JP2520587B2 - Refining slag reforming method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for removing impurities such as phosphorus or sulfur in basic slag generated in a pig-making and steel-making process, and recycling the slag for reuse. Is.

(Prior Art) Conventionally, the slag generated by the hot metal dephosphorization treatment has a high P and S content, and is rarely recycled for reuse in the refining reaction. There is an example in which the high basicity of P-free slag is used to suppress Mn-free, or Fe is recovered, but a large merit is not enjoyed due to the recovery of P and recovery of S. Also, there is a need to reuse the slag generated by converter refining or molten steel dephosphorization for refining to recover Fe content or use high basicity, but the content of P and S is high and it was reused for refining. In this case, recovery from slag,
Due to the S-reversion phenomenon, it was actually difficult to reuse slag by recycling it to smelting.

(Problems to be Solved by the Invention) On the other hand, as a disclosure example of a technique intended to be reused in refining, for example, a dephosphorization treatment as disclosed in JP-A-59-53637 is disclosed. It is said that if the temperature of the later slag together with the carbonaceous substance is raised to a temperature higher than the dephosphorization temperature, the oxides having oxidizing power in the slag are easily reduced by the carbonaceous substance, and stirring is carried out to accelerate these reduction reactions. As a result, slag with low phosphorus is said to be regenerated.

Further, JP-A-57-177911 discloses that a converter slag is charged in a molten bath of an iron alloy containing carbon and silicon, and is stirred for electromagnetic or gas bubbling and for heating by electric arc light. Therefore, means for performing dephosphorization regeneration of converter waste is shown.

However, these means reduce P ₂ O ₅ contained in the slag by a carbon source, and the P produced by the reduction is transferred to the Fe content in the iron bath or the slag, and thereby the P content in the slag is reduced. P
Although the content is certainly reduced, P does not escape to the outside of the system including the slag and the iron bath or the Fe content in the slag and the slag, and the P content of the entire system does not decrease. Therefore, when P in the slag is recovered in the iron bath, it is necessary to remove P from the iron bath again. Further, when recovering P in slag to Fe content in the slag, when the slag having a reduced P content is recycled for refining, a step of separating the Fe content enriched in P in the slag from the slag, That is, it is necessary to cool, solidify, and pulverize the slag containing the Fe content, and then magnetically separate the Fe content to separate it. Only after the Fe content enriched in P is removed from the slag, the slag can be reused for refining. It becomes possible to recycle. The step of magnetically separating and removing Fe from the slag requires a great deal of cost, and the slag sensible heat is lost in the cooling step before magnetic separation.

As described above, P ₂ O ₅ in the slag is reduced by C, P
If the P content is recovered in the iron bath, it is necessary to remove P (cost) of the bath iron again, and even if the P content is recovered in the Fe content in the slag, Fe
Separation (cost) of P content is required, and both when recovering P content in an iron bath and recovering Fe content in slag, there is a new process cost associated with recovery of P content, and there is almost no profit. Is the actual situation.

The present invention overcomes the above-mentioned drawbacks, efficiently removes P or S component from de-P refined slag generated in the ironmaking and steelmaking processes, and conventionally discards the slag or the ironmaking and steelmaking processes. When it is reused, the slag that causes the recovery P and the recovery S can be reused for de-P refining without causing the recovery P and the recovery S.

(Means for Solving Problems) The inventor has the following means for solving the above problems.

(1) The dephosphorization slag or converter slag generated in the hot metal dephosphorization treatment, converter refining or molten steel dephosphorization refining is left under a molten state or a semi-molten state at the time of generation, and a slag reducing agent such as carbon under reduced pressure. A refining slag reforming method for slag recycling use, characterized in that phosphorus in slag is removed by adding phosphorus to reduce phosphorus oxide and vaporize and dephosphorize it.

(2) The dephosphorization slag or converter slag generated in the hot metal dephosphorization treatment, converter refining or molten steel dephosphorization refining is left in a molten state or a semi-molten state at the time of generation, and a slag reducing agent such as carbon under reduced pressure. And heating by burner heating, arc heating, plasma heating, etc. to reduce phosphorus oxide,
A refining slag reforming method for slag recycling use, characterized in that phosphorus in slag is removed by vaporizing and dephosphorizing.

(3) Desulfurization slag or converter slag generated in hot metal dephosphorization treatment, converter refining or molten steel dephosphorization refining is vaporized and desulfurized by blowing oxygen in the molten state or semi-molten state at the time of generation. Smelting and refining for slag recycling, characterized in that a slag reducing agent such as carbon is added to the slag under reduced pressure to reduce phosphorus oxide and vaporized and dephosphorized to remove sulfur and phosphorus in the slag. Slag reforming method.

Is.

(Operation) In the present invention, vaporization and dephosphorization is performed as a method of removing the P content from the slag after dephosphorization, and the principle thereof will be described below.

P becomes an oxide of P ₂ O ₅ in the slag produced by hot metal dephosphorization, converter refining, and molten steel dephosphorization, and is present as a compound such as 4CaO or P ₂ O ₅ in the form of being combined with CaO. Is added with a reducing agent such as C, P ₂ O ₅ is reduced, has a higher vapor pressure than P ₂ O ₅ , and easily evaporates suboxides (P ₂ O ₃ , PO, P ₂ O ₄ , PO
₂ etc.) or P ₂ , P, P ₄ etc. However, the amount of evaporation is small under atmospheric pressure even in the state of this suboxide or P ₂ , P, P _4, etc., and it is recovered in the granular iron in the slag or Fe produced by reduction from iron oxide. The rate of P is high. If the atmosphere is further evacuated or depressurized in this state, the partial pressure of steam is reduced and evaporation is increased. Also, heating promotes decomposition of the de-P product and vaporization.

The above is the principle of vaporization dephosphorization. In order to industrialize vaporization P removal without returning to P in iron, P _{2 in} slag
In addition to reducing O ₅ with a reducing agent such as C, conditions under reduced pressure or heating + reduced pressure are required.

Next, the S content is removed from the slag after P removal by vaporization S removal. The principle of vaporization S removal is that S ^{2 −} or SO ₄ ^{2− in the} slag is produced by blowing O ₂ into the slag. S ion of SO ₂
It is to vaporize as.

(Examples) The present invention will be described below with reference to the drawings based on examples.

Example 1 FIG. 1 shows that after hot metal dephosphorization, hot metal is tapped into a hot metal ladle, and after de-P treatment, slag 1 is left in the tope car 2 and after de-p treatment, coke powder 3 from lance 4 is used as a reducing agent. Injected with N ₂ gas, mixed well with slag after de-P treatment, heated using plasma 5 as a heat source, and vaporized de-P of slag under reduced pressure by vacuum treatment hood 6.
It is a state diagram which is performing processing. An O ₂ spraying lance 7 is provided for the vaporization / de-S treatment before the vaporization / de-P treatment.
The treatment temperature was 1100 ° C. to 1600 ° C. for both vaporization and de-Ping and de-S, and the depressurization level was 0.2 to 200 torr. It should be noted that FIG. 1 shows the case where the pressure reducing process is also used.

Fig. 2 shows the change in the dephosphorization rate of slag during the treatment and the recovery P rate of slag Fe. As shown in Fig. 2, the removal rate of P varies depending on the presence / absence of decompression treatment. Without decompression treatment, the P removal rate is 80 in 20 minutes
%, But the recovery rate of slag ingots is large 20
It became about 80 times in minutes, and the slag was recycled for de-P refining without removing the metal in this state, but it was reconstituted significantly. When combined with the reduced pressure treatment, a P removal rate of 80% was obtained in about 10 minutes, and the increase of P in the slag ingot was also very small. Note that FIG. 3 also shows an example of the vapor desulfurization treatment by O ₂ spraying performed before the vapor desulfurization.

Example 2 FIG. 4 shows that the converter steel is tapped, and the coal powder 9 is added as a converter slag reducing agent in the ladle 8 after the casting is completed.
It is an example of performing vaporization and dephosphorization landing under reduced pressure by mixing with, heating with an arc 11 as a heat source. Reference numeral 13 in the figure is a bottom blowing porous plug.

 FIG. 5 shows the change in the P removal rate of slag during processing.

(Effects of the Invention) It is possible to extremely efficiently dephosphorize and desulfurize from the dephosphorization slag or converter slag generated in the molten steel dephosphorization refining by the method of the present invention. Therefore, this can be recycled again as refining slag, and its economic effect is extremely large.

[Brief description of drawings]

FIG. 1 is a state diagram of vaporization and dephosphorization treatment of hot metal dephosphorization slag, and FIG.
FIG. 4 is a diagram showing changes in P concentration in slag during vaporization deP treatment of hot metal deoxidized P slag, and FIG. 3 is a diagram showing changes in S concentration in slag during vaporization deS treatment of hot metal deoxidized P slag; FIG. 5 is a diagram showing a state where the dry-furnace slag is vaporized and deP-treated, and FIG. 5 is a diagram showing a change in the P concentration in the slag during the treatment when the dry-furnace slag is vaporized and deP-treated. 1 …… Slag after P treatment 2 …… Topeed car 3 …… Coke powder 4 …… Lance 5 …… Plasma, 6 …… Vacuum exhaust hood 7 …… O ₂ spraying lance, 8 …… Ladle 9 ... … Coal powder, 10 …… Converter slag 11 …… Arc, 12 …… Vacuum tank 13 …… Bottom blowing porous plug

Claims (3)

(57) [Claims] 1. A dephosphorization slag or a converter slag that is generated by hot metal dephosphorization treatment, converter refining or molten steel dephosphorization refining is left under a reduced pressure to remove carbon etc. in a molten state or a semi-molten state at the time of generation. A refining slag reforming method for use in slag recycling, which comprises adding a slag reducing agent to reduce phosphorus oxide, and removing phosphorus in the slag by vaporization and dephosphorization. 2. A dephosphorization slag or a converter slag that is generated in hot metal dephosphorization treatment, converter refining or molten steel dephosphorization refining, in a molten state or a semi-molten state at the time of generation, under reduced pressure to remove carbon etc. Smelting for slag recycling, characterized by adding slag reducing agent and heating by burner heating, arc heating, plasma heating to reduce phosphorus oxide and vaporizing dephosphorization to remove phosphorus in slag Slag reforming method. 3. Desulfurization slag or converter slag generated by molten iron dephosphorization treatment, converter refining or molten steel dephosphorization refining is vaporized and desulfurized by blowing oxygen in the molten state or semi-molten state at the time of generation. After that, a slag reducing agent such as carbon is added to the slag under reduced pressure to reduce phosphorus oxide, and vaporized and dephosphorized to remove sulfur and phosphorus in the slag. Refining slag reforming method.