Bag filter

Abstract

To suppress the generation of a dust bridge in a hopper.SOLUTION: A bag filter 1 includes: a casing 2; a hopper that is provided at a bottom portion of the casing 2, and in which a width in a width direction gradually decreases downward, and a lower end opening 33 provided at a lower end extends in a longitudinal direction; a filter cloth unit 4 that has, with a plurality of filter cloths 41 arranged along the width direction defined as filter cloth rows in the casing 2, a first filter cloth row group 430 in which a plurality of first filter cloth rows 43 are arranged in the longitudinal direction and a second filter cloth row group 440 in which a plurality of second filter cloth rows 44 are arranged in the longitudinal direction at a position adjacent to the first filter cloth row group in the width direction; a backwash unit 5 that has first and second backwash portions 53, 54 which respectively perform backwashing on the first and second filter cloth row groups in units of filter cloth row; and a control portion that determines backwash timing and causes the backwash unit 5 to perform, according to the backwash timing, backwashing on the first filter cloth row and the second filter cloth row whose positions in the longitudinal direction are different from each other.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a bag filter.

Background Art

[0002] Conventionally, in waste incineration facilities and the like, bag filters that collect dust contained in exhaust gas have been used. In a bag filter, backwashing is performed to remove the dust deposited on the filter cloth. For example, in the bag filter of Patent Document 1, a filter cloth group is divided into a plurality of compartments by partition plates, and an on-off damper that blocks the flow of exhaust gas is provided for each compartment. When the on-off damper of one compartment is closed, the dust deposited on the plurality of filter cloths in the compartment is sequentially removed by a pulse jet. In the bag filter of Patent Document 2, a method of sequentially blocking the gas flow of a plurality of compartments is disclosed by providing a movable shutter that can move horizontally above the pulse jet injection pipe.

[0003] In addition, in the bag type dust collector (bag filter) of Patent Document 3, after selecting and backwashing a filter (filter cloth) group in an arbitrary row, by sequentially selecting and backwashing a filter group in another row that is not adjacent to the filter group, uneven flow in the dust collector is prevented. In the backwashing device of Patent Document 4, information acquisition means for acquiring information regarding the ventilation resistance situation of the bag filter is provided, and every time backwashing is completed in one backwashing unit, it is determined whether backwashing is necessary based on the information from the information acquisition means. When it is determined that backwashing is necessary, backwashing of the next sequential backwashing unit is performed, and when it is determined that backwashing is unnecessary, backwashing is terminated.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a bag filter, a hopper is provided at the bottom of the casing. In an example of the hopper, the width in the width direction that is substantially perpendicular to the vertical direction gradually decreases downward, and the lower end opening provided at the lower end extends in the longitudinal direction that is substantially perpendicular to the vertical direction and the width direction. Further, a plurality of filter cloths arranged along the width direction are taken as a filter cloth row, and further, a plurality of filter cloth rows arranged in the longitudinal direction are taken as a filter cloth row group, and two filter cloth row groups may be provided in parallel. In such a bag filter, usually, in the two filter cloth row groups, backwashing is simultaneously performed on the filter cloth rows at the same position in the longitudinal direction. In this case, depending on the amount of dust to be removed, dust may form a bridge in the vicinity above the lower end opening of the hopper, that is, a dust bridge may occur. When a dust bridge occurs, dust cannot be properly discharged from the hopper.

[0006] The present invention has been made in view of the above problems, and an object thereof is to suppress the generation of a dust bridge in the hopper.

Means for Solving the Problems

[0007] Aspect 1 of the present invention is a bag filter, comprising: a casing through which exhaust gas flows from the bottom to the top; a hopper provided at the bottom of the casing, the width in the width direction that is substantially perpendicular to the vertical direction gradually decreasing downward, and the lower end opening provided at the lower end extending in the longitudinal direction that is substantially perpendicular to the vertical direction and the width direction; in the casing, a plurality of filter cloths arranged along the width direction are used as a filter cloth row, a first filter cloth row group in which a plurality of first filter cloth rows are arranged in the longitudinal direction, and a second filter cloth row group in which a plurality of second filter cloth rows are arranged in the longitudinal direction at a position adjacent to the first filter cloth row group in the width direction; a first backwashing unit that performs backwashing on the first filter cloth row group in units of filter cloth rows, and a second backwashing unit that performs backwashing on the second filter cloth row group in units of filter cloth rows; and a control unit that determines the backwashing timing and causes the backwashing unit to perform backwashing on the first filter cloth row and the second filter cloth row having different positions in the longitudinal direction according to the backwashing timing.

[0008] Aspect 2 of the present invention is the bag filter of Aspect 1, wherein in the first filter cloth row and the second filter cloth row, backwashing is performed while the exhaust gas is flowing.

[0009] Aspect 3 of the present invention is the bag filter of Aspect 1 (which may also be Aspect 1 or 2), wherein at the backwashing timing, the backwashing of the first filter cloth row and the backwashing of the second filter cloth row are performed simultaneously.

[0010] Aspect 4 of the present invention is the bag filter of Aspect 1 (which may be any one of Aspects 1 to 3), further comprising a dust conveying unit that is disposed below the lower end opening of the hopper and conveys dust in the longitudinal direction and discharges it to the outside.

[0011] Aspect 5 of the present invention is the bag filter of any one of Aspects 1 to 4, wherein the filter cloth unit is divided into a plurality of sections in the longitudinal direction, and the first filter cloth row and the second filter cloth row on which backwashing is performed at the backwashing timing belong to different sections.

[0012] Aspect 6 of the present invention is a bug filter according to any one of Aspects 1 to 4 (which may be any one of Aspects 1 to 5). When focusing on the longitudinal direction, between the first filter cloth row and the second filter cloth row where backwashing is performed at the backwashing timing, there is another filter cloth row present.

[0013] Aspect 7 of the present invention is a bug filter according to any one of Aspects 1 to 4 (which may be any one of Aspects 1 to 6). The longitudinal distance between the first filter cloth row and the second filter cloth row where backwashing is performed at the backwashing timing is greater than the width in the width direction at the lower end opening of the hopper.

[0014] Aspect 8 of the present invention is a bug filter according to any one of Aspects 1 to 4 (which may be any one of Aspects 1 to 7). Between the first filter cloth row where backwashing is performed at the backwashing timing and the first filter cloth row where backwashing is performed at the next backwashing timing, there is at least one first filter cloth row present. Between the second filter cloth row where backwashing is performed at the backwashing timing and the second filter cloth row where backwashing is performed at the next backwashing timing, there is at least one second filter cloth row present.

[0015] Aspect 9 of the present invention is a bug filter according to any one of Aspects 1 to 4 (which may be any one of Aspects 1 to 8). At the next backwashing timing after the backwashing timing, backwashing is performed on a first filter cloth row and a second filter cloth row different from the first filter cloth row and the second filter cloth row. The longitudinal positions of the first filter cloth row where backwashing is performed at the backwashing timing and the second filter cloth row where backwashing is performed at the next backwashing timing are different. The longitudinal positions of the second filter cloth row where backwashing is performed at the backwashing timing and the first filter cloth row where backwashing is performed at the next backwashing timing are different.

Advantages of the Invention

[0016] According to the present invention, the generation of dust bridges in the hopper can be suppressed.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0018] FIG. 1 and FIG. 2 are diagrams showing the configuration of a bag filter 1 according to an embodiment of the present invention. In FIGS. 1 and 2, the X direction, Y direction, and Z direction orthogonal to each other are indicated by arrows (the same applies to other figures). The X direction and Y direction are substantially horizontal directions, and the Z direction is substantially vertical (up and down) direction. In FIG. 1, a simplified cross-section of the bag filter 1 in a plane perpendicular to the X direction is shown, and in FIG. 2, a simplified cross-section of the bag filter 1 in a plane perpendicular to the Y direction is shown.

[0019] The bag filter 1 is also called a filtration type dust collector, and in a waste incineration facility or the like, it collects dust contained in exhaust gas (in addition to coal dust, it may include various chemicals mixed in the exhaust gas. The same applies hereinafter). The bag filter 1 includes a casing 2, a hopper 3, a filter cloth unit 4, a backwashing unit 5, a dust conveying unit 6, and a control unit 10. The control unit 10 is, for example, a computer equipped with a CPU or the like, and is responsible for overall control of the bag filter 1. The control unit of a waste incineration facility or the like may also serve as the control unit 10.

[0020] The casing 2 includes two side surfaces 21 facing the X direction and two side surfaces 22 facing the Y direction. The two side surfaces 21 are substantially parallel to each other and are arranged apart in the X direction. The two side surfaces 22 are substantially parallel to each other and are arranged apart in the Y direction. The two side surfaces 21 and the two side surfaces 22 form a dust collection space 20 where the filter cloth unit 4 is arranged. The dust collection space 20 also includes the internal space of the hopper 3. At the upper ends of the two side surfaces 21 and the two side surfaces 22, a top surface 23 is attached to close the upper part of the dust collection space 20. In this embodiment, the distance between the two side surfaces 22 is larger than the distance between the two side surfaces 21. That is, the length of the dust collection space 20 in the Y direction is larger than the width in the X direction. In the following description, the direction along the Y direction is referred to as the "longitudinal direction", and the direction along the X direction is referred to as the "width direction". The longitudinal direction and the width direction are substantially perpendicular to the vertical direction, and the longitudinal direction and the width direction are substantially perpendicular to each other. Note that the cross-sectional shape of the dust collection space 20 perpendicular to the vertical direction is not limited to a rectangle and may be other shapes.

[0021] A hopper 3 is provided at the bottom of the casing 2. The hopper 3 includes two side surfaces 31 facing the substantially X direction and two side surfaces 32 facing the substantially Y direction. The two side surfaces 31 are respectively connected to the lower ends of the two side surfaces 21 of the casing 2. The two side surfaces 32 are respectively connected to the lower ends of the two side surfaces 22 of the casing 2. The two side surfaces 31 are inclined surfaces located on the inner side in the width direction (toward the other side surface 31) as going downward. That is, the width of the hopper 3 in the width direction gradually decreases as going downward. The two side surfaces 32 are inclined surfaces located on the inner side in the longitudinal direction (toward the other side surface 32) as going downward. That is, the width of the hopper 3 in the longitudinal direction gradually decreases as going downward.

[0022] In the hopper 3, a substantially rectangular lower end opening 33 extending in the longitudinal direction is formed by the lower ends of the two side portions 31 and the lower ends of the two side portions 32. The lower end opening 33 is a discharge port provided at the lower end of the hopper 3. Below the dust collection space 20, except for the lower end opening 33, is blocked by the hopper 3. As will be described later, dust is shaken off from the filter cloth unit 4 onto the hopper 3. The dust is mainly guided by the two side portions 32 (inclined surfaces) extending in the longitudinal direction and is led to the lower end opening 33. In FIG. 2, the dust 81 shaken off from the filter cloth unit 4 and heading toward the lower end opening 33 is shown by a two-dot chain line.

[0023] The dust conveying unit 6 includes a screw feeder 61, a discharge pipe 62, and a rotary valve 63. The screw feeder 61 extends in the longitudinal direction and is disposed below the lower end opening 33 of the hopper 3. The dust that has fallen from the lower end opening 33 is conveyed in the (+Y) direction by the screw feeder 61. In the case (trough) of the screw feeder 61, the discharge pipe 62 is connected to the lower side of the end portion on the (+Y) side. The discharge pipe 62 extends in the vertical direction, and the dust conveyed to the end portion of the screw feeder 61 falls into the discharge pipe 62. A rotary valve 63 is provided in the discharge pipe 62, and the dust that has passed through the rotary valve 63 is discharged to the outside of the bag filter 1. In the bag filter 1, the rotary valve 63 prevents the inflow of gas (for example, outside air) into the dust collection space 20 and the outflow of gas in the dust collection space 20 to the outside. Note that the position of the discharge pipe 62 may be changed as appropriate. For example, the discharge pipe 62 may be disposed near the central portion of the hopper 3 in the longitudinal direction. In this case, a screw feeder for conveying dust from the end portion on the (+Y) side of the hopper 3 to the vicinity of the central portion and a screw feeder for conveying dust from the end portion on the (-Y) side of the hopper 3 to the vicinity of the central portion may be provided.

[0024] The upstream flue 71 is connected to the side surface portion 32 on the (-Y) side of the hopper 3. The downstream flue 72 is connected to the side surface portion 22 on the (+Y) side of the casing 2. In the upstream flue 71, the exhaust gas discharged from the incinerator flows. The exhaust gas flowing into the hopper 3 from the upstream flue 71 goes upward in the dust collection space 20 and is discharged outside the casing 2 from the downstream flue 72. In this way, in the casing 2, the exhaust gas flows from the lower part to the upper part. The downstream flue 72 is connected to the chimney via an induced draft fan or the like, and the exhaust gas that has passed through the bag filter 1 is discharged from the chimney to the outside air. Depending on the design of the bag filter 1, the upstream flue 71 may be connected to the casing 2.

[0025] FIG. 3 is a diagram showing the filter cloth unit 4 and the backwashing unit 5, and shows a state in which the top surface portion 23 is omitted and the casing 2 and its surroundings are viewed from the (+Z) side toward the (-Z) direction. As shown in FIGS. 1 to 3, a partition plate 26 that extends in a substantially horizontal direction is provided in the dust collection space 20 of the casing 2. A large number of holes 261 are arranged and formed in the partition plate 26. The filter cloth unit 4 includes a large number of filter cloths 41. The filter cloths 41 are respectively attached to the holes 261 of the partition plate 26. Specifically, each filter cloth 41 has a bottomed cylindrical shape, and the upper end is fixed around one hole 261. The filter cloth 41 is held by the partition plate 26 in a state of hanging from the partition plate 26. The dust collection space 20 is partitioned into an upper space 201 and a lower space 202 by the partition plate 26. The exhaust gas flowing into the lower space 202 from the upstream flue 71 (see FIG. 1) passes through one of the filter cloths 41, reaches the upper space 201, and is discharged to the downstream flue 72. Dust accumulates on the outer surface of the filter cloth 41, that is, the surface facing the lower space 202.

[0026] As shown in FIG. 3, in the filter cloth unit 4, a number of filter cloths 41 are arranged along the width direction and the longitudinal direction in accordance with the arrangement of a number of holes 261 in the partition plate 26. In the filter cloth unit 4 of FIG. 3, the filter cloth 41 arranged in the region on the (-X) side from the center in the width direction in the dust collection space 20 and the filter cloth 41 arranged in the region on the (+X) side are different in a reverse washing section described later used for reverse washing. In the following description, a plurality (for example, 5) of filter cloths 41 arranged along the width direction in the region on the (-X) side of the dust collection space 20 are called the first filter cloth row 43, and a plurality (for example, 5) of filter cloths 41 arranged along the width direction in the region on the (+X) side of the dust collection space 20 are called the second filter cloth row 44. The number of filter cloths 41 in each of the filter cloth rows 43 and 44 may be arbitrarily determined.

[0027] The filter cloth unit 4 has a first filter cloth row group 430 in which a plurality of first filter cloth rows 43 are arranged in the longitudinal direction, and a second filter cloth row group 440 in which a plurality of second filter cloth rows 44 are arranged in the longitudinal direction at a position adjacent to the first filter cloth row group 430 in the width direction. In the example of FIG. 3, the number of first filter cloth rows 43 included in the first filter cloth row group 430 is the same as the number of second filter cloth rows 44 included in the second filter cloth row group 440, and in the longitudinal direction, the plurality of first filter cloth rows 43 are arranged at the same positions as the plurality of second filter cloth rows 44 respectively.

[0028] In each of the first filter cloth rows 43 and the second filter cloth rows 44, the filter cloths 41 do not necessarily have to be arranged strictly in the width direction. Depending on the design of the bag filter 1, for example, the filter cloths 41 may be arranged in a staggered pattern along the width direction, or may be arranged slightly inclined with respect to the width direction. Also, in the longitudinal direction, the positions of the plurality of first filter cloth rows 43 may be slightly different from the positions of the plurality of second filter cloth rows 44. Usually, in each of the first filter cloth row group 430 and the second filter cloth row group 440, since the filter cloth rows 43, 44 are arranged relatively closely in the longitudinal direction, it is assumed that the position in the longitudinal direction of each first filter cloth row 43 and the second filter cloth row 44 whose longitudinal position is closest to the first filter cloth row 43 is substantially the same. In other words, the second filter cloth rows 44 other than the second filter cloth row 44 whose longitudinal position is substantially the same as that of a certain first filter cloth row 43 are considered to have different longitudinal positions from the first filter cloth row 43. The plurality of first filter cloth rows 43 do not necessarily have to be arranged at a constant pitch in the longitudinal direction, and for example, relatively large gaps may be provided partially. The same applies to the second filter cloth rows 44.

[0029] As shown in FIGS. 2 and 3, the backwashing unit 5 includes a first backwashing section 53 and a second backwashing section 54. Each of the first backwashing section 53 and the second backwashing section 54 includes a header tank 50, a plurality of blow tubes 51, and a plurality of pulse valves 52. The header tank 50 is disposed above the casing 2 and extends in the longitudinal direction over substantially the entire casing 2. The header tank 50 of the first backwashing section 53 is disposed on the (-X) side of the casing 2, and the header tank 50 of the second backwashing section 54 is disposed on the (+X) side of the casing 2. Each header tank 50 is connected to an air compressor (not shown), and compressed air (for example, 0.3 to 0.7 MPa) supplied from the air compressor is stored in the header tank 50. Compressed gas other than air may be stored in the header tank 50.

[0030] As shown in FIG. 2, each blow tube 51 is substantially L-shaped and has an injection portion 511 extending in the width direction and a connection portion 512 extending in the vertical direction. In the first backwashing section 53, the injection portions 511 of the plurality of blow tubes 51 are respectively arranged above the plurality of first filter cloth rows 43 in the dust collection space 20. Each injection portion 511 overlaps with a plurality (all) of the filter cloths 41 of the first filter cloth row 43 in the vertical direction and has a plurality of injection ports respectively facing the plurality of filter cloths 41. Each connection portion 512 in the first backwashing section 53 extends upward from the end portion on the (-X) side of the injection portion 511 and is connected to the header tank 50 of the first backwashing section 53 outside the casing 2. A pulse valve 52 is provided in the vicinity of the header tank 50 in the connection portion 512.

[0031] In the first backwashing section 53, the plurality of pulse valves 52 provided in the plurality of blow tubes 51 are normally in a closed state. By opening the pulse valve 52 of one blow tube 51, compressed air is instantaneously blown into the plurality of filter cloths 41 of the first filter cloth row 43 facing the blow tube 51. Thereby, backwashing is performed on the plurality of filter cloths 41 of the first filter cloth row 43, and the dust deposited on the plurality of filter cloths 41 is removed into the hopper 3. Thus, in the first backwashing section 53, backwashing is performed on the first filter cloth row group 430 in units of filter cloth rows.

[0032] In the second backwashing section 54, the injection portions 511 of the plurality of blow tubes 51 are respectively arranged above the plurality of second filter cloth rows 44 in the dust collection space 20. Each injection portion 511 overlaps with a plurality (all) of the filter cloths 41 of the second filter cloth row 44 in the vertical direction and has a plurality of injection ports respectively facing the plurality of filter cloths 41. Each connection portion 512 in the second backwashing section 54 extends upward from the end portion on the (+X) side of the injection portion 511 and is connected to the header tank 50 of the second backwashing section 54 outside the casing 2. A pulse valve 52 is provided in the vicinity of the header tank 50 in the connection portion 512.

[0033] In the second backwashing unit 54, the plurality of pulse valves 52 provided in the plurality of blow tubes 51 are normally in a closed state. By opening the pulse valve 52 of one blow tube 51, compressed air is instantaneously blown into the plurality of filter cloths 41 of the second filter cloth row 44 facing the blow tube 51. Thereby, backwashing is performed on the plurality of filter cloths 41 of the second filter cloth row 44, and the dust deposited on the plurality of filter cloths 41 is shaken off into the hopper 3. Thus, in the second backwashing unit 54, backwashing is performed on the second filter cloth row group 440 in units of filter cloth rows. In the bag filter 1, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 while the exhaust gas is flowing without stopping the flow of the exhaust gas in the first filter cloth row 43 and the second filter cloth row 44. Such a backwashing process is also called an online pulse, and it is possible to perform backwashing while approximately maintaining the processing amount of the exhaust gas in the bag filter 1.

[0034] As will be described later, the backwashing of the first filter cloth row 43 and the second filter cloth row 44 is performed according to the backwashing timing determined by the control unit 10 in FIG. 1. In this processing example, in each of the first filter cloth row group 430 and the second filter cloth row group 440, the number of filter cloth rows to be backwashed according to one backwashing timing is one, but depending on the design of the bag filter 1, it may be two or more. The "backwashing in units of filter cloth rows" by the first backwashing unit 53 and the second backwashing unit 54 means that the minimum unit of backwashing is a filter cloth row, and backwashing is simultaneously performed on all the filter cloths 41 included in one filter cloth row, and it does not necessarily mean that backwashing is performed on only one filter cloth row.

[0035] Next, the backwashing operation in the bag filter 1 will be described. FIG. 4 is a diagram showing the order (hereinafter referred to as "backwashing order") of performing backwashing on the filter cloth rows 43 and 44 in each of the first filter cloth row group 430 and the second filter cloth row group 440. In FIG. 4, the backwashing order in the first filter cloth row group 430 is written on the left side of the plurality of first filter cloth rows 43, and the backwashing order in the second filter cloth row group 440 is written on the right side of the plurality of second filter cloth rows 44 (the same applies to FIGS. 5 and 6 described later).

[0036] In the control unit 10, a signal indicating that backwashing should be performed in the backwashing unit 5 (hereinafter referred to as the "backwashing timing signal") is generated, and the backwashing timing is determined. In the present embodiment, the differential pressure between the upper space 201 and the lower space 202 in the casing 2 is measured by a pressure gauge (not shown). When the measured value of the differential pressure is less than a predetermined value, a backwashing timing signal indicating the backwashing timing is sequentially generated at a first set period (for example, a period of several tens of minutes). When the measured value of the differential pressure is equal to or greater than the predetermined value, a backwashing timing signal is sequentially generated at a second set period shorter than the first set period (for example, a period of several minutes). The backwashing timing signal may be generated based on other conditions.

[0037] When one backwashing timing signal is generated, the control unit 10 controls the backwashing unit 5 to perform backwashing on one first filter cloth row 43 and one second filter cloth row 44 almost simultaneously. For example, by opening the pulse valve 52 of the blow tube 51 facing the first filter cloth row 43 whose backwashing order number in the first filter cloth row group 430 is "1", backwashing is performed on the first filter cloth row 43. Thereby, the dust deposited on the plurality of filter cloths 41 of the first filter cloth row 43 is removed and falls into the hopper 3. Further, by opening the pulse valve 52 of the blow tube 51 facing the second filter cloth row 44 whose backwashing order number in the second filter cloth row group 440 is "1", backwashing is performed on the second filter cloth row 44. Thereby, the dust deposited on the plurality of filter cloths 41 of the second filter cloth row 44 is removed and falls into the hopper 3.

[0038] When the next backwash timing signal of the above-described backwash timing signal is generated, the backwash of the first filter cloth row 43 in the first filter cloth row group 430 with the backwash order number of "2" and the backwash of the second filter cloth row 44 in the second filter cloth row group 440 with the backwash order number of "2" are performed almost simultaneously. Thus, every time the backwash timing signal is generated, the first backwash unit 53 performs backwashing on one first filter cloth row 43 according to the backwash order in the first filter cloth row group 430, and the second backwash unit 54 performs backwashing on one second filter cloth row 44 according to the backwash order in the second filter cloth row group 440. In the backwash order of each of the first filter cloth row group 430 and the second filter cloth row group 440, only one number is assigned to each filter cloth row 43, 44. Therefore, after the first filter cloth row 43 and the second filter cloth row 44 are backwashed at each backwash timing, at the next backwash timing after that backwash timing, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 that are different from the first filter cloth row 43 and the second filter cloth row 44.

[0039] Here, if a combination of the first filter cloth row 43 and the second filter cloth row 44 arranged at the same position in the longitudinal direction is called a filter cloth row pair, in all the filter cloth row pairs, the backwash order number of the first filter cloth row 43 is different from the backwash order number of the second filter cloth row 44. In other words, according to each backwash timing, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 with different longitudinal positions. As a result, the falling position of the dust removed from the first filter cloth row 43 is different from the falling position of the dust removed from the second filter cloth row 44 in the longitudinal direction. Therefore, it is possible to prevent the dust from the first filter cloth row group 430 and the dust from the second filter cloth row group 440 from falling at the same position in the hopper 3 in the longitudinal direction and causing a dust bridge at one backwash timing.

[0040] Also, in all pairs of filter cloth rows, the reverse washing sequence numbers of the first filter cloth row 43 and the reverse washing sequence numbers of the second filter cloth row 44 are not consecutive. Therefore, when reverse washing is performed on one of the filter cloth rows 43, 44 of the filter cloth row pair at a certain reverse washing timing, reverse washing will not be performed on the other filter cloth row 43, 44 of the filter cloth row pair at the next reverse washing timing after that reverse washing timing. In other words, dust will not fall at the same position in the hopper 3 in the longitudinal direction at two consecutive reverse washing timings.

[0041] Furthermore, in the first filter cloth row group 430, the reverse washing sequence numbers in each combination of two first filter cloth rows 43 adjacent to each other in the longitudinal direction are not consecutive. In other words, the first filter cloth row 43 on which reverse washing is performed at each reverse washing timing and the first filter cloth row 43 on which reverse washing is performed at the next reverse washing timing after that reverse washing timing are not adjacent to each other in the longitudinal direction. Similarly, in the second filter cloth row group 440, the reverse washing sequence numbers in each combination of two second filter cloth rows 44 adjacent to each other in the longitudinal direction are not consecutive. In other words, the second filter cloth row 44 on which reverse washing is performed at each reverse washing timing and the second filter cloth row 44 on which reverse washing is performed at the next reverse washing timing after that reverse washing timing are not consecutive in the longitudinal direction.

[0042] Here, the reverse washing operation in the bag filter of the comparative example will be described. FIG. 5 is a diagram showing the reverse washing sequence in each of the first filter cloth row group 930 and the second filter cloth row group 940 of the bag filter 9 of the comparative example, corresponding to FIG. 4. In the bag filter 9 of the comparative example, in all pairs of filter cloth rows, the reverse washing sequence numbers of the first filter cloth row 93 and the reverse washing sequence numbers of the second filter cloth row 94 are the same. In other words, according to each reverse washing timing, reverse washing is performed on the first filter cloth row 93 and the second filter cloth row 94 having the same position in the longitudinal direction, and dust is shaken off from the first filter cloth row 93 and the second filter cloth row 94 at the same position in the longitudinal direction in the hopper. In this case, a large amount of dust accumulates at the lower end opening of the hopper, and a dust bridge is likely to occur.

[0043] In addition, in the bug filter 9 of the comparative example, in the first filter cloth row group 930, the reverse washing order numbers in each combination of two adjacent first filter cloth rows 93 in the longitudinal direction are consecutive. In other words, the first filter cloth row 93 where reverse washing is performed at each reverse washing timing and the first filter cloth row 93 where reverse washing is performed at the next reverse washing timing after the reverse washing timing are adjacent in the longitudinal direction. As a result, most of the dust removed from the first filter cloth row 93 where reverse washing is performed at the next reverse washing timing is sucked by the first filter cloth row 93 whose suction force has increased due to the reverse washing at the immediately preceding reverse washing timing, and the amount of dust removed by the reverse washing in the first filter cloth row group 930 decreases. The same applies to the second filter cloth row group 940.

[0044] On the other hand, in the bug filter 1 of FIG. 4, the control unit 10 causes the reverse washing unit 5 to perform reverse washing on the first filter cloth row 43 and the second filter cloth row 44 having different longitudinal positions according to each reverse washing timing. Thereby, it is possible to prevent dust from being removed from the first filter cloth row 43 and the second filter cloth row 44 at the same position in the longitudinal direction in the hopper 3. In other words, the amount of dust removed at each position in the hopper 3 in the longitudinal direction is limited at each reverse washing timing. As a result, it is possible to suppress the generation of a dust bridge that crosses the lower end opening 33 in the hopper 3.

[0045] Preferably, there is at least one first filter cloth row 43 between the first filter cloth row 43 where backwashing is performed at each backwashing timing and the first filter cloth row 43 where backwashing is performed at the next backwashing timing after the current backwashing timing. Also, there is at least one second filter cloth row 44 between the second filter cloth row 44 where backwashing is performed at the current backwashing timing and the second filter cloth row 44 where backwashing is performed at the next backwashing timing. As a result, in the first filter cloth row group 430, it is possible to suppress that most of the dust removed from the first filter cloth row 43 where backwashing is performed at the next backwashing timing is attracted by the first filter cloth row 43 whose suction force has increased due to the backwashing at the immediately preceding backwashing timing. The same applies to the second filter cloth row group 440. As a result, dust can be efficiently removed from the filter cloth unit 4.

[0046] Preferably, the longitudinal positions of the first filter cloth row 43 where backwashing is performed at each backwashing timing and the second filter cloth row 44 where backwashing is performed at the next backwashing timing after the current backwashing timing are different. Also, the longitudinal positions of the second filter cloth row 44 where backwashing is performed at the current backwashing timing and the first filter cloth row 43 where backwashing is performed at the next backwashing timing are different. Therefore, even if dust from one of the filter cloth rows 43, 44 of the filter cloth row pair at one backwashing timing remains in the hopper 3 until the next backwashing timing, at the next backwashing timing, it is possible to prevent the dust from being removed from the other filter cloth row 43, 44 of the filter cloth row pair, and it is possible to suppress the generation of a dust bridge.

[0047] Note that depending on the cycle of the backwashing timing, etc., backwashing may be performed on two adjacent first filter cloth rows 43 (or two second filter cloth rows 44) in the longitudinal direction at two consecutive backwashing timings. Similarly, at two consecutive backwashing timings, backwashing may be performed on one of the filter cloth rows 43, 44 and the other filter cloth row 43, 44 of the filter cloth row pair, respectively.

[0048] FIG. 6 is a diagram showing another example of the backwashing order. In this processing example, the filter cloth unit 4 is divided into a plurality of sections (or groups) in the longitudinal direction. In the example of FIG. 6, as shown by the dashed rectangle, it is divided into three sections P1 to P3. At each backwashing timing, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 belonging to different sections P1 to P3 from each other.

[0049] Specifically, at one backwashing timing, backwashing is performed on the first filter cloth row 43 whose backwashing order number in the first filter cloth row group 430 is "1", and backwashing is performed on the second filter cloth row 44 whose backwashing order number in the second filter cloth row group 440 is "1". That is, backwashing is performed on the first filter cloth row 43 belonging to section P1 and the second filter cloth row 44 belonging to section P2 almost simultaneously. At the next backwashing timing after the above backwashing timing, backwashing is performed on the first filter cloth row 43 whose backwashing order number in the first filter cloth row group 430 is "2", and backwashing is performed on the second filter cloth row 44 whose backwashing order number in the second filter cloth row group 440 is "2". That is, backwashing is performed on the first filter cloth row 43 belonging to section P2 and the second filter cloth row 44 belonging to section P3 almost simultaneously.

[0050] In this way, the first filter cloth row 43 and the second filter cloth row 44 for each number in the backwashing order belong to different sections P1 to P3 from each other. In other words, the first filter cloth row 43 and the second filter cloth row 44 on which backwashing is performed at each backwashing timing belong to different sections P1 to P3 from each other. Thereby, the generation of dust bridges in the hopper 3 can be suppressed. The number of the first filter cloth rows 43 in the first filter cloth row group 430 included in each section is, for example, 2 or more, and preferably 3 or more. The upper limit of the number is, for example, half of the number of rows included in the first filter cloth row group 430. The same applies to the second filter cloth row group 440.

[0051] Here, assume a case where backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 that are adjacent to each other in the diagonal direction at one backwashing timing. The first filter cloth row 43 and the second filter cloth row 44 adjacent to the second filter cloth row 44 that forms a filter cloth row pair with the first filter cloth row 43 are adjacent to each other in the diagonal direction (for example, refer to the first filter cloth row 43 and the second filter cloth row 44 whose backwashing order number is "2" in the example of FIG. 4 above). In this case, when the interval between the filter cloth rows 43 and 44 in the longitudinal direction is small, dust is knocked off from the first filter cloth row 43 and the second filter cloth row 44 that are adjacent to each other in the diagonal direction to a position close in the longitudinal direction in the hopper 3, and there is a possibility of generating a dust bridge.

[0052] On the other hand, in the example of FIG. 6, when focusing on the longitudinal direction, there are other filter cloth rows 43 and 44 between the first filter cloth row 43 and the second filter cloth row 44 on which backwashing is performed at each backwashing timing. In other words, the first filter cloth row 43 and the second filter cloth row 44 on which backwashing is performed at each backwashing timing are not adjacent to each other in the diagonal direction. Thereby, even when the interval between the filter cloth rows 43 and 44 in the longitudinal direction is small, the generation of a dust bridge in the hopper 3 can be suppressed. Further, from the viewpoint of sufficiently separating the first filter cloth row 43 and the second filter cloth row 44 on which backwashing is performed at the same backwashing timing to more reliably suppress the generation of a dust bridge, the longitudinal distance between the first filter cloth row 43 and the second filter cloth row 44 is preferably larger than, for example, the width in the width direction at the lower end opening 33 of the hopper 3. The same applies to the case where backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44 having different longitudinal positions at each backwashing timing without providing the partitions P1 to P3.

[0053] Various modifications are possible for the bag filter 1 described above.

[0054] In the above-described embodiment, since the backwashing of the first filter cloth row 43 and the backwashing of the second filter cloth row 44 are performed simultaneously at each backwashing timing, the control related to backwashing is simplified, and it is possible to rapidly reduce the differential pressure when the differential pressure is high. On the other hand, depending on the structure of the bag filter 1, such as the first backwashing section 53 and the second backwashing section 54 sharing one header tank 50, the backwashing of the first filter cloth row 43 and the backwashing of the second filter cloth row 44 may be performed with a time difference. The control unit 10 may cause the backwashing unit 5 to perform backwashing on the first filter cloth row 43 and the second filter cloth row 44 that should be backwashed at one backwashing timing, between the backwashing timing and the next backwashing timing. Even when a time difference is provided between the backwashing of the first filter cloth row 43 and the backwashing of the second filter cloth row 44, if dust removed by backwashing for one of the filter cloth row pairs remains in the hopper and backwashing is performed on the other, the dust accumulates and a dust bridge is likely to occur. Therefore, even when the above time difference is provided, it is important to perform backwashing on the first filter cloth row 43 and the second filter cloth row 44 whose longitudinal positions are different from each other according to each backwashing timing.

[0055] As described above, the number of rows of the first filter cloth row 43 that is backwashed at one backwashing timing may be 2 or more, and the number of rows of the second filter cloth row 44 may also be 2 or more. Even in this case, the two or more first filter cloth rows 43 and the two or more second filter cloth rows 44 have different longitudinal positions from each other.

[0056] In the bag filter 1 of FIGS. 1 and 2, a dust conveying section 6 is arranged below the lower end opening 33 of the hopper 3, and the dust conveying section 6 conveys dust in the longitudinal direction and discharges it to the outside. With such a configuration, the dust removed from the first filter cloth row 43 and the second filter cloth row 44 cannot be discharged promptly, and a dust bridge is likely to occur. Therefore, the present method of performing backwashing on the first filter cloth row 43 and the second filter cloth row 44, whose longitudinal positions are different from each other according to each backwashing timing, can be said to be particularly suitable for the bag filter 1 having such a configuration. Of course, the present method may be adopted in a bag filter 1 in which the dust conveying section 6 is not provided and the dust is moved downward from the lower end opening 33 of the hopper 3, for example.

[0057] In the bag filter 1, as shown in FIG. 7, two hoppers 3 may be provided at the bottom of the casing 2. Above each of the two hoppers 3, a first filter cloth row group 430 and a second filter cloth row group 440 are arranged. In the first filter cloth row group 430 and the second filter cloth row group 440 above one hopper 3, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44, whose longitudinal positions are different from each other according to each backwashing timing. Similarly, in the first filter cloth row group 430 and the second filter cloth row group 440 above the other hopper 3, backwashing is performed on the first filter cloth row 43 and the second filter cloth row 44, whose longitudinal positions are different from each other according to each backwashing timing. Thereby, the generation of a dust bridge in the hopper 3 is suppressed.

[0058] The bag filter 1 may be used in addition to waste incineration facilities.

[0059] The configurations in the above-described embodiments and each modification may be appropriately combined as long as they do not conflict with each other.

Explanation of Signs

[0060] 1 Bag filter 2 Casing 3 Hopper 4 Filter cloth unit 5 Backwashing unit 6 Dust conveying section 10 Control Unit 33 Lower End Opening 41 Filter Cloth 43 First Filter Cloth Row 44 Second Filter Cloth Row 53 First Backwashing Unit 54 Second Backwashing Unit 430 First Filter Cloth Row Group 440 Second Filter Cloth Row Group Zones P1 to P3

Claims

1. A bag filter, comprising: a casing through which exhaust gas flows from the bottom to the top; a hopper provided at the bottom of the casing, having a width in the width direction that is substantially perpendicular to the vertical direction and gradually decreases downward, and a lower end opening provided at the lower end extending in the longitudinal direction that is substantially perpendicular to the vertical direction and the width direction; in the casing, a plurality of filter cloths arranged along the width direction are used as a filter cloth row, a first filter cloth row group in which a plurality of first filter cloth rows are arranged in the longitudinal direction, and a second filter cloth row group in which a plurality of second filter cloth rows are arranged in the longitudinal direction at a position adjacent to the first filter cloth row group in the width direction; a backwashing unit having a first backwashing part for performing backwashing on the first filter cloth row group in units of filter cloth rows and a second backwashing part for performing backwashing on the second filter cloth row group in units of filter cloth rows; a control unit that determines the backwashing timing and causes the backwashing unit to perform backwashing on the first filter cloth row and the second filter cloth row having different positions in the longitudinal direction according to the backwashing timing; A bag filter comprising the above.

2. The bag filter according to Claim 1, wherein in the first filter cloth row and the second filter cloth row, backwashing is performed in a state where the exhaust gas flows.

3. The bag filter according to Claim 1, wherein at the backwashing timing, backwashing of the first filter cloth row and backwashing of the second filter cloth row are performed simultaneously.

4. The bag filter according to Claim 1, further comprising a dust conveying part disposed below the lower end opening of the hopper for conveying dust in the longitudinal direction and discharging it to the outside.

5. The bag filter according to any one of Claims 1 to 4, wherein the filter cloth unit is divided into a plurality of sections in the longitudinal direction, and the first filter cloth row and the second filter cloth row on which backwashing is performed at the backwashing timing belong to different sections.

6. The bag filter according to any one of Claims 1 to 4, wherein when focusing on the longitudinal direction, there are other filter cloth rows between the first filter cloth row and the second filter cloth row on which backwashing is performed at the backwashing timing.

7. The bag filter according to any one of Claims 1 to 4, A bag filter in which the longitudinal distance between the first filter cloth row and the second filter cloth row where backwashing is performed at the backwashing timing is larger than the width in the width direction at the lower end opening of the hopper.

8. The bag filter according to any one of Claims 1 to 4, wherein at least one first filter cloth row exists between the first filter cloth row where backwashing is performed at the backwashing timing and the first filter cloth row where backwashing is performed at the next backwashing timing, and at least one second filter cloth row exists between the second filter cloth row where backwashing is performed at the backwashing timing and the second filter cloth row where backwashing is performed at the next backwashing timing.

9. The bag filter according to any one of Claims 1 to 4, wherein backwashing is performed on a first filter cloth row and a second filter cloth row different from the first filter cloth row and the second filter cloth row at the next backwashing timing after the backwashing timing, wherein the longitudinal positions of the first filter cloth row where backwashing is performed at the backwashing timing and the second filter cloth row where backwashing is performed at the next backwashing timing are different, and the longitudinal positions of the second filter cloth row where backwashing is performed at the backwashing timing and the first filter cloth row where backwashing is performed at the next backwashing timing are different.

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