KR840001170B1 - Injection desulfurzizing agent - Google Patents

Abstract

Desulphurizing agent for injecion consists of lime powders having a particle dia. that allows at least 50 wt.% of the lime powders to pass through a screen mesh of 100 microns, and contains 0.015-1 wt.% of silicone oil surfactant, 10-40 wt.% of carbonate of alkaline earth metals, and 2-20 wt.% C. Pref. the agent additionally contains 2-10 wt.% alkali metal fluoride, cryolite and/or Na silicofluoride. Pref. the carbonate is CaCO used as a gas-generating substance. The agent exhibits a high reaction efficiency when injectted into hot metal.

Description

Blowing Desulfurizer

1 is a graph showing the effect of the silicone oil-based surfactant, methylhydrogen polysiloxane, added to two kinds of quicklime powders having different particle sizes on the angle of rest,

2 is a graph showing the relationship between CaCO ₃ content and desulfurization of a desulfurization agent composed of CaO-CaCO ₃ -10% C-0.05% methyl hydrogen polysiloxane,

3 is a graph showing the relationship between the C content of the desulfurization agent composed of CaO-25% and CaCO ₃ -C-0.05 methyl hydrogen polysiloxane and the desulfurization rate,

4 is a graph showing the relationship between the quicklime particle size and the desulfurization rate of the desulfurization agent according to the present invention, which is composed of CaO-25% CaCO ₃ -10% -0.015 to 0.4% methyl hydrogen polysiloxane.

5 is a graph showing the relationship between the amount of desulfurization agent CaF ₂ (fluorite) added according to the present invention and the desulfurization rate, which is composed of CaO-25% CaCO ₃ -10% C-CaF ₂ -0.05% methyl hydrogen polysiloxane being.

The present invention relates to a blowing desulfurizing agent suitable for hot metal desulfurization treatment.

Recently, good quality steel has been strongly demanded. In particular, if the steel contains sulfur, the mechanical properties of the steel material is significantly degraded, so it is preferable to lower the sulfur content of the steel.

In order to meet these requirements, it has been common to carry out desulfurization in the molten iron phase.

Desulfurization agents suitable for desulfurization of molten iron have been studied for a long time, but at present, calcium carbide (CaC ₂ ) is removed due to the high reaction efficiency of the desulfurization agent and the relatively easy removal of slag after desulfurization treatment. Desulfurization agents, the main component of which has been widely used.

However, calcium carbide is disadvantageous because it consumes a large amount of power in the manufacturing process and is expensive and there is a risk of generating acetylene gas during handling. In addition, there are soda, such as sodium carbonate, as a low-cost desulfurization agent, but since these soda tend to generate white smoke during desulfurization treatment, there is a problem in terms of workability, as well as a built-in desulfurization vessel. It is not widely used because of the drawbacks such as increased melting loss of the refractory.

In addition, quicklime has been tried to be used as a desulfurization agent for a long time because it is known that it is considerably inexpensive and has a desulfurization ability, compared to carbide and soda, but desulfurization is slow, although there are no disadvantages such as the generation of acetylene and white smoke. Had a serious flaw.

Therefore, during desulfurization, it is necessary to add a large amount of quicklime in order to obtain a high desulfurization rate.In addition, although a large amount of quicklime is used, the desulfurization unit costs much lower than carbide and soda, even though the desulfurization unit cost is low. Due to problems such as slag due to the temperature drop and the amount of molten iron loss due to the slag, quicklime is less practical.

Many methods have been studied for practical use of the desulfurization method of molten iron, and in recent years, a method of blowing a desulfurizing agent together with a carrier gas through a lance in a molten iron in a torpedo car has been frequently used.

This method has the advantage of processing a large amount of molten iron in a short time, but since the sulfur desulfurization occurs only in a very short time from when the desulfurization agent is blown to the hot metal bath, a desulfurization agent having high anti-reflection rate is used. It is necessary to use it, and the quicklime which has a slow reflection rate is especially unsuitable as a blowing desulfurization agent. However, quicklime has been reevaluated as a useful desulphurizer because of its low cost, easy handling, and low risk.

As a method of improving the anti-melt efficiency of quicklime used in blown desulfurization, a method of improving the anti-melt size of quicklime to increase the antisolvent area with molten iron or adding a small amount of fluorite to make part of quicklime low melting point composition Has been proposed.

In order to investigate the effect of the above-mentioned proposal, the inventors carried out an experiment in which nitrogen was used as a carrier gas, and a quicklime desulfurizing agent which changed the particle size and fluorite content of the quicklime powder was blown into the molten iron in the topido car.

As a result, the desulfurization efficiency of quicklime varies slightly in the size of the quicklime or in the content of fluorspar. Since the amount of change is small, the increase in the price due to the incorporation of expensive fluorspar compared to the grinding cost and quicklime required to make the grain size finer In view of the above, it has been found that favorable conditions cannot be found.

In addition, although a desulfurization agent based on quicklime having a low calcining degree of lime and having 1 to 15% of CaCo ₃ remaining therein has been proposed, according to the inventors' investigation, the quicklime having a low calcining degree is a blown desulfurizing agent. When used as a desulfurization effect was lower than that of calcined well calcined.

Accordingly, an object of the present invention is to provide a quicklime desulfurization agent having excellent desulfurization ability with high anti-solvent efficiency even when used for blowing desulfurization.

The present invention is characterized by having a quick-drying lime powder having a particle size that can pass at least 50% by weight or more of a screen mesh of 100 µm, including 0.015 to 1.0% by weight of a silicone oil-based surfactant and 10 to 10 carbonates or hydroxides of alkaline earth metals. It is to provide a blowing desulfurization agent composed of 40% by weight and 2 to 20% by weight of carbon.

In addition, the above-mentioned desulfurization agent according to the present invention may be blended with one or more selected from fluoride, cryolite and sodium silica fluoride of 2-10 wt% of alkali metal or alkaline earth metal, if necessary.

Due to the poor flowability of the quicklime, it is more dense than carbide, so when blowing desulfurization, less antagonist gas is used and the lance is cloged, and the quicklime causes a large aneurysm. It is a defect such as being.

This drawback can be eliminated by increasing the carrier gas to about 70 liters per kilogram of desulfurizer. When the carrier gas is increased in this way, even though blowing of quicklime is possible, the amount of molten iron scattered at the time of blowing the quicklime powder increases. In addition, when the amount of carrier gas is large, the upflow velocity of the molten iron is significantly increased, and the blown desulfurizing agent floats in the bath in a very short time. Moreover, even slower desulfurization reactions do not yield satisfactory desulfurization effects.

Therefore, the present inventors have conducted various experiments and studies in order to solve the above-mentioned drawbacks. As a result, silicone oil treatment improves the fluidity of quicklime powder and increases the ratio of solid (desulfurizer) to gas (carriage gas). At the same time, it has succeeded in developing a blow desulfurization agent which is low in cost and high in desulfurization effect by adding an appropriate amount of an appropriate additive.

The fluidity change when a small amount of the silicone oil-based surfactant is added to the quicklime powder is shown in FIG.

FIG. 1 shows two kinds of quicklime, in which methyl hydrogen polysiloxane, which is one kind of silicone oil, is uniformly added to two kinds of 2 μm and 75 μm quicklime powder having a particle size D ₅₀ that can pass 50% by weight of quicklime powder. The standard of fluidity for powders is the result of measuring the residual angle.

Residual angle is drastically reduced by the addition of a small amount of methyl hydrogen polysiloxane from FIG. 1, and the flowability of the quicklime powder is remarkably improved, so that the addition of a small amount of carrier gas of about 10 liters per kg of the desulfurizing agent enables the blowing of the desulfurizing agent. You can see

In this case, the surfactant is preferably added so that the remaining angle is about 40 ° or less, and the required amount depends on the particle size of the quicklime powder, but at least when the particle size of the quicklime powder is within the range specified by the present invention. 0.015% by weight of surfactants must be used. The upper limit of the amount added is not limited in terms of improving the flowability of quicklime, but is preferably 1% viscosity from an economic point of view.

145 mesh in Japanese Industrial Standard JIS Z 8801 refers to the size of the mesh having a 105 μm opening, and 140 mesh in the US standard ASTME refers to the size of the mesh having a 105 μm opening, and the British standard 150 mesh in BS 410 refers to the size of the network with a 104 μm opening, and 150 mesh in the US Tyler standard refers to the size of the network with a 104 μm screen opening.

The present inventors conducted various research experiments on the desulfurization effect of the quicklime desulfurization agent which improved the fluidity by surfactant treatment, and the hydroxide and fish coke of alkaline earth metal such as CaCO ₃ or alkaline earth metal such as Mg (OH) _2. , Oil coke, smoking, electrode chips, anthracite, charcoal, and other carbons significantly improve the desulfurization effect, and CaF ₂ , NaF, MgF ₂ , ice crystals (Na ₃ AlF ₆ ), sodium silica fluoride (Na It was found that adding fluoride such as ₂ SiF ₆ ) stabilized at the same time as the desulfurization effect was improved.

The mechanism by which these substances are added to improve the desulfurization effect of quicklime has not yet been elucidated, but it has been found that the desired purpose can be achieved in the composition range as described in detail later.

Conventionally, it has been thought that it is desirable to reduce the oxygen potential of the carrier gas as low as possible for the use of quicklime for blow desulfurization, because the oxygen in the carrier gas is incompatible with Si in the snow melting tank and the surface of the quicklime It was thought that the reaction rate was slowed down by producing SiO ₂ which tends to cover the. Therefore, in some cases, natural gas is used as the carrier gas to reduce the oxygen potential. Alkaline metal carbonates and hydroxides, such as CaCO ₃ and Mg (OH) ₃ , generate CO ₂ and H ₂ O in molten iron, which is expected to produce SiO ₂ by incompatible with Si as in oxygen. Desulfurization agents rarely mix these substances. Nevertheless, in the present invention, the desulfurization effect of quicklime is improved by mixing CaCO ₃ and Mg (OH) ₂ and the like, which is a significant result.

However, in order to obtain the above-mentioned effect, fluorides such as alkali carbonate or hydroxide and carbon, and Ca ₂ F ₂ , Nae, MgF ₂ , Na ₃ AlF ₆ , Na ₂ SiF _6, and the like are simply added to quicklime. By adding only, the desired effect cannot be obtained, and each condition of an appropriate mixing ratio and quicklime particle size must be satisfied, and the fluidity must be improved by surfactant treatment.

Next, these conditions will be described, and FIGS. 2 to 4 show the results obtained by blowing 6 kg per tonne of molten iron into a 200 to 300 tonne of molten iron in which the sulfur concentration was maintained at about 0.040% before the desulfurization treatment. .

A second turning CaCO ₃ or Mg (OH) by showing the relationship between the content and the desulfurization rate in the desulfurizing agent with respect to the gas generating material in the _second place, the curve in Figure 2 a is a satisfactorily calcined calcium oxide minutes (CaO) and limestone The desulfurization agent composed of CaO-CaCO ₃ -10% C-0.05% prepared by mixing with powder (CaCO ₃ ) and carbon powder shows the case where the CaCO ₃ content is changed in the range of 3 to 45%. Xb is a case in which a desulfurization agent composed of quicklime containing 15% CaCO ₃ and CaO-15% CaCO ₃ -10% C-0.05% mixed with carbon is blown in the second degree. It can be seen that the desulfurization rate is lower than the curve a in the case shown by xb.

In the curve a of FIG. 2, when the CaCO ₃ content is less than 10%, the desulfurization rate is lowered because the amount of gas generated by the decomposition of CaCO ₃ is insufficient. On the other hand, when the CaCO ₃ content is more than 40%, there is little desulfurization power. Since the ratio of CaCO ₃ becomes large and the desulfurization rate becomes low, the suitable addition amount of CaCO ₃ is 10 to 40%, and especially when CaCO ₃ is used, it is necessary to mix it with the calcined quicklime separately. In addition, it has been found that, even for carbonates or hydroxides of other alkaline earth metals, excellent desulfurization effects are provided only within the range of 10 to 40%.

3 shows the relationship between the content of the desulfurization agent and the desulfurization rate with respect to carbon, and it is not clear why the desulfurization rate is increased as the carbon content is increased, but the action of reducing the atmosphere and reducing the CaCO ₃ and Mg It can be considered that the amount of generated gas is increased by reacting with CO ₂ and H ₂ O generated from (OH) ₂ and the like as described in the following formulas (1) and (2).

CO ₂ + C → 2CO (1)

H ₂ O + C → H ₂ + CO (2)

At this time, when the carbon content is 2% or less, the desulfurization rate is lowered because the above-described action is not sufficiently exhibited. On the other hand, when the carbon content is more than 20%, the desulfurization rate is rapidly decreased because carbon itself has no desulfurization power. . Therefore, the carbon content is preferably in the range of 2 to 20%.

As described above, as the desulfurizing agent composition, it is preferable to mix 10-40% of the gas generating substance and 2-20% of carbon in addition to the main component quicklime, but even if the composition is in such a range, the desulfurization rate decreases if the particle size of the quicklime is coarse. This relationship is shown in FIG. 4, and when the particle size D ₅₀ of quicklime, through which 50% by weight of quicklime passes, exceeds 100 µm, the contact area between the quicklime and the molten iron is reduced, so that the desulfurization rate is increased. It will be lowered.

Therefore, in order to improve the desulfurization capacity, the particle size D ₅₀ of quicklime must be 100 µm or less.

As described above, the quicklime powder particle size D ₅₀ through which 50% by weight quicklime can pass is mainly composed of quicklime of 100 μm or less, and 10 to 40% of carbonates or hydroxides of alkaline earth metals and 2 to 20%. It is understood that a blowing desulfurizing agent having a significantly high desulfurization effect can be obtained by mixing carbons and adding only 0.015 to 1.0% of a silicone oil-based surfactant.

The present inventors also found that the addition of 2-10% alkali metal or alkali metal fluoride such as CaF ₂ , NaF, MgF ₂ , cryolite or sodium silica fluoride significantly stabilizes the desulfurization rate. I also found the facts.

FIG. 5 shows the fluctuation of fluorspar addition and desulfurization rate. It can be seen from FIG. 5 that the fluctuation of the desulfurization rate can be reduced by adding 2 to 10% of CaF ₂ to the quicklime.

If the desulfurization rate is large, the sulfur concentration after the desulfurization treatment is too low, resulting in excessive use of the desulfurization agent, or the sulfur concentration is too high, which leads to an increase in the desulfurization cost. Therefore, it is very beneficial to stabilize the desulfurization rate by the addition of the above-mentioned fluoride, and the desulfurization rate itself has an effect of increasing about 2-3%.

To achieve these effects, 2% or more must be added. However, when the amount of fluoride is more than 10, the amount of fluoride added is 2 to 10 because it not only improves the desulfurization rate but also reduces the stabilizing effect. It should be in the range of%.

Below, the Example using the desulfurization agent of the preferable composition range which concerns on this invention is described in detail, comparing with the comparative example using the desulfurization agent outside this composition range.

[Examples 1 to 8 and Comparative Examples 9 to 15]

The desulfurization agent composition, quicklime density, the presence or absence of silicone oil treatment, and the amount of carrier gas per kg of desulfurization agent in these Examples and Comparative Examples are as described in Table 1 below, and in these examples, nitrogen gas was used as the carrier gas. The desulfurizing agent of was blown into the molten iron of 200 to 300 tons, and the amount of the desulfurizing agent used was 6 kg per ton of molten iron in all examples and comparative examples.

[Table 1]

The molten iron was subjected to desulfurization treatment under the conditions described in Table 1 above, and the fluctuations in sulfur concentration, desulfurization agent and desulfurization rate before and after the desulfurization treatment thus obtained were measured, and the results are shown in Table 2.

[Table 2]

As can be seen from the first table, No. which does not use silicone oil. In Comparative Examples 14 and 15, a carrier gas of 70 L / kg was required to prevent the lance membrane force. Particularly, in Comparative Example 15, since gas generation in CaCO ₃ was aggravated, scattering was severe and molten iron flowed out from the exit of Topido Ka.

From Table 2, when CaCO ₃ or carbon content in Comparative Examples 9, 10, 11 and 12 is outside the preferred range according to the present invention and when the particle size of CaO in Comparative Example 13 is larger than the preferred particle size according to the present invention It can be seen that the desulfurization rate is low and the fluctuation of the desulfurization rate is large.

On the contrary, it can be seen from the second table that the desulfurization agent according to the present invention can obtain a significantly higher desulfurization rate than the comparative example. In particular, as in Examples 4 to 8, CaF ₂ , NaF, MgF ₂ , Na By adding fluorides such as ₃ AlF ₆ and NaSiF ₆ , the fluctuation in the desulfurization rate can be further reduced, which is advantageous for performing a stable desulfurization treatment. Moreover, the desulfurization agent which concerns on this invention can also be used for the desulfurization of molten iron in oxygen blowing in a conversion furnace, or molten steel after oxygen blowing.

As described above, according to the present invention, a low cost quicklime desulfurization agent can be used for blow desulfurization treatment for molten iron in topido cara or ladle, and the desulfurization cost can be greatly reduced.

In addition, the desulfurization agent according to the present invention is easy to handle, and there are no safety and hygiene problems such as generation of acetylene gas in the carbide-based desulfurization agent and white smoke generation in the soda-type desulfurization agent.

Claims (1)

It is composed mainly of quicklime powder having a particle size that can pass at least 50% by weight of 100 μm screen mesh, and it contains 0.015 to 1.0% by weight of silicone oil-based surfactant and 10 to 40% by weight of carbonate or hydroxide of alkaline earth metal and carbon 2 Blowing desulfurization agent, characterized in that the composition to 20% by weight.

Images