JP2020176299A - Method for manufacturing sintered ore - Google Patents

Abstract

To provide a method for manufacturing sintered ore in which an improvement in the yield of sintered ore is aimed.SOLUTION: A method for manufacturing sintered ore is a method for manufacturing sintered ore in which a sintering raw material, in which iron ore, limestone, MgO-containing auxiliary raw material, carbonaceous material and return ore are compounded, is subjected to granulation treatment, segregation-charged into the pallet of a downward suction type sintering machine, and calcined, and in which, characterized, the average particle size (MSC) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less, and the ratio of the average particle size of limestone (MSL) to the average particle size of carbonaceous material (MSC) is 0.94≤MSL/MSC≤1.2.SELECTED DRAWING: Figure 3

Description

The present invention relates to a method for producing a sinter.

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

Sintered ore is usually produced as follows. First, an auxiliary raw material, a charcoal material, and a return ore are mixed at a predetermined ratio with an iron-containing raw material powder such as iron ore, which is the main raw material, and then appropriate water is added to the mixture to granulate and blend the raw material (hereinafter referred to as “blended material”). It is also called a sintered raw material).

Next, this sintering raw material is charged into a downward suction type Dwightroid (DL) type sintering machine (hereinafter, also referred to as a sintering machine). Specifically, the sintered raw material is quantified 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 filling layer. .. The upper layer (surface layer) of the formed raw material filling layer is ignited by an ignition furnace. Then, oxygen is supplied by sucking air from the lower part of the pallet while continuously moving the pallet, and the combustion of the carbonaceous material in the raw material filling layer proceeds from the upper layer to the lower layer. The raw material filling 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 portion (sinter cake) is pulverized and sieved to a predetermined particle size, and a sinter having a certain particle size or more is used as a raw material for a blast furnace. Those having a particle size smaller than a certain size (usually −5 mm) are recovered as returned ore and reused as a part of the sintering raw material.

Here, the sintered raw material is charged onto the pallet via the inclined surface of the charging chute. Therefore, the charged sintered raw material forms a slope when placed on the pallet, and a rolling classification action occurs on this slope. Due to this rolling classification action, particle size segregation occurs in the layer thickness (layer height) direction of the raw material packing layer, and the sintered raw material has a smaller particle size on the upper layer side of the raw material packing layer and a larger particle size on the raw material packing layer. It becomes easier to charge to the lower layer side.

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 amount of heat tends to be insufficient due to the low temperature air sucked, while on the lower layer side, the amount of heat becomes excessive due to the residual heat of combustion on the upper layer side.

Due to the particle size segregation of the sintered raw material in the layer thickness direction and the difference in the amount of heat received in the layer thickness direction, the amount of the melt of iron ore, which is the main raw material, is uneven in the layer thickness direction, and the calcination is fired in the layer thickness direction. The yield and quality of sinter will differ. As a result, the yield as a whole may decrease, but in order to prevent this, a technique for controlling the distribution of the sintered raw material in the layer thickness direction and the concentration of components that influence the melting point is disclosed.

For example, the particle size of the charcoal material contained in the sinter raw material before granulation is adjusted (Patent Document 1), and the particle size of coke and limestone is adjusted (Patent Document 2) to obtain the sinter. The manufacturing technology is disclosed.

Patent Documents 1 and 2 describe a technique for producing a sinter having excellent high-temperature reduction and softening melt properties by increasing the formation of micropores by adjusting the particle size distribution of coke and limestone to be blended in the sinter raw material before firing. Is disclosed.

Japanese Unexamined Patent Publication No. 07-3342 Japanese Unexamined Patent Publication No. 08-120350

In the techniques described in Patent Document 1 and Patent Document 2 above, it is shown that the grain sizes of the carbonaceous material and the limestone are adjusted separately. However, a method for producing sinter that can improve the yield of sinter by adjusting the two raw materials, carbonaceous material and limestone, to an appropriate combination of particle sizes has not been proposed so far. ..

An object of the present invention is the production of a sinter that enables improvement in yield in a method for producing a sinter in which a compounded raw material is granulated, charged into a pallet of a downward suction type sinter, and fired. To provide a method.

The gist of the present invention is as follows.
In the method for producing sinter, which is obtained by granulating a sinter raw material containing iron ore, limestone, MgO-containing auxiliary raw material, charcoal material, and return ore, charging the sinter into a pallet of a downward suction type sinter, and firing the sinter.
The average particle size (MS _C ) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less.
The ratio of the average particle size (MS _L ) of the limestone to the average particle size (MS _C ) of the carbonaceous material is 0.94 ≤ MS _L / MS _C ≤ 1.2. Production method.

According to the present invention, by adjusting the carbonaceous material and limestone based on these particle size ratios, it is possible to control the particle size segregation of both raw materials and improve the yield.

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 (MS _C ) of coke and the product yield. It is a figure which shows the relationship between the average particle diameter (MS _C ) of coke and the average particle diameter (MS _L ) of limestone.

The process of solving the problem will be explained in detail below.

Sintered ore is made by blending iron-containing raw material powder such as iron ore, which is the main raw material, auxiliary raw materials, charcoal, and return ore. Iron ore occupies about 70% by mass or more and 85% by mass or less of the sintering raw material, and is used in a particle size range of 10 mm or less. Usually, 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 raw materials are CaO-containing auxiliary raw materials such as limestone and quicklime, and MgO-containing auxiliary raw materials such as peridotite and nickel slag. The carbonaceous material is a material mainly composed of a carbon component (free carbon) that is a heat generating source for sintering, such as coal char, in addition to coke and anthracite that are usually used.

In the sintering process, the carbonaceous material becomes a heat source for forming a melt around the iron ore in the raw material packing layer. Limestone is the raw material for the melt and melts when the carbonaceous material burns. 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 (sintered raw material). Proceeds. Therefore, in the melt formation (sintering) reaction of the sintered raw material, limestone and carbonaceous material affect the amount of melt generated, that is, the strength of the sintered ore to be calcined, and are important factors directly linked to the yield. It has become.

If the particle size of limestone is small, it is easy to melt, but if it is too small, the aeration resistance of the raw material packing layer increases when it is charged into the pallet, and the productivity is lowered. Further, when the particle size of limestone is large and remains undissolved, the amount of melt produced decreases. Due to the insufficient amount of melt produced, unsintered portions remain in the sintered cake, and as a result, the yield is lowered due to insufficient strength. Here, the particle size segregation of the sintered raw material in the layer thickness direction described above is the same for the carbonic material and limestone which are the sintered raw materials, and the coarse-grained material may be biased to the lower layer and the fine-grained material may be biased to the upper layer. Are known.

The present inventor has focused on the particle size segregation of carbonaceous material and limestone as described above, that is, the endowment amount in the layer thickness direction changes depending on the particle size. By segregating coke, which is the heat source for melt formation, and limestone, which is the raw material for the melt, in the same manner in the layer thickness direction, it is possible to prevent undissolved limestone and generate the melt required for sintering. I thought I could do it. That is, by adjusting both the particle size of the carbonaceous material (average particle size MS _C ) and the particle size of limestone (average particle size MS _L ) based on the particle size ratio, free carbon, which is a heat source for generating a melt, is used. , The segregation state of both components of CaO, which is a raw material of the melt, in the layer thickness direction can be controlled to be similar. As a result, it was considered that the amount of melt generated in the layer thickness direction could be controlled and the yield of the sinter could be improved.

Therefore, the present inventor investigated the range of an appropriate particle size ratio for the particle size of the carbonaceous material and the particle size of the limestone. Specifically, a plurality of carbon materials having different particle sizes and limestones having different particle sizes were prepared, and a sintering pot test was conducted on a sintered raw material in which these were mixed in combination to examine each yield in the sintering process. As a result, even when a charcoal material having an average 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 is used, the particle size of limestone (average particle size) Hereinafter, the ratio of the "average particle size of limestone" (also referred to as "MS _L ") to the particle size of the carbonaceous material (hereinafter, also referred to as "average particle size of the carbonaceous material" or "MS _C ") is "0.94". It was found that the effect of improving the yield of the sinter can be obtained by adjusting so that ≦ MS _L / MS _C ≦ 1.2 ”. Here, when 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 when the average particle size of the carbonaceous material is larger than 2.8 mm, the yield decreases due to insufficient heat in the lower layer of the pallet. The amount of carbonaceous material in the lower layer may become too large, causing seizure on the great surface of the pallet, making stable operation difficult. Further, if the value of "MS _L / MS _C " is less than 0.94, the particle size of the limestone is small and the gaps between the raw material particles are filled, so that the amount of melt produced is too large and the raw material filling layer Breathability deteriorates and yield decreases. If the value of "MS _L / MS _C " is larger than 1.2, the grain size of the limestone becomes large, so that the limestone becomes difficult to dissolve, the amount of melt produced decreases, unsintered parts are generated, and the yield is reduced. descend. The present application has been invented based on such findings.

In the present invention, the inventor employs the ratio of the average grain size of limestone to the average grain size of the carbonaceous material (MS _L / MS _C ) as an index for improving the yield. Although various representative indexes representing the particle size can be considered, in dealing with the phenomenon dominated by the particle size segregation at the time of charging the raw material, the average particle size described later is better than the expression using the particle size configuration adopted in Patent Documents 1 and 2. This is because (MS) was considered to be a more appropriate particle size index. Here, the particle size segregation behavior in each raw material packing layer is based on the difference in particle size with respect to the particle size of iron ore as the main raw material (hereinafter, also referred to as “average particle size of iron ore” or “MSo”), for example, the particle size ratio. It is reasonable to think that it is controlled by a certain MS _L / MSo and MS _C / MSo. Therefore, the relative segregation behavior of the carbonaceous material and the limestone is governed by (MS _L / M So) / (MS _C / M So) in detail. At this time, since MSo is offset by the denominator numerator, the index adopted in the present application: MS _L / MS _C is obtained. 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 that does not depend on the particle size of iron ore.

As an example, the rationale for determining a suitable range of the ratio of the average particle size of limestone (MS _L ) to the average particle size of carbonaceous material (MS _C ) is shown. In this embodiment, a compounding raw material filling layer is formed by a charging experimental 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 (sintering 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 limestone was used as the CaO-containing auxiliary material among the compounding raw materials. As shown in Table 1, three types of coke and limestone having 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 grain (C3)) was prepared. Table 1 shows the particle size distribution of limestone (L1, L2, L3) and coke (C1, C2, C3) samples when they were sieved using six types of sieves with different meshes (opening dimensions). Is shown. As shown in Table 1, the particle sizes that serve as the boundary values for the particle size classification are 0.25 mm, 0.5 mm, 1 mm, 3 mm, 5 mm, and 7 mm, and these values are the sieves of the sieve used for classification. .. For example, the particle size classification "1 mm-0.5 mm" is above the sieve when sieved with a sieve having a mesh size of 0.5 mm and below the sieve when sieved through a sieve having a mesh size of 1 mm. As for the 0.25 mm, 0.5 mm, and 1 mm sieves, those specified in JIS Z 8801 are used. The average particle size (MS) is an average value calculated by weighting the median value of the particle size categories by the mass fraction for each particle size category. In the calculation, it is assumed that there is no difference in specific gravity for each particle size.

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

(Ingredient formulation and granulation)
Table 2 shows the composition of raw materials. For coke and peridotite, nine types of compounding raw materials, which were compounded by combining the above three types with different particle sizes, were prepared and tested for each. The iron ore used had an average particle size of 1.5 mm.

As shown in Table 2, the raw materials excluding the returned ore and coke were taken as 100% by mass, and the blending ratios of the returned ore and coke were 15.0% by mass and 3.6% by mass, respectively. After mixing these compounding raw materials with a universal kneader, granulate for a predetermined time (3 minutes) using a drum-type granulator with a diameter of 1 m with a target of 7.5% by mass of water content, and perform a pan firing test. A compounding raw material (sintered raw material) for use was prepared.

(Classification of granulated sintered raw materials)
In order to reproduce the particle size segregation of the compounded raw material filling layer in the layer thickness direction that occurs when the compounded raw material is charged into the pallet, a slit bar type compounded raw material sieving device (hereinafter, also referred to as a sieving device) is used to granulate and bake. The raw materials were classified.

FIG. 1 is a diagram schematically showing a sieving device 1 used in this experiment. As shown in FIG. 1, the sieving apparatus 1 includes a supply unit 3 for supplying the sintered raw material 2 and a slit 5 for classifying the supplied sintered raw material 2. Below the slit 5, a plurality of recovery boxes 7 (6 in this embodiment) for collecting the sintered raw material 2 classified by the slit 5 are arranged side by side. The slits 5 have slit bars 5a that are arranged so as to be inclined downward from the supply unit 3, extend orthogonally to the moving direction of the sintered raw material, and are arranged at equal intervals in the moving direction. As shown in FIG. 1, the supplied sintered raw material 2 moves on the slit bar 5a from the upstream side (upper left in the figure) to the downstream side (lower right in the figure). During this movement, the sintered raw material 2 sequentially passes through the slit 5 and falls into the recovery box 7 from the one having the smallest particle size (particle size). In this way, the sintered 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 collection box 7 on the upstream side of the slit 5, and coarse particles having a large particle size are collected in the collection box 7 on the downstream side. The sintered raw material in the recovered recovery box 7 was charged into a sintering pot to be described later in order from the coarse grain side, and the same particle size segregation and raw material component segregation as the raw material packing layer of the actual sintering machine were reproduced ( Layer thickness 435 mm). The inclination angle of the slit 5 was set to 40 °, at which continuous segregation was obtained as a result of preliminary examination.

(Sintered pot test)
Table 3 shows the specifications and test conditions of the test equipment used in the sintering pot test. The firing process of the raw material packing layer in the actual machine was simulated by the sintering pot test. The surface of the sintered layer after the filling of the sintered raw material was ignited, air was sucked from the air box installed at the bottom of the sintering pot with a blower, and the raw material packed layer was fired.

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

(Evaluation of product yield)
Table 4 shows the results of the product yield test of the sinter obtained by firing from the above-mentioned nine kinds of sinter raw materials.
In Experiments 1 to 3, Experiments 4 to 6, and Experiments 7 to 9, samples of fine-grained (C1), medium-grained (C2), and coarse-grained (C3) coke particles are used. Further, in Experiments 1, 4, 7, Experiments 2, 5, 8, and Experiments 3, 6, 9, the limestone particles were fine-grained (L1), medium-grained (L2), and coarse-grained (L3), respectively. Is using. An experiment using coke having a grain size of limestone slightly coarser than that of coarse grain (L3) and a grain size of coke having a grain size of coarse grain (over 3.0 mm) than that of coarse grain (C3) was also conducted. It is shown in Table 4 as Experiment 10. The average particle size is a weighted average of the median value of the particle size classification as described above by mass fraction.

In Table 4, those satisfying the following requirements 1 and 2 are examples, and the others are comparative examples. The product yield in Table 4 is a value obtained by averaging the yields (+ 5 mm%) of each sample in the upper layer portion, the middle layer portion, and the lower layer portion.
Requirement 1: Average grain size of carbonaceous material (MS _C ) exceeds 2.0 mm and 2.8 mm or less Requirement 2: Average particle size of limestone (MS _L ) is 0.94 of average particle size of carbonaceous material (MS _C ) More than double 1.2 times or less

FIG. 2 is a diagram showing the relationship between the average particle size of coke (MS _C ) and the 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 ) are It was found that by adjusting the ratio, the product yield became a high 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 a product yield of 70% by mass or more can be secured. Further, in Experiment 10 using coke having an average particle size (MS _C ) of more than 2.8 mm, seizure occurred on the great surface of the lower layer, the air permeability in the sintering pot decreased, and the yield was reduced. The decrease was remarkable.

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 straight line L1 in the figure shows a straight line having a slope of 1.2, and the straight line L2 shows a straight line having a slope of 0.94. 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 ensure a high yield of the product, the average grain size of coke (MS _C ) should be more than 2.0 mm and 2.8 mm or less, and the average grain size of limestone (MS _L ) with respect to the average grain size of coke (MS _C ). It was confirmed that the ratio of) should be in the range of 0.94 ≤ MS _L / MS _C ≤ 1.2.

1 ... Slit bar type compound raw material sieving device (sieving device), 2 ... Sintered raw material, 3 ... Supply unit, 5 ... Slit, 5a ... Slit bar, 7 ... Recovery box

Claims (1)

In the method for producing sinter, which is obtained by granulating a sinter raw material containing iron ore, limestone, MgO-containing auxiliary raw material, charcoal material, and return ore, charging the sinter into a pallet of a downward suction type sinter, and firing the sinter.
The average particle size (MS _C ) of the carbonaceous material is more than 2.0 mm and 2.8 mm or less.
The ratio of the average particle size (MS _L ) of the limestone to the average particle size (MS _C ) of the carbonaceous material is 0.94 ≤ MS _L / MS _C ≤ 1.2. Production method.

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