Granulation device, method for producing granulated sintered raw material, and method for producing sintered ore

Abstract

The present invention provides: a granulation device which is capable of efficiently heating a sintering starting material by blowing steam into the sintering starting material; a method for producing a granulated sintering starting material; and a method for producing a sintered ore, the method using the method for producing a granulated sintering starting material.　The present invention provides a granulation device for granulating a sintering starting material that contains an iron-containing starting material, a CaO-containing starting material and a coagulating agent, the granulation device comprising: a cylindrical drum which rotates about a rotation axis that matches the lateral direction, while being provided with a feed port through which the sintering starting material is input and a discharge port through which a granulated sintering starting material is discharged; a steam pipe which is provided within the drum only in a posterior part from a position in between the feed port and the discharge port to the discharge port; and a plurality of nozzles which are connected to the steam pipe so as to eject the steam onto a deposition surface of the sintering starting material.

Description

[Technical field]

[0001] The present invention relates to a granulating device for granulating a sintering raw material, a method for producing a granulated sintering raw material, and a method for producing sintered ore. [Background technology]

[0002] Sintered ore, which is a raw material for blast furnaces, is generally produced by using iron-containing raw materials such as iron ore powder, recovered powder in steelworks, and sintered ore undersize powder, CaO-containing raw materials such as limestone and dolomite, and carbonaceous materials (solid fuel) such as coke powder and anthracite as sintering raw materials, using a Dwight Lloyd sintering machine (hereinafter, sometimes referred to as "sintering machine"), which is an endless moving sintering machine. The sintering raw materials are charged into the endless moving pallet of the sintering machine to form a charging layer. The thickness (height) of the charging layer is about 400 to 800 mm. Then, the carbonaceous materials on the surface of the charging layer are ignited by an ignition furnace installed above the charging layer. The carbonaceous materials in the charging layer are sequentially burned by sucking air downward through a wind box arranged under the pallet. This combustion progresses gradually downward and forward as the pallet moves. The sintering raw materials are burned and melted by the combustion heat generated at this time, and a sintered cake is produced. The resulting sintered cake is then crushed in the ore discharge section, cooled in a cooler, and sized to produce sintered ore.

[0003] In the production of sintered ore using the above-mentioned sintering machine, a technique is known in which the ratio of the wet zone in the charging bed is reduced by preheating and drying the sintering raw material, thereby improving the permeability of the charging bed and improving the productivity of sintered ore. For example, Patent Document 1 discloses a method for producing granulated sintered raw material in which steam such as water vapor is injected during granulation of the sintering raw material to heat the sintering raw material. According to Patent Document 1, the sintering raw material is preheated and dried by granulating the sintering raw material while injecting water vapor, which improves the permeability of the charging bed and improves the productivity of sintered ore. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2019 / 167888 [Patent Document 2] Patent Publication No. 2022-39966 Summary of the Invention [Problem to be solved by the invention]

[0005] The method disclosed in Patent Document 1 is a method of granulating the sintering raw material while injecting steam, but there is no disclosure or suggestion of injecting steam in the downstream region (later part) where the sintering raw material moves in the drum mixer. Therefore, when the method disclosed in Patent Document 1 is used, the temperature of the granulated sintering raw material drops before it is discharged from the discharge port. In addition, the method disclosed in Patent Document 2 is a method of heating the granulated raw material in a heating device, so that even after passing through the heating device, the target temperature may not be reached due to the difficulty of heat transfer to the inside of the raw material. The present invention has been made in consideration of such problems in the prior art, and its purpose is to provide a granulation device that can efficiently heat the sintering raw material by injecting steam into the sintering raw material, a method for producing granulated sintering raw material, and a method for producing sintered ore using the method for producing granulated sintering raw material. [Means for solving the problem]

[0006] The means for solving the above problems are as follows. [1] A granulation device for granulating a sintering raw material containing an iron-containing raw material, a CaO-containing raw material, and a coagulant, comprising: a cylindrical drum having an inlet through which the sintering raw material is fed and an outlet through which the granulated sintering raw material is discharged, the drum rotating about a horizontal axis of rotation; a steam pipe provided within the drum only in the rear half between the midpoint between the inlet and the outlet and the outlet; and a plurality of nozzles connected to the steam pipe for spraying steam onto the deposition surface of the sintering raw material. [2] A method for producing granulated sintered raw material, which uses a granulating device to granulate sintered raw material containing an iron-containing raw material, a CaO-containing raw material, and a coagulant, wherein the granulating device has a cylindrical drum that is provided with an inlet through which the sintered raw material is fed and an outlet through which the granulated sintered raw material is discharged, and that rotates around a horizontal axis, and wherein steam is blown into the sintered raw material only in the latter half of the drum, between the midpoint between the inlet and the outlet and the outlet, to produce the granulated sintered raw material. [3] The method for producing a granulated sintered raw material described in [2], further adding moisture of 0.5 mass % or more and 4.5 mass % or less to the sintered raw material when the temperature of the granulated sintered raw material discharged from the granulation device becomes 60°C or higher. [4] A method for producing sintered ore, comprising sintering the granulated sintered raw material granulated by the method for producing granulated sintered raw material according to [2] or [3] in a sintering machine to produce sintered ore. Effect of the Invention

[0007] By using the granulating device according to the present invention, the sinter raw material can be efficiently heated by injecting steam, thereby reducing the amount of steam used during granulation. By using this heated granulated sinter raw material, the air permeability of the charging bed is improved and the productivity of sintered ore is improved, so by using the granulating device according to the present invention, the productivity of sintered ore can be improved and the manufacturing cost of sintered ore can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing an example of a sintered ore production facility 10 having a drum mixer 32 which is a granulating device according to this embodiment. [Diagram 2] FIG. 2 is a graph showing the relationship between the temperature rise of the pseudo-particles when they are charged onto the pallet of the sintering machine and the rate of increase in the productivity of sintered ore. [Diagram 3] FIG. 3 is a graph showing the moisture content of the sintering raw materials in Experimental Examples 1 to 3. [Figure 4] FIG. 4 is a graph showing the particle size of the pseudo-particles and the permeability index JPU of the sintered bed in Experimental Examples 1 to 3. [Diagram 5] FIG. 5 is a graph showing the productivity of sintered ore in Experimental Examples 1 to 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] The present invention will be described below through embodiments of the invention. Fig. 1 is a schematic diagram showing an example of a sintered ore production facility 10 having a drum mixer 32, which is a granulation device according to this embodiment. Iron-containing raw materials 12 stored in a yard 11 are transported to a blending tank 22 by a transport conveyor 14. The iron-containing raw materials 12 include various brands of iron ore and dust generated in a steelworks.

[0010] The raw material supply section 20 includes a plurality of blending tanks 22, 24, 25, 26, and 28. The blending tank 22 stores the iron-containing raw material 12. The blending tank 24 stores the CaO-containing raw material 16 containing limestone and quicklime, and the blending tank 25 stores the MgO-containing raw material 17 containing dolomite and refined nickel slag. The blending tank 26 stores the coke powder and anthracite aggregate 18 crushed to a particle size of 1 mm or less using a rod mill. The blending tank 28 stores the return ore (sintered ore undersieve powder) having a particle size of 5 mm or less that is undersieved from the sintered ore. A predetermined amount of each raw material is cut out from the blending tanks 22 to 28 of the raw material supply section 20, and these are blended to form the sintered raw material. The sintered raw material is transported to the drum mixer 32 by the transport conveyor 30. The MgO-containing raw material 17 is an optional blended raw material, and may or may not be blended with the sintered raw material.

[0011] The drum mixer 32 is a granulation device that granulates the sintering raw material while spraying steam onto it. The drum mixer 32 has a cylindrical drum 33 that rotates with a horizontal axis of rotation, a steam pipe 36, and a plurality of nozzles 37 that are connected to the steam pipe 36 and spray steam 38 onto the deposition surface of the sintering raw material. Note that steam is an example of steam. The rotation axis of the drum mixer 32 may be approximately horizontal. In order to efficiently discharge the pseudo-particles, the rotation axis may be inclined so that the discharge port 35 is located vertically below the inlet 34.

[0012] The cylindrical drum 33 is provided with an inlet 34 at one end face of the drum 33 through which the sintering raw material is introduced, and an outlet at the other end face of the drum 33 through which the granulated sintering raw material (hereinafter referred to as pseudo particles) is discharged. The steam pipe 36 is provided only in the latter half of the drum 33 from the midpoint between the inlet 34 and the outlet 35 to the outlet 35, and blows steam from this position through multiple nozzles 37 toward the deposition surface of the sintering raw material.

[0013] In this way, by granulating the sintering raw material while blowing steam into the sintering raw material in the latter half of the drum 33, pseudo particles with an average particle size of about 3.0 mm are manufactured at a higher temperature than the sintering raw material granulated without blowing steam. The pseudo particles are transported to the sintering machine 40 by the transport conveyor 39. In this embodiment, the average particle size of the pseudo particles is an arithmetic mean particle size, which is a particle size defined by Σ(Vi×di) (where Vi is the abundance ratio of particles in the i-th particle size range, and di is the representative particle size of the i-th particle size range). The drum mixer 32 is an example of a granulating device that granulates the sintering raw material.

[0014] The sintering machine 40 is, for example, a downward suction type Dwight Lloyd type sintering machine. The sintering machine 40 has a sintering material supply device 42, an endless movable pallet cart 44, an ignition furnace 46, and a wind box 48. The sintering material is charged from the sintering material supply device 42 to the pallet cart 44, and a charging layer of the sintering material is formed. The charging layer is ignited by the ignition furnace 46. By sucking air through the wind box 48, the coagulant 18 is combusted in the charging layer, and the combustion and melting zone in the charging layer is moved downward in the charging layer. As a result, the charging layer is sintered to form a sintered cake. In this embodiment, a gas fuel supply device 47 may be provided. The gaseous fuel supplied from the gaseous fuel supply device 47 is any combustible gas selected from blast furnace gas, coke oven gas, blast furnace / coke oven mixed gas, converter gas, city gas, natural gas, methane gas, ethane gas, propane gas, shale gas, and mixed gases thereof.

[0015] The sintered cake is crushed by a crusher 50 to produce sintered ore. The sintered ore crushed by the crusher 50 is cooled by a cooler 52. The sintered ore cooled by the cooler 52 is sieved by a sieving device 54 having a plurality of sieves, and is sieved into a finished sintered ore 56 having a particle size of more than 5 mm and a return ore 58 having a particle size of 5 mm or less. The finished sintered ore 56 is used as a blast furnace raw material. Meanwhile, the return ore 58 is transported by a transport conveyor 60 to the blending tank 28 of the raw material supply section 20. In this embodiment, the particle size of the finished sintered ore 56 and the particle size of the return ore 58 refer to the particle size sieved by a sieve. For example, a particle size of more than 5 mm means a particle size sieved onto a sieve with a mesh size of 5 mm, and a particle size of 5 mm or less means a particle size sieved onto a sieve with a mesh size of 5 mm. The particle size values ​​of the product sinter 56 and the return ore 58 are merely examples and are not limited to these values.

[0016] In this way, in the production of sintered ore using the sintered ore production equipment 10, the sintered raw materials are granulated while being heated by blowing steam into them in the drum mixer 32. This improves the air permeability of the sintered raw materials charging bed, thereby improving the productivity of the sintered raw materials.

[0017] FIG. 2 is a graph showing the relationship between the rising temperature of the pseudo-particles charged into the pallet cart 44 of the sintering machine and the rate of increase in productivity of sintered ore. The horizontal axis of FIG. 2 is the rising temperature (°C) of the pseudo-particles when they are charged into the pallet cart 44 of the sintering machine. The rising temperature is the difference between the average temperature of the pseudo-particles granulated by injecting steam when they are charged into the pallet cart 44 and the average temperature of the pseudo-particles granulated without injecting steam. The average temperature of the pseudo-particles granulated without injecting steam is 18.3°C, and the plots in the figure are examples of the average temperatures of the pseudo-particles when they are charged into the pallet cart 44 being 38.0°C, 35.0°C, 35.5°C, 45.0°C, and 51.0°C. The vertical axis of FIG. 2 is the improvement effect (%) of the productivity of sintered ore, which is a value calculated by the following formula (1).

[0018] (T2-T1) × 100 / T1 (1) In the above formula (1), T1 is the productivity of sintered ore (t / (hr×m)) when sintered ore is produced using pseudo-particles granulated without injecting steam. 2 )), and T2 is the productivity of sintered ore when sintered ore is produced using pseudo-particles granulated by injecting steam (t / (hr×m 2 )).

[0019] As shown in Fig. 2, the increase rate of sintered ore productivity increased as the average temperature of the pseudo-particles at the time of charging into the pallet cart 44 increased. From this result, it can be seen that the productivity of sintered ore can be improved by blowing steam into the sintering raw material in the drum mixer 32 to turn it into high-temperature pseudo-particles and using the pseudo-particles to produce sintered ore.

[0020] On the other hand, if the average temperature of the pseudo-particles exceeds 60°C, the moisture evaporates and pseudo-particles of the desired particle size cannot be granulated. If the particle size of the pseudo-particles becomes small, the air permeability of the sintering bed deteriorates, and the productivity of sintered ore decreases significantly.

[0021] Fig. 3 is a graph showing the moisture content of the sintering raw materials in Experimental Examples 1 to 3. In Fig. 3, the bar graphs shown with diagonal hatching show the moisture content (mass%) of the sintering raw materials on the inlet side of the drum mixer, and the bar graphs shown with horizontal hatching show the moisture content (mass%) of the sintering raw materials when they are charged into the sintering machine. Experimental Example 1 is a production example using pseudo particles in which the average temperature of the sintering raw materials when they are charged into the sintering machine is 33°C. Experimental Example 2 is a production example using pseudo particles in which the average temperature of the sintering raw materials when they are charged into the sintering machine is 60°C. Experimental Example 3 is a production example using pseudo particles in which the average temperature of the sintering raw materials when they are charged into the sintering machine is 62°C.

[0022] As shown in Fig. 3, it can be seen that the moisture content of the raw material was kept at 6.5 mass% even when it was charged into the sintering machine in Experimental Example 1 and Experimental Example 3. On the other hand, in Experimental Example 2, although the moisture content of 6.5 mass% was kept at the inlet side of the drum mixer, the moisture evaporated due to heating, so the moisture content decreased to about 5.5 mass% when it was charged into the sintering machine.

[0023] Fig. 4 is a graph showing the particle diameter of the pseudo-particles and the permeability index JPU of the sintering bed in Experimental Examples 1 to 3. In Fig. 4, the bar graph shown with diagonal hatching shows the particle diameter (mm) of the pseudo-particles, and the bar graph shown with horizontal hatching shows the permeability index JPU (-) ((-) means dimensionless). Note that the particle diameter of the pseudo-particles is the calculated average particle diameter described above, and the permeability index JPU of the sintering bed is an index calculated using the following formula (2).

[0024] JPU = V / [S × (ΔP / h) 0.6 ]···(2) In the above formula (1), V is the air volume (m 3 / min, and S is the effective area of ​​the sintering machine (m 2 ), h is the bed height (mm), and ΔP is the pressure drop (mmH2O).

[0025] As shown in FIG. 4, in Experimental Example 1 and Experimental Example 3, pseudo-particles with a particle diameter of about 3 mm were granulated, but in Experimental Example 2, only pseudo-particles with a particle diameter of about 1 mm were granulated. The decrease in the particle diameter of the pseudo-particles in Experimental Example 2 is considered to be due to the decrease in the moisture content of the raw material shown in FIG. 3. In Experimental Example 3, pseudo-particles with a particle diameter of about 3 mm were granulated at high temperature, so the permeability index of the sintering bed was about 17. In Experimental Example 1, pseudo-particles with the same particle diameter were granulated, but the average temperature of the pseudo-particles was low, so the permeability index of the sintering bed was about 15. In Experimental Example 2, pseudo-particles with a high temperature were granulated, but only pseudo-particles with a particle diameter of about 1 mm were granulated, so the permeability index of the sintering bed was significantly decreased to about 12.

[0026] Fig. 5 is a graph showing the productivity of sintered ore in Experimental Examples 1 to 3. The productivity of sintered ore per 1 m of the sintering layer 2 This is the amount of product sintered ore produced (t) per hour per sinter. As shown in Fig. 5, the productivity in Experimental Example 3 was 1.39 compared to 1.29 in Experimental Example 1, and the productivity of sintered ore was significantly increased. The improvement in productivity in Experimental Example 3 is thought to be due to the improvement in permeability shown in Fig. 4. On the other hand, in Experimental Example 2, the permeability of the sintering bed was significantly reduced, sintering did not progress, and the sintering raw materials were not agglomerated.

[0027] In this way, when the average temperature of the pseudo-particles discharged from the granulator is 60°C or higher, the moisture evaporates due to the temperature, so that the moisture required for granulation is insufficient, pseudo-particles of a predetermined particle size cannot be granulated, and the breathability of the charging bed deteriorates. When the pseudo-particles discharged from the drum mixer 32 are heated to an average temperature of 60°C or higher and lower than 80°C, the amount of moisture evaporated was confirmed to be in the range of 0.5% by mass to 3.0% by mass after granulation. Furthermore, when the pseudo-particles discharged from the drum mixer 32 are heated to an average temperature of 80°C or higher, the amount of moisture evaporated was confirmed to be in the range of 2.0% by mass to 4.5% by mass after granulation.

[0028] From these results, when the average temperature of the pseudo-particles discharged from the granulator is set to 60°C or higher, it is preferable to further add moisture in the range of 0.5% by mass to 4.5% by mass in terms of the moisture content after granulation to the sintering raw material during granulation. This ensures the moisture content required for granulation even when the pseudo-particles are heated to 60°C or higher, and pseudo-particles with a particle diameter of about 3 mm heated to 60°C or higher can be produced from the sintering raw material. By producing sintered ore using these heated pseudo-particles, the air permeability of the charging bed is improved, and this improves the productivity of sintered ore. Note that when the average temperature of the pseudo-particles is set to 60°C or higher and lower than 80°C, it is preferable to further add moisture in the range of 0.5% by mass to 3.0% by mass in terms of the moisture content after granulation to the sintering raw material during granulation, and when the average temperature of the pseudo-particles is set to 80°C or higher, it is preferable to further add moisture in the range of 2.0% by mass to 4.5% by mass in terms of the moisture content after granulation.

[0029] The amount of water to be added may be determined within the above range by measuring the water content of the pseudo-particles discharged from the drum mixer 32 at predetermined intervals. Water may be added by adding industrial water, hot water or condensed water to the sintering raw material during granulation.

[0030] Next, the installation position of the steam pipe 36 in the drum mixer 32 will be described. Table 1 shows the results of an experiment on blowing steam into the sintering raw material, in which the steam pipe 36 was installed at either the inlet side or the outlet side. The temperature at the outlet side in the table is the average temperature of the pseudo-particles discharged from the drum mixer 32.

[0031] [Table 1]

[0032] Experimental Examples 11 and 12 are granulation examples in which the steam pipe 36 is provided only in the first half of the sintering material from the inlet 34 to the midpoint between the inlet and the discharge port, and steam is blown into the sintering material to granulate it. Experimental Examples 13 to 15 are granulation examples in which the steam pipe 36 is provided only in the second half of the sintering material from the midpoint between the inlet 34 and the discharge port 35 to the discharge port 35, and steam is blown into the sintering material to granulate it.

[0033] From a comparison between Experimental Example 11 and Experimental Example 13, and a comparison between Experimental Example 12 and Experimental Example 14, the average temperature at the outlet side of the pseudo-particles granulated by blowing steam into the steam pipe 36 provided in the rear part was 8 to 11°C higher than the average temperature at the outlet side of the pseudo-particles granulated by blowing steam into the steam pipe 36 provided in the front part. Also, from a comparison between Experimental Example 11 and Experimental Example 15, if the temperature at the outlet side of the pseudo-particles was the same, the amount of steam blown during granulation could be reduced by 17% by providing the steam pipe 36 in the rear part. From these results, it was confirmed that the sintering raw material could be heated more efficiently by providing the steam pipe 36 having multiple nozzles 37 only in the rear part of the drum mixer 32 and blowing steam into the sintering raw material from the nozzles 37 than by providing a steam pipe having multiple nozzles in another position of the drum mixer 32.

[0034] As described above, the drum mixer 32, which is the granulation device according to this embodiment, can inject steam into the sintering raw material and heat it efficiently. Therefore, if the amount of steam used is the same, the sintering raw material can be heated to a higher temperature, and if the temperature at the outlet side is the same, the sintering raw material can be heated with a smaller amount of steam used. In this way, by using the granulation device according to this embodiment, the amount of steam used during sintering can be reduced while heating the sintering raw material to a predetermined temperature, thereby improving the productivity of the sintered ore and suppressing the increase in the production cost of sintered ore. [Explanation of symbols]

[0035] 10. Sintered ore manufacturing facility 11 yards 12 Iron-containing raw materials 14 Transport Conveyor 16 CaO-containing raw materials 17 MgO-containing raw materials 18 Setting agent 20 Raw material supply department 22 Mixing tank 24 Blending tank 26 Blending tank 28 Blending tank 30 Transport Conveyor 32 Drum Mixer 33 Drums 34 Inlet 35 Outlet 36 Steam piping 37 Nozzle 38 Water Vapor 39 Transport Conveyor 40 Sintering machine 42 Sintering material supply device 44 Pallet Trolley 46 Ignition Furnace 48 Wind Box 50 Crusher 52 Cooler 54 Sieving device 56 Finished sinter 58 Return Mine 60 Transport Conveyor 62 Sintering materials

Claims

1. A method for producing a granulated sintered raw material, comprising the steps of: granulating a sintered raw material containing an iron-containing raw material, a CaO-containing raw material, and a coagulant using a granulator; The granulating device has an inlet through which the sintering raw material is introduced and an outlet through which the granulated sintering raw material is discharged, and has a cylindrical drum that rotates about a rotation axis in the horizontal direction, In the drum, steam is blown into the sintering raw material only in a rear half portion between the intermediate position between the inlet and the outlet and the outlet to form a granulated sintering raw material; A method for producing a granulated sintered raw material, comprising the steps of: adding moisture of 0.5% by mass or more and 4.5% by mass or less to the sintered raw material when the temperature of the granulated sintered raw material discharged from the granulating device is 60°C or higher.

2. A method for producing sintered ore, comprising sintering the granulated sintered raw material granulated by the method for producing granulated sintered raw material according to claim 1 in a sintering machine to produce sintered ore.

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