KR100834548B1 - Manufacturing method of briquette containing mill scale - Google Patents

Abstract

The present invention relates to a method for producing briquettes containing mill scales, and more particularly, briquettes that can be used as an alternative iron source in the steelmaking process, containing mill scales and additives suitable for reducing the mill scales, and having high strength. A method of making briquettes.

One aspect of the present invention is briquette is an inorganic binder per 100 parts by weight of the briquette main component and the briquette main component consisting of 5 to 10% by weight of reducing agent, 25 to 40% by weight of electric furnace or steelmaking dust and 50 to 70% by weight of mill scale. 2 to 10 parts by weight of the organic binder and 2 to 10 parts by weight of the organic binder, characterized in that obtained by pressing.

In another aspect of the present invention, a manufacturing method for producing a briquette containing a mill scale includes a briquette consisting of 5 to 10 wt% of a reducing agent, 25 to 40 wt% of an electric furnace or steelmaking dust, and 50 to 70 wt% of a mill scale. Preparing and mixing 2-10 parts by weight of an inorganic binder and 2-10 parts by weight of an organic binder per 100 parts by weight of the main component and the briquette main component; Pressure molding the mixture formed in the mixing step to process briquette shapes; And curing the workpiece in the form of briquettes.

Mill scale, briquettes, recycling, iron recovery, high strength

Description

Briquettes containing mill scale and manufacturing method thereof {MANUFACTURING METHOD OF BRIQUETTE CONTAINING MILL SCALE}

The present invention relates to a method for producing briquettes containing mill scales, and more particularly, briquettes that can be used as an alternative iron source in the steelmaking process, containing mill scales and additives suitable for reducing the mill scales, and having high strength. A method of making briquettes.

The steelmaking process refers to a process of manufacturing iron or steel using iron ore or scrap iron as a main raw material containing a large amount of iron.

Iron ore is manufactured from pig iron through a process such as blast furnace, Corex or Finex, then cast directly or made into semi-finished products such as billets, blooms or slabs through the steelmaking stage. It is made into semi-finished products such as billets, blooms or slabs through an additional steelmaking step.

Most of the semi-finished products do not have the form required by the end customer, and thus are subjected to a rolling step to be processed into the form required by the end customer. The rolling usually consists of a hot rolling process for greatly reducing the diameter or thickness of these semi-finished products and a cold rolling process for additional physical properties and dimensional control. In the hot rolling process, since the dimensions of the semi-finished products are drastically reduced, a large strain is required, and accordingly, it is necessary to maintain the high temperature of the semi-finished products through a process of heating the semi-finished products at a high temperature or directly transferring them in a hot semi-finished state. At this time, the surface of the semi-finished product can easily occur the oxidation reaction of oxygen and steel due to the high temperature. As a result of this oxidation, scales form on the surface of semi-finished products such as slabs, blooms and billets.

Such scales are removed by the rolling process, and since they contain a large amount of iron, they may cause waste of resources and environmental pollution if they are disposed of as it is, and efforts to recycle them as alternatives to iron sources have been conventionally made. Has been implemented.

In order to recycle the mill scale, it is necessary to understand the properties of the mill scale. The mill scale forms a brittle oxide layer as the surface of the semifinished product is oxidized, and is finely crushed and removed from the semifinished product when stress is applied due to the brittle nature of the oxide layer. Therefore, the mill scale is present in a part oxidized state, and includes components such as Fe, FeO, Fe ₂ O ₃ , Fe ₃ O ₄ , the average oxidation degree of these components is hematite (many iron used as iron source) Fe ₂ O ₃ ) is lower than the lower oxide level. Therefore, in order to use the mill scale as an iron source, it is necessary to add an additive under conditions suitable for reducing the lower oxide.

In addition, the mill scale is advantageous to iron recovery in the reaction vessel, such as steelmaking process, when the mill scale is put into the powder form as it is collected in the form of powdery raw material due to the strong rising air formed on the reaction vessel Many of them may be lost.

Therefore, it is preferable to agglomerate and inject | aggregate the said mill scale in block form so that it may have sufficient strength.

In response to this demand, Korean Patent Laid-Open Publication No. 2003-90803 discloses a method and a facility using wastes containing hydrocarbons and iron oxides, particularly mill scale sludge and pulverized coal.

Korean Patent Laid-Open Publication No. 2003-90803 discloses agglomerates having ultrafine coal 40-40% by weight, roll scale sludge about 30-50%, metallurgical dust about 10-15%, and binder 2-5%. . The aggregates make it possible to utilize mill scales as iron sources.

However, the Republic of Korea Patent Publication No. 2003-90803 uses a bitumen or bitumen emulsion as a binding agent having a strong binding force between the oil is not removed from the rolling sludge, such as rolling oil and the like contained in the rolled sludge, all these are pollution sources such as molten steel There is a problem that can work. In addition, in order to use the waste containing the rolled sludge in the steelmaking process, the content of the ultra fine coal serving as a reducing agent needs to be as high as 40 to 70%, so the content of the rolled sludge is very low as 30 to 50%. As a level, there is a problem that the iron content is insufficient to function as an iron source.

Therefore, the recycling of mill scales containing a large amount of iron without causing problems such as molten steel pollution still remains an urgent need for its development.

Disclosure of Invention The present invention has been made to solve the above-mentioned problems of the prior art, and it is an object of the present invention to provide a briquette and a method for manufacturing the same, which can sufficiently reduce iron in molten steel without causing problems such as molten steel contamination. It is done.

One aspect of the present invention for achieving the above object is a briquette briquette main component and the briquette consisting of 5 to 10% by weight of reducing agent, 25 to 40% by weight of electric furnace or steelmaking dust and 50 to 70% by weight of mill scale It is obtained by mixing by 2-10 parts by weight of the inorganic binder and 2-10 parts by weight of the organic binder per 100 parts by weight of the main component, followed by pressing.

At this time, the reducing agent is preferably one or two or more selected from cokes and pulverized coal.

In addition, it is effective that the inorganic binder is one or two or more selected from bentonite, cement, and water glass.

In addition, the organic binder is preferably starch.

In another aspect of the present invention, a manufacturing method for producing a briquette containing a mill scale includes a briquette consisting of 5 to 10 wt% of a reducing agent, 25 to 40 wt% of an electric furnace or steelmaking dust, and 50 to 70 wt% of a mill scale. Preparing and mixing 2-10 parts by weight of an inorganic binder and 2-10 parts by weight of an organic binder per 100 parts by weight of the main component and the briquette main component; Pressure molding the mixture formed in the mixing step to process briquette shapes; And curing the workpiece in the form of briquettes.

At this time, the reducing agent is preferably one or two or more selected from cokes and pulverized coal.

In addition, it is effective that the inorganic binder is one or two or more selected from bentonite, cement, and water glass.

In addition, the organic binder is preferably starch.

In addition, the pressure at the time of pressing is preferably 100 ~ 200kgf / cm ² .

And, it is effective that the temperature of the curing step is 100 ~ 300 ℃.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention, while deeply studying a method for increasing the content of mill scale in the briquette, when the briquette is used for iron supply in molten steel in the steelmaking process, the mill scale must be added to the briquette only It is not necessary to reduce all of the heavy oxide components, and when appropriately utilizing the reaction vessel and molten steel or the atmosphere of slag positioned thereon, the oxide components can be sufficiently reduced and supplied into the molten steel even if the amount of the reducing agent is slightly reduced. The present invention was confirmed.

For the above reason, the reducing agent of the present invention may be added in the briquette by a weight ratio of about 5 to 10%. When the content of the reducing agent is less than 5% by weight, the reducing power is not sufficient even though assisted by an ambient reducing atmosphere. In addition, when the amount of the reducing agent exceeds 10% by weight, the reducing agent is excessively added more than necessary, and as a result, the amount of the mill scale may be reduced. Therefore, it is appropriate that the reducing agent is added 5 to 10% by weight. At this time, it is preferable to use carbonized carbon (carbon products) as the reducing agent, and in particular, it is most preferable to use one or two or more selected from coke and pulverized coal, and the particle size of the carbon is particularly preferably less than 3 mm.

In addition, when the briquette is added, it can react with the slag located in the upper part of the molten steel and dissolve in the slag to supply iron in a short time. In this case, a solvent (reagent) is preferably included in the briquette. Do. For this reason, it is preferable to include an electric furnace or steelmaking dust in a briquette. The electric furnace or steelmaking dust refers to dust collected by dust collection equipment or the like generated in the electric furnace or steelmaking process, and has a form containing a large amount of CaO. In addition, the dust also contains a large amount of iron can also play a role of iron source. These dusts vary slightly depending on where they are collected and the conditions under which they are generated, but in the case of electric dust, they generally contain 48 to 57% by weight of T.Fe and 7 to 13% by weight of CaO and other impurities. 47 to 53% by weight of T.Fe, 8 to 18% by weight of CaO, and other impurities.

The electric furnace or steelmaking dust is preferably contained 25 to 40% by weight. If less than 25 wt% of the electric furnace or steelmaking dust is included, the role of dust as a solvent is not sufficient.On the contrary, if it contains more than 40 wt%, the content of the mill scale is insufficient as in the case of the reducing agent described above. It is difficult to have sufficient functions as an iron source.

The remaining component of the briquettes is the mill scale. The mill scale is preferably included 50 to 70% by weight relative to the total amount of briquettes. The content of the mill scale is to be determined in an amount excluding the content of the reducing agent and the electric furnace or steelmaking dust. At this time, the mill scale is preferably used to remove the oil components by washing to minimize the molten steel contamination.

As described above, the mill scale is meant to encompass all the scales collected in the rolling process, but specific examples thereof include T. Fe: 70 to 80 wt%, CaO: 0.1 wt% or less, and SiO ₂ : 2 weight % Or less, S: 0.1% or less, C: 0.5% or less.

Therefore, the briquette of this invention consists of 5-10 weight% of reducing agents, 25-40 weight% of electric furnaces or steelmaking dust, and 50-70 weight% of mill scales. However, the binder alone is included because the components of the briquette alone cannot provide the binding force necessary to form the aggregates.

In the present invention, since the oil component contained in the mill scale is removed, it is difficult to expect an effect when using bitumen or bitumen emulsion as a binder as in the Republic of Korea Patent Publication No. 2003-90803, and the bitumen binder It also has the problem of contaminating molten steel components.

Therefore, when the inventors of the present invention review the inorganic binders such as bentonite, cement, water glass, and organic binders such as starch at the same time as a binder, the bonding strength of briquettes including the oil scale and the mill scale is removed to a sufficient level. Of course, it was found that there are few problems such as molten steel contamination.

At this time, the inorganic binder and the organic binder is preferably contained together 2 to 10 parts by weight with respect to 100 parts by weight of the briquette main component consisting of the above-described reducing agent, electric furnace or steelmaking dust and mill scale.

If the content of any one of the inorganic binder and the organic binder is less than 2 parts by weight with respect to 100 parts by weight of the briquette main component, the initial strength of the briquette cannot be secured and stored in a silo, or put into the reaction container. When the briquette is pulverized and lost as a result of the strong rising air present in the furnace, a problem may occur. On the contrary, if the content exceeds 10 parts by weight, the strength and the effect of increasing the strength of the inorganic and organic binders may be reduced. It is 2 to 10 parts by weight based on 100 parts by weight of the briquette main component consisting of an electric furnace or steelmaking dust and mill scale.

It is preferable that the briquette including the mill scale of the above-mentioned form is manufactured by the following manufacturing process.

First, 2 to 10 parts by weight of the briquette main component, the organic binder and the inorganic binder each composed of 5 to 10 wt% of a reducing agent, 25 to 40 wt% of an electric furnace or steelmaking dust, and 50 to 70 wt% of a mill scale, respectively. 10 parts by weight of preparation and mixing need to be preceded.

At the time of the mixing, mixing with an appropriate amount of water is preferable. However, the term 'titration' as used herein means an amount necessary for briquetting, and a person having ordinary knowledge in the technical field to which the present invention belongs can easily perform 'titration' of water required for briquetting without trial and error. It does not need to specifically limit the content.

Next, it is necessary to press-form the mixture formed in the mixing step to process into a briquette shape. If the initial strength is not secured, it may be destroyed again during the curing process.

The pressure at the time of press molding is sufficient if the usual briquetting pressure, it is more preferably between 100 to 200 kgf / cm ² . In addition, the briquettes preferably have a particle size of between 5 and 50 mm in consideration of ease of feeding and storage.

In addition, in order to manufacture a mill scale briquette having a higher compressive strength, it is necessary to further improve the strength through curing. Curing temperature is preferably 100 ~ 300 ℃, if less than 100 ℃ strength after curing is less than 40kgf / cm ² curing effect is not enough, if it exceeds 300 ℃ such as briquette cracking due to high heat This is because problems can occur.

As an example of a drying method, the method of drying in a heating furnace is mentioned, but it is not necessarily limited to this method.

The curing time depends on the curing temperature, but curing may be performed until the water including the bound water is completely removed. Through the curing process as described above it is possible to obtain a high strength briquette having a high compressive strength.

That is, the manufacturing method of the present invention is a briquette main component, an organic binder and an inorganic binder, each composed of 5-10 wt% of a reducing agent, 25-40 wt% of an electric furnace or steelmaking dust, and 50-70 wt% of a mill scale, respectively. Preparing to mix 2 to 10 parts by weight with respect to 100 parts by weight; Pressure molding the mixture formed in the mixing step to process briquette shapes; And it consists of the step of curing the workpiece of the briquette-shaped according to the manufacturing method of the present invention can provide a mill scale briquette having the above-mentioned advantageous effect.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, it should be noted that the following examples are only intended to describe the present invention in more detail, but are not intended to limit the scope of the present invention to the scope of the following examples.

(Example)

Briquette  Measurement of iron recovery by the influence of the main component

After the mill scale briquette main component and 5 parts by weight of bentonite and 5 parts by weight of starch were added to the blending ratio shown in Table 1, and then mixed to form a briquette at a pressure of 170kgf / cm ² Briquettes were prepared by curing for 5 hours at a temperature of 250 ° C. In Table 1, when iron recovery is 70% or more, good (○), 50 to 70% is normal (△), and when 50% or less are indicated as defective (×).

The recovery rate of iron, 1kg briquettes were put in an induction furnace loaded with 100kg of molten steel at 1550 ° C. and maintained for 1 hour to recover iron, and then the recovery rate of iron contained in briquettes from the weight change of molten steel shown. It was measured in such a way that.

division Compounding ratio (% by weight) Iron recovery Mill scale Steelmaking Dust Minute coke (coal ash) Example 1 50 40 10 ○ Example 2 55 40 5 ○ Example 3 60 35 5 ○ Example 4 60 30 10 ○ Example 5 65 25 10 ○ Example 7 70 25 5 ○ Comparative Example 1 60 40 - × Comparative Example 2 48 50 2 △ Comparative Example 3 78 20 2 △ Comparative Example 4 35 60 5 ○

As can be seen in Table 1, in the case of Examples 1 to 6 in which the mass% of the carbonaceous material is 5 to 10% by weight in the mass scale of mill scale, steelmaking or electric dust and carbonaceous material, the iron recovery was good. Iron recovery was not good in the case of Comparative Examples 1 to 3 in which carbonaceous material was added at 5 wt% or less or the dust content was less than 25 wt% as defined in the present invention. From this, it can be seen that the content of carbonaceous material is more than 5% by weight, dust content is more than 25% by weight. In addition, in Comparative Example 4, the carbon ash content satisfies the range defined herein, but the dust content is too high, and the iron recovery rate is satisfactory. Therefore, it does not fit the spirit of the present invention. Therefore, it was confirmed that the briquettes were the most preferred mill scales 50-70% by weight, dust 25-40% by weight, and carbonaceous material 5-10% by weight.

Strength Measurement According to Binder Mixing Ratio

After the briquette was prepared by mixing and curing the main components and the binder under the same briquette main component composition ratio as in Example 3 and the conditions shown in Table 2, the compressive strength and the rotational strength of each briquette were measured. Briquette production conditions are as described above.

In Table 2, when the compressive strength is 60 kgf / cm 2 or more, excellent (○), when 40 to 50 kgf / cm 2 is normal (△), and when 40 kgf / cm 2 or less are indicated as defective (×). In addition, the rotational strength is the value measured after rotating for 200 cycles at 25rpm, the weight of the briquette of + 6.3mm after centrifugation of 200kg of the prepared + 10mm briquettes 200kg in a tumbler, 75% The case where it was higher was classified as good ((circle)) and the case where it was higher than 65% as normal (△), and the case where it was 65% or less as defect (x).

division Compounding ratio (weight ratio) Compressive strength Rotational strength Briquette Active Ingredients Bentonite parts by weight Starch weight part Example 1 100 3 2 △ ○ Example 2 100 2 3 ○ △ Example 3 100 3 3 ○ ○ Example 4 100 5 5 ○ ○ Example 5 100 5 10 ○ ○ Example 6 100 10 5 ○ ○ Example 7 100 10 10 ○ ○ Comparative Example 1 100 - - × × Comparative Example 2 100 One 2 △ × Comparative Example 3 100 2 One × △ Comparative Example 4 100 5 - × ○ Comparative Example 5 100 - 5 ○ ×

As confirmed from Table 2, Example 1 in which the mixing ratio of bentonite (inorganic binder) and starch (organic binder) as a binder in a mixture of mill scale, steelmaking or electric dust and carbonaceous material satisfies the conditions defined in the present invention. In Example 7 it can be seen that both the compressive strength and the rotational strength is good. However, in the case of Comparative Examples 1 to 5 in which the content of the binder is less than the scope of the present invention or in which only one binder is included, the compressive strength and the rotational strength were not all higher than the normal level.

Therefore, bentonite 2-10 weight by weight in a mixture of 50-70% by weight of mill scale, 25-40% by weight of steelmaking or electric furnace dust, and 5-10% by weight of carbonaceous material, in which both iron recovery and iron recovery are in good range. Mill scale briquettes prepared by mixing either or both of 2% by weight or starch 2% by weight were found to be the most preferred.

According to the present invention, it is possible to provide a briquette and a manufacturing method thereof capable of sufficiently reducing iron and supplying iron powder to molten steel without causing problems such as molten steel contamination and the like, and are effective for mill scale recycling. to be.

Claims (10)

Briquette main component consisting of 5 to 10% by weight of reducing agent, 25 to 40% by weight of electric furnace or steelmaking dust, and 50 to 70% by weight of mill scale, 2 to 10 parts by weight of inorganic binder and organic binder 2 per 100 parts by weight of the briquette main component A briquette containing a mill scale, characterized in that it is obtained by mixing -10 parts by weight and then pressing. The briquette containing mill scale according to claim 1, wherein the reducing agent is one or two or more selected from coke and pulverized coal. The briquette containing mill scale according to claim 1, wherein the inorganic binder is one or two or more selected from bentonite, cement, and water glass. 2. The briquette of claim 1 wherein the organic binder is starch. Briquette main component consisting of 5 to 10% by weight of reducing agent, 25 to 40% by weight of electric furnace or steelmaking dust, and 50 to 70% by weight of mill scale, 2 to 10 parts by weight of inorganic binder and organic binder 2 per 100 parts by weight of the briquette main component Preparing to mix 10 parts by weight; Pressure molding the mixture formed in the mixing step to process briquette shapes; And Curing the workpiece of briquette shape; Briquette production method containing a mill scale, characterized in that consisting of. The method of claim 5, wherein the reducing agent is briquette production method containing briquettes, characterized in that at least one selected from coke and pulverized coal. 6. The method according to claim 5, wherein the inorganic binder is one or two or more selected from bentonite, cement, and water glass. 6. The method according to claim 5, wherein the organic binder is starch. The method of claim 5, wherein the pressure during the molding process briquettes containing mill scale, characterized in that 100 ~ 200kgf / cm ² . The method of claim 5, wherein the temperature of the curing step is a briquette manufacturing method containing a mill scale, characterized in that 100 ~ 300 ℃.