JP2008025934A - Method for producing desiliconized slag rough concentrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a desiliconized slag rough mineral concentrate which is an inexpensive iron source for obtaining molten iron by being charged with iron ore into a blast-furnace. <P>SOLUTION: The method comprises drying a desiliconized slag coagulated mass so that the moisture content is 5% by mass or less, crushing the resulting desiliconized slag coagulated mass into desiliconized slag grains, sorting desiliconized slag magnetized grains attracted to a magnet from the desiliconized slag grains, and classifying the desiliconized slag magnetized grains so that the mixing ratio of particle size of 5 mm or less is 5% by mass or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a desiliconized slag coarse concentrate that can recover iron from desiliconized slag generated in the hot metal pretreatment and can be charged into a blast furnace as an iron source together with iron ore.

In the ironmaking process in which iron ore is charged into a blast furnace to obtain hot metal, not only iron ore but various iron sources are used. For example, technology to charge scrap and dust into the blast furnace as an iron source has been studied.
(a) Effective use of resources by using scrap and dust that have been disposed of as industrial waste as raw materials for making iron,
(b) It has been found that effects such as effective use of energy and reduction of CO ₂ emissions can be obtained by being able to melt scrap and dust with less heat than iron ore smelting reduction.

Patent Document 1 discloses a technique of using hot briquette reduced iron (so-called HBI) or direct reduced iron (so-called DRI) as an example of a technique for reusing scrap and dust as an iron source. However, since HBI and DRI are expensive, the technology disclosed in Patent Document 1 causes an increase in raw material costs.
Japanese Patent Laid-Open No. 10-36906

  An object of this invention is to provide the manufacturing method of the desiliconization slag coarse concentrate used as an inexpensive iron source for charging a blast furnace with iron ore and obtaining molten iron.

  The inventor paid attention to desiliconized slag generated in the hot metal pretreatment as an iron source used with iron ore in the iron making process. The hot metal pretreatment refers to the process of removing Si, P, and S in the hot metal in the process of transporting the hot metal obtained in the iron making process (ie, blast furnace) to the steel making process (ie, converter). It is a general term for treatment (so-called desiliconization treatment), treatment for removing P (so-called dephosphorization treatment), and treatment for removing S (so-called desulfurization treatment).

Of the hot metal preliminary treatment, the desiliconization treatment is performed by adding a desiliconizing agent to the hot metal before being accommodated in the kneading vehicle on the cast floor of the blast furnace. Slag generated by the desiliconization process (hereinafter referred to as desiliconization slag) is discharged from the kneading vehicle before the dephosphorization process and contains a large amount of metallic Fe. Therefore, the inventor conducted intensive research on a technique for solidifying and crushing the desiliconized slag and using it as an iron source in the iron making process. as a result,
(1) regulates the amount of water contained in the crushed desiliconized slag coagulum,
(2) Define the particle size distribution of the crushed desiliconized slag coagulum.
(3) By satisfying the condition that the metal Fe content in the crushed desiliconized slag coagulated material is selected, it is found that the desiliconized slag coagulated material can be operated without any trouble by charging it into the blast furnace. It was. Here, in order to distinguish from a desiliconized slag in a molten state, the solidified desiliconized slag is referred to as a desiliconized slag solidified product.

The water of (1) above is cooling water sprayed when cooling the desiliconized slag in a molten state discharged from the kneading vehicle, or rainwater entering during storage of the desiliconized slag coagulum outdoors. .
The present invention has been made based on these findings.
That is, according to the present invention, after the moisture content of the desiliconized slag coagulum is dried to 5% by mass or less, the desiliconized slag coagulum is crushed into desiliconized slag particles, and further adsorbed on the magnet from the desiliconized slag particles. This is a method for producing a desiliconized slag coarse concentrate in which the desiliconized slag magnetically-adhered grains to be selected are classified, and the desiliconized slag magnetically-adhered grains are classified so that the blending ratio of the particle diameter of 5 mm or less is 5 mass% or less.

  In the method for producing the desiliconized slag crude concentrate of the present invention, it is preferable to dry the desiliconized slag solidified product by sun drying. Also, among the desiliconized slag magnetized particles, the desiliconized slag magnetized particles having a particle size exceeding 50 mm are crushed and subjected to magnetic selection, and the particles adsorbed on the magnet are classified to a compounding ratio of particle size exceeding 5 mm and 50 mm or less. Is preferably 90% by mass or more. Further, it is preferable that the desiliconized slag magnetically-adhered granule is crushed, sorted by magnetic force and classified twice or more so that the content of metallic Fe is 70% by mass or more.

According to the present invention, it is possible to produce a desiliconized slag coarse concentrate that is an inexpensive iron source for obtaining molten iron by charging into a blast furnace, and charging the desiliconized slag coarse concentrate together with iron ore into the blast furnace. Thus, reduction of raw material costs, effective use of resources, effective use of energy, and reduction of CO ₂ emissions can be achieved.

  The molten desiliconized slag is cooled to obtain a desiliconized slag solidified product. The method for cooling the desiliconized slag in the molten state is not particularly limited, and a conventionally known method such as a method of spraying cooling water and cooling it with water or a method of storing it outdoors and letting it cool is used. Even if which method is employ | adopted, the obtained desiliconization slag solidified material is dried and the water content in a desiliconized slag solidified material is reduced. If the water content exceeds 5% by mass, heat energy is consumed to evaporate the water when it is charged into the blast furnace as an iron source, resulting in an increase in energy loss. Therefore, it is dried until the moisture content of the desiliconized slag coagulum becomes 5% by mass or less.

A method for drying the desiliconized slag coagulated product is not particularly limited, and a conventionally known method such as drying by heating or drying by blowing is adopted. However, since both heating and blowing consume energy, it is preferable to employ sun drying.
After the desiliconized slag coagulum is dried, the desiliconized slag coagulum is crushed. Here, in order to distinguish from the desiliconized slag coagulated product, the granular material obtained by crushing the desiliconized slag coagulated product is referred to as a desiliconized slag particle.

Next, magnetic separation of desiliconized slag grains is performed. That is, using a magnet, the desiliconized slag grains adsorbed on the magnet and the desiliconized slag grains not adsorbed on the magnet are selected. Here, among the desiliconized slag particles, the desiliconized slag particles adsorbed on the magnet are referred to as desiliconized slag magnetically-adhered particles. The desiliconized slag magnetized particles contain a large amount of metallic Fe.
In this way, the desiliconized slag magnetically-adhered particles of the desiliconized slag particles are collected and classified to adjust the particle size distribution. When the blending ratio of the particle size of 5 mm or less exceeds 5% by mass, a phenomenon (so-called shelf hanging) occurs that aggregates in a hopper stored for charging into a blast furnace and prevents smooth flow. Therefore, the blending ratio with a particle size of 5 mm or less is 5% by mass or less.

A method for classifying the desiliconized slag magnetically-adhered grains is not particularly limited, and a conventionally known method such as a method using a sieving net is adopted. For example, desiliconized slag magnetized particles having a particle size of 5 mm or less are classified using a sieve screen having a mesh opening of 5 mm, and the blending ratio is adjusted to 5 mass% or less by adjusting the blending amount. be able to.
Here, in order to distinguish it from desiliconized slag magnetically-adhered grains whose particle size distribution is not adjusted, what is adjusted so that the blending ratio with a particle size of 5 mm or less is 5 mass% or less is referred to as desiliconized slag coarse concentrate. If this desiliconized slag coarse concentrate is used as an iron source and charged into a blast furnace together with iron ore, reduction of raw material costs, effective use of resources, effective use of energy, and reduction of CO ₂ emissions can be achieved.

  However, if desiliconized slag magnetized particles having a particle size exceeding 50 mm are charged into the blast furnace, the air permeability in the blast furnace may be adversely affected. Accordingly, it is preferable that the desiliconized slag magnetically-adhered particles having a particle size exceeding 50 mm are crushed to a particle size of 50 mm or less. That is, it is preferable that the desiliconized slag crude concentrate has a blending ratio of 5 mm or less in particle size of 5% by mass or less and a blending ratio of 5 mm or more in particle size of 50 mm or less is 90% by mass or more.

  In addition, desiliconized slag coarsely obtained by repeatedly crushing, magnetic separation and classification of desiliconized slag magnetically-adhered grains (that is, 3 times or more by adding crushing, magnetic selection and classification of desiliconized slag coagulum) The concentrate contains 70 mass% or more of metallic Fe. Such a desiliconized slag crude concentrate containing a large amount of metallic Fe is suitable as an iron source charged in a blast furnace.

The desiliconization slag was discharged from the kneading car before dephosphorization treatment was performed after adding the desiliconizing agent to the hot metal discharged from the blast furnace and adding it to the kneading car. This desiliconized slag was deposited in a slag yard and sprayed with cooling water to obtain a desiliconized slag solidified product.
Subsequently, sun drying was performed, and the water content of the desiliconized slag coagulated product was reduced to 3% by mass. After drying in the sun, the desiliconized slag coagulum was crushed into desiliconized slag granules. Further, magnetic separation of desiliconized slag grains was performed, and desiliconized slag magnetically adhered grains adsorbed on the magnet were collected.

Next, the desiliconized slag magnetized particles were classified, and those having a particle size exceeding 50 mm were crushed again, and magnetic separation and classification were performed.
In this way, the blending ratio of the desiliconized slag magnetically-adhered grains having a particle size of 5 mm or less was adjusted to 4 mass% and the blending ratio of the particle diameter exceeding 5 mm to 50 mm or less was adjusted to 3 mass%, and stored as desiliconized slag coarse concentrate. This desiliconized slag crude concentrate was charged into a blast furnace and operated at a ratio of 1 part by mass with respect to 100 parts by mass of iron ore. This is an invention example.

On the other hand, conventionally, desiliconized slag has been disposed of as industrial waste, and no desiliconized slag coarse concentrate has been produced. This is a conventional example. That is, the conventional blast furnace operation does not use desiliconized slag coarse concentrate.
The operation of the invention example was continued for 2 months, and the basic unit of coke in the blast furnace operation was investigated. For the conventional example, an average value of 12 months was calculated from the operation results. The coke basic unit is an index representing the amount of coke used per ton of hot metal, and the smaller the coke basic unit, the smaller the energy consumption.

As a result, the basic unit of coke in the inventive example was reduced by 3 kg / ton compared to the conventional example.
In the inventive examples, there was no shelf hanging in the furnace top hopper.
As described above, according to the present invention, since the basic unit of coke (that is, the amount of coke used per 1 ton of hot metal) has been reduced, effective use of energy and reduction of CO ₂ emissions can be achieved. Moreover, it goes without saying that reduction of raw material costs and effective use of resources can be achieved by recovering metallic Fe from desiliconized slag, which has been disposed of as industrial waste, and charging it into a blast furnace as an iron source.

Claims (4)

  After the moisture content of the desiliconized slag coagulated product is dried to 5% by mass or less, the desiliconized slag coagulated product is crushed into desiliconized slag particles, and desiliconized adsorbed on the magnet from the desiliconized slag particles. The desiliconized slag coarse particles are characterized by selecting slag magnetized grains and classifying the desiliconized slag magnetized grains into a desiliconized slag coarse concentrate having a particle size of 5 mm or less and a blending ratio of 5% by mass or less. Manufacturing method of ore.   The method for producing a desiliconized slag crude concentrate according to claim 1, wherein the desiliconized slag coagulum is dried by sun drying.   Among the above desiliconized slag magnetized particles, the desiliconized slag magnetized particles having a particle size of more than 50 mm are crushed and subjected to magnetic selection, and the particles adsorbed on the magnet are classified so that the blending ratio of the particle size exceeding 5 mm and 50 mm or less is obtained. The method for producing a desiliconized slag crude concentrate according to claim 1 or 2, wherein the desiliconized slag coarse concentrate is 90% by mass or more.   4. The desiliconized slag coarse concentrate having a metal Fe content of 70 mass% or more is obtained by repeating crushing, magnetic sorting and classification of the desiliconized slag magnetically-adhered grains twice or more. Manufacturing method of desiliconized slag rough concentrate.