KR100526126B1 - Formed coal having superior initial strength - Google Patents

Abstract

The present invention relates to a metallurgical coal briquette used in the melt reduction process or the corex process of the new steelmaking method, the purpose of which is to press-molded at room temperature by using lignoselfonate as a binder while using quicklime as an additive to control the water content of pulverized coal. It is possible to provide coal briquettes having excellent low temperature stability, easy mass handling, and excellent initial strength.

The present invention for achieving the above object is a quicklime: 1 to 5 parts by weight and lignocellonate solution as a binder: 7 to 15 parts by weight of an additive for removing water from fine coals with respect to 100 parts by weight of pulverized coal and pulverized coal The technical subject matter is a coal briquette having excellent initial strength.

Description

Formed coal having superior initial strength

The present invention relates to a metallurgical coal briquette used in a melt reduction process or a corex process of a new steelmaking method, and more particularly, a liquid phase for use in a molten iron reduction process while omitting the drying process of pulverized coal due to exothermic reaction of moisture and quicklime of pulverized coal. The present invention relates to coal briquettes using Lignosulfonate solution as a binder.

In the FINEX and COREX processes, which are a type of melt-reducing steelmaking process, the new steel making method is known to have many advantages in terms of fuel use because coal, not coke, is used as input fuel for the furnace. Coal used as a fuel is collected in the dust collector and is not sufficiently burned in the smelter if it is about 8mm or less, and excessive use of pulverized coal causes limitations in the process and causes problems in operation. . However, most of the steelmaking coal is composed of fines less than 8mm.

Since pulverized coal is limited to use in melt reduction process, it is used for Pulverized Coal Injection (PCI) or coke coal. However, due to the characteristics of coal for Corex, there is a limit to transferring unused pulverized coal to other uses. have. Therefore, there is a need for the development of a technique for producing coal briquettes by agglomerating fine coal in an appropriate manner.

The technique of making pulverized coal into coal briquettes and using them for coke production is disclosed in Japanese Patent Laid-Open No. 7-97576 (published on April 11, 1995). This technology heats and melts binders such as coal tar and pitch above softening temperature (about 150 ℃), adds a certain amount to pulverized coal, mixes it sufficiently and then press-forms the molten binder after molding. It is a technique of manufacturing coal briquettes by cooling below softening temperature. The coal briquettes exhibit sufficient mechanical strength for transport handling because they firmly bind the coal particles by cooling the pitch binder. However, since the binder is heated above the softening temperature, a large-scale heating facility is required, and at this time, harmful gases are generated, which entails enormous expenses for the deterioration of the working environment and its prevention. In the case of using the coal briquettes in a molten steelmaking process, the coal briquettes are required to be hundreds of tons or more every day, so the coal briquettes are piled up outdoors. Therefore, in summer, the temperature of the yard increases to 40 ~ 60 ℃ due to solar heat, and this temperature is close to the softening temperature of the pitch binder, and the pitch binder used in the coal briquettes is softened again and sticks to the coal briquettes. Mass handling is difficult.

On the other hand, pulverized coal contains a large amount of water, so when the coal briquettes are manufactured by pressing the pulverized coal at room temperature, there is a problem that the cold strength of the coal briquettes is weakened due to excessive moisture content. As a result, the recovery rate is lowered in the process of manufacturing coal briquettes, which requires an additional drying process for removing moisture, thereby lowering productivity and increasing costs.

The present invention has been proposed to solve the above problems, by using the lignoselfonate solution which can maintain the viscosity at room temperature as a binder by omitting the drying process of the pulverized coal due to the exothermic reaction of the powdered coal and quicklime It is an object of the present invention to provide coal briquettes having excellent low temperature stability, excellent initial strength, and easy mass handling without a heating process.

The coal briquettes of the present invention for achieving the above object are composed of quicklime: 1 to 5 parts by weight and lignocellfonate solution: 7 to 15 parts by weight based on finely divided coal and 100 parts by weight of the fine coal.

Hereinafter, the present invention will be described in detail.

The inventors of the present invention are seeking to secure a high strength that can be applied to a molten steelmaking process while massifying the pulverized coal without drying it, while the water-containing pulverized coal and quicklime (CaO) are formed due to the following chemical reaction. It was confirmed that the water of the pulverized coal is removed due to the strong exothermic reaction as it is converted into calcareous lime (Ca (OH) 2).

Scheme 1

CaO + H2O → Ca (OH) ₂

In addition, it was confirmed that when a lignoselfonate solution capable of maintaining viscosity at room temperature was used as a binder together with pulverized coal and quicklime, the strength of the coal briquettes could be ensured and used in a melt reduction process.

In this invention which started from this point of view, a raw material is mix | blended so that it may be comprised from (1) to 5 parts by weight of quicklime, (1 to 5 parts by weight) and (3) lignocellonate solution: 7 to 15 parts by weight of fine coal.

① Pulverized coal

In the present invention, the pulverized coal is used as a raw material of coal which is not used in the particle size regulation in the Corex process. Usually, about 8 mm or more coal is used in the Corex process so that the pulverized coal is used less than that. Preferably pulverized coal is used to about 4mm or less. If it is larger than about 4 mm, the pressure exerted during the molding increases so much that the coal briquettes may be cracked, thereby reducing the strength of the coal briquettes. More preferably, about 60% or more of pulverized coal of about 1 mm or less is used.

In the present invention, even if water is contained in the pulverized coal, it can be used immediately without undergoing a drying process, but the moisture content of the pulverized coal is related to the amount of quicklime blended. In the present invention, when considering the blending amount with quicklime, pulverized coal is most preferably about 6 to 12% of water content. When the pulverized coal content is too small, the chemical reaction with quicklime does not occur sufficiently and the strength of the coal briquettes is reduced. Even when the moisture content is too high, the molding coal is not well formed and the strength of the coal briquettes is difficult to secure the quality of the coal briquettes.

② quicklime

In the present invention, quicklime removes the water of fine coal to enhance the strength of coal briquettes. Quicklime (CaO) is converted to hydrated by the water contained in the pulverized coal and the reaction as in Scheme 1, causing an intense exothermic reaction serves to remove the water of the pulverized coal. The quicker the lime, the smaller the particle size, and the larger the specific surface area, which is advantageous to the conversion of the calcined circuit by reacting with moisture in the pulverized coal. Therefore, the smaller the particle size is, the more advantageous it is, and it is preferable to use quicklime of about 1 mm or less. It is best to secure the strength of coal briquettes when the particle size of less than about 0.3mm is used for the quicklime more than 50% by weight. If the particle size is larger than 1mm and the particle size distribution of less than 0.3mm is less than 50%, it may not cause sufficient chemical reaction with the water in the pulverized coal, so that unreacted quicklim may remain inside the coal briquettes even after molding. Unreacted quicklime in the coal briquettes causes chemical reactions in contact with moisture in the air, thereby slightly reducing the strength of the coal briquettes.

The quicklime of the present invention is preferably added 1-5 parts by weight based on 100 parts by weight of pulverized coal. If the amount of quicklime is less than 1 part by weight, the amount of quicklime is too small to perform the role of sufficiently removing moisture. If the amount of quicklime exceeds 5 parts by weight, the physical properties of the coal briquettes are poor. Because it occurs.

③ lignocellonate solution

In the present invention, as a binder, a lignoselfonate solution that does not use solid materials such as coal tar or pitch, which are difficult to handle in large quantities, is easily maintained in a room temperature and is easy to handle in large quantities. Solid content in lignocellonate solution is most preferred in terms of securing strength of coal briquettes when the content is 40 to 70% by weight. If the content of solids is less than 40% by weight in the lignocellonate solution, the amount of lignocellonate that exhibits the binder properties is small, the moisture content is high, and the strength of the coal briquettes may be slightly reduced, and the content of solids is 70% by weight. If exceeded, the viscosity of the lignocellfonate solution is high, which makes it somewhat difficult to uniformly mix.

It is preferable to use 7-15 weight part of compounding quantities of lignocellfonate solution with respect to 100 weight part of pulverized coal.

If the added amount of lignocellonate solution is less than 7 parts by weight, the binder may not be sufficient in the fine coal, which may cause a problem in the strength of coal briquettes. I can cause it.

Hereinafter, the present invention will be described in more detail with reference to Examples.

EXAMPLE

First, uniformly mix the quicklime for controlling the water content with fine coal (water content: 6 ~ 12%) of 3.4mm or less, and then uniformly mix the lignoselfonate solution having a solid content of 50% by weight as a binder. Pressurized using a Briquetter Roll Press at room temperature to prepare a pillow-shaped coal briquettes 63.5mm in diameter, 25.4mm in width and 19.1mm in thickness. Table 1 shows an example of the present invention and a comparative example for comparing the same.

Experimental Example Pulverized coal (part by weight) of 3.4 mm or less additive Lignocellonate solution addition amount (part by weight) Kinds Usage (part by weight) Inventive Example 1 100 quicklime 3 10 Inventive Example 2 100 quicklime 3 8 Inventive Example 3 100 quicklime 2 10 Comparative Example 1 100 - - 10 Comparative Example 2 100 Calcium carbonate 3 10 Comparative Example 3 100 Slaked lime 3 10 Comparative Example 4 100 quicklime One 6

Inventive Examples 1 to 3 of Table 1 mix 2 to 3 parts by weight of quicklime with respect to 100 parts by weight of pulverized coal, and then mix with 8 to 10 parts by weight of lignoselfonate solution binder to press-mold at room temperature to form coal briquettes. It is manufactured.

In Comparative Example 1, 10 parts by weight of lignoselfonate solution binder was added to 100 parts by weight of pulverized coal, and Comparative Example 2 was uniformly mixed with 3 parts by weight of calcium carbonate (CaCO3) based on 100 parts by weight of pulverized coal. Coal briquettes were prepared by mixing with 10 parts by weight of lignoselfonate solution binder and pressure molding at room temperature. In Comparative Example 3, 3 parts by weight of hydrated lime (Ca (OH) 2) was uniformly mixed with 100 parts by weight of pulverized coal, and then mixed with 10 parts by weight of lignoselfonate solution binder to form a coal briquette at room temperature. In Comparative Example 4, 1 part by weight of quicklime was uniformly mixed with 100 parts by weight of pulverized coal, followed by mixing with 6 parts by weight of lignoselfonate solution binder to form a coal briquette at room temperature.

As soon as the coal briquettes were manufactured, drop strength and dust generation rate were measured.

Drop strength was evaluated by dropping approximately 2Kg of coal briquettes on a steel plate four times freely at 5M height and remaining the coal briquettes of 10 mm or more as shown in Equation (1) below. It evaluated as Formula (2).

[Equation 1]

[Equation 2]

Table 2 below evaluates the drop strength of the coal briquettes manufactured according to the invention examples and comparative examples of Table 1.

Experimental Example Drop strength (%) Minute occurrence rate (%) Inventive Example 1 84.3 11.8 Inventive Example 2 80.2 15.5 Inventive Example 3 78.6 17.3 Comparative Example 1 22.0 68.6 Comparative Example 2 25.5 64.8 Comparative Example 3 69.2 22.3 Comparative Example 4 29.1 56.8

As can be seen in Table 2 above, the coal briquettes having excellent initial strengths were manufactured, with the drop strength of the invention examples 1-3 satisfying the scope of the present invention being 78% or more and the minute generation rate of 18% or less. In the case of Comparative Examples 1-4, which do not satisfy the scope of the invention, it can be seen that the initial strength of the coal briquettes is lowered because the drop strength is lowered and the dust generation rate is higher than that of the above-described invention examples.

Table 3 shows the strength and generation rate range of coal and coal briquettes. In the melt reduction steelmaking process, the falling strength of coal during the actual operation is within the allowable range, and below that, problems occur due to productivity decrease and operation failure due to lowering of the molten iron temperature. In addition, in the generation of powder, when the powder is generated and charged more than the allowable range, it is not sufficiently burned in the melting furnace and is excessively collected in the dust collector, which increases the operating cost and adversely affects the process, thereby making the operation unstable. However, coal briquettes have a small particle size during differentiation, thereby enhancing the optimum and acceptable range of the generation rate.

division Coal (10 ~ 60mm) Coal briquettes (10 ~ 60mm) Drop strength (%) Optimal range 80 or more 80 or more Allowable range 70 or more 70 or more Incidence rate (%) Optimal range below 10 5 or less Allowable range 25 or less 20 or less

As described above, according to the present invention, it is possible to provide coal briquettes capable of securing the optimum strength required in the FINEX and COREX processes of the new steelmaking method, and accordingly, the FINEX and the COREX, the new steelmaking method. This is a useful effect to improve the competitiveness of the COREX process.

Claims (7)

Coal briquettes having excellent initial strength composed of quicklime: 1 to 5 parts by weight and lignoselfonate solution: 7 to 15 parts by weight based on 100 parts by weight of fine coal and fine coal. The coal briquette having excellent initial strength according to claim 1, wherein the solid content of the lignocellonate solution is 40-70 wt%. The coal briquette having excellent initial strength of claim 1, wherein the coal briquette has a drop strength of 70% or more and a generation rate of 20% or less. The coal briquette having excellent initial strength according to claim 1, wherein the pulverized coal used in the coal briquettes has a moisture content of 6 to 12%. The coal briquette having excellent initial strength of claim 1, wherein the quicklime is 1 mm or less, and has a particle size of 0.3 mm or less and 50 wt% or more. The coal briquette having excellent initial strength according to claim 1, wherein the coal briquettes are press-molded at room temperature. The coal briquette having excellent initial strength according to claim 1, wherein the coal briquettes are omitted from the heat-drying process after press forming.