduction furnace discharge apparatus having a rotary hearth in which a screw for discharging reduced agglomerates is disposed on the hearth , a plurality of ceramic chips are attached to the tip of the base material of the spiral blade of the screw . Reduction agglomeration in a metal reduction furnace having a rotary hearth , wherein the ceramic chip is attached by casting in at least one row in the longitudinal direction, and the ceramic chip has a structure having at least one constriction in the depth direction. Chemical discharge device. 2. The reduced agglomerate in a metal reduction furnace having a rotary hearth according to claim 1, wherein the ceramic chip is made of at least one of nitride, oxide, carbide and boride or a composite thereof. Discharge device. Claim 1, characterized in that arranged in at least one row or more, and in a staggered or random form an array of ceramic chips are cast into the distal end portion of the base material of the spiral blade in the longitudinal direction of the spiral blade Or the discharge | reduction apparatus of the reduction agglomerate in the metal reduction furnace which has a rotary hearth of 2 . The rotation according to any one of claims 1 to 3, wherein a cross-sectional shape of a surface of the ceramic chip that contacts the rotary hearth is arranged as one or more of a circle, an ellipse, and a polygon. An apparatus for discharging reduced agglomerates in a metal reduction furnace having a hearth. The ratio of the total cross-sectional area (A) of the ceramic chip and the cross-sectional area (B) of the spiral blade on the surface in contact with the rotary hearth: A / B is 0.3 to 0.8. An apparatus for discharging reduced agglomerates in a metal reduction furnace having the rotary hearth according to any one of 1 to 4 . Wherein the ratio of the individual cross-sectional area of contact with the rotary hearth surface of the ceramic chip and (a), casting a depth (H): claim 1, characterized in that a 0.5 to 8 to a / H ~ An apparatus for discharging reduced agglomerates in a metal reduction furnace having the rotary hearth according to any one of 5 . The material of the base material of the spiral blade is made of any one of high chromium cast iron, high nickel alloy-based grain cast iron, martensitic high-speed steel, or stainless steel, or a combination thereof. An apparatus for discharging reduced agglomerates in a metal reduction furnace having the rotary hearth according to any one of 1 to 6 . The metal having a rotary hearth according to any one of claims 1 to 7 , wherein a ratio of a linear expansion coefficient of the base material of the spiral blade to the ceramic chip is 0.5 to 2.0. A device for discharging reduced agglomerates in a reduction furnace. The apparatus for discharging reduced agglomerates in a metal reduction furnace having a rotary hearth according to any one of claims 1 to 8 , wherein the spiral blade is attached to a blade attachment lug by a bolt. .

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