KR20040055926A - Method of manufacturing briquettes having superior strength - Google Patents

Abstract

PURPOSE: Provided is a method for preparing a molded charcoal having high strength without heating a binder or a coal. CONSTITUTION: The method comprises steps of (a) mixing 100 parts by weigh of a dust coal with 3-15 parts by weight of dusts containing 20-60 % of CaO; (b) mixing the mixture of the step (a) with 5-15 parts by weight of a molasses; and (c) molding the second mixture of the step (b) into molded charcoal.

Description

Method of manufacturing briquettes having superior strength {Method of manufacturing briquettes having superior strength}

The present invention relates to a method for producing pulverized coal into coal briquettes, and more particularly, to control uniform mixing order of pulverized coal, molasses, and CaO-containing dust, and to achieve uniform mixing, and to achieve a uniform mixing strength by chemical reaction of calcium in molasses and CaO-containing dust. It relates to a method for producing coal briquettes having been enhanced. Coal briquettes prepared according to the present invention is excellent in strength and can be applied to a molten steel reduction process, which is a new steelmaking method.

In the FINEX and COREX processes, which are a type of molten steel reduction process, new coal-making methods are known to have many advantages in terms of fuel use because coal is used as a fuel for melting furnace, not coke. However, when the coal used as fuel is less than about 8 mm, it is not sufficiently burned in the melting furnace and is collected in the dust collector, and when excessively used, the use of pulverized coal is limited in the steelmaking process because it causes imbalance in the process and causes problems in operation. . At present, the molten iron reduction process can only use lump coal that is larger than about 8 mm in size. However, since a considerable amount of the steelmaking coal currently used is composed of fine powder of about 8 mm or less, it is necessary to develop a manufacturing technique of coal briquettes which can be massified by an appropriate method.

Until now, there is no known technique for making pulverized coal into coal briquettes and applying them to the FINEX and COREX processes. However, Japanese Patent Application Laid-open No. Hei 7-97576 (published on April 11, 1995) is a technique for making pulverized coal into coal briquettes and using them for coke production. This technology heats and melts binders such as tar and pitch above softening temperature (about 150 ℃), adds them to pulverized coal, mixes them and press-molizes them to cool molten binder. It is a technique to manufacture. The coal briquettes exhibit sufficient mechanical strength for transport handling because they firmly bind the coal particles by the pitch binder. However, since the binder is heated above the softening temperature, a large-scale heating facility is required. At this time, harmful gases are generated, which entails enormous expenses for the deterioration of the working environment and its prevention. When the coal briquettes are loaded outdoors, when the temperature of the yard increases to 40-60 ° C. due to solar heat, the pitch is softened again because the pitch binder is near the softening temperature, and the coal briquettes are stuck to each other, so that mass handling by the mechanical force is prevented. Becomes difficult.

Meanwhile, US Patent No. US 4,738,685 discloses a method for producing coal briquettes by making molasses and an inorganic hardener to make coal briquettes for 1 hour at 200 to 300 ° C. In this method, since the curing efficiency is not good, the initial strength is low to cure for 1 to 3 days at room temperature or for 1 hour in an oven at 200 to 300 ℃ to improve the strength of coal briquettes. However, in order to heat the coal briquettes at 200 ° C. or more, a large-scale heat-drying facility is required, and thus there is a problem in that the cost and productivity are low in manufacturing coal briquettes.

The present invention has been proposed to solve the above problems, and provides a method of manufacturing coal briquettes having high strength by an environmentally friendly manufacturing process without a separate binder or coal heating step.

1 is a schematic diagram of a coal briquette manufacturing process according to the present invention.

※ Explanation of symbols about main part of drawing ※

4, 5: Mixer Mixer 6: Kneader

7: roll press 8: Kenvey belt

Method for producing coal briquettes of the present invention for achieving the above object is a step of mixing 3 to 15 parts by weight of dust containing 20 to 60% CaO with respect to 100 parts by weight of pulverized coal, molasses 5 ~ to 100 parts by weight of pulverized coal of the mixture Mixing 15 parts by weight,

And forming the secondary mixture into coal briquettes.

Hereinafter, the present invention will be described in detail.

The present inventors confirmed that the use of molasses as a binder for pulverized coal and dust containing CaO as a curing agent of the binder can proceed the curing by molasses-calcium chemical reaction to enhance the strength of the coal briquettes. By the way, in order to ensure these uniform and high strength, the mixing order of these raw materials is important.

According to the present invention, the pulverized coal and the CaO-containing dust must be mixed first and the molasses binder must be mixed thereto. If three raw materials are mixed at the same time, or if pulverized coal and molasses are mixed and then mixed with CaO-containing dust later, a uniform mixture cannot be obtained and the strength becomes poor. If the pulverized coal, which is a solid powder, and the molasses, which is a liquid, are mixed, then the CaO-containing dust, which is a solid powder, is cured before the dust is uniformly distributed by the molasses-calcium reaction.

On the other hand, when a mixture of solid pulverized coal and CaO-containing dust is mixed followed by liquid molasses, a molasses-calcium reaction occurs, and it has been found through experiments that the reaction does not prevent the uniform mixing of liquid molasses.

Based on these studies, the present invention will be described according to the process sequence.

[First Mixing: Mixing of Pulverized Coal and CaO-containing Dust]

In the present invention, first, pulverized coal and CaO-containing dust are mixed.

The pulverized coal used in the present invention is made from coal which is not used in the particle size regulation in the Finex and Korex processes. That is, although 8 mm or less is used, Preferably it is good to grind | pulverize 8 mm or less pulverized coal to a particle size of 4 mm or less, and to use it. Coal having a particle size larger than 4 mm may crack due to the pressure applied during molding, thereby reducing the strength of coal briquettes.

CaO-containing dust is mixed with such pulverized coal, and mixed as uniformly as possible.

CaO-containing dust controls the moisture of pulverized coal and contributes to the strength of coal briquettes due to the chemical reaction of molasses binder and calcium-saccharide salt bond. Therefore, 20% or more of CaO is preferable for dust. If the content of CaO in the dust is less than 20% may be due to the lack of calcium-saccharide bonds. If the content of CaO in the dust is high, the addition amount may be adjusted accordingly so that the upper limit of CaO in the dust is not limited. The dust containing a large amount of CaO is typically steelmaking dust. Steelmaking dust is composed of C component which can be used as a heat source and reducing agent, Fe compound which can be used as iron source, Ca compound and other components which can be used as an auxiliary material. Therefore, since T-Fe, C, etc. can be recycled from coal briquettes as an active ingredient, it is most preferable to use such dust. Considering the effective use of the active ingredient with CaO, the content of CaO in the dust is preferably 20 to 60%. More preferably, it is 20 to 40%, and the example is steelmaking dust. If the content of CaO in the dust exceeds 40%, the amount of the active ingredient is less.

In this invention, 3-15 weight part of CaO containing dust compounding quantity is preferable with respect to 100 weight part of pulverized coal. When the content of CaO-containing dust is less than 3 parts by weight, the calcium-saccharide salt bond with molasses is not sufficiently exhibited, and the strength of the coal briquettes is lowered. Moreover, when the compounding quantity of CaO containing dust exceeds 15 weight part, ash component may become high in a coal briquette, and may not fully play the role as a fuel in a melting furnace.

CaO-containing dust is preferably 1 mm or less, and most preferably, the particle size of 0.3 mm or less has a weight ratio of 50% by weight or more. The smaller the particle size of the CaO-containing dust, the larger the specific surface area. Therefore, the chemical reaction of the calcium-saccharide salt bond to harden the pulverized coal-molasses mixture also occurs more smoothly. When the particle size of the CaO-containing dust is larger than 1mm and the particle size distribution of 0.3mm or less is less than 50% by weight, sufficient chemical reactions do not occur, which causes a decrease in the strength of coal briquettes.

[Secondary Mixing: Molasses Binder Mixture in Mixture of Pulverized Coal and CaO-containing Dust]

The molasses binder is mixed with the pulverized coal-CaO-containing dust mixture. The molasses binder is preferably used that contains 70 to 85% by weight solid content. The reason is that when the solid content of the molasses binder is less than 70% by weight, the sugar component exhibiting the binder properties is low, and the moisture content is high, which may cause a problem of deterioration of the strength of the coal briquettes. In some cases, the viscosity of molasses is high, which may cause a problem in uniform mixing.

When mixing molasses binder with a pulverized coal-CaO containing dust mixture, it is preferable to use 5-15 weight part with respect to 100 weight part of pulverized coal. If the amount of molasses is less than 5 parts by weight, there is not enough molasses binder in the powdered coal, which may cause a problem in the coal briquette strength. If the amount of the molasses exceeds 15 parts by weight, problems such as adhesion during mixing with the powdered coal-CaO-containing dust mixture may occur. And economic loss. In addition, when the viscosity of the molasses is high, in order to control it, a diluent mixture of a certain amount of water may be used.

A method of manufacturing such coal briquettes will be described in more detail with reference to FIG. 1.

3-15 parts by weight of CaO-containing dust is extracted from the dust bin 2 with respect to 100 parts by weight of pulverized coal of 4 mm or less in the pulverized coal bin 1 and mixed uniformly in the primary mixer 4. It is preferable to use a mixer mixer (Twin SCREW method) for the primary mixer, since it can achieve uniform mixing.

To the primary mixed pulverized coal-CaO-containing dust mixture, 5 to 15 parts by weight of a molasses binder is added to 100 parts by weight of pulverized coal and mixed uniformly in the secondary mixer 5. Secondary mixers are also recommended to use a mixer mixer for even mixing. In the secondary mixer, the pulverized coal-steel dust mixture and the molasses binder are mixed, resulting in the chemical reaction of the calcium-saccharide salt bond.

In general, the residence time of the mixture in the mixer mixer is very short (1 to 3 minutes), so the chemical reaction of the calcium-saccharide linkage is limited.

Therefore, extending the residence time of the mixture increases the strength of the coal briquettes if the curing reaction by the chemical reaction of the calcium-saccharide salt bond is further advanced. In the present invention, for this purpose, the secondary mixture of molasses binder mixed with a mixture of pulverized coal and CaO-containing dust is stirred for a predetermined time to allow calcium-saccharide salt chemical reaction to proceed. Such a long time stirring is preferably performed in a kneader (6), which is a kind of kneader rather than a mixer.

The kneader 6 of the kneader is composed of a vertical cylindrical cylinder having a central axis to which a wing is attached, and stirs the contents. Therefore, when the secondary mixture in which the molasses binder is mixed with the mixture of pulverized coal and CaO-containing dust is stirred in a kneader, the curing efficiency of the molasses binder by the calcium-saccharide salt bond is increased. The blades are arranged to have a function of stirring the mixture as the shaft rotates, and the stirring time of the mixture can be controlled by adjusting the level of the mixture in the kneader 6. According to the experiment of the present invention, when the stirring time is less than 5 minutes, the stirring time may be insufficient, and the strength of the coal briquettes may be lowered. When the stirring time exceeds 40 minutes, the mixture of fine coal-CaO-containing dust-molasses dries. As a result, the strength during molding may decrease. Therefore, 5-40 minutes are suitable for the stirring time range.

The pulverized coal-molasses-CaO-containing dust mixture with appropriately increased curing efficiency is pressurized to a conventional pressure in the roll press 7 to produce coal briquettes. The coal briquettes are transferred to the coal briquettes 9 at normal temperature without being heated and dried when being transferred to the conveyor belt. On the other hand, the unsatisfactory coal briquettes are separated on the Kenvey belt 8 and the calculated amount is reused to go through the recovery bin 10 to the molding mixture in the secondary mixer 5.

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

EXAMPLE

Steelmaking dust for controlling water content was mixed uniformly in Muller Mixer with respect to 100 parts by weight of Mt. thorley pulverized coal (water content: 8-12%) of 3.4 mm or less. The molasses binder is uniformly mixed in the Muller Mixer in a homogeneously mixed pulverized coal-steel dust mixture, and then stirred in a kneader for 10 minutes to increase the curing efficiency, and then the Briquetter Roll Press is machined at room temperature. It was pressurized using a pillow shaped coal briquettes having a diameter of 63.5 mm, a width of 25.4 mm, and a thickness of 19.1 mm. Table 1 below shows the analysis results of the main components of the steelmaking dust used in the present invention, Table 2 shows a comparative example for comparison with the embodiment of the present invention.

Kinds Composition (% by weight) T-Fe (%) C (%) CaO (%) moisture(%) Steelmaking Dust A 25.3 2.4 33.3 2.4 Steelmaking Dust B 45.7 2.5 30.9 1.1 Steelmaking Dust C 60.6 4.4 7.0 0.4 Steelmaking Dust D 35.9 30.4 3.8 3.0

Experimental Example Pulverized coal (part by weight) of 3.4 mm or less additive Molasses Binder Usage (part by weight) Kinds Usage (part by weight) Inventive Example 1 100 Steelmaking Dust A 10 8 Inventive Example 2 100 Steelmaking Dust B 10 8 Comparative Example 1 100 - - 8 Comparative Example 2 100 Calcium carbonate 10 8 Comparative Example 3 100 Steelmaking Dust C 10 8 Comparative Example 4 100 Steelmaking Dust D 10 8

Inventive Example 1 of Table 2, after mixing 10 parts by weight of steelmaking dust A uniformly with respect to 100 parts by weight of pulverized coal, 8 parts by weight of molasses binder is mixed with a binder to form a coal briquette at room temperature. Inventive Example 2 was prepared by the same method as inventive example 1 by mixing 10 parts by weight of steelmaking dust B as an additive.

In Comparative Example 1, 8 parts by weight of molasses binder was added as a binder based on 100 parts by weight of pulverized coal, and in Comparative Example 2, 8 parts by weight of 10 parts by weight of calcium carbonate (CaCO3) was uniformly mixed. Coal briquettes were manufactured by pressing at room temperature using a negative molasses binder as a binder. In Comparative Example 3, 10 parts by weight of steelmaking dust C was uniformly mixed with 100 parts by weight of pulverized coal, and then 8 parts by weight of molasses binder was mixed and pressure molded at room temperature to produce coal briquettes. In Comparative Example 4, 10 parts by weight of steelmaking dust D was uniformly mixed with 100 parts by weight of pulverized coal, and then 8 parts by weight of molasses binder was mixed and pressure molded at room temperature to produce coal briquettes.

Coal briquettes prepared according to Inventive Examples (1, 2) and Comparative Examples (1 to 4) as described above were immediately measured drop strength and dust generation rate. Then, the high temperature strength was measured at 1,000 ° C.

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).

In the high temperature strength test, two pieces of coal briquettes were injected four times at intervals of 10 minutes under conditions in which nitrogen gas was passed at 2 L / min through an inert atmosphere set at 1,000 ° C. After the final coal briquette sample was put into the reactor, 10 minutes later, the coal briquette sample was extracted and cooled to measure a particle size distribution. The high temperature strength was evaluated by the ratio of coal briquettes having a size of 16 mm or more as shown in Equation (3).

Table 3 below is to evaluate the drop strength, generation rate and high temperature strength of the coal briquettes prepared according to the invention examples and comparative examples of Table 2.

Experimental Example Drop strength (%) Minute occurrence rate (%) High temperature strength (%) Inventive Example 1 94.5 4.7 60.3 Inventive Example 2 97.0 2.5 67.6 Comparative Example 1 16.1 75.9 34.5 Comparative Example 2 35.1 57.5 51.2 Comparative Example 3 71.6 17.4 61.3 Comparative Example 4 65.4 24.3 56.8

As can be seen in Table 2, in the case of Inventive Example (1.2) satisfying the scope of the present invention, good coal briquettes having a drop strength of 90% or more, a particle generation rate of 5% or less, and a high temperature strength of 60% or more were produced. . On the other hand, in the case of Comparative Examples (1 to 4) that do not satisfy the scope of the present invention, it can be seen that the drop strength and the generation rate of the coal briquettes are low compared to the case of the above-described invention.

As described above, the coal briquettes of the present invention can not only be used without drying pulverized coal, but also can be recycled environmentally friendly CaO-containing dust generated in steel mills in the steelmaking process itself, and can be press-molded at room temperature because molasses is used as a binder. It can reduce the manufacturing cost, easy handling, and can produce coal briquettes having excellent initial strength without heating is a useful effect. In addition, it is possible to provide coal briquettes capable of securing the strength required by the new steelmaking methods FINEX and COREX processes, thereby improving the competitiveness of the new steelmaking methods FINEX and COREX processes. It has a useful effect.

Claims (5)

Mixing 3 to 15 parts by weight of dust containing 20 to 60% of CaO with respect to 100 parts by weight of pulverized coal, mixing 5 to 15 parts by weight of molasses to 100 parts by weight of pulverized coal of the mixture, A method for producing coal briquettes having excellent strength comprising forming the secondary mixture into coal briquettes. The method of claim 1, wherein the dust is steelmaking dust, the method of producing coal briquettes having excellent strength, characterized in that the content of CaO 20 to 40%. The method of claim 2, wherein the steelmaking dust is less than 1mm, 0.3mm or less particle size of less than 50% by weight, characterized in that the manufacturing method of coal briquettes having excellent strength. The method of claim 1, wherein the mixture is stirred for 5 to 40 minutes before molding to increase the curing rate of the mixture. The coal briquettes of claim 1 to 4, wherein the coal briquettes are applied to a molten steel reducing process having a drop strength of 90% or more, a generation rate of 5% or less and a high temperature strength of 60% or more. Way.