WO2009119925A1

WO2009119925A1 - Circular type air injection nozzles having two circular slits and filter cleaning system using them

Info

Publication number: WO2009119925A1
Application number: PCT/KR2008/001719
Authority: WO
Inventors: Hyun-Sul Park; Kyung-Soo Lim
Original assignee: Korea Institute Of Energy Research
Priority date: 2008-03-27
Filing date: 2008-03-27
Publication date: 2009-10-01
Also published as: CN101808710A; CN101808710B

Abstract

There are provided circular type air injection nozzles having two circular slits by generating the Coanda effect, and a filter cleaning system using them and more particularly, circular type air injection nozzles having two circular slits by using the Coanda effect, the air injection nozzle in which two circumferential type air injection slits are formed around inner and outer peripheries of the air injection nozzle and the Coanda effect is generated when injecting compressed air through the slits at high speed so that the injected air flows along a surface of a guide inside the air injection nozzle and then nearby air being several tens of times an amount of the injected air drawn from the inside and outside of the air injection nozzle is guided to the inside of the filter, and a filter cleaning system using them. The present invention as described has the feature of remarkably improving the performance of the cleaning system.

Description

CIRCULAR TYPE AIR INJECTION NOZZLES HAVING TWO CIRCULAR SLITS AND FILTER CLEANING SYSTEM USING

THEM

Technical Field

[1] The present invention relates to circular type air injection nozzles having two circular slits by generating the Coanda effect, and a filter cleaning system using them, and more particularly, circular type air injection nozzles having two circular slits by using the Coanda effect, the air injection nozzle in which two circumferential type air injection slits are formed around inner and outer peripheries of the air injection nozzle and the Coanda effect is generated when injecting compressed air through the slits at high speed so that the injected air flows along a surface of a guide inside the air injection nozzle and then nearby air being several tens of times an amount of the injected air drawn from the inside and outside of the air injection nozzle is guided to the inside of the filter, and a filter cleaning system using them. Background Art

[2] In general, when dust particles are collected on dust filters of a filter dust collector for removal of dust particles generated during various industrial processes, air resistance across the filters increases and therefore it is necessary to remove dust collected on the surface of the dust filters. In the filter dust collector, a pulse jet cleaning method is most generally applied. In this method, an air injection nozzle momentarily injects compressed air so that the dust filter expands and thus the dust collected on the surface of the filter is removed.

[3] In Korean Application Nos. 20-2005-16238 (entitled: "System for cleaning dust collector"), 20-1997-26955 (entitled: "Nozzle for cleaning dust collector"), and 20-1995-17896 (entitled: "Air injection nozzle for cleaning bag filter"), there are disclosed conventional technologies regarding a system for cleaning a dust filter and an air injection nozzle for cleaning a dust filter, using the pulse jet cleaning method.

[4] However, the nozzle used in the aforementioned existing cleaning system of a dust collecting filter has complicate constitution or needs to be individually controlled. Due to these reasons, the existing cleaning systems of a dust collecting filter are difficult to be maintained or repaired or they incur high installation costs.

[5] For example, in the filter cleaning system a filter dust collector (Korean Application

No. 20-2005-16238), one of the aforementioned existing systems, since each nozzle includes an actuator and packing, its installation cost is excessively high. Moreover, since actuators need to be individually repaired, the system is difficult to be maintained or repaired.

Disclosure of Invention

Technical Problem

[6] Therefore, the present invention has been made to solve the above problems, and it is an aspect of the present invention to provide circular type air injection nozzles having two circular slits by generating the Coanda effect, and a filter cleaning system using them, whereby improving the dust collecting efficiency of the dust collecting filter and remarkably improving the performance of the dust filter cleaning system. Technical Solution

[7] In accordance with an aspect of the present invention, the above and other aspects can be accomplished by circular type air injection nozzles mounted to injection pipes of a dust filter cleaning system, each circular type air injection nozzle comprising: an upper annular guide shaped as a upper half torus and having inlet holes formed at its top side so as to correspond to the holes of the injection pipe; a lower annular guide positioned under the upper annular guide and configured by rotating a streamlined cross section; and a connection part connecting a top part of the lower guide with a lower part of the upper guide, to form an outer slit between an inner circumferential surface of an outer wall of the upper guide and an outer circumferential surface of the lower guide, to form an inner slit between an inner circumferential surface of an inner wall of the upper guide and an inner circumferential surface of the lower guide, and to form a space inside the upper guide above the top of the lower guide.

[8] In accordance with another aspect of the present invention, there is provided a dust filter cleaning system using a circular type air injection nozzle having two circular slits, the system comprising: a cleaning air storage tank positioned outside of the filter dust collector; a number of injection pipes, positioned on vertical tops of dust collecting filters mounted in the filter dust collector, each of which includes a number of air ejection holes formed at equal interval in the length direction and has one end being connected with a cleaning air control valve by equal interval in the length direction of the cleaning air storage tank and the other end being closed; and a number of cleaning air control valves each including a control unit positioned outside the cleaning air storage tank and a valve unit having one end connected to each control unit and the other end connected to one end of each injection pipe, wherein the circular type air injection nozzle and the injection pipe are coupled by a clamp which is fixed at both sides of the upper annular guide nearby both sides of a saddle connector in contact with the circumference of the injection pipe. The saddle connector forming a connection opening from its top to bottom is interposed between the injection pipe and the upper guide of annular air injection nozzle so that each hole of injection pipe is op- eratively connected to each inlet hole of upper guide.

Advantageous Effects

[9] In the circular type air injection nozzles having two circular slits and the dust filter cleaning system using them in accordance with the present invention, since the air injection nozzle generates the Coanda effect, the filter cleaning performance is high even though low pressure air is used for cleaning. Therefore, the energy cost for filter cleaning is reduced, the use life of the dust collecting filter is prolonged, and the dust collection efficiency of the dust collector is improved.

[10] Furthermore, in the filter cleaning system using the circular type air injection nozzles having two circular slits, the air injection nozzle is controlled externally. Therefore, the air injection nozzle does not need a separate repair process unless it corrodes or is damaged. Consequently, the system is easily maintained or repaired. Brief Description of the Drawings

[11] These and other aspects and advantages of the present invention will become apparent and more readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings, in which:

[12] FIG. 1 illustrates a filter dust collector for explaining the present invention;

[13] FIG. 2 is a sectional view of the filter dust collector of FIG. 1, taken along line A-A;

[14] FIG. 3 is a perspective view of a dissembled circular type air injection nozzle having two circular slits for cleaning a dust collecting filter according to an embodiment of the present invention, in which the configuration of coupling the air injection nozzle with an injection pipe is shown;

[15] FIG. 4 illustrates the air injection nozzle coupled to the injection pipe of FIG. 3;

[16] FIG. 5 illustrates the coupling relation of an upper guide of the circular type air injection nozzle and an injection pipe according to the embodiment of the present invention;

[17] FIG. 6 illustrates a circular type air injection nozzle having two circular slits for cleaning a dust collecting filter and a flow pattern of compressed air according to another embodiment of the present invention;

[18] FIG. 7 illustrates various examples of a lower guide of the circular type air injection nozzle having two circular slits, according to embodiments of the present invention;

[19] FIG. 8 illustrates an example of a coupling relation of the upper guide and the lower guide;

[20] FIG. 9 illustrates another example of the coupling relation of the upper guide and the lower guide;

[21] FIG. 10 is a referential view of the circular type air injection nozzles coupled to the injection pipe according to the embodiment of the present invention; [22] FIG. 11 is a perspective view of a dissembled circular type air injection nozzle having two circular slits according to another embodiment of the present invention;

[23] FIG. 12 is a sectional view of a dissembled circular type air injection nozzle having two circular slits, according to another embodiment of the present invention;

[24] FIG. 13 is a perspective view of a dissembled circular type air injection nozzle having two circular slits, according to another embodiment of the present invention;

[25] FIG. 14 is a sectional view of an exemplary configuration of an injection pipe in a dust collector cleaning system, using the circular type air injection nozzle having two circular slits, according to another embodiment of the present invention; and

[26] FIG. 15 a sectional view of another exemplary configuration of an injection pipe in a dust collector cleaning system, using the circular type air injection nozzle having two circular slits, according to another embodiment of the present invention.

[27] <Explanation on essential elements of drawings>

[28] 100: filter dust collector 7: dust collecting filter

[29] 9: air injection pipe

[30] 10: upper guide of a circular type air injection nozzle

[31] 20: lower guide of a circular type air injection nozzle

[32] 31: protruding inlet 41 : welding point

[33] 42: pin 50: saddle connector

[34] 61: cleaning air storage tank

[35] 62: control unit 63: valve unit

[36] 65: cleaning air control valve

[37] 70: fixing clamp

Mode for the Invention

[38] Prior to the detailed description of the present invention, a filter dust collection technology, an pulse jet cleaning method, and the Coanda effect related to the present invention will be explained below:

[39] The filter dust collection technology is to remove dust included in a processing gas by using dust collecting filters. When dust particles are collected on filters, the differential pressure across the filter increases. Thus, a process of periodically detaching dust collected on the surface of the filters is required and this is called filter cleaning hereinafter. Filter cleaning methods generally used in the filter dust collection technology include an pulse jet cleaning method of detaching dust from the filter surface by injecting compressed air momentarily, a reverse flow cleaning method of cleaning filters by supplying airflow in the opposite direction to the direction in which a processing gas passes through the filters, and a shaker cleaning method of cleaning filters by directly vibrating dust collecting filters. [40] Relating to the pulse jet cleaning method, an pulse jet cleaning apparatus generally comprises: a cleaning air storage tank for storing compressed air to be injected; a cleaning air control valve for controlling an amount of the compressed air transported from the cleaning air storage tank when cleaning; a number of cleaning air injection pipes for transferring the compressed air transported through the cleaning air control valve to each dust collecting filter; and a number of cleaning air injection nozzles attached to each cleaning air injection pipe, for actually injecting the compressed air to the inside of the dust collecting filters.

[41] Furthermore, in the pulse jet cleaning method, the cleaning air control valve is opened for a very short moment, less than 0.2 seconds, to allow the compressed air to be momentarily injected from the injection nozzle. Then, the directly injected air and the nearby air induced by high-speed injection flow into the dust collecting filter for a short moment, thereby expanding the dust collecting filter and removing dust deposited on the surface of the dust collecting filter. A filter cleaning system applying the pulse jet cleaning technique has been realized in various modes.

[42] The Coanda effect is a physical phenomenon discovered by Henri Coanda. When a fluid with high speed flows over a surface of an object, it moves fast along the surface of the object, and consequently the fluid pressure around the object becomes low. That is called the Coanda effect. The phenomenon appears when a moving fluid is injected through a narrow slit, such as a capillary tube, and a wall surface which is curved in the direction of the fluid flow exists nearby, the fluid flow is curved along the curved surface.

[43] For example, the Coanda effect is applied to an aircraft. While air passes over the wing having top and bottom surfaces of different curvatures, the pressure on the top surface decreases. Then, a lift force of the aircraft is generated by the action and reaction between the wing and the air which flows downwardly, along the wing surface at a faster speed.

[44] Therefore, the Coanda effect is applicable in various fields as well as the aircraft field. That is, the Coanda effect is widely applied to the industrial fields of installing diverse exhaust and ventilation, wires or optical fibers for communication, or cleaning large boilers.

[45] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[46] A dust collector used in the present invention is a filter dust collector 100. As illustrated in FIG. 1, the filter dust collector 100 comprises: a primary dust collecting chamber 1 in an inverted pyramid shape, to collect dust by inertial collision; a gas intake pipe 1 ' connected to the primary dust collecting chamber 1 ; a secondary dust collecting chamber 2 in a box shape, formed on the top of the primary dust collecting chamber 1 and including a number of dust collecting filters 7 to remove dust passing through the primary dust collecting chamber 1 ; a filter mounting plate 3 to fix a top of each dust collecting filter 7; a gas exhaust pipe 2' connected to a top side wall of the secondary dust collecting chamber 2 over the filter mounting plate 3; a cleaning system positioned inside and outside of the secondary dust collecting chamber 2, to detach dust deposited on each dust collecting filter 7; and a dust box 4 to receive and store dust separated from each dust collecting filter 7 by the filter cleaning system and dust moving down through the primary dust collecting chamber 1.

[47] A number of circular type air injection nozzles having two circular slits for cleaning the dust collecting filter according to the present invention (hereinafter, referred to as the 'injection nozzle') is mounted to an injection pipe 9 in a pulse jet type filter cleaning system. The injection pipe 9 injects a flow-in air through ejection holes 9' formed at the bottom of it. The injection nozzle comprises: an upper guide 10 of annular shape; a lower guide 20 of annular shape; and a connection part. The upper guide 10 is formed with inlet holes 10' at its one side (top part) so as to correspond to the ejection holes 9' of the injection pipe 9 and opened at its lower part. The lower guide 20 is positioned under the upper guide 10 and is configured by rotating and extending a streamlined cross section. The connection part connects a top part of the lower guide 20 with the lower part of the upper guide 10 by forming an outer slit Ll between an inner circumferential surface of an outer wall of the upper guide 10 and an outer circumferential surface of the lower guide 20 and an inner slit L2 between an inner circumferential surface of an inner wall of the upper guide 10 and an inner circumferential surface of the lower guide 20 while forming a space S inside the upper guide 10 above the top part of the lower guide 20.

[48] As described in FIGS. 3 and 4, the upper guide 10 has a structure opened at its lower part just like an upper half torus. A pair of inlet holes 10' is formed at the top part of the upper guide 10, so as to correspond to the ejection holes 9' formed on the injection pipe 9. When the number of the inlet holes 10' is even, the inlet holes 10' are formed so as to face opposite to each other, thereby stably mounting the upper guide 10 to the injection pipe 9.

[49] The upper guide 10 may further comprise a protruding inlet 31 extending from the inlet hole 10' upwardly by a predetermined length. Preferably, the extension length of the protruding inlet 31 may be the same as the depth of the ejection hole 9' of the injection pipe 9. The same extension length is preferable for a tight mounting of the upper guide 10 to a lower side of the injection pipe 9 when the protruding inlet 31 is coupled to the injection pipe 9.

[50] The lower guide 20 is positioned under the upper guide 10. The shape of the lower guide 20 is configured by rotating and extending a streamlined cross section. The lower guide 20 is connected to the upper guide 10 by a connection part.

[51] Then, preferably, the outer slit Ll and the inner slit L2 may be respectively formed between the inner circumferential surface of the outer wall of the upper guide 10 and the outer circumferential surface of the lower guide 20, and between the inner circumferential surface of the inner wall of the upper guide 10 and the inner circumferential surface of the lower guide 20. Preferably, the space S may be formed inside the upper guide 10 above the top part of the lower guide 20.

[52] The outer slit Ll and inner slit L2 may be formed within the range of 0.05 to 1.0 mm.

The outer slit Ll and the inner slit L2 may be formed within the range of 2 to 20 mm in height. An angle of inclination (θ) between one inside circumferential edge at the bottom of the lower guide 20 and a horizontal plane may be formed within the range of 30 to 150 degrees. For example, the angle of inclination, θ between one inside circumferential edge at the bottom of the lower guide 20 and a horizontal plane may be variously constituted as illustrated in FIG. 7.

[53] As illustrated in FIG. 8 and FIG. 9, the connection part may be a few of welding points formed in a shape of a few of dots 41 at equal intervals respectively to the outer slit Ll and the inner slit L2 to maintain the outer slit Ll and the inner slit L2 or the connection part may be a number of pins 42 forming flanges at both sides at equal intervals respectively to the outer slit Ll and inner slit L2 to maintain the outer slit Ll and the inner slit L2.

[54] A filter cleaning system of the filter dust collector 100 using the injection nozzles in the above-described constitution comprises: a cleaning air storage tank 61 positioned outside of the filter dust collector 100; a number of the injection pipes 9 positioned on vertical tops of the dust collecting filters 7 mounted in the filter dust collector, each injection pipe 9 having a number of the ejection holes 9' formed at equal interval in the length direction, one end being mounted by equal interval in the length direction of the cleaning air storage tank 61, and the other end being closed; and a number of cleaning air control valves 65 each including a control unit 62 positioned outside the cleaning air storage tank 61 and a valve unit 63 having one end connected to each control unit 62 and the other end connected to one end of each injection pipe 9, wherein the annular air injection nozzle and the injection pipe are coupled by a clamp 70, each of which is fixed at both sides of the upper annular guide 10 nearby both sides of a saddle connector 50 in contact with the circumference of the injection pipe 9. The saddle connector 50 forming a connection opening 51 from its top to bottom is interposed between the injection pipe 9 and the upper guide 10 of annular air injection nozzle so that each ejection hole 9 'of injection pipe 9 is operatively connected to each inlet hole 10' of upper guide 10.

[55] The cleaning air storage tank 61 is constituted to store compressed air of high pressure and is positioned outside the filter dust collector 100, as illustrated in FIG. 1.

[56] The dust collecting filter 7 is positioned in the secondary dust collecting chamber 2 inside the filter dust collector 100. A number of the dust collecting filters 7 are positioned in a predetermined arrangement and are constituted to be fixed to the filter mounting plate 3 and to remove dust contained in the processing gas.

[57] For example, the injection pipe 9 may be a cylindrical pipe having its one end being opened and the other end being closed. A number of the ejection holes 9' are formed on the bottom of the injection pipe 9, at equal interval, in the length direction of the injection pipe 9. In the injection pipe 9, the one end being opened is connected to one side of the cleaning air storage tank 61 and the other end being closed is fixed over the filter mounting plate 3 so as to be positioned at the vertical top of the dust collecting filter 7. One injection pipe 9 is installed for the dust collecting filters 7 that form one column. A number of the ejection holes 9' formed at equal interval on the injection pipe 9 are opposite to the dust collecting filters 7 in the vertical direction.

[58] The control valve 65 comprises a control unit 62 positioned outside the cleaning air storage tank 61, and a valve unit 63 having one end connected to the control unit 62 and the other end connected to the open end of each injection pipe 9.

[59] The saddle connector 50 is formed to be tightly contacted to an upper part of each inlet hole 10' of the upper guide 10 and to a lower part of each ejection hole 9' of the injection pipe 9. Through the connection opening 51 of the saddle connector 50, the ejection hole 9' is operatively connected to the inlet hole 10'. To secure air leakage- proof, the saddle connector 50 may be fixed by welding or may be attached by using an adhesive or the like between the upper guide 10 and the injection pipe 9. Preferably, the upper and lower parts of the connection opening 51 may be constituted to protrude so as to be same as the thickness of the bottom of the injection pipe 9 and the thickness of the top of the upper guide 10. The saddle connector 50 is not used when the protruding inlet 31 is formed on the upper guide 10.

[60] When the protruding inlet 31 is formed on the upper guide 10, the fixing clamp 70 is placed around the circumference of the injection pipe 9 and welded F at both sides of the upper guide 10 nearby the protruding inlet 31, thereby fixing the upper guide 10 to the injection pipe 9.

[61] Further, when the protruding inlet 31 is not formed on the upper guide 10, the saddle connector 50 is interposed between the upper guide 10 and the injection pipe 9, and the fixing clamp 70 is welded at both sides of the upper guide 10 nearby both sides of the saddle connector 50, thereby clamps the upper guide 10 to the injection pipe 9.

[62] In the present invention, to improve the straightness of air flow into the dust collecting filter 7, a number of branch apertures 9a may be formed at the bottom of the injection pipe 9, based on the center on the plane of the upper guide 10 of each injection nozzle connected to the injection pipe 9 or a number of branch tubes 9b may be further formed by being extended from each of the branch apertures 9a downwardly.

[63] The invention has been described using preferred exemplary embodiments. However, it is to be understood that the scope of the invention is not limited to the disclosed embodiments. On the contrary, the scope of the invention is intended to include various modifications and alternative arrangements within the capabilities of persons skilled in the art using presently known or future technologies and equivalents. The scope of the claims, therefore, should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.

Claims

[1] A circular type air injection nozzle mounted to an injection pipe (9) formed with ejection holes (9') at its bottom side, of a dust filter cleaning system, comprising: an annular upper guide (10) formed with inlet holes (10') at its one side (upper part) so as to correspond to the ejection holes (9') of the injection pipe (9) and opened at its lower part; an annular lower guide (20) positioned under the upper guide (10) and constituted by rotating and extending a streamlined cross section; and a connection part connecting the top of the lower guide (20) under the upper guide (10), to form an outer slit (Ll) between an inner circumferential surface of an outer wall of the upper guide (10) and an outer circumferential surface of the lower guide (20), to form an inner slit (L2) between an inner circumferential surface of an inner wall of the upper guide (10) and an inner circumferential surface of the lower guide (20), and to form a space (S) inside the upper guide (10) above the top part of the lower guide (20).

[2] The air injection nozzle according to claim 1, wherein the number of the inlet holes (10') formed on the top of the upper guide (10) is at least two or more.

[3] The air injection nozzle according to claim 2, wherein, when the number of the inlet holes (10') is even, the inlet holes (10') are formed in a symmetric structure that they correspond to each other.

[4] The air injection nozzle according to claim 2, wherein the upper guide (10) further comprises a protruding inlet 31 extended upwardly by a predetermined length from the inlet hole (10').

[5] The air injection nozzle according to claim 1, wherein the connection part is a number of welding points (41) formed in a shape of a number of dots at equal interval respectively to the outer slit (Ll) and inner slit (L2) to maintain the outer slit (Ll) and the inner slit (L2).

[6] The air injection nozzle according to claim 1, wherein the connection part is a number of pins (42) forming flanges at both sides at equal interval respectively to the outer slit (Ll) and the inner slit (L2) to maintain the outer slit (Ll) and the inner slit (L2).

[7] The air injection nozzle according to claim 1, wherein the outer slit (Ll) and the inner slit (L2) are 0.05 to 1.0 mm.

[8] The air injection nozzle according to claim 1, wherein the outer slit (Ll) and the inner slit (L2) are 2 to 20 mm in height.

[9] The air injection nozzle according to claim 1, wherein an angle of inclination (θ) between one side of the inside circumference edge at the bottom of the lower guide (20) and a horizontal plane is within the range of 30 to 150 degrees.

[10] A filter cleaning system of a filter dust collector (100) using the circular type air injection nozzle according to any one of claims 1, 2, 3, 5, 6, 7, 8 and 9, comprising: a cleaning air storage tank (61) positioned outside of the filter dust collector (100); a number of the injection pipes (9) positioned on vertical tops of dust collecting filters (7) mounted in the filter dust collector (100), each injection pipe (9) having a number of the ejection holes (9') formed on the bottom at equal interval in the length direction, one end being mounted by equal interval in the length direction of the cleaning air storage tank (61), and the other end being closed; and a number of cleaning air control valves (65), each comprising a control unit (62) positioned outside the cleaning air storage tank (61) and a valve unit (63) having one end connected to each control unit (62) and the other end connected to one end of each injection pipe (6), wherein a coupling of the annular air injection nozzle having two circular slits with the injection pipe (9) is through interposing a saddle connector (50) forming a connection opening (51) protruded its top and bottom so that each ejection hole 9' is operatively connected to each inlet hole (10') while the upper guide (10) of the injection nozzle contacts the injection pipe (9), and coupling by fixing clamps (70), each of which is in contact with the circumference of the injection pipe (9) and welded (F) at both sides of the upper guide (10) nearby both sides of the saddle connector (50).

[11] The filter cleaning system according to claim 10, wherein an upper part and a lower part of the connection opening (51) are formed to protrude so as to be same as the thickness of the bottom of the injection pipe (9) being connected to the upper guide (10) and the thickness of the top of the upper guide (10), respectively.

[12] The filter cleaning system according to claim 10, wherein the injection pipe (9) further comprises: a number of branch apertures (9a) formed at the bottom of the injection pipe (9), based on the center on the plane of the upper guide (10) of each injection nozzle as connected to improve the straightness of air flow into the dust collecting filter (7); or a number of branch tubes (9b) formed by being extended from each of the branch apertures (9a) downwardly.

[13] A filter cleaning system of a filter dust collector (100) by using the circular type air injection nozzle according to claim 4, comprising: a cleaning air storage tank (61) positioned outside of the filter dust collector 100; a number of the injection pipes (9) positioned on vertical tops of dust collecting filters (7) mounted in the filter dust collector (100), each injection pipe (9) having a number of the ejection holes (9') formed on a bottom side at equal interval in the length direction, one end being mounted by equal interval in the length direction of the cleaning air storage tank (61), and the other end being closed; and a number of cleaning air control valves (65), each comprising a control unit (62) positioned outside the cleaning air storage tank (61) and a valve unit (63) having one end connected to each control unit (62) and the other end connected to one end of each injection pipe (6), wherein a coupling of the upper guide (10) with the injection pipe (9) is made by using fixing clamps (70), each of which is in contact with the circumference of the injection pipe (9) and welded (F) at both sides of the upper guide (10) nearby the protruding inlet (31).

[14] The filter cleaning system according to claim 13, wherein the injection pipe (9) further comprises: a number of branch apertures (9a) formed at the bottom of the injection pipe (9), based on the center on the plane of the upper guide (10) of each injection nozzle as connected to improve the straightness of air flow into the dust collecting filter (7); or a number of branch tubes (9b) formed by being extended from each of the branch apertures (9a) downwardly.