JPH024928A - Method for cooling high-temperature reduced pellet - Google Patents

Abstract

PURPOSE:To decrease the pulverization of reduced pellets and to reduce reoxidation rate by forming high-temp. reduced pellets into a thin layer by means of plural strickles provided to the inlet side of a rotary cooler and also carrying out water-spray cooling at the time of introducing high-temp. reduced pellets into the rotary cooler. CONSTITUTION:High-temp. reduced pellets 8 reduced by heating in a rotary kiln 1 are introduced via a chute 2 into a rotary cooler 3. At this time, water is sprayed in the vicinities of a position E in the inclined part of the chute 2, a position F in the inlet part of the rotary cooler 3, and a position G in the middle part of the rotary cooler 3 by means of spray nozzles 4, 5, 6, respectively, by which the high-temp. reduced pellets 8 can be cooled down to <=about 80 deg.C. Further, L-shaped plural strickles 7 are provided to the internal wall on the inlet side of the rotary cooler 3 and a basket-shaped partition chute is formed by means of the rotation of the above strickles 7, and, when the reduced pellets 8 exceed the angle of repose of about 35 deg., the pellets 8 are discharged in the forward direction, by which a thin layer of <=about 50mm thick is formed. By this method, the pulverization rate of the reduced pellets 8 can be decreased and also reoxidation rate can be reduced.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a method for cooling high-temperature reduced pellets, and more particularly, to a method for cooling high-temperature reduced pellets that reduces powdering of finished reduced pellets and suppresses the reoxidation rate. .

BACKGROUND OF THE INVENTION Conventionally, dust and other iron-containing waste gas discharged from blast furnaces in large quantities is heated and reduced at high temperatures in a rotary kiln to form reduced pellets, which are then used as raw materials for iron ore. Various methods have been proposed for producing reduced pellets, as some cooling methods may lead to a decrease in quality.

For example, there is a method in which reduced pellets that have been reduced at a temperature of about 1300° C. in a rotary kiln are cooled with water spray in a rotary cooler. However, in this method, the round thickness of the pellet is 500 mm.
Since it is approximately 600 mm, it may result in uneven cooling.
Furthermore, since the cooling time is as long as about 60 seconds, the reduced pellets at a temperature of 500°C or higher are easily oxidized by oxidizing gas during the cooling process, and are reoxidized by about 5 to 7% during water spray cooling.
There is a problem that the quality of the product deteriorates (Japanese Patent Laid-Open No. 56-1
52933).

In addition, there is a so-called submersion method in which high-temperature reduced pellets are immersed in water, but this method can suppress the reoxidation rate to about 1%, but it is not preferable because it increases the powdering rate and the product yield is poor (JP-A-49 Publication No.-96901, JP-A-56-15293
Publication No. 3).

Problems to be Solved by the Invention The present invention aims to solve these problems, and specifically,
When reducing pellets obtained by high-temperature reduction in a rotary kiln are cooled with water, the problem of pulverization can be alleviated in conventional methods, but re-oxidation occurs at the stage of reaching the desired cooling temperature, resulting in reduced pellets of good quality. What you can't get, and what's more,
The purpose of this invention is to solve the problem that a cooling method for obtaining good quality products has not yet been researched or developed.

Means for Solving the Problems and Their Effects Namely, the present invention provides a plurality of scraping plates on the inner wall of the entrance side of the cooler when introducing high-temperature reduced pellets heated and reduced by a rotary kiln into a rotary cooler and cooling them. The method is characterized in that after a thin gap of reduced pellets is formed in the area by providing a thin layer of reduced pellets, the area is cooled by water spraying.

Therefore, the structure of these means and their operation will be explained in more detail as follows.

First, the present inventors conducted research on a conventional cold filling method, that is, a water sprinkling cooling method for high-temperature reduced pellets that causes less powdering.

FIG. 6 is a cross-sectional side view illustrating the process in which high-temperature reduced pellets are cooled by the rotary cooler 3 from the discharge side of the rotary kiln 1 in a conventional example.

As shown in FIG. 6, the high-temperature reduced pellets heated to about 1300°C by a burner and reduced in a reducing gas atmosphere are introduced into the rotary kiln 3 from the discharge side of the rotary kiln 1 through the chute 2. . In the cooler 3, the high temperature reduction pellets 1 to 1 are usually about 200 to 3
The product moves with a layer thickness of 0.00111 m, is sprayed with water by the spray nozzle 5 on the inlet side, and is cooled to about 80° C. or less, and is obtained from the outlet.

Therefore, the present inventors investigated the relationship between the positions of rotary kiln outlet A, chute B, rotary cooler population part C, and rotary cooler outlet in this cooling process and the return rate (%). The results shown in the graph in the figure showed a tendency for the reduction rate to decrease as the reduced pellets moved from the rotary kiln discharge port toward the rotary cooler discharge port. It was found that the reoxidation rate was large during the period.

Therefore, the present inventors conducted research on conditions for reducing powdering and preventing reoxidation in such a water spray cooling method, and the present invention was established based on this research.

Further, the present invention will be explained in detail with reference to the drawings as follows.

In addition, FIG. 1 is a cross-sectional view seen from the side to explain an example of a water cooling device used when carrying out the present invention, and FIG. 2 is a cross-sectional view taken along the line A-A in FIG. 3 is a sectional view taken along line B-B in FIG. 1, FIG. 4 is a sectional view of the rotary cooler in FIG. 1 seen from the side of the inlet side, and FIG. It is an explanatory view of spray piping.

1 is a rotary kiln, 2 is a chute, 3 is a rotary cooler, 4 is a spray nozzle of the chute, 5 is a spray nozzle on the artificial side of the rotary cooler, 6 is a spray nozzle in the middle of the rotary cooler, 7 is a scraping plate, 8 is a reduced pellet, 9 is a In the spray piping, 10 is a pump, 11 is a flow meter, and 12 is a flow control valve.

First, in FIG. 1, high-temperature reduced pellets indicated by reference numeral 8 are introduced from the discharge side of the rotary kiln 1 through the chute 2 into the rotary cooler 3. Furthermore, spray nozzles 4,5,6 are installed near the position E of the inclined part of the chute 2 as shown in FIG. 2, the position F of the inlet part of the rotary cooler 3 as shown in FIG. Water is injected to cool the high-temperature reduced pellets 8 to a temperature of about 80° C. or lower. Note that if the layer thickness at position E on the inlet side of the rotary cooler 3 is thick, cooling will be uneven, so in order to make the layer thickness thinner and uniform cooling,
The inner wall of the rotary cooler 3 on the inlet side has an angle of repose of 35 when the reduced pellets rotate in a single-shape direction in the direction of rotation.
A plurality of scraping plates 7 are provided to form a packet-shaped partition chute, and the thickness of the reducing pellet 80 introduced into the partition chute is determined as follows: It is configured to have a thin N of 100 mm or less, preferably 50 mm or less. Moreover, it is preferable to be able to control the thickness to be further reduced each time the rotation speed of the rotary cooler is increased.

As described above, the high temperature reduced pellets 8 are cooled by the spray nozzles 4.5 and 6, and the watering time is 1.
While the temperature is uniformly cooled to approximately 80°C within 1 minute, the chute of the packet-shaped partition rotates, and the angle of inclination of the scraping plate 7 changes to the angle of repose of the reduced pellets (
α) When the angle is 35° or more, it rolls on the scraper plate 7 (partition shoe 1-) and is ejected forward. At this time, the cooling time and speed are controlled by the number of revolutions of the cooler, the location of watering, etc.
This can be done by changing the amount of water sprinkled, etc.

As explained above, since the high-temperature reduced pellets are formed into a thin layer on the inlet side of the rotary cooler 3, water spray cooling can be performed uniformly, and there is less pulverization compared to the conventional submersion method. However, re-oxidation can be suppressed and reduced pellets 1 of good quality can be obtained.

Example First, using the cooling device shown in FIG. 1, reduced pellets 1 to 1 heated to 1300°C with a particle size of 15 to 25 mm were heated in a rotary kiln 1 at a rotation speed of 1 at a speed of 16 t/b.
Introduced into rotary cooler 3 rotating at m/SeC,
Water spray cooling was performed on the reduced pellets moving in a rotary cooler with a layer thickness of 50 mm.

The rotary cooler 3 has an inner diameter of 5,400 mmφ, and a 1-shaped scraping plate as shown in Figs. 7 at 22.5° intervals,
A structure was used in which when the reduced pellet 8 rotated and the angle of repose α of the reduced pellet 8 became 35° or more, it rolled from the scraper plate 7 and was ejected forward.

Water cooling is performed by spraying water from the tip spray nozzles 4.5 and 6 of the spray piping 9 shown in FIG. The spray pipe 9 was installed as shown in FIG. 5.

In addition, water is supplied at position F by using a flat spray nozzle (number of 31110752 series nozzles in 174 5 x 2) using spray nozzle 4 at a rate of 0.75 to 3 t/l).
The gas was supplied at a rate of 1,000 ml, to block the entry of oxidizing gases, and to cool the gas. At position F, spray nozzle 5 (3/4 S
E 4 to 8 tons depending on the number of 3090H2 series nozzles (3 x 2)
It was fed and cooled at a rate of /h. Furthermore, at position G, the spray nozzle 6 is replaced with an oblique flat nozzle (SH4 in 1/2
065-ORO 1 series nozzle number 2) 0.75 to 3
t/I). At this time, the water from the pump 10 was controlled by the flow meter 71 and the flow m control valve 12 so that the total amount of water supplied was at a rate of 8 t/h.

As mentioned above, when the reduced pellets 8 at 1300° C. were cooled with water spray, a product with a moisture content of 0.5% or less, little powdering, and a reoxidation rate of 2% or less was obtained.

<Effects of the Invention> As explained above, the present invention provides a method for introducing high-temperature reduced pellets heated and reduced by a rotary kiln into a rotary cooler and cooling them by providing a plurality of scraping plates on the inner wall of the inlet side of the cooler. This method of cooling high-temperature reduced pellets is characterized by forming a thin layer of reduced pellets on the area and then cooling the area with water spray.

Therefore, in the conventional water cooling method, the remelting rate is about 5 to 7.
%, but with the present invention, it has been possible to suppress it to about 2%.In addition, the powdering rate of the finished product is lower than that of the conventional submersion method, and due to the characteristics of the raw materials, the strength is high and powdering is prevented. If the temperature is low, increase the cooling rate and increase the temperature of the reduced pellets to 1300~5.
By cooling the temperature between 00° C. and 1 in a short period of time, it is possible to further reduce the reoxidation rate.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view illustrating one embodiment of a water cooling system used in carrying out the present invention, Fig. 2 is a sectional view taken along line A-A in Fig. 1, and Fig. 3 is a cross-sectional view taken along line B-B in Figure 1, Figure 4 is a cross-sectional view of the rotary cooler on the artificial side of Figure 1, Figure 5 is an explanatory diagram of the spray piping in Figure 1, and Figure 6 is 7 is a side cross-sectional view of a conventional water cooling device, and FIG. 7 is a graph showing the relationship between the position of the cooling process in FIG. 6 and the reduction rate. Code 1...Rotary kiln 2...Chute 3...Rotary cooler 4.5.6...Spray nozzle 7...
Scraping plate 8... Reducing pellets 9... Spray piping 10... Pump 11... Flow meter 12... Flow rate control valve Fig. 2 Figure 3

Claims (1)

[Claims] 1) When introducing high-temperature reduced pellets heated and reduced by a rotary kiln into a rotary cooler and cooling them, a plurality of scraping plates are provided on the inner wall on the entrance side of the cooler to form a thin layer of reduced pellets at the relevant portions. A method for cooling high-temperature reduced pellets, which comprises cooling the pellets with water.