KR20020050084A - Coal briquette having superior strength and briquetting method thereof - Google Patents

Abstract

PURPOSE: A method for producing coal briquette having superior strength for Corex process is provided, which is characterized in that lime is mixed with coke breeze to remove moisture of coke breeze. Therefore drying process of coke breeze is not necessary. And molasses is added to increase strength of coal briquette. CONSTITUTION: According to the method, the coal briquette is made by the following steps: mixing 100 parts by weight of coke breeze and 1-5 parts by weight of lime; aging the mixture; adding 7-15 parts by weight of molasses, based on 100 parts by weight of coke breeze into the mixture; agitating the mixture; and (e) molding the mixture. The size of lime is less than 1mm wherein the particle size fraction less than 0.3mm occupies 0.5 of total lime. Obtained coal briquette is used to metallurgical process.

Description

Coal briquettes having excellent strength and manufacturing method thereof {Coal briquette having superior strength and briquetting method

The present invention relates to a coal briquette for metallurgy, and more particularly, to a coal briquette having excellent strength by a chemical reaction of calcium saccharide bonds while omitting the drying process of the pulverized coal due to the exothermic reaction of pulverized coal and moisture of quicklime. . 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-reduced steelmaking 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 instead of coke. Coal used as a fuel is collected in the dust collector and is not sufficiently burned in the smelter in the case of pulverized coal of 8mm or less, and if it is excessive, the use of pulverized coal is limited in the steelmaking process because it causes imbalance in the process. A considerable amount of steel coal currently used is composed of fine powder of less than about 8mm.

Pulverized coal is limited to use in the melt reduction process, and has been converted to Pulverized Coal Injection (PCI) or coke coal. However, because the nature of the coal for Korex is prescribed, there is a limit to the use of unused pulverized coal for other purposes. Therefore, there is a need for the development of a technique for producing coal briquettes by agglomerating fine coal in an appropriate manner.

Until now, there is no known technique for making pulverized coal into coal briquettes and applying them to the FINEX and COREX processes.

However, a 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). In this technique, coal tar and pitch binders are heated to a softening temperature (about 150 ℃) or more, and then melted, and then a certain amount is added to the pulverized coal, mixed sufficiently, and then press-molded to form a binder in a molten state. It is a technique of manufacturing coal briquettes by cooling below softening temperature. The coal briquettes exhibit sufficient mechanical strength for transport handling because the pitch binder is melted by heating and the coal particles are firmly bound by cooling the 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. Since this temperature is near the softening temperature of the pitch binder, the pitch binder used in the coal briquettes is softened again and sticks to the coal briquettes. It becomes difficult to handle large quantities.

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 during the manufacture of 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 an additive and molasses binder for moisture content control, excellent low temperature stability, high strength, easy to handle large quantities, and a method for manufacturing the coal briquettes without a drying process or a heating process. To provide, the purpose is.

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

* Description of the symbols for the main parts of the drawings *

1, 2, 5, 10 ... empty 3, 6. mixer mixer

4 ...... Save Hopper 7 ..... Kneader

8 ...... roll press

Coal briquettes of the present invention for achieving the above object,

Based on pulverized coal and 100 parts by weight of pulverized coal, quicklime: 1 to 5 parts by weight and molasses: 7 to 15 parts by weight.

In addition, the coal briquette manufacturing method of the present invention,

Mixing 1 to 5 parts by weight of quicklime to 100 parts by weight of pulverized coal,

Aging the mixture,

Mixing molasses 7 to 15 parts by weight based on 100 parts by weight of pulverized coal to the aged mixture,

Stirring the mixture containing the molasses,

It comprises a step of molding the stirred mixture into coal briquettes.

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 the molten steelmaking process while bulking the moisture of the pulverized coal without drying it. 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 + H ₂ O → Ca (OH) ₂

In addition, the use of molasses as a binder in the raw materials of pulverized coal and quicklime, it was confirmed that the quicklime and molasses can prevent the improvement of the strength of the coal briquettes and the melting of molasses due to the chemical reaction of calcium saccharide bond. The present invention will be described by dividing the coal briquettes and a manufacturing method thereof.

[Grenade]

The coal briquettes of the present invention are composed of (1) pulverized coal: 1 to 5 parts by weight, and (3) molasses: 7 to 15 parts by weight based on (1) pulverized coal and 100 parts by weight of pulverized 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 the particle size of the pulverized coal is too large, the pressure applied during molding increases, which may cause cracking of the coal briquettes and reduce the strength of the coal briquettes. More preferably, it is preferable to use about 80% or more of pulverized coal of about 4 mm or less.

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 amount of the quicklime, the fine coal is about 6-12% 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 enhances the strength of coal briquettes by removing calcium hydrate from coal dust. 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. In addition, due to the chemical reaction of the calcium saccharide bonds with molasses plays a role in improving the strength of coal briquettes and molasses dissolved in water.

In the present invention, the quicklime is preferably used less than about 1mm, and most preferably, less than about 1mm, the particle size of less than about 0.3mm to use more than 50% by weight ratio. The quicker the lime, the larger the specific surface area is, the more the reaction with water in the pulverized coal, the conversion of the slaked circuit is advantageous. If the particle size is larger than 1mm and the particle size distribution of less than 0.3mm is less than 50%, sufficient chemical reaction with moisture in the pulverized coal may not occur, and unreacted quicklim may remain in the coal briquettes even after molding. Unreacted quicklime in the coal briquettes causes chemical reactions to come into contact with moisture in the air, thereby reducing the strength of coal briquettes.

In the present invention, the quicklime is preferably mixed 1-5 parts by weight with respect to 100 parts by weight of pulverized coal. When the content of quicklime is less than 1 part by weight, it does not play a role of sufficiently removing moisture and does not sufficiently exhibit the calcium saccharide bond with molasses, thereby reducing the strength of coal briquettes. Moreover, when the compounding quantity of quicklime exceeds 5 weight part, the physical property of the coal briquettes will fall.

③ molasses

In the present invention, instead of using a solid material such as coal tar or pitch, which is difficult to handle in large quantities, molasses that is easy to handle in large quantities by maintaining viscosity at room temperature is used. Molasses preferably has a solid content of 70 to 85% by weight. If the molasses content of the molasses is less than 70% by weight, there is little sugar component exhibiting the binder properties, the moisture content is high, the strength of the coal briquettes may be lowered, if the solids content exceeds 85% by weight the molasses viscosity High and may cause problems with uniform mixing. When the molasses viscosity is high, a diluent in which water is mixed within 10% of the molasses weight ratio may be used to control the molasses.

It is preferable to use 7-15 weight part of compounding quantities of molasses with respect to 100 weight part of pulverized coal. If the amount of molasses is less than 7 parts by weight, the molasses binder may not be sufficient in the powdered coal, which may cause a problem in the strength of the coal briquettes. .

[Manufacturing method of coal briquettes]

The present inventors have found that the strength of the coal briquettes is affected by the mixing order and processing conditions of these raw materials when producing coal briquettes composed of pulverized coal, quicklime, and molasses. The present invention completed based on these studies will be described according to the process sequence with reference to FIG.

[Mixing and Aging of Pulverized Coal and Quicklime]

In the present invention, first, pulverized coal and quicklime are mixed. Quicklime is mixed 1 to 5 parts by weight based on 100 parts by weight of pulverized coal. Mixing pulverized coal and quicklime is preferable because a general mixer mixer (Twin Screw method) can be used to achieve uniform mixing. The mixing at this time is enough uniformly mixed in about 1 to 3 minutes.

After mixing as described above, it is recommended to ripen so that quicklime is converted into hydrated lime as in Scheme 1 above. In the mixer, it is converted into a calcination but the residence time is short and it is limited. Therefore, long-term storage in a storage vessel such as a hopper induces the reaction of Scheme 1. At this time, the ripening time is preferably within about 2 minutes or more within 2 hours. If the aging time is less than 2 minutes, unreacted quicklime remains and the strength of the coal briquettes is feared. If the aging time exceeds 2 hours, it is difficult to secure the yield during continuous production due to the increase of residence time.

[Mixing and stirring primary mixture and molasses]

Molasses is mixed with the primary mixture 7 to 15 parts by weight based on 100 parts by weight of pulverized coal. Secondary mixers are also recommended to use a mixer mixer for even mixing. In the second mixer, some unreacted quicklime combines with the water in the molasses and is converted to hydrated, and the chemical reaction of calcium saccharide bond occurs. However, due to the short residence time, the chemical reaction of the calcium saccharide linkage is inevitably limited. Molasses in the secondary mixer is preferred because it can increase the mixing efficiency by spraying through the injection nozzle.

If the residence time of the mixture is extended, the curing reaction by the chemical reaction of calcium saccharide bonds is further advanced, and the strength of coal briquettes is increased. In the present invention, for this purpose, the secondary mixture is stirred for a predetermined time to proceed the calcium-saccharide salt chemical reaction. Such a long time stirring is preferably performed in a kneader (6) of kneader, which is a kind of kneader rather than a mixer.

The kneader 6, which is a kneader, is composed of a vertical cylindrical cylinder having a central axis to which wings are attached, and stirs the contents. Thus, stirring the secondary mixture in a kneader increases the curing efficiency due to calcium saccharide bonds. 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 2 minutes, the stirring time may be insufficient, and the strength of the coal briquettes may be lowered. When the stirring time exceeds 50 minutes, the mixture may be dried to reduce the strength during molding. . Therefore, the stirring time range is preferably 2 minutes to 50 minutes.

[Molding]

By stirring as described above, the mixture of which the curing efficiency is appropriately increased is pressurized to a normal pressure in the roll press 7 to produce coal briquettes. When the coal briquettes are transferred to the conveyor belt, the coal briquettes are transferred to a coal briquette 9 without being heated and dried at room temperature.

On the other hand, the unsatisfactory coal briquettes are separated on the Kenvey belt 9 and reused in the calculated amount to go to the forming mixture in the secondary mixer 6 via the recovery bin 11.

Thus, the manufacturing process of the coal briquette which passes through the roll press from the pulverized coal bin 1 takes about 6 minutes-about 3 hours.

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

Example 1

First, uniformly mix quick-acting lime to control the water content in the fine coal less than 3.4mm, and then evenly mix the molasses as a binder, and press it with a briquetter roll press at room temperature to measure 63.5mm in diameter, 25.4mm in width and 19.1 in thickness. A pillow shaped coal briquettes of mm were prepared. 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 Sugar addition amount (part by weight) Kinds Usage (part by weight) Inventive Example 1 100 quicklime 3 10 Inventive Example 2 100 quicklime 2 8 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

In Table 1, Inventive Example (1-2) is a mixture of 2 to 3 parts by weight of quicklime with respect to 100 parts by weight of pulverized coal, and then mixed with 8 to 10 parts by weight of molasses binder to press-molded at room temperature to produce coal briquettes. It is.

In Comparative Example 1, 10 parts by weight of the molasses binder was added to 100 parts by weight of pulverized coal. In Comparative Example 2, 3 parts by weight of calcium carbonate (CaCO ₃ ) was uniformly mixed with 100 parts by weight of pulverized coal, and then mixed with 10 parts by weight of molasses binder to press-molded at room temperature to produce coal briquettes. 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 molasses binder to press-molded at room temperature to produce coal briquettes. In Comparative Example 4, 1 part by weight of quicklime was uniformly mixed with 100 parts by weight of pulverized coal, and then mixed with 6 parts by weight of molasses binder to press-molded at room temperature to produce coal briquettes.

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 89.7 8.8 Inventive Example 2 80.5 15.5 Comparative Example 1 20.0 71.6 Comparative Example 2 15.1 75.5 Comparative Example 3 69.6 23.3 Comparative Example 4 31.9 58.8

As can be seen in Table 2, in the case of Inventive Example (1-2) that satisfies the scope of the present invention, the coal briquettes having excellent strength are manufactured with a drop strength of 80% or more and a particle generation rate of 16% or less. In the case of Comparative Examples 1-4, which do not satisfy the scope of the present invention, it is understood that the drop strength is low and the dust generation rate is higher than that of the above Inventive Example, resulting in low strength of coal briquettes.

Example 2

Additives for controlling the water content in the fine coal less than 3.4mm (Australia: MT.Thorley) were first uniformly mixed in Muller Mixer for 1 minute, and then aged. Molasses was added to the matured mixture as a binder and mixed in Muller Mixer for 3 minutes, and then stirred in a kneader for a certain time to increase the curing efficiency. , Pillow shaped briquettes having a width of 25.4 mm and a thickness of 19.1 mm were prepared.

division Pulverized coal additive molasses Additive-pulverized coal aging time (min) Stirring time (min) of molasses-additive-pulverized coal mixture Usage (part by weight) Moisture content (wt%) Kinds Addition amount (part by weight) Content less than 3mm (part by weight) Addition amount (part by weight) Inventive Example 1 100 9.7 quicklime 3 84 8 10 5 Inventive Example 2 100 9.6 quicklime 3 78 8 30 5 Inventive Example 3 100 9.7 quicklime 3 78 8 60 10 Inventive Example 4 100 9.1 quicklime 3 81 8 5 7 Inventive Example 5 100 9.4 quicklime 3 60 8 5 12 Inventive Example 6 100 8.5 quicklime 3 95 8 5 20 Inventive Example 7 100 14.5 quicklime 3 95 10 10 10 Comparative Example 1 100 8.9 quicklime 3 78 8 0 5 Comparative Example 2 100 8.1 quicklime 3 78 8 One 60 Comparative Example 3 100 8.7 quicklime 3 15 8 10 5 Comparative Example 4 100 4.9 quicklime 3 78 8 10 5 Comparative Example 5 100 8.5 - - - 10 0 10 Comparative Example 6 100 9.4 Slaked lime 3 100 8 10 5 Comparative Example 7 100 8.2 Calcium carbonate 3 92 10 One 10 Comparative Example 8 100 7.1 quicklime One 95 6 One 10

In Table 3, Inventive Example (1-7) was made by uniformly mixing quicklime with pulverized coal, then maturing, and then mixing molasses, stirring in a kneader, and then molding the coal briquettes at room temperature.

In Comparative Example (1), the quick coal was uniformly mixed with pulverized coal, molasses was immediately mixed without aging, stirred in a kneader, and press-molded at room temperature to produce coal briquettes.

Comparative Example (2) uniformly mixed quicklime with pulverized coal, aged for 1 minute, mixed molasses for 60 minutes in a kneader and press-molded at room temperature to produce coal briquettes.

In Comparative Example (3), coal briquettes were manufactured by the same method as inventive example (1), using quicklime having a particle size distribution of 0.3 mm or less in 15% by weight.

In Comparative Example (4), coal briquettes were manufactured by the same method as inventive example (1) using 4.9% by weight of pulverized coal.

In Comparative Example (5), only molasses was mixed with pulverized coal, stirred for 10 minutes in a stirrer, and molded under pressure at room temperature to produce coal briquettes.

In Comparative Example (6), coal briquettes were manufactured by the same method as inventive example (1) using calcined lime in pulverized coal.

In Comparative Example (7), calcium carbonate was uniformly mixed with pulverized coal, aged for 1 minute, molasses was mixed, stirred for 10 minutes in a kneader, and press-molded at room temperature to produce coal briquettes.

In Comparative Example (8), uniformly mixed quicklime with mibutane and then aged for 1 minute, the molasses was mixed, stirred in a kneader and press-molded at room temperature to produce coal briquettes.

The drop strength and firing rate of the invention examples and the comparative examples were measured immediately after manufacture and after 24 hours, and the results are shown in Table 2.

division Right after manufacturing After 24 hours Drop strength (%) Incidence rate (%) Drop strength (%) Incidence rate (%) Inventive Example 1 97.2 2.6 84.6 11.6 Inventive Example 2 95.1 4.1 82.5 13.7 Inventive Example 3 94.4 4.5 86.3 10.8 Inventive Example 4 95.8 3.7 81.5 14.9 Inventive Example 5 95.3 4.1 77.4 18.9 Inventive Example 6 88.2 9.3 80.9 17.7 Inventive Example 7 94.5 4.3 81.2 13.2 Comparative Example 1 91.7 7.0 69.9 23.9 Comparative Example 2 69.3 25.0 56.8 37.5 Comparative Example 3 72.1 22.4 62.4 31.0 Comparative Example 4 55.2 38.3 49.3 42.7 Comparative Example 5 20.0 71.6 33.0 58.6 Comparative Example 6 73.0 21.6 57.5 35.8 Comparative Example 7 15.1 75.5 42.9 47.8 Comparative Example 8 31.9 58.8 73.6 21.8

As shown in Table 4, in the case of Inventive Examples (1 to 7), excellent initial strength was ensured with a drop strength of 88% or more and a firing rate of 10% or less, and a drop strength of 77% or more even after 24 hours had elapsed. Good coal briquettes were produced with an incidence of 19% or less.

On the contrary, in the case of Comparative Examples (1 to 7), the drop strength was lowered and the generation rate was increased, so that it was not suitable for use in the melt reduction furnace, and thus poor quality was evaluated as coal briquettes.

Table 5 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 (8)

Coal briquettes having excellent strength composed of quicklime: 1 to 5 parts by weight and molasses: 7 to 15 parts by weight with respect to pulverized coal and 100 parts by weight of this pulverized coal. The coal briquette having excellent strength according to claim 1, wherein the coal briquettes have a drop strength of 70% or more and a generation rate of 20% or less. Mixing 1 to 5 parts by weight of quicklime to 100 parts by weight of pulverized coal, Aging the mixture, Mixing molasses 7 to 15 parts by weight based on 100 parts by weight of pulverized coal to the aged mixture, Stirring the mixture containing the molasses, Method for producing coal briquettes having excellent strength comprising the step of molding the stirred mixture into coal briquettes. The method of claim 1 or 3, wherein the fine coal has a water content of 6 to 15%. The coal briquette having excellent strength according to claim 1 or 3, wherein the quicklime is 1 mm or less and a particle size of 0.3 mm or less is 50% by weight or more. The method for producing coal briquettes having excellent strength according to claim 3, wherein the aging is performed for 2 minutes to 2 hours to convert quicklime into slaked lime. The method of claim 3, wherein the stirring is performed for 2 to 50 minutes to increase the curing rate of the mixture. 4. The method for producing coal briquettes having excellent strength according to claim 3, wherein the molding omits a heat drying step after the press molding.