Patent Application
20120017849
This application is related to application number 20-2010-7716, filed Jul. 22, 2010, and application number 10-2010-79534, filed Aug. 17, 2010, both in the Republic of Korea, the disclosures of which are incorporated herein by reference and to which priority is claimed.
The present invention relates to a heat collecting combustion apparatus, and more particularly, to a heat collecting combustion apparatus that collects heat of combustion that is generated by burning a solid fuel and so on in a combustion chamber and uses the collected heat as a recovery energy source.
In general, industrial facilities that require industrial hot water, steam or gas of high temperature use a combustion apparatus that ignites and burns fuel in a combustion vessel to thus generate thermal energy, respectively. In addition, solid fuels such as RDF (Refuse Derived Fuel) that is made from waste into a fuel or RPF (Refuse Plastic Fuel) that is made from scrapped plastic waste into a fuel are widely being used as fuels that are used in the combustion apparatus in terms of economical efficiency and recycling of resources.
However, since these conventional combustion apparatuses employ a method of putting and burning a lot of solid fuels into the bottom of the combustion vessel, the solid fuels may be incompletely burnt to thus cause a waste of the solid fuels as well as to lower a thermal efficiency. In addition, since a lot of ashes are generated at a time, it is not so easy to construct automation of the remaining ashes, and it is cumbersome to take out the left ashes from the bottom of the combustion vessel. Further, if solid fuels have been completely burnt on the bottom of the combustion vessel, new solid fuels should be put into the bottom of the combustion vessel and then ignited again, to thereby make it to perform a continuous combustion process difficult and make a caloric value uneven.
In addition, these solid fuels have caused a problem of discharging a massive amount of gases or particles such as dust, carbon monoxide, soot, gaseous HCL, SOx, NOx, and dioxin that pollute environment during combustion.
To solve these problems, a combustion apparatus 1000 has been developed. The heat collecting combustion apparatus 1000 according to the conventional technology, burns solid fuels that are supplied from a fuel hopper 310 into a combustion vessel 1 to thus generate hot combustion gases. Here, air that is necessary for combustion of fuels is supplied from the outside into a combustion chamber 110 via an air cooling chamber 150, a passage 140a of an intermediate wall 140, a swirl flow supply chamber 130, and a passage 120a of an inner wall 120.
In addition, the combustion gases of high temperature that have been generated by combustion of fuel in the combustion chamber 110 are supplied to a heat collecting unit such as a boiler through an elbow-shaped combustion gas discharge tube 400, to thereby collect heat.
However, the conventional solid fuel combustion apparatus supplies air that is needed to burn solid fuels to only outer portions of the solid fuels that have been loaded in the combustion chamber. Accordingly, the outer portions of the solid fuels are well burnt but the inner portions thereof may be difficult to contact the air necessary for combustion and thus may be burnt imperfectly. In addition, the inner wall of the combustion chamber is persistently exposed to the combustion gases of high temperature and thus may be deformed and cracked at a long-term use, to accordingly lower durability.
To solve the above problems of the conventional art, it is an object of the present invention to provide a combustion apparatus that ensures complete combustion of solid fuels loaded inside a combustion chamber and reduces a loss of heat to thus improve a thermal efficiency, as well as that lowers temperature of inner walls of the combustion chamber that is continuously exposed to high temperature combustion gases to thereby enhance durability.
To achieve the above object of the present invention, there is provided a combustion apparatus with improved thermal efficiency having a combustion vessel that receives an air supply from the outside to thus burn a fuel that is supplied from a fuel supply unit, the combustion apparatus comprising:
a cylindrical combustion chamber that is surrounded by an inner wall of the combustion vessel to thus burn a fuel;
a cooling chamber that comprises an intermediate wall that is formed to be spaced apart from an outer side of the inner wall of the combustion vessel, in which a cooling water inlet and a cooling water outlet through which cooling water flows in and out, respectively, are formed at lower and upper sides of the intermediate wall, and that is formed at an outer circumference of the combustion chamber, to thereby cool the inner wall of the combustion chamber by the cooling water that flows into a space formed between the inner and intermediate walls of the cooling chamber through the cooling water inlet;
a lateral combustion air supply chamber that comprises an outer wall that is formed to be spaced apart from an outer side of the intermediate wall of the cooling chamber, in which a combustion air supply inlet through which air necessary for combustion is supplied from the outside is formed at an upper side of the outer wall, and that is formed at an outer circumference of the cooling chamber, to thereby make the air supplied through the combustion air supply inlet that is formed in a tangential direction with respect to the cylindrical outer wall turn and fall in a space formed between the intermediate wall of the cooling chamber and the outer wall of the lateral combustion air supply chamber, so that the combustion air is supplied to the combustion chamber via an opened lower portion of the lateral combustion air supply chamber.
Preferably but not necessarily, the combustion apparatus further comprises: a boiler comprising a water tube to which the combustion gases that have been generated by burning the fuel in the combustion chamber are supplied to the boiler to thereby collect heat from the combustion gases, wherein the cooling water discharged from the cooling water outlet in the cooling chamber is connected with the water tube in the boiler via a connection tube so as to be used to collect heat from the combustion gases generated by the combustion vessel.
Preferably but not necessarily, the connection tube comprises first and second connection tubes, and a boiler feed water tank is provided between the first and second connection tubes, in which the cooling water discharged from the cooling water outlet in the cooling chamber flows into the water tube of the boiler via the boiler feed water tank.
Preferably but not necessarily, a spirally shaped cooling water guide plate is provided in the cooling chamber so that the cooling water introduced via the cooling water inlet turns and rises up.
Preferably but not necessarily, the fuel supply unit that is installed at the lower portion of the combustion vessel comprises a lower combustion air supply tube whose diameter is larger than that of the fuel supply tube through which fuel is supplied, and that is formed in the form of a concentric circle, to thereby supply combustion air from the lower portion of the combustion chamber to the bottom surface of the fuel.
Preferably but not necessarily, an upper end portion that is protrudingly formed from the fuel supply tube into the combustion chamber comprises: a diameter enlargement portion whose diameter gradually grows bigger upwards; and a slope guide portion that is bent downwards from the end portion of the diameter enlargement portion and is formed slanting downwards.
Preferably but not necessarily, an upper end portion that is protrudingly formed from the lower combustion air supply tube into the combustion chamber comprises an air feed diameter enlargement portion whose diameter gradually grows bigger upwards and that is positioned at the lower side of the diameter enlargement portion of the fuel supply tube, and wherein a number of air feed nozzles are formed in the diameter enlargement portion of the fuel supply tube so that the combustion air supplied from the lower combustion air supply tube is introduced into the combustion chamber.
Preferably but not necessarily, an upper end of the air feed diameter enlargement portion of the lower combustion air supply tube is closed by the slope guide portion of the fuel supply tube.
Preferably but not necessarily, the combustion apparatus further comprises an upper combustion air supply chamber that is formed at the upper circumference of the combustion chamber and supplies combustion air to the upper portion of the combustion chamber, wherein the upper combustion air supply chamber comprises: a swirl flow supply chamber that comprises an upper intermediate wall that is formed so as to be spaced apart from an outer side of an upper inner wall that surrounds an upper inner side of the combustion chamber in which an air passage is formed at the upper end of the upper intermediate wall, and that supplies combustion air to the upper portion of the combustion chamber; and a preheating chamber that comprises a cylindrical upper outer wall that is formed so as to be spaced apart from an outer side of the upper intermediate wall in which an upper air supply inlet through which combustion air is supplied from the outside is formed at the lower portion of the preheating chamber, in a tangential direction with respect to the upper outer wall, in which the combustion air that is introduced into the preheating chamber through the upper air feed inlet of the upper outer wall turns, rises up and moves in the preheating chamber, and then moves from the upper portion of the swirl flow supply chamber to the lower portion thereof via the air passage formed at the upper end of the upper intermediate wall, to thus be supplied to the combustion chamber via a combustion air supply passage that is formed at the lower end of the upper intermediate wall.
Preferably but not necessarily, a rotary type fire grate on the upper surface of which a fuel that is supplied via the fuel supply tube is supplied is provided on the bottom of the combustion chamber, in which cross-section of both sides of the rotary type fire grate is formed in a V-shaped form.
The present invention provides a combustion apparatus that ensures complete combustion of solid fuels loaded inside a combustion chamber and reduces a loss of heat to thus improve a thermal efficiency, as well as that lowers temperature of inner walls of the combustion chamber that is continuously exposed to high temperature combustion gases to thereby enhance durability.
The above and other objects and advantages of the present invention will become more apparent by describing the preferred embodiment thereof in more detail with reference to the accompanying drawings in which:
A combustion apparatus according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings,
A combustion apparatus according to a preferred embodiment of the present invention, includes a combustion vessel 100 that burns a fuel therein and generates combustion gases of high temperature generated by combustion, and collects heat from the high temperature combustion gases using a boiler.
First, the combustion vessel 100 is formed in a cylindrical shape, and contains and burns a solid fuel therein. The combustion vessel 100 includes: a combustion chamber 11 that is surrounded by an inner wall of the combustion vessel 100 to thus burn a fuel; a cooling chamber 13 that cools the inner wall of the combustion chamber 11; and a lateral combustion air supply chamber 15 that is formed at the side surface of the combustion chamber 11 in order to supply air necessary for combustion supplied from the outside for the combustion chamber 11.
The cooling chamber 13 plays a role of lowering temperature of the inner wall 12 that continues to contact the hot combustion gases of high temperature. As shown in
The lateral combustion air supply chamber 15 is formed in a space formed between the intermediate wall 14 of the cylindrical combustion vessel 100 and an outer wall 16 that is formed to be spaced apart from an outer side of the intermediate wall 14. A combustion air supply inlet 16a through which air necessary for combustion is supplied from the outside is formed at an upper side of the outer wall 16. The lower portion 12a of the lateral combustion air supply chamber 15 is opened. The combustion air supply inlet 16a is formed in a tangential direction with respect to the cylindrical outer wall 16. Accordingly, the air supplied through the combustion air supply inlet 16a turns and falls down in the inside of the lateral combustion air supply chamber 15, and then is supplied into the combustion chamber 11 via an opened lower portion 12a of the lateral combustion air supply chamber 15.
In addition, an upper combustion air supply chamber 20 is formed at the upper circumference of the combustion chamber 11 in order to supply combustion air to the side portion of the upper portion of the combustion chamber 11. The upper combustion air supply chamber 20 is combined with the upper side of the cooling chamber 13 and the lateral combustion air supply chamber 15 using flanges 18, and includes: a swirl flow supply chamber 23 that is formed at an outer circumference of a cylindrical upper inner wall 22 that surrounds an upper inner side of the combustion chamber 11; and a preheating chamber 25 that is formed at an outer circumference of the swirl flow supply chamber 23, in order to supply combustion air supplied from the outside for the swirl flow supply chamber 23.
The swirl flow supply chamber 23 is formed in a space formed between the upper inner wall 22 and an upper intermediate wall 24 that is formed so as to be spaced apart from an outer side of the upper inner wall 22, and the preheating chamber 25 is formed in a space formed between the upper intermediate wall 24 and an upper outer wall 26 that is formed so as to be spaced apart from an outer side of the upper intermediate wall 24. An upper air supply inlet 26a is formed at the lower portion of the upper outer wall 26, in a tangential direction with respect to the upper outer wall 26, and an air passage 24a is formed at the upper end of the upper intermediate wall 24, so that combustion air supplied from the outside turns to then be supplied into the preheating chamber 25. The combustion air that is introduced into the preheating chamber 25 turns and rises up upwards in the preheating chamber 25, and then moves from the upper portion of the swirl flow supply chamber 23 to the lower portion thereof via the air passage 24a formed at the upper end of the upper intermediate wall 24, to thus be supplied to the upper portion of the combustion chamber 11 via a combustion air supply passage 22a that is formed at the lower end of the upper inner wall 22.
The upper portion of the combustion vessel 100 is opened in order to exhaust the hot combustion gases of high temperature that are generated by burning a fuel, and the exhausted hot combustion gases are introduced into the boiler 60 through a combustion gas discharge tube (not shown) in order to collect heat. The boiler 60 collects heat from the hot combustion gases and thus obtains hot steam of high temperature. Here, the cooling water that is introduced from the cooling water outlet 14b is introduced into the boiler 60 through a boiler feed water tank 61, to thereby be turned into steam using heat of the combustion gases.
Meanwhile, an ash ejection outlet 19 is formed at the lower edge of the combustion vessel 100 to thereby discharge ashes of the burnt solid fuels.
In addition, a rotary type fire grate 17 (grate is plate for loading the solid fuel in the top surface thereof) is rotatably installed at the lower portion of the combustion chamber 11. The rotary type fire grate 17 is made in the form of a disc, and plays a role of burning solid fuels loaded in the top surface thereof. The rotary type fire grate 17 is sloped downwards from the center thereof to the outer side inflection point thereof and then is sloped upwards from the outer side inflection point to the outermost side thereof. Accordingly, both side cross-sections of the rotary type fire grate 17 are formed into a V-shaped form. A fuel supply unit 40 for supplying solid fuels for the rotary type fire grate 17 is formed at the center of the rotary type fire grate 17.
A fuel inlet 44 is formed at one side of the lower portion of the fuel supply unit 40, and a fuel supply tube 41 is provided in the fuel supply unit 40 to thereby supply solid fuels into the combustion chamber 11 by a transfer screw 42. In addition, a lower combustion air supply tube 43 whose diameter is larger than that of the fuel supply tube 41 and that is formed in the form of a concentric circle is formed at the outer side of the fuel supply tube 41, in which the lower combustion air supply tube 43 supplies combustion air from the lower portion of the combustion chamber 11 into the inside of the combustion chamber 11 by an air supply unit 45 such as a ring blower.
An upper end portion that is protrudingly formed from the fuel supply tube 41 into the combustion chamber 11 includes: a diameter enlargement portion 41a whose diameter gradually grows (=becomes bigger) upwards; and a slope guide portion 41b that is bent downwards from the end portion of the diameter enlargement portion 41a and is formed slantly downwards. The diameter enlargement portion 41a and the slope guide portion 41b make the fuels be supplied to the fire grate 17 more stably. A number of air feed nozzles 41c are formed at the diameter enlargement portion 41a so that the combustion air supplied from the lower combustion air supply tube 43 is introduced into the combustion chamber 11.
In addition, an upper end portion that is protrudingly formed from the lower combustion air supply tube 43 into the combustion chamber 11 includes an air feed diameter enlargement portion 43a whose diameter gradually grows upwards and that is positioned at the lower side of the diameter enlargement portion 41a of the fuel supply tube 41, and an upper end of the air feed diameter enlargement portion 43a is closed by the slope guide portion 41b of the fuel supply tube 41. Thus, the combustion air supplied through the lower combustion air supply tube 43 is guided by the air feed diameter enlargement portion 43a and then is supplied to the bottom of the fuels through a number of the air feed nozzles 41c that are formed at the diameter enlargement portion 41a of the fuel supply tube 41 that is formed at the upper side thereof.
Meanwhile, an air supply unit 45 such as a ring blower may be provided at the other side of the lower portion of the fuel supply tube 41, so that combustion air can be supplied through the fuel supply tube 41 in order to prevent the solid fuels that are burnt in the combustion chamber 11 from being reversed into the solid fuels that exist in the fuel supply tube 41.
According to the above-described configuration, the solid fuels are supplied to the center of the upper surface of the rotary type fire grate 17 by the fuel supply tube 41, and the combustion air is directly supplied to the bottom of the solid fuels through the air feed nozzles 41c that are formed at the diameter enlargement portion 41a of the fuel supply tube 41.
A transfer screw 42 that is formed in the fuel supply tube 41 and thus transfers the fuels into the combustion chamber includes a screw shaft 42d and screw blades 42e that are formed on the screw shaft 42d. The transfer screw 42 rotates by a motor (not shown) and transfers the fuels. The upper portion 42a of the screw shaft 42d is extended to the outside of the fuel supply tube 41, and are protrudingly formed in the combustion chamber 11. A radial fuel supply element 42b that radially supplies the fuels that are supplied through the fuel supply tube 41 into the combustion chamber 11 is formed by a certain length in the length direction of the transfer screw 42 at the upper portion 42a of the protruded screw shaft 42d.
The radial fuel supply element 42b is protrudingly formed perpendicularly from the axial direction of the screw shaft 42d and thus is rotated together with a transfer screw 42, to thereby radially supply the fuels that are raised up through the fuel supply tube 41 into the combustion chamber 11. As described above, the solid fuels that are supplied from the fuel supply tube 41 are radially consistently supplied into the combustion chamber 11, to thereby prevent clinkers from blocking the air feed nozzles 41c.
In addition, a fuel height control bracket 42c that is protrudingly formed perpendicularly from the axial direction of the screw shaft 42d is installed at the end of the upper portion 42a of the screw shaft 42d that is protrudingly formed in the combustion chamber 11. As shown in
Hereinbelow, an operational process of the combustion apparatus according to the embodiment of the present invention as constructed above will be described.
First, a certain amount of solid fuels are supplied into a combustion chamber 11 from a fuel hopper (not shown) by the rotation of a transfer screw 42 that is installed in a fuel supply tube 41. A radial fuel supply element 42b that is formed at an upper portion 42a of a screw shaft 42d protruded into the combustion chamber 11 and are rotated together with the screw shaft 42d radially supply the fuels that are raised up through the fuel supply tube 41 into the combustion chamber 11. By this configuration, the fuel supply unit 40 makes fuels whose particles are small and light rise up and be burnt by combustion air that is supplied from the air feed nozzles 41c, and makes fuels whose particles are relatively large and heavy radially consistently supplied into the combustion chamber 11 in the neighborhood of the fuel supply tube 41 by the fuel supply element 42b, to thereby prevent clinkers from blocking the air feed nozzles 41c. Accordingly, the present invention can solve conventional problems of incompletely burning fuels that are continuously piled up to the upper portion of the fuel supply tube since the fuels contact combustion air in a small area, and preventing the fuels that are not discharged to the outer side of the fuel supply tube from being produced into clinkers that prevent the fuels from being burnt.
And the solid fuels supplied into the combustion chamber 11 are preheated and ignited by a preheating burner (not shown) and an ignition burner (not shown), to then be burnt. The solid fuels supplied to the upper side of the rotary type fire grate 17 are burnt and moves to the edge of the rotary type fire grate 17 due to a continuous supply of fuels as time passes. The fuels whose portion is changed into liquid-phase fuels as the solid fuels are burnt, stay and are burnt in a V-shaped gully portion whose cross-section is the same as that of the rotary type fire grate 17. Accordingly, a problem that the liquid-phase fuels that have been produced during performing a combustion process flows down in the case that cross-section of the rotary type fire grate is slantly formed only in one direction, can be solved. In addition, ashes that have been produced as the fuels have been burnt are discharged through an ash ejection outlet 19 at the edge of the rotary type fire grate 17, during rotation of the rotary type fire grate 17.
Meanwhile, when the solid fuels are burnt in the combustion chamber 11, cooling water is introduced into a cooling chamber 13 through a cooling water inlet 14a of the cooling chamber 13 that is formed at the outer circumference of the inner wall 12 of the combustion chamber 11 and the introduced cooling water is rotated and raised up by a cooling water guide plate 13a to thereby cool the inner wall 12 to then be discharged through a cooling water outlet 14b. Then, the cooling water discharged from the cooling chamber 13 is stored in a boiler feed water tank 61 via a connection tube 62, and then is introduced into a boiler 60, to thereby collect heat from the hot combustion gases by a heat exchanging process. As described above, the combustion apparatus according to the present invention includes the cooling chamber 13 that is formed at the outer circumference of the inner wall 12 of the combustion chamber 11, to thereby prevent durability from being lowered due to an excessive temperature rise of the inner wall 12 of the combustion chamber 11. In addition, according to the combustion apparatus according to the present invention, the cooling water is preheated through the heat exchanging process with respect to the inner wall 12 of the cooling chamber 13, and then is introduced into the boiler 60 again, to thereby collect heat from the hot combustion gases that have been generated by the combustion apparatus according to the present invention, and to thus prevent durability from being lowered due to deform, deterioration or crack that may occur at the inner wall 12 of the combustion chamber 11 that is continuously exposed to the hot combustion gases, and simultaneously avoid an unnecessary loss of heat to accordingly enhance a thermal efficiency.
In addition, combustion air necessary for burning solid fuels is fed to the combustion chamber 11 through the lateral combustion air supply chamber 15, the upper combustion air supply chamber 20, and the lower combustion air supply tube 43 from the outside. First, the combustion air supplied through the air supply inlet 16a that is formed in a tangential direction with respect to the upper portion of the outer wall 16 of the cylindrical combustion vessel 100 turns and falls down in the lateral combustion air supply chamber 15, to then be supplied into the combustion chamber 11 through the opened lower portion 12a of the lateral combustion air supply chamber 15. Thus, the combustion air is supplied while turning, in the lateral combustion air supply chamber 15, that is, at the lateral surface of the combustion chamber 11. As a result, although the combustion chamber 11 is small in comparison with a case where combustion air is supplied in a straight line direction with respect to the fuels, the combustion air is directly in contact with most of the fuels, to thereby lower a manufacturing cost and enhance a thermal efficiency.
In addition, the combustion air is supplied into the preheating chamber 25 through the upper combustion air supply inlet 26a that is formed in the upper combustion air supply chamber 20 in a tangential direction with respect to the upper outer wall 26 of the cylindrical combustion vessel 100, and the combustion air supplied to the preheating chamber 25 moves to the upper portion of the preheating chamber 25 and then is again supplied to the swirl flow supply chamber 23 through the air passage 24a of the upper intermediate wall 24. The combustion air supplied to the swirl flow supply chamber 23 moves from the upper portion of the swirl flow supply chamber 23 to the lower portion thereof, and then is supplied while turning from the lateral surface of the upper portion of the combustion chamber 11 into the inside of the combustion chamber 11 through the combustion air supply passage 22a that is formed in the upper inner wall 22. Thus, the external air moves to the upper portion of the preheating chamber 25 in the upper combustion air supply chamber 20 and then moves again to the lower portion of the swirl flow supply chamber 23. As a result, since the moving distance of the external air becomes long, a more effective preheating effect can be obtained in the swirl flow supply chamber 23, and simultaneously the preheating chamber 25 can also perform a heat isolation function from the swirl flow supply chamber 23 to the outside thereof. In addition, the combustion air supplied from the lateral combustion air supply chamber 15 plays a role of directly burning the solid fuels loaded on the fire grate 17 and the combustion air supplied from the upper combustion air supply chamber 20 plays a role of burning the incomplete combustion matters that are generated from the solid fuels that have not been completely burnt and risen up, to thereby attempt perfect combustion of the solid fuels.
On the following, a method of injecting combustion air by the lower combustion air supply tube 43 will be described. The combustion air that is supplied by the lower combustion air supply tube 43 that is formed at the outer side of the fuel supply tube 41 is supplied into the combustion chamber 11 through the air feed nozzles 41c that are formed at the diameter enlargement portion 41a of the fuel supply tube 41, and thus is supplied to the lower portion of the solid fuels loaded in the combustion chamber 11. Accordingly, the outer portion of the solid fuels loaded in the combustion chamber 11 as well as the lower and inner portions of the solid fuels are also smoothly burnt, to thereby enhance a thermal efficiency.
Meanwhile, the hot combustion gases of high temperature that has been generated by burning the solid fuels in the combustion chamber 11 are introduced into the boiler 60 through the opened upper portion of the combustion chamber 11, and the hot combustion gases that have been supplied to the boiler 60 are used to generate hot water or steam for an industrial purpose by a heat exchanging process.
As described above, in the present invention, since the swirl flow is generated and is swirled in the combustion chamber 11, most of the fuel may be contacted with the combustion air even though the combustion chamber 11 and the fire grate are small; therefore, it is possible to reduce the manufacturing cost and to design for complete combustion because the combustion air is continuously supplied directly to the solid fuel, at the same time, it is possible to increase the temperature of the combustion gas generated by the combustion of the fuel and to improve the thermal efficiency.
In addition, if a conventional incinerator burns a high calorie fuel like RPF and so on that the present invention uses, the inner wall of the combustion chamber of the conventional incinerator may be melted down due to an excessive temperature rise of the combustion chamber, but the combustion apparatus according to the present invention includes the cooling chamber 13 that is formed at the outer circumference of the inner wall 12 of the combustion chamber 11, to thereby overcome the problem of the conventional incinerator and prevent durability from being lowered due to an excessive temperature rise of the inner wall of the combustion chamber.
As described above, an example of using solid fuels has been described in a combustion apparatus according to a preferred embodiment of the present invention. However, the combustion apparatus according to the present invention is not limited to the example of using the solid fuels but can be applied to examples of using gas fuels or liquid fuels.
Although the present invention has been described in detail with respect to the limited embodiments and drawings, it is not limited thereto. It is apparent to one who has an ordinary skill in the art that there may be a number of modifications and variations within the same technical spirit of the invention. It is natural that the modifications and variations belong to the following appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20-2010-7716 | Jul 2010 | KR | national |
| 10-2010-79534 | Aug 2010 | KR | national |
