JPH07166223A - Method for recovering iron and reformed slag - Google Patents

Abstract

PURPOSE:To recover iron and simultaneously recover reformed slag as well by adding a mixture composed of metal aluminum, common salt and calcium fluoride to a raw material for steel making contg. iron oxides to effect reaction. CONSTITUTION:The mixture composed of the metal aluminum (aluminum ashes, etc.), the common salt (pulverized matter of original salt, etc.) and the calcium fluoride (pulverized matter of natural fluorite, etc.) is added by a carrier gas (nitrogen) to the raw material for steel making contg. the iron oxides (Fe2O3, Fe3O4, FeO) to effect reaction. The iron is recovered from a reaction product and thereafter, silica sand is added thereto at need and the reformed slag is recovered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering iron from iron oxide contained in a steelmaking raw material and recovering a modified slag.

[0002]

2. Description of the Related Art A mixture of metallic aluminum powder and iron oxide is generally called a thermite agent. When it is ignited, it causes a so-called thermite reaction to generate heat at a high temperature, and thus has a use as a heat generating agent. Law and iron,
It is used in reduction metallurgy of metal oxides such as chromium, manganese, and cobalt. Further, in place of the metal aluminum used in the thermite agent, so-called aluminum ash, which is generated on the surface of molten aluminum during refining of metal aluminum or when regenerating metal aluminum from aluminum scraps, etc. Since it contains metallic aluminum, it is partially used as part of effective utilization of industrial waste.

However, in an electric furnace steelmaking method such as a steelmaking method using an arc type electric furnace, even if the reaction heat is partly used by adding a thermite agent, the thermal energy to be added from the outside is still present. Since it is large and the reducing power is inferior, it takes a lot of time to make steel. Therefore, conventionally, there has been a problem that it is necessary to shorten the steelmaking time by using gas or heavy oil as an auxiliary heat source. Therefore, the present inventors focused on the problems of the electric furnace steelmaking method using such a conventional thermite agent, and provide an exothermic reducing agent that can obtain higher thermal energy and reducing power than the conventional thermite agent. Invented an electric furnace steelmaking method using this exothermic reducing agent.

The ironmaking raw materials used in the electric furnace steelmaking method may contain a large amount of iron oxide, but these iron oxides eventually become a part of the slag during the oxidation period of the steelmaking process and become slag. The amount increases. Here, it is possible to recover iron from this slag by treating with a coke blast furnace. However, in reality, due to various costs such as transportation and recovery, most of the oxidation stage slag of the electric furnace steelmaking method is only crushed after cooling and used as crushed stone,
Its value was very low, and effective utilization was desired.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the low value of the oxidization stage slag in the electric furnace steelmaking method, and provides a method for recovering iron and reformed slag from a steelmaking raw material containing iron oxide. To do.

[0006]

The method for recovering iron and modified slag according to the present invention is characterized by adding a mixture of metallic aluminum, salt and calcium fluoride to a steelmaking raw material containing iron oxide. This is a method of collecting the modified slag. The method for recovering iron and modified slag of the present invention is characterized in that a mixture of metallic aluminum, salt and calcium fluoride is added to a steelmaking raw material containing iron oxide to recover iron, and then silica sand is added. It is a method of recovering iron and modified slag.

Here, when a steelmaking raw material containing iron oxide is melted and a mixture of metallic aluminum, common salt and calcium fluoride is added, the mixture is blown from a lance with a carrier gas to add the mixture. It is preferable because it is stirred by the bubbling action and reacts quickly and efficiently. Further, at this time, it is preferable to use nitrogen as the carrier gas because unnecessary oxygen does not enter the furnace and the reducibility of metallic aluminum in the addition mixture can be effectively used. Similarly, it is preferable to add this mixture directly to the molten slag in terms of effective utilization of the reducibility of the added mixture. In addition, it is preferable to add silica sand to the melt-modified slag after recovering iron, because a more modified slag can be obtained. The present invention will be described in more detail below.

Metallic aluminum (M.
The Al) may contain impurities to some extent, and the aluminum ash described above can also be preferably used. Table 1 shows an example of the composition of aluminum ash.

[Table 1]

The iron oxide may be any of Fe ₂ O ₃ , Fe ₃ O ₄ and FeO in the form of an oxide, and may be used in the production of steel products such as continuous casting, ingots and steel. A so-called scale generated in a process of rolling or forging a piece, a slag in the oxidation period of an electric furnace steelmaking method, or scrap iron can also be suitably used. Table 2 shows an example of the composition of the scale.

[Table 2]

Further, as salt, raw salt or rock salt (NaCl
A pulverized product having a purity of about 96 to 97%) can be used, and as the calcium fluoride (CaF ₂ ), a natural fluorite pulverized product having the composition shown in Table 3 can be used.

[Table 3]

Among these blended compositions, M.Al, common salt and calcium fluoride are used as fine particles having a diameter of about 1 mm or less. Table 4 shows the practical compounding composition of the mixture used in the examples and its compounding ratio.

[Table 4] The mixture of metallic aluminum, salt and calcium fluoride used in the present invention may be used by premixing a steelmaking raw material containing iron oxide (see Table 5).

[Table 5]

An outline of the electric furnace steelmaking method using the exothermic reducing agent of the reference example will be described. First, the scrap iron 3 is loaded into an electric furnace 1 (a lid and an electrode are omitted) as shown in FIG. 1, and the exothermic reducing agent 2 (having the composition shown in Table 5) is packed in a paper bag or a hemp bag to remove the scrap iron 3. It is placed in the middle of the stack. This is because the exothermic reducing agent 2 ignites at a temperature of about 700 ° C. or higher. Next, when the lid is covered in the electric furnace 1 and the electrode is inserted and electricity is applied, the partially melted steel hot water flows downward and comes into contact with the exothermic reducing agent 2, and the exothermic reducing agent 2 ignites and reacts rapidly and violently. Generates heat and rises to high temperature. Due to this high temperature, the scrap iron 3 around the exothermic reducing agent 2 is rapidly melted to form a steel hot water, and the iron oxide in the scale is reduced by metallic aluminum and recovered by a short-time energization, and is integrated with the molten steel. The conventional electric furnace steelmaking method is performed in the same manner as this reference example except that the exothermic reducing agent is not used.

The method for recovering iron and modified slag of the present invention is
As shown in FIG. 2, by pre-energizing the scrap iron 3 loaded in the electric furnace 1, the lance pipe 5 is used to energize the molten steel 4 immediately before the oxidation period to the reduction period after most of the scrap iron is melted and enters the reduction period. While continuing, blow a mixture of aluminum metal, salt and calcium fluoride. In this case, strong reduction, deoxidation, dephosphorization, and degassing are performed simultaneously with the temperature rise of the molten steel, and the iron oxide in the molten steel raw material that should eventually be absorbed by the slag or the oxidation contained in the slag itself. The iron is reduced to recover the iron, which is integrated with the molten steel, and the modified slag containing less iron oxide is recovered. Further, as another effect, the steelmaking time in the reduction period can be shortened. In addition, in FIG.
Is a lid of the electric furnace 1, and 7 is an electrode.

[0014]

[Function] Iron oxide in the steelmaking raw material is reduced with a mixture of metallic aluminum, sodium chloride and calcium fluoride (reaction formulas (1) to (3) of the reduction reaction are shown below) to become iron and become integrated with molten steel. The iron oxide in the slag is reduced, and the rest becomes reformed slag. In addition, according to these formulas, aluminum of aluminum metal (Al = 26.98) 1
It can be seen that 1 to 1.5 atoms of iron (Fe = 55.85) in iron oxide react with the atoms and are reduced and recovered. Therefore, the amount (weight) of slag is reduced. 2Al + Fe ₂ O ₃ → 2Fe + Al ₂ O ₃ + heat of reaction …… (1) 2Al +3/4 Fe ₃ O ₄ → 9/4 Fe + Al ₂ O ₃ + heat of reaction… (2) 2Al + 3FeO → 3Fe + Al ₂ O ₃ + Heat of reaction (3) Simultaneously blowing in a mixture of aluminum metal, sodium chloride and calcium fluoride to accelerate deoxidation, dephosphorization and degassing, while shortening the reduction period due to its strong reducing power. You can

The reason why a higher temperature than the conventional thermite agent can be obtained when a small amount of each of salt and calcium fluoride is added to the conventional thermite agent composed of a mixture of M.Al and iron oxide is the above formula. M ・ Al as shown in 1) to 3)
It is considered that this is because the heat of reaction generated by the reaction between the calcium fluoride and sodium chloride shown in Formula 4) at a high temperature is added to the heat generated by the reaction between the iron oxide and iron oxide. CaF ₂ + 2NaCl → 2NaF + CaCl ₂ + heat of reaction …… (4)

[0016]

【Example】

(Reference example) Scrap iron 18 in an electric arc furnace with a capacity of 200 tons
A paper bag filled with 0 tons and filled with 1000 kg of a mixture having the composition and the blending ratio shown in Table 6 was placed in the center of the scrap iron.
Then, cover the lid and insert the electrodes to energize (energized voltage 550 to 550
700V).

[Table 6]

After energization, the partially melted molten steel flowed downward and contacted with the exothermic reducing agent, the mixture ignited and reacted at once, and the temperature around this mixture reached a high temperature of about 2700 ° C. This temperature is approximately 2200 ° C when using the conventional thermite agent.
Considerably higher than. Due to this high temperature and strong reducing power, the scrap iron in the furnace is quickly melted and the melting time including the oxidation period and the reduction period is shortened.
It was possible to shorten from 1 minute to 1 hour and 15 minutes. Therefore,
It was possible to reduce the power consumption corresponding to this shortened time. It was also found that the amount of the exothermic reducing agent used per molten steel t can be reduced to 1 to 3 kg / t as compared with 3 to 4 kg / t of the conventional thermite agent.

(Example of conventional electric furnace steelmaking method) 180 tons of scrap iron was loaded into an arc type electric furnace having a capacity of 200 tons in the same manner as in the reference example except that the reducing mixture was not arranged. Then, cover the lid and insert the electrodes to energize (energizing voltage 550 to 700
V) Immediately before entering the reduction period from the oxidation period, iron oxide contained in scrap iron or oxides such as calcium and silicon gathered on molten steel to form molten slag. This molten slag was about 20 tons. When its composition was examined, it was as shown in Table 7 as a raw material slag.

(Embodiment 1) In a slag pan 8 having the structure shown in FIG. 3, 5 tons of the above-mentioned electric furnace molten slag (its composition is
It is shown in Table 7 as the raw material slag. ) Was added to the mixture, and 1200 kg of a mixture having the composition and blending ratio shown in Table 4 above was added.
Was blown from the lance tube 10 using nitrogen of 2.5 to 4 kg / cm ² for 5 to 7 minutes, and the slag temperature was 1350.
The temperature rose from around 0 ° C to 1620 ° C, iron was recovered from the slag, and molten steel accumulated at the bottom of the pan 8. The composition of the slag recovered after the reaction is shown in Table 7. The amount of recovered reduced iron was about 1200 kg.

[Table 7]

Example 2 Table 4 was carried out in the same manner as in Example 1 except that the molten slag having the composition shown in Table 8 was used.
When the mixture was blown in, the composition of the slag after the reaction was as shown in Table 8, and the reduced molten steel could be injected into the mold 12 from the outlet 15 to form an atypical product. The weight of the recovered reduced iron was 1250 kg.

[Table 8]

Furthermore, about 1000 g of silica sand is added to this slag.
When kg was blown from the lance with nitrogen, the temperature of the slag, which had been raised to 1620 ° C. by the above mixture, dropped to 1490 ° C. In this way, the vitrified molten slag 11 was poured into the mold 12 to make various types of atypical products.

[0022]

According to the present invention, iron can be recovered from a steelmaking raw material containing iron oxide, and at the same time, modified slag can be recovered. This melt-modified slag is capable of producing various types of atypical products by using a mold. Further, by blowing the above mixture, there is a secondary effect that the reduction period can be shortened in the electric furnace steelmaking by the strong reducing power while promoting the deoxidizing, dephosphorizing and degassing actions.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an electric furnace steelmaking method of a reference example.

FIG. 2 is an explanatory view of a method for recovering iron and modified slag according to the present invention.

FIG. 3 is an explanatory view of a method for recovering iron and modified slag according to the present invention.

[Explanation of symbols] 1 Electric furnace 2 Exothermic reducing agent 3 Scrap iron 4 Molten steel 5 Lance tube 6 Lid 7 Electrode 8 Slag pan 9 Lid 10 Lance 11 Molten slag 12 Cast iron or slag mold 13 Stamping material 14 Molten steel or Slag removal Outlet plug

Claims (4)

[Claims] 1. A method of recovering iron and modified slag, which comprises adding a mixture of metallic aluminum, salt and calcium fluoride to a steelmaking raw material containing iron oxide and reacting the mixture. 2. An iron and a modified slag, characterized in that a mixture of metallic aluminum, salt and calcium fluoride is added to a steelmaking raw material containing iron oxide and reacted to recover iron, and then silica sand is added. Recovery method. 3. The method for recovering iron and modified slag according to claim 1 or 2, wherein the steelmaking raw material containing iron oxide is molten slag. 4. The iron and reforming according to claim 1, wherein a mixture of metallic aluminum, sodium chloride and calcium fluoride is added to a steelmaking raw material containing iron oxide by using a carrier gas. How to collect slag.