JP2020117767A - Method for manufacturing sinter - Google Patents

Abstract

To improve a yield of sinter.SOLUTION: A method for manufacturing sinter includes: granulating a sintered material obtained by blending iron ore, a CaO-containing auxiliary material, an MgO-containing auxiliary material, a carbonaceous material and return ore; and segregately loading this into a pallet of a downward suction type sintering machine, followed by firing. A mean particle diameter (MSc) of the carbonaceous material exceeds 2.0 mm but not more than 2.8 mm. A ratio of a mean particle diameter (MSm) of the MgO-containing auxiliary material and the mean particle diameter (MSc) of the carbonaceous material is 0.9≤MSm/MSc≤1.8.SELECTED DRAWING: Figure 3

Description

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

Currently, the raw material for blast furnaces in Japan is mainly sinter. Sintered ore is made by mixing iron-containing raw material powder such as iron ore, which is the main raw material, auxiliary raw material, carbonaceous material, and return ore.

Sinter ore is usually manufactured as follows. First, with respect to iron-containing raw material powder such as iron ore, which is the main raw material, auxiliary raw materials, carbonaceous materials and return ore are mixed at a predetermined ratio, and further, suitable water is added to the mixture to granulate the raw material mixture (hereinafter, Also referred to as sintering raw material).

Next, this sintering raw material is loaded into a downward suction type Dwightroid (DL) type sintering machine (hereinafter, also referred to as a sintering machine). Specifically, a predetermined amount of the sintering raw material is cut out by a raw material cutting device from a hopper directly above the sintering machine, and is charged and placed on a pallet via a charging chute to form a raw material packed layer. .. The carbonaceous material of the upper layer (surface layer) in the formed raw material packed bed is ignited by an ignition furnace. Then, oxygen is supplied by sucking air from below the pallet while continuously moving the pallet, and the combustion of the carbonaceous material in the raw material packed bed proceeds from the upper layer to the lower layer. The raw material packed layer is sequentially sintered from the upper layer side to the lower layer side by the combustion heat of the carbonaceous material. The obtained sintered part (sinter cake) is crushed to a predetermined particle size and sized by sieving, and a sinter having a certain particle size or more becomes a blast furnace raw material. In addition, those having a particle size smaller than a certain value (usually -5 mm) are recovered as return ore and reused as a part of the sintering raw material.

Here, the sintering raw material is charged on the pallet via the inclined surface of the charging chute. Therefore, the charged sintering raw material forms a slope when it is placed on the pallet, and the rolling classification action occurs on this slope. Due to this rolling classification action, grain size segregation occurs in the layer thickness (layer height) direction of the raw material packed layer, and the sintering raw material with a small grain size is on the upper layer side of the raw material packed layer, and the one with a large grain size is the raw material packed layer. It is easy to insert it in the lower layer.

Further, in the sintering process by the downward suction type sintering machine, since air is sucked from below, the amount of heat received by the raw material differs depending on the layer thickness direction of the raw material filling layer. On the upper layer side, the heat quantity tends to be insufficient due to the sucked low temperature air, whereas on the lower layer side, the heat quantity becomes excessive due to the residual heat of combustion on the upper layer side.

Due to the segregation of the sintering raw material in the layer thickness direction and the difference in the amount of heat received in the layer thickness direction, a deviation in the amount of the melt of the iron ore, which is the main raw material, occurs in the layer thickness direction, and firing in the layer thickness direction The yield and quality of the sintered ore will vary. As a result, the overall yield may decrease, but in order to prevent this, a technique is disclosed for controlling the distribution of the sintering raw material in the layer thickness direction and the concentration of the component that influences the melting point.

For example, the grain size of the carbonaceous material contained in the sintering raw material before granulation is adjusted (Patent Document 1), the grain size of the MgO-containing mineral is adjusted (Patent Document 2), and the yield of the sintered ore is adjusted. A technique for improving the above is disclosed.

In Patent Document 1, by controlling the ratio d _C /d _O of the average particle size d _C of the carbonaceous material and the average particle size d _O of the ore within an appropriate range, the height direction in the sintered packed bed A technique is disclosed in which a carbonaceous material concentration distribution is appropriately maintained and a sintered ore can be stably manufactured without deteriorating the yield and productivity of the sintered ore.

In Patent Document 2, a sintering machine is provided with a sloping chute having a predetermined screen, and further, the grain size of MgO-containing mineral is adjusted, and the sintering pallet is charged together with other sintering raw materials to perform firing. A technique for improving the product strength, product yield, production efficiency, and coke consumption rate of the sintered ore by setting the MgO average concentration of the sintered ore in the upper part of the binding pallet to 1 wt% or less is disclosed.

JP, 2009-185356, A Japanese Patent Laid-Open No. 08-60261

In the technique described in Patent Document 1 above, the appropriate range for the ratio of the average particle size of the carbonaceous material and the average particle size of the ore is set, and in the technique described in Patent Document 2 above, the MgO-containing mineral It has been shown to adjust the particle size. However, for the production method of sinter that enables improvement of the yield of sinter by adjusting the particle size of the two materials, carbonaceous materials and MgO-containing auxiliary materials (eggite, Ni slag, etc.) Was not proposed until.

An object of the present invention is to produce a sintered ore that can improve the yield in a method for producing a sintered ore in which a compounded raw material is granulated and charged into a pallet of a downward suction type sintering machine and fired. Is to provide a method.

The gist of the present invention is as follows.
(1) Sintering in which iron ore, CaO-containing auxiliary raw material, MgO-containing auxiliary raw material, carbonaceous material, and sinter raw material are granulated, charged into a pallet of a lower suction type sintering machine, and sintered. In the method of producing ore,
The average particle size (MSc) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less,
The ratio of the average particle size (MSm) of the MgO-containing auxiliary material to the average particle size (MSc) of the carbonaceous material is 0.9≦MSm/MSc≦1.8 Method.
(2) The method for producing a sinter according to (1), characterized in that the MgO-containing auxiliary material is olivine.
(3) The method for producing a sinter according to (1), wherein the MgO-containing auxiliary material is nickel slag.

According to the present invention, the grain size segregation can be controlled and the yield can be improved by adjusting the grain sizes of the carbonaceous material and the MgO-containing auxiliary raw material.

It is a figure which shows typically the sieving apparatus used in this experiment. It is a figure which shows the relationship between the average particle diameter (MSc) of coke and a product yield. It is a figure which shows the relationship between the average particle diameter (MSc) of coke and the average particle diameter (MSm) of peridotite.

The details of how the problems were solved are described below.
Sintered ore is made by mixing iron-containing raw material powder such as iron ore, which is the main raw material, auxiliary raw material, carbonaceous material, and return ore. The iron ore accounts for about 70% by mass or more and 85% by mass or less of the sintering raw material, and the one having a particle size range of 10 mm or less is used. Usually, 5 to 10 types of iron ore brands are mixed, and the average particle size of the iron ore is set in the range of 1.3 mm or more and 2.5 mm or less depending on the mixing ratio.

The carbonaceous material is a material mainly containing a carbon component (free carbon) which is a heat source for melt generation, such as coke and anthracite which are usually used, and coal char. During the sintering process, the carbonaceous material serves as a heat source for generating a melt around the iron ore in the raw material packed bed. The auxiliary raw materials are CaO-containing auxiliary raw materials such as limestone and quicklime, and MgO-containing auxiliary raw materials such as granite and nickel slag. As shown in Table 1, since the MgO-containing secondary raw materials, that is, granite and nickel slag, are raw materials whose main chemical components are MgO and SiO ₂ after heating, they show similar properties.

It is known that MgO contained in the MgO-containing auxiliary material raises the melting point and reduces the amount of melt produced. Therefore, in the melt generation (sintering) reaction of the sintering raw material, the MgO content and the carbonaceous material content affect the amount of melt generated, that is, the strength of the sintered ore, and the yield. It is an important element that is directly connected to. Further, the segregation of the grain size of the sintering raw material in the layer thickness direction is the same as that of the carbonaceous material and the MgO-containing auxiliary raw material which are the sintering raw materials. Are known.

The present inventor has focused on the particle size segregation of the carbonaceous material and the MgO-containing auxiliary material as described above, that is, the endowment amount in the layer thickness direction changes depending on the particle size. By adjusting both the particle size (MSc) of the carbonaceous material and the particle size (MSm) of the MgO-containing auxiliary material, the free carbon, which is the heat source that generates the melt, and the melting point, which decreases the amount of melt generated It is possible to control the segregation state of both components of MgO and MgO in the layer thickness direction. As a result, it was thought that the amount of melt generated in the layer thickness direction could be controlled and the yield of the sintered ore could be improved.

Therefore, the present inventor investigated the range of the appropriate particle size ratio for the particle size of carbonaceous material and the particle size of peridotite. Specifically, a plurality of carbonaceous materials having different grain sizes and MgO-containing auxiliary raw materials having different grain sizes (in this example, granite is used) are prepared, and a sintering pot test is performed on the sintering raw materials prepared by combining them. Was carried out and each yield in the sintering process was examined. As a result, even when using a carbonaceous material having a particle size larger than the conventional particle size (average particle size of 1.5 mm or more and 1.8 mm or less) of more than 2.0 mm and 2.8 mm or less, the MgO-containing auxiliary raw material is used. Particle size (hereinafter, also referred to as "average particle size of MgO-containing auxiliary material" or "MSm") and the particle size of carbon material (hereinafter also referred to as "average particle size of carbon material" or "MSc") , It has been found that the effect of improving the yield of the sintered ore can be obtained by adjusting so that "0.9≤MSm/MSc≤1.8". Here, if the average particle size of the carbonaceous material is 2.0 mm or less, the amount of carbonaceous material in the lower layer of the pallet decreases, the yield decreases due to insufficient heat in the lower layer, and if it exceeds 2.8 mm, The amount of carbonaceous material in the lower layer may be too large, and seizure may occur on the pallet's great surface. Further, if the value of "MSm/MSc" is less than 0.9, the amount of melt produced is too large, which deteriorates the air permeability of the sintered layer and lowers the yield. When the value of “MSm/MSc” is larger than 1.8, the amount of melt produced is small and unsintered portions are generated, resulting in a low yield. The present application was invented based on such knowledge.

In the present invention, the inventor has adopted the ratio (MSm/MSc) of the average particle size of the MgO-containing auxiliary material to the average particle size of the carbonaceous material as an index for improving the yield. By the way, the particle size segregation behavior in each raw material packed bed is a difference in particle size with respect to the particle size of the iron ore as the main material (hereinafter, also referred to as “average particle size of iron ore” or “MSo”), for example, particle size ratio. It is appropriate to consider that it is controlled by MSm/MSo and MSc/MSo. Therefore, the relative segregation behavior of the carbonaceous material and the MgO-containing auxiliary material is governed by (MSm/MSo)/(MSc/MSo) in detail. At this time, MSo is canceled by the denominator, so that the index adopted in the present application is MSm/MSc. That is, the ratio (MSm/MSc) of the average particle size of the MgO-containing auxiliary material to the average particle size of the carbonaceous material, which is an index in the present invention, is universal regardless of the particle size of the iron ore.

As an example, the basis for determining a suitable range of the ratio of the average particle size (MSm) of the MgO-containing auxiliary material to the average particle size (MSc) of the carbonaceous material will be shown. In this example, a compounding raw material filling layer is formed by a charging experiment device capable of reproducing the charging state of the compounding raw material, and the formed compounding raw material filling layer is fired by a general sintering experimental device (sinter pot test). Therefore, we adopted a method to reproduce the actual sintering machine.

(Preparation of raw materials)
The contents of the test conducted by the present inventor are as follows.
First, in this test, coke was used as the carbonaceous material and granite was used as the MgO-containing auxiliary raw material among the mixed raw materials. As shown in Table 2, three types of coke and granite having different particle sizes were prepared.
Table 2 shows the particle size distribution and average particle size of the granite and coke used in this test.

As shown in Table 2, samples of three types of apatite (fine grain (M1), medium grain (M2), coarse grain (M3)) and three types of coke (fine grain (C1), medium grain (C2) ), a sample of coarse particles (C3)) was prepared. Table 2 shows the particle size when olivine (M1, M2, M3) and coke (C1, C2, C3) samples, respectively, are sieved using six types of sieves with different sieve meshes (opening size). The distribution is shown. As shown in Table 2, the particle size as the boundary value of the particle size classification is 0.25 mm, 0.5 mm, 1 mm, 3 mm, 5 mm, and 7 mm, and these values are the meshes of the sieve used for classification. .. For example, the particle size classification "1 mm-0.5 mm" means on the sieve when sieved with a sieve of 0.5 mm and under the sieve when sieved with a sieve of 1 mm. As for the 0.25 mm, 0.5 mm, and 1 mm sieves, those specified in JIS Z 8801 are used. It is an average value calculated by loading the median value of the particle size classification with the mass fraction for each particle size classification. In the calculation, it is assumed that there is no difference in specific gravity between particle sizes.

As shown in Table 2, the average particle size (MS) of the fine granules (M1), medium particles (M2), and coarse particles (M3) of the granite is 0.45 mm, 2.04 mm, and 3. It is 02 mm. The average particle size (MS) of the fine coke particles (C1), medium particles (C2), and coarse particles (C3) is 1.63 mm, 2.01 mm, and 2.55 mm, respectively.

(Raw material blending and granulation)
Table 3 shows the composition of the raw materials. With respect to coke and apatite, nine types of compounding raw materials prepared by combining the above-mentioned three types having different particle sizes were prepared, and tests were conducted for each. The iron ore used had an average particle size of 1.5 mm.

As shown in Table 3, the raw materials excluding the return ore and the coke were set to 100% by mass, and the mixing ratios of the return ore and the coke were set to 15.0% by mass and 3.6% by mass, respectively. After mixing these blended raw materials with a universal kneader, a drum type granulator with a diameter of 1 m was used to target a moisture content of 7.5 mass% for a predetermined time (3 minutes), and a pot firing test was performed. A compounding raw material (sintering raw material) was prepared.

(Classification of granulated sintering raw material)
In order to reproduce the particle size segregation in the layer thickness direction of the compounded raw material packed bed that occurs when charging the pallet, a slit bar type compounded raw material sieving device (hereinafter, also referred to as a sieving device) is used for granulation and firing. The raw material was classified.

FIG. 1 is a diagram schematically showing a sieving apparatus 1 used in this experiment. As shown in FIG. 1, the sieving device 1 includes a supply unit 3 for supplying the sintering raw material 2 and a slit 5 for classifying the supplied sintering raw material 2. Below the slits 5, a plurality of recovery boxes 7 (six in this embodiment) for recovering the sintering raw material 2 classified by the slits 5 are arranged side by side. The slits 5 are arranged so as to be inclined downward from the supply unit 3, extend perpendicularly to the moving direction of the sintering raw material, and have slit bars 5a arranged at equal intervals in the moving direction. As shown in FIG. 1, the supplied sintering raw material 2 moves on the slit bar 5a from the upstream side (upper left in the figure) toward the downstream side (lower right in the figure). During this movement, the sintering raw material 2 having a smaller particle size (particle size) sequentially passes through the slit 5 and drops into the recovery box 7. In this way, the sintering raw material 2 is divided into the recovery boxes 7 according to the particle size. Specifically, fine particles having a small particle size are collected in the recovery box 7 on the upstream side of the slit 5, and coarse particles having a large particle size are collected in the recovery box 7 on the downstream side. The recovered sintering raw material in the recovery box 7 was loaded into the sintering pot described later in order from the coarse grain side, and the same particle size segregation and raw material component segregation as in the raw material packed bed of the actual sintering machine were reproduced ( Layer thickness 435 mm). Note that the inclination angle of the slit 5 was set to 40°, which was a result of preliminary examination and at which continuous segregation was obtained.

(Sintering pot test)
Table 4 shows the specifications and test conditions of the test apparatus used for the sintering pot test. The sintering process was used to simulate the firing process of the raw material packed bed in an actual machine. The surface of the sintered layer after being filled with the sintering raw material was ignited, and air was sucked by a blower from a wind box installed at the bottom of the sintering pot to burn the raw material packed layer.

(Measurement of product yield of sintered ore)
The product yield was measured as follows. The sintered cake after firing was divided into three equal parts in the height direction (layer thickness direction) to obtain samples (upper layer portion, middle layer portion, lower layer portion). For each sample, after the falling weight test (3 kg of weight was dropped onto the sample from a height of 2 m four times repeatedly), it was passed through a sieve with an opening of 5 mm, and particles of sinter ore (+5 mm particles) remaining on the sieve, The mass% based on the total mass of the sinter cake was defined as the product yield (+5 mm%) here.

(Evaluation of product yield)
Table 5 shows the result of the product yield test of the sintered ore sintered from the above-mentioned nine kinds of sintering raw materials.
In Experiments 1 to 3, Experiments 4 to 6 and Experiments 7 to 9, samples of fine coke grain size (C1), medium grain size (C2), and coarse grain size (C3) were used, respectively. Further, in Experiments 1, 4, 7, Experiments 2, 5, 8, and Experiments 3, 6, 9, the particle size of the granite is fine (M1), medium (M2), and coarse (M3), respectively. Using the sample. In addition, under the same conditions as in Experiment 9, an experiment in which coke having coarse particles (average particle diameter exceeding 3.0 mm) was used more than that of coarse particles (C3) was also performed, and is shown in Table 5 as Experiment 10. In addition, this average particle diameter is the weighted average of the median values of the same particle size classification as described above by mass fraction.

In Table 5, those satisfying the following requirements 1 and 2 are taken as examples, and the others are taken as comparative examples. The product yield in Table 5 is a value obtained by averaging the yields (+5 mm%) of the samples of the upper layer portion, the middle layer portion, and the lower layer portion.
Requirement 1: Average particle size (MSc) of carbonaceous material exceeds 2.0 mm and 2.8 mm or less Requirement 2: Average particle size (MSm) of granite is 0.9 times or more of average particle size (MSc) of carbonaceous material 1.8 times or less

FIG. 2 is a diagram showing the relationship between the average particle size (MSc) of coke and the product yield. As shown in FIG. 2, the average particle size (MSc) of coke is set to more than 2.0 mm and 2.8 mm or less, and the ratio between the average particle size (MSc) of coke and the average particle size (MSm) of peridotite is calculated. It was found that the adjustment yields a high product yield of 70% by mass or more. In particular, in Experiments 5, 6, and 9 which are Examples of the present invention, it was found that the product yield could be 70% by mass or more. In addition, in Experiment 10 in which coke having an average particle size (MSc) of more than 2.8 mm was used, seizure occurred on the grate surface of the lower layer, air flow in the sintering pot was reduced, and the yield was reduced. The decline was remarkable.

FIG. 3 is a diagram showing the relationship between the average particle size (MSc) of coke and the average particle size (MSm) of peridotite. The straight line L1 in the figure shows a straight line with a slope of 1.8, and the straight line L2 shows a straight line with a slope of 0.9. Experiments 5, 6, and 9, which are examples of the present invention, are located between the straight line L1 and the straight line L2. In order to secure a high yield of the product, the average particle size (MSc) of coke is set to be 2.0 mm or more and 2.8 mm or less, and the average particle size (MSm) of the granite (MSm) relative to the average particle size (MSc) of the coke is set. It was confirmed that the ratio needs to be in the range of 0.9≦MSm/MSc≦1.8.

DESCRIPTION OF SYMBOLS 1... Slit bar type compounded raw material sieving device (sieving device), 2... Sintering raw material, 3... Supply part, 5... Slit, 5a... Slit bar, 7... Recovery box

Claims (3)

Manufacture of sintered ore in which iron ore, CaO-containing auxiliary raw material, MgO-containing auxiliary raw material, carbonaceous material and sinter raw material are granulated, charged into a pallet of a downward suction type sintering machine, and fired. In the method
The average particle size (MSc) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less,
The ratio of the average particle size (MSm) of the MgO-containing auxiliary material to the average particle size (MSc) of the carbonaceous material is 0.9≦MSm/MSc≦1.8 Method. The method for producing a sintered ore according to claim 1, wherein the MgO-containing auxiliary raw material is granite. The method for producing a sintered ore according to claim 1, wherein the MgO-containing auxiliary material is nickel slag.

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