KR100840264B1 - Magnesia-carbon coating material for the iron making vessel - Google Patents

Abstract

The present invention relates to a coating prepared in the form of pellets or briquettes by mixing light MgO powder, anthracite and a binder, through which the coating property of the steelmaking converter can be maintained uniformly.

Slag Coating, Viscosity, Anthracite, Pellets, Briquettes, Coatings, Steel Converters

Description

MAGO-C coating agent for steelmaking converter {MAGNESIA-CARBON COATING MATERIAL FOR THE IRON MAKING VESSEL}

1 is a schematic diagram of the slag coating operation in the converter during the steelmaking process.

<Explanation of symbols for the main parts of the drawings>

1. converter 2. hearth hopper

3. slag 4. coating agent

5. Anthracite (coal) 6. Combustion reaction (Anthracite loss)

7. Coated slag

The present invention relates to a MgO-C mixed coating for steelmaking converter, and more particularly, to a coating prepared in the form of pellets or briquettes by mixing light MgO powder and anthracite.

In the steel manufacturing process for producing steel from raw materials, the raw materials are blown into a furnace and subjected to a steelmaking process to reduce iron ore, and then the necessary alloying elements are added from the iron ore from which the impurities are removed, and the temperature is raised for the subsequent process. The steelmaking process will be carried out.

This steelmaking process usually consists of molten iron pretreatment, converter refining, and secondary refining. In each of these processes, the molten iron pretreatment removes sulfur and phosphorus using various fluxes, and in the refining, the pure oxygen is deodorized. In this case, the secondary refining removes oxygen and oxides due to the oxygen injection during the converter refining.

To describe the converter refining process in more detail in the steelmaking process, converter refining takes high-speed oxygen into molten iron containing a large amount of impurities such as carbon (C), silicon (Si), phosphorus (P), and manganese (Mn). In this process, molten steel of high temperature (1600 ° C to 1750 ° C) is produced by heat of oxidation of each impurity element. As shown in the following Chemical Formula 1, carbon in the molten iron reacts with oxygen to form CO and CO ₂ gas and is thus released into the atmosphere, but other elements form oxides and then float over the molten steel to form slag. This slag formation scheme is represented by the following formula (2).

[C] + 1/2 O ₂ = CO (g) or [C] + O ₂ = CO ₂ (g)

[M] + X / 2 O ₂ = MO _X

Here, [M] is silicon (Si), manganese (Mn), phosphorus (P), etc.                         

In the converter blowing operation, in particular, a large amount of quicklime (CaO) is added to stably fix impurity elements in the slag, and the added quicklime reacts with SiO ₂ , FeO and the like to melt into the slag. The slag generated during the converter refining process is generated by injecting oxygen, and therefore contains a large amount of high temperature FeO and CaO during the blowing.

The converter, in which the converter blow operation is carried out, consists of an outer shell and an inner refractory, where the refractory is built inside the converter to protect the shell from slag and molten steel. The refractory herein uses materials which can withstand high temperatures and are excellent in chemical and thermal resistance with slag. That is, the inner wall of the converter is constructed of magnesia carbon (MgO-C) brick having excellent corrosion resistance, and the carbon in the refractory material in the case of slag containing a large amount of high-temperature iron oxide (FeO), as shown in the following formula (3): Reacts with iron oxide in the slag to reduce the iron to form a layer of iron (Fe) that is not harmful to the refractory, it is resistant to thermal shock due to the excellent thermal conductivity due to carbon containing, high temperature due to magnesium oxide (MgO) excellent in high temperature characteristics Excellent corrosion resistance at Therefore, the life of the refractory can be extended.

[FeO] (in slag) + [C] (in MgO-C lead) = Fe + CO (g)

However, as in the reaction shown in Chemical Formula 3, the disadvantage is that the oxidation of carbon relaxes the connective structure of magnesia carbon (MgO-C), causing a spalling phenomenon in which magnesium oxide (MgO) crystals are released from the refractory. have. Therefore, in order to improve the life of the refractory of the converter, it is important to control the properties of the slag during the converter slag coating operation so that the slag adheres well to the refractory. The converter slag coating here attaches the slag generated during the blow operation to the furnace wall refractory during the resumption after the termination of the blow operation, thereby preventing the furnace wall refractory from physically or chemically eroding.

Currently, a typical converter refractory coating method, the slag preheated after the tapping is left in the converter in a large amount, and the endothermic (CaO · MgO) and dolomite (CaCO ₃ · MgCO ₃ ) as a quicklime is added to the endothermic sikimyeo through the calcination reaction of the reaction of dolomite increase the viscosity of the residual slag, magnesium oxide (MgO) the tilt (傾動) and nitrogen slag injection of further increasing the converter the viscosity by changing the composition of the residual slag with saturated slag (N ₂ slag A method of adhering to the furnace wall through spalshing coating is used.

CaCO ₃ ㆍ MgCO ₃ = CaO + MgO + 2CO ₂ + ΔH

This coating method is to form a coating layer of MgO-saturated slag layer to suppress the elution of MgO from the refractory by FeO during blowing, or after slag contact with highly oxidizing atmosphere with oxygen pressure of about 0.21 atm Most of the Fe-based compound in the slag is present as Fe ₂ O ₃ , the coating layer produced at this time has a low melting point characteristics due to Fe ₂ O ₃ and the initial coating layer is dissolved and absorbed into the slag layer is limited to the coating effect There is.

Therefore, in order to prevent this, as shown in the following Chemical Formula 5, in the case of the coating method in which anthracite or coke is added after coating, Fe ₂ O ₃ is reduced to FeO to change the coating layer into a MgO-FeO-based high melting solid solution. In addition to improving coating properties, the carbon inside the coated slag layer (unreacted carbon or unreacted carbon from coke) also plays the same role as C in MgO-C, making the FeO-containing slag harmless and inhibiting chemical erosion. This has the advantage.

[Fe ₂ O ₃ ] (in slag) + [C] (in anthracite or coke) = 2FeO + CO (g)

However, when the conventional dolomite (or light dolomite) and anthracite (or coke) are added separately, there is a variation in quality of the coating layer depending on the input method. In other words, when dolomite is introduced first and anthracite is added, the viscosity of slag becomes higher due to the addition of dolomite, and when the anthracite is added later, the reactivity of the anthracite coal with slag decreases, and due to the sensible heat inside the converter, Many losses will occur. On the contrary, when anthracite is added first, anthracite first induces a reduction reaction in slag of low viscosity, thereby improving reactivity of the anthracite, but a low viscosity FeO-based slag reacts with the atmosphere at high speed before introducing dolomite. Since the Fe ₂ O ₃ is formed again, the slag reduction effect due to the anthracite injection is inferior. In addition, in the case of simultaneous input, it does not fall simultaneously to the same part due to the characteristics of converter equipment, which causes unevenness of the coating layer, which acts as a factor causing variation in composition of the coating layer, induction of thickness variation, and deterioration of coating property.

In the aspect of eliminating this nonuniformity and recycling the waste smoke generated from the converter, there is a method of using the waste smoke of the MgO-C component generated after dismantling the converter refractory.

However, in the case of this method, the waste smoke of the already used MgO-C component and the content of the C component is already reduced during the blowing reaction according to the above formula (3), as well as the component deviation by the converter blowing conditions, parts of the refractory There is a disadvantage in that the uniformity of the coating layer is difficult to be different. In addition, the carbon in MgO-C exists as graphite, which is a plate-like structure, the reaction rate is lower than the use of the amorphous anthracite coal of the present invention, there is a fear that the coating is not uniform. In addition, the use of such a confectionery is limited in its generation is not suitable for the converter operation under a mass production system, there is a problem that the workability is inferior because the shape is not constant because it is used by crushing the existing.

In order to overcome the problems of the prior art described above, the present invention is to solve the unevenness of the coating layer due to the addition of anthracite and MgO components such as dolomite and to minimize the loss of the injected carbon components, light MgO powder, anthracite and binder It is to provide a coating for steelmaking converters containing.

In addition, an object of the present invention is to adjust the coating layer components freely to match the components of the MgO-C edible to improve the coating property (wetting of the coated layer and edible), and to minimize the lightness of the MgO powder to ensure the flexibility of the equipment through the use of mixed raw materials To provide a coating for steelmaking converters containing anthracite and a binder.

The present invention relates to coatings for steelmaking converters in the form of pellets or briquettes made of light MgO powder, anthracite and binders.

In the coating of the present invention, the MgO content is preferably 30 to 93% by weight, the carbon content is 5 to 40% by weight, and the CaO content is 2 to 20% by weight.

In addition, examples of binders usable in the coating of the present invention include, but are not limited to, cement, gypsum (gypsium, CaSiO ₄ ), limestone, and the like.

The present invention relates to a coating agent used in the slag coating operation for the purpose of protecting the internal refractory of the converter for treating high temperature molten steel in the steelmaking process, by improving the coating property by synthesizing the light MgO powder and anthracite coal at the same time It is possible to reduce coating loss to the atmosphere and to minimize equipment constraints.

The small MgO powder is to increase the MgO concentration in the slag, the anthracite is to reduce the iron oxide (Fe _x O) in the slag to control the crystal phase to form a coating layer of a high melting point compound. To this end, MgO powder and anthracite coal with a high MgO component ratio are mixed to make the MgO content in the coating material 30 to 95% by weight, and prepared in pellet or briquette form so that the carbon content is 5 to 40% by weight.

Conventional MgO-based raw materials (Dolomite or light dolomite), which are applied during slag coating, increase the MgO concentration in the coated slag to make the component supersaturated and increase the viscosity and chemical erosion of converter refractory (MgO-C) by FeO in the slag. To prevent. To this end, 20-30% of dolomite (MgO) or dolomite has been used to increase the content of MgO to 35-45% by firstly calcining dolomite (MgO). However, the dolomite or light dolomite does not have a high content of MgO component, so there is a problem in that a large amount of dolomite and light dolomite should be added in order to add as much MgO as the required amount, and thus heat loss may occur. In this case, when the dolomite and the light dolomite are added in excess, the coating slag is cured, and thus the coating property is deteriorated. Therefore, it is necessary to secure an appropriate MgO amount relative to the input amount.

Therefore, in the present invention, in order to secure various MgO concentrations suitable for the respective conditions, the MgO component in the coating agent of the present invention is 30% by weight or more using MgO powder. For this reason, in the present invention, the MgO component in the coating agent is 30 to 95% by weight. Dolomite, light dolomite, and the chemical composition of the MgO powder is shown in Table 1 below.

Anthracite coal used for slag coating is a component that is added to reduce the Fe ₂ O ₃ component of the coating slag to FeO to form the coating slag into a high-melting MgO-FeO layer, and the sulfur contained in the component There was a limit due to the loss by reaction with oxygen in flames and hot air. Therefore, in the present invention, when the anthracite coal is mixed with the MgO-containing coating agent in order to minimize the loss and to ensure an appropriate carbon concentration according to the coating agent input amount, the carbon content in the coating agent is mixed so as to be 5 to 40% by weight of pellet or Prepare briquettes. In addition, in the case of anthracite, its crystal structure is amorphous, which has the advantage of being more reactive than graphite or coke having a plate structure used in the prior art. When the carbon content in the coating agent exceeds 40% by weight, when a large amount of MgO is added to match the MgO component ratio of the coating slag, the excessive amount of carbon is burned into the air, resulting in loss of iron oxide (Fe _X O). ) Is reduced to iron (Fe) and rather inhibits the coating slag from adhering to the furnace wall. In addition, when the anthracite coal is mixed so that the carbon content is less than 5% by weight, the role of carbon (C) in the coating agent becomes extremely insignificant to achieve the object of the present invention.

The anthracite coal used in the present invention is shown in Table 2 below.

Unlike conventional coatings using waste smoke, binders are used as needed to manufacture briquettes or pellets using MgO powder and anthracite coal. Examples of such binders include cement, gypsum (gypsum, CaSiO ₄ ), and limestone. Including but not limited to. The MgO powder and anthracite are mixed and then prepared in the form of pellets or briquettes using a binder. In the present invention, in order to maintain the bond strength at high temperature, the CaO component in the coating agent is preferably 2 to 20% by weight.

As an example of the present invention, the slag coating process in the converter in the steelmaking process will be described. After the molten metal produced in the converter is discharged through the hot water outlet, the slag on the upper portion of the molten metal remains in the converter 1. At this time, as shown in FIG. 1, the coating agent 4 is charged into the converter 1 through the hearth hopper 2. The anthracite (5) contained in the coating (4) charged into the converter (1) forms a coated slag (7) during the combustion reaction (6) with the slag remaining in the converter (1). The coated slag 7 produced at the bottom of the converter 1 is uniformly coated on the inner wall of the converter 1 using the tilting of the converter 1 and the nitrogen slag spray coating method.

Hereinafter, the present invention will be described in detail with reference to preferred examples, but the protection scope of the present invention is not intended to be limited to the following examples.

Example 1-5

Light MgO powder, anthracite coal and a binder were mixed in the component ratios shown in Table 4 and then sintered to prepare a coating in pellet or briquette form. Component analysis was performed on the MgO component, C component and CaO component of the prepared coating agent, respectively, and the results are shown in Table 3.

The prepared coating agent was put into a steelmaking converter and the converter was coated for the time shown in Table 3, and the obtained coating layer and the degree of coating property were evaluated as good and normal.

Comparative Example 1

Instead of the coating agent of Example 1, only light dolomite was added to the steelmaking converter and the converter was coated for the time shown in Table 3 above, and the obtained coating layer and the degree of coating property were evaluated as good and normal.

Comparative Example 2

In place of the coating agent of Example 1, light dolomite and anthracite coal were added to the steelmaking converter, and the converter was coated for the time shown in Table 3 above, and the obtained coating layer and the degree of coating property were evaluated as good and moderate.

Comparative Example 3

Instead of the coating agent of Example 1, waste lead and [MgO-graphite (graphite)] were added to the steelmaking converter and the converter was coated for the time shown in Table 3 above, and the obtained coating layer and the degree of coating property were evaluated as good and normal. The component composition with the said waste smoke is shown in the said Table 4.

When using the product obtained by the present invention as in the Comparative Examples and Examples described above, the loss of carbon (C) to the atmosphere compared to Comparative Example 1 and Comparative Example 2 which was coated separately by the conventional light dolomite and anthracite coal separately It can be seen from Table 4 that the amount is reduced, there is an advantage that can prevent the case of the coating state is not good due to the variation in coating properties that may occur when the anthracite coal is added separately.

That is, as in the case of 2-2 and 2-5 of Comparative Example 2, a large amount of unreacted loss of the injected anthracite coal is generated, the effect of the actual anthracite coal injected does not appear as it is, the coating properties slightly worsen, When the invention is applied, this phenomenon does not appear at all, and it can be confirmed that a consistent coating property is secured. In addition, when the waste smoke is recycled and used, that is, when using anthracite instead of graphite as [C], it can be confirmed that the coating time is shortened because the reaction rate of the anthracite in the amorphous crystal structure is fast. Therefore, in the case of the present invention is very advantageous in improving the coating properties.

As described above, to minimize the loss of the carbon component introduced through the present invention, to improve the coating property (wetting of the coating layer and yeonwa) to make it uniform, to ensure the flexibility of the facility through the use of mixed raw materials, recycling the waste smoke The degradation of the reactivity of graphite can be overcome.

Although the present invention has been described above, it will be readily understood by those skilled in the art that many other modifications and variations are possible without departing from the spirit and scope of the claims set out below. .

Claims (5)

Coating for steelmaking converters in the form of pellets or briquettes made of light MgO powder, anthracite and binder. The method of claim 1, MgO content of the coating agent is a coating agent for steelmaking converter is 30 to 93% by weight. The method of claim 1, Carbon coating in the coating agent is a coating agent for steelmaking converter 5 to 40% by weight. The method of claim 1, CaO content of the coating agent is a coating agent for steelmaking converter is 2 to 20% by weight. The method according to any one of claims 1 to 4, Wherein the binder is cement, gypsum (gypsium, CaSiO ₄ ) and the coating agent for steel converter is at least one selected from the group consisting of limestone.

Images