Catalytic flameless combustion apparatus with extremely low pollutant emission and combustion method

Abstract

A catalytic flameless combustion apparatus has a fuel inlet, a combustion-supporting gas inlet, a gas premixer, a combustion plate, an igniter, a gas deflector, a flameless combustion cavity, a catalyst filled in the flameless combustion cavity, a gas collection chamber and an exhaust port. The method for starting the catalytic flameless combustion apparatus includes initially combusting and heating the flameless combustion cavity and the catalyst filled therein with low power flame; and then increasing flow velocity and switching to high power flame for conducting catalytic flameless combustion. The catalytic flameless combustion apparatus can be used for various non-solid fuel combustion and heat extraction processes.

Claims

1. A catalytic flameless combustion apparatus, comprising: a first housing having an upper end and a lower end closed by a plate, wherein at least one combustion-supporting gas inlet and at least one fuel inlet are disposed about the lower end of the first housing; a gas premixer disposed inside the first housing above the combustion-supporting gas inlet and the fuel inlet; a combustion plate disposed inside the first housing above the gas premixer; wherein a space between the lower end of the first housing and the combustion plate defines a gas premixing cavity, and the gas premixer resides in the gas premixing cavity; an igniter disposed inside the first housing above the combustion plate; a gas deflector having a tubular body with a lower opening and an upper opening; a second housing that defines a flameless combustion cavity and has a single opening opposed to the upper opening of the gas deflector; and a catalyst disposed inside the second housing, wherein the lower opening of the gas deflector is connected to the upper end of the first housing, and wherein the upper opening of the gas deflector is flush with the single opening in the second housing or extends into the flameless combustion cavity through the single opening in the second housing.

2. The catalytic flameless combustion apparatus according to claim 1, wherein the gas premixer is in the shape of a sheet, a rod, or a honeycomb monolith, and is connected to an inner wall of the first housing, wherein, during operation, the gas premixer causes changes in a flow direction of a combustion-supporting gas and in a flow direction of a fuel gas and thereby premixing the combustion-supporting gas and the fuel gas in the premixing cavity, wherein the combustion plate has a planar structure having pores or through holes that allow the premixed gas to pass through the combustion plate, wherein the through holes have a diameter or slit width of 0.01-10 mm and the combustion plate has a thickness of 0.1-1000 mm.

3. The catalytic flameless combustion apparatus according to claim 1, wherein the catalyst is fixedly supported by a bracket affixed to inner wall of the second housing flameless combustion cavity.

4. The catalytic flameless combustion apparatus according to claim 1, wherein an area of the opening in the second housing is 1.01-20 times of an area of the upper opening of the gas deflector.

5. The catalytic flameless combustion apparatus according to claim 1, further comprising a third housing having one or more exhaust ports, wherein the third housing is disposed about the second housing, forming a gas collection chamber between an outer wall of the seconding housing and the inner wall of the third housing.

6. The catalytic flameless combustion apparatus according to claim 1, further comprising a fixing bracket for affixing the second housing.

7. The catalytic flameless combustion apparatus according to claim 5, wherein sectional area of the one or more exhaust ports is larger than an area of the upper opening of the gas deflector.

8. The catalytic flameless combustion apparatus according to claim 5, further comprising a heat exchanger disposed inside the second housing, on an outer wall of the second housing, or on an outer wall of the third housing, wherein the heat exchanger is a shell-and-tube heat exchanger, a finned type heat exchanger, or a plate type heat exchanger.

9. A method for operating the catalytic flameless combustion apparatus of claim 1, comprising: introducing an oxygen-containing combustion-supporting gas through the combusting-supporting gas inlet and a gaseous fuel through the fuel gas inlet at an air coefficient of 1.01-2.5; mixing air and the fuel gas in the gas premixing cavity to form a premixed gas; controlling a linear velocity of the premixed gas to between a tempering linear velocity and a flame blowoff linear velocity according to tempering linear velocity and flame blowoff linear velocity; igniting the premixed gas using the igniter; heating the catalyst disposed in the flameless combustion cavity to above 600 C.; increasing the linear velocity of the premixed gas to above the flame blowoff linear velocity to extinguish a flame; carrying out flameless combustion of the premixed gas on the catalyst; and discharging a tail gas through the one or more exhaust ports in the third housing.

10. The method according to claim 9, wherein the combustion-supporting gas is air, oxygen, or an oxygen-containing mixed gas with oxygen content of 1-99.9 vol % other than air, and wherein the gaseous fuel is natural gas, coal gas, and liquefied petroleum gas, gasoline, diesel fuel, kerosene, alcohol, or methanol.

11. The catalytic flameless combustion apparatus according to claim 1, wherein the catalyst comprises a carrier and a metal oxide active component, wherein the carrier is ceramics, quartz, spinel, carborundum, stainless steel with fibrous, granules, or a honeycomb monolith, wherein the metal oxide active components is aluminum oxide, cerium oxide, magnesium oxide, lanthanum oxide, titanium oxide, ferric oxide, manganese oxide, silicon oxide, sodium oxide, copper oxide, nickel oxide, powder blue, platinic oxide, palladium oxide, ruthenium oxide, rhodium oxide, silver oxide, or a mixture thereof, wherein the metal oxide active component has a mass percentage of 0.1%-85% of the catalyst.

12. The method according to claim 1, wherein the catalyst comprises a carrier and a metal oxide active component, wherein the carrier is ceramics, quartz, spinel, carborundum, stainless steel with fibrous, granules, or a honeycomb monolith, wherein the metal oxide active components is aluminum oxide, cerium oxide, magnesium oxide, lanthanum oxide, titanium oxide, ferric oxide, manganese oxide, silicon oxide, sodium oxide, copper oxide, nickel oxide, powder blue, platinic oxide, palladium oxide, ruthenium oxide, rhodium oxide, silver oxide, or a mixture thereof, wherein the metal oxide active component has a mass percentage of 0.1%-85% of the catalyst.

Description

DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a schematic diagram of a catalytic flameless combustion apparatus according to embodiments of the present invention.

(2) Reference Signs:

(3) combustion-supporting gas inlet (1); fuel inlet (2); gas premixer (3); gas premixing cavity (4); combustion plate (5); igniter (6); gas deflector (7); flameless combustion cavity (8); catalyst (9); fixing bracket (10); gas collection chamber (11); and exhaust port (12).

(4) In the figure, a single-dashed arrow represents the flow direction of air; a single-solid arrow represents the flow direction of gas; a double-dashed arrow represents the flow direction of premixed gas; and a double-solid arrow represents the flow direction of flue gas.

(5) FIG. 2 is a schematic diagram of a catalytic flameless combustion apparatus with a heat exchanger according to embodiments of the present invention.

(6) Reference Signs:

(7) combustion-supporting gas inlet (1); fuel inlet (2); gas premixer (3); gas premixing cavity (4); combustion plate (5); igniter (6); gas deflector (7); flameless combustion cavity (8); catalyst (9); fixing bracket (10); gas collection chamber (11); exhaust port (12); finned type heat exchanger (13); heat-conducting fluid inlet (14); and heat-conducting fluid outlet (15).

(8) In the figure, a single-dashed arrow represents the flow direction of air; a single-solid arrow represents the flow direction of gas; a double-dashed arrow represents the flow direction of premixed gas; and a double-solid arrow represents the flow direction of flue gas.

DETAILED DESCRIPTION

(9) Embodiments of the present invention will be described below in detail. Examples of the embodiments are shown in drawings. Embodiments described below by reference to the drawings are exemplary embodiments, and are used for explaining the present invention, and shall not be understood as a limitation to the present invention.

(10) The embodiments of the catalytic flameless combustion apparatus of the present invention are specifically described below in combination with FIG. 1 and FIG. 2.

Embodiment 1

(11) As shown in FIG. 1, a catalytic flameless combustion apparatus comprises a hollow cylinder with an upper opening end and a lower closed end, wherein one combustion-supporting gas inlet 1 and one fuel inlet 2 are arranged on the bottom end of the cylinder; a gas premixer 3 is arranged above the combustion-supporting gas inlet 1 and the fuel inlet 2 on the middle lower part of the cylinder; a combustion plate 5 is arranged above the gas premixer 3; a gap is reserved between the bottom end of the cylinder and the combustion plate 5 to form a gas premixing cavity 4; the gas premixer 3 is placed in the gas premixing cavity 4; an igniter 6 is arranged above the combustion plate 5; a gas deflector 7 is arranged on the upper opening end of the cylinder; the gas deflector 7 is a hollow cylindrical duct with upper and lower opening ends; the lower opening end of the cylindrical duct is in airtight connection with the upper opening end of the hollow cylinder; a flameless combustion cavity 8 is arranged above the gas deflector 7; the flameless combustion cavity 8 is a hollow container with a lower opening end and an upper closed end; the upper opening end of the gas deflector 7 is opposite to the lower opening end of the flameless combustion cavity 8; the upper opening end of the gas deflector 7 extends from the lower opening end of the flameless combustion cavity 8 into the flameless combustion cavity 8; and a catalyst 9 is filled in the middle upper part in the flameless combustion cavity 8. The flameless combustion cavity 8 is fixedly connected to the hollow container in which the gas collection chamber 11 is placed through a fixing bracket 10. The gas collection chamber 11 is a hollow container which is provided with an exhaust port 12; and the gas collection chamber 11 wraps the lower opening end of the flameless combustion cavity 8 into the hollow containing cavity.

(12) Optionally, the hollow cylinder has a diameter of 100 mm. Air enters the combustion-supporting gas inlet 1. Natural gas enters the fuel inlet 2. The gas premixer 3 is cordierite ceramics with 200 meshes and thickness of 25.4 mm. The gas is uniformly mixed in the premixing cavity 4. The combustion plate 5 is cordierite ceramics with 400 meshes. The combustion plate has a thickness of 25.4 mm. The igniter 6 can ignite the premixed gas which passes through the combustion plate 5. The outlet of the gas deflector 7 is circular, and is opposite to the inlet of the flameless combustion cavity 8. The outlet of the gas deflector 7 has a diameter of 60 mm. The cross-sectional area of the inlet of the flameless combustion cavity 8 is 1.8 times of the cross-sectional area of the outlet of the deflector 7. The outlet of the deflector 7 extends into the inlet of the flameless combustion cavity 8 by 10 mm. The section of the outlet of the gas deflector 7 is a plane. The flameless combustion cavity 8 is a cylindrical cavity with an opening end, and has a depth of 60 mm. The inlet of the flameless combustion cavity 8 is a circle with a diameter of 80 mm. The catalyst 9 is placed in the flameless combustion cavity 8, and is fixedly supported by the bracket on the inner wall of the flameless combustion cavity 8. The catalyst fills 70% of volume of the flameless combustion cavity, and can adequately contact the gas which completely enters the flameless combustion cavity 8 through the outlet of the gas deflector 7. The catalyst 9 comprises porous ceramic material and metal oxide active components with a mass fraction of 40%. The flameless combustion cavity 8 is fixed to a position near the outlet of the deflector 7 by the fixing bracket 10, and can be connected with the gas collection chamber 11 or the deflector or the premixing cavity. The gas collection chamber 11 can collect the combusted tail gas and discharge the combusted tail gas through the exhaust port 12. The exhaust port 12 can be installed on the top of the gas collection chamber 11. The cross-sectional area of the exhaust port is 2 times of the cross-sectional area of the outlet of the gas deflector 7.

(13) Advantageously, after the combustion-supporting gas enters the combustion-supporting gas inlet 1, the combustion-supporting gas is offset with the airflow of the fuel gas which enters the fuel inlet 2 to increase a mixing effect of the combustion-supporting gas and the fuel airflow in the premixing cavity 4 through the premixer 3. The combustion plate 5 has air holes of 1 mm. The igniter 6 is an ignition needle. The deflector 7 extends into the flameless combustion cavity 8 by 15 mm. The area of the gap between the deflector 7 and the flameless combustion cavity 8 is 2.2 times of the cross-sectional area of the deflector 7. The area of the gap between the gas collection chamber and the flameless combustion cavity 8 is 2.5 times of the cross-sectional area of the deflector 7.

Embodiment 2

(14) As shown in FIG. 2, a catalytic flameless combustion apparatus with a heat exchanger comprises a hollow cylinder with an upper opening end and a lower closed end, wherein one combustion-supporting gas inlet 1 and one fuel inlet 2 are arranged on the bottom end of the cylinder; a gas premixer 3 is arranged above the combustion-supporting gas inlet 1 and the fuel inlet 2 on the middle lower part of the cylinder; a combustion plate 5 is arranged above the gas premixer 3; a gap is reserved between the bottom end of the cylinder and the combustion plate 5 to form a gas premixing cavity 4; the gas premixer 3 is placed in the gas premixing cavity 4; an igniter 6 is arranged above the combustion plate 5; a gas deflector 7 is arranged on the upper opening end of the cylinder; the gas deflector 7 is a hollow cylindrical duct with upper and lower opening ends; the lower opening end of the cylindrical duct is in airtight connection with the upper opening end of the hollow cylinder; a flameless combustion cavity 8 is arranged above the gas deflector 7; the flameless combustion cavity 8 is a hollow semi-spherical container with a lower opening end and an upper closed end; the upper opening end of the gas deflector 7 is opposite to the lower opening end of the flameless combustion cavity 8; the upper opening end of the gas deflector 7 extends from the lower opening end of the flameless combustion cavity 8 into the flameless combustion cavity 8; and a catalyst 9 is filled in the middle upper part in the flameless combustion cavity 8. The flameless combustion cavity 8 is fixedly connected to the hollow container in which the gas collection chamber 11 is placed through a fixing bracket 10. The gas collection chamber 11 is a hollow container which is provided with an exhaust port 12; and the gas collection chamber 11 wraps the lower opening end of the flameless combustion cavity 8 into the hollow containing cavity. The finned type heat transfer apparatuses are installed above the flameless combustion cavity 8 in the gas collection chamber 11 and on the outer wall surface of the gas collection chamber 11. The water enters the heat-conducting fluid inlet 14 by using the water as heat-conducting fluid. The water flows out from the heat-conducting fluid outlet 15 after heat transfer by the finned type heat exchanger.

(15) Optionally, the hollow cylinder has a diameter of 80 mm. Air enters the combustion-supporting gas inlet 1. Natural gas enters the fuel inlet 2. The gas premixer 3 is cordierite ceramics with 200 meshes and thickness of 12 mm. The gas is uniformly mixed in the premixing cavity 4. The combustion plate 5 is cordierite ceramics with 300 meshes. The combustion plate has a thickness of 20 mm. The igniter 6 can ignite the premixed gas which passes through the combustion plate 5. The outlet of the gas deflector 7 is circular, and is opposite to the inlet of the flameless combustion cavity 8. The outlet of the gas deflector 7 has a diameter of 50 mm. The cross-sectional area of the inlet of the flameless combustion cavity 8 is 1.5 times of the cross-sectional area of the outlet of the deflector 7. The outlet of the deflector 7 extends into the inlet of the flameless combustion cavity 8 by 5 mm. The section of the outlet of the gas deflector 7 is a plane. The flameless combustion cavity 8 is a semi-spherical cavity with an opening end, and has a depth of 40 mm. The inlet of the flameless combustion cavity 8 is a circle with a diameter of 70 mm. The catalyst 9 is placed in the flameless combustion cavity 8, and is fixedly supported by the bracket on the inner wall of the flameless combustion cavity 8. The catalyst fills 60% of volume of the flameless combustion cavity, and can adequately contact the gas which completely enters the flameless combustion cavity 8 through the outlet of the gas deflector 7. The catalyst 9 comprises porous ceramic material and metal oxide active components with a mass fraction of 30%. The flameless combustion cavity 8 is fixed to a position near the outlet of the deflector 7 by the fixing bracket 10, and can be connected with the gas collection chamber 11 or the deflector or the premixing cavity. The gas collection chamber 11 can collect the combusted tail gas and the combusted tail gas flows through the finned type heat exchanger 13. After heat transfer on the heat-conducting fluid which comes in and out through the heat-conducting fluid inlet 14 and outlet 15, the heat-conducting fluid is discharged through the exhaust port 12. The exhaust port 12 can be installed on the top of the gas collection chamber 11. The cross-sectional area of the exhaust port is 2 times of the cross-sectional area of the outlet of the gas deflector 7.

Embodiment 3

(16) A multikilowatt natural gas catalytic flameless combustion apparatus with rated thermal power of 20 KW takes the structure shown in FIG. 2. The hollow cylinder has a diameter of 70 mm. The combustion-supporting gas inlet 1 is a stainless steel pipe with an inside diameter of 40 mm. The combustion-supporting gas is volume-adjustable air supplied by a stepless speed change blower. The gas inlet 2 is a stainless steel pipe with an inside diameter of 9 mm. The gas is flow-adjustable natural gas (methane) controlled by an electromagnetic valve. The gas premixer 3 is cordierite ceramics with 200 meshes and thickness of 12 mm. The gas is uniformly mixed in the premixing cavity 4. The combustion plate 5 is cordierite ceramics with 300 meshes. The combustion plate has a thickness of 20 mm. The premixing cavity 4 is a stainless steel pipe with an inside diameter of 65 mm. The gas deflector 7 is a circular ring connected to the inner wall of the premixing cavity 4, and has an upward oblique angle of 75 degrees and an outlet diameter of 50 mm. The outlet of the deflector 7 extends into the inlet of the flameless combustion cavity 8 by 5 mm. The section of the outlet of the gas deflector 7 is a plane. The flameless combustion cavity 8 is a semi-spherical cavity with an opening end, and has a depth of 40 mm. The inlet of the flameless combustion cavity 8 is a circle with a diameter of 70 mm. The catalyst 9 is placed in the flameless combustion cavity 8, and is fixedly supported by the bracket on the inner wall of the flameless combustion cavity 8. The catalyst fills 60% of volume of the flameless combustion cavity, and can adequately contact the gas which completely enters the flameless combustion cavity 8 through the outlet of the gas deflector 7. The catalyst 9 comprises porous ceramic material and metal oxide active components with a mass fraction of 30%. The heat exchanger 13 is placed on the upper half part of the gas collection chamber 11. The heat-conducting fluid is the water. The exhaust port is a stainless steel pipe with an inside diameter of 70 mm.

(17) The following operation method is adopted: during ignition, the methane flow velocity is controlled as 7 L/min, and the air flow velocity is controlled as 80 L/min, i.e., the air coefficient is 1.20, linear velocity is 0.5 m/s and thermal power is about 4.6 KW. Under this combustion of low power flame, emission values of CO, HC and NO.sub.x are 0 (detector resolution is 1 ppm). After combustion for 20 s, the combustion chamber and the catalyst can be red hot. At this moment, the air coefficient is kept as 1.20. The methane flow velocity is increased as 30 L/min within 1 minute. The air flow velocity is increased as 345 L/min, i.e., the linear velocity is 2.0 m/s and the thermal power reaches 20 KW. When and after the flow is increased, the emission values of CO, HC and NO.sub.x are 0 (detector resolution is 1 ppm). After continuous combustion for 3 hours, the emission values of CO, HC and NO.sub.x are always 0. The beneficial effects realized by the multikilowatt natural gas catalytic flameless combustion apparatus with rated power of 20 KW and the above used method are: the fuel is completely combusted; heat transfer efficiency is more than 95%; and the emission values of pollutants CO, HC and NO.sub.x are 0 (lower than 1 ppm).

Embodiment 4

(18) A multikilowatt natural gas catalytic flameless combustion apparatus with rated thermal power of 80 KW takes the structure shown in FIG. 2. The hollow cylinder has a diameter of 150 mm. The combustion-supporting gas inlet 1 is a stainless steel pipe with an inside diameter of 100 mm. The combustion-supporting gas is volume-adjustable air supplied by a stepless speed change blower. The gas inlet 2 is a stainless steel pipe with an inside diameter of 30 mm. The gas is flow-adjustable natural gas (methane) controlled by an electromagnetic valve. The gas premixer 3 is cordierite ceramics with 200 meshes and thickness of 25.4 mm. The gas is uniformly mixed in the premixing cavity 4. The combustion plate 5 is cordierite ceramics with 300 meshes. The combustion plate has a thickness of 40 mm. The premixing cavity 4 is a stainless steel pipe with an inside diameter of 150 mm. The gas deflector 7 is a circular ring connected to the inner wall of the premixing cavity 4, and has an upward oblique angle of 75 degrees and an outlet diameter of 100 mm. The outlet of the deflector 7 extends into the inlet of the flameless combustion cavity 8 by 20 mm. The section of the outlet of the gas deflector 7 is a plane. The flameless combustion cavity 8 is a semi-spherical cavity with an opening end, and has a depth of 60 mm. The inlet of the flameless combustion cavity 8 is a circle with a diameter of 160 mm. The catalyst 9 is placed in the flameless combustion cavity 8, and is fixedly supported by the bracket on the inner wall of the flameless combustion cavity 8. The catalyst fills 70% of volume of the flameless combustion cavity, and can adequately contact the gas which completely enters the flameless combustion cavity 8 through the outlet of the gas deflector 7. The catalyst 9 comprises porous ceramic material and metal oxide active components with a mass fraction of 50%. The heat exchanger 13 is placed on the upper half part of the gas collection chamber 11. The heat-conducting fluid is the water. The exhaust port is a stainless steel pipe with an inside diameter of 120 mm.

(19) The following operation method is adopted: during ignition, the methane flow velocity is controlled as 14 L/min, and the air flow velocity is controlled as 160 L/min, i.e., the air coefficient is 1.20, linear velocity is 0.35 m/s and thermal power is about 9.3 KW. Under this combustion of low power flame, emission values of CO, HC and NO.sub.x are 0 (detector resolution is 1 ppm). After combustion for 15 s, the combustion chamber and the catalyst can be red hot. At this moment, the air coefficient is kept as 1.20. The methane flow velocity is increased as 120 L/min within 1 minute. The air flow velocity is increased as 1380 L/min, i.e., the linear velocity is 3.2 m/s and the thermal power reaches 80 KW. When and after the flow is increased, the emission values of CO, HC and NO.sub.x are 0 (detector resolution is 1 ppm). After continuous combustion for 2 hours, the emission values of CO, HC and NO.sub.x are always 0. The beneficial effects realized by the multikilowatt natural gas catalytic flameless combustion apparatus with rated power of 80 KW and the above used method are: the fuel is completely combusted; heat transfer efficiency is more than 95%; and the emission values of pollutants CO, HC and NO.sub.x are 0 (lower than 1 ppm).

Embodiment 5

(20) A megawatt natural gas catalytic flameless combustion apparatus with rated thermal power of 1.2 MW is formed by combining 15 groups of catalytic flameless combustors each having 80 KW in embodiment 4.

Embodiment 6

(21) A megawatt natural gas catalytic flameless combustion apparatus with rated thermal power of 2.1 MW takes the structure shown in FIG. 2. The hollow cylinder has a diameter of 400 mm. The combustion-supporting gas inlet 1 is a stainless steel pipe with an inside diameter of 200 mm. The combustion-supporting gas is volume-adjustable air supplied by a stepless speed change blower. The gas inlet 2 is a stainless steel pipe with an inside diameter of 60 mm. The gas is flow-adjustable natural gas (methane) controlled by an electromagnetic valve. The gas premixer 3 is cordierite ceramics with 200 meshes and thickness of 50 mm. The gas is uniformly mixed in the premixing cavity 4. The combustion plate 5 is cordierite ceramics with 400 meshes. The combustion plate has a thickness of 60 mm. The premixing cavity 4 is a stainless steel pipe with an inside diameter of 400 mm. The gas deflector 7 is a circular ring connected to the inner wall of the premixing cavity 4, and has an upward oblique angle of 75 degrees and an outlet diameter of 350 mm. The outlet of the deflector 7 extends into the inlet of the flameless combustion cavity 8 by 100 mm. The section of the outlet of the gas deflector 7 is a plane. The flameless combustion cavity 8 is a semi-spherical cavity with an opening end, and has a depth of 360 mm. The inlet of the flameless combustion cavity 8 is a circle with a diameter of 550 mm. The catalyst 9 is placed in the flameless combustion cavity 8, and is fixedly supported by the bracket on the inner wall of the flameless combustion cavity 8. The catalyst fills 60% of volume of the flameless combustion cavity, and can adequately contact the gas which completely enters the flameless combustion cavity 8 through the outlet of the gas deflector 7. The catalyst 9 comprises porous ceramic material and metal oxide active components with a mass fraction of 50%. The heat exchanger 13 is placed on the upper half part of the gas collection chamber 11. The heat-conducting fluid is the water. The exhaust port is a stainless steel pipe with an inside diameter of 240 mm. It should be understood in the description of the present invention that terms such as length, width, thickness, upper, lower, top, bottom, inner, outer, flow direction, etc. indicate direction or position relationships shown based on the drawings, and are only intended to facilitate the description of the present invention and the simplification of the description rather than to indicate or imply that the indicated device or element must have a specific direction or constructed and operated in a specific direction, and therefore, shall not be understood as a limitation to the present invention.

(22) Although the explanatory embodiments of the present invention have been disclosed in detail with reference to the attached drawings, it should be understood that the present invention is not limited to exact embodiments. The present invention may be changed and modified by those skilled in the art without departing from the scope of the present invention as defined by the scope of the patent application and its equivalent.