JP7205362B2 - Method for producing sintered ore - Google Patents

Description

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

Currently, sintered ore is the main raw material for blast furnaces in Japan. Sintered ore is made by blending iron-containing raw material powder such as iron ore as the main raw material, auxiliary raw materials, carbonaceous material and return ore.

Sintered ore is usually manufactured as follows. First, iron-containing raw material powder such as iron ore, which is the main raw material, is mixed with auxiliary raw materials, carbonaceous material and return ore in a predetermined ratio, and then an appropriate amount of water is added to the mixture and granulated to form a mixed raw material (hereinafter referred to as a mixed raw material). Also called sintering raw material).

Next, this raw material for sintering is charged into a downward suction type Dwight Lloyd (DL) type sintering machine (hereinafter also referred to as a sintering machine). Specifically, a fixed amount of sintering raw material is cut out by a raw material cutting device from a hopper immediately above the sintering machine, and charged and placed on a pallet through a charging chute to form a raw material packed layer. . The upper layer (surface layer) of the carbon material in the formed raw material packed bed is ignited by an ignition furnace. Oxygen is supplied by sucking air from below the pallets while the pallets are continuously moved, and the combustion of the carbon material in the raw material packed bed proceeds from the upper layer to the lower layer. By the heat of combustion of the carbonaceous material, the raw material packed bed is sequentially sintered from the upper layer side to the lower layer side. The obtained sintered part (sinter cake) is pulverized to a predetermined particle size and sieved to obtain sintered ore having a certain particle size or more, which is a raw material for blast furnaces. Those with a particle size smaller than a certain size (usually -5 mm) are collected as return ore and reused as part of the raw material for sintering.

Here, the raw material for sintering is charged onto the pallet through the inclined surface of the charging chute. Therefore, the charged sintering raw material forms a slope when it is placed on the pallet, and a 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 bed. It becomes easy to charge to the lower layer side.

In addition, in the sintering process using a downward suction type sintering machine, since air is sucked from below, the amount of heat received by the raw material varies depending on the layer thickness direction of the raw material packed layer. On the upper layer side, the amount of heat tends to be insufficient due to the sucked low-temperature air, whereas on the lower layer side, the amount of heat is excessive due to the residual heat of combustion on the upper layer side.

Due to the grain size 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, the amount of iron ore melt, which is the main raw material, is uneven in the layer thickness direction, and sintering occurs in the layer thickness direction. The yield and quality of sintered ore will differ. As a result, the yield as a whole may be lowered. In order to prevent this, techniques have been disclosed for controlling the distribution of the sintering raw material in the layer thickness direction and the concentration of components that affect the melting point.

For example, by adjusting the particle size of the carbonaceous material contained in the sintering raw material before granulation (Patent Document 1), or by adjusting the particle size of coke or limestone (Patent Document 2), sintered ore can be obtained. Techniques for manufacturing are disclosed.

Patent Documents 1 and 2 disclose techniques for producing sintered ore with excellent high-temperature reduction/softening and melting properties by adjusting the particle size distribution of coke and limestone mixed in the sintering raw material before firing, thereby increasing the generation of micropores. is disclosed.

JP-A-07-3342 JP-A-08-120350

The techniques described in Patent Literature 1 and Patent Literature 2 above show that the particle sizes of the carbonaceous material and the limestone are adjusted separately. However, there has been no proposal for a method for producing sintered ore that enables an improvement in the yield of sintered ore by adjusting the combination of two raw materials, carbonaceous material and limestone, to an appropriate particle size combination. .

The object of the present invention is to produce sintered ore that enables improvement of yield in a method for producing sintered ore in which mixed raw materials are granulated, charged into a pallet of a downward suction type sintering machine, and fired. to provide a method.

The gist of the present invention is as follows.
In a method for producing sintered ore, a sintering raw material mixed with iron ore, limestone, MgO-containing auxiliary raw material, carbonaceous material and return ore is granulated, charged into a pallet of a downward suction sintering machine, and fired,
The average particle diameter (MS _C ) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less,
Sintered ore characterized in that the ratio of the average particle size of the limestone (MS _L ) and the average particle size of the carbonaceous material (MS _C ) is 0.94 ≤ MS _L /MS _C ≤ 1.2 Production method.

According to the present invention, by adjusting carbonaceous material and limestone based on their particle size ratio, particle size segregation of both raw materials can be controlled and the yield can be improved.

It is a figure which shows typically the sieving apparatus used in this experiment. FIG. 3 is a diagram showing the relationship between the average coke particle size (MS _C ) and product yield. FIG. 3 is a diagram showing the relationship between the average particle size of coke (MS _C ) and the average particle size of limestone (MS _L ).

The details of how the problem was solved are described below.

Sintered ore is made by blending iron-containing raw material powder such as iron ore as the main raw material, auxiliary raw materials, carbonaceous material and return ore. Iron ore accounts for about 70% by mass or more and 85% by mass or less of the raw material for sintering, and those with a particle size range of 10 mm or less are used. Normally, 5 to 10 types of iron ore brands are mixed, and the average particle size of iron ore is in the range of 1.3 mm or more and 2.5 mm or less depending on the mixing ratio. The auxiliary materials are CaO-containing auxiliary materials such as limestone and quicklime, and MgO-containing auxiliary materials such as peridotite and nickel slag. The carbon material is a material mainly composed of a carbon component (free carbon) that serves as a heat source for sintering, such as coke and anthracite, which are usually used, and coal char.

In the sintering process, the carbonaceous material serves as a heat source that generates a melt around the iron ore in the raw material packed bed. Limestone is a raw material for the melt and is melted by burning the carbonaceous material. CaO in limestone reacts with Fe ₂ O ₃ in iron ore to form a calcium ferrite (CaO.Fe ₂ O ₃ )-based melt, and this melt agglomerates the compounding raw material (sintering raw material). advances. Therefore, in the melt formation (sintering) reaction of the sintering raw material, limestone and carbonaceous material are important factors that affect the amount of melt generated, that is, the strength of the fired sintered ore, and are directly linked to the yield. It has become.

If the grain size of limestone is small, it will melt easily. In addition, if the limestone has a large particle size and remains undissolved, the amount of melt produced decreases. Due to the insufficient amount of melt produced, an unsintered portion remains in the sinter cake, resulting in a decrease in yield due to insufficient strength. Here, the grain size segregation of the sintering raw material in the layer thickness direction described above is the same for carbonaceous materials and limestone, which are sintering raw materials, and it is possible that coarse grains are concentrated in the lower layer and fine grains are concentrated in the upper layer. Are known.

The present inventor paid attention to the particle size segregation of the carbonaceous material and limestone as described above, that is, the existence amount in the layer thickness direction varies depending on the particle size. By segregating the coke, which is the heat source for generating the melt, and the limestone, which is the raw material of the melt, in the layer thickness direction, it is possible to prevent undissolved limestone and generate the melt necessary for sintering. I thought I could. That is, by adjusting both the particle size of the carbonaceous material (average particle size MS _C ) and the particle size of the limestone (average particle size MS _L ) based on the particle size ratio, the free carbon, which is the heat source for generating the melt, and , CaO, which is the raw material of the melt, can be controlled so that the segregation states in the layer thickness direction are the same. As a result, it is possible to control the amount of melt generated in the layer thickness direction, and it is possible to improve the yield of sintered ore.

Therefore, the present inventor investigated the appropriate particle size ratio range for the particle size of the carbonaceous material and the particle size of the limestone. Specifically, a plurality of carbonaceous materials with different grain sizes and limestone with different grain sizes were prepared, and a sintering pot test was performed on the sintering raw materials prepared by combining these, respectively, and each yield in the sintering process was investigated. As a result, even when using a carbonaceous material with an average particle size of more than 2.0 mm and 2.8 mm or less, which is larger than the conventional particle size (average particle size of 1.5 mm or more and 1.8 mm or less), the grain size of limestone ( Hereinafter, the ratio between the “mean particle size of limestone” and “MS _L ”) and the particle size of carbonaceous material (hereinafter also referred to as “mean particle size of carbonaceous material” or “MS _C ”) is “0.94 ≤ MS _L /MS _C ≤ 1.2”, it was found that the effect of improving the yield of sintered ore can be obtained. 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, and the yield decreases due to the lack of heat in the lower layer. There is a possibility that the amount of carbonaceous material in the lower layer will become too large, causing seizure on the grate surface of the pallet and making stable operation difficult. Further, if the value of "MS _L /MS _C " is less than 0.94, the grain size of the limestone is small and fills the gaps between the raw material particles, so the amount of melt generated is too large, resulting in the formation of the raw material packed bed. Breathability deteriorates and the yield decreases. If the value of “MS _L /MS _C ” is greater than 1.2, the grain size of limestone becomes large, so limestone becomes difficult to dissolve, the amount of melt produced decreases, unsintered portions occur, and the yield decreases. descend. The present application has been invented based on such findings.

In the present invention, the inventor adopts the ratio of the average grain size of limestone to the average grain size of carbonaceous material (MS _L /MS _C ) as an index for improving the yield. Although various representative indices representing particle size are conceivable, in terms of dealing with the phenomenon governed by particle size segregation at the time of raw material charging, the average particle size described later is preferable to the expression using the particle size configuration adopted in Patent Documents 1 and 2. This is because (MS) was thought to be a more suitable particle size index. Here, the grain size segregation behavior in each raw material packed bed is the difference in grain size with respect to the grain size of iron ore, which is the main raw material (hereinafter also referred to as “average grain size of iron ore” or “MSo”), for example, the grain size ratio. It is reasonable to think that they are governed by certain MS _L /MSo and MS _C /MSo. Therefore, the relative segregation behavior between carbonaceous material and limestone is, in detail, governed by (MS _L /MSo)/(MS _C /MSo). At this time, _MSo is canceled out by the denominator and numerator, so the index used in the present application is MSL/ _MSC . That is, the ratio of the average particle size of limestone to the average particle size of carbonaceous material (MS _L /MS _C ), which is an index in the present invention, has universality regardless of the particle size of iron ore.

As an example, the grounds for determining a suitable range of the ratio between the average particle size of limestone (MS _L ) and the average particle size of carbonaceous material (MS _C ) will be shown. In this example, a mixed raw material packed layer is formed with a charging experimental apparatus that can reproduce the charging state of mixed raw materials, and the formed mixed raw material packed layer is fired with a general sintering experimental apparatus (sintering pot test). By doing so, we adopted a method to reproduce an actual sintering machine.

(Preparation of raw materials)
The contents of the test conducted by the inventor are as follows.
First, in this test, coke was used as the carbonaceous material and limestone was used as the CaO-containing auxiliary material among the raw materials to be mixed. As shown in Table 1, three types of coke and limestone with different particle sizes were prepared.
Table 1 shows the particle size distribution and average particle size of limestone and coke used in this test.

As shown in Table 1, three types of limestone (fine grain (L1), medium grain (L2), coarse grain (L3)) samples and three types of coke (fine grain (C1), medium grain (C2) , coarse grains (C3)) were prepared. Table 1 shows the particle size distribution when limestone (L1, L2, L3) and coke (C1, C2, C3) samples are sieved using six different sieves with different meshes (mesh opening dimensions). indicates As shown in Table 1, the particle sizes that are the boundary values of the particle size division are 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 division "1 mm-0.5 mm" means above the sieve when sieved with a sieve with a sieve of 0.5 mm, and under sieve when sieving with a sieve with a sieve of 1 mm. The sieves of 0.25 mm, 0.5 mm, and 1 mm specified in JIS Z 8801 are used. The average particle size (MS) is the average value calculated by weighting the median value of each particle size category by the mass fraction of each particle size category. The calculation assumes that there is no specific gravity difference for each particle size.

As shown in Table 1, the average particle size (MS) of the limestone fine grain (L1), medium grain (L2), and coarse grain (L3) samples is 1.61 mm, 2.08 mm, and 2.41 mm, respectively. is. The average particle diameters (MS) of fine (C1), medium (C2) and coarse (C3) coke samples are 1.63 mm, 2.01 mm and 2.55 mm, respectively.

(Raw material blending and granulation)
Table 2 shows the composition of the raw materials. As for coke and peridotite, 9 types of blended raw materials were prepared by combining the above 3 types of different particle sizes, and tests were conducted on each of them. Iron ore having an average particle size of 1.5 mm was used.

As shown in Table 2, the ratio of return ore and coke was 15.0% by mass and 3.6% by mass, respectively, with the raw material excluding return ore and coke being 100% by mass. After mixing these blended raw materials with a universal kneader, they were granulated for a predetermined time (3 minutes) using a drum type granulator with a diameter of 1 m with a target moisture content of 7.5% by mass, followed by a pot firing test. A compounding raw material (sintering raw material) for

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

FIG. 1 is a diagram schematically showing a sieving device 1 used in this experiment. As shown in FIG. 1, this sieving device 1 includes a supply section 3 for supplying the sintering raw material 2 and slits 5 for classifying the supplied sintering raw material 2 . Below the slits 5, a plurality of collection boxes 7 (six in this embodiment) for collecting the sintering raw material 2 classified by the slits 5 are arranged side by side. The slit 5 is inclined downward from the supply section 3, extends perpendicularly to the moving direction of the raw material for sintering, and has slit bars 5a arranged at equal intervals in this 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 passes through the slit 5 and falls into the recovery box 7 in order from the smallest particle size. Thus, the sintering raw material 2 is sorted into the collection box 7 according to the particle size. Specifically, fine grains with a small grain size are collected in the collection box 7 on the upstream side of the slit 5, and coarse grains with a large grain size are collected in the collection box 7 on the downstream side. The recovered sintering raw material in the recovery box 7 was charged into a sintering pot described later in order from the coarse grain side to reproduce the same grain size segregation and raw material component segregation as the raw material packed bed of the actual sintering machine ( layer thickness 435 mm). Incidentally, the inclination angle of the slit 5 was set to 40° at which continuous segregation was obtained as a result of preliminary examination.

(Sintering pot test)
Table 3 shows the specifications and test conditions of the test equipment used for the sintering pot test. A sintering pot test simulated the sintering process of the raw material packed bed in an actual machine. The surface of the sintered layer after filling the sintering raw material was ignited, and the raw material packed layer was sintered by sucking air with a blower from an air box installed at the bottom of the sintering pot.

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

(Evaluation of product yield)
Table 4 shows the results of the product yield test of sintered ore fired from the nine types of sintering raw materials described above.
Experiments 1 to 3, Experiments 4 to 6, and Experiments 7 to 9 use fine (C1), medium (C2), and coarse (C3) coke samples, respectively. In Experiments 1, 4, 7, Experiments 2, 5, 8, and Experiments 3, 6, 9, the limestone grain sizes were fine grains (L1), medium grains (L2), and coarse grains (L3), respectively. are using. In addition, an experiment using coke with a limestone grain size slightly coarser than coarse grains (L3) and coke grains coarser than coarse grains (C3) (average particle size exceeding 3.0 mm) was also conducted. It is listed in Table 4 as Experiment 10. This average particle size is the weighted average of the medians of the particle size categories similar to those described above, using mass fractions.

In Table 4, 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 4 is an average value of the yields (+5 mm%) of the upper layer, middle layer, and lower layer samples.
Requirement 1: The average particle size of carbonaceous material (MS _C ) is more than 2.0 mm and 2.8 mm or less Requirement 2: The average particle size of limestone (MS _L ) is 0.94 of the average particle size of carbon material (MS _C ) 1.2 times or less

FIG. 2 is a diagram showing the relationship between the average coke particle size (MS _C ) and product yield. As shown in FIG. 2, the average particle size of coke (MS _C ) is more than 2.0 mm and 2.8 mm or less, and the average particle size of coke (MS _C ) and the average particle size of limestone (MS _L ) It was found that by adjusting the ratio, the yield of finished products was as high as 70% by mass or more. In particular, in Experiments 5, 6, and 9, which are examples of the present invention, it was found that a product yield of 70% by mass or more could be ensured. In addition, in Experiment 10 using coke with an average particle size (MS _C ) exceeding 2.8 mm, seizure occurred on the grate surface of the lower layer, and the ventilation in the sintering pot decreased, and the yield decreased significantly.

FIG. 3 is a diagram showing the relationship between the average particle size of coke (MS _C ) and the average particle size of limestone (MS _L ). A straight line L1 in the figure indicates a straight line with a slope of 1.2, and a straight line L2 indicates a straight line with a slope of 0.94. Experiments 5, 6, and 9, which are examples of the present invention, are located between straight lines L1 and L2. In order to ensure a high yield of products, the average particle size of coke (MS _C ) is set to more than 2.0 mm and 2.8 mm or less, and the average particle size of limestone ₍ MS _L ) should be in the range of 0.94≦MS _L /MS _C ≦1.2.

DESCRIPTION OF SYMBOLS 1... Slit bar-type mixing raw material sieving apparatus (sieving apparatus), 2... Sintering raw material, 3... Supply part, 5... Slit, 5a... Slit bar, 7... Collection box

Claims (1)

In a method for producing sintered ore, a sintering raw material mixed with iron ore, limestone, MgO-containing auxiliary raw material, carbonaceous material and return ore is granulated, charged into a pallet of a downward suction sintering machine, and fired,
The average particle diameter (MS _C ) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less,
A sintered ore characterized in that the ratio of the average particle size of the limestone (MS _L ) and the average particle size of the carbon material (MS _C ) is 0.94 ≤ MS _L /MS _C ≤ 1.2 Production method.

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