JP2021165417A - Method for producing non-fired carbon-containing agglomerate for blast furnace - Google Patents

Abstract

To provide a technique producing non-fired carbon-containing agglomerates for a blast furnace capable of attaining high strength without deteriorating the hot strength thereof even if T.C. is high and the blending ratio of a hydraulic binder is low.SOLUTION: A method has a process where water at a prescribed ratio is added to non-fired carbon-containing agglomerate raw materials subjected to prescribed blending, they are continuously mixed into mixed raw materials, the same is transferred in such a manner that the filling ratio of a first extrusion part 3 is controlled to 50 to 90 vol% and the filling ratio of a second extrusion part 5 is controlled to 50 to 95 vol%, and the mixed raw materials are continuously extruded into a molded body to produce non-fired carbon-containing agglomerates for a blast furnace. Raw materials in which the particle size of the mixed raw materials is in-iron-containing raw materials-10 μm powder ratio≥15.0 mass% are used, the mixed raw materials are continuously extruded while forming a first material seal and a second material seal in such a manner that the respective filling ratios are controlled to 50 to 90 mass% in accordance with the mixed raw materials in the first extrusion part and the second extrusion part, and the molding is performed under the vacuum deaeration conditions of -40 kPaG or lower.SELECTED DRAWING: Figure 1

Description

The present invention relates to a technique for producing a non-firing coal-containing agglomerate ore for a blast furnace, which is used as a raw material for a steelmaking furnace such as a blast furnace or a rigid melting furnace.

In the blast furnace, raw material ore and massive coke are injected from the upper part of the furnace and blown from the lower part of the furnace, and the reducing gas generated from the bulky coke and blown air is ventilated from the lower part of the furnace to the upper part of the furnace to release iron oxide in the raw material ore. It is reduced and dissolved. In order to ensure the ventilation of the reducing gas in the furnace, the raw material ore is required to have strength that does not pulverize in the furnace. For this reason, in a blast furnace, raw materials that have been fired at a high temperature in advance, such as sinter and calcined pellets, are usually used.

On the other hand, non-calcination coal-containing agglomerates for blast furnaces have been developed that suppress the energy consumption required for calcination by using a water-hard binder such as cement and suppress the amount of carbon dioxide gas, which is a greenhouse gas. .. As a raw material for this uncalcined coal-containing lump ore for a blast furnace, there is a possibility that inferior powder ore, which has low sinterability and is difficult to be molded into a lump, can also be used.

In addition, for non-firing coal-containing agglomerates for blast furnaces, powdered coke, which has a small particle size and is difficult to directly charge into a blast furnace, and anthracite coal, which is inexpensive but has low cohesiveness and is difficult to coke, are also used as reducing agents. There is a possibility that it can be mixed, and it is expected that the ratio of reducing agents in the blast furnace can be reduced. According to the latest findings, the carbon content (TC) contained in the uncalcined coal-containing agglomerate for blast furnace is 120 to 200 of the theoretical carbon content required to reduce iron oxide to metallic iron. It has been clarified that the effect of reducing the ratio of the reducing material in the blast furnace is maximized by setting it to% (corresponding to 15 to 25% by mass in terms of TC) (Patent Document 1).

The hydrate in the uncalcined coal-containing agglomerate for blast furnace formed by the curing reaction of the hydraulic binder is decomposed by the endothermic reaction when heated to about 400 ° C. or higher in the blast furnace. For this reason, the strength of the uncalcined coal-containing agglomerate for blast furnace is significantly reduced in the furnace, and there is a concern that it will be pulverized. When the non-calcined coal-containing agglomerate for blast furnace is pulverized in the blast furnace, the air permeability in the furnace is deteriorated. Therefore, the non-calcined coal-containing agglomerate for blast furnace is required to have a certain hot strength. On the other hand, if a large amount of water-hard binder is used to secure the hot strength, the amount of reducing agent input to the blast furnace increases in order to compensate for the heat taken by the endothermic reaction, and the hot metal cost increases.

From the above, in the method for producing a non-calcined coal-containing agglomerate for a blast furnace, a production method capable of exhibiting the hot strength required for the use of a blast furnace with as little hydraulic binder as possible is required.

The pulverization of non-fired coal-containing agglomerates for blast furnace in a blast furnace is caused by friction (surface destruction) with other blast furnace raw fuels (sintered ore, pellets, coke, etc.). Therefore, as a strength index, it is suitable to use the pulverization rate of the uncalcined coal-containing agglomerate for blast furnace after the reaction in hot water (high temperature, under reducing atmosphere).
So far, in order to improve the hot strength of uncalcined coal-containing coal-containing agglomerates for blast furnaces, various technological developments have been made regarding the production conditions thereof (Patent Documents 2 to 6).

However, most of them use the load capacity due to volumetric fracture instead of the pulverization rate due to surface fracture as a strength index (Patent Documents 1 to 4), and it cannot be said that the strength suitable for use in a blast furnace can be evaluated. Further, for those focusing on pulverization in a high temperature and reducing atmosphere in a furnace (Patent Document 6), a preferable particle size range is narrow (ore: 10 to 50 μm, carbon-containing raw material: ~ 100 μm), and high water of crystallization ore. There are problems such as restrictions on the blending amount of water of crystallization (5 to 20% by mass), and restrictions on industrial use are severe.

Japanese Patent No. 5000402 Japanese Patent No. 5835144 Japanese Patent No. 5825180 Japanese Patent No. 5786668 Japanese Patent No. 5454505 Japanese Patent No. 4842403

The present invention relates to T.I. C. Production of non-calcined coal-containing agglomerates for blast furnaces that can achieve high strength without lowering the hot strength of uncalcined coal-containing agglomerates for blast furnaces even if the amount of water-hard binder is small. Provide conditions.

In order to solve the above problems, T.I. C. Manufactures uncalcined coal-containing lump deposits for blast furnaces that can achieve high strength without lowering the hot strength of uncalcined coal-containing lump deposits for blast furnaces I succeeded in doing it. That is,
(1) A method for producing a non-calcined coal-containing lump ore for a blast furnace used as a raw material for a blast furnace in steelmaking.
The uncalcined coal-containing agglomerate ore raw material for the blast furnace has a mass ratio equivalent to zero moisture.
2.0-9.0% by mass of hydraulic binder,
The fine silica source is 1.0 to 4.0% by mass, and the total of the water-hard binder and the fine silica source is 6.0 to 13.0% by mass.
Further, iron-containing raw materials, carbon-containing raw materials, and other raw materials so that the ratio of carbon (TC) contained in the non-calcined coal-containing agglomerate ore raw material for the blast furnace is 15.0 to 40.0% by mass. A total of 87.0 to 94.0% by mass was used.
When the non-fired coal-containing agglomerate ore raw material for blast furnace and water are mixed with a mixer to prepare a mixed raw material, the mass ratio of water is 100. Add water so that the mass ratio of water is 9.0 to 14.0 mass% when it is set to mass%, and mix continuously.
The mixed raw material is applied to the first extrusion section, the vacuum chamber, and the second extrusion section, the filling rate of the first extrusion section is 50 to 90% by volume, and the filling rate of the second extrusion section is 50 to 95% by volume. It is a method of producing a non-calcined coal-containing agglomerate for a blast furnace as a molded body by continuously extruding the mixed raw material by transferring the mixture so as to be.
Using a raw material having a particle size of the mixed raw material of −10 μm powder ratio ≧ 15.0% by mass in the iron-containing raw material,
In the first extrusion portion, the mixed raw material is pushed into a weir formed of a perforated plate installed in front of the transfer direction so that the filling rate is 50 to 90% by volume, so that the mixed raw material is pushed into the first material. Form a seal,
In the vacuum chamber, the mixed raw material continuously supplied from the outlet side of the weir is evacuated and transferred to the second extrusion section.
In the second extrusion section, the vacuum degassed mixed raw material supplied from the vacuum chamber is pushed into a molding section having a large number of holes so that the filling rate is 50 to 95% by volume. The mixed raw material is continuously extruded while forming the second material seal.
The vacuum degassing condition is a method for producing a non-calcined coal-containing agglomerate ore for a blast furnace, which comprises molding at −40 kPaG or less.

According to the present invention, T.I. C. It is possible to produce a non-calcined coal-containing agglomerate for blast furnace suitable for blast furnace charging in the range of 15.0 to 40.0% by mass and the water-hard binder addition rate of 2.0 to 9.0% by mass. Contributes to low-reduction material ratio operation.

It is a figure which shows the example of the vacuum extrusion molding machine used in this invention. It is a figure which shows the mixed raw material filling rate of the 1st and 2nd extruding part. It is a figure which shows the outline of the load softening test apparatus which simulated the inside of a blast furnace. It is a figure which shows the temperature rise pattern at the time of a test using the load softening test apparatus which simulated the inside of a blast furnace. It is a figure which shows the outline of the tumbler tester. It is a figure which shows the relationship between the powder ratio of -10 μm in an iron-containing raw material and the powdering ratio after a reaction. It is a figure which shows the relationship between the degree of vacuum and the reaction pulverization rate.

As described above, the raw material of the non-calcined coal-containing agglomerate for blast furnace is generally composed of three kinds of a carbon-containing raw material as a reducing agent, an iron-containing raw material as an iron source, and other raw materials. Then, a hydraulic binder and a fine silica source are mixed with these three kinds of raw materials to prepare a non-calcination coal-containing agglomerate ore raw material for a blast furnace, and water is further added and mixed, and then molded to obtain a coal-containing agglomerate ore. .. Each item will be described below.

material;
"1" Iron-containing raw material The residue after determining the addition rate of the carbon-containing raw material and the binder is used as the iron-containing raw material. Examples of iron-containing raw materials include iron ore crushed to a predetermined particle size, iron ore fine powder (pellet feed), dust, sludge, scale, etc., which generate a large amount of carbon in the iron-making process and contain a large amount of iron components. Can be used. Further, grinding debris from a rolling roll or an aggregate such as iron ore or sinter that has fallen during the transportation process of the ironmaking process may be used, or powder generated during the molding process of the coal-containing agglomerate ore. And fragments are also included in the iron-containing raw materials.

"2" Carbon-containing raw material In order to enjoy the merit of reducing the ratio of reducing agent in the above-mentioned blast furnace, T.I. C. Is about 15.0 to 40.0% by mass. For example, common coke breeze is T.I. C. Is about 85% by mass, so when these are used for RCE, the blending ratio is about 24.0% by mass. As the raw material containing carbonaceous material, fine powder obtained by carbonizing coal such as powdered coke obtained by crushing coke to a predetermined particle size or dust collected from a coke oven is preferable, but it contains a large amount of carbon content generated from anthracite, coal, and a blast furnace. You may use dust or the like.

"3" Other raw materials Refers to sludge, slag, etc., which have a small amount of iron components (iron content of 30% by mass or less) or do not contain iron components, especially in the iron making process. Carbon may be contained due to the low iron content.

"4" Hydraulic binder, etc. Next, the concept for reducing the blending ratio of the hydraulic binder required for the strength development of the non-calcined coal-containing agglomerate for blast furnace will be described. The hydraulic binder is sometimes simply called cement, and means a binder having a function of increasing the cold crushing strength of the granulated product by hardening by a hydration reaction with water contained in the raw material or added water. Water-hard binders include Portland cement (specified in JIS R 5210), mixed cement (blast furnace cement (specified in JIS R 5211)), silica cement (specified in JIS R 5212), and fly ash cement containing calcium silicate. (Specified in JIS R 5213)), ultrafast hard cement, blast furnace slag, etc. are used, but the present invention is not limited thereto.

Since the hydrate formed by the hydraulic binder is decomposed in the blast furnace, the strength held by the hydraulic binder gradually decreases in the furnace. In order to compensate for this decrease in strength, it has been necessary to add about 10% by mass of a hydraulic binder in the prior art.

However, hydraulic binders such as cement, which are restricted to blast furnace charging, have a mass ratio of 2.0 to 9.0 mass% in terms of zero moisture, and fine-grained SiO2 as a curing accelerator has a mass ratio of 1 in terms of zero moisture. If the hydraulic binder and fine-grained SiO2 are excessive in the range of 0 to 4.0% by mass, the blast furnace input reducing material and slag increase, and the merits of the non-fired coal-containing agglomerate for blast furnace are offset, which is too small. If this is the case, the required strength cannot be achieved and the blast furnace cannot be charged. Here, the mass of each raw material in terms of water content is determined by the following method. Put each raw material of about 2 to 3 kg into a dryer set at 105 ° C or higher, and continue drying until the weight loss is less than 0.1% per hour (usually about 6 to 12 hours), and the total weight loss is reduced. Ask for. The total weight loss before drying / the weight of the raw material before drying is defined as the water content ratio of the raw material, and the weight of the raw material before drying − (weight of the raw material before drying × the water content ratio) is defined as the mass of the raw material converted to zero moisture.

Therefore, in the present invention, attention is paid to the Me-Fe bond formed between the iron-containing raw material particles by reducing the uncalcined coal-containing agglomerate for blast furnace in the blast furnace. If a dense Me-Fe bond can be spread in the non-calcined coal-containing agglomerate for blast furnace, the hot strength of the non-calcinated coal-containing agglomerate for blast furnace can be improved without using a hydraulic binder. I think I can.

The degree of formation of the Me-Fe bond is determined by the properties and arrangement of the iron-containing raw material particles and the carbon-containing raw material particles constituting the uncalcined coal-containing agglomerate for blast furnace. Specifically, the reactivity of the iron-containing raw material particles, the reactivity of the carbon-containing raw material particles, and the degree of proximity between the iron-containing raw material particles and the carbon-containing raw material particles are important.

"5" Fine-grained silica source The fine-grained silica source includes not only silica fume and microsilica but also fly ash. The weight ratio of the above raw materials is converted to zero water content, the water-hard binder is 2.0 to 9.0% by mass, the fine silica source is 1.0 to 4.0% by mass, and the total of the water-hard binder and the fine silica source is 6. The iron content should be 0.0% by mass or more, and the ratio of carbon (TC) contained in the non-fired carbon-containing agglomerate ore raw material for blast furnace should be 15.0 to 40.0% by mass. A total of 100% by mass of the raw material and water is added to the non-fired carbon-containing agglomerate ore raw material for blast furnace, which is a total of 87.0 to 94.0% by mass adjusted by adjusting the mixing ratio of the raw material, carbon-containing raw material, and other raw materials. The mass ratio of water when% is 9.0 to 14.0 mass% is added and continuously mixed to obtain a molding raw material.

In the examples of the present invention, in consideration of the above conditions, for example, Table 1 below is used as an example of the compounding conditions.

Method for producing uncalcined coal-containing agglomerate for blast furnace In the present invention, in order to reduce voids in the non-calcined coal-containing agglomerate for blast furnace as much as possible, FIG. The vacuum extrusion molding method as shown in is adopted. In the vacuum extrusion molding method, a strong agglomerate ore with few air-derived voids is produced by degassing the raw material in the vacuum chamber shown in FIG.

The coal-containing lump ore manufacturing apparatus 10 includes a mixer 1, a charging port 2, a first extrusion section 3, a vacuum chamber 4, a second extrusion section 5, a molding section 6, and a vacuum pump 7.

The first extruded portion 3 (also referred to as a kneaded portion) is a uniaxial screw feeder having a cylindrical casing 3a and a screw 3b rotatably arranged inside the casing 3a and continuously formed vertically. Is. The screw 3b is rotated by a driving means (not shown). The upper portion of the base portion of the casing 3a is connected to the input port 2 by the connecting pipe 8. A weir 3c formed of a perforated plate is arranged at the tip of the casing 3a. In the present embodiment, the weir 3c formed of the perforated plate has a structure in which a large number of holes are formed in a thick plate-shaped disk.

A second extrusion portion 5 is arranged below the first extrusion portion 3. The tip of the first extrusion 3 and the base of the second extrusion 5 are connected by a vacuum chamber 4. The vacuum chamber 4 is connected to the vacuum pump 7 by a vacuum pump connecting pipe 9. The second extrusion portion 5 (also referred to as an extrusion molding portion) is a uniaxial type having a cylindrical casing 5a and a screw 5b rotatably arranged inside the casing 5a and continuously formed vertically. It is a screw feeder. The screw 5b is rotated by a driving means (not shown). A molding portion 6 is attached to the tip of the casing 5a. In the present embodiment, the molded portion 6 has a structure in which a large number of holes are formed in a thick disk-shaped disk.

The raw materials of the non-calcined coal-containing lump ore for blast furnace are supplied to the mixer 1 so as to have a predetermined blending ratio, and water is added and mixed to produce a mixed raw material. The mixed raw material is continuously or intermittently charged into the inlet 2. The mixed raw material charged into the charging port 2 is supplied into the first extrusion section 3 through the connecting pipe 8 and is gradually compressed by the screw 3b to reach the weir 3c formed of the perforated plate. At this time, by adjusting the rotation speed of the screw 3b and the supply speed of the mixed raw material so that all the holes of the weir 3c formed of the perforated plate are filled with the mixed raw material, the weir 3c formed of the perforated plate is formed. A material seal is formed. Since the mixed raw material is continuously supplied by the screw 3b, the mixed raw material is continuously discharged into the vacuum chamber 4 while constantly forming a material seal on the back surface of the weir 3c formed of the perforated plate. Will be done. The pore shape of the perforated plate (weir 3c) is not particularly limited, but it is important to adjust the pore diameter and aperture ratio according to the physical characteristics of the mixed raw material so that the material seal can be easily formed. Is.

Since the inside of the vacuum chamber 4 is evacuated by the operation of the vacuum pump 7 connected by the vacuum pump connecting pipe 9, the mixed raw material supplied to the vacuum chamber 4 is degassed, and the raw material particles in the raw material are surely separated from each other. By contacting and densifying, the strength of the produced unfired coal-containing agglomerate for blast furnace can be increased.

The mixed raw material densified in the vacuum chamber 4 is supplied to the second extrusion section 5. The mixed raw material supplied to the second extrusion section 5 is extruded into the molding section 6 by the screw 5b.

As described above, in the example of the production apparatus for the non-calcined coal-containing agglomerate for blast furnace according to the present invention, it was decided to continuously extrude while vacuum degassing using the material seal, so that the productivity was improved. It is possible to improve.
Here, the conditions under which the second material seal can be continuously maintained were investigated. Table 2 shows the contents and results of this survey. From the conditions that satisfy the quality of the uncalcined coal-containing lump ore for blast furnace, which will be described later, the state where the vacuum degassing condition is -40 kPa or less and the continuous operation can be performed for 1 hr or more is evaluated as 〇.

As described above, the second material seal can be formed by installing the adjusted molded portion 6 of the perforated plate in the second extruded portion 5. However, in actual production, the flow resistance of the raw material changes (operation fluctuation) or the screw rotation speed changes (operation action), so that the raw material supply speed to the molding unit 6 changes. For example, if the water content of the raw material becomes excessive, the fluidity of the raw material decreases, the raw material is discharged before the second material seal is formed, and the pressure in the vacuum chamber 4 cannot be stably maintained. A similar change occurs with respect to the increase in the rotation speed of the screw 5b. As a result of investigating these phenomena, when the mixed raw material filling rate of the second extrusion section 5 is less than 50% by volume, the second material seal is likely to collapse when the raw material supply rate to the molding section 6 increases. I found out.

On the other hand, if the flow resistance of the raw material is increased or the rotation speed of the screw 5b is decreased, the amount of the raw material supplied to the molding portion 6 is reduced, and the raw material is transferred from the second extrusion portion 5 to the vacuum chamber 4. It was found that the screw 5b in the second extrusion portion 5 was overloaded and easily stopped due to excessive accumulation. As a result of the investigation, it was found that when the filling rate of the second extrusion portion 5 exceeds 95% by volume, the raw materials are likely to be excessively deposited when the supply of the raw materials to the molding portion 6 is reduced.

Therefore, the rotation speed of the screw 5b of the second extrusion portion 5, the rotation speed of the screw 3b of the first extrusion portion 3 upstream of the vacuum chamber 4 and the physical characteristics of the raw material are adjusted at any time, and the raw material filling rate of the second extrusion portion 5 is adjusted. It has been found that by continuing to control the amount to 50% by volume or more and 95% by volume or less, stable and continuous production of a molded product is possible even if there is a change in operation.

The raw material filling rate of the second extrusion section 5 is the ratio of the raw material to the volume of the cylindrical space (excluding the volume of the screw 5b) in which the screw 5b of the second extrusion section 5 is rotating. To say. By controlling the raw material filling rate to 50% by volume or more and 95% by volume or less by increasing or decreasing the rotation speed of the screw 5b of the second extrusion portion 5 and increasing or decreasing the amount of raw material supplied, stable and continuous molding becomes possible.

Here, the determination of the raw material filling rate is performed, for example, as shown in FIG. 2, a first extruded portion raw material level observing portion attached to the upper part of the first extruded portion 3, or an upper portion of the vacuum chamber 4. It is common to visually determine each extruded portion from the observation window at the raw material level of the extruded portion, and determine the visual condition in 5% by volume divisions. This time, in order to determine the raw material filling rate from the screw range that can be seen from the observation window, for example, the relationship between the range where the screw blades are hidden by the raw material and the raw material filling rate is investigated in advance, and filling is performed simply by looking at the screw from the observation window. Although the rate can be determined, for example, even if a level meter (microwave type level meter, proximity sensor, various level switches, etc.) is installed in each part of the extrusion molding part and the filling rate is calculated from the level measurement value. good.

As described above, regarding the control range of the raw material filling rate of the second extrusion portion 5, continuous stable molding is possible if it is 50% by volume or more and 95% by volume or less, but if it is 50% by volume or more and 70% by volume or less. Even better, it is optimal if it is 50% by volume or more and 60% by volume or less. The reason is that by controlling the filling rate to be constant, the force of the screw 5b pressing against the molded portion 6 is stabilized, and the variation of the discharged molded body is reduced.

For the first material seal, the conditions under which it can be continuously maintained are also investigated, and as shown in Table 3, if the raw material filling rate of the first extrusion portion 3 is 50% by volume or more and 90% by volume or less, stable molding is performed. Turned out to be possible. If the filling rate is less than 50% by volume, the material seal cannot be maintained. Further, if the filling rate exceeds 90% by volume, the load tends to be overloaded, or the raw material tends to overflow into the grating portion on the upper surface of the first extrusion portion 3 and the raw material supply chute, which makes continuous operation difficult. Therefore, the raw material filling rate of the first extrusion unit 3 needs to be 50% by volume or more and 90% by volume or less. The filling rate is even better if it is 50% by volume or more and 80% by volume or less, and more preferably 50% by volume or more and 65% by volume or less. The reason is that by controlling the filling rate to be constant, the force of the screw 3b pressing against the perforated plate 3c is stabilized, and the variation of the discharged molded body is reduced. The observation of the first material seal can be performed in the same manner as the second material seal. Since the inside of the container of the first extrusion portion 3 is at normal pressure, the upper surface of the first extrusion portion 3 is usually grating to observe the inside. This is because it has better visibility than a glass window, but it does not matter as long as the inside can be observed.

In the present embodiment, if the particle size of each raw material is 8 mm or less (maximum particle size is 8 mm, average particle size is about 60 to 100 μm), when extruding with the screws 3b and 5b, the mixed raw materials are the screws 3b and 5b. , The casings 3a and 5a, the weir 3c formed of the perforated plate, and the molded portion 6 can pass through the gaps of each, so that they do not mesh with each other, which is preferable. When the mixed raw material passes through the molding portion 6, it is molded into the cross-sectional shape of the molding portion 6. The mixed raw material extruded from the molding portion 6 is broken by its own weight and molded into a molded product having a predetermined length.

The shape of the molded product is determined by the cross-sectional shape of the molded portion 6, and the holes can be formed not only in a cylinder but also in a prism such as a quadrangular prism or a hexagonal prism, but it is most desirable to form the molded product in a cylindrical shape. The reason is described below.

When comparing the ventilation pressure loss of the packed bed of the blast furnace in the non-calcination coal-bearing mass ore for blast furnace of various tendencies, the columnar shape shows the lowest pressure loss. In addition, compared to prisms, the columnar non-calcined coal-bearing agglomerates for blast furnaces are characterized by being less likely to be pulverized when the walls in the packed bed or the coal-bearing agglomerates rub against each other or when a drop impact occurs. be. While agglomerates with a diameter of 30 mm to 40 mm have the highest crushing strength, the raw material charging mechanism into the blast furnace has a structure suitable for transporting raw materials with a diameter of 20 mm or less in accordance with the existing sinter. Therefore, it is desirable to mold it into a columnar shape with a diameter of about 10 to 20 mm.

The molded products are stacked in a covered curing yard and cured in the curing yard for a predetermined period of time. During the curing period, the molded product solidifies and is gradually dehydrated by natural drying to complete the production of a non-calcined coal-containing agglomerate for blast furnace.

Definition of hot strength to be retained by uncalcined coal-bearing agglomerates for blast furnaces;
On the other hand, the hot strength of the uncalcined coal-containing agglomerate for blast furnace, which is an object of the present invention, will be described. When uncalcined coal-containing lump ore for blast furnace is pulverized in the blast furnace, the ventilation in the furnace is deteriorated. Therefore, the strength index that the uncalcined coal-containing agglomerate for blast furnace should hold for use in a blast furnace depends on the pulverization rate after exposure to a high-temperature reducing atmosphere. The powdering rate at this time is preferably low. Specifically, the post-reaction pulverization rate, which describes the measurement method below, was defined and used as a strength index for uncalcined coal-containing agglomerates for blast furnaces.

The method for measuring the pulverization rate after the reaction is as follows: First, a non-calcined coal-containing agglomerate ore is charged into a load softening device simulating the inside of a blast furnace as shown in FIG. 3, and then from room temperature to 900 ° C. as shown in FIG. The temperature is raised at 10 ° C./min, and the reducing gas in the blast furnace is reduced in a simulated gas atmosphere. In this reduction process, the uncalcined coal-containing agglomerate for blast furnace goes through the history of temperature and gas composition of the thick dotted line in FIG. The vertical axis of FIG. 4 is _{the ratio of CO and CO 2 , but in the blast furnace, the ratio of CO and CO 2} changes depending on the temperature range due to the reaction (FeO + CO = Fe + CO ₂ , CO ₂ + C = 2CO), so this reduction process _{However, CO 2} / (CO + CO ₂ ) is changed according to the temperature range of the uncalcined coal-containing agglomerate for blast furnace. The heating rate of 10 ° C./min reproduces the heating rate of the charged material in the furnace. The uncalcined coal-containing agglomerate for blast furnace cooled to room temperature after the temperature rise to 900 ° C. is completed is rotated at 30 rpm for 4 minutes in a tumbler tester as shown in FIG. Then, the entire amount of the sample is sieved with a test sieve having an opening of 1 mm. Then, the mass of the sample under the sieve and the mass of the sample on the sieve are measured, respectively, and the mass fraction of the sample under the sieve is obtained by the following formula (1). This value is defined as the post-reaction pulverization rate.
Post-reaction pulverization rate [-1 mm mass%] = Under-sieve sample mass [kg] / (Unsieve sample mass [kg] + Sieve sample mass [kg]) × 100 ... (1)

In order to use a non-calcined coal-containing agglomerate ore for a blast furnace, the post-reaction pulverization rate should be low, and for stable use, the post-reaction pulverization rate is about 16.0% by mass or less. Is preferable.

Improved reactivity of each raw material;
[1] Improvement of Reactivity of Iron-Containing Raw Material Particles Further, the reactivity of the iron-containing raw material is generally improved by making the particles finer (increasing the specific surface area). Here, the ore used as an iron-containing raw material for the non-calcined coal-containing agglomerate for blast furnace is determined from the aspect of the ore situation (cost, stable supply) at that time, and may not be changed freely. It is preferable that the brand and properties are not limited. Further, for industrial use, it is difficult to cut only fine particles from a wet powder such as a raw material for non-calcined coal-containing agglomerates for blast furnaces, so an index that imposes an upper limit on the ratio of fine particles is not preferable. In the present invention, as shown in FIG. 6, by using an index of -10 μm powder ratio, which is a fraction of fine particles having a particle diameter of 10 μm or less in the iron-containing raw material, the same index can be used for different ore brands. I found that it can be organized.

From FIG. 6, in order to lower the post-reaction pulverization rate, the higher the -10 μm powder ratio in the iron-containing raw material, the better, and for the post-reaction pulverization rate [-1 mm mass%] ≤ 16 mass%, It is necessary that the powder ratio of −10 μm in the iron-containing raw material is 15.0% by mass or more. In FIG. 6, various ores are used, and if there are different plots with the same name, it means that the particle size of the ore is adjusted (crushing, etc.). Excessive particle size adjustment (crushing, etc.) of the iron-containing raw material increases the installation cost and running cost of the equipment required for the operation, and reduces the merit of the present invention. Therefore, the upper limit of the -10 μm powder ratio is preferably about 35.0% by mass, which can be realized by a ball mill or the like that is relatively inexpensive and capable of mass processing (another particle size adjusting method such as a roller mill is also possible). Here, the particle size distribution of each raw material was measured by using a sieve for particles of 1 mm or more and a laser diffraction / scattering type particle size distribution measuring device for particles of less than 1 mm. However, other measuring methods (wet sieving, etc.) capable of measuring fine particles can be used instead. The vacuum degassing condition of the vacuum chamber 4 in FIG. 6 is −90 to −75 kPaG.

[2] Reactivity of carbon-containing raw material particles The reduction of iron-containing raw material by carbon-containing raw material is the reduction gas and solid iron generated by the reaction by contact between solid carbon-containing raw material and solid iron-containing raw material or by gasification of carbon-containing raw material. It proceeds by the reaction due to the contact of the contained raw materials. Here, if the particles of the carbon-containing raw material are too coarse, the inside of the particles cannot contribute to the reduction reaction, and the reducing ability is lowered. On the other hand, if the particles of the carbon-containing raw material are too fine, the gasification proceeds too quickly, and the reducing gas is released to the outside of the system before reacting with the iron-containing raw material particles.

[3] Proximity of particles of iron-containing raw material and particles of carbon-containing raw material In order to promote the reduction reaction, the particles of the iron-containing raw material and the particles of the carbon-containing raw material which is the reducing material should be arranged as close as possible. preferable. Here, in a non-calcined coal-containing agglomerate for a blast furnace, in general, the voids between particles are mainly occupied by water and air. It is necessary to reduce this void as much as possible in order to arrange the iron-containing raw material particles and the other carbon-containing raw material particles in close proximity to each other.

In the present invention, by using the vacuum extrusion molding method of FIG. 1 described above, air-derived voids in the uncalcined coal-containing agglomerate for a blast furnace are reduced, thereby forming a non-calcined coal-containing agglomerate for a blast furnace having a high specific density. Manufacture ore. FIG. 7 shows the relationship between the degree of vacuum and the post-reaction pulverization rate [-1 mm mass%]. In order to lower the post-reaction pulverization rate [-1 mm mass%], it is better that the degree of vacuum in vacuum extrusion molding is low, and for the post-reaction pulverization rate [-1 mm mass%] ≤ 16 mass%. It is necessary that the degree of vacuum is -40 kPaG or less. The degree of vacuum can theoretically be reduced to −101.13 kPaG, but an excessive reduction in the degree of vacuum leads to an increase in equipment costs such as a vacuum pump, so the lower limit of the degree of vacuum is reached by a general vacuum pump. Possible about -98.0 kPaG is preferable. The powder ratio of −10 μm in the iron-containing raw material in FIG. 7 is 26.9%.

Next, examples of the present invention will be described, but the present invention is not limited thereto. As the raw material for the non-calcined coal-containing agglomerate for blast furnace, a carbon-containing raw material, an iron-containing raw material, and other raw materials were used, and T.I. C. Was adjusted. As the carbon-containing raw material, coke breeze (TC = 84%) and iron-making dust (TC = 23%) having a high carbon content were sieved with a 5 mm sieve, and the under-sieve was used. As iron-containing raw materials, ore P (Australian powder ore), ore B, F (Brazilian powder ore), and ore C (Canada powder ore) are crushed with a ball mill, sieved with a 5 mm sieve, and under the sieve. Was used. As the hydraulic binder, early-strength cement was used. Silica fume and fly ash were used as the fine silica source. The raw materials were weighed, the whole amount was put into a uniaxial paddle type continuous mixer and mixed for 1 minute, then a predetermined amount of water was added and mixed for 3 minutes to prepare a mixed raw material. The mixed raw material is put into an extrusion molding apparatus composed of a uniaxial screw type kneader and a uniaxial screw type extrusion molding unit, and the extrusion speed (the speed at which the raw material passes through the hole of the molding unit 6) is 10 mm /. The molding test was carried out after adjusting so as to be s. The diameter of the holes (perforated) in the extruded portion was set to φ16 mm. The details are shown in Table 4 (Table 4-1 and Table 4-2) and Table 5.

Regarding the evaluation of the material seal, when the vacuum pump shown in FIG. 1 is started, the vacuum degassing condition in the vacuum chamber 4 can be continuously maintained at -40 kPa or less (for example, continuous 1 hr or more), and the vacuum degassing condition is-. A state in which the value did not decrease to 40 kPa or less or a state in which the vacuum deaeration condition fluctuated intermittently and the state of −40 kPa or less could not be maintained continuously (for example, continuously 1 hr or more) was evaluated as ×.

The agglomerated coal-containing agglomerate ore is air-cured at room temperature for 1 day, then placed in a constant temperature and humidity chamber at 80 ° C. for 2 days to be cured, and then air-cooled to 30 ° C. Then, after charging the uncalcined coal-containing lump ore for the blast furnace into the load softening device simulating the inside of the blast furnace as shown in FIG. 3, the temperature is 10 ° C./min from room temperature to 900 ° C. as shown in FIG. The temperature is raised and the reducing gas in the blast furnace is reduced in a simulated gas atmosphere. Then, after rotating at 30 rpm for 4 minutes with the above-mentioned tumbler tester as shown in FIG. 5, the entire amount of the sample is sieved with a test sieve having an opening of 1 mm, and the sample mass under the sieve and on the sieve are measured, respectively. According to (1), the mass fraction of the sample under the sieve is obtained and used as the post-reaction pulverization rate. As the post-reaction pulverization rate [-1 mm mass%], the above-mentioned 16.0% or less was accepted.

In Table 4 (Table 4-1 and Table 4-2), Examples 1 to 21 are described in T.I. C. Under the condition of = 15.0 to 40.0% by mass, the water-hard binder = 2.0 to 9.0% by mass, the fine silica source = 1.0 to 4.0% by mass, and the water-hard binder and the fine silica source. The total is 6.0 to 13.0% by mass, the moisture content of the molded product is 9.0 to 14.0% by mass, the filling rate of the first extrusion portion 3 is 50 to 90% by mass, and the second extrusion portion is In the case of molding with the filling rate of 5 being 50 to 95% by volume, the pulverization rate after the reaction is about 16% by mass or less.

In Table 5, Comparative Example 1 is an example in which the powder ratio of −10 μm in the iron source-containing raw material is out of the lower limit. The -10 μm powder ratio in the iron source-containing raw material affects the degree of formation of Me-Fe bonds when the uncalcined coal-containing agglomerate for blast furnace is reduced in the blast furnace. The Me-Fe bond is not sufficiently formed, and the pulverization rate after the target reaction cannot be secured. Comparative Example 2 is an example in which the upper limit of the vacuum degassing condition is not exceeded. The degree of vacuum affects the degree of proximity between the iron source-containing raw material particles and the carbonaceous material-containing raw material particles in the uncalcined coal-containing agglomerate for blast furnace. If the degree of vacuum does not satisfy the condition, the iron source-containing particles and the carbonaceous material-containing particles are not sufficiently close to each other, and the formation of the Me—Fe bond is inhibited, so that the pulverization rate after the target reaction cannot be secured. Here, in Comparative Example 2, in order to determine the upper limit of the vacuum degassing condition, the valve of the vacuum pump is adjusted and the vacuum degassing condition is raised under the condition that the first and second material seals are stably formed. rice field. The higher the vacuum degassing condition, the smaller the density of the mixed raw material, so the force required for extrusion can be small, but under conditions exceeding -40 kPa, even if that state can be maintained stably, the target reaction The post-pulverization rate cannot be achieved. Comparative Example 3 is an example in which the filling rate of the first extrusion section 3 is out of the lower limit. The material seal of the first extrusion section 3 whose filling rate is out of the lower limit cannot be stably maintained, and the vacuum degassing condition is set to-. Since stable operation cannot be performed at 40 kPa or less, the post-reaction pulverization rate of the uncalcined coal-containing agglomerate for blast furnace does not become 16% by mass or less. Comparative Example 4 is an example in which the filling rate of the first extrusion portion 3 is out of the upper limit. If the filling rate exceeds the upper limit, the load of the first extrusion portion 3 becomes excessive and the operation is stopped. Comparative Example 5 is an example in which the filling rate of the second extrusion section 5 is out of the lower limit. The material seal of the second extrusion section 5 whose filling rate is out of the lower limit cannot be stably maintained, and the vacuum degassing condition is set to-. Since stable operation cannot be performed at 40 kPa or less, the post-reaction pulverization rate of the uncalcined coal-containing agglomerate for blast furnace does not become 16% by mass or less. Comparative Example 6 is an example in which the filling rate of the second extrusion portion 5 is out of the upper limit. If the filling rate exceeds the upper limit, the load of the second extrusion section 5 becomes excessive and the operation is stopped.

1 Mixer 2 Input port 3 First extrusion section (kneading section)
3a Casing 3b Screw 3c Weir formed of perforated plate 4 Vacuum chamber 5 Second extrusion section (extrusion molding section)
5a Casing 5b Screw 6 Molding part 7 Vacuum pump 8 Connection pipe 9 Vacuum pump connection pipe 10 Manufacturing equipment for unfired coal-containing agglomerate for blast furnace

Claims (1)

A method for producing a non-calcined coal-containing lump ore for a blast furnace, which is used as a raw material for a blast furnace in steelmaking.
The uncalcined coal-containing agglomerate ore raw material for the blast furnace has a mass ratio equivalent to zero moisture.
2.0-9.0% by mass of hydraulic binder,
Fine silica source 1.0-4.0 mass%,
Moreover, the total of the hydraulic binder and the fine silica source is 6.0 to 13.0% by mass.
Furthermore, the total of iron-containing raw materials, carbon-containing raw materials, and other raw materials is 87.0 so that the proportion of carbon contained in the non-firing carbon-containing agglomerate ore raw material for the blast furnace is 15.0 to 40.0% by mass. Using a mixture of ~ 94.0% by mass,
When the non-fired coal-containing agglomerate ore raw material for blast furnace and water are mixed with a mixer to prepare a mixed raw material, the mass ratio of water is 100. Add water so that the mass ratio of water is 9.0 to 14.0 mass% when it is set to mass%, and mix continuously.
The mixed raw material is applied to the first extrusion section, the vacuum chamber, and the second extrusion section, the filling rate of the first extrusion section is 50 to 90% by volume, and the filling rate of the second extrusion section is 50 to 95% by volume. It is a method of producing a non-calcined coal-containing agglomerate for a blast furnace as a molded body by continuously extruding the mixed raw material by transferring the mixture so as to be.
Using a raw material having a particle size of the mixed raw material of −10 μm powder ratio ≧ 15.0% by mass in the iron-containing raw material,
In the first extrusion portion, the mixed raw material is pushed into a weir formed of a perforated plate installed in front of the transfer direction so that the filling rate is 50 to 90% by volume, so that the mixed raw material is pushed into the first material. Form a seal,
In the vacuum chamber, the mixed raw material continuously supplied from the outlet side of the weir is evacuated and transferred to the second extrusion section.
In the second extrusion section, the vacuum degassed mixed raw material supplied from the vacuum chamber is pushed into a molding section having a large number of holes so that the filling rate is 50 to 95% by volume. The mixed raw material is continuously extruded while forming the second material seal.
A method for producing a non-calcined coal-containing agglomerate ore for a blast furnace, characterized in that the vacuum degassing condition is -40 kPaG or less.

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