JP7339516B2 - Method for producing sintered ore - Google Patents

Description

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

At present, the main raw material for blast furnace ironmaking is sintered ore. Sintered ore is usually manufactured as follows. First, iron ore (powder) as a raw material, iron-containing miscellaneous raw materials such as steelmaking dust, MgO-containing auxiliary raw materials such as peridotite, CaO-containing auxiliary raw materials such as limestone, return ore, and sintered ore are sintered (coagulated) by combustion heat. ) is mixed with a carbonaceous material (also referred to as a coagulant), which is used as a fuel for the sintering process, at a predetermined ratio. Appropriate moisture is added to the mixed compounded raw material and granulated to obtain raw material granules.

Next, this raw material granule 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 raw material granules is cut out from a hopper immediately above the sintering machine by a raw material cutting device, and mounted on a pallet via a charging chute to form a raw material packed bed. The carbonaceous material in the raw material packed bed is ignited from the upper portion (surface layer) of the raw material packed bed formed by an ignition furnace. Then, air is sucked from below the pallet while continuously moving the pallet. Oxygen is supplied by suction, and the combustion of the carbon material in the raw material packed bed proceeds from the upper layer to the lower layer, and the raw material packed bed is sequentially sintered by the combustion heat of the carbon material. The sintered part (sinter cake) obtained by sintering is pulverized to a predetermined particle size, sieved, etc., and particles having a certain particle size or more become sintered ore, which is a raw material for blast furnaces.

Here, the raw material granules are loaded onto the pallet by charging through the inclined surface of the charging chute. The charged raw material granules themselves also form slopes when placed on the pallet. Classification occurs during downhill descent on these slopes. Due to this rolling classification action, grain size segregation occurs in the layer thickness (layer height) direction of the raw material packed bed. A large one is likely to be charged to the lower layer side of the raw material packed bed.

In sintering by a downward suction type DL type sintering machine, the upper layer (surface layer) of the raw material packed layer is ignited and sequentially sintered from the upper layer to the lower layer. Since air is sucked from below, the amount of heat received by the raw material for sintering varies depending on the layer thickness direction. On the upper layer side, low-temperature air is sucked, so the amount of heat tends to be insufficient. Therefore, generally, in the sintering process, even if the lower layer portion of the raw material packed layer has a sufficient amount of heat, the upper layer portion has an insufficient amount of heat.

Due to the grain size segregation of the raw material for sintering in the layer thickness direction and the difference in the amount of heat in the layer thickness direction, the amount of iron ore melt, which is the main raw material, is uneven in the layer thickness direction. The yield and quality of the sintered ore produced are different. As a result, the yield as a whole may be lowered. Techniques for controlling the distribution of sintering raw materials in the layer thickness direction have been disclosed in order to prevent a decrease in yield.

For example, the following charging method and charging apparatus are disclosed, which are capable of segregating a large amount of carbonaceous material, which is a fuel, to the upper layer where the amount of heat is insufficient. A method of stochastically classifying and charging sintering raw materials by arranging a large number of rod-shaped members in the raw material flow direction (Patent Document 1: Grain-regulating dispersion type charging device), sintering raw materials on advancing pallets A device for dispersing powdered fuel through a dispersing plate provided on the upper surface in a direction transverse to the direction of movement (Patent Document 2: Two-stage charging device (slip skip conveyor)), a charging chute A charging device (Patent Document 3: wind segregation type charging device) in which a gas blowing nozzle is provided above the provided opening and fine coke is classified by gas (Patent Document 3: wind segregation type charging device). There is a method of stochastically classifying and charging raw materials for sintering through a chute formed by a method (Patent Document 4: slit bar type charging device).

There is also disclosure of a charging method according to the composition of iron ore. The distribution of iron ore in the layer thickness direction varies greatly depending on the type of iron ore. In particular, pisolitic ore, which contains a large amount of water of crystallization that causes an endothermic reaction, is coarser than other ores and tends to segregate more in the lower layer. A method for producing sintered ore using a raw material defined as high crystal water ore or pisolitic ore is disclosed below. The pisolitic ore is a rock having a bean-like form in the mineralogical classification.
In Patent Document 5, when producing sintered ore using iron ore with a high content of water of crystallization, instead of segregating a large amount of carbonaceous material in the upper layer as in the past (see paragraph 0008), sintered ore raw materials It is suggested that the amount of free carbon in the vertical direction of the filling layer should be uniform. Further, in Patent Document 6, when the pisolite ore blending amount X is 10% by mass ≤ X < 30% by mass, the coke segregation degree Y (= (top layer carbon mass% - bottom layer carbon mass%) / A method for producing sintered ore is disclosed in which the average carbon mass %) is charged so that -0.1 ≤ Y ≤ 0.25 - (0.005 x X). In Patent Document 7, when the mixing ratio of high-crystalline-water iron ore in the iron ore is 10 to 50% by mass, the coke content Cmiddle of the middle layer and the coke content Cbottom of the lower layer are 0≦( Cmiddle-Cbottom)≦0.15 (mass%) is disclosed.

JP-A-61-223136 JP-A-2000-178661 JP-A-11-351756 JP-A-57-164940 JP-A-08-81717 JP 2007-169774 A JP 2009-197264 A

As shown in Patent Documents 1 to 3, it was necessary to segregate a large amount of fuel carbonaceous material in the upper layer, which generally has an insufficient amount of heat.

In recent years, due to depletion of high-quality iron ore, a large amount of high-crystalline water iron ore has been used. Conventionally, it was believed that a large amount of fuel carbon material should be segregated in the upper layer where the amount of heat is insufficient. It is suggested that the degree of segregation of the material is preferred. However, until now, there has been no knowledge about the case where high crystal water iron ore is blended at a ratio exceeding 50% by mass with respect to the raw material iron ore. The inventor focused on pisolite-based ore, which is one of high-crystalline-water iron ores, and conducted repeated research. It was found that the concentration of water of crystallization in the lower layer increased significantly, and the yield in the lower layer decreased significantly due to insufficient heat.

An object of the present invention is to enable a high yield in a method for producing sintered ore using a mixed raw material in which the mixed ratio of pisolitic ore exceeds 50% by mass with respect to the total iron ore in the raw material for sintering. It is to provide a method for producing sintered ore to be used.

The gist of the present invention is as follows.
(1) In a method for producing sintered ore, the sintered ore is produced by blending pisolitic iron ore at a ratio exceeding 50% by mass with respect to the total iron ore in the raw material for sintering,
The raw material for sintering is charged into the sintering machine so that the blending ratio (Wp) of the pisolitic iron ore with respect to the total iron ore and the degree of coke segregation (dC) satisfy the following relationship: A method for producing sintered ore characterized by:
dC=−0.02・Wp+2.0±0.2
Wp (% by mass): ratio of pisolitic iron ore to total iron ore composition
dC (mass%): degree of coke segregation where,
Coke segregation degree (dC) =
(Average value of coke concentration in the upper layer for 30% of the total layer thickness)-
(Average value of coke concentration in the lower layer for 70% of the total layer thickness)
(2) The adjustment of the coke segregation degree (dC) when changing the blending ratio (Wp) of the pisolitic iron ore is by adjusting the particle size of coke. Production method.
(3) When using a slit bar type charging device that classifies with a slit bar when charging the raw material for sintering,
The adjustment of the degree of coke segregation (dC) when the blending ratio (Wp) of the pisolitic iron ore is changed is by adjusting the interval of the slit bars. (1) or (2). A method for producing sintered ore.
(4) When using a wind force segregation type charging device that classifies by blowing gas when charging the raw material for sintering,
Any one of (1) to (3), wherein the adjustment of the degree of coke segregation (dC) when the mixing ratio (Wp) of the pisolitic iron ore is changed is by adjusting the air volume of the blown gas. 1. Manufacturing method of sintered ore according to one.

According to the present invention, even if the pisolitic ore in the raw material for sintering has a high blending ratio exceeding 50% by mass with respect to the total iron ore, by maintaining appropriate carbon material segregation conditions, high yield and can do.

It is a figure explaining coke segregation degree dC. FIG. 2 is a diagram schematically showing a sieving device (a sieving device simulating a slit bar type charging device) used in this experiment. FIG. 3 is a diagram showing the relationship between the mixing ratio Wp of pisolitic iron ore and the degree of coke segregation dC.

The details of how the problem was solved are described below.
Pisolite iron ore has two characteristics of coarser grain size and remarkably high content of water of crystallization compared to other ores. Because of its coarse grain size, when sintering raw materials containing pisolitic iron ore are charged onto a pallet, most of the pisolitic iron ore is mixed in the lower layer side of the raw material packed bed and segregates in the layer thickness direction. In particular, when the blending ratio of pisolitic iron ore exceeds 50% by mass with respect to the total iron ore in the raw material for sintering, the segregation of pisolitic iron ore to the lower layer causes crystals in the lower layer of the raw material packed layer. The water concentration will rise greatly.

In addition, when the blending ratio of pisolitic iron ore exceeds 50% by mass with respect to the total iron ore in the raw material for sintering, the large amount of pisolitic iron ore blending also affects coke segregation. . A raw material for sintering is cut out from a drum feeder (raw material cutting device) and charged onto a pallet through an inclined surface of a charging chute. In addition, the sintering raw material charged onto the pallet also forms a slope on the pallet. The raw material for sintering slides down these slopes, and the sliding distance is about 4m. Coarse particles (mainly 3 mm or more) of pisolitic iron ore have a higher specific gravity than coke of the same particle size. Therefore, the coarse particles of pitolitic iron ore are filled into the bottom of the pallet prior to coke when they are charged into the pallet. The filling of the coke to the pallet bottom is relatively hindered, and the coke concentration in the lower layer of the raw material packed layer is lower than in the case of normal raw material blending.

Here, in normal raw material blending, more coke is segregated in the upper layer than in the lower layer of the raw material packed bed in order to compensate for the heat quantity in the upper layer, which is insufficient due to the downward suction of the atmosphere. On the other hand, in the case of raw material blending in which the amount of pisolite iron ore in the raw material for sintering is increased, if coke is segregated in the upper layer, the yield in the lower layer is significantly reduced. noticed. In particular, when the amount of pisolitic iron ore blended exceeds 50% by mass with respect to the total iron ore in the raw material for sintering, as described above, the concentration of water of crystallization in the lower layer of the raw material packed layer increases. In addition to the large increase, the coke concentration of the fuel drops excessively. As a result, in the sintering process, the fuel is scarce and the dehydration reaction (endothermic reaction) of the water of crystallization occurs in the lower layer, resulting in an insufficient amount of heat, and the yield of the lower layer is remarkably reduced.

The inventor thought that by alleviating the degree of coke segregation in the upper layer and distributing more coke in the lower layer than before, the yield in the lower layer would be improved and the overall yield would be improved. . Therefore, an appropriate relationship between the blending amount of pisolitic iron ore and the segregation degree of coke when the blending amount of pisolitic iron ore exceeds 50% by mass with respect to the total iron ore in the raw material for sintering was investigated. Ta. As a result, it was found that segregating coke so as to satisfy the following conditions improved the overall yield.

(Proportion of pitolitic iron ore and degree of segregation of coke)
When the blending amount of pisolite iron ore exceeds 50% by mass with respect to the total iron ore in the raw material for sintering, the segregation degree of coke in the raw material packed bed satisfies the following conditional expression (1) do.
dC=−0.02·Wp+2.0±0.2 (1)
Wp (% by mass): Blending ratio of pisolitic iron ore to total iron ore dC (% by mass): Degree of coke segregation

Here, the coke segregation degree dC in Equation (1) is a parameter representing the degree of coke segregation, and is defined by Equation (2).
Coke segregation degree (dC) =
(Average value of coke concentration in the upper layer for 30% of the total layer thickness)-
(Average value of coke concentration in the lower layer portion for 70% of the total layer thickness) (2)
FIG. 1 is a diagram for explaining coke segregation degree dC.
FIG. 1 is a diagram showing the concentration distribution of coke (free carbon) in the layer thickness direction of a raw material packed bed formed under certain conditions. The white circles in the figure indicate measured values of the free carbon concentration in different layer thickness directions. The black circles in the figure show the average value of the free carbon concentration (three measured values) in the upper layer for 30% of the total layer thickness, and the black squares in the figure show the lower layer for 70% of the total thickness. The average value of free carbon concentration (seven measured values) is shown. In the present invention, the average value of the free carbon concentration in the lower layer portion of 70% of the total layer thickness (black square) is subtracted from the average value of the free carbon concentration of the upper layer portion of 30% of the total layer thickness (black circle). The value was defined as coke segregation degree dC. When the segregation of coke is loosened, the value of coke segregation degree dC decreases, and when the segregation of coke is strengthened, the value of coke segregation degree dC increases.
Here, the reason why the upper layer is 30% of the total layer thickness is that when the strength distribution of the sinter cake is measured in the layer height direction, the strength is generally high from the lower surface (100% position) to the 30% position without any change in strength. On the other hand, this is because the strength sharply decreases from the 30% position toward the upper surface (0% position). The reason why the degree of coke segregation is defined by the formula (2) is that the coke concentration of the upper layer is specified by sampling the raw material of 30% of the upper layer and measuring the free carbon concentration, while the coke concentration of the lower layer is This is because the degree of coke segregation can be easily evaluated because it can be estimated from the known overall coke concentration.

Moreover, the blending ratio Wp in the formula (1) indicates the blending ratio of the pisolite iron ore to the total iron ore blend. The coefficient of Wp is "-0.02", and there is a relationship that coke segregation is relaxed as the ratio of pisolitic iron ore to the total iron ore mixture increases. The coke segregation degree dC is derived by substituting the blending ratio Wp of the pisolitic iron ore with respect to the total iron ore of the raw material for sintering (hereinafter referred to as the pisolitic iron ore blending ratio Wp as appropriate) into the formula (1). can be done. The absolute value of the coefficient of Wp is a large value compared to the case where the blending ratio of pisolitic iron ore to the total iron ore blend is 50% or less, and the blending ratio of pisolitic iron ore is less than 50%. If it exceeds, it indicates that the heat quantity in the lower layer is insufficient than expected.

(Method for adjusting coke segregation degree dC)
The apparatus and method for segregating coke are not particularly limited as long as they can achieve the desired coke segregation (dC). For example, a desired coke segregation degree dC can be achieved by adjusting the particle size of coke used as a raw material for sintering or by adjusting charging conditions in a segregation charging device. Examples of segregation charging devices include a rectifying distributed charging device (Patent Document 1), a two-stage charging device (Patent Document 2), a wind segregation charging device (Patent Document 3), and a slit bar charging device ( Patent document 4) etc. are mentioned.

As an example of a means for realizing a desired coke segregation degree dC, when using a slit bar charging device (Patent Document 4), a method for adjusting the particle size of coke and a method for adjusting charging conditions are described below. will be described in order.

First, a method for realizing a desired degree of coke segregation dC by adjusting the particle size of coke will be described. Coke for sintering is usually obtained by pulverizing blast furnace coke under sieves (less than 40 mm). Coke particle size control can be performed during grinding.
In general, increasing the coke particle size decreases the coke segregation degree (dC). This is because if the particle size of coke is increased, the difference in particle size between iron ore and coke is reduced, and the segregation effect during pallet charging due to the difference in particle size is reduced.
An example of the relationship between the coke segregation degree (dC) and the coke particle size (MS: arithmetic mean size) is shown in Equation (3). The particle size (MS) of coke is obtained by Equation (3), and the particle size (MS) of coke used as a raw material for sintering is adjusted based on the obtained particle size (MS) to achieve the desired coke segregation ( dC).
dC = -0.71 x (coke particle size MS) + 2.28 (3)
MS: arithmetic mean diameter (mm)
Here, the arithmetic mean diameter is the median value of the particle size classification from the particle size distribution when sieving using sieves with different meshes (mesh opening dimensions), weighted by the mass fraction for each particle size classification. It is the calculated average value.

Next, a method for realizing a desired degree of coke segregation dC by adjusting charging conditions will be described.
A slit bar is a sieve consisting of bars equally spaced in the horizontal direction (perpendicular to the direction of material descent). When the raw material flows down on this, it is stochastically classified, and relatively fine raw material particles fall under the sieve to form the upper layer of the raw material packed layer. The charging conditions of the slit bar type charging device can be adjusted so that the coke segregation degree dC becomes a predetermined value by adjusting the slit width (slit bar interval) and charging chute angle. As an example when the charging chute angle is 40 degrees and the coke particle size (MS) is 1.8 mm, the gap between the slit bars is adjusted according to the following formula (4) to obtain the desired coke segregation (dC) and It is possible to For example, for a coke segregation (dC) of 1.0, the bar spacing is 12.5 mm.
dC=−0.2×L+3.5 (4)
L (mm): Bar spacing

As described above, a slit bar type charging device (segregation charging device) can be used to achieve the desired degree of coke segregation dC. The coke particle size adjustment method and charging condition adjustment method using the slit bar type charging device shown here is an example of using a general slit bar type charging device, and the slit bar type Depending on the charging device, it is necessary to check the relationship between the grain size, charging conditions, and the degree of segregation in advance, and then make adjustments. Alternatively, a method of adjusting the particle size of coke and adjusting charging conditions may be used. A desired coke segregation degree dC can be achieved by previously examining the relationship between coke particle size, charging conditions, and coke segregation degree dC.

Also, with other segregation charging devices, the desired coke segregation degree dC can be achieved by adjusting the particle size of coke and adjusting the charging conditions, as in the case of the slit bar type charging device. Although the details will be described later, in the two-stage charging device (Patent Document 2), the blending ratio of the raw materials in the upper and lower stages is adjusted, and in the wind segregation type charging device (Patent Document 3), the air volume is adjusted to achieve the desired value. A coke segregation degree dC can be realized.

As an example, a conditional expression ( Show the grounds for determining 1). In this embodiment, a raw material packed layer is formed using a segregation charging device, and the formed raw material packed layer is fired in a general sintering experimental device (sintering pot test), thereby making an actual sintering machine. A reproducible method was used. As the segregation charging device, a slit bar type sieving device was used, which can relatively easily reproduce the charging state of the compounded raw materials such as component segregation and particle size segregation.

(Mixing ratio of raw materials for sintering)
The contents of the experiment conducted by the inventor are as follows.
First, in this experiment, experiments were conducted on nine types of mixed raw materials with different pisolitic iron ore mixing ratios Wp and coke segregation degrees dC. Specifically, as shown in Table 2, the pisolitic iron ore blending ratio Wp is 50.9% (Experimental Examples 1 to 3), 70.3% (Experimental Examples 4 to 6), 90.9% (Experimental Three experiments (a total of nine experiments) were conducted with different conditions for the degree of coke segregation dC for each of the three types different from Examples 7 to 9). At this time, in all the experiments, the average coke concentration and coke particle size in all blended raw materials were kept constant. The coke particle size was adjusted to that used in a general sintered ore manufacturing process. Table 1 shows the particle size distribution and average particle size of coke used in this experiment.

(Mixing and granulation of raw materials for sintering)
Table 2 shows the mixing ratio of the raw materials for sintering used.
As shown in Table 2, the ratio of the return ores and the coke was set to 15.0% by mass and 4.8% by mass, respectively, with the raw material excluding the return ores and coke being 100% by mass. These raw materials were mixed (dry mixed) by a drum mixer at 32 rpm for 1 minute. After mixing, 7.0% by mass of water was added to the blended raw materials, and the mixture was granulated for 3 minutes to produce raw material granules (hereinafter, appropriately referred to as whole raw material granules). In addition, raw material granules (hereinafter referred to as C-free raw material granules as appropriate) were produced by similarly mixing and granulating raw materials shown in Table 3 from which coke was removed.

(Sieving of raw material granules)
A slit bar type sieving device was used to reproduce the grain size segregation in the layer thickness direction of the mixed raw material packed bed that occurs when the raw material is charged into the pallet. This slit bar type sieving device can imitate the charging in the above slit bar type charging device (Patent Document 4).

FIG. 1 is a diagram schematically showing a slit bar type sieving apparatus 1, which is a mixed raw material sieving apparatus used in this experiment.
As shown in FIG. 1, this slit bar type sieving apparatus 1 includes a supply unit 3 for supplying the raw material 2 for sintering, and a slit 5 for classifying the supplied raw material 2 for sintering. ing.

Below the slits 5, a plurality of collection boxes 7 (six in this embodiment) for collecting the raw materials 2 for sintering classified by the slits 5 are arranged side by side. The slit 5 has a plurality of slit bars 5a. The slit bars 5a are inclined downward from the supply section 3, extend perpendicularly to the moving direction of the raw material for sintering, and are arranged at equal intervals in this moving direction. As shown in FIG. 1, the supplied raw material 2 for sintering 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 raw materials 2 for sintering pass through the slits 5 and drop into the recovery box 7 in ascending order of particle size (particle size). Thus, the sintering raw material 2 is sorted into the recovery 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.

Using the slit bar type sieving apparatus 1 shown in FIG. 1, the above-mentioned whole raw material granules and C-free raw material granules were each sieved. Table 3 shows the specifications and sieving conditions of the slit bar type sieving device 1. The inclination angle of the slit 5 was set to 40°, which obtained continuous segregation as a result of preliminary examination.

(Adjustment of coke segregation degree dC of sieved raw material granules)
The carbon concentration in each collection box 7 of the sieved all raw material granules is measured, and as appropriate, coke powder is added to the sintering raw material for the upper layer, and C is added to the sintering raw material for the lower layer. The raw material granules were added to adjust the coke segregation degree dC to a predetermined value when charged. Each raw material granule adjusted for each collection box 7 is charged into a sintering pot described later in order from the coarse grain side (layer thickness 435 mm), and the same grain size segregation as the raw material packed bed of the actual sintering machine, raw material The component segregation was reproduced.

(Sintering pot test)
Table 4 shows the specifications and experimental conditions of the experimental apparatus 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 packed bed after filling the raw material granules was ignited, and the raw material packed bed 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 sinter cake after baking is subjected to a falling weight test (a weight of 4 kg is dropped from a height of 2 m onto the sample four times repeatedly), and then passed through a sieve with an opening of 5 mm. The mass % of the particles) with respect to the total mass of the sinter cake was defined as the product yield (+5 mm %) here.

(Experimental result)
At the bottom of Table 2, the results of product yield tests for Experiments 1-9 are shown. In Table 2, among the experiments conducted with the same pisolitic iron ore blending ratio Wp, the ones with the highest yield are Inventive Examples 1 to 3, and the others are Comparative Examples 1 to 6.
When the pitolitic iron ore blending ratio Wp was 50.9% and the degree of coke segregation dC was 0.6%, the segregation was insufficient, and the yield was as low as 79% (Comparative Example 1). When the coke segregation degree dC was segregated to 0.9%, the yield increased to 83% (Invention 1). However, when the coke segregation degree dC was further strengthened to 1.3%, the heat shortage in the lower layer was caused and the yield decreased to 79% (Comparative Example 2).
When the pitolitic iron ore blending ratio Wp was 70.3% and the degree of coke segregation dC was 0.3%, the segregation was insufficient and the yield was as low as 78% (Comparative Example 3). When the coke segregation degree dC was segregated to 0.6%, the yield increased to 79% (Invention 2). However, when the coke segregation degree dC was further strengthened to 0.9%, the heat shortage in the lower layer was caused and the yield decreased to 75% (Comparative Example 4).
When the coke segregation degree dC was -0.2% under the condition that the pisolitic iron ore blending ratio Wp was 90.9%, the segregation was insufficient, and the yield was as low as 70% (Comparative Example 5). . When the coke segregation degree dC was segregated to 0.2%, the yield increased to 75% (Invention 3). However, when the coke segregation degree dC was further strengthened to 0.5%, the heat shortage in the lower layer was caused and the yield decreased to 70% (Comparative Example 6).

FIG. 3 is a diagram showing the relationship between the pitolitic iron ore blending ratio Wp and the degree of coke segregation dC. Black triangles plotted in FIG. 3 indicate Inventions 1 to 3, respectively, and black circles indicate Comparative Examples 1 to 6, respectively. The range that satisfies the conditional expression (1) “dC=−0.02・Wp+2.0±0.2” is the top line of the three downward-sloping diagonal lines on the right side of FIG. It is the area sandwiched between the bottom lines. Under high blending conditions where the pisolitic iron ore blending ratio Wp exceeds 50%, "dC = -0.02 · Wp + 2.0 ± 0.2" is shown in order to ensure a high yield of the product. It was confirmed that conditional expression (1) must be satisfied.

In the above-described embodiment, the slit bar type sieving device 1 that imitates charging with a slit bar type charging device (Patent Document 4) is used so that coke segregation reaches a predetermined coke segregation degree dC. However, as mentioned above, other segregation charging devices may be used. Hereinafter, the case of using another segregation charging device will be described as a modification.

(Modification 1: Wind segregation type charging equipment)
The wind segregation type charging device (Nakamura et al.: Tetsu to Hagane, 1987-S845) is a device that performs segregation charging by wind classification in which gas is blown onto the raw material granules sliding down the inclined surface of a charging chute. The degree of coke segregation dC can be adjusted to a predetermined value by adjusting the air volume of the wind classifier. For example, for the wind segregation type charging equipment to be used, the relationship between the air volume and the coke segregation degree dC is obtained, and based on this relationship, the air volume is adjusted to adjust the coke segregation degree dC to a predetermined value.
For example, when the coke particle size MS is 1.8 mm, the degree of coke segregation dC and the air volume V for air volume classification are expressed by the following equation (5). It was confirmed that the air volume can be adjusted according to equation (5). For example, in order to set the degree of coke segregation dC to "1.0", the air volume V is approximately 240 m ³ /min.
dC=+0.008×V−0.9
V (m ³ /min): Blowing air volume

(Modification 2: Slit type wind power segregation charging device)
The slit type wind segregation charging device (Patent Document 3 (see Fig. 1)) is a wind segregation charging device that performs segregation charging by wind classification, and the charging chute has a slit ( opening) is provided. The first gas blowing device blows gas toward the sintering raw material sliding down the slit to drop the fine/fine-grained sintering raw material downward from the opening, and the second gas blowing device Then, a gas is blown onto the dropped raw material for sintering to separate fine grains and fine grains, followed by classification. The degree of coke segregation dC can be adjusted to a predetermined value by adjusting the air volumes of the first gas blowing device and the second gas blowing device.

(Modification 3: Two-stage charging device)
The two-stage charging device is a device in which a slip stick conveyor (Patent Document 2) having a supply means (hopper) and a dispersing plate is provided in two stages, one for the upper layer and the other for the lower layer. The coke segregation degree dC can be adjusted by separately preparing raw materials for the upper layer and for the lower layer, each of which has a desired coke concentration, and charging them onto a pallet.

Although the preferred embodiments of the present invention have been described in detail above, according to each of the above-described embodiments, even if a blended raw material in which the blending ratio of pisolite-based ore in the raw iron ore exceeds 50% by mass, a predetermined It was possible to adjust the degree of coke segregation dC and achieve a high yield. In addition, this invention is not limited to embodiment mentioned above. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive of various modifications or modifications within the scope of the technical idea described in the claims. It is understood that these also naturally belong to the technical scope of the present invention.

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

Claims (4)

In a method for producing sintered ore, the sintered ore is produced by blending pisolitic iron ore at a ratio exceeding 50% by mass with respect to the total iron ore in the raw material for sintering,
The raw material for sintering is used in a Dwightroid (DL) sintering machine so that the blending ratio (Wp) of the pisolitic iron ore with respect to the total iron ore and the degree of coke segregation (dC) satisfy the following relationship. A method for producing sintered ore, characterized by charging into.
dC=−0.02・Wp+2.0±0.2
Wp (% by mass): ratio of pisolitic iron ore to total iron ore composition
dC (mass%): degree of coke segregation where,
Coke segregation degree (dC) =
(Average value of coke concentration in the upper layer for 30% of the total layer thickness)-
(Average value of coke concentration in the lower layer for 70% of the total layer thickness) The method for producing sintered ore according to claim 1, wherein the adjustment of the degree of coke segregation (dC) when the blending ratio (Wp) of the pisolitic iron ore is changed is by adjusting the particle size of coke. When using a slit bar type charging device that classifies with a slit bar when charging the raw material for sintering,
3. The adjustment of the degree of coke segregation (dC) when changing the blending ratio (Wp) of the pisolitic iron ore is according to the adjustment of the interval between the slit bars. A method for producing sintered ore. When using a wind force segregation type charging device that classifies by blowing gas when charging the raw material for sintering,
4. The adjustment of the degree of coke segregation (dC) when changing the mixing ratio (Wp) of the pisolitic iron ore is performed by adjusting the air volume of the gas to be blown. A method for producing a sintered ore according to item 1.

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