JPH1060515A - Method for desulfurizing molten iron - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain fuming without reducing desulfurizing efficiency by incorporating a specific ratio of Al together with sode ash into a desulfurizing agent. SOLUTION: At the time of executing the desulfurizing of molten iron by using the desulfurizing agent containing the soda ash, the Al is used together with the soda ash so that the Al quantity of controlled to 5-25mass% to the soda ash quantity. Such a mixed material is added into the molten iron. The adding quantity is made to the same as the conventional method. By this method, the exhaust gas can be prevented from becoming high temp. due to the composition of CO gas by reducing the production of CO gas without coursing any fume. Further, the desulfurizing ratio is obtd, as hereto fore. When the ratio of Al to the soda ash is less than the lower limit of the above mentioned range, the suppression of fuming becomes insufficient. On the other hand, when the ratio is more than the upper limit, the desulfurizing ratio is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a method for desulfurizing hot metal.

[0002]

2. Description of the Related Art As a desulfurizing agent for hot metal, at least one of calcium carbide, soda ash (sodium carbonate: Na ₂ CO ₃ ), and lime-based desulfurizing agent is used alone or in combination. Among them, soda ash is still used constantly since it has a small required amount, does not necessarily need to be blown into hot metal, and can obtain a predetermined desulfurization rate even when it is put.

When hot metal is desulfurized using soda ash as a desulfurizing agent, a considerable desulfurization rate can be obtained in a short period of time. However, smoke generated during the desulfurization treatment due to the desulfurizing agent is remarkable, and the working environment is deteriorated. It is known to be significant.

[0004] As a technique for suppressing such smoke emission, it is known to mix soda ash with quick lime.
Japanese Patent Application Laid-Open No. 49-123111 describes mixing soda ash and calcium carbonate, and Japanese Patent Application Laid-Open No. 49-13016 discloses that hot lime or magnesium oxide is impregnated with soda ash by heating.

[0005] These smoke suppression techniques are intended to reduce the proportion of soda ash in the desulfurizing agent by mixing substances such as quick lime at a certain ratio, thereby suppressing smoke formation.

However, in these smoke suppression technologies, the amount of soda ash per unit of desulfurizing agent is reduced, so that the desulfurization rate is lower when the amount of desulfurizing agent is the same than when no substance such as quicklime is mixed. When the desulfurization rate is lowered and the same desulfurization rate is to be obtained, the required amount of the desulfurizing agent increases, and therefore, there is a problem that the desulfurization treatment time is extended and the cost is increased. In addition, the technology described in Japanese Patent Application Laid-Open No. 49-13016 also has a problem that, in addition to the above-mentioned problems, a heat impregnation process is required during the production of a desulfurizing agent, which leads to an increase in the desulfurizing agent production process and production costs. There are points.

Further, as in the case where soda ash is not mixed with a substance such as quick lime, a large amount of CO gas is generated by the desulfurization reaction, which is burned by oxygen in the atmosphere to become high-temperature exhaust gas. In addition to the necessity of an excessively large cooling facility, there is also a problem that a dust collector or the like requires some consideration.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has as its object to solve the problems of the prior art and to use a desulfurizing agent containing soda ash. When desulfurizing hot metal, it is possible to suppress the generation of smoke without lowering the desulfurization rate and to reduce the amount of generated CO gas, thereby suppressing the high temperature of exhaust gas due to the combustion of CO gas. It is an object of the present invention to provide a method for desulfurizing hot metal that can be produced.

[0009]

Means for Solving the Problems To achieve the above object, a method for desulfurizing hot metal according to the present invention is a method for desulfurizing hot metal according to claims 1 and 2, which has the following configuration. Things.

That is, the method of desulfurizing hot metal according to claim 1 is
When desulfurizing hot metal using a desulfurizing agent containing soda ash, Al is present together with soda ash, and the amount of this Al is set to 5 to 25% by mass with respect to the amount of soda ash. It is a desulfurization method.

The method for desulfurizing hot metal according to claim 2 is characterized in that:
2. The method for desulfurizing hot metal according to claim 1, wherein the amount of the hot metal is 10 to 25% by mass.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is implemented, for example, as follows. Soda ash (Na ₂ CO ₃ ) and granular or powdered Al
(Aluminum) and the amount of Al is 5
-25% by mass, for example 15%, and the mixture is placed in a hopper. Then, this mixture is added from a hopper to hot metal, for example, hot metal after tapping from a blast furnace. At this time, the amount of the mixture added was Al to soda ash as a desulfurizing agent.
Is the same as in the case where a material not mixed with is used.

Then, no smoke is generated, and
Without causing high temperature of exhaust gas by combustion of CO gas,
A desulfurization treatment can be performed, and a desulfurization rate similar to that in the case where a soda ash that does not mix Al is used as a desulfurizing agent is obtained.

As can be seen from the embodiments of the present invention, according to the present invention, when desulfurizing hot metal using a desulfurizing agent containing soda ash, the desulfurization rate does not decrease, and
Smoke emission can be suppressed, and the amount of generated CO gas can be reduced, and the temperature rise of exhaust gas due to the combustion of CO gas can be suppressed.

The details will be described below.

When hot metal is desulfurized using soda ash (without mixing of Al) as a desulfurizing agent, the desulfurization reaction by soda ash is represented by the following equations (1), (2), (3) and (4). And desulfurized by such a reaction. In these equations, [S],
[O] and [C] indicate S, O and C in the hot metal. g
Is a gas.

Na ₂ CO ₃ = Na ₂ O + CO ₂ (g) ---- (1) Na ₂ O + [S] = Na ₂ S + [O] ---- (2) CO ₂ (g ) + [C] = 2CO (g) ---- (3) [O] + [C] = CO (g) ---- (4)

However, not all soda ash added to the hot metal participates in the desulfurization reaction as shown in the above formula, and soda ash other than the soda ash that has contributed to the desulfurization reaction is heated to a high temperature by the molten iron to evaporate. Or hot metal surface (hot water surface)
Involved in the formation of slag. At this time, Na ₂ CO ₃ and Na ₂ C
Na ₂ O produced by the decomposition of O ₃ is carbon in hot metal ([C])
Is known to produce fuming, and this reaction is represented by the following formulas (5) and (6). That is, as can be seen from this reaction equation, the fumes that cause the deterioration of the working environment are generated by reducing the soda ash with carbon in the hot metal to form CO gas [: C
O (g)], and Na gas generated by the reduction of Na ₂ O by the carbon in the hot metal (: Na (g))
And CO (g).

Na ₂ CO ₃ + [C] = Na ₂ O + 2CO (g) ---- (5) Na ₂ O + [C] = 2Na (g) + CO (g) ---- (6 )

Therefore, it is considered that if the generation of CO (g) and Na (g) can be suppressed, the generation of smoke should be suppressed.

Therefore, intensive research was conducted to find a method capable of suppressing the generation of CO (g) and Na (g) without lowering the desulfurization rate. As a result, Al exists together with soda ash, and the amount of this Al is set to 5 to 25% by mass with respect to the amount of soda ash, without lowering the desulfurization rate.
It has been found that the generation of CO (g) can be suppressed, thereby suppressing the generation of smoke.

That is, according to various research experiments, the coexistence of Al in soda ash causes a reaction represented by the following formulas (7) and (8). The progress of the reaction of the formulas (5) and (6), which is the cause, is hindered, so that although Na (g) is generated, generation of CO (g) is suppressed, thereby suppressing smoke generation. all right. And by making the amount of Al coexisting in soda ash at this time 5 mass% or more with respect to the amount of soda ash,
It was found that fuming could be sufficiently suppressed.

3Na ₂ CO ₃ +4 [Al] = 3Na ₂ O + 2Al ₂ O ₃ + [C] ---- (7) 3Na ₂ O + 2 [Al] = 6Na (g) + Al ₂ O ₃ ---- (8 )

It is feared that the coexistence of Al with soda ash reduces the amount of soda ash per unit desulfurizing agent, thereby lowering the desulfurization rate. However, Al has a strong affinity for oxygen and has a high oxygen affinity. Easily reacts with the oxygen in the hot metal ([O])
To form Al ₂ O ₃ , thereby reducing the concentration of [O], so that the desulfurization reaction of the above formula (2) proceeds easily. Therefore, if the amount of Al coexisting in soda ash is too large, the desulfurization rate will be reduced. It was found that the same desulfurization rate as in the case of using the same was obtained.

Further, as described above, the progress of the reaction of the formulas (5) and (6) is hindered, and the generation of CO (g) is suppressed. It was also found that it was possible to lower the exhaust gas temperature.

The present invention has been completed based on the above findings, and has the above-described configuration. That is,
The method for desulfurizing hot metal according to the present invention, when performing desulfurization of hot metal using a desulfurizing agent containing soda ash, Al is present together with soda ash, and the amount of this Al is 5 to 25 mass with respect to the amount of soda ash. %. Therefore, according to the method for desulfurizing hot metal according to the present invention, when performing desulfurization of hot metal using a desulfurizing agent containing soda ash, without causing a decrease in desulfurization rate,
Smoke emission can be suppressed, and the amount of generated CO gas can be reduced, and the temperature rise of exhaust gas due to the combustion of CO gas can be suppressed. Accordingly, the working environment can be improved without lowering the desulfurization rate, and the exhaust gas system and the dust collector can be simplified.

As described above, the reactions of the formulas (7) and (8) proceed, and the progress of the reactions of the formulas (5) and (6) are hindered.
The reaction of (8) is an oxidation reaction of Al, and the reactions of Formulas (5) and (6) are oxidation reactions of carbon.Since the heat of oxidation of Al is larger than the heat of oxidation of carbon, The effect that the temperature of the hot metal during the treatment is hard to lower and the lowering of the hot metal temperature can be suppressed can be obtained.

Here, the reason why the amount of Al coexisting in soda ash is set to 5 to 25% by mass with respect to the amount of soda ash is that if it is less than 5% by mass, smoke cannot be sufficiently suppressed. If the content is more than 25% by mass, the desulfurization rate is lower than in the case of using no Al mixture, and the desulfurization rate is reduced, resulting in an insufficient desulfurization rate.

As described above, Al is present together with soda ash,
By setting the amount of Al to 5 to 25% by mass with respect to the amount of soda ash, the amount of soda ash or a soda ash-containing agent (containing soda ash and a substance other than soda ash) and Al is reduced to an amount of soda. Adding to the hot metal a mixture preliminarily mixed so as to be 5 to 25% by mass with respect to the amount of ash, or adding soda ash or a soda ash-containing agent and Al to the soda ash in the hot metal after the addition. By separately adding to the hot metal so that it becomes 5 to 25% by mass with respect to the amount of In any case, it is important that soda ash and Al coexist in the hot metal part requiring desulfurization, and that the amount of Al be 5 to 25% by mass with respect to the amount of soda ash.

It is desirable that the amount of Al coexisting in the soda ash is 10 to 25% by mass based on the amount of soda ash (the method of desulfurizing hot metal according to claim 2). Then, smoke can be more remarkably suppressed.

When the amount (%) of Al coexisting in soda ash with respect to the amount of soda ash is expressed as an A / N (%) value, this is A / N (%) = (Al coexisting in Na ₂ CO ₃ ). Amount / Na ₂ CO ₃
Amount) x 100 When soda ash or a soda ash-containing agent is preliminarily mixed with Al to form a mixture, A / N (%) = [amount of Al in mixture (%) / amount of Na ₂ CO _{3 in} mixture (%)] It can also be obtained by the formula × 100.

The present invention can be applied to desulfurization of any hot metal.

[0033]

EXAMPLES Example 1 A mixture (desulfurizing agent) of soda ash (sodium carbonate: Na ₂ CO ₃ ) and granular or powdered Al is put in a hopper. Then, the hot metal was poured into the ladle from the blast furnace, and the desulfurizing agent was charged into the ladle from the hopper. That is, the desulfurizing agent was poured into the ladle together with the hot metal after tapping from the blast furnace, and the hot metal in the ladle was desulfurized. Then, the state of smoke emission during the desulfurization treatment was observed, and the amount of sulfur ([S]) in the hot metal before and after the desulfurization treatment was analyzed to determine the desulfurization rate from the following equation (9).

Desulfurization rate (%) = [([S] amount before desulfurization treatment− [S] amount after desulfurization treatment) / [S] amount before desulfurization treatment] × 100 ---- (9)

The desulfurization treatment was carried out with the composition, temperature, and amount of hot metal poured into the ladle constant, and changing the ratio of the amount of Al to the amount of soda ash in the desulfurizing agent as a parameter. That is, [C] = 3.5-3.8% and [S] = 0.00 as hot metal.
The temperature of the hot metal at the time of pouring into the ladle is 1260 to 1320 ° C, and the amount of hot metal into the ladle is 3 to 0.008%.
The ratio was set to 200 to 250 tons (tons) and kept constant for each desulfurization treatment. However, the ratio of the amount of Al to the amount of soda ash of the desulfurizing agent charged into the ladle [A / N (%) value] is shown in the table. It was changed as shown in FIG.

Table 1 shows the smoke generation status and desulfurization rate during these desulfurization treatments. In addition, the smoke generation state was defined as the smoke generation state when using only a soda ash (A / N (%) value = 0) as a desulfurizing agent without mixing Al, and almost no smoke was observed. If the degree of smoking is extremely small or no smoking is observed, it is referred to as small smoke.The level of smoke is larger than that of small smoke, but smaller than large smoke, The case is indicated as smoking (the same applies hereinafter).

As can be seen from Table 1, the desulfurizing agent (soda ash and
(A / N (%) value) with a soda ash amount (A / N (%) value) of 5% as a mixture with Al) (No.
4) Smoke emission is suppressed to the level during smoke emission, and if the A / N (%) value used is 11%, 18% or 25% (No. 5, 6, 7), the smoke emission status Is suppressed to a small extent. Moreover, in these cases, the desulfurization rate is determined by using a desulfurizing agent having an A / N (%) value of 0 (No. 1 to No. 1).
It is at the same level as 3) and does not cause a decrease in desulfurization rate. However, when an A / N (%) value of 33% was used (No.
8) Although the smoke generation is suppressed to a small degree, the decrease in desulfurization rate is observed.

(Example 2) As a desulfurizing agent to be poured into a ladle together with hot metal after tapping from a blast furnace, a mixture of soda ash, lime, granular or powdered Al in the ratio shown in Table 2 was used. Except for this point, the hot metal in the ladle was desulfurized in the same manner as in Example 1, the smoke generation status was observed, and the desulfurization rate was determined.

Table 2 shows the results. As can be seen from Table 2, a mixture of soda ash and lime [A / N
(% Value = 0) (Nos. 1 to 2), the smoking status is the level during the smoking. On the other hand, it is a mixture of soda ash, lime, and Al as a desulfurizing agent, and the A / N (%) value is
When 11% and 25% were used (Nos. 3 and 4), the smoke generation was suppressed to a small degree, and the desulfurization rate was at the same level, and the desulfurization rate did not decrease. However, A / N
When the (%) value used was 43% (No. 5), although the smoke emission was suppressed to a small extent, the reduction of the desulfurization rate was observed.

Example 3 FIG. 1 shows a diagram obtained by rearranging the data of Tables 1 and 2 using the A / N (%) value as an index. That is, the A / N (%) value, desulfurization rate and smoke generation status (degree of smoke generation) obtained using the data of Tables 1 and 2.
1 is shown in FIG.

As described above, when the A / N (%) value is arranged as an index, the case where the desulfurizing agent does not contain lime (Table 1) and the case where the desulfurizing agent contains lime (Table 2) are the same as the A / N (%) value. It became possible to evaluate with the index of. As a result, A / N
It can be seen that when the (%) value is 5% or more, the effect of suppressing smoke is obtained, and when the A / N (%) value is 10% or more, the effect of suppressing smoke becomes remarkable. But,
When the A / N (%) value exceeds 25%, the effect of suppressing smoke emission is remarkable, but the desulfurization rate decreases. As described above, when the A / N (%) value is 5 to 25%, it is possible to suppress the generation of smoke without lowering the desulfurization rate, and to further reduce the A / N (%) value to 10%.
It was confirmed that the smoke generation can be more remarkably suppressed by setting to 2525%.

[0042]

[Table 1]

[0043]

[Table 2]

[0044]

According to the method for desulfurizing hot metal according to the present invention,
When desulfurizing hot metal using a desulfurizing agent containing soda ash, smoke can be suppressed without lowering the desulfurization rate, and the amount of generated CO gas can be reduced to reduce CO gas combustion. High temperature of exhaust gas can be suppressed. Accordingly, the working environment can be improved without lowering the desulfurization rate, and the exhaust gas system and the dust collector can be simplified. Furthermore, the effect that the temperature fall of the hot metal during the desulfurization treatment can be suppressed can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between A / N (%) and a desulfurization rate (%) according to an example.

Claims (2)

[Claims] When desulfurizing hot metal using a desulfurizing agent containing soda ash, Al is present together with soda ash.
The desulfurization method for hot metal, wherein the amount of the molten iron is 5 to 25% by mass based on the amount of soda ash. 2. The hot metal desulfurization method according to claim 1, wherein the amount of Al is set to 10 to 25% by mass.