JP2020012154A - Manufacturing method of sintered ore - Google Patents

Abstract

To provide a manufacturing method of a sintered ore for enhancing product yield and productivity of sintered ore in a two-stage injection two-stage ignition sintering method.SOLUTION: There is provided a two-stage injection two-stage ignition sintering method in which a granulated first blending raw material is supplied to a pallet constituting a Dwight Lloyd (DL) type sintering machine to form a lower stage layer 10, ignition is conducted from an upper part of the lower stage layer 10, and sintering of the lower stage layer 10 is initiated by aspirating air from lower side, a granulated second blending raw material is further supplied onto the lower stage layer 10 after ignition to form an upper stage layer 20, ignition is conducted on the upper stage layer 20, sintering of the upper stage layer 20 is initiated by aspirating air from lower side, and thereafter the upper stage layer 20 and the lower stage layer 10 are sintered by aspirating air from lower side, the second blending raw material forming the upper stage layer 20 contains 10 mass% or more of a granulate with a particle diameter (diameter) of 10 mm to 20 mm, and 10 mass% or less of granulate with a particle diameter of over 20 mm.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a sintered ore.

  Currently, the main raw material for blast furnace ironmaking is sinter. This sintered ore is usually produced as follows. First, iron ore (powder) as raw material, iron ore, iron-containing raw material such as steelmaking dust, flux containing silicon oxide and the like, auxiliary raw material such as lime containing CaO, and sintering sinter ore by combustion heat ( A carbon material as a coagulant to be coagulated) is mixed at a predetermined ratio, and the mixture is granulated to obtain a blended raw material. Next, the granulated compounded raw material is placed on a pallet of a Dwydroid (DL) type sintering machine that is suctioned downward from a hopper so as to form a raw material packed layer, and is placed on the placed raw material packed layer. From the (surface layer), the carbon material in the raw material packed layer is ignited. Then, oxygen is supplied by sucking air from below the pallet while continuously moving the pallet, and the combustion of the carbon material in the raw material packed bed proceeds from the upper part to the lower part, thereby burning the carbon material. Sintered by heat sequentially. The obtained sintered part (sinter cake) is pulverized to a predetermined particle size and sized by sieving or the like, and becomes sintered ore, which is a raw material for blast furnace iron making.

In a method for producing a sintered ore by using such a DL-type sintering machine, a multi-stage charging multi-stage ignition sintering method in which formation and ignition of a raw material packed layer are performed in two or more stages has been proposed (Patent Documents 1 to 4). 3).
In the multi-stage ignition sintering method, the compounded raw materials are sequentially loaded in the layer height direction of the sintering machine to form a multi-stage raw material packed layer, and the surface of each raw material layer is ignited by sucking air from below, thereby igniting each layer. This is a method of sintering by causing the sintering reaction to proceed frequently.

A two-stage charging two-stage ignition sintering method in which charging is performed in two stages and ignition is performed in two stages will be described with reference to FIG.
First, in order to granulate the compounded raw material for sinter ore production, in a separate system, a carbon-based coagulant such as coke breeze or the like is added to the iron-containing raw material, and water is added. Granulation is carried out by the first drum mixer 1A and the second drum mixer 2A, respectively.
Although not shown, the first compounded raw material granulated by the first drum mixer 1A is charged by a first hopper 1B onto a pallet laid with bedding ore to form a lower layer 10. .
The lower layer 10 formed on the pallet moves to a position below the first igniter 1C by moving the pallet in the downstream direction 5, and ignites the carbon-based aggregate of fuel by the first igniter 1C from above. Then, using a wind box below the pallet (not shown), the lower-layer combustion zone 10A is formed by the downward suction 6 that sucks air from below, and sintering of the lower layer 10 is started.
The sintering of the lower layer 10 is started, the sintering proceeds while the lower layer combustion zone 10A is lowered, and further moves to a position below the second hopper 2B. Then, the second compounded raw material granulated by the second drum mixer 2A is charged onto the lower layer 10 after ignition by the second hopper 2B to form the upper layer 20.
The carbon-based condensed material of the fuel is ignited from the upper portion of the formed upper layer 20 by the second igniter 2C, and the upper layer combustion zone 20A is formed by the downward suction 6, and the sintering of the upper layer 20 is started. .
Thereafter, lower suction 6 is performed to lower the lower combustion zone 10A and upper combustion zone 20A of the lower combustion layer 10 and the upper combustion layer 20, respectively, so that sintering proceeds, and the lower combustion zone 10A and the upper combustion zone 10A. When 20A reaches the lowermost portion of each layer, sintering by combustion of the carbon-based coagulant ends, and the sintered portion 3 is formed. The sintering of the sintered portion 3 proceeds by the residual heat even after the combustion of the carbon-based coagulant.

According to Patent Literature 1, the multi-stage charging / multi-stage ignition sintering method can change the supply ratio of the raw material of each layer, so that the sintering yield due to the impaired air permeability caused by the difference in particle size between the upper layer 20 and the lower layer 10 and the like. Is described as being able to cover the decrease in the yield and improving the yield.
Patent Document 2 discloses that in the two-stage charging two-stage ignition sintering method of charging in two stages and igniting in two stages of the multi-stage charging and multi-stage ignition sintering method, the sintering strength of the lower layer 10 is reduced. He points out the problem. For this reason, in order to improve the sintering strength of the sintered ore of the lower layer 10, the fixed carbon concentration in the steelmaking raw material to be sintered is set to 3.3% or less on the average in all layers, and the fixed carbon concentration of the upper layer 20 is reduced. It is described that the concentration is low and the fixed carbon concentration of the lower layer 10 is high.

Patent Literature 3 describes an oxygen enrichment technique for increasing the thickness of a raw material filling layer, increasing the moving speed of a pallet, and improving productivity. This oxygen-enrichment technique is used in the range from the pallet position when the depth of the front of the upper-layer combustion zone 20A becomes 10% of the thickness of the upper layer 20 downward from the surface layer to the end of the pallet to be discharged. The pressure difference in the layer thickness direction of the oxygen-containing gas supplied to the raw material packed bed in part or in whole is increased to 1.1 to 5.0 times the pressure difference in the previous portion. As described above, in the invention described in Patent Document 3, the suction pressure is increased, and the oxygen concentration in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) is increased to 8 vol% or more by increasing the gas flow rate. I have.
Patent Document 4 discloses that charging of a blended raw material is performed in one stage, and in a mining part, a middle zone of the single-stage raw material packed bed is ignited to form a combustion zone below the middle stage of the raw material packed bed. Describes that the oxygen concentration in the feed gas to the combustion zone below the middle stage of the raw material packed bed is increased to 9 vol%.

JP-A-47-26304 JP-A-62-60828 JP 2000-017343 A JP 2015-157980 A

  In the two-stage charging two-stage ignition sintering method, the air supplied for sintering the lower layer 10 is supplied as a gas having a reduced oxygen partial pressure by sintering the upper layer 20. . For this reason, in the lower layer 10, the carbon-based coagulant (coke breeze) is incompletely burned due to insufficient oxygen partial pressure in the gas, and the temperature is apt to decrease. As a result, the amount of heat required for sintering tends to be insufficient, and the sintering yield of the lower layer 10 is likely to decrease. Even in the two-stage ignition sintering method described in Patent Document 4 in which two-stage ignition is performed after charging in one stage, the amount of heat required for sintering the material-filled layer below the middle part of the material-filled layer is insufficient. The tendency is similar.

  In the method of Patent Document 2, the upper limit is set for the average concentration of all the carbon layers in the fixed carbon concentration, and the mixing ratio of coke in the upper layer 20 is reduced. However, the amount of heat supplied to the upper layer 20 is reduced. Since the cold strength of the sintered ore in the layer 20 was reduced, the implementation was difficult.

  On the other hand, if the oxygen is enriched by increasing the suction pressure as described in Patent Literature 3, the equipment load is large, and as described in Patent Literature 4, There is a problem in that enrichment requires equipment for supplying oxygen other than air.

  An object of the present invention is to increase the suction pressure, add oxygen to air to enrich oxygen, or reduce the mixing ratio of coke breeze in the upper layer 20 in the two-stage charging two-stage ignition sintering method. Instead, it is an object of the present invention to provide a method for producing a sintered ore that solves the basic problem that the oxygen concentration in the gas sucked (supplied) to the lower layer 10 is reduced and improves the product yield of sintering.

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

(1) Pallets that make up the Dwyroid (DL) sintering machine
The lower layer is formed by supplying the first compounded raw material obtained by mixing and granulating the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant,
Ignition from the upper part of the lower layer, start sintering of the lower layer by sucking air from below,
On the lower layer after ignition, an iron-containing raw material, an auxiliary material, and a second blended raw material obtained by mixing and granulating a carbon-based coagulant are further supplied to form an upper layer,
Ignition the upper layer and start sintering the upper layer by sucking air from below,
A method for producing a sintered ore by a two-stage charging two-stage ignition sintering method of thereafter sintering the upper layer and the lower layer by sucking air from below,
The second compounding raw material forming the upper layer contains 10% by mass or more of granules having a particle size (diameter) of 10 mm or more and 20 mm or less, and 10% by mass or less of granules having a particle size of more than 20 mm. A method for producing a sintered ore, comprising:
(2) The method for producing a sintered ore according to (1), wherein the particle size of the carbon-based coagulant contained in the second compounding raw material is 3 mm or more and 5 mm or less in median diameter.

  According to the present invention, both product yield and sintering productivity are improved. This is because the upper layer 20 contains granules having a particle size of 10 mm or more and 20 mm or less, but since the granules have a low specific surface area (surface area / volume), heat is transferred from the high-temperature gas to the raw material. Rapidly progresses to the lowermost layer, and the oxygen concentration in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) increases. As a result, the adverse effect of oxygen deficiency in the sintering of the lower layer 10 is reduced.

FIG. 1 is a schematic diagram of a DL-type sintering machine used in a two-stage charging two-stage ignition sintering method. The figure which shows the aspect which makes the particle diameter of the granulated material which comprises a 2nd raw material into the range of this invention by mix | blending a predetermined amount of fine ore, and granulating it with 2nd drum mixer 2A. The granulated material having a particle size (diameter) of 10 mm or more and 20 mm or less is added from the granulated material tank 4 to the granulated material granulated by the second drum mixer 2 </ b> A in an appropriate amount to constitute the second compounded raw material. The figure which shows the aspect which makes the particle size of a granulated object into the range of the present invention. The figure which shows the aspect used as a 2nd compounding raw material by a high-speed stirring mixer or a dish type granulator in the DL-type sintering machine used for a two-stage charging two-stage ignition sintering method. The figure which shows the aspect used as a 2nd compounding raw material by a high-speed stirring mixer and a dish type granulator in the DL-type sintering machine used for a two-stage charging two-stage ignition sintering method. The figure which shows the relationship between the particle size of the granulated material in a compounding raw material, and the oxygen concentration in the exhaust gas under it.

According to the present invention, a lower layer 10 is formed by supplying a first blended raw material obtained by mixing and granulating an iron-containing raw material, an auxiliary raw material, and a carbon-based coagulant material to a pallet constituting a Dwyroid (DL) type sintering machine. Then, sintering of the lower layer 10 is started by igniting from the upper part of the lower layer 10 and sucking air from below, and the iron-containing raw material, the auxiliary material, and the carbon-based coagulant are mixed on the lower layer 10 after ignition. The second compounded raw material thus granulated is further supplied to form the upper layer 20, the upper layer 20 is ignited, and the air is sucked from below to start sintering of the upper layer, and thereafter from below, This is a method for producing a sintered ore by a two-stage charging two-stage ignition sintering method in which an upper layer and a lower layer are sintered by sucking air.
In the two-stage charging two-stage ignition sintering method, the first compounding raw material forming the lower layer 10 and the second compounding raw material forming the upper layer 20 are used as iron-containing materials such as iron ore, returned ore, and steelmaking dust. Granulated by adding a carbon-based coagulant such as lime, flux, or other auxiliary materials, coke breeze, or anthracite as a carbonaceous material for combustion. As the iron-containing raw material, in addition to oxide ores such as hematite and magnetite, any iron ore such as iron ore containing hydroxide such as goethite can be used.

  In the two-stage charging two-stage ignition sintering method of the present invention, it is preferable that the layer thickness of the upper layer 20 is substantially equal to the layer thickness of the lower layer 10. For example, the layer thickness of the upper layer 20 is preferably in a range from 0.4 to 0.6 with respect to the total layer thickness of the upper layer 20 and the lower layer 10. When the total thickness of the upper layer 20 and the lower layer 10 is in the range of 0.4 or more and 0.6 or less, the production amount per unit time per unit area (sintering speed) is sufficiently improved, Since the residual oxygen in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) is further consumed during the sintering of the lower layer 10, the oxygen remaining in the exhaust gas from the lower layer 10 per unit sintered ore In addition, the amount of incomplete combustion gas in the exhaust gas from the lower layer 10 can be reduced. Then, since the sintering of the upper layer 20 and the lower layer 10 proceeds simultaneously, the amount of exhaust gas can be significantly reduced per ton of sintered ore. In addition, since the layer thickness ratio is substantially equal to the weight ratio (mass ratio) of the raw materials, the ratio between the upper layer 20 and the lower layer 10 may be defined by the mass ratio.

  In the two-stage charging two-stage ignition sintering method, the present inventors further studied various means for improving product yield and sintering productivity.

  In order to clarify the relationship between the oxygen concentration in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) and the particle size of the granulated material in the compounding raw material layer forming the upper layer 20, A single compounded raw material layer in which the particle size of the granulated material was changed was sintered, and the relationship between the oxygen concentrations in the exhaust gas was measured.

  The measurement test was conducted by granulating a sintering raw material containing 50% hematite concentrate (mostly fine ore having a particle size of 0.125 mm or less) with an Erich mixer (trade name) and a pan pelletizer. Sieving to diameters (5 to 10 mm, 10 to 15 mm, 15 to 20 mm), mixing of coke breeze (carbonaceous material) and limestone having a predetermined particle size, and a one-stage charging one-stage ignition pot test (diameter 300 mm, layer thickness 500 mm) ). FIG. 6 shows the results.

  As shown in FIG. 6, it can be seen that the oxygen concentration in the exhaust gas increases as the particle size of the granulated material constituting the blended raw material increases. From this fact, if the particle size of the granulated material constituting the second compounding raw material forming the upper layer 20 becomes larger, the oxygen concentration in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) becomes higher. It can be said that it increases.

  In the normal single-stage charging and single-stage ignition, when extremely large granules (GB) having a particle size of 10 mm or more are blended, the gap between the granules increases, which is effective in improving the air permeability, but the sintering speed is improved. Has the disadvantage that the product yield of the sintered ore decreases. Even if the granulated material having such a large particle size is arranged as the second compounding raw material and the upper layer 20 is formed, the problem of improving the product yield by using the upper layer 20 alone cannot be solved. Rather, the yield of the upper layer 20 alone decreases.

  However, in the two-stage charging and two-stage ignition sintering method, the yield of the lower layer 10 is significantly improved, and the product yield of the combined upper layer 20 and lower layer 10 is improved.

  For this reason, the second compounding raw material forming the upper layer 20 needs to contain at least 10% by mass of a granulated material having a particle size (diameter) of 10 mm or more and 20 mm or less. In the existing two-stage ignition sintering method, no particular raw material granulation treatment is performed. That is, general raw materials for sintering are granulated by a drum mixer. The compounded raw material hardly contains granules of 10 mm or more and 20 mm or less. The above definition of “10% by mass or more” excludes this. This ratio is a ratio when only the total amount of the second blended raw material is set to 100%, and is not a ratio to the total amount of the bedding or the first blended raw material.

  In the second compounding raw material forming the upper layer 20, if the granulated material having a particle diameter (diameter) of 10 mm or more and 20 mm or less is less than 10% by mass, the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10) Does not sufficiently increase, and the product yield does not improve sufficiently. The upper limit is not particularly limited, but is preferably 50% by mass or less. More preferably, it is at most 40% by mass.

  On the other hand, in the second compounded raw material forming the upper layer 20, when the ratio of the granulated material having a particle diameter (diameter) of more than 20 mm is included in more than 10% by mass, the exhaust gas of the upper layer 20 (= the lower layer 10 The increase in the oxygen concentration in the suction gas is slowed down. For this reason, the yield of the upper layer 20 is greatly reduced, and even if the yield of the lower layer 10 is improved, it cannot be compensated for, and the overall product yield of the combined upper layer 20 and lower layer 10 is reduced. It is more preferable that a granulated product having a particle size (diameter) exceeding 20 mm is not included.

  The particle size of the granulated material constituting the first compounding raw material forming the lower layer 10 is not particularly limited, but when the granulated material is coarse, the effect of improving the yield of the lower layer 10 is reduced. Therefore, as usual, it is preferable that the particle diameter (diameter) is less than 10 mm. That is, it is preferable that the first compounding raw material does not include a granulated material having a particle size of 10 mm or more.

  In the second compounding raw material forming the upper layer 20, a granulated material having a particle size (diameter) of 10 mm or more and 20 mm or less is included at 10% by mass or more, and a granulated material having a particle size of more than 20 mm is adjusted to 10% by mass or less. The method will be described.

  As shown in FIG. 2, the raw material for granulating the first compounded raw material and the raw material for granulating the second compounded raw material are a first raw material tank group 1D and a second raw material tank group, respectively. From 2D, they are supplied to the first drum mixer 1A and the second drum mixer 2A, respectively. The first raw material tank group 1D and the second raw material tank group 2D are respectively a raw material tank containing a predetermined type of hematite, a raw material tank containing a predetermined type of limonite, a raw material tank containing a flux, and lime. And a plurality of raw material tanks, such as a raw material tank containing powdered coke and a powdered coke tank (1D1, 2D1). The first raw material tank group 1D and the second raw material tank group 2D supply necessary types and amounts of raw materials from the respective raw material tanks.

  The particle size of the granules contained in the second compounding material is increased, the granules having a particle size (diameter) of 10 mm or more and 20 mm or less are included in an amount of 10% by mass or more, and the granules having a particle size of more than 20 mm are reduced to 10 mass%. % Or less, as shown in FIG. 2, a fine ore tank 2D2 for supplying fine ore is provided in the second raw material tank group 2D. Then, a larger amount of fine ore having a particle size of 0.125 mm or less, which acts as an adhering powder of the granulated material, is supplied from the fine ore tank 2D2 in a larger amount than in the related art, and granulated. That is, the particle size of the granulated material is increased by blending fine ore in an amount of 20% or more and 60% or less with respect to the mass of the entire second blending raw material forming the upper layer 20.

At this time, in order to smoothly promote the granulation, it is preferable to increase the granulation time in the second drum mixer 2A.
However, if the granulation time is too long or the amount of granulated water added at the time of granulation is too large, the granulated material having a particle size of more than 20 mm may exceed 10% by mass. These are adjusted according to the granulation equipment (drum mixer, high-speed stirring mixer, dish-type granulator) and the like.

Alternatively, in order to make the second compounded raw material contain 10% by mass or more of granules having a particle diameter (diameter) of 10 mm or more and 20 mm or less and 10% by mass or less of granules having a particle size of more than 20 mm, FIG. As shown in (2), a granulated material previously granulated into coarse particles may be added later.
That is, a granulated material having a particle diameter (diameter) of 10 mm or more and 20 mm or less prepared in advance on another line (another system) is prepared in the granulated material tank 4, and the second drum mixer is By adding an appropriate amount to the granulated product in 2A and supplying it to the second hopper 2B, the granulated product having a particle size (diameter) of 10 mm or more and 20 mm or less in the second compounding raw material is 10% by mass or more. The content of the granulated material having a particle size exceeding 20 mm can be reduced to 10% by mass or less.

  Further, as shown in FIGS. 4 and 5, the second compounding raw material forming the upper layer 20 is formed by a high-speed stirring mixer 2A1 and / or a dish granulator 2A2 instead of the second drum mixer 2A. It is preferred to granulate. 4 and 5, illustration of the first raw material tank group 1D and the second raw material tank group 2D is omitted.

  When the high-speed stirring mixer 2A1 and / or the dish-type granulator 2A2 are employed, the stirring power is high, so that the granulation strength is improved and the air permeability of the upper layer 20 is improved. As a result, productivity is further improved. In particular, as shown in FIG. 5, after granulation by the high-speed stirring mixer 2A1, and further granulation by the dish-type granulator 2A2, the productivity is enhanced when the second compounded raw material is granulated. Even better. Of course, as shown in FIG. 4, granulation may be performed using only one of the high-speed stirring mixer 2A1 and the dish-type granulator 2A2. As the high-speed stirring mixer 2A1, for example, an Erich mixer (trade name) can be used, and as the dish-type granulator 2A2, for example, a pan pelletizer can be used.

When granulating the second blended raw material, as shown in FIG. 2, when the fine ore is added and granulated by the second drum mixer 2A, the preferable granulated water content is as follows. It is 6.5 parts by mass or more and 9.5 parts by mass or less based on 100 parts by mass of the whole raw material, and the preferable granulation time is 30 seconds or more and 6 minutes or less before the addition of granulated water. After the addition of the grain moisture, the heating time is 1 minute or more and 10 minutes or less.
On the other hand, as shown in FIGS. 4 and 5, when the fine ore is added and granulated by a high-speed stirring mixer 2A1 (Erich mixer (trade name)) and / or a plate-type granulator 2A2 (pan pelletizer), The preferred amount of granulated water is 7.2 parts by mass or more and 8.8 parts by mass or less based on 100 parts by mass of the whole second compounding raw material. When granulation is performed using either an Erich mixer (trade name) or a pan pelletizer as shown in FIG. 4, a preferable granulation time is that the treatment before the addition of the granulated water is not performed, and the granulation time is 30 minutes after the addition of the water. It is not less than seconds and not more than 10 minutes. Further, as shown in FIG. 5, when granulating with an Erich mixer (trade name) and a pan pelletizer, the preferable granulation time is such that the treatment before the addition of the granulated water is not performed, and (Trade name)) for 30 seconds or more and 5 minutes or less, and for a pelletizer for 1 minute or more and 10 minutes or less.

  In the present invention, the particle size of the carbon-based aggregate contained in the second compounding raw material is preferably 3 mm or more and 5 mm or less in median diameter.

Conventionally, in normal sintering (single stage), in order to obtain an appropriate maximum temperature of sintering, the appropriate particle size of coke breeze is set to 3 mm or less (Yasuhito Shimomura, "Review-Analysis of Sintering Process ( 1st report) "Fuji Iron and Steel Technology, Vol.9 (1959), No.4, p.389-400). This is because the smaller the particle size, the higher the sintering temperature. However, in the present invention, the size of the carbon-based coagulant such as coke breeze in the upper layer 20 is as large as 3 mm or more in median diameter (median diameter = median value) including a size of 3 mm or more. Is preferred.
By increasing the size of the carbon-based aggregate, the burning speed of the carbon-based aggregate blended in the upper layer 20 becomes slower, and the oxygen consumption rate further decreases. Therefore, there is an effect of further increasing the oxygen concentration in the exhaust gas of the upper layer 20 (= the suction gas of the lower layer 10).
On the other hand, if the particle size of the carbon-based coagulant exceeds 5 mm, the sintering temperature when sintering the upper layer 20 may not be sufficiently obtained.

  Thus, by setting the particle size of the carbon-based coagulant contained in the second compounding raw material to a median diameter of 3 mm or more and 5 mm or less, both the product yield and the sintering productivity are further improved.

  Here, the carbon-based coagulant is a carbon material for combustion, and means at least one of coke breeze and anthracite. In addition, the particle size is determined by a particle size measurement (JIS Z 8801-1, JIS Z 8800-2) using a median diameter based on mass and using a sieve.

  Note that the first compounding raw material and the second compounding material may be the same material, or may be obtained by granulating different types of iron ore, auxiliary materials, and the like at different mixing ratios.

  The effect of the two-stage charging two-stage ignition sintering method of the present invention was verified by simulating a method for producing a sintered ore using a Dwyroid (DL) type sintering machine and performing a sintering pot test of φ300 mm under the following conditions. .

1) Basic conditions The charging and ignition methods are described below.
The layer thickness was two layers of 365 mm layer (for the upper layer 20) and 435 mm (lower layer 10).
A cylindrical lower pot having a diameter of 300 mm and a height of 500 mm and a cylindrical upper pot having a diameter of 300 mm and a height of 300 mm are prepared, and the first compounding material (for the lower layer 10, for a layer thickness of 435 mm) and A second compounding raw material (for the upper layer 20, for a layer thickness of 300 mm) is charged in advance. For the lower layer 10, 2 kg of bedding ore having a particle size of 10 to 15 mm is laid, and then the first raw material is charged. In addition, this bedding is not included in the layer thickness of 435 mm.
First, a pot charged with the first compounding material was set and ignited at 1100 ° C. for 1 minute. Immediately after the ignition is completed, the raw material for the layer thickness of 65 mm is charged into the lower pan, and then the upper pot with the second blended material (300 mm thick) is set on the lower pan, and immediately. Ignition was performed at 1100 ° C. for 1 minute.

The suction air volume at the time of sintering was kept constant at 1.3 Nm ³ / min from the start of ignition.
Blowing was stopped three minutes after the time when the temperature of the exhaust gas from the lower layer 10 reached a peak, and sintering was completed.

2) Compounding raw materials Table 1 shows the mixing conditions of the raw materials.
The test cases are a batch granulation case (the upper layer 20 and the lower layer 10 have the same composition) and a split granulation case (the upper layer 20 and the lower layer 10 have different compositions). In the batch granulation case, granulation is performed according to the batch granulation formulation (a) shown in Table 1, and after granulation, the mixture is divided into mass ratios of 45.4% and 54.6%, and then divided into second blends. The raw material (forming the upper layer 20) and the first compounding raw material (forming the lower layer 10) were used. In the split granulation case, the mixture was granulated by the blending for the upper layer (b) to obtain a second blending material, and the granulation was performed by the blending for the lower layer (c) to obtain the first blending material. In addition, the difference of brand of hematites A and D and the difference of brand of limonites B and C in Table 1 depend on the difference of production places. Also, peridotite forms flux.

  As the carbon-based coagulant, coke breeze is used, and the mixing ratio of coke breeze is common to batch granulation and divided granulation (upper layer 20 and lower layer 10). It was 5.0% by number. The 5% is distributed in average in proportion to the small measurement of 45.4% of the upper layer 20 and the small measurement of 54.6% of the lower layer 10 so that the coke breeze ratio of each layer becomes uniform. .

  Table 2 shows the particle size distribution of the carbon-based coagulant (coke breeze). The carbonaceous material to be used in the compounding for batch granulation (a) and the compound for the lower layer of the divided granulation case (c) is a carbon material a (normal sintering size) with a median diameter of 1.1 mm. Was. Depending on the test case, in addition to the above-mentioned carbonaceous material a coarse-grained carbonaceous material b having a [median diameter] of 3.4 mm was used depending on the test case. In Table 2, -0.25 mm is a carbon material having a size of less than 0.25 mm, and 0.25-1.0 mm is a carbon material having a size of 0.25 mm to 1.0 mm. Numerical values indicate mass%. The same applies to other particle sizes in Tables 2 and 3.

3) Granulation method Batch granulation case (granulated material a)
After mixing for 4 minutes the mixture of the compound for batch granulation (a) shown in Table 1 with a drum mixer (diameter 600 mm, rotation number 25 rpm), granulation water was added, and the mixture was further processed with a drum mixer for 4 minutes. a was granulated. The granulation water was added in a mass ratio of 7.0% with respect to a case where the total 100 in the batch granulation formulation (a) shown in Table 1 was 100%.

2. Split granulation case (granules b to e)
The granulated material b as the first compounding raw material forming the lower layer 10 was mixed with the compound for the lower layer (c) in Table 1 for 4 minutes using a drum mixer (600 mm in diameter, 25 rpm), and then mixed. Granulation was performed by adding granular water and further treating the mixture with a drum mixer for 4 minutes. The granulation water was added by an external number of 6.0% in terms of mass ratio, assuming that the total of 45.4 in the lower layer composition (C) shown in Table 1 was 100%.

The second compounding raw material forming the upper layer 20 is provided in two levels of granulation by a drum mixer and granulation by an Erich mixer (trade name) (high-speed stirring mixer 2A1) and a pan pelletizer (dish-type granulator 2A2). Was.
The granulation of the granulated material c, which is the second compounding material for forming the upper layer 20 by the drum mixer, is performed by mixing the compound for the upper layer (b) for 4 minutes, adding the granulated water, and further mixing with the drum mixer. Minutes. The granulated water content was 7.8% in terms of mass ratio, as compared with the case where the total of 54.6 in the lower layer composition (b) shown in Table 1 was 100% and the total number was 7.8%.

  The granulation of the granulated materials d and e, which are the second compounding raw materials for forming the upper layer 20 by an Erich mixer (trade name) and a pan pelletizer, is performed by an Erich mixer (trade name) (a stirring blade having a pan diameter of 800 mm and a stirring blade of 800 mm). The rotation speed is 20 rpm for the pan and 300 rpm for the stirring blade.) After the mixture for the upper layer (b) is processed for 1 minute together with the granulated water, the pelletizer (diameter 800 mm, rim height) is used. (150 mm, inclination angle 50 °, rotation number 25 rpm) for 5 minutes. The granulated water content was 8.5% (granulated material d) and 9 in terms of mass ratio in comparison with the case where the total of 54.6 in the lower layer composition (b) shown in Table 1 was 100%. 0.0% (granules e) were added at two levels.

Table 3 shows a summary of the above conditions and the particle size of the granulated product. In Table 3, +20 mm is the sum of granules larger than 20 mm and 10-20 mm is the sum of granules of 10-15 mm and 15-20 mm. The values in the table are% by mass.
Particle size distribution, after shrinking the granulated material to 300 g, after drying at 110 ° C. for 2 hours or more, sieving for 15 seconds with a low-tapping tow machine, 2 mm sieve, 5 mm sieve, The amount remaining on each of the 10 mm, 15 mm, and 20 mm sieves was defined as the yield of each particle size.

4) Evaluation method Product yield and productivity were evaluated for each case.
In the product yield, after sintering, the obtained sintered cake was subjected to a dropping treatment four times from a height of 2 m, and a particle size of +5 mm or more excluding bedding ore was defined as a sintered product. The value obtained by dividing the sintered product weight (the amount of sintering quality) by the weight of the sinter cake excluding the floor covering was defined as the product yield.
The sintering time was the time required from the ignition time of the lower layer 10 to the time when the temperature of the exhaust gas from the lower layer 10 peaked.
The production rate was calculated by dividing the product amount by the sintering time and the pot bottom area.

5) Test results The test conditions are shown in the upper part of Table 4, and the test results are shown in the lower part of Table 4. The increase rate is a value calculated by dividing the production rate of each example by the production rate of Comparative Example 1.

  As shown in Comparative Example 1, when the amount of the granulated material having a size of 10 mm or more and 20 mm or less is set to less than 10% by mass and the two-stage charging two-stage ignition is performed, Since the yield of the layer 10 is reduced, the overall product yield is low. This is an adverse effect due to the sintering of the lower layer 10 falling into low oxygen concentration sintering.

  On the other hand, as shown in Invention Example 1-1, when the granulated material c containing 10% or more of the granulated material having a particle size of 10 mm or more and 20 mm or less is used for the upper layer 20 and two-stage charging and two-stage ignition is performed, the air permeability is increased. The improvement and promotion of heat transfer shorten the sintering time and improve the product yield. By using the granulated material c for the upper layer 20 and using the coarse-grained carbonaceous material b for the upper layer 20 (Invention Example 1-2), the product yield is further improved.

  As shown in Inventive Example 2, the second compounded raw material forming the upper layer 20 is granulated with an Erich mixer (trade name) and a pan pelletizer, and the ratio of the granulated material having a particle size of 10 mm or more and 20 mm or less is further increased. When the increased granulated material d is used, the product yield is further improved as compared with Invention Examples 1-1 and 1-2. However, as shown in Comparative Example 2, coarsening proceeds excessively, and when the ratio of granules exceeding 20 mm exceeds 10% by mass (using granules e), the product yield deteriorates.

  According to the present invention, in the two-stage charging two-stage ignition sintering method, since the productivity of the sinter can be improved, it is possible to save energy and reduce costs. Have.

1A: first drum mixer, 1B: first hopper, 1C: first igniter, 1D: first raw material tank group, 1D1: powder coke tank, 10: lower layer, 10A: lower layer combustion zone, 2A: second drum mixer, 2A1: high-speed stirring mixer, 2A2: dish-type granulator, 2B: second hopper, 2C: second igniter, 2D: second raw material tank group, 2D1: coke breeze Tank, 2D2: fine ore tank, 20: upper layer, 20A: upper layer combustion zone, 3: sintering section, 4: granulated tank, 5: downstream direction, 6: downward suction

Claims (2)

Pallets that make up the Dwyroid (DL) sintering machine
The lower layer is formed by supplying the first compounded raw material obtained by mixing and granulating the iron-containing raw material, the auxiliary raw material, and the carbon-based coagulant,
Ignition from the upper part of the lower layer, start sintering of the lower layer by sucking air from below,
On the lower layer after ignition, an iron-containing raw material, an auxiliary material, and a second blended raw material obtained by mixing and granulating a carbon-based coagulant are further supplied to form an upper layer,
Ignition the upper layer and start sintering the upper layer by sucking air from below,
A method for producing a sintered ore by a two-stage charging two-stage ignition sintering method of thereafter sintering the upper layer and the lower layer by sucking air from below,
The second compounding raw material forming the upper layer contains 10% by mass or more of granules having a particle size (diameter) of 10 mm or more and 20 mm or less, and 10% by mass or less of granules having a particle size of more than 20 mm. A method for producing a sintered ore, comprising:   2. The method for producing a sintered ore according to claim 1, wherein a particle size of the carbon-based aggregate contained in the second compounding raw material is 3 mm or more and 5 mm or less in median diameter. 3.

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