COAL BRIQUETTE HAVING SUPERIOR STRENGTH AND BRIQUETTING METHOD THEREOF BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a briquette used in metallurgy. More particularly, the present invention relates to a briquette which is produced from fine coal by using quicklime and molasses, thereby being capable of dispensing with the process of drying the fine coal through an exothermal reaction of moisture contained in the fine coal with the quicklime, while exhibiting superior strength by virtue of bonds of calcium saccharate formed through a chemical reaction between the quicklime and the molasses.

The present invention also relates to a method for producing such a briquette. Since the briquette prepared according to the invention has superior physical strength, it is applicable to a smelting reduction iron making process, which is a newly introduced iron making process.

Description of the Related Art It is known that FINEX and COREX processes, or smelting reduction iron making processes, have advantages in terms of fuel availability in that instead of coke, coal is used as a fuel for a smelting furnace. However, as for a fuel, when the coal is fine coal having a particle size of 8 mm or less, it fails to undergo complete combustion in a

melting furnace and is frequently trapped in a collector.

Furthermore, when the fine coal is trapped in the collector in an excessive amount, the thermal balance of the process is lost, thereby causing various problems with the process.

Therefore, use of such fine coal should be limited in the iron making process. However, coals currently used for iron making processes largely include fine coal of not larger than 8 mm.

Use of fine coal has limits in its application in the iron making process, so having been mainly employed either for pulverized coal injection (PCI) or as a coal for coke making.

However, since the characteristics of coals which can be used in the COREX process are specified, there are limitations to uses of such coal in terms of its application to purposes other than COREX. Thus, it is desirable to obtain a method of making a briquette by agglomerating fine coal in an appropriate way. However, as to the state of the art so far, no successful technology to make fine coals into briquette applicable to the new iron making processes of FINEX and COREX has been found.

For example, U. K. Pat. No. GB2227024A and U. S. Pat. No.

4,738,685 disclose methods of making briquettes using a mixture of fine coal, molasses and an inorganic hardener. In these methods, briquettes should be hardened at room temperature for 1 to 3 days or in an oven at a temperature of 200 to 300°C for 1 hour to increase the strength of briquettes since the process efficiency of the hardening step is poor, which is directly connected to a low initial strength of

briquettes.

When a large amount of briquettes are employed in a process, such as smelting reduction process, the briquettes are transported and stored with the aid of a conveyer belt.

If the briquettes do not have a sufficient initial strength, they are broken during transportation using the conveyer belt.

To avoid such breakages, briquettes have to be heated above 200°C after molding. However, this additional heating process requires large scale heat drying equipment, creating an economic burden of high costs and low productivity in a manufacture of briquettes.

Meanwhile, a method of making briquettes using fine coal for a manufacture of cokes is disclosed in Japanese Pat. Laid- open Publication No. Heisei 7-97576 (Pub. Date: April 11, 1995).

According to the method, a binder such as coal tar or pitch is heated to a softening temperature (about 150°C) or higher to be melted. Then, the melt is added to fine coal in an appropriate amount. The mixture is blended thoroughly and subjected to compression-molding by cooling the melted binder to below the softening temperature. Thus, a desired briquette is produced. Such a smelting by heat and a cooling of a binder cause coal particles to be strongly bonded to each other, conferring high strength and resistance to breakage during mechanical transportation. Such heating of the binder to a softening temperature, however, requires a large scale heating system, which emits hazardous gases making a working environment unsafe during operation. For prevention and

treatment of the hazardous gases additional expenses may be incurred.

Further, a smelting reduction iron making process needs more than several hundred tons of the briquettes every day.

Therefore, the briquettes should be piled up in the open for a period of time until they are used. In summer, a temperature outdoors is raised to 40 to 60°C by solar heat. Therefore, the binder of pitch having a softening temperature around such temperatures may be resoftened and cause sticking of the briquettes to one another, making them difficult to be handled by mechanical means.

Moreover, fine coal contains typically a lot of moisture. Briquettes made by compression molding the fine coal at room temperature have a problem in that the excessive moisture content reduces cold strength thereof. For this reason, the cited method of making a briquette has a low recovery rate, so an additional drying step is necessary, increasing an expense and lowering productivity.

SUMMARY OF THE INVENTION Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide briquettes having superior strength and an excellent stability at lower temperature, as well as being handled easily in large quantities, which is produced from fine coal using a molasses binder and an additive for regulating moisture content in the fine coal, without

requiring any additional drying or heating step for removing moisture in fine coal and a process for making the same.

Thus, in accordance with the present invention, the above and other objects can be accomplished by the provision of a briquette with high strength comprising 100 weight parts of fine coal, 1 to 5 weight parts of quicklime and 7 to 15 weight parts of molasses.

Further, in accordance with the present invention, the above and other objects can be accomplished by the provision of a method of making briquettes with superior strength, comprising the steps of: (a) mixing of 100 weight parts of fine coal with 1 to 5 weight parts of quicklime and aging the mixture; (b) mixing 7 to 15 weight parts of molasses with the aged mixture from step (a) and stirring it; and (c) compression-molding the stirred mixture from step (b) to form briquettes.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawing, in which: Fig. 1 is a schematic diagram showing a process of making a briquette according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a briquette with high strength comprising 100 weight parts of fine coal, 1 to 5 weight parts of quicklime and 7 to 15 weight parts of molasses.

The present inventors have conducted studies and researches to find a way of agglomerating fine coal to make briquettes without removing moisture therein, while ensuring high strength of the briquettes applicable to a smelting reduction iron making process. They finally found that moisture contained in fine coal can be removed through an exothermal reaction in which moisture and quicklime (CaO) are converted into slaked lime (Ca (OH) 2) as follows.

[Reaction 1] CaO + H2O ~ Ca (OH) 2 Also, it was found that when molasses is added, as a binder, to the mixture of fine coal and quicklime, it chemically reacts with the quicklime to produce bonds of calcium saccharate, whereby it is prevented from being dissolved in the moisture present in the mixture. Thus, it is possible to produce a briquette with high strength without performing any additional heat-drying process after a compression-molding process of producing briquettes. On the basis of the above findings and facts, the present invention

is formed.

The present invention is described in detail below.

The fine coal used in the present invention includes coal which is not applicable to the COREX process, according to particle size specifications of coal. It is normally recommended that coal having a particle size of not less than 8 mm is used in a typical COREX process, and thus, in the present invention fine coal having a particle size of less than 8 mm is used. Preferably, the fine coal which is used according to the present invention is one that is ground to a particle size of up to about 4 mm. When a particle size of the fine coal is too big, pressure applied to compression-molding briquetting is increased, which cause cracks in briquettes and consequently, deteriorates the strength thereof. More preferably, the distribution of fine coal having a particle size of up to about 4 mm is about 80 % or more in the total fine coal.

According to the invention, fine coal containing moisture is not subjected to a separate drying step. The moisture content in the fine coal is correlated to the added amount of quicklime. It is most preferable that fine coal contains about 6 to 12 % moisture considering the added amount of quicklime. When fine coal contains a small amount of moisture the reaction with quicklime takes place insufficiently, resulting in decreased strength of briquette. On the other hand, when fine coal contains too much moisture, molding of briquettes is not carried out effectively, thereby failing to ensure a good quality of

briquette.

According to the invention, the quicklime serves two functions to provide briquettes with high strength: one is that it removes moisture from the fine coal and the other is that it improves the strength of briquettes by formation of calcium saccharate bonds. The quicklime (CaO) removes moisture from fine coal through an exothermal reaction with moisture contained in the fine coal into slaked lime, as shown in the above Reaction 1. Also, the quicklime may chemically react with molasses to form calcium saccharate bonds, which improve the strength of briquettes. Further, by virtue of such formation of calcium saccharate bonds, molasses is prevented from being dissolved in moisture contained in fine coal.

According to the invention, the quicklime is added in an amount of 1 to 5 weight parts relative to 100 weight parts of fine coal. If the quicklime is added in an amount of less than 1 weight parts, it cannot sufficiently achieve the function of removing moisture from the fine coal through a reaction with moisture and also, cannot form calcium saccharate bonds by a reaction with molasses, thereby causing decreased strength of a briquette. If the quicklime is added in an amount of more than 5 weight parts, physical properties of the resulting briquettes are deteriorated.

The quicklime which can be used according to the present invention has preferably a particle size of up to about 1 mm.

It is most important that the quicklime has a particle size of up to about 1 mm and the distribution of quicklime having a

particle size of up to 0.3 mm is more than or equal to 50 % by weight. As the quicklime is smaller in size, its specific surface area is larger. The quicklime having a small particle size, thus, is advantageously converted to slaked lime by a reaction with moisture in fine coal. When the quicklime has a particle size of larger than 1 mm and the distribution of quicklime having a particle size of up to 0.3 mm is less than 50%, the reaction of the quicklime and moisture contained in fine coal takes place insufficiently, probably leaving unreacted quicklime in the resulting briquette. Such unreacted quicklime tends to react with moisture in the air, causing deterioration in the strength of briquettes.

According to the invention, molasses is used as a binder which can maintain its viscosity at room temperature and thus is readily handled in large quantities, instead of coal tar or pitch, solid material which is difficult to handle in large quantities.

The added amount of molasses according to the present invention is regulated to an amount of 7 to 15 weight parts relative to 100 weight parts of fine coal. When molasses is added in an amount of less than 7 weight parts, the strength of briquette is poor. When molasses is added in an amount of more than 15 weight parts, there might be a problem of stickiness upon mixing with fine coal.

Preferably, the molasses has a solid content of 70 to 85 % by weight, based on the total weight of molasses. If the solid content of the molasses is less than 70 % by

weight, the produced briquettes have a low strength because of lacking the saccharide content in the molasses, which exhibits an actual binding property. Also, a moisture content in the molasses is high, producing briquettes of deteriorated strength. If the solid content of molasses is more than 85 % by weight, viscosity of the molasses is increased, making homogenous mixing with other ingredients difficult.

When the molasses is too viscous, it may be diluted with not more than 10 % by weight of water based on the weight of the used molasses.

Also, the inventors have discovered that the strength of briquettes is affected by a mixing order, and they have developed a protocol with which raw materials comprising fine coal, quicklime and molasses according to the present invention are mixed and/or aged for making a briquette.

Thus, in accordance with another aspect, the present invention is directed to a method of making briquettes with superior strength, comprising the steps of: (d) mixing of 100 weight parts of fine coal with 1 to 5 weight parts of quicklime and aging the mixture; (e) mixing 7 to 15 weight parts of molasses with the aged mixture from step (a) and stirring it; and (f) compression-molding the stirred mixture from step (b) to form briquettes.

Figure 1 shows a series of steps for the process.

Firstly, fine coal was mixed with quicklime. The

quicklime was employed in an amount of 1 to 5 weight parts relative to 100 weight parts of fine coal. Preferably, the mixing was performed using a mixer (4: Twin Screw mode), to achieve a homogenous mixture. The mixing was performed for about 1 to 3 min.

After mixing, it is preferable that aging is performed so that the quicklime is converted to slaked lime, as shown in the above Reaction 1. Although the conversion of the quicklime into the slaked lime may be carried out in the mixer, the residence time in the mixer is relatively short and therefore, the aging is limited. Thus, a reservoir such as a hopper is employed for long-term storage, allowing the reaction of Reaction 1. At this time, the aging time is preferably about 2 min to 2 hr. If the time is less than 2 min, unreacted quicklime remains in the produced briquettes, so the strength of the briquettes may be deteriorated. If the time is more than 2 hr, productivity is decreased.

After a first mixture of fine coal and quicklime was aged, molasses was added to the mixture in an amount of 7 to 15 weight parts relative to 100 weight parts of fine coal.

At this time a mixer (5) can be also used. It is preferable that molasses is sprayed using a nozzle for injection, improving a mixing efficiency.

Meanwhile, when being mixed in the mixer, the quicklime may chemically react with the molasses to form calcium saccharate bonds and unreacted quicklime may react with moisture in molasses, being converted to slaked lime.

However, the chemical reaction between the quicklime and

molasses is limited due to a short residence time in the mixer.

However, if the residence time of the mixture in the mixer is longer, more calcium saccharate may be generated to promote increased hardening of briquettes, providing a briquette with increased strength. Thus, according to the present invention, the second mixture was stirred for a certain time so that the reaction for producing calcium saccharate proceeds. Preferably, the stirring process is performed for a long time using a kneader (denoted by the reference numeral 6 in Fig. 1, different from the one used in the above mixing step.

The kneader (6) has a shape of a cylinder, vertically positioned, including a central axis with wings attached, and stirring materials charged therein. The stirring of the second mixture in the kneader increases hardening efficiency owing to the formation of calcium saccharate bonds. The wings are arranged to function in stirring a mixture. The kneader regulates a stirring time for a mixture based on a volume of a mixture contained.

According to the invention, when the time for stirring is less than 2 min, the strength of briquettes is decreased and in case the time is more than 50 min, a mixture becomes dry so that the strength of briquettes can also be decreased.

Thus, the time for stirring is preferably 2 to 50 min.

The second mixture thus obtained which has an increased hardening efficiency is applied to a roll press (7) which applies an even pressure thereto to make a briquette with

superior strength.

In the present invention, the briquettes produced are transported using a conveyer belt (8) to a briquette bin (9) for storing them at room temperature, without a separate heat- drying step. Briquettes of poor quality are removed from the conveyer belt (8), transferred to a mixer (5) which carries a resting mixture via a recovery bin (10) and reused by repeating a series of stages.

It takes about 3 min to 3 hr to form a briquette through the steps from a fine coal bin (1) to the roll press (7).

Meanwhile, reference numbers 1,2 and 3 in Fig. 1 denote fine coal bin, quicklime bin and molasses bin respectively.

As described above, the invention provides briquettes formed through the steps of mixing fine coal with quicklime and aging the mixture, mixing molasses with the aged mixture and stirring it, in which liquid molasses can permeate the mixture thoroughly so as to form calcium saccharate bonds, thereby forming briquettes with superior strength.

Therefore, the briquettes produced according to method of the invention have a superior initial strength, and are therefore directly available for use, without undergoing a separate hardening stage.

On the other hand, the quicklime reacts very rapidly with moisture and with molasses. Therefore, either when fine coal is first mixed with molasses and then mixed with quicklime or when the above three raw materials are mixed at the same time, since the quicklime reacts too rapidly with

moisture and with molasses and hardens the ingredients, it is impossible to disperse homogenously the quicklime through the mixture. Accordingly, briquettes with superior strength cannot be obtained.

Hereinafter, the present invention will be described in detail, in conjunction with various examples. These examples are provided only for illustrative purposes, and the present invention is not to be construed as being limited to those examples.

Example 1 Following the composition ratios listed in Table 1 below, 2 specimens according to the present invention and 4 specimens as comparative examples were prepared. Fine coal not larger than 3.4 mm was homogenously mixed with quicklime for controlling water contents contained in the fine coal and then, mixed with molasses as a binder. The resulting mixture was compressed using Briquetter Roll Press at room temperature to form a pillow shaped briquette of 63.5 mm in diameter, 25.4 mm in width, and 19.1 mm in thickness.

Table 1 FineCoal Additive S3. 4 mm Amount Molasses (weight (weight (weight Examples part) Compound part) part) Ex.1100quicklime310 Ex.2 100 quicklime 2 8 Comp. Ex. 1 100--10 100 calcium 3 10 Comp. Ex. 2 carbonate Comp. Ex. 3 100 Slaked lime 3 10 Comp. Ex. 4 100 quicklime 1 6

In Table 1, the inventive 1 and 2 were briquettes prepared by homogenously mixing fine coal with 2 to 3 weight parts of quicklime, and then with 8 to 10 weight parts of molasses and compression-molding the resulting mixture at room temperature.

On the other hand, the briquette of Comparative Example 1 was prepared using 10 weight parts of molasses binder relative to 100 weight parts of fine coal. The Briquette of Comparative Example 2 was prepared by homogenously mixing 100 weight parts of fine coal with 3 weight parts of calcium carbonate (CaCO3), then with 10 weight parts of molasses and compression-molding the resulting mixture at room temperature.

The Briquette of Comparative Example 3 was prepared by homogenously mixing 100 weight parts of fine coal with 3 weight parts of slaked lime (Ca (OH) 2), then with 10 weight parts of molasses and compression-molding the resulting mixture at room temperature. The Briquette of Comparative Example 4 was prepared by homogenously mixing 100 weight parts of fine coal with 1 weight part of quicklime, then with 6

weight parts of molasses and compression-molding the resulting mixture at room temperature.

Immediately after molding, the briquettes were subjected to test to determine their shatter resistance and dust rate.

The test of shatter resistance was conducted by free dropping about 2 kg of briquttes from a height of 5 m to an iron board four times. Then, briquettes pieces larger than or equal to 10 mm after were weighed and the shatter resistance was calculated following the Equation 1 below. Briquettes pieces smaller than 6.3 mm after dropping were weighed and the dust rate was calculated following the Equation 2 below.

[Equation 1] Shatter resistance (%) = (total weight of briquettes pieces larger than or equal to 10 mm after dropping/total weight of the briquettes before dropping) x 100 [Equation 2] Dust rate (%) = (total weight of briquettes pieces smaller than or equal to 6.3 mm after dropping/total weight of the briquettes before dropping) x 100 The shatter resistance and dust rate of each of the briquettes prepared from the compositions of Table 1 are shown in Table 2 below.

Table 2 Examples Shatter Resistance (%) Dust Rate (%) Ex. 1 89.7 8.8 Ex. 2 80.5 15.5 Comp. Ex. 1 20. 0 71.6 Comp. Ex. 2 15.1 75.5 Comp. Ex. 3 69.6 23.3 Comp. Ex. 4 31.9 58.8

As shown in Table 2, Examples 1 and 2 of which the compositions are within the range of the present invention provided briquettes with superior strength, characterized by more than 80 % shatter resistance and less than 16 % dust rate. On the other hand, Comparative Examples 1 to 4 of which the compositions were out of the range according to the present invention provided briquettes with low shatter resistance and high dust rate, indicating low strength, as compared with the Examples according to the present invention.

Example 2 Fine coal more than or equal to 3.4 mm in particle size were homogenously mixed with an additive in a Muller Mixer for 1 min and aged for a certain time. After adding molasses as a binder to the aged mixture and mixing it for 3 min in the Muller Mixer, the mixture was transferred to a kneader and stirred for a certain time for increasing hardening efficiency. The resulting mixture was compression molded using a Briquetter Roller Press at room temperature. Pillow shaped briquettes 63.5 mm in diameter, 25.4 mm in width, and 19.1 mm in thickness were formed.

Table 3 Fine coal Additive Molasses Aging time Time for Moisture for Stirring of Amount Amount Amount Examples Content 0.3mm Additive Additive (weight Compound (weight (weight (weight (weight-Fine coal-Fine Coal %) part) part) %) part) (min) (min) Ex. 1 100 9.7 quicklime 3 84 8 10 5 Ex. 2 100 9.6 quicklime 3 78 8 30 5 Ex. 3 100 9.7 quicklime 3 78 8 60 10 Ex. 4 100 9.1 quicklime 3 81 8 5 7 Ex. 5 100 9.4 quicklime 3 60 8 5 12 Ex. 6 100 8.5 quicklime 3 95 8 5 20 Ex. 7 100 14. 5 quicklime 3 95 10 10 10 Comp. Ex. 1 100 8.9 quicklime 3 78 8 0 5 Comp. Ex. 2 100 8.1 quicklime 3 78 8 1 60 Comp. Ex. 3 100 8.7 quicklime 3 15 8 10 5 Comp. Ex. 4 100 4.9 quicklime 3 78 8 10 5 Comp. Ex. 5 100 8.5 10 0 10 Comp. Ex. 6 100 9.4 slaked lime 3 100 8 10 5 Comp. Ex. 7 100 8.2 CaCO3 3 92 10 1 10 Comp. Ex. 8 100 7.1 quicklime 1 95 6 1 10

In Table 3, briquettes of Examples 1 to 7 were prepared according to the present invention by homogenously mixing fine coal with quicklime, aging the mixture, mixing the aged mixture with molasses, stirring the mixture in a kneader, and compression-molding at room temperature.

On the other hand, the Briquette of Comparative Example 1 was prepared by homogenously mixing fine coal with quicklime, then with molasses without aging the mixture of fine coal and quicklime, and stirring the resulting mixture in a kneader, followed by compression-molding at room temperature.

The briquette of Comparative Example 2 was prepared by homogenously mixing fine coal with quicklime, aging the mixture for 1 min, mixing the mixture with molasses, stirring the mixture in a kneader for 60 min, and compression-molding the mixture at room temperature.

The briquette of Comparative Example 3 was prepared by a method similar to that of Example 1, but employing quicklime

containing a fraction with a particle size of not more than 0.3 mm in an amount of 15 % by weight.

The briquette of Comparative Example 4 was prepared by a method similar to that of Example 1, but employing fine coal having a moisture content of 4.9 weight percent.

The briquette of Comparative Example 5 was prepared by homogenously mixing fine coal with only molasses, stirring the mixture in a kneader for 10 min, and compression-molding the mixture at room temperature.

The briquette of Comparative Example 6 was prepared by a method similar to that of Example 1, but employing only fine coal and slaked lime.

The briquette of Comparative Example 7 was prepared by homogenously mixing fine coal with calcium carbonate, aging the mixture for 1 min, mixing the mixture with molasses, stirring the mixture in a kneader for 10 min., and compression-molding the mixture at room temperature.

The briquette of Comparative example 8 was prepared by homogenously mixing fine coal with quicklime, aging the mixture for 1 min, mixing the mixture with molasses, stirring the mixture in a kneader, and compression-molding the mixture at room temperature.

Shatter resistance and dust rate of each briquette formed according to the Examples and Comparative Examples was determined immediately and 24 hours after formation. The results were shown in Table 4.

Table 4 Immediately after Formation 24 hrs after Formation Shatter Dust Rate Shatter Dust Rate Examples Resistance (%) (%) Resistance (%) (%) Ex. 1 97. 2 2. 6 84.6 11.6 Ex. 2 95. 1 4. 1 82. 5 13. 7 Ex. 3 94. 4 4. 5 86. 3 10. 8 Ex. 4 95. 8 3. 7 81. 5 14. 9 Ex. 5 95. 3 4. 1 77. 4 18. 9 Ex. 6 88. 2 9. 3 80.9 17.7 Ex. 7 94. 5 4. 3 81. 2- 13. 2 Comp. Ex. 1 91.7 7.0 69.9 23.9 Comp. Ex. 2 69.3 25.0 56.8 37.5 Comp. Ex. 3 72.1 22.4 62.4 31.0 Comp. Ex. 4 55.0 38.3 49.3 42.7 Comp. Ex. 5 20.0 71.6 33.0 58.6 Comp. Ex. 6 73. 0 21. 6 57.5 35.8 Comp. Ex. 7 15.1 75.5 42.9 47.8 Comp. Ex. 8 31.9 58.8 73.6 21.8

As shown in Table 4, the briquettes of Examples 1 to 7 had superior strength, characterized by more than 88 % shatter resistance and less than 10 % dust rate. Further, as determined after 24 hours, the briquettes continued to exhibit high strength, with more than 77 % shatter resistance and less than 19 % dust rate.

In contrast, Comparative Examples 1 to 8 provide briquettes with low shatter resistance and high dust rate, thereby being evaluated as defective briquettes not applicable to a smelting reduction furnace.

Table 5 shows ranges of shatter resistance and dust rate for coal and briquette specimens. The coal exhibits a shatter resistance within an acceptable range for an actual smelting reduction iron-making process. If coal has a shatter resistance below the acceptable range, the temperature of molten iron is decreased, thereby resulting in a degraded productivity and causing problems in the manufacturing process. Further, as for dust rate, when a coal or briquette with a value above an acceptable range is charged into a smelting furnace, incomplete combustion occurs. In this case, an excessive amount of unburnt coal is collected by a collector, thereby increasing operation costs, and adversely affecting on operation. For this reason, it is required to use stricker optimal and acceptable range values for briquettes because dust formed from those briquettes has a reduced particle size.

Table 5 Shatter Resistance (%) Dust Rate (%) Optimal Acceptable Acceptable Specimens Range Range Optimal Range Range Coal (10-60 mm) 80 or over 70 or over 10 or less 5 or less Briquette (10-60 mm) 80 or over 70 or over 25 or less 20 or less

Example 3 The following experiment was performed while changing the mixing order of quicklime and molasses to be mixed with fine coal, in order to evaluate a variation in the characteristics of the produced briquette according to the change of the mixing order.

First, as indicated in Table 6, a fine coal of 3.4 mm or less in size (from Australia: Mt. Thorley) was homogenously mixed with 3 weight parts of quicklime relative to 100 weight parts of the fine coal in a Muller Mixer, and aged for 10 min.

Then, 8 weight parts of molasses was added to the mixture, and stirred in a kneader for 5 min, in order to achieve an increase in hardening efficiency. The resulting mixture was compressed using a Briquetter Roller Press at room temperature to form a pillow-shaped briquette of 63.5 mm in diameter, 25.4 mm in width, and 19.1 mm in thickness.

For preparing another briquette, a fine coal having the same particle size as above was homogenously mixed with 8 weight parts of molasses as a binder relative to 100 weight parts of the fine coal in a Muller Mixer for 5 min. Then, 3 weight parts of quicklime as a hardener was added to the mixture, and mixed in the Muller Mixer for 3 min, then stirred in a kneader for 5 min, in order to achieve an increase

in hardening efficiency. The resulting mixture was compressed to form a briquette at room temperature.

For preparing another briquette, a fine coal having the same particle size as above was homogenously and simultaneously mixed with both 3 weight parts of quicklime and 8 weight parts of molasses relative to the fine coal in the Muller Mixer for 5 min. Then, the mixture was stirred in a kneader for 5 min for increasing hardening efficiency. The resulting mixture was compressed using a Briquetter Roller Press at room temperature to form a pillow-shaped briquette of 63.5 mm in diameter, 25.4 mm in width, and 19.1 mm in thickness.

Table 6 Fine coal Molasses Quicklime Order of mixing (weight (weight (weight Second Examples part) part) part) First Ex. 1 100 8 3 quicklime molasses Comp. Ex. 1 100 8 3 molasses quicklime quicklime & Comp. Ex. 2 100 8 3 molasses For the produced briquettes, a drop test was performed immediately, and 24 hours after the production of those briquettes, to evaluate shatter resistance and dust rate. The testing results are shown in Table 7. The evaluation method was conducted in the same manner as in Example 1.

Table 7

Immediately after Formation 24 hr after Formation Shatter Shatter Dust Dust Resistance Resistance RateRate Examples(%) (%) Ex. 1 97.2 2.6 84.6 11.6 Comp. Ex. 1 64.3 27.6 75.2 14.6 Comp. Ex. 2 71.5 22.2 88.8 7.0 Referring to Table 7, it can be seen that Example 1 corresponding to a method in which a fine coal is first mixed with quicklime, aged, then mixed with molasses, provides a briquette having a shatter resistance of 95 % or more and a dust rate of 5 % or less.

On the other hand, Comparative Examples 1 and 2, which are beyond the range of the present invention, provide briquettes with a degraded shatter resistance and an increased dust rate, thereby exhibiting a degraded strength, as compared with Example 1. This will now be described in more detail.

Comparative Example 1 uses a method in which fine coal is first mixed with molasses, and then mixed with quicklime to form a briquette.

Where the molasses is mixed with the fine coal prior to

the adding of the quicklime, the mixture of fine coal and molasses has an increased total moisture content because the molasses, in general, contains 15 to 30 % by weight of moisture. In this case, conversion (hydroxylation) of quicklime to slaked lime occurs very rapidly, causing a chemical reaction producing bonds of calcium saccharate to occur at the surface of the quicklime contacting the mixture upon successive mixing the quicklime with the mixture. As a result, the mixture is rendered to be hardened before the quicklime is distributed homogenously in the mixture. As a result, the briquette formed in this way has a low initial strength of 64.3 %. On the other hand, it was found that 24 hours later, the briquette exhibits an increased shatter resistance. This is because the chemical reaction producing bonds of calcium saccharate, which did not proceed to completion, is gradually progressed with the lapse of time.

Comparative Example 2 uses a method in which fine coal is mixed with both quicklime and molasses at the same time to form a briquette.

In this case, similarly with Comparative Example 1, the quicklime reacts with the molasses to produce bonds of calcium saccharate before the quicklime and molasses are homogenously mixed with the fine coal, causing the mixture to be hardened.

Where the mixture is hardened early, it is impossible to produce a homogenous mixture consisting of fine coal, quicklime and molasses. As a result, the briquette formed in this way has an initial strength of 71.5 %, lower than that of briquettes of the Examples according to the present invention.

On the other hand, it was found that 24 hours later, the briquette exhibits an increased shatter resistance. This is because the chemical reaction producing bonds of calcium saccharate, which did not proceed to completion, is gradually progressed with the lapse of time.

As apparent from the above description, the present invention provides a briquette which has an optimal strength required in new iron making processes, the FINEX and COREX processes, thereby being useful and efficient, to strengthen competitiveness thereof.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.