1. A method for converting an electrostatic precipitator in which a fixed electrode type electrostatic precipitator is arranged in a casing, comprising: replacing the fixed electrode type electrostatic precipitator with a moving dust collecting electrode and a discharge electrode corresponding to the moving dust collecting electrode.

2. The method for converting the electrostatic precipitator according to Claim 1, wherein the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of an exhaust gas passage inside the casing, the method further comprising: removing some or all of the stages of the fixed electrostatic precipitator and then mounting the moving dust collecting electrode and the discharge electrode at a position from which the fixed electrode type electrostatic precipitator has been removed.

3. The method for converting the electrostatic precipitator according to Claim 1, further comprising: forming a lower opening by removing a hopper from a position facing the fixed electrode type electrostatic precipitator at a lower end of the casing; arranging a hoist at a position facing the lower opening in the casing; and hoisting the moving dust collecting electrode and the discharge electrode with the hoist and carrying in the moving dust collecting electrode and the discharge electrode through the lower opening.

4. The method for converting the electrostatic precipitator according to Claim 3, further comprising: arranging an upper unit at a position between the hoist and the lower opening, the upper unit including a housing that has an insertion slot communicating with the lower opening and a plurality of upper rollers that are aligned in a direction perpendicular to the direction of the exhaust gas passage inside the casing, are supported in the insertion slot, and support the moving dust collecting electrode at an upper end thereof; and hoisting a lower unit with a wire fed from the hoist and inserted into the insertion slot, and carrying in the lower unit through the lower opening, the lower unit including a plurality of lower rollers that are aligned to face the upper rollers and support the moving dust collecting electrode at a lower end thereof.

5. The method for converting the electrostatic precipitator according to Claim 3, further comprising: hoisting the hopper with the hoist, and sealing the lower opening.

6. The method for converting the electrostatic precipitator according to Claim 4, wherein a rail that extends in a direction perpendicular to the exhaust gas passage across the casing is arranged on the upper unit at a position facing the insertion slot, the method further comprising: hoisting the moving dust collecting electrode with the hoist arranged on the rail so as to be movable along the rail; and repeating an operation of moving the hoist and hoisting another moving dust collecting electrode, thereby aligning a plurality of moving dust collecting electrodes in the direction perpendicular to the exhaust gas passage.

7. The method for converting the electrostatic precipitator according to Claim 1, further comprising: forming an upper opening in an upper end of the casing at a position facing the fixed electrode type electrostatic precipitator; carrying in a lower unit through the upper opening, and arranging the lower unit in the casing, the lower unit including a plurality of lower rollers that are aligned in a direction perpendicular to the exhaust gas passage inside the casing and support the moving dust collecting electrode at a lower end thereof; and arranging an upper unit on the casing at a position facing the upper opening, the upper unit including a plurality of upper rollers that are aligned and supported to face the lower rollers and support the moving dust collecting electrode at an upper end thereof.

8. The method for converting the electrostatic precipitator according to Claim 7, wherein the upper unit has an insertion slot communicating with the upper opening, and the upper rollers are supported inside the insertion slot, the method further comprising: carrying in the moving dust collecting electrode into the insertion slot.

9. The method for converting the electrostatic precipitator according to Claim 1, further comprising: arranging an extended casing on the casing at a position facing the upper opening such that the upper end of the casing is heightened.

10. The method for converting the electrostatic precipitator according to Claim 1, wherein a guide plate is arranged such that exhaust gas that reaches a zone in an exhaust gas passage that is lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

11. An electrostatic precipitator comprising: a casing through which exhaust gas flows; a fixed electrode type electrostatic precipitator arranged upstream of an exhaust gas passage in the casing; a moving dust collecting electrode that is arranged downstream of the exhaust gas passage, and that includes a plurality of dust collecting electrodes that are coupled together to form a loop as a whole and circle around; a discharge electrode arranged at a position facing the moving dust collecting electrode; and a guide plate arranged such that the exhaust gas that reaches a zone in an exhaust gas passage lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

12. The electrostatic precipitator according to Claim 11, wherein a plurality of moving dust collecting electrodes are aligned in a direction perpendicular to the exhaust gas passage, lower rollers that support a lower end of each moving dust collecting electrode are supported by the lower unit, and the guide plate is arranged on the lower unit.

13. The electrostatic precipitator according to Claim 11, wherein an exhaust gas diffusing unit is arranged between the fixed electrode type electrostatic precipitator and the moving dust collecting electrode.

14. The electrostatic precipitator according to Claim 11, wherein the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing, and the moving dust collecting electrode is arranged at a position from which some or all of the stages of the fixed electrode type electrostatic precipitator have been removed.

15. The electrostatic precipitator according to Claim 11, wherein the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing, a width of the moving dust collecting electrode is greater than a width of the fixed electrode type electrostatic precipitator, and the moving dust collecting electrode is arranged at a position from which at least two adjacent stages of the fixed electrode type electrostatic precipitator have been removed.

16. The electrostatic precipitator according to Claim 15, wherein diffusion space is formed between the moving dust collecting electrode and the fixed electrode type electrostatic precipitator to diffuse the exhaust gas, and an exhaust gas diffusing unit is arranged in the diffusion space.

17. The electrostatic precipitator according to Claim 11, wherein an upper opening is formed at a position facing the moving dust collecting electrode in an upper end of the casing, and an extended casing is arranged on the casing at a position facing the upper opening so that the upper end of the casing is heightened.

TECHNICAL FIELD
[0001] The present invention relates to an electrostatic precipitator. The present invention more particularly relates to a method for converting part or all of a fixed electrode type electrostatic precipitator to a moving electrode type electrostatic precipitator.

BACKGROUND ART
[0002] As soot and dust emission control is strengthened and also as existing electrostatic precipitators are aging; more conversion and renovation work is required to enhance the performance of the electrostatic precipitators.

To enhance the performance of fixed electrode type electrostatic precipitators, which collect soot and dust with fixed dust collecting electrodes, addition of more precipitators is a common approach; however, most of the existing facilities cannot afford sufficient surrounding space for such addition.

[0003] In contrast, moving electrode type electrostatic precipitators, which collect soot and dust with moving dust collecting electrodes, remove easily with brushes soot and dust that are adhered to the moving dust collecting electrodes. The moving dust collecting electrodes thereby can be kept clean, maintaining high dust collection performance. For this reason, to enhance the performance of part or all of the existing fixed electrode type electrostatic precipitator, replacing them with a moving electrode type electrostatic precipitator is an effective solution.

[0004] Among the conventional techniques of renewing a fixed electrode type electrostatic precipitator, for example, in the method disclosed in Patent Document 1, fixed dust collecting electrodes are carried in and out through an opening that is formed in an upper side surface of a casing of the fixed electrode type electrostatic precipitator. In the method disclosed in Patent Document 2, on the other hand, fixed dust collecting electrodes are carried in and out through an opening that is formed by removing a hopper from a lower end of a casing that houses the fixed electrode type electrostatic precipitator.

[0005] Meanwhile, among the conventional techniques of installing or renewing a moving electrode type electrostatic precipitator, a method of carrying in and mounting a discharge electrode through an opening that is formed by removing a hopper from a lower end of a casing with a gate type mobile crane, which is set up above the casing, and then carrying in and mounting a moving dust collecting electrode through the opening is disclosed in Patent Document 3. On the other hand, in the method disclosed in Patent Document 4, driving wheels that drive a moving dust collecting electrode are coupled to endless chains that are included in the moving dust collecting electrode. Dust collecting electrodes included in the moving dust collecting electrode are sequentially coupled one by-one to the endless chains near the driving wheels. In the method disclosed in Patent Document 5, an endless chain is cut at one point, and an end of new chain is connected to one of the cut ends of the endless chain. While turning the endless chain around, the dust collecting electrode plates coupled to this endless chain are sequentially re-coupled to the new chain. When the new chain makes one circuit, the endless chain from which all the dust collecting electrode plates are detached is removed. Thereafter, one end of the new chain is connected to the other end to complete replacement of the endless chain of the moving dust collecting electrode with the new chain.

[0006] A structure in which a fixed electrode type electrostatic precipitator and a moving electrode type electrostatic precipitator are arranged in one casing is disclosed in Patent Document 6. More particularly, the fixed electrode type electrostatic precipitator is arranged upstream of an exhaust gas passage in the casing, while the moving electrode type electrostatic precipitator is arranged downstream of the exhaust gas passage. By this arrangement, soot and dust having larger particle size are caught by the earlier fixed electrode type electrostatic precipitator, while soot and dust having smaller particle size, which are difficult for the fixed electrode type electrostatic precipitator to catch, are caught by the latter moving electrode type electrostatic precipitator. This means that, after the renovation, the structure as disclosed in Patent Document 6 is preferable for the fixed electrode type electrostatic precipitator. Conventional Art Documents Patent Documents

[0007]
Patent Document 1: Japanese Patent Application Laid-open No. H7-96214
Patent Document 2: Japanese Patent Application Laid-open No. H9-290177
Patent Document 3: Japanese Patent Application Laid-open No. 2000-342993
Patent Document 4: Japanese Patent Application Laid-open No. 2000-342996
Patent Document 5: Japanese Patent Application Laid-open No. 2000-342995
Patent Document 6: Japanese Patent Application Laid-open No. S57-32742

DISCLOSURE OF INVENTION PROBLEM TO BE SOLVED BY THE INVENTION
[0008] In the structure disclosed in Patent Document 6, the casing is originally designed to suitably house the fixed electrode type electrostatic precipitator and the moving electrode type electrostatic precipitator. However, the fixed electrode type electrostatic precipitator and the moving electrode type electrostatic precipitator have different dimensions (heights), and different zones for effectively catching soot and dust from the exhaust gas also appear at different heights between the two precipitators. Consequently, to realize the structure disclosed in Patent Document 6 in a conventional fixed electrode type electrostatic precipitation technique, the casing needs to be redesigned to make room for installing a moving electrode type electrostatic precipitator, which raises cost problems.

[0009] In light of the above problems, it is an object of the present invention to provide a method for converting an electrostatic precipitator by replacing part or all of a fixed electrode type electrostatic precipitator with a moving electrode type electrostatic precipitator without making any change in an existing casing, and also an electrostatic precipitator produced by such a method.

MEANS FOR SOLVING THE PROBLEM
[0010] In order to achieve the above object, a method for converting an electrostatic precipitator according to an aspect of the present invention, in which a fixed electrode type electrostatic precipitator is arranged in a casing, includes replacing the fixed electrode type electrostatic precipitator with a moving dust collecting electrode and a discharge electrode corresponding to the moving dust collecting electrode.

[0011] With the above method, the casing need not be newly designed. The existing fixed electrode type electrostatic precipitator can be replaced with the moving electrode type electrostatic precipitator including the moving dust collecting electrode and the discharge electrode by using the existing casing. Accordingly, the exhaust gas processing capacity can be thereby increased.

[0012] According to another aspect of the present invention, the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of an exhaust gas passage inside the casing. The method further includes removing some or all of the stages of the fixed electrostatic precipitator and then mounting the moving dust collecting electrode and the discharge electrode at a position from which the fixed electrode type electrostatic precipitator has been removed.

[0013] With the above method, how much the electrostatic precipitator is to be converted can be determined in accordance with the number of stages of the fixed electrode type electrostatic precipitator that are to be removed or the dimensions of the moving dust collecting electrode.
The method according to still another aspect of the present invention further includes forming a lower opening by removing a hopper from a position facing the fixed electrode type electrostatic precipitator at a lower end of the casing; arranging a hoist at a position facing the lower opening in the casing; and hoisting the moving dust collecting electrode and the discharge electrode with the hoist and carrying in the moving dust collecting electrode and the discharge electrode through the lower opening. [0014] With the above method, the moving dust collecting electrode and the discharge electrode need not be hoisted over the casing, and therefore can be efficiently carried into the casing. The discharge electrode and the moving dust collecting electrode are hoisted by the hoist that is supported by the casing, and therefore the moving electrode type electrostatic precipitator can be efficiently carried in even if sufficient work space is difficult to obtain in the existing fixed electrode type electrostatic precipitator.

[0015] The method according to still another aspect of the present invention further includes arranging an upper unit at a position between the hoist and the lower opening; and hoisting a lower unit with a wire fed from the hoist and inserted into the insertion slot and carrying in the lower unit through the lower opening. The upper unit includes a housing that has an insertion slot communicating with the lower opening and a plurality of upper rollers that are aligned in a direction perpendicular to the direction of the exhaust gas passage inside the casing, are supported in the insertion slot, and support the moving dust collecting electrode at an upper end thereof. The lower unit includes a plurality of lower rollers that are aligned to face the upper rollers and support the moving dust collecting electrode at a lower end thereof.

[0016] With the above method, the installation position need not be determined on site for each moving dust collecting electrode. Multiple moving dust collecting electrodes can be easily mounted without causing any interference between the hoist and the upper unit.

[0017] The method according to still another aspect of the present invention includes hoisting the hopper with the hoist, and sealing the lower opening.

With the above method, the hopper can be easily hoisted, and the lower opening can be easily sealed.

[0018] The method according to still another aspect of the present invention, in which a rail that extends in a direction perpendicular to the exhaust gas passage across the casing is arranged on the upper unit at a position facing the insertion slot, further includes hoisting the moving dust collecting electrode with the hoist arranged on the rail so as to be movable along the rail; and repeating an operation of moving the hoist and hoisting another moving dust collecting electrode, thereby aligning a plurality of moving dust collecting electrodes in the direction perpendicular to the exhaust gas passage.

[0019] With the above method, in the existing fixed electrode type electrostatic precipitator in which sufficient work space is difficult to obtain, the discharge electrode can be efficiently carried in, and also the multiple moving dust collecting electrodes can be efficiently carried in.

[0020] The method according to still another aspect of the present invention further includes forming an upper opening in an upper end of the casing at a position facing the fixed electrode type electrostatic precipitator; and carrying in a lower unit through the upper opening and arranging the lower unit in the casing; and arranging an upper unit on the casing at a position facing the upper opening. The lower unit includes a plurality of lower rollers that are aligned in a direction perpendicular to the exhaust gas passage inside the casing and support the moving dust collecting electrode at a lower end thereof. The upper unit includes a plurality of upper rollers that are aligned and supported to face the lower rollers and support the moving dust collecting electrode at an upper end thereof.

With the above method, multiple moving dust collecting electrodes can be easily mounted, without determining on site the installation position for each moving dust collecting electrode.

[0021] The method according to still another aspect of the present invention, in which the upper unit has an insertion slot communicating with the upper opening and the upper rollers are supported inside the insertion slot, further includes carrying in the moving dust collecting electrode into the insertion slot.

With the above method, the moving dust collecting electrode can be carried into the casing without interfering with the upper unit.

[0022] The method according to still another aspect of the present invention further includes arranging an extended casing on the casing at a position facing the upper opening such that the upper end of the casing is heightened.

With the above method, the moving dust collecting electrode can be arranged in the existing casing without being affected by the height of the moving dust collecting electrode.

[0023] In the method according to still another aspect of the present invention, a guide plate is arranged such that exhaust gas that reaches a zone in an exhaust gas passage that is lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

With the above method, the exhaust gas is prevented from flowing toward the zone, which is lower than the discharge electrode of the moving dust collecting electrode, in which soot and dust are difficult to catch. The soot and dust in the exhaust gas can be thereby efficiently caught.

[0024] Meanwhile, an electrostatic precipitator according to still another aspect of the present invention includes a casing through which exhaust gas flows; a fixed electrode type electrostatic precipitator arranged upstream of an exhaust gas passage in the casing; a moving dust collecting electrode that is arranged downstream of the exhaust gas passage, and that includes a plurality of dust collecting electrodes that are coupled together to form a loop as a whole and circle around; a discharge electrode arranged at a position facing the moving dust collecting electrode; and a guide plate arranged such that the exhaust gas that reaches a zone in an exhaust gas passage lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

With the above structure, the exhaust gas is prevented from flowing toward the zone, which is lower than the discharge electrode of the moving dust collecting electrode, in which soot and dust are difficult to catch. The soot and dust in the exhaust gas can be thereby efficiently caught.

[0025] According to still another aspect of the present invention, a plurality of moving dust collecting electrodes are aligned in a direction perpendicular to the exhaust gas passage Lower rollers that support a lower end of each moving dust collecting electrode are supported by the lower unit. The guide plate is arranged on the lower unit.
With the above structure, the guide plate is mounted on the lower unit. This facilitates the mounting of the guide plate.

[0026] According to still another aspect of the present invention, an exhaust gas diffusing unit is arranged between the fixed electrode type electrostatic precipitator and the moving dust collecting electrode.

With the above structure, the exhaust gas can be distributed throughout the moving dust collecting electrode, and the soot and dust can be efficiently caught from the exhaust gas.

[0027] According to still another aspect of the present invention, the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing. The moving dust collecting electrode is arranged at a position from which some or all of the stages of the fixed electrode type electrostatic precipitator have been removed.

With the above method, how much the electrostatic precipitator is to be converted can be determined in accordance with the number of stages of the fixed electrode type electrostatic precipitator that are to be removed.

[0028] According to still another aspect of the present invention, the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing. A width of the moving dust collecting electrode is greater than a width of the fixed electrode type electrostatic precipitator. The moving dust collecting electrode is arranged at a position from which at least two adjacent stages of the fixed electrode type electrostatic precipitator have been removed.

With the above structure, the moving dust collecting electrode can be arranged in the casing without being affected by the width of the moving dust collecting electrode.

[0029] According to still another aspect of the present invention, diffusion space is formed between the moving dust collecting electrode and the fixed electrode type electrostatic precipitator to diffuse the exhaust gas. The exhaust gas diffusion unit is arranged in the diffusion space.

With the above structure, a sufficient passage length for diffusing the exhaust gas can be obtained, and the exhaust gas can be efficiently diffused by the exhaust gas diffusing unit.

[0030] According to still another aspect of the present invention, an upper opening is formed at a position facing the moving dust collecting electrode in an upper end of the casing. An extended casing is arranged on the casing at a position facing the upper opening so that the upper end of the casing is heightened.

With the above structure, the moving dust collecting electrode can be arranged in the casing without being affected by the height of the moving dust collecting electrode.

ADVANTAGES OF THE INVENTION
[0031] With a method for converting an electrostatic precipitator according to the present invention, and also with an electrostatic precipitator produced by such a method, a moving electrode type electrostatic precipitator can be arranged in a casing in which an existing fixed electrode type electrostatic precipitator is arranged, without requiring large work space. In the entire casing, the performance of catching soot and dust in exhaust gas can be enhanced.

BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a perspective view of an electrostatic precipitator (a single-stage fixed electrode type electrostatic precipitator and a single-stage moving electrode type electrostatic precipitator) according to an embodiment of the present invention;

FIG. 2 is a front elevational view of an electrostatic precipitator (a four-stage fixed electrode type electrostatic precipitator and a two-stage moving electrode type electrostatic precipitator) according to the present embodiment;

FIG. 3 is a partially enlarged view of FIG. 2, showing the two-stage moving electrode type electrostatic precipitator;

FIG. 4-a is a side view of the fixed electrode type electrostatic precipitator;

FIG. 4-b is a side view of the moving electrode type electrostatic precipitator;

FIG. 5-a is a plan view of an upper cover included in the moving electrode type electrostatic precipitator;

FIG. 5-b is a plan view of an upper unit included in the moving electrode type electrostatic precipitator;

FIG. 5-c is a plan view of a lower unit included in the moving electrode type electrostatic precipitator;

FIG. 6-a is a schematic view of a conversion process of the electrostatic precipitator (two-stage fixed electrode type electrostatic precipitator) that is yet to be converted according to the first embodiment;

FIG. 6-b is a schematic view of the conversion process at a step of removing a dust collecting electrode, a discharge electrode, a ceiling, and a hopper from a second stage of the fixed electrode type electrostatic precipitator;

FIG. 6-c is a schematic view of the conversion process at a step of mounting insulator rooms;

FIG. 6-d is a schematic view of the conversion process at a step of mounting the upper unit;

FIG. 7-a is a schematic frontal view of a first conversion process of the electrostatic precipitator (at a step of hoisting a discharge electrode frame after mounting the upper cover) according to the first embodiment;

FIG. 7-b is a schematic side view of the structure shown in FIG. 7-a;

FIG. 8-a is a schematic frontal view of the conversion process of the electrostatic precipitator (at a step of hoisting the discharge electrode) according to the first embodiment;

FIG. 8-b is a schematic side view of the structure shown in FIG. 8-a;

FIG. 9-a is a schematic frontal view of the conversion process of the electrostatic precipitator (before hoisting the moving dust collecting electrode) according to the first embodiment;

FIG. 9-b is a schematic side view of the structure shown in FIG. 9-a;

FIG. 10-a is a schematic frontal view of the conversion process of the electrostatic precipitator (after hoisting the moving dust collecting electrode) according to the first embodiment;

FIG. 10-b is a schematic side view of the structure shown in FIG. 10-a;

FIG. 11-a is a schematic frontal view of the conversion process of the electrostatic precipitator (at a step of hoisting the lower unit) according to the first embodiment;

FIG. 11-b is a schematic side view of the structure shown in FIG. 11-a;

FIG. 12-a is a schematic frontal view of the conversion process of the electrostatic precipitator (at a step of hoisting the hopper) according to the first embodiment;

FIG. 12-b is a schematic side view of the structure shown in FIG. 12-a;

FIG. 13-a is a schematic frontal view of the conversion process of the electrostatic precipitator according to the first embodiment (after mounting the hopper);

FIG. 13-b is a schematic side view of the structure shown in FIG. 13-a;

FIG. 14-a is a schematic diagram of the conversion process of the electrostatic precipitator (two-stage fixed electrode type electrostatic precipitator) that is yet to be converted according to a second embodiment;

FIG. 14-b is a schematic diagram of the conversion process at a step of carrying in the lower unit after removing the second stage of the fixed electrode type electrostatic precipitator;

FIG. 14-c is a schematic diagram of the conversion process at a step of carrying in the discharge electrode frame after mounting the insulator room;

FIG. 14-d is a schematic diagram of the conversion process at a step of carrying in the discharge electrode;

FIG. 15-a is a schematic diagram of the conversion process of the electrostatic precipitator at a step of mounting the upper unit according to the second embodiment;

FIG. 15-b is a schematic diagram of the conversion process at a step of carrying in the moving dust collecting electrode (when lowering);

FIG. 15-c is a schematic diagram of the conversion process at a step of carrying in the moving dust collecting electrode (immediately after lowering);

FIG. 15-d is a schematic diagram of the conversion process at a step of mounting the upper cover;

FIG. 16 is a side view of the structure shown in FIG. 15-b; and

FIG. 17 is a schematic diagram of a modification example of the electrostatic precipitator according to the present embodiment.

DETAILED DESCRIPTION
[0033] Exemplary embodiments of the present invention are explained in detail below with reference to the accompanying drawings. It should be noted, however, that structural components, and types, combinations, shapes, relative positioning thereof, and the like that are described here are not to limit the scope of the present invention unless otherwise specified, but merely provided as examples. [0034] FIG. 1 is a perspective view of an electrostatic precipitator (a single-stage fixed electrode type electrostatic precipitator and a single-stage moving electrode type electrostatic precipitator) according to the present embodiment. FIG. 2 is a front elevational view of an electrostatic precipitator (a four-stage fixed electrode type electrostatic precipitator and a two-stage moving electrode type electrostatic precipitator) according to the present embodiment. FIG. 3 is a partially enlarged view of FIG. 2, showing the two-stage moving electrode type electrostatic precipitator. Side views of the electrostatic precipitator according to the present embodiment are shown in FIG. 4 in which FIG. 4-a is a side view of the fixed electrode type electrostatic precipitator, and FIG. 4-b is a side view of the moving electrode type electrostatic precipitator. All of the above drawings show an electrostatic precipitator that has been converted with the method for converting the electrostatic precipitator according to the present embodiment.

[0035] The electrostatic precipitator that is before implementing the method for converting the electrostatic precipitator includes only a fixed electrode type electrostatic precipitator 28 in the casing. In the present embodiment, part (or all) of the fixed electrode type electrostatic precipitator 28 is replaced with a moving electrode type electrostatic precipitator 44.

[0036] An electrostatic precipitator 10 that has been converted in this manner includes a casing 12, the fixed electrode type electrostatic precipitator 28, a moving dust collecting electrode 46, and a discharge electrode 54 (or a discharge electrode 55, see FIG. 14). Exhaust gas flows through the casing 12. The fixed electrode type electrostatic precipitator 28 is arranged upstream of exhaust gas passage in the casing 12. The moving dust collecting electrode 4 6 is arranged downstream of the exhaust gas passage. The moving dust collecting electrode 46 has a plurality of dust collecting electrode plates 48 connected into a loop, and circles around as a whole. The discharge electrode 54 (the discharge electrode 55) is arranged inside the loop, and faces the moving dust collecting electrode 46. The electrostatic precipitator 10 further includes a guide plate 94 arranged in a zone lower than the lower end of the discharge electrode 54 (the discharge electrode 55) in the exhaust gas passage. The guide plate 94 guides the exhaust gas, which tends to flow toward the lower area, to a position higher than the lower end of the discharge electrode 54 (the discharge electrode 55). The upper end of the casing 12 corresponding to the position of the moving dust collecting electrode 46 is extended to agree with the height of the upper edge of the moving dust collecting electrode 46 (an upper unit 66).

[0037] The electrostatic precipitator 10 is explained in detail below and also converting methods according to first and second embodiments are explained.

The casing 12 defines the contour of the entire electrostatic precipitator 10 that has been converted (see FIG. 1). The electrostatic precipitator 10 is supported on a plurality of pillars 14 and installed at a certain height above the ground in the premises of a factory or the like. On front side of the casing 12, an inlet gas duct 16 is arranged, through which exhaust gas from boilers of a power plant, a factory, or the like flows in. On a side of the casing 12 opposite to the inlet gas duct 16, an outlet gas duct 18 is arranged, through which the exhaust gas is discharged after soot and dust are removed.

Consequently, an exhaust gas passage is formed along a line between the inlet gas duct 16 and the outlet gas duct 18 in the casing 12.

[0038] Pyramid-shaped hoppers 20 are arranged on the bottom surface of the casing 12 in a matrix. When the hoppers 20 are removed, a lower opening 64 (see FIG. 6) that is described later is formed in the bottom surface of the casing 12. The fixed electrode type electrostatic precipitator 28 is arranged upstream and the moving electrode type electrostatic precipitator 44 is arranged downstream of the exhaust gas passage in the casing 12. A gas distributor 24 is arranged between the inlet gas duct 16 and the fixed electrode type electrostatic precipitator 28 in the casing 12 in such a manner as to obstruct the entire exhaust gas passage. The gas distributor 24 has a large number of apertures 26 in a principal surface thereof, forming a meshed structure as a whole. The gas distributor 24 imparts a certain resistance to the flowing-in exhaust gas when the gas passes through the apertures 26. The exhaust gas thereby flows evenly throughout the casing, and the efficiency in catching soot and dust can be enhanced.

[0039] In the fixed electrode type electrostatic precipitator 28, fixed dust collecting electrodes 42 and discharge electrodes 30 are suspended from the upper end of the casing 12. Each of the fixed dust collecting electrodes 42 is suspended from the upper end of the casing 12 and arranged such that a normal line of the principal surface of the fixed dust collecting electrode 42 runs perpendicular to a direction of the exhaust gas passage. The fixed dust collecting electrodes 42 are arranged at certain intervals in a line along the direction of this normal line.

[0040] The discharge electrodes 30 are arranged at certain intervals with the principal surfaces thereof facing the principal surfaces of the fixed dust collecting electrode 42. That is, the discharge electrodes 30 and the fixed dust collecting electrodes 42 are alternately arranged in a line along a direction perpendicular to the exhaust gas passage. The discharge electrodes 30 are coupled to a discharge electrode frame 32 at their two ends on the passage side. The fixed dust collecting electrodes 42 are arranged as close as possible to the discharge electrodes 30. With this arrangement, when a negative voltage is applied to the discharge electrodes 30, negative ions are emitted from the discharge electrode 30 and propagated toward the fixed dust collecting electrode 42.

[0041] The discharge electrode frame 32 includes a beam 32a extending in an alignment direction of the discharge electrodes 30. The discharge electrodes 30 are coupled to this beam 32a. The discharge electrode frame 32 is coupled to a discharge electrode frame support 34 that is suspended from the upper end of the casing 12.

[0042] The discharge electrode frame support 34 is a rod member suspended from the bottom of an insulator room 38. The discharge electrode frame support 34 extends through conical insulators 36 arranged in the insulator room 38 to support the discharge electrode frame 32. The discharge electrode frame support 34 is therefore supported by the insulator room 38 via these insulators 36, and is electrically insulated from the insulator room 38 (casing 12). Consequently, the discharge electrode frame support 34, the discharge electrode frame 32, and the discharge electrode 30 are electrically insulated from the casing. The insulator room 38 is sealed off, and is kept warm in order to prevent condensation on the surfaces of the insulators 36 and also prevent leakage current. The discharge electrode frame support 34 is electrically connected to charging equipment 40 that is arranged outside the casing 12.

[0043] The casing 12 is grounded, and therefore the fixed dust collecting electrodes 42, which are directly connected to the casing 12, are also grounded. In contrast, a negative high voltage is applied to the discharge electrode frame support 34 by the charging equipment 40, and therefore a negative high voltage is also applied to the discharge electrode frame 32 and the discharge electrodes 30. Consequently, negative ions are emitted from the discharge electrodes 30 in a direction intersecting the exhaust gas passage and propagate toward the fixed dust collecting electrodes 42. In this state, when the exhaust gas is introduced through the inlet gas duct 16, negative ions become adhered to soot and dust contained in the exhaust gas. The soot and dust that become negatively charged get adhered to the fixed dust collecting electrodes 42, and removed from the exhaust gas. The soot and dust adhered to the fixed dust collecting electrodes 42 can be tapped off the fixed dust collecting electrodes 42 with a hammer (not shown) and collected at the bottom end of the hoppers 20. The soot and dust can be discharged from the casing 12 through a discharge outlet 22 formed at the bottom end of each hopper 20. [0044] The fixed electrode type electrostatic precipitator 28 including the fixed dust collecting electrodes 42, the discharge electrodes 30, the discharge electrode frame 32, the discharge electrode frame support 34, and the like is arranged in the casing 12 to have multiple stages along a direction of the exhaust gas passage. The number of stages is designed in accordance with specifications.

[0045] The moving electrode type electrostatic precipitator 44 includes the moving dust collecting electrodes 4 6, the discharge electrodes 54, the upper unit 66, a lower unit 84, and the like. Each moving dust collecting electrode 46 includes the dust collecting electrode plates 48 that are coupled together into a loop via a pair of loop chains 52. The dust collecting electrode plates 48 are arranged such that their principal surfaces are parallel to the direction of the exhaust gas passage. Connecting members 50 extend from the two edges of each dust collecting electrode plate 48 in the direction of the exhaust gas passage, and the connecting members 50 are coupled to the chains 52. The loop of the moving dust collecting electrode 46 forms arches in its upper and lower portions, while other portions of the loop are oriented in a vertical direction. A plurality of moving dust collecting electrodes 4 6 are arranged at certain intervals in the direction perpendicular to the exhaust gas passage, in the same manner as the fixed dust collecting electrodes 42 of the fixed electrode type electrostatic precipitator 28.

[0046] The discharge electrodes 54 are arranged at certain intervals such that their principal surfaces face the principal surfaces of the moving dust collecting electrodes 46. Some of the discharge electrodes 54 are arranged inside the loops formed by the moving dust collecting electrodes 46, while other discharge electrodes 54 are arranged between two adjacent moving dust collecting electrodes 46.

[0047] The discharge electrodes 54 and the moving dust collecting electrodes 4 6 are thereby aligned in a line along the direction perpendicular to the exhaust gas passage. The discharge electrodes 54 are coupled to a discharge electrode frame 56 at their two ends on the passage side. The moving dust collecting electrodes 46 are arranged as close as possible to the discharge electrodes 54. Accordingly, when a negative high voltage is applied to the discharge electrodes 54, negative ions are emitted from the discharge electrodes 54 and the negative ions propagate toward the moving dust collecting electrodes 46.

[0048] The discharge electrode frame 56 includes beams 56a that extend in an alignment direction of the discharge electrodes 54. The discharge electrodes 54 are coupled to the beams 56a. The discharge electrode frame 56 is coupled to discharge electrode frame supports 58 that are suspended from the upper end of the casing 12.

[0049] Each discharge electrode frame support 58 is a rod member suspended from the bottom of an insulator room 60. The discharge electrode frame support 58 extends through conical insulators 62 arranged in the insulator room 60 to support the discharge electrode frame 56. The discharge electrode frame support 58 is therefore supported by the insulator room 60 via these insulators 62, and is electrically insulated from the insulator room 60 (casing 12). The discharge electrode frame support 58 is electrically coupled to the charging equipment 4 0 or the like arranged outside the casing 12. The discharge electrode frame supports 58, the discharge electrode frame 56, and the discharge electrodes 54 are thereby electrically insulated from the casing 12. The insulator room 60 is arranged on the periphery of an upper opening 100 of the casing 12. The insulator room 60 extends in a longitudinal direction of the discharge electrode frame 56 (the direction perpendicular to the exhaust gas passage), and holds inside the insulators 62 that cap the discharge electrode frame supports 58.

[0050] When the moving dust collecting electrode 46 is designed to have its upper end higher than that of the fixed dust collecting electrode 42 of the fixed electrode type electrostatic precipitator 28, the upper end of the moving dust collecting electrode 4 6 would interfere with the upper end of the casing 12. In view of this problem, a portion of the upper end of the casing 12 that faces the moving dust collecting electrode 46 is formed into the upper opening 100 (see FIG. 6), allowing the moving dust collecting electrode 46 to extend out of the casing 12. The top portion of the casing 12 is covered by an extended casing (extending members 82, the insulator room 60, the upper unit 66, and an upper cover 74) in such a manner as to surround the upper opening 100. As a result, the casing 12 is now given a shape in which a portion of its upper end that faces the moving dust collecting electrode 46 (the upper unit 66) is extended in a height direction.

[0051] The extending member 82 heightens the upper end of the casing, and has, at its upper and lower ends, openings that are communicable with the upper opening 100. The upper cover 74 has an opening at its lower end. Although the upper unit 66 is a structural component of the moving electrode type electrostatic precipitator 44, it is formed as a body unified with the extended casing. The moving dust collecting electrode 4 6 is therefore sealed in an internal space defined by the casing 12 and the extended casing (the extending member 82, the insulator room 60, the upper unit 66, and the upper cover 74). Consequently, the moving electrode type electrostatic precipitator 44 can be mounted in the existing casing 12 without being affected by the height of the moving dust collecting electrode 46.

[0052] The width of each of the extending member 82, the insulator room 60, the upper unit 66, the upper cover 74, and the lower unit 84 is substantially the same as the width of the hopper 20 in the direction of the exhaust gas passage. The width in the direction perpendicular to the exhaust gas passage is suitably determined in accordance with the numbers of the moving dust collecting electrodes 46 and the discharge electrodes 54 that are aligned. The width of the upper opening 100 in the direction of the exhaust gas passage is determined so as not to interfere with the moving dust collecting electrode 46 or the like that is inserted through the upper opening. The width of the upper opening 100 in the direction perpendicular to the exhaust gas passage is suitably determined in accordance with the numbers of the moving dust collecting electrodes 4 6 and the discharge electrodes 54 that are aligned.

[0053] FIG. 5 is a schematic view of the electrostatic precipitator according to the present embodiment. FIG. 5-a is a plan view of the upper cover included in the moving electrode type electrostatic precipitator; FIG. 5-b is a plan view of the upper unit included in the moving electrode type electrostatic precipitator; and FIG. 5-c is a plan view of the lower unit included in the moving electrode type electrostatic precipitator.

[0054] The upper unit 66 is arranged between later-explained hoists 78 and the lower opening 64. The contour of the upper unit 66 is defined by a housing 68 that has an insertion slot 68a communicable with the upper opening 100 and the lower opening 64. The housing 68 extends in the alignment direction of the moving dust collecting electrodes 46. The housing 68 includes upper rollers 69 (a rotation shaft 70 and driving wheels 72) that are aligned in the direction perpendicular to the exhaust gas passage in the casing 12 and are supported in the insertion slot 68a. Each upper roller 69 supports the upper end of the moving dust collecting electrode 46.

[0055] The upper roller 69 includes the rotation shaft 70, the driving wheels 72, and a motor (not shown) that rotates the rotation shaft 70. The rotation shaft 70 is supported by the housing 68 and arranged to correspond to the alignment of the moving dust collecting electrodes 46. The driving wheels 72 support the upper end of the moving dust collecting electrode 4 6 (an arch portion of the loop) by engaging with the chains 52, and also rotate together with the rotation shaft 70 so that the moving dust collecting electrode 4 6 loops along the chains 52. The rotation shaft 70 is coupled at its longitudinal ends to the side surfaces of the passage of the insertion slot 68a. The multiple upper rollers 69 are therefore arranged at positions of the arch portions of the moving dust collecting electrodes 46 in the alignment direction of the moving dust collecting electrodes 46. [0056] The upper cover 74 is a cover member that extends in the alignment direction of the moving dust collecting electrodes 4 6 and is arranged on top of the upper unit 66. A pair of rails 76 is mounted on the inner top surface (or side surface) of the upper cover 74 and extends in the alignment direction of the discharge electrodes 54. Two or more hoists 78 are mounted on the rails 76.

[0057] The hoists 78 are movable in the longitudinal direction of the rails 76. The hoists 78 perform a hoisting operation or the like for a component that is to be carried in while adjusting a feeding length of wire 80. The rails 7 6 and the hoists 78 are arranged at positions such that the wire 80 fed by the hoist 78 can pass through the insertion slot 68a.

[0058] Similar to the upper unit 66, the lower unit 84 includes a housing 86 and a plurality of lower rollers 87 (a rotation shaft 88 and lower wheels 90). The housing 86 extends in the alignment direction of the moving dust collecting electrodes 46 and is coupled to the casing 12. The lower rollers 87 are arranged to face the upper rollers 69 and supported by the housing 86. The lower rollers 87 support the lower ends of the moving dust collecting electrodes. [0059] Each lower roller 87 includes the rotation shaft 88 and the lower wheels 90. The rotation shaft 88 is arranged to correspond to the alignment of the moving dust collecting electrodes 46. The lower wheels 90 are engaged with the chains 52 so as to support the lower end of the moving dust collecting electrode 4 6 (the arch portion of the loop). The lower wheels 90, upon receiving the looping force (circling movement) of the chains 52, rotate together with the rotation shaft 88. A plurality of rotation shafts 88 are arranged exactly below the rotation shafts 70 supported by the upper unit 66.

[0060] The lower unit 84 is a column member that is supported by the housing 8 6 and extends in the direction perpendicular to the alignment direction of the moving dust collecting electrodes 46. The lower unit 84 includes a pair of rotary brushes 92 arranged to grip each of the dust collecting electrode plates 48 of the moving dust collecting electrode 46 from either side. The central shafts of the rotary brushes 92, for example, extend out of the casing 12, and are coupled to a motor (not shown) outside the casing 12 to rotate the rotary brushes 92. As shown in FIG. 4-b, the rotary brushes 92 rotate in a direction opposite to each other, and the peripheries of the rotary brushes 92 on the sides facing each other rotate in a direction opposite to the moving direction of the dust collecting electrode plates 48. The rotary brushes 92 can thereby remove soot and dust adhered to the surfaces of the dust collecting electrode plates 48, and deposit the removed soot and dust on the lower end of the hopper 20. Accordingly, the soot and dust can be collected without being attracted again toward the rotary brushes 92 and the dust collecting electrode plates 48.

[0061] With the above arrangement, the moving dust collecting electrode 46 circles around, with the driving wheels 72 at its upper end and the lower wheels 90 at its lower end. Meanwhile, the discharge electrode 54 is arranged such that its lower end is above the lower unit 84 and its upper end is below the upper unit 66. The discharge electrode 54 thereby prevents negative ions from propagating anywhere other than the moving dust collecting electrode 46. This makes it difficult to efficiently remove soot and dust from the exhaust gas that flows particularly in a height range between the lower end of the lower unit 8 and the lower end of the discharge electrode 54. In addition, in certain situation, as in the present embodiment, the moving dust collecting electrode 46 and the discharge electrode 54 extend higher than the dust collecting electrode plates 48 of the fixed electrode type electrostatic precipitator 28. In these situations, if the moving dust collecting electrode 4 6 and the discharge electrode 54 are arranged downstream of the fixed electrode type electrostatic precipitator 28 in the casing 12, the exhaust gas may not be distributed evenly throughout the moving dust collecting electrode 4 6 and the discharge electrode 54.

[0062] To address this problem, the guide plates 94 are mounted in the lower unit 84 at the two ends of the exhaust gas passage, as shown in FIGS. 2 and 3. The lower ends of the guide plates 94 are coupled to the hopper 20, and the upper ends are substantially at the same height as the lower end of the discharge electrode 54. The guide plates 94 thereby block the exhaust gas passage between their lower and upper ends. The exhaust gas that reaches a zone lower than the lower end of the discharge electrode 54 can be guided toward a position higher than the lower end of the discharge electrode 54. Consequently, the exhaust gas can be prevented from flowing in a zone lower than the discharge electrode 54 (or the discharge electrode 55 in FIG. 14) of the moving dust collecting electrode 46, in which the soot and dust are difficult to catch, and the soot and dust can be efficiently caught in the exhaust gas. The guide plates 94 and the discharge electrodes 54 are not brought into contact with each other. The guide plates 94 are arranged in the lower unit 84 in the above manner, and therefore the installation of the guide plates 94 can be facilitated.

[0063] As shown in FIG. 2, an inlet distributor 96 having the same structure as the gas distributor 24 is arranged between the fixed electrode type electrostatic precipitator 28 and the moving electrode type electrostatic precipitator 44. The inlet distributor 96 serves as an exhaust gas diffusing unit, making the exhaust gas passage evenly flow into the moving electrode type electrostatic precipitator 44 (the moving dust collecting electrodes 4 6 and the discharge electrodes 54). An outlet distributor 98 having the same structure as the inlet distributor 96 is also arranged downstream of the exhaust gas passage in the moving electrode type electrostatic precipitator 44. A flow rate of the exhaust gas can be thereby reduced in a zone between the inlet distributor 96 and the outlet distributor 98, or in other words, when the gas passes through the moving electrode type electrostatic precipitator 44, which makes catching of soot and dust more efficient.

[0064] In the above structure, the upper unit 66 and the lower unit 84, which are coupled to the casing 12, are grounded. This means that the moving dust collecting electrodes 46, which are coupled to the upper unit 66 (the driving wheels 72) and the lower unit 84 (the lower wheels 90), are also grounded. Meanwhile, the discharge electrodes 54, the discharge electrode frame 56, and the discharge electrode frame supports 58 are insulated from the casing 12, and a negative high voltage is applied thereto. Subsequently, negative ions are emitted from the discharge electrodes 54 in the direction intersecting the exhaust gas passage, and propagate toward the dust collecting electrode plates 48 of the moving dust collecting electrodes 46. In this state, when the exhaust gas is introduced through the inlet gas duct 16, negative ions adhere to the soot and dust in the exhaust gas that has passed through the fixed electrode type electrostatic precipitator 28. The negatively charged soot and dust adhere to the dust collecting electrode plates 48, and are removed from the exhaust gas. The exhaust gas from which the soot and dust is removed is discharged through the outlet gas duct 18.

[0065] When a dust collecting electrode plate 48 comes into contact with the rotary brushes 92, the dust and soot adhered to the dust collecting electrode plate 48 are swept off by the rotary brushes 92 and accumulated at the lower end of the hopper 20. Thereafter, the soot and dust are discharged from the casing 12 through the discharge outlet 22 arranged at the lower end of the hopper 20.

[0066] The moving electrode type electrostatic precipitator 44 including the moving dust collecting electrodes 46, the discharge electrodes 54, and the like is arranged to have multiple stages in the casing 12 along the direction of the exhaust gas passage.

The number of stages can be designed in accordance with the specifications of the conversion. [0067] FIGS. 6 to 13 are diagrams showing a conversion process of the electrostatic precipitator according to the first embodiment. FIG. 6 is a front elevational view. As shown in FIGS. 7 to 13, FIG. X-a indicates a front elevational view, while FIG. X-b indicates a side view.

Conversion of the fixed electrode type electrostatic precipitator shown in FIG. 6-a to replace the fixed electrode type electrostatic precipitator 28 on the right side with the moving electrode type electrostatic precipitator 44 is explained. First, as shown in FIG. 6-b, the hopper 20 immediately below the to-be-removed fixed electrode type electrostatic precipitator 28 is removed to create the lower opening 64, and the upper opening 100 is created in the upper end of the casing 12 at a position facing the to-be-removed fixed electrode type electrostatic precipitator 28. Thereafter, the fixed electrode type electrostatic precipitator 28 is removed through the lower opening 64 or the upper opening 100 by a crane (not shown) or the like.

[0068] Next, as shown in FIG. 6-c, the extending member 82 and the insulator room 60 are hoisted by using the crane (not shown) or the like and mounted to surround the periphery of the upper opening 100 on the casing 12. Prior to this mounting, the insulators 62 and the discharge electrode frame supports 58 are mounted in the insulator room 60. The inlet distributor 96 (and the outlet distributor 98 (not shown)) can also be mounted at this timing. Thereafter, as shown in FIG. 6-d, the upper unit 66 and the upper cover 74 are hoisted with the crane (not shown) or the like and mounted on the insulator room 60.

[0069] Next, the discharge electrode frame 56 is positioned beneath the lower opening 64. Then, as shown in FIG. 7, the wire 80 is fed from the hoist 78 mounted on the upper cover 74, and the wire 80 is inserted into the insertion slot 68a and the upper opening 100. The wire 80 is connected to the discharge electrode frame 56 for hoisting, and the discharge electrode frame 56 is thereby carried through the lower opening 64. Thereafter, the discharge electrode frame 56 is coupled to the discharge electrode frame supports 58 by welding or the like.

[0070] The discharge electrode 54 is positioned beneath the lower opening 64. Then, as shown in FIG. 8, the wire 80 is fed from the hoist 78 as described above to hoist the discharge electrode 54. The discharge electrode 54 is thereby carried through the lower opening 64. Thereafter, the discharge electrode 54 is coupled to the discharge electrode frame 56 by welding or the like. The operation of moving the hoist 78 as necessary along the rails 76, hoisting a discharge electrode 54, and then coupling it to the discharge electrode frame 56 is repeated for the multiple discharge electrodes 54. [0071] Next, a pair of moving dust collecting electrodes 46a, each of the chains 52 of which is cut into half, is positioned beneath the lower opening 64. As shown in FIG. 9, a balance scale 78a is coupled to the tips of the fed wire 80. The pair of moving dust collecting electrodes 46 is hoisted by this balance scale 78a and carried through the lower opening 64. Thereafter, as shown in FIG. 10, the moving dust collecting electrodes 46a are hoisted to a height beyond the upper ends of the driving wheels 72 mounted in the upper unit 66. The pair of moving dust collecting electrodes 46 is held at positions to face each other across the driving wheels 72. Then, the chains 52a are detached from the hoists 78, and are attached to each other and engaged with the driving wheels 72. It is preferable that the rotation shaft 70 be locked so as not to rotate, preventing the moving dust collecting electrodes 46 from coming off the driving wheels 72.

[0072] The operation of moving the hoist 78 as necessary along the rails 76, hoisting a pair of moving dust collecting electrodes 46a, and coupling the hoisted moving dust collecting electrodes 4 6a to each other is repeated for the multiple moving dust collecting electrodes 46a. By this operation, the moving dust collecting electrodes 46 (the discharge electrodes 54) are aligned in a direction perpendicular to the exhaust gas passage. [0073] Thereafter, the lower unit 84 is positioned beneath the lower opening 64. As shown in FIG. 11, the lower unit 84 is hoisted by the hoist 78 via the balance scale 78a and is carried through the lower opening 64. The lower unit 84 is hoisted until the pair of moving dust collecting electrodes 46a reaches a position where the moving dust collecting electrodes 46a face each other across the lower wheels 90. During this hoisting, one of the moving dust collecting electrodes 46a is inserted between the pair of rotary brushes 92 arranged in the lower unit 84. The portions of the chains 52a, which are the lower ends of the moving dust collecting electrodes 46a, are coupled to each other into the loop-forming chains 52 and are engaged with the lower wheels 90. The moving dust collecting electrodes 46 having the dust collecting electrode plates 48 form, as a whole, a loop, and are arranged at positions facing the discharge electrodes 54. The lower unit 84 is coupled to the casing 12. Prior to hoisting the lower unit 84, the guide plates 94 are mounted to the lower unit 84 in advance.

[0074] Finally, the hopper 20 is arranged beneath the lower opening 64 that has been detached, and hoisted, as shown in FIG. 12, by the hoist 78 via the balance scale 78a. Thereafter, as shown in FIG. 13, the hopper 20 is mounted on the lower end of the casing 12 to seal the lower opening 64, thereby completing the conversion process. Even after completion of the conversion process, the hoists 78 can remain to be used for future maintenance or the like.

[0075] In the above conversion process, the moving dust collecting electrodes 46, the discharge electrodes 54, and the like need not be hoisted across and over the casing 12, and therefore the moving electrode type electrostatic precipitator 44 having a large body can be efficiently carried into the casing 12. In addition, the discharge electrode 54 and the moving dust collecting electrode 46 are hoisted by the hoist 78 that is supported by the casing 12. Thus, even the existing electrostatic precipitator 10 in which sufficient work space is difficult to obtain can be efficiently converted to the moving electrode type electrostatic precipitator 44. Similarly, the hopper 20 can be easily hoisted so that the upper opening 100 can be easily sealed.

[0076] The hoists 78 movable along the rails 76 are arranged on the upper cover 74. This allows a number of discharge electrodes 54 and moving dust collecting electrodes 46 to be efficiently carried in, even in the existing electrostatic precipitator 10 in which sufficient work space is difficult to obtain. [0077] The moving dust collecting electrodes 46 and the discharge electrodes 54 need not be hoisted across and over the casing 12, and therefore the moving electrode type electrostatic precipitator 44 having the large body can be efficiently carried into the casing 12. With the above method, the exhaust gas is prevented from passing in the zone of the moving dust collecting electrode 46 below the discharge electrode 54, where soot and dust are difficult to catch. The soot and dust in the exhaust gas can be thereby efficiently caught.

[0078] According to the present embodiment, the upper rollers 69 that support the moving dust collecting electrodes 46 at their upper ends are coupled to the upper unit 66, while the lower rollers 87 that support the moving dust collecting electrodes 46 at their lower ends are coupled to the lower unit 84. The upper unit 66 and the lower unit 84 are carried into the casing 12 and mounted at positions corresponding to the installation position of the moving dust collecting electrode 46. With this arrangement, the installation position need not be determined on site for each moving dust collecting electrode 46. Furthermore, with the insertion slot 68a formed in the upper unit 66, the multiple moving dust collecting electrodes 46 can be easily installed without any interference between the hoist 7 8 and the upper unit 66.

[007 9] In the above explanation of the conversion process, part (one stage) of the fixed electrode type electrostatic precipitator 28 having multiple stages is replaced with the moving electrode type electrostatic precipitator 44; however, more than one stage of the fixed electrode type electrostatic precipitator 28, or all of the fixed electrode type electrostatic precipitator 28 in the casing 12 can be replaced with the moving electrode type electrostatic precipitator 44. In a conversion process of carrying in a moving electrode type electrostatic precipitator 44 adjacent to a previously carried moving electrode type electrostatic precipitator 44, the two moving electrode type electrostatic precipitators 44 would not interfere with each other, nor would they after the conversion process. Some stages of a multiple-stage fixed electrode type electrostatic precipitator 28 therefore can be replaced with the moving electrode type electrostatic precipitators 44 at a time, which makes the conversion even more efficient.

Consequently, how much the electrostatic precipitator 10 is to be converted can be determined based on the number of stages of the fixed electrode type electrostatic precipitator 28 that are to be removed. [0080] FIGS. 14 and 15 are schematic diagrams of the conversion process of the electrostatic precipitator according to the second embodiment. FIG. 14-a shows a pre-conversion state, FIG. 14-b shows a step of carrying in the lower unit after removing the fixed electrode type electrostatic precipitator, FIG. 14-c shows a step of carrying in the discharge electrode frame after mounting the insulator room, and FIG. 14-d is a step of carrying in the discharge electrode. FIG. 15-a shows a step of mounting the upper unit, FIG. 15-b shows a step of carrying in the moving dust collecting electrode (at lowering), FIG. 15-c shows a step of carrying in the moving dust collecting electrode (immediately after lowering), and FIG. 15-d shows a step of mounting the upper cover.

[0081] In the conversion process of the electrostatic precipitator according to the second embodiment, the hopper 20 is not removed. Instead, the fixed electrode type electrostatic precipitator 28 is carried out through the upper portion of the casing 12, and the moving electrode type electrostatic precipitator 44 is carried in. In the explanation of the second embodiment, similar to the first embodiment, the second-stage fixed electrode type electrostatic precipitator 28 is replaced with the moving electrode type electrostatic precipitator 44 as shown in FIG. 14-a. First, as shown in FIG. 14-b, the upper opening 100 is formed in the casing 12 at a position facing the to-be-removed fixed electrode type electrostatic precipitator 28. The to-be-removed fixed electrode type electrostatic precipitator 28 is hoisted with the crane (with its main body not shown) or the like, and removed from the casing 12. Thereafter, the lower unit 84 (with the guide plates 94 attached) is hoisted with the crane (with its main body not shown), carried through the upper opening 100 into the casing 12, and coupled to the lower portion of the casing 12. [0082] Next, as shown in FIG. 14-c, the extending members 82 and the insulator room 60 (with the discharge electrode frame supports 58 coupled) are sequentially hoisted with the crane (with its main body not shown) and coupled at the position surrounding the periphery of the upper opening 100 in the upper portion of the casing 12. A discharge electrode frame 57 is lowered with the crane (with its main body not shown), carried in through the upper opening 100, and coupled to the discharge electrode frame support 58.

[0083] As shown in FIG. 14-d, the discharge electrode 55 is carried in through the upper opening 100 with the crane (with its main body not shown) and coupled to the discharge electrode frame 57. Multiple discharge electrodes 55 are arranged in the direction perpendicular to the exhaust gas passage, and therefore the operation of carrying in and coupling the discharge electrodes 55 is repeated in accordance with the number of discharge electrodes 55.

[0084] Next, as shown in FIG. 15-a, the upper unit 66 is hoisted with the crane (with its main body not shown) and coupled to the insulator room 60. Thereafter, the moving dust collecting electrode 4 6 is lowered with the crane (with its main body not shown) via a balance scale, inserted through the insertion slot 68a of the upper unit 66 and the upper opening 100, and carried into the casing 12 (FIG. 15-b). Here, as shown in FIG. 16, the moving dust collecting electrodes 46 are carried to positions where each of the moving dust collecting electrodes 46 is engaged with the driving wheels 72 mounted in the upper unit 66. When the moving dust collecting electrodes 46 are lowered into the casing 12, each of the chains 52 is cut at the lower end that comes at lowering so that two strands of chains 52a are formed. As shown in FIG. 15-c, the upper ends of the chains 52 in the moving dust collecting electrode 46 are engaged with the driving wheels 72.

[0085] Finally, as shown in FIG. 15-d, with the chains 52a engaged with the lower wheels 90, the chains 52a are connected into the chains 52. An upper cover 75 is lowered with the crane (with its main body not shown) and coupled onto the upper unit 66, thereby completing the conversion process. The present embodiment is effective when there is a sufficient space for setting up the crane (with its main body not shown) outside the casing 12 or when the moving dust collecting electrodes 46 or the like that are to be carried in have small bodies. This structure does not require the rails 76 or the hoists 78 in the upper cover 75. The discharge electrode frame 57 and the discharge electrode 55 have the same functions as the discharge electrode frame 56 and the discharge electrode 54. If the discharge electrode frame 57 and the discharge electrode 55 interfere with the edge of the upper opening 100 (or with the insulator room 60), various dimensions can be adjusted so that the discharge electrode frame 57 and the discharge electrode 55 can be carried in through the upper opening 100.

[0086] With the above method, in the existing casing 12, the fixed electrode type electrostatic precipitator 28 can be replaced with the moving electrode type electrostatic precipitator 44 that includes the discharge electrodes 55 and the moving dust collecting electrodes 46. In addition, because of the insertion slot 68a formed in the upper unit 66, the moving dust collecting electrode 46 can be efficiently carried into the casing 12 by inserting the moving dust collecting electrode 46 into the insertion slot 68a, without interfering with the upper unit 66.

The moving dust collecting electrode 46 can be efficiently carried in.

[0087] FIG. 17 shows a modification example of the electrostatic precipitator according to the present embodiment. As discussed above, in the electrostatic precipitator 10, the fixed electrode type electrostatic precipitator 28 is arranged in the casing 12 to have multiple stages in the direction of the exhaust gas passage in the casing 12. In this modification example, some (or all) of the stages of the fixed electrode type electrostatic precipitator 28 are removed, and a moving electrode type electrostatic precipitator 45 (the moving dust collecting electrode and the discharge electrode) is installed at a position from which the fixed electrode type electrostatic precipitator 28 is removed.

[0088] In the first and second embodiments, it is assumed that the width of the moving electrode type electrostatic precipitator 44 in the direction of the exhaust gas passage is substantially equal to the width of the fixed electrode type electrostatic precipitator 28. As shown in the modification example, however, the width of the moving electrode type electrostatic precipitator 45 can be greater than that of the fixed electrode type electrostatic precipitator 28. In such a situation, as shown in FIG. 17, two adjacent stages or more of the fixed electrode type electrostatic precipitator 28 are removed, and the moving electrode type electrostatic precipitator 45 is installed at the removed position. As shown in FIG. 17, three adjacent stages of the fixed electrode type electrostatic precipitator 28 along the exhaust gas passage are removed, and the moving electrode type electrostatic precipitator 45 is installed at the removed position. Consequently, how much the electrostatic precipitator 10 is converted can be determined in accordance with the number of to-be-removed stages of the fixed electrostatic precipitator 28 or the dimension (i.e., the width in the direction of the exhaust gas passage) of the moving dust collecting electrode (the moving electrode type electrostatic precipitator 45).

[0089] It is preferable that, when installing the moving electrode type electrostatic precipitator 45, diffusion space 102 be formed to enhance diffusion of the exhaust gas, as shown in FIG. 17, instead of installing the moving electrode type electrostatic precipitator 45 immediately next to the fixed electrode type electrostatic precipitator 28. It is also preferable that the inlet distributor 96 that is mentioned earlier be arranged in this diffusion space 102. With this arrangement, a sufficient passage length for diffusing the exhaust gas can be obtained, and the inlet distributor 96 can efficiently diffuse the exhaust gas.

[0090] The moving electrode type electrostatic precipitator 45 shown in FIG. 17 has a different width from the widths of the moving electrode type electrostatic precipitators 44 according to the first and second embodiments, but has basically the same structure. Numerals of structural components in FIG. 17 denote structural components having the same numerals in FIG. 2 or the like. The moving electrode type electrostatic precipitator 45 can be carried into the casing 12 with the conversion processes according to the first and second embodiments, and therefore the detailed explanation is omitted. Consequently, the moving dust collecting electrode 46 can be arranged in the casing 12, without being affected by the width of the moving dust collecting electrode 46.

INDUSTRIAL APPLICABILITY
[0091] The present invention can be used as a converting method for replacing, in an existing casing in which a fixed electrode type electrostatic precipitator is housed, the fixed electrode type electrostatic precipitator with a moving electrode type electrostatic precipitator including a discharge electrode and a moving dust collecting electrode, and also as an electrostatic precipitator produced by using this converting method.

EXPLANATIONS OF LETTERS OR NUMERALS
[0092] 10: electrostatic precipitator; 12: casing; 14: pillars; 16: inlet gas duct; 18: outlet gas duct; 20: hopper; 22: discharge outlet; 24: gas distributor; 26: apertures; 28: fixed electrode type electrostatic precipitator; 30: discharge electrode; 32: discharge electrode frame; 32a: beam; 34: discharge electrode frame support; 36: insulator; 38: insulator room; 40: charging equipment; 42: fixed dust collecting electrode; 44: moving electrode type electrostatic precipitator; 45: moving electrode type electrostatic precipitator; 46: moving dust collecting electrode; 46a: moving dust collecting electrode; 48: dust collecting electrode plate; 50: connecting member; 52: chain; 52a: chain; 54: discharge electrode; 55: discharge electrode; 56: discharge electrode frame; 57: discharge electrode frame; 56a: beam; 58: discharge electrode frame support; 60: insulator room; 62: insulator; 64: lower opening; 66: upper unit; 68: housing; 68a: insertion slot; 69: upper roller; 70: rotation shaft; 72: driving wheel; 74: upper cover; 75: upper cover; 76: rail; 78: hoist; 78a: balance scale; 80: wire; 82: extending member; 84: lower unit; 86: housing; 87: lower roller; 88: rotation shaft; 90: lower wheel; 92: rotary brushes; 94: guide plate; 96: inlet distributor; 98: outlet distributor; 100: upper opening; 102: diffusion space.

We claim:
1. A method for converting an electrostatic precipitator in which a fixed electrode type electrostatic precipitator is arranged in a casing, comprising:

replacing the fixed electrode type electrostatic precipitator with a moving dust collecting electrode and a discharge electrode corresponding to the moving dust collecting electrode.

2. The method for converting the electrostatic precipitator according to Claim 1, wherein the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of an exhaust gas passage inside the casing, the method further comprising:

removing some or all of the stages of the fixed electrostatic precipitator and then mounting the moving dust collecting electrode and the discharge electrode at a position from which the fixed electrode type electrostatic precipitator has been removed.

3. The method for converting the electrostatic precipitator according to Claim 1, further comprising:

forming a lower opening by removing a hopper from a position facing the fixed electrode type electrostatic precipitator at a lower end of the casing;

arranging a hoist at a position facing the lower opening in the casing; and

hoisting the moving dust collecting electrode and the discharge electrode with the hoist and carrying in the moving dust collecting electrode and the discharge electrode through the lower opening.

4. The method for converting the electrostatic precipitator according to Claim 3, further comprising:

arranging an upper unit at a position between the hoist and the lower opening, the upper unit including a housing that has an insertion slot communicating with the lower opening and a plurality of upper rollers that are aligned in a direction perpendicular to the direction of the exhaust gas passage inside the casing, are supported in the insertion slot, and support the moving dust collecting electrode at an upper end thereof; and

hoisting a lower unit with a wire fed from the hoist and inserted into the insertion slot, and carrying in the lower unit through the lower opening, the lower unit including a plurality of lower rollers that are aligned to face the upper rollers and support the moving dust collecting electrode at a lower end thereof.

5. The method for converting the electrostatic precipitator according to Claim 3, further comprising:

hoisting the hopper with the hoist, and sealing the lower opening.

6. The method for converting the electrostatic precipitator according to Claim 4, wherein a rail that extends in a direction perpendicular to the exhaust gas passage across the casing is arranged on the upper unit at a position facing the insertion slot, the method further comprising:

hoisting the moving dust collecting electrode with the hoist arranged on the rail so as to be movable along the rail; and

repeating an operation of moving the hoist and hoisting another moving dust collecting electrode, thereby aligning a plurality of moving dust collecting electrodes in the direction perpendicular to the exhaust gas passage.

7. The method for converting the electrostatic precipitator according to Claim 1, further comprising:

forming an upper opening in an upper end of the casing at a position facing the fixed electrode type electrostatic precipitator;

carrying in a lower unit through the upper opening, and arranging the lower unit in the casing, the lower unit including a plurality of lower rollers that are aligned in a direction perpendicular to the exhaust gas passage inside the casing and support the moving dust collecting electrode at a lower end thereof; and

arranging an upper unit on the casing at a position facing the upper opening, the upper unit including a plurality of upper rollers that are aligned and supported to face the lower rollers and support the moving dust collecting electrode at an upper end thereof.

8. The method for converting the electrostatic precipitator according to Claim 7, wherein the upper unit has an insertion slot communicating with the upper opening, and the upper rollers are supported inside the insertion slot, the method further comprising:

carrying in the moving dust collecting electrode into the insertion slot.

9. The method for converting the electrostatic precipitator according to Claim 1, further comprising:

arranging an extended casing on the casing at a position facing the upper opening such that the upper end of the casing is heightened.

10. The method for converting the electrostatic precipitator according to Claim 1, wherein a guide plate is arranged such that exhaust gas that reaches a zone in an exhaust gas passage that is lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

11. An electrostatic precipitator comprising:

a casing through which exhaust gas flows;

a fixed electrode type electrostatic precipitator arranged upstream of an exhaust gas passage in the casing;

a moving dust collecting electrode that is arranged downstream of the exhaust gas passage, and that includes a plurality of dust collecting electrodes that are coupled together to form a loop as a whole and circle around;

a discharge electrode arranged at a position facing the moving dust collecting electrode; and

a guide plate arranged such that the exhaust gas that reaches a zone in an exhaust gas passage lower than a lower end of the discharge electrode is guided toward a position higher than the lower end of the discharge electrode.

12. The electrostatic precipitator according to Claim 11, wherein a plurality of moving dust collecting electrodes are aligned in a direction perpendicular to the exhaust gas passage, lower rollers that support a lower end of each moving dust collecting electrode are supported by the lower unit, and the guide plate is arranged on the lower unit.

13. The electrostatic precipitator according to Claim 11, wherein an exhaust gas diffusing unit is arranged between the fixed electrode type electrostatic precipitator and the moving dust collecting electrode.

14. The electrostatic precipitator according to Claim 11, wherein the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing, and

the moving dust collecting electrode is arranged at a position from which some or all of the stages of the fixed electrode type electrostatic precipitator have been removed.

15. The electrostatic precipitator according to Claim 11, wherein

the fixed electrode type electrostatic precipitator is arranged in the casing to have a plurality of stages in a direction of the exhaust gas passage inside the casing,

a width of the moving dust collecting electrode is greater than a width of the fixed electrode type electrostatic precipitator, and

the moving dust collecting electrode is arranged at a position from which at least two adjacent stages of the fixed electrode type electrostatic precipitator have been removed.

16. The electrostatic precipitator according to Claim 15, wherein

diffusion space is formed between the moving dust collecting electrode and the fixed electrode type electrostatic precipitator to diffuse the exhaust gas, and
an exhaust gas diffusing unit is arranged in the diffusion space.

17. The electrostatic precipitator according to Claim 11, wherein
an upper opening is formed at a position facing the moving dust collecting electrode in an upper end of the casing, and an extended casing is arranged on the casing at a position facing the upper opening so that the upper end of the casing is heightened.