JPH07100830B2 - Pretreatment method for sintering raw material - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pretreatment method for a sintering raw material to be supplied to a DL type sintering machine, and in particular, improves the properties of an iron ore for sintering having a high water content of crystallization. The present invention relates to a pretreatment method for recovering and using the iron ore as return ore and for reducing the coke ratio during sintering and stabilizing the sintering operation.

2. Description of the Related Art In the production of sinter by the DL type sintering machine, as shown in the production process in FIG. 3, iron ore and limestone having various miscellaneous properties were granulated by adding powder coke as fuel. The raw material (1) is loaded into a sinter machine pallet (3) on which a bed ore (2) is laid, the surface of the raw material layer is ignited by an ignition furnace (4), and air is sucked through a wind box (5). As a result, the pallet (3) is sintered from the upper side toward the lower layer.

The red hot sinter ore (6) discharged from the sintering machine is hot crushed by the crusher (7), enters the cooler (8), and is classified by the product sieve (9), and the sieve top is transferred to the blast furnace. After being sent, the undersize is used again as a raw material for sintering. (13) is a raw material tank, and (14) is a mixer.

By the way, among the iron ore used for the production of the above-mentioned sinter,
Some contain 5.0% or more of water of crystallization (CW). When such iron ore having a high content of water of crystallization is directly used as a sintering raw material, the water of crystallization is thermally decomposed and an endothermic reaction occurs in the process of sinter generation, resulting in a decrease in the sintering temperature and the sintering process. Retaining and worsening productivity.

Therefore, iron ore with such a high water content of crystallization is
It is necessary to decompose the water of crystallization by some treatment in advance. However, in order to industrially decompose the water of crystallization in iron ore, a temperature of 500 ° C. or higher is required, and a large amount of energy and equipment cost are required to perform such high temperature heat treatment.

Therefore, for example, Japanese Patent Application Laid-Open No. 63-128127 proposes a method of using iron ore having a high content of water for crystallization as a bed ore. However, iron ores with a high content of water of crystallization have the characteristic that water of crystallization decomposes when exposed to high temperatures, causing thermal cracking. However, there is a problem that clogging of the pallet grate causes deterioration of air permeability, which hinders firing. Furthermore, when using iron ore with a high fine particle ratio,
Since the bed ore had a particle size restriction, it was necessary to perform a granulation process.

Problem to be Solved by the Invention The present invention is viewed from such a conventional situation as described above, by heat-treating an iron ore with a high content of high crystal water as a sintering raw material without a large capital investment, as a sintering raw material, It is intended to propose a pretreatment method that can be modified into a high-quality sintering raw material that does not hinder firing.

Means for Solving the Problems The present invention uses a waste heat of red-hot sinter for heat treatment of inferior iron ore having a high water content of crystallization, thereby improving the quality of a sintering raw material without restriction of grain size. This is a pretreatment method that can be performed, and its gist is to install iron ore with a high water content of crystallization (CW) of 5% or more in a cooler together with the red-hot sinter ore discharged from the sintering machine and hot-crushed. This is a sintering raw material pre-treatment method in which the iron ore is heat-treated by the exhaust heat of the red-hot sinter, and then recovered as ore under the sieve during product classification.

Action The sinter cake discharged from the sinter is crushed hot by the crusher and supplied to the cooler, but the cooler inlet temperature of the hot crushed red-hot sinter is about 500 ° C.

On the other hand, in order to dehydrate the water of crystallization in the iron ore containing 5% or more of water of crystallization in a short time, a heat treatment temperature of at least 200 ° C. or higher is required.

Therefore, in the heat dehydration treatment of iron ore containing 5% or more of water of crystallization, it is possible to sufficiently utilize the cooler exhaust heat of the red hot sinter.

That is, when both the red-hot sinter and the iron ore containing 5% or more of water of crystallization are charged into the cooler, the iron ore mixed with the red-hot sinter receives the thermal energy from the exhaust heat of the red-hot sinter and undergoes a dehydration reaction. Cause During this dehydration reaction, the iron ore is thermally cracked, and most of it is sieved during product classification and recovered as return ore. There is almost no water of crystallization in this recovered return ore,
It can be used as a good raw material for sintering.

In the present invention, the reason for limiting the water of crystallization to 5% or more is that if the water content is less than 5%, the dehydration reaction rate becomes slow in the heat treatment of about several hundred degrees by the cooler, and as a result, the water of crystallization remains. .

Here, the results of investigating the initial ratio of water of crystallization and the time required for dehydration are shown in FIG. FIG. 1 shows the experimental results when 100 g of iron ore with a grain size of 10 to 5 mm was used under the condition of heat treatment temperature of 500 ° C. using air as the heat treatment atmosphere.

From FIG. 1, it can be seen that the treatment time can be greatly improved when the water of crystallization ratio is 5% or more.

The reason why a lower proportion of water of crystallization requires more time for dehydration will be described below.

The dispersion of water of crystallization in iron ore is almost uniform. that is,
This is because the crystal water is regularly arranged in microscopic crystal structure units. In other words, a very small amount of crystal water
The higher the ratio of water of crystallization, the denser the packing in the iron ore,
As a result, the distance between the water of crystallization and the distance between the water of crystallization and the surface of the iron ore become shorter.

When the iron ore containing this crystal water receives thermal energy,
Heat is transferred from the surface of the iron ore and the temperature rises. Therefore,
The higher the content of water of crystallization is, the faster the initiation of the dehydration reaction of water of crystallization becomes.

Moreover, the water of crystallization is vaporized by dehydration and the volume of the water is expanded.
The energy causes the iron ore to first crack locally at the water of crystallization. The impact force of this thermal crack extends toward the center of the iron ore and causes cracks and the like.

It is presumed that these cracks are extremely minute, but heat is also transmitted from the voids, etc., and the localized dehydration vaporization reaction proceeds at an accelerated rate due to a chain reaction. Finally, the water of crystallization is completely dehydrated, and iron ore becomes fine powder of 4 mm or less.

On the other hand, the iron ore having a low content of water of crystallization not only delays the initial localized dehydration / vaporization reaction, but also the above chain reaction due to the coarse arrangement of water of crystallization. As a result, the water of crystallization remains after the heat treatment even though the initial ratio of water of crystallization is low.

This tendency is also strong in the case of coarse particles having an initial particle size of 5 mm or more. Moreover, the ore remaining while containing the water of crystallization does not undergo thermal cracking, and thus has a large grain size. Therefore, the coarse particles are sieved by the product sieve while containing the crystal water, and are directly sent to the blast furnace, which adversely affects the operation of the blast furnace.

Therefore, the iron ore to be subjected to the heat treatment of the present invention is limited to those having a water of crystallization of 5% or more.

In addition, the recovery of most of the iron ore with a product sieve means that at least 90% or more of the total amount of the iron ore is recovered under the sieve, and the value of the recovery rate is determined by the sieve mesh representative diameter, the sieve efficiency, and the like.

In addition, there are various types of coolers, and in addition to a straight or circular moving bed type cooler, a vertical countercurrent or cocurrent moving bed is used to cool the cooling gas and red hot sinter ore. There are methods such as cooling by heat exchange, but any method can be applied.

Example 1 Example 1 FIG. 2 is an equipment flow showing a pretreatment method of the present invention.
(10) is a hopper for charging the iron ore (11) having a water content of crystallization of 5% or more into the cooler (8).

That is, according to the present invention, together with the red hot sinter ore (6) discharged from the DL type sintering machine and crushed by the crusher (7), the iron ore (11) with a high content of crystal water in the hopper (10) is used.
Is charged into the cooler (8).

The iron ore (11) mixed with the red-hot sinter (6) causes dehydration heat cracking due to the exhaust heat of the red-hot sinter, and is completely dehydrated in the cooler (8) to form fine powder with a particle size of 4 mm or less. And is discharged from the cooler.

The sintered ore discharged from the cooler (8) and the iron ore in the form of fine powder are classified by the product sieve (9), and the upper part of the sieve is recovered into the blast furnace, and the lower part of the sieve, that is, the sintered powder and the iron ore are recovered as return ore. Is
Used as a sintering raw material.

Example 2 The effect obtained when the sintering operation was carried out under the conditions shown in Table 2 by the sintering equipment having the specifications shown in Table 1 was compared with the conventional method and the method out of the conditions of the present invention. Shown in the table.

In Tables 2 and 3, the present invention introduces Lobe River (8.2% of water of crystallization), which is an iron ore with a high water content of crystallization, into the cooler inlet through a separate line, and introduces it together with the red-hot sinter ore. An example in which Hammasley (2.8% of crystal water), which is a kind of red iron and steel, is supplied to the cooler in the same way as in the present invention, the conventional method 1 is to granulate and sinter the iron ore containing a large amount of crystal water together with other raw materials. The example of the raw material, the conventional method 2, is an example of using the lobe river, which is an iron ore with a high water content of crystallization, alone to granulate and use it as a bed ore.

In the present invention and the comparative example, the total sintering raw material + cooler charging raw material, the conventional method 1 total sintering raw material + bed ore, and the conventional method 2 total sintering raw material are each expressed in weight per unit time. Conducted in agreement. Also,
The sintered new raw materials for each had the same brand composition.

As shown in Table 3, the present invention significantly improves the production rate, powder coke unit consumption and electric power as compared with the conventional method 1 which is a conventional normal sintering method and the conventional method 2 which uses an iron ore with a high water content of crystallization. I understand that it will be done.

Further, in the comparative example in which iron ore (Hamasley) with low crystal water was put into the cooler, the production rate, powder coke basic unit,
Although the electric power is the same as that of the present invention, the crystal water content is as low as 2.8%, so that the crystal water remains in the sintered product, resulting in poor quality.

Effects of the Invention As described above, the present invention has the following effects.

Since the iron ore for sintering with a high water content of crystallization can be reformed into a good quality sintering material by pretreatment, an increase in the coke ratio during sintering can be prevented.

Iron ore with a high content of water of crystallization has been modified into a high-quality sintering raw material, and thus does not hinder firing.

 There is no restriction on the particle size of iron ore.

As an additional sintering facility, there is only a hopper for charging iron ore with a high water content in the cooler, and there is no restriction on the particle size of the raw material charged in the cooler, so a classifier, crusher, granulator No additional equipment such as machines is required.

The cooling effect of the red hot sinter increases, and the cooler power can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing the results of investigating the initial crystallization water ratio of iron ore in the present invention and the time required for dehydration, and FIG. 2 is an equipment flow showing the pretreatment method of the present invention, FIG. Is an equipment flow showing a conventional pretreatment method. 1 ... Raw material, 2 ... Floor mat, 3 ... Sintering machine pallet, 4 ... Ignition furnace, 5 ... Wind box, 6 ... Red-hot sinter, 7 ... Crusher, 8 ... Cooler, 9 ... Product Sieve, 10 …… Hopper 11 …… High water content of crystal iron ore

Claims (1)

[Claims] 1. Crystal water (CW) in the production of sinter.
0% or more of iron ore is charged into the cooler together with the red hot sinter that is discharged from the sinter and crushed by hot crushing, and the iron ore is heated by the exhaust heat of the red hot sinter, and the iron ore A pretreatment method for a sintering raw material, characterized in that most of it is recovered as an undersize return ore at the time of product sieve classification.