Title of Invention	"A COAL BRIQUETTE FOR A SMELTING REDUCTION PROCESS"
Abstract	The present invention relates to a coal briquette for a smelting reduction process comprising: 50% by weight or less of dust, mixture of sludge and dust, the balance of fine coal, as major components, the sludge having iron(Fe) or iron compounds, carbon (C ), Ca compounds and Mg compounds; and 5-20 parts by weight of a binder, based on 100 parts by weight of the major components.

Full Text

Technical Field The present invention relates to coal briquettes for a smelting reduction process in which coal and iron ore are charged into a smelting furnace to produce a molten iron. More particularly, the present invention relates to coal briquettes having sufficient falling strength and thermal decrepitation required for a smelting reduction process which comprise sludge and dust as raw materials, and methods for manufacturing the coal briquettes. Background Art It is known that since novel FINEX and COREX processes being smelting reduction processes (process of making molten iron using coal) use coal as a fuel for a smelting furnace, instead of coke, they have advantages in terms of fuel availability. The particle size of the coal usable for the smelting reduction process is limited to 8mm or more. When the coal has a particle size smaller than 8mm, it cannot be completely combusted in the smelting furnace and thus is trapped in a dust collector. In addition, when the fine coal having a particle size smaller than 8 mm is charged in an excess amount, undesirable unbalances causing various problems during the process, such as shortage of fuel due to trap in the dust collector, may occur. Accordingly, such fine coal is limited in its application in iron making processes. However, most of coal currently used for iron making processes consists of fine particles having a particle size of 8mm or smaller. Since the fine coal is limited in its use for the smelting reduction process, it is mainly used for a pulverized coal injection (PCI) or as a fuel for making coke. However, since coal capable of being used for COREX process is already specified in its characteristics, there is also a limitation in using fine coal for other processes except for the smelting reduction process. Accordingly, there is a need for developing methods capable of agglomerating fine coal into a coal briquette in an appropriate manner in order to use for the smelting reduction process. PCT publication WO 02/50219 suggests a method for producing a coal briquette from fine coal, which is applicable to a smelting reduction iron making process. This publication provides a coal briquette which is produced from fine coal by mixing molasses as a binder and quicklime as a hardener. Since the smelting reduction process is different from a blast furnace process for iron production, there are differences between properties required for the coal briquette. In the blast furnace process, since the temperature in the upper part of a blast furnace is as low as 200~300C, thermal dynamic decrepitation is not specially considered. At this time, the coal briquette and sintered ore are sequentially charged into the blast furnace, and then slowly descend to the lower part of the blast furnace. Accordingly, the coal briquette for the blast furnace process is required to have high compressive strength. On the contrary, in the smelting reduction process, since the temperature in the upper part of a smelting furnace is as high as about 100'C, the volatile components of the coal briquette are volatilized and decrepitated as soon as the coal briquette is charged into the smelting furnace. Accordingly, thermal decrepitation and thermal dynamic decrepitation, as well as falling strength are important factors required for the coal briquette for the smelting reduction process. Although prior art coal briquettes satisfy various properties required for the smelting reduction process, e.g., falling strength of 70% or higher, and thermal decrepitation of 70% or higher, they use only fine coal as their raw material. Various by-products are outputted from ironworks. To recycle the by-products in iron making processes provides economic advantages. The by-products are largely classified into the following four categories: dust, sludge, slag and waste refractory materials. Among them, since the dust and the sludge contain a large amount of Fe or Fe compounds, carbon (C), Ca compounds and Mg compounds, they are recycled as raw materials in ironworks and cement industries. The Fe compounds mainly include iron oxides. However, a large amount of the dust and sludge tends to be buried through their solidification or incinerated without recycling. Accordingly, treatment and recycling of the by-products are gradually becoming important environmental issues. The dust and the sludge are outputted from every process in ironworks. The dust and the sludge contain carbon usable as a heat source and a reducing agent, Fe compounds usable as an iron source, and Ca compounds and Mg compounds usable as additives, etc. Most of dust and sludge particles have a particle size of 1mm or less. The moisture content in the dust and the sludge is largely depended on various processes or properties of the dust and the sludge. Since the dust and the sludge contain a large amount of valuable components, a part of them are recycled. In view of components contained in the sludge and the dust, and properties and secondary pollution thereof, etc., mere is a need for a novel method capable of recycling the dust and the sludge in a pig iron making process. Due to its relatively high moisture content and an additional drying step, the sludge is seldom recycled. Accordingly, the recycling of the sludge is very important Disclosure 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 coal briquettes having sufficient falling strength, thermal decrepitation and thermal dynamic decrepitation required for a smelting reduction process using by-products outputted from ironworks as raw materials. It is another object of the present invention to provide methods for manufacturing the coal briquettes. In order to achieve the above objects of the present invention, there is provided a coal briquette for a smelting reduction process, comprising: 50% by weight or less of sludge and the balance of fine coal, as major components, the sludge including iron (Fe) or iron compounds, carbon (C), Ca compounds and Mg compounds; and 5-20 parts by weight of a binder, based on 100 parts by weight of the major components. In accordance with another aspect of the present invention, there is provided a coal briquette for a smelting reduction process, comprising: 50% by weight or less of dust and the balance of fine coal, as major components, the dust including iron (Fe) or iron compounds, carbon (C), Ca compounds and Mg compounds; and 5-20 parts by weight of a binder, based on 100 parts by weight of the major components. In accordance with another aspect of the present invention, there is provided a coal briquette for a smelting reduction process, comprising: 50% by weight or less of a mixture of sludge and dust and the balance of fine coal, as major components, the sludge and the dust including iron (Fe) or iron compounds, carbon (C), Ca compounds and Mg compounds; adding 5-20 parts by weight of molasses as a binder to 100 parts by weight of the major components, and stirring; and shaping the resulting mixture. If necessary, prior to the addition of the binder, 5 parts by weight or less of quicklime as a hardener may be added to 100 parts by weight of the major components, and then aged. The present inventors have found that a coal briquette manufactured by using sludge or dust, by-products outputted from ironworks, and fine coal as raw materials can be used for a smelting reduction process (FINEX or COREX process), and as a result, accomplished the present invention. The coal briquette according to the present invention satisfies requirements of falling strength, thermal decrepitation and thermal dynamic decrepitation required for a smelting reduction process. In particular, the sludge used as a raw material for the coal briquette according to the present invention may be in the dried or undried form. In accordance with the present invention it relates to a coal briquette for a smelting reduction process comprising: 50% by weight or less of dust, mixture of sludge and dust, the balance of fine coal, as major components, the sludge having iron(Fe) or iron compounds, carbon (C ), Ca compounds and Mg compounds; and 5-20 parts by weight of a binder, based on 100 parts by weight of the major components 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 process chart schematically showing a method for manufacturing a coal briquette using sludge and dust according to the present invention. Best Mode for Carrying Out the Invention The present invention will be now explained in terms of a coal briquette and a method for manufacturing the coal briquette. [Coal briquette] The coal briquette of the present invention comprises at least one of sludge and dust, and fine coal as major components; and a binder. If necessary, the coal briquette of the present invention further comprises a hardener. [Fine coal] The fine coal used in the present invention is coal not meeting the particle size requirements for a pig iron making process (COREX process). That is, coal having a particle size of 8mm or more is commonly recommended in the COREX process. Accordingly, the fine coal used in the present invention has a particle size of below 8mm, and preferably below 4mm. When the particle size of the fine coal is 8mm or more, very high compacting pressure is required in the shaping step and thus may cause cracks of the resulting coal briquette. Accordingly, the fine coal is preferably ground to a particle size of below 4mm. [Sludge and dust] The sludge and the dust used in the present invention comprise valuable components such as iron (Fe) or iron compounds, carbon (C), Ca compounds and Mg compounds. The Fe compounds mainly include iron oxides. The sludge and the dust outputted from ironworks (pig iron making process and steel making process, etc.) comprise the valuable components as listed above. Physical properties of the sludge are similar to those of the dust, except for a difference in moisture content. Accordingly, when the sludge is dried, physical properties of the sludge are almost the same as those of the dust. The sludge may be used in the dried form, but is characterized by its undried form. That is, the undried sludge can be used as a raw material of the coal briquette for a smelting reduction process according to the present invention. The undried sludge preferably contains 50% or less of moisture. When the moisture content of the undried sludge exceeds 50%, the undried sludge cannot be homogeneously distributed into the fine coal, and finally is agglomerated in the form of clumps. That is, the segregated undried sludge lowers the falling strength and the thermal decrepitation of the resulting coal briquette. On the other hand, the dried sludge usable in the present invention contains 5% or less of water. Considering the recycling of the sludge and the dust as raw materials of the coal briquette for a pig iron making process, the higher the content of valuable components, the better. It is preferred that the content of valuable components is 30% by weight or more, based on the dry weight of the sludge or the dust. The sludge or dust may contain impurities such as Zn, alkali metals, Al2O3, S, P, Cal, etc. The contents of these impurities are preferably limited as follows: 2.0% or less of Zn, 2.0% or less of the total weight of alkali metals, 1.0% or less of S, 1.0% or less of P, 6.0% or less of Al2O3, and 1.0% or less of Cal. Since Zn and alkali metals may form deposits within a gasification melting furnace, negatively affecting gas flow and impeding descent of charging materials, etc., their contents are preferably limited to 2.0% or less, respectively. Since S and P are components limited in molten pig iron, the contents are preferably limited to 1.0% or less, respectively. Since Al2O3 is a problematic component affecting fluidity of slag, the addition of a large amount of sub-raw materials is required to prevent the fluidity of slag. Accordingly, the content of Al2O3 is limited to 6.0% or less, and more preferably 3.0% or less. Cal may be concentrated in the water treatment facilities and thus corrodes the facilities. Accordingly, the content of Cal is preferably limited to 1.0% or less. It is preferred that the total weight of the valuable components and the content of the impurities satisfy the ranges as discussed above. When the total weight of the valuable components and the content of the impurities are out of the preferable ranges, sludge or dust within the preferable ranges can be mixed with sludge or dust out of the ranges so that the total weight of the valuable components and the content of the impurities satisfy the preferable ranges. Representative examples of the sludge satisfying the preferable ranges include sludge from blast furnace in ironworks, sludge from molten iron making processes using coal, sludge from water treatment facility in iron and steel works and sludge from sewage treatment facility. On the other hand, as the dust, dust from wire rod facility in ironworks is mainly used. Since dust from sinter facility in ironworks exceeds the allowable content ranges of alkali metals and Cl, it is not desirably used as a raw material for the coal briquette of the present invention. The composition of the sludge and the dust outputted from ironworks is presented in the following Table 1. (Table Removed) A: sludge from blast furnace, B: sludge from molten iron making processes using coal, C: sludge from water treatment facility in iron and steel works, D: sludge from sewage treatment facility, E: dust from wire rod facility, F: dust from sinter facility. The coal briquette of the present invention comprising 50% by weight or less of at least one of sludge and dust and the balance of fine coal, as major components, is preferred. When the content of the sludge and the dust is above 50%, physical properties of the resulting coal briquette may be deteriorated. Since physical properties of the sludge are similar to those of the dust, the mixing ratio of the sludge and the dust can be appropriately determined. [Binder] The binder usable in the present invention includes petroleum pitch, petroleum bitumen, molasses, thermosetting resins, starches and cements, etc., and is most preferably molasses. Molasses preferably has a solid content of 70-80% by weight. When the solid content is below 70%, the content of sugar which exhibits the intrinsic characters of binder is too low. When the solid content is above 80%, it is impossible to uniformly mix with the other components due to high viscosity of the molasses. The binder is added in an amount of 5-20 parts by weight, based on 100 parts by weight of the major components consisting of 50% by weight or less of at least one of sludge and dust and the balance of fine coal. When the amount of the binder added is below 5 parts by weight, shaping strength of the coal briquette is too low. When the amount of the binder added is above 20 parts by weight, it is not preferred in terms of low economic efficiency. [Hardener] If necessary, the coal briquette of the present invention further comprises a hardener. As the hardener, inorganic materials such as quicklime (CaO), Limestone, iron ore, bauxite, etc., may be used, and quicklime (CaO) is most preferred. The quicklime (CaO) is converted into slaked lime by an exothermal reaction with moisture contained in fine coal or sludge. The quicklime can remove moisture contained in fine coal or sludge by the exothermal reaction. The Quicklime preferably has a particle size of 1mm or less. The smaller the quicklime particles are, the broader the specific surface area is. Accordingly, the quicklime (CaO) is readily converted into slaked lime through a reaction with moisture contained in fine coal. The hardener is preferably added in an amount of 5 parts by weight, based on 100 parts by weight of the major components consisting of fine coal, sludge and dust. When the amount of the hardener added is above 5 parts by weight, physical properties of the resulting coal briquette may be deteriorated. [Manufacture of coal briquette] The coal briquette of the present invention is manufactured by adding a binder, if necessary, a hardener to major components consisting of fine coal, and dust and/or sludge. Physical properties of the coal briquette are affected by the mixing order of these raw materials and process variables. In the present invention, molasses is used as the binder and quicklime is used as the hardener. The most preferred method for manufacturing the coal briquette is shown in Fig. 1. First, 50% by weight of at least one of sludge and dust is added to the fine coal. The mixing time is varied according to whether or not the sludge is dried. When the sludge is a dried form, the mixing time is not longer than 3 minutes. When the sludge is an undried form, the mixing time is within the range of 3~10 minutes. When the dried sludge is mixed for more than 3 minutes, the increased time does not contribute to improvement of properties. When the undried sludge is mixed for less than 3 minutes, mixing of the fine coal with the undried sludge is incomplete and thus agglomeration may occur. When the undried sludge is mixed for more than 10 minutes, the increased time does not contribute to improvement of properties. The quicklime is added in an amount of 5 parts by weight, based on 100 parts by weight of the major components consisting of fine coal, sludge and dust. The mixing was carried out in a mixer to obtain a homogenous mixture. The mixing time is preferably within the range of 1-3 minutes. Thereafter, me quicklime is aged so as to be converted into slaked lime. The aging can be partly carried out in the mixer, but this is limited due to its relatively short residence time in the mixer. Accordingly, the aging is preferably carried out in a reservoir such as a hopper for a long time. It is preferred that the aging is carried out for about 2 minutes ~2 hours. The aged mixture is again mixed with 5~20 parts by weight of molasses as a binder. The mixing is carried out in a mixer. In the mixing step, imreacted quicklime is reacted with moisture contained in the molasses, and as a result, calcium saccharate bonds are formed therebetween so that the quicklime is converted into slaked lime. The conversion is limited due to relatively short residence time in the mixer. Accordingly, it is preferred that the mixture of quicklime and molasses is stirred for an extended residence tune to improve the strength of final coal briquette by curing the coal briquette through the formation of calcium saccharate bonds. The stirring is more preferably carried out in a kneader, a kind of mixing mill, than in a mixer. The kneader comprises a central shaft hi the form of vertical cylinder to which blades are mounted. The kneader is used to stir the mixture of quicklime and molasses. The stirring is preferably carried out within the range of 2-50 minutes. When the stirring is carried out for less than 2 minutes, the strength of the final coal briquette is poor. When the stirring is carried out for more than 50 minutes, the mixture is dried and thus the strength of the shaped coal briquette becomes poor. Shaping follows the stirring. The shaping is carried out in a roll press under a constant pressure to manufacture a coal briquette. When the coal briquette of the present invention has the moisture content of 30% or higher, its falling strength and thermal decrepitation are poor. Accordingly, it is preferred to maintain the moisture content at 30% or lower throughout all processes. Hereinafter, the present invention will be described in more detail with reference to the following Examples. [Example 1] 10% by weight of dried sludge and/or dust having the compositions listed in Table 2 below, and fine coal having a particle size of 4mm or less were mixed for 3 minutes or less. The used dried sludge and dust satisfied the content ranges of impurities shown in Table 1 above. The dried sludge was obtained by drying in a rotary kiln. (Table Removed) 3 parts by weight of quicklime as a hardener was added to 100 parts by weight of the mixture (major components). The resulting mixture was aged for 2 minutes~2 hours. 8% by weight of molasses as a binder was added to 100 parts by weight of the mixture, and then stirred at room temperature for 2~50 minutes to manufacture a coal briquette. Falling strength, thermal decrepitation and dynamic thermal decrepitation were measured. The results are shown in Table 3 below. Falling strength was measured by dropping the coal briquette thus manufactured from a height of 5m four times, and expressing as a fraction of coarse particles and fine particles (particle size 6.3mm), based on the total weight of the crushed particles. The fraction of coarse particles is calculated by the following equation: Particles having a particle size larger than 20mm (% by weight) + {particles having a particle size of 10~20mm (% by weight)} x (—)} Thermal decrepitation was measured by placing the coal briquette manufactured thus in a reaction furnace at 1000.C to obtain coal char and expressing as a fraction of coarse particles and fine particles (particle size Particles having a particle size larger than 20mm (% by weight) + (particles having a particle size larger than 16mm (% by weight) x (3/4)} + {particles having a particle size larger than 13mm (% by weight) x (2/4)} + {particles having a particle size larger than 1 0mm (% by weight) x (1/4)} Thermal dynamic decrepitation was measured by placing the coal briquette manufactured thus hi a rotary furnace at 900. C) to obtain coal char and expressing as a fraction of coarse particles, based on the weight of the obtained the coal char. The fraction of coarse particles is calculated by the following equation: Particles having a particle size larger than 20mm (% by weight) + {particles having a particle size larger than 10mm (% by weight) x (1/2)} The larger the fractions of coarse particles and the smaller the fractions of fine particles, the more excellent these properties were. As shown in Table 3, the (Table Removed 3) coal briquette of the present invention had properties equal to or more excellent than lump coal. Accordingly, the coal briquette of the present invention can be used for molten iron making processes using coal. In the present invention, dust from sinter facility (El) can be used in the form of a mixture with coal, but it contains a large amount of harmful components (S, alkali metals, Cl), causing process problems. Accordingly, it is recommended that the dust from sinter facility be mixed with other sludge or dust to dilute the content of the harmful components. At this time, the amount of the sludge or dust to be mixed can be limited by the content of the harmful components. [Example 2] Untried sludge having the compositions listed in Table 4 below and dust were mixed with each other for 3~10 minutes to obtain mixtures shown in Table 5 below. The used untried sludge shown in Table 4 satisfied the content ranges of the impurities shown in Table 1 above. At this time, 10% by weight of sludge and dust, and 90% by weight of fine coal having a particle size of 4mm or less were mixed. (Table Removed) 3 parts by weight of a hardener was added to 100 parts by weight of the mixture (major components), and then aged for 2 minutes~2 hours. To 100 parts by weight of the aged mixture, 8 parts by weight of molasses was added. The resulting mixture was stirred for 2~50 minutes to manufacture a coal briquette. On the other hand, the coal briquette was manufactured in the same manner as in Example 1, except that the undried sludge shown inTable 4 was dried. Falling strength and thermal decrepitation of the coal briquette thus manufactured were measured. (Table Removed) As shown in Table 5, the coal briquette manufactured prepared using undried sludge was equal to or more excellent than lump coal in terms of their properties. Accordingly, the coal briquette of the present invention can be used for molten iron making processes using coal. [Example 3] Undried sludge Bl shown in Table 4 was dried so that the moisture content in the undried sludge reached 3% or lower. The undried sludge was mixed with fine coal having a particle size of 4mm or less for 3 minutes or less. At this step, the mixing ratio of the dried sludge and the fine coal is shown in Table 6 below. 3 parts by weight of quicklime as a hardener was added to 100 parts by weight of the mixture of sludge and fine coal (major components). The resulting mixture was then aged for 2 minutes~2 hours. To 100 parts by weight 'of the aged mixture, 8% by weight of molasses as a binder was added. The resulting mixture was stirred at room temperature for 2-50 minutes to manufacture a coal briquette. Falling strength and thermal decrepitation of the coal briquette thus manufactured were measured. The results are shown in Table 6 below. (Table Removed 6) From the results shown in Table 6, it can be seen that although the amount of the sludge mixed was varied, there were no large changes in the properties of the coal briquette and the coal briquette of the present invention can be used for molten iron making processes using coal. Industrial Applicability As can be seen from the foregoing, dust and sludge, in particular undried sludge can be recycled as raw materials of the coal briquette according to the present invention which is used for iron making processes. In addition, the coal briquette according to the present invention has more excellent falling strength and thermal decrepitation than conventional coal briquettes manufactured using coal. 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. We Claim: 1. A coal briquette for a smelting reduction process comprising: 50% by weight or less of dust, mixture of sludge and dust, the balance of fine coal, as major components, the sludge having iron(Fe) or iron compounds, carbon (C ), Ca compounds and Mg compounds; and 5-20 parts by weight of a binder, based on 100 parts by weight of the major components. 2. The coal briquette for a smelting reduction process as claimed in claim 1, wherein the sludge is an undried form containing 50% or less of moisture. 3. The coal briquette for a smelting reduction process as claimed in any one of claims 1, wherein the sludge or dust contains 2.0% or less of Zn, 2.0% or less of alkali metals, 1.0% or less of S, 1.0% or less of P, 6.0% or less of A1203 and 1.0% or less of CI as impurities. 4. The coal briquette for a smelting reduction process as claimed in claim 3, wherein the sludge is at least one selected from sludge from blast furnace in ironworks, sludge from molten iron making processes using coal, sludge from water treatment facility in iron and steel works, and sludge from sewage treatment facility. 5. The Coal briquette for a smelting reduction process as claimed in claim 4, wherein the dust includes dust from wire rod facility. 6. The coal briquette for a smelting reduction process as claimed in any one of claims 1 to 3, wherein the total content of iron (Fe) or iron compounds, carbon (C), Ca compounds and Mg compounds is 30% by weight or more, based on the dry weight of the sludge or dust. 7. The coal briquette for a smelting reduction process as claimed in any one of claims 1 to 3, wherein the binder is molasses. 8. A coal briquette for smelting reduction process substantially as herein described with reference to the foregoing description, example, tables and the accompanying drawings.

Documents:

1324-DELNP-2004-Abstract-(06-04-2009).pdf

1324-DELNP-2004-Abstract-(15-04-2009).pdf

1324-DELNP-2004-Abstract-(19-03-2009).pdf

1324-delnp-2004-abstract.pdf

1324-DELNP-2004-Assignment-(19-03-2009).pdf

1324-delnp-2004-assignment.pdf

1324-DELNP-2004-Claims-(06-04-2009).pdf

1324-DELNP-2004-Claims-(15-04-2009).pdf

1324-DELNP-2004-Claims-(25-11-2008).pdf

1324-delnp-2004-claims.pdf

1324-DELNP-2004-Correspondence-Others-(06-04-2009).pdf

1324-DELNP-2004-Correspondence-Others-(15-04-2009).pdf

1324-DELNP-2004-Correspondence-Others-(19-03-2009).pdf

1324-DELNP-2004-Correspondence-Others-(25-11-2008).pdf

1324-delnp-2004-correspondence-others.pdf

1324-DELNP-2004-Description (Complete)-(06-04-2009).pdf

1324-DELNP-2004-Description (Complete)-(15-04-2009).pdf

1324-DELNP-2004-Description (Complete)-(19-03-2009).pdf

1324-delnp-2004-description (complete).pdf

1324-DELNP-2004-Drawings-(19-03-2009).pdf

1324-delnp-2004-drawings.pdf

1324-DELNP-2004-Form-1-(06-04-2009).pdf

1324-DELNP-2004-Form-1-(25-11-2008).pdf

1324-delnp-2004-form-1.pdf

1324-delnp-2004-form-18.pdf

1324-DELNP-2004-Form-2-(06-04-2009).pdf

1324-DELNP-2004-Form-2-(25-11-2008).pdf

1324-delnp-2004-form-2.pdf

1324-delnp-2004-form-3.pdf

1324-delnp-2004-form-5.pdf

1324-DELNP-2004-GPA-(25-11-2008).pdf

1324-DELNP-2004-Others-Document-(19-03-2009).pdf

1324-delnp-2004-pct-101.pdf

1324-DELNP-2004-PCT-210-(25-11-2008).pdf

1324-delnp-2004-pct-210.pdf

1324-DELNP-2004-PCT-220-(25-11-2008).pdf

1324-DELNP-2004-PCT-304-(19-03-2009).pdf

1324-delnp-2004-pct-308.pdf