JPH0459933A - Method for cooling high temperature reduced pellet - Google Patents

Abstract

PURPOSE:To prevent the reoxidation of a reduced pellet in the stage of cooling and to obtain the reduced pellet having excellent quality at high yield by retaining the layer thickness of a reduced pellet to be subjected to water cooling in cooling water in a partition box provided on the inner wall in the input side of a rotary cooler into a specified one. CONSTITUTION:A high temp. reduced pellet 6 of about >=1300 deg.C reduced by a rotary kiln (not shown in fig.) is passed through a chute 7, is introduced into a partition box 2 and accumulates on a bottom plate 8 in the state of an approximately uniform thin layer (<=100mm). This pellet 6 is uniformly and rapidly water-cooled by cooling water from a sprinkler nozzle 11 of sprinkler piping 5, and its reoxidation is prevented. The above partition box 2 is provided preferably in such a manner that the length in the axial direction is regulated to prescribed value or above and the inclined angle of the bottom plate 8 is regulated to the angle of repose of 10 to 25 deg. or below. Furthermore, it is preferable that the number of revolution of the rotary cooler 1 is controlled according to the product of the reduced pellet to secure the above layer thickness.

Description

[Detailed Description of the Invention] Industrial Field of Application The present invention relates to a method for cooling high-temperature reduced pellets, and more particularly, a method for cooling high-temperature reduced pellets by preventing re-oxidation and powdering during water spray cooling and efficiently (cooling) high-temperature reduced pellets. The present invention relates to a method for cooling high-temperature reduced pellets.

Conventional technology For example, there is a method in which pellets containing iron components such as dust are heated and reduced in a rotary kiln to form high-temperature reduced pellets in the exhaust gas discharged in large quantities from blast furnaces, and then cooled to form reduced pellets. Are known.

When producing these reduced pellets using a rotary kiln, the quality may deteriorate depending on the cooling method.
Various cooling methods have been proposed.

For example, as described in JP-A-56-152933,
There is a method in which reduced pellets at 1300° C. or higher that have been reduced in a rotary kiln are introduced into a cooling tank through a chute, cooled by stirring the cooling water with compressed air, and cooled while adjusting the temperature of the cooling water, and then discharged from the cooling tank by a conveyor. However, in this method, the reduced pellets are introduced into the cooling tank using the inclined surface inside the cooling tank, and are cooled by contacting with cooling water.
Since the temperature is about Il, it results in uneven cooling, and the cooling 7j
The IFR period is as long as 60 seconds or more (also, during the cooling process, the reduced pellets are reoxidized by oxidizing gas, etc.
There was a problem that about 5 to 7% of that amount was oxidized, resulting in poor quality of the finished product.

Furthermore, as described in Japanese Patent Application Laid-Open No. 49-96901, reduced pellets heated and reduced in a rotary kiln are cooled to F! There is a method of introducing it into JWI and completely immersing it in cooling water until it reaches room temperature. However, this method has the advantage of suppressing reoxidation of the reduced pellets because there is little contact with air, etc., but has the problem of a high pulverization rate and a low yield of finished products.

In summary, as mentioned above, in the conventional example, cooling methods and devices have been developed in which high-temperature reduced pellets heated and reduced in a rotary kiln for cooling tanks are cooled in water all at once to room temperature. Cooling methods that cause less oxidation and powdering have only been proposed as described in JP-A-56-152933 and vI JP-A-49-96901. For this reason, no method has been proposed for cooling high-temperature reduced pellets without reoxidation or powdering, in which the high-temperature reduced pellets heated and reduced in a rotary kiln are continuously cooled in a rotary cooler.

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically,
If the reduced pellets obtained by high-temperature reduction in a rotary kiln are cooled by contacting them with cooling water for several tens of seconds, the problem of pulverization can be suppressed, but during the cooling process re-oxidation occurs, resulting in reduced pellets with excellent finished product quality. The purpose of the present invention is to solve problems such as the fact that reduced pellets of excellent quality cannot be cooled using a rotary cooler with a high yield, and a method has not yet been researched or developed.

Means for Solving the Problems and Their Effects Namely, the present invention provides a method of providing a partition ellipse on the inner wall of the entrance side of the rotary cooler when high-temperature reduced pellets reduced by a rotary kiln are introduced into the rotary cooler and cooled with water spray. Cooling water is stored in this partition box, and the layer thickness of the reduced pellets submerged and cooled in this cooling water is maintained at 100wn or less, and the high temperature reduced pellets reduced by the rotary kiln are introduced into the rotary cooler. When cooling with water spray, the change in layer thickness due to changes in the supply amount of reduced pellets and the rotation speed of the rotary cooler is determined in advance, and based on the data, the rotation speed of the rotary cooler is adjusted to the supply of reduced pellets. IIJIIIL The layer thickness of reduced pellets is maintained at 100 m or less.

Hereinafter, a detailed explanation of the configuration and the operation of the means of the present invention will be as follows.

In order to solve the problem of reoxidation in the conventional cooling method for high-temperature reduced pellets, the present inventors provided a plurality of partition cells at the inlet of a rotary cooler, and filled the partition cells with cooling water. A method was developed in which the reduced pellets were discharged from a partition box that had been cooled to about 0.9°C and cooled down to room temperature by sprinkling water, and this method was previously proposed in Japanese Patent Application No. 1-194760.

This method is suitable for cooling high-temperature reduced pellets depending on the production volume.When high-temperature reduced pellets are continuously cooled using a rotary cooler (for example, 80% operation or less), the layer thickness of the reduced pellets in the partition box is This is basically a preferable method since it is controlled to 100 mm or less and a reoxidation rate of 2% or less after water cooling is obtained.

However, when producing high-temperature reduced pellets using a rotary kiln, if the amount of reduced pellets in the partition tree provided in the rotary cooler becomes excessive, the reoxidation rate becomes large.

For example, when the WJf inside the partition tree becomes about 150 am or more, the reoxidation rate increases to 4% or less. Therefore, we investigated the cooling method for reduced pellets when the production volume of high-temperature reduced pellets changes, and found that the thickness of the reduced pellet layer within the partition tree of reduced pellets has a large effect.

Further research and development was carried out, and the present invention was established based on the results of this research.

The method of the present invention will be explained below with reference to the drawings.

Note that FIG. 1 is an explanatory diagram showing a cross-sectional structure of an example of an apparatus used when carrying out the method of the present invention.

Code 1 is rotary cooler, 2 is partition tower, 3 is pit,
4 is the pump, 5 is the water pipe, 6 is the transport pellet, 7 is the chute, 8 is the bottom plate, 9 is the draining net, 10 is inside the cooler! ,
11 is a water nozzle, 12 is a water tank, and 13 is a water overflow prevention cover.

First, the rotary cooler 51 shown in FIG. 1 is provided with a plurality of partition walls 2 all around the inner wall on the entrance side of the rotary cooler. Cooling water is supplied into this partition cell 2 from a pit 3 by a pump 4 through a water sprinkling nozzle 11 of a water sprinkling pipe 5 .

When cooling water is filled in this partition cell 2, it overflows from the partition inlet end, passes through the water tank 12, returns to the pit 3, and is configured to be used for circulation.

The axial surface of the rotary cooler 1 is closed in the partition cell 2,
It consists of a draining net 9% on the side surface and an overflow prevention cover 13 on the top surface, the bottom plate 8 has a predetermined inclination angle θ° with respect to the horizontal plane, and the axial length l of the partition cell is a predetermined length. It consists of Incidentally, the inclination angle θ° and the axial length j of the partition cell vary depending on the height of the chute and the amount of pellets passing through, but θ is less than the angle of repose, preferably 10 to 25
°, and l is the pellet passing amount 20 t/'
In the case of about fi, it is preferable to have a length of about 2 to 3 m. The reason for this is that if θ° is too small, the particles will not be transferred and will accumulate directly under the chute, whereas if θ° is too large, the particles will be transferred too much and will be segregated only toward the protrusion of the partition cell 2. Moreover, if l is short, the reduced pellets will become mountain-like, which is undesirable, and if it is longer than necessary, it will be wasteful and impractical.

Next, a method for cooling the reduced pellets will be explained.

1300℃ reduced in rotary kiln (not shown)
The reduced pellets 6 at the above high temperature are introduced into the partition cell 2 through the chute 7 and are deposited on the bottom plate 8 in a substantially uniform thin layer 11 (1
, 001111 or less), while the water is uniformly and rapidly cooled by the cooling water sprayed from the water sprinkling nozzle 11 of the water sprinkling pipe 5, and the water is drained when the temperature reaches about 500 to 600°C by 10 rotations of the rotary cooler. After being drained with a draining net 9, it is discharged from the partition 2 into the inner wall 10 of the rotary cooler. Here, it is further cooled by water spraying until it reaches room temperature. Note that, depending on the degree of water removal, cooling the rotary cooler inner wall 10 with water may not be necessary. The reason for this is that after the reduced pellets are cooled to below 500'C, the rate of reoxidation is slow and does not pose a practical problem.

As described above, by setting the axial length of the partition cell 2 to be greater than a predetermined value and the inclination angle of the bottom plate 8 to be less than the Ansei angle, the layer thickness of the reduced pellets can be reduced to about 100 mm or less. The reduced pellets are uniformly and rapidly (about 4 to 6 seconds)
Since the pellets are cooled to about 00 to 600°C, reduced pellets with a low reoxidation rate (for example, 2% or less) can be produced.

In addition, in the above cooling method, since the layer thickness of the reduced pellets in the partition 2 in the rotary kiln 1 changes in proportion to the production amount of reduced pellets in the rotary kiln,
When producing reduced pellets using a rotary kiln, the layer thickness of the rotary cooler partition increases, making uniform rapid cooling difficult. Therefore, we investigated a method of reducing the layer thickness D of the partition cell to 100 mm or less, and found that it would be sufficient to control the rotation speed of the rotary cooler depending on the production amount of reduced pellets.

The method will be explained below.

In the apparatus shown in Fig. 1, a signal from a weighing machine (not shown) of a charging conveyor on the inlet side of a rotary run is inputted to a variable motor (not shown) of a rotary cooler drive device, and pellets of this charging conveyor are The rotational speed of the rotary cooler 1 should be increased to 1ml in proportion to the weighed value, thereby making the layer thickness of the pellets in the rotary cooler 100 mm or less. In other words, when the production volume increases, the rotation speed of the rotary cooler is increased, and when the production volume decreases, the rotation speed is lowered, thereby keeping the thickness of the partition on the slope angle below a predetermined value. It is something to do.

Hereinafter, the present invention will be specifically explained with reference to Examples.

Example 1゜1 from the rotary kiln to the rotary cooler shown in Figure 1.
14t7 of reduced pellets heated to 300°C or higher
'h speed, inclination angle θ = 20°, axial length j
= 2.5m partition Matsunai reduced pellets - thickness 100m
At the same time, the cooling water is supplied from the bit at a speed of 7t/”h or more, and after the temperature reaches 500 to 600℃ due to the rotation of the rotary cooler, the water is drained with a draining net, and then the inner wall of the rotary cooler is The product was cooled by spraying water from the water spray nozzle 11 until it reached room temperature.The obtained product was not powdered and its reoxidation rate was 2% or less.

For comparison, when a conventional cooling method was used, the reoxidation rate was 4% or more, and it is clear that the method of the present invention is superior.

Example 2゜The speed of reduced pellets fed to the rotary cooler was changed to 2Q.
t and 'h, input the signal from the scale rim of the charging conveyor on the entrance side of the rotary kiln to the same speed motor of the rotary cooler drive device, and control the rotation speed of the rotary cooler in proportion to the weight value of the pellets on the charging conveyor. The same procedure as in Example 1 was carried out except that the Il thickness of the reduced pellets was set to 10011 or less, and even though the production amount of reduced pellets was increased, a product with a reoxidation rate of 2% was produced without powdering. .

<Effects of the Invention> As explained in detail above, the present invention provides a method in which, when high-temperature reduced pellets reduced by a rotary kiln are introduced into a rotary cooler and cooled by water spraying, a partition box is provided on the inner wall of the entrance side of the rotary cooler, Cooling water is stored in this partition pine, and the layer thickness of the reduced pellets submerged and cooled in this cooling water is maintained at 111 times less than 100 mm.Also, the high temperature reduced pellets reduced by the rotary kiln are transferred to the rotary cooler. When cooling with water spray, the change in layer thickness due to changes in the supply amount of reduced pellets and the rotational speed of the rotary cooler is determined in advance, and based on this data, the rotational speed of the rotary cooler is adjusted according to the supply amount of reduced pellets. It is characterized by controlling the thickness of the reduced pellets and keeping the thickness of the reduced pellets at 10100I1 or less.

According to the present invention, the bottom plate of the cooling partition is set at an angle equal to or less than the angle of repose with respect to the horizontal plane, and the length of the rotary cooler in one direction is set to be greater than a predetermined value, so that the high temperature that comes into contact with the cooling water in the partition Since the layer thickness of the reduced pellets is set to 100 m+ or less, it is uniformly and rapidly cooled to 500 to 600°C, and even when cooled to room temperature, excellent products with little re-oxidation and powdering can be efficiently produced.

In addition, the rotation speed of the rotary cooler is controlled according to the production amount of reduced pellets, and the layer thickness of the high-temperature reduced pellets in the partition Matsunouchi is kept at 100IIIll or less, so the rotary cooler can be used regardless of the production amount of reduced pellets. It was hoped that the product would be easy to operate and would have a uniform and low reoxidation rate.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a cross-sectional structure of an example of an apparatus used when carrying out the method of the present invention. Code 1... Rotary cooler 2... Partition box 3... Bit 4... Pump 5... Watering pipe 6... ... Reduction pellets 7 ... Chute 8 ... Bottom plate 9 ... Draining net 10 ... Cooler inner wall 11 ... Water nozzle 12・・・・・・Aquarium 13・・・・・・Overflow prevention cover

Claims (1)

[Claims] 1) When introducing high-temperature reduced pellets reduced by a rotary kiln into a rotary cooler and cooling them with water spray, a partition cell is provided on the inner wall of the entrance side of the rotary cooler, and cooling is carried out within this partition cell. A method for cooling high-temperature reduced pellets, which comprises storing water and maintaining the layer thickness of the reduced pellets submerged and cooled in the cooling water at 100 mm or less. 2) The method for cooling high-temperature reduced pellets according to claim 1, characterized in that the layer thickness of the reduced pellets is maintained at 100 mm or less using a partition box whose bottom surface has an inclined surface in the range of 10° to 25°. 3) When high-temperature reduced pellets reduced by a rotary kiln are introduced into a rotary cooler and cooled by water spraying, a change in layer thickness due to a change in the supply amount of the reduced pellets and the rotation speed of the rotary cooler is determined in advance; A method for cooling high-temperature reduced pellets, which comprises controlling the rotation speed of a rotary cooler with respect to the supply amount of reduced pellets based on this data to maintain the layer thickness of reduced pellets at 100 mm or less.