JP2001348625A - Method for producing pellet for iron-marking raw material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for obtaining a pellet having sufficient strength for iron-making raw material with a little quantity of starch. SOLUTION: Into raw material obtained by using single use of or a mixture of iron-containing powder produced in the iron-making process, such as blast furnace/converter dust, rolling scale, sludge and iron ore powder, carbonaceous material such as coal and coke is added together with starch, mixed and kneaded, and further, a starch solution is supplied to the resultant product at a granulating machine and granulation is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of using iron dust, scale, sludge and iron ore powder, the main components of which are generated in an iron making process, and relates to the use of these in the iron making process by pelletizing them. It is an improvement method.

[0002]

2. Description of the Related Art Conventionally, in the iron making process, for example, blast furnace and converter dust is pelletized, processed in a firing furnace, and then used as a raw material for iron making. Pellets are subject to collapse and powdering due to handling during transportation by truck or conveyor from granulation to the firing furnace, and also due to collapsing and powdering when charged into the firing furnace. It is necessary to secure sufficient strength in order to suppress the generation of dust that lowers the efficiency of the firing furnace and lowers the surrounding environment. Conventionally, in order to increase the pellet strength, a binder is mixed with iron-containing powder, which is a raw material, and pelletized. For example, Japanese Patent Publication No. 56-50157
In the case of 0, a mixture of mineral fine powder and starch is pelletized, and gelatinized starch is added to mineral fine powder and pelletized.

[0003]

However, when the pellets were produced by mixing the iron-containing powder generated in the iron-making process with coal using the above-mentioned pellet production method, it was found that sufficient strength could be obtained with a small amount of starch. could not. If a large amount of starch is used to obtain sufficient strength, the cost of starch as a binder becomes expensive, and further, productivity in granulation is reduced and efficiency in the firing step is reduced. The present invention has been made in view of such circumstances, and an object of the present invention is to provide a pellet for a steelmaking raw material having a sufficient strength by using a small amount of starch.

[0004]

The gist of the production method according to the present invention is as follows: blast furnace / converter dust, rolling scale, sludge,
Iron ore powder and other iron-containing powders generated in the iron-making process can be used alone or in combination with raw materials such as coal and coke,
A method for producing a raw material for ironmaking, comprising adding starch, mixing and kneading, and further supplying a starch solution with a granulator to granulate.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The following experiment was conducted to confirm the operation of the method for producing pellets according to claim 1 of the present invention.
First, according to the method of the present invention, 60% by weight of converter dust
Rolled scale is 25% by weight, and anthracite is blended as a carbon material in an amount of 15% by weight. The raw material is adjusted to a particle size suitable for granulation. %
After changing the mixture, the water content was adjusted to an appropriate level, and the mixture was sufficiently mixed and kneaded by a ball mill, and pelletized by a dish-type granulator having a diameter of 1 m. In the granulator, an aqueous solution in which 5% by weight of starch was dissolved was continuously added in an amount of 2% by weight of the raw material, so that 0.1% by weight of the corresponding raw material was supplied in the form of starch. Thus, the total amount of starch contained in the pellets was 0.1 to 0.6%. The pellet diameter after granulation was 8 to 12 mm, and the pellet moisture content was about 10% by weight. FIG. 1 shows the above-mentioned pelletizing process.

[0006] The crushing strength and drop strength test of the pellets thus produced were performed. FIG. 2 shows the crushing strength measurement results, and FIG. 3 shows the drop strength measurement results as the method of the present invention. Next, for comparison, in the process of the present invention, the supply of the starch aqueous solution in the granulator was stopped, and starch was mixed with a raw material obtained by mixing converter dust, a rolling scale, and anthracite in a ratio of 0.5% and 1.0% by weight of the raw material. To produce pellets. The pellets thus produced were subjected to a crushing strength test and a drop strength test. FIG. 2 shows the crushing strength measurement results, and FIG. 3 shows the drop strength measurement results as a comparison method.

The pellets of the present invention thus produced and the comparative pellets produced by the comparative method are gradually dried by blowing hot air at about 160 ° C. with a band dryer, which is an example of a drying apparatus, to obtain a pellet moisture content. Was sufficiently dried until the content became 1% or less. The pellets thus dried were subjected to a crushing strength test and a drop strength test. FIG. 4 shows the crushing strength measurement results, and FIG. 5 shows the drop strength measurement results as a method for comparison with the method of the present invention.

[0008] Here, the crushing strength refers to the force required for compressive breaking of one pellet, and the drop strength refers to the number of times that one pellet is dropped from a predetermined height onto an iron plate and the pellet is not broken. The drop strength in FIG. 3 shows the result of dropping the pellet from a height of 1 m, and the drop strength in FIG. 5 shows the result of dropping the pellet from a height of 450 mm.

From the above test results, it can be seen that the pellets of the present invention have sufficient strength with a smaller amount of starch used than the pellets produced by the comparative method. In this test, pelletization was performed using a dish-type granulator, but similar results can be obtained by using a drum-type granulator capable of adding a solution during granulation.

[0010]

EXAMPLE According to the method of the present invention, a converter dust, a rolling scale and coal are mixed to obtain a raw material, and starch is added to the mixed raw material, kneaded, water content is adjusted, and pelletized by a plate granulator. did. In the granulator, an aqueous solution in which starch was dissolved was continuously added to the mixed raw material. The pellets thus obtained are guided to a vibrating sieve to select pellets having a diameter in an appropriate range, and the selected pellets are dried in a drier so that the moisture content in the pellets is 1% or less, and then in a firing furnace. Heat treatment was performed.

The specific procedures and conditions are as follows. 60% by weight of converter dust, 25% by weight of rolling scale, and 15% by weight of anthracite as a carbon material were mixed as raw materials,
Further, a mixture obtained by adding 0.2% by weight of starch to this mixed raw material was sufficiently mixed with a mixer, and then adjusted so that the mixed raw material had a water content of 8% by weight. This was introduced into a ball mill, pulverized so that the particle size of the mixed raw material was 1 mm or less, kneaded sufficiently, and then pelletized by a dish-type granulator. In the granulator, 0.1% by weight of the mixed raw material is added by continuously adding an aqueous solution in which 5% by weight of starch is dissolved to the mixed raw material to 2% by weight of the mixed raw material.
Was supplied in the form of a solution, and adjusted so that the total amount of starch contained in the pellets was 0.3% by weight and the moisture content was 10% by weight. The pellets thus obtained are guided to a vibrating sieve, pellets having a particle size range of 8 to 15 mm are selected, and the selected pellets are dried with a band dryer so that the moisture in the pellets is 1% or less, and then transferred to a belt conveyor. Led to the firing furnace.

Table 1 shows the crushing strength, drop strength, powdering rate, and granulation productivity (index) of the pellets collected on the entrance side of the firing furnace. If the powdering rate of the pellets on the inlet side of the firing furnace increases, the efficiency of the firing furnace decreases, so that the pelletizing rate at the inlet of the firing furnace is preferably lower. In addition, the powdering ratio is sampled at a place where the powder falls from a belt conveyor into a firing furnace, and the particle size distribution is measured with a sieve. Further, the productivity is an index with the example taken as 100, and the variation in the production amount is 1 with the particle size range of the pellets produced by the granulator being 8 to 15 mm.
The 8-hour average values when the operation could be continued for 8 hours or more while being kept within 0% were compared.

Comparative Example 1 As Comparative Example 1, 60% by weight of converter dust, 25% by weight of a rolling scale, and 15% by weight of anthracite as a carbon material were used as raw materials, and starch was further added to the mixed raw material. After adding 0.3% by weight, the mixture was sufficiently mixed with a mixer, and then adjusted so that the water content of the mixed raw material became 8% by weight. This was introduced into a ball mill, pulverized so that the particle size of the mixed raw material was 1 mm or less, kneaded sufficiently, and then pelletized by a dish-type granulator. In the granulator, 2% by weight of the mixed raw material is continuously added to the mixed raw material, and the water content is 10% by weight.
Was adjusted to become pellets. After selecting pellets of an appropriate diameter range with a vibrating sieve, drying the pellets with a dryer so that the moisture content in the pellets is 1% or less, guiding the pellets to the firing furnace on a belt conveyor, and crushing the pellets collected at the firing furnace entrance. , Drop strength, powdering rate, and productivity (index) were measured. This is also shown in Table 1.

Comparative Example 2 As Comparative Example 2, 60% by weight of converter dust, 25% by weight of a rolling scale, and 15% by weight of anthracite as a carbon material were used as raw materials, and starch was further added to this mixed raw material. After adding 1.0% by weight, the mixture was sufficiently mixed with a mixer, and then adjusted so that the water content of the mixed raw material became 8% by weight. This was introduced into a ball mill, pulverized so that the particle size of the mixed raw material was 1 mm or less, kneaded sufficiently, and then pelletized by a dish-type granulator. In the granulator, 2% by weight of the mixed raw material is continuously added to the mixed raw material, and the water content is 10% by weight.
Was adjusted to become pellets. After selecting pellets of an appropriate diameter range with a vibrating sieve, drying the pellets with a dryer so that the moisture content in the pellets is 1% or less, guiding the pellets to the firing furnace on a belt conveyor, and crushing the pellets collected at the firing furnace entrance. , Drop strength, powdering rate, and productivity (index) were measured. This is also shown in Table 1.

[0015]

[Table 1]

From the examples in Table 1 and Comparative Example 1, when the same amount of starch was used, the pellets of the present invention had higher crushing strength and drop strength than the pellets produced by the comparative method. It turns out that a favorable result that the pelletization ratio is low can be obtained. Further, from the examples and comparative example 2, it can be seen that a large amount of starch is required in order to obtain a pelletization ratio equivalent to that of the pellets produced by the method of the present invention in the pellets produced by the comparative method. . In addition, it can be seen that the productivity (index) is better in the example.

[0017]

As described above, the method of the present invention has an excellent feature that pellets having sufficient strength can be obtained with a small amount of starch.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a comparison of pellet crushing strength by the method of the present invention and a comparative method.

FIG. 3 is a diagram showing a comparison of pellet drop strength between the method of the present invention and a comparative method.

FIG. 4 is a diagram showing a comparison of pellet crushing strength after drying according to the method of the present invention and a comparative method.

FIG. 5 is a diagram showing a comparison of pellet drop strength after drying according to the method of the present invention and a comparative method.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Akira Nobumoto 1Fuji-cho, Hirohata-ku, Himeji-shi, Hyogo F-term in Nippon Steel Corporation Hirohata Works (reference) 4K001 AA10 BA14 BA15 CA18

Claims (1)

[Claims] An iron-containing powder generated in an iron-making process such as blast furnace / converter dust, rolling scale, sludge, iron ore powder, etc., alone or mixed with a carbonaceous material such as coal and coke and a starch. , Kneading, and granulating by supplying a starch solution with a granulator, and pelletizing the raw material for steelmaking.