JP2021133305A - Electric dust collector - Google Patents

Abstract

To provide an electric dust collector which can enhance dust collection efficiency by a dust collection section by controlling flow rate of exhaust gas at the time of passing the inside of the dust collection section.SOLUTION: An electric dust collector includes: an inlet duct; and a dust collection section into which exhaust gas is introduced through the inlet duct. An enlargement flow passage which has flow passage area gradually increasing along a flow direction of the exhaust gas is defined on an inner peripheral surface of the inlet duct. The enlargement flow passage has a shield plate perpendicular to the flow direction of the exhaust gas. The shield plate has a shield section in a region located outside an uppermost stream section of the enlargement flow passage in an axial view of the enlargement flow passage.SELECTED DRAWING: Figure 2

Description

The present invention relates to an electrostatic precipitator.

At business establishments that use coal-fueled heat supply systems, such as thermal power plants and steel mills, electrostatic precipitators are used to electrically collect the dust from exhaust gas containing dust. In this electrostatic precipitator, the flow path area on the inner peripheral surface of the inlet duct along the flow direction of the exhaust gas so that the flow velocity of the exhaust gas passing through the dust collector is smaller than the flow velocity when the exhaust gas passes through the inlet duct. There is an expansion channel that gradually increases.

In this electrostatic precipitator, a technique of providing a perforated plate in the expanded flow path has been proposed in order to make the flow velocity of the exhaust gas passing through the expanded flow path uniform (see Japanese Patent Application Laid-Open No. 2001-232235).

Japanese Unexamined Patent Publication No. 2001-232235

Patent Document 1 describes that the perforated plate is divided into a plurality of regions so that the flow velocity distribution of the exhaust gas can be made uniform, and the aperture ratio is changed for each region. Patent Document 1 describes that the aperture ratio of the perforated plate is changed based on the distribution of the flow velocity of the exhaust gas at the time of passing through the perforated plate. On the other hand, in Patent Document 1, the flow velocity of the exhaust gas at the time of passing through the dust collecting portion is not examined. Therefore, the perforated plate described in Patent Document 1 has room for further improvement.

The present invention has been made based on such circumstances, and can improve the dust collection efficiency by the dust collector by controlling the flow velocity of the exhaust gas at the time of passing through the dust collector. The purpose is to provide the device.

The electrostatic precipitator according to one aspect of the present invention made to solve the above problems is an electrostatic precipitator including an inlet duct and a dust collector in which exhaust gas is introduced through the inlet duct. An enlarged flow path whose flow path area gradually increases along the flow direction of the exhaust gas is defined on the inner peripheral surface of the inlet duct, and the expanded flow path is shielded perpendicular to the flow direction of the exhaust gas. A plate is provided, and the shielding plate has a shielding portion in a region located outside the most upstream portion of the enlarged flow path in the axial view of the enlarged flow path.

As a result of diligent studies by the present inventors, even when a conventional perforated plate is provided in the expansion flow path, the exhaust gas passing through the peripheral edge of the expansion flow path is collected after being introduced into the dust collection section. It was found that the flow velocity in the dust collecting portion tends to be higher than that in other portions because the dust flows along the inner surface of the casing of the dust portion. The electrostatic precipitator was introduced into the dust collecting portion because the shielding plate is arranged in the expanding flow path and the shielding plate has a shielding portion at the peripheral edge of the expanding flow path. It is possible to suppress the partial increase in the flow velocity of the exhaust gas. Therefore, the electrostatic precipitator can appropriately control the flow velocity of the exhaust gas and improve the dust collection efficiency by the dust collector.

It is preferable that the shielding plate has a rectifying portion in which a plurality of ventilation holes are formed in a region other than the shielding portion. As described above, when the shielding plate has a rectifying portion in which a plurality of ventilation holes are formed in a region other than the shielding portion, the exhaust gas introduced into the expanded flow path can be rectified more appropriately. ..

It is preferable that the perforated plate arranged in the expanded flow path is further provided, and the perforated plate is provided on the upstream side of the shielding plate in the flow direction of the exhaust gas. As described above, the perforated plate arranged in the expanded flow path is further provided, and the perforated plate is provided on the upstream side of the shielding plate in the flow direction of the exhaust gas, so that after rectification by the perforated plate. Exhaust gas can be introduced into the shielding plate. Thereby, the flow velocity of the exhaust gas in the dust collecting portion can be easily controlled by the shielding plate.

It is preferable that the expansion flow path extends in the horizontal direction, and the shielding portion is provided above the expansion flow path. In the electrostatic precipitator, since the shielding plate has the shielding portion, the exhaust gas that collides with the shielding portion or bypasses the shielding portion can induce a vortex flow on the downstream side of the shielding portion. The residence time of the exhaust gas on the downstream side of the shielding portion can be lengthened. On the other hand, in general, in an electrostatic precipitator, if the flow of exhaust gas passing above the dust collecting portion becomes faster, the dust collecting efficiency in this portion tends to decrease. Therefore, since the shielding portion is provided above the expanded flow path, the residence time of the exhaust gas passing above the dust collecting portion on the downstream side of the shielding portion can be lengthened, and the dust collecting portion can be extended. It is possible to improve the dust collection efficiency by the part.

It is preferable that the shielding plate is arranged at the most downstream portion of the expansion flow path. By arranging the shielding plate at the most downstream portion of the expanded flow path in this way, the flow velocity of the exhaust gas passing through the dust collecting portion can be easily and surely controlled.

It is preferable that the shielding portion does not project at a position overlapping the most upstream portion of the enlarged flow path in the axial view of the enlarged flow path. As described above, since the shielding portion does not project at a position overlapping the uppermost flow portion of the expanded flow path in the axial view of the expanded flow path, the exhaust gas is provided with a sufficient flow rate of the entire exhaust gas. The flow velocity can be easily controlled.

In the present invention, "the flow path area gradually increases along the flow direction of the exhaust gas" means that the flow path area continuously increases along the flow direction of the exhaust gas and one of the flow directions of the exhaust gas. The portion includes a configuration having a region in which the flow path area does not change. "Vertical to the flow direction of the exhaust gas" means that the inclination angle with respect to the flow direction of the exhaust gas is 80 ° or more and 100 ° or less, preferably 85 ° or more and 95 ° or less. The "horizontal direction" refers to a direction based on the state in which the electrostatic precipitator is arranged on a horizontal plane. "Arranged in the most downstream part of the expansion flow path" means that the expansion flow path is arranged in the region on the most downstream side when the expansion flow path is divided into five equal parts in the flow path direction of the exhaust gas, and is preferably arranged in the expansion flow path. Is arranged in the most downstream region when the exhaust gas is divided into 10 equal parts in the direction of the flow path of the exhaust gas.

As described above, the electrostatic precipitator according to one aspect of the present invention can improve the dust collection efficiency by the dust collecting unit by controlling the flow velocity of the exhaust gas at the time of passing through the dust collecting unit.

FIG. 1 is a schematic perspective view showing an electrostatic precipitator according to an embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II of the electrostatic precipitator of FIG. FIG. 3 is an end view of the electrostatic precipitator of FIG. 2 along line III-III. FIG. 4 is a schematic view showing a shielding plate of the electrostatic precipitator of FIG. FIG. 5 is a diagram showing the positional relationship between the inlet side opening of the inlet duct and the shielding portion in the axial view of the enlarged flow path in the electrostatic precipitator of FIG. FIG. 6 is a schematic view showing a perforated plate of the electrostatic precipitator of FIG. FIG. 7 is a contour diagram showing the analysis results of the electrostatic precipitator in the comparative example. FIG. 8 is a contour diagram showing the analysis result of the electrostatic precipitator in the embodiment. FIG. 9 is a diagram showing a gas velocity vector of the electrostatic precipitator in the comparative example. FIG. 10 is a diagram showing a gas velocity vector of the electrostatic precipitator in the embodiment.

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

[Electrostatic precipitator]
The electrostatic precipitator 1 of FIGS. 1 to 3 includes an inlet duct 2 and a dust collecting unit 3 into which the exhaust gas G1 is introduced through the inlet duct 2. Further, the electrostatic precipitator 1 is provided at an outlet duct 4 into which the exhaust gas G2 that has passed through the dust collecting unit 3 is introduced, and below the dust collecting unit 3, and collects dust (dust) contained in the exhaust gas G1. The hopper 5 is provided. The electrostatic precipitator 1 is configured to introduce the exhaust gas G1 containing dust from the inlet duct 2, remove the dust by the dust collecting unit 3, and then discharge the exhaust gas G2 after removing the dust from the outlet duct 4. There is. The inlet duct 2, the dust collector 3, and the outlet duct 4 are connected in this order from one side to the other in the horizontal direction. That is, the electrostatic precipitator 1 is configured to remove the dust and then discharge the exhaust gas G1 introduced from one side in the horizontal direction from the other side in the horizontal direction.

As shown in FIGS. 2 and 3, in the electrostatic precipitator 1, an enlarged flow path X whose flow path area gradually increases along the flow direction of the exhaust gas G1 is defined on the inner peripheral surface of the inlet duct 2. .. A shielding plate 10 perpendicular to the flow direction of the exhaust gas G1 is arranged in the expansion flow path X. Further, in the expansion flow path X, in addition to the shielding plate 10, a perforated plate 11 perpendicular to the flow direction of the exhaust gas G1 is arranged. As shown in FIGS. 4 and 5, the shielding plate 10 has a shielding portion 10a in a region located outside the most upstream portion of the expanding flow path X in the axial view of the expansion flow path X.

(Inlet duct)
The inlet duct 2 has an inlet side opening 2a into which the exhaust gas G1 is introduced and an outlet side opening 2b into which the exhaust gas G1 is discharged. The expansion flow path X is formed between the entrance side opening 2a and the exit side opening 2b. More specifically, the entrance side opening 2a is the upstream end in the flow direction, and the exit side opening 2b is the downstream end in the flow direction. It is formed.

The inner peripheral surface of the inlet duct 2 has an upper surface 2c and a lower surface 2d facing each other in the vertical direction, and a pair of side surfaces 2e facing each other in the left-right direction (horizontal direction). The upper surface 2c and the lower surface 2d are inclined in a direction away from each other along the flow direction of the exhaust gas G1. That is, the upper surface 2c is inclined upward along the flow direction of the exhaust gas G1, and the lower surface 2d is inclined downward along the flow direction of the exhaust gas G1. Further, the pair of side surfaces 2e are inclined in a direction away from each other along the flow direction of the exhaust gas G1. As a result, the expanded flow path X has a rectangular cross section in the axial direction. More specifically, the enlarged flow path X is formed as a substantially truncated square pyramid whose height direction is the flow direction of the exhaust gas G1 as a whole.

The expansion flow path X extends in the horizontal direction. In other words, the expansion flow path X projects in the horizontal direction from the introduction port of the exhaust gas G1 in the dust collecting unit 3.

(Dust collector)
The dust collecting unit 3 has a casing 12, a plurality of dust collecting plates 13 arranged in the casing 12, and a plurality of discharging electrodes 14 arranged at intervals from the plurality of dust collecting plates 13. The casing 12 defines a substantially square columnar internal space whose axial direction is the horizontal direction.

The plurality of dust collecting plates 13 are arranged parallel to the flow direction and the vertical direction of the exhaust gas G1. As shown in FIG. 3, the plurality of dust collecting plates 13 are arranged in parallel in the width direction of the dust collecting unit 3. Further, as shown in FIGS. 2 and 3, the plurality of dust collecting plates 13 are arranged at intervals in the axial direction of the dust collecting portion 3. As a result, the plurality of dust collecting plates 13 are arranged in a matrix as a whole, with the width direction of the dust collecting unit 3 as the row direction and the axial direction of the dust collecting unit 3 as the column direction. The number of dust collecting plates 13 in each row is not particularly limited, and may be, for example, about 20 or more and 100 or less.

The plurality of emission electrodes 14 are arranged between the dust collecting plates 13 adjacent to each other in each row. The number of the emission electrodes 14 arranged between the pair of adjacent dust collecting plates 13 is not particularly limited, and may be, for example, about 10 or more and 50 or less.

The dust collecting unit 3 removes dust contained in the exhaust gas G1 that has passed through the expansion flow path X. When a high voltage is applied to the discharge electrode 14, the dust collector 3 generates a corona discharge from the discharge electrode 14. In this state, when the exhaust gas G1 passes through the dust collecting portion 3, the dust in the exhaust gas G1 is charged, and the charged dust moves toward the dust collecting plate 13 by the Coulomb force while accompanied by an electrostatic agglomeration action. It adheres to the dust collecting plate 13. As a result, the dust contained in the exhaust gas G1 is collected by the dust collecting plate 13. As a result, the exhaust gas G2 from which the dust has been removed is discharged from the dust collecting unit 3.

(hopper)
The hopper 5 is continuously provided from the bottom of the casing 12. The hopper 5 collects the dust collected on the plurality of dust collecting plates 13. Specifically, in a state where dust is collected on the plurality of dust collecting plates 13, by applying vibration or the like to the plurality of dust collecting plates 13, dust falls from these dust collecting plates 13 and becomes the hopper 5. Collected.

(Shield)
As shown in FIGS. 4 and 5, the shielding plate 10 has a substantially rectangular shape having an upper edge 10b and a lower edge 10c facing each other in the vertical direction and a pair of side edges 10d facing each other in the left-right direction. The shielding plate 10 has the above-mentioned shielding portion 10a and a rectifying portion 10e provided in a region other than the shielding portion 10a. More specifically, the shielding plate 10 includes a shielding portion 10a and a rectifying portion 10e. The upper edge 10b of the shielding plate 10 constitutes the upper edge of the shielding portion 10a. The rectifying unit 10e has a plurality of ventilation holes 10f. The plurality of ventilation holes 10f are arranged in a grid dot shape, for example, and are arranged in a square grid dot shape in FIGS. 4 and 5.

The shielding portion 10a is a solid portion having no pores. The shielding portion 10a is provided at a position continuous with the outer edge of the expansion flow path X. The shielding portion 10a is provided along the outer edge of the expansion flow path X, and more specifically, is provided above the expansion flow path X. The shielding portion 10a has a strip shape with the left-right direction as the longitudinal direction. The shielding portion 10a extends in the left-right direction with the upper edge 10b of the shielding plate 10 as one end in the width direction. The shielding portion 10a preferably crosses the shielding plate 10 in the left-right direction so as to reach the pair of left and right side edges 10d of the shielding plate 10.

The width W of the shielding portion 10a may change over the longitudinal direction of the shielding portion 10a. However, the width W of the shielding portion 10a may be uniform over the longitudinal direction of the shielding portion 10a from the viewpoint that the flow of the exhaust gas G1 discharged to the dust collecting portion 3 can be easily controlled uniformly. In addition, "the width of the shielding portion is uniform over the longitudinal direction" means that the ratio of the minimum width to the maximum width of the shielding portion in the longitudinal direction is 0.8 or more and 1.0 or less, preferably. It means that it is 0.9 or more and 1.0 or less, more preferably 0.95 or more and 1.0 or less.

[Flow velocity control function]
The flow velocity control function of the exhaust gas G1 by the shielding portion 10a will be described. In the electrostatic precipitator 1, a part of the exhaust gas G1 introduced from the inlet side opening 2a of the inlet duct 2 and flowing in the axial direction of the expansion flow path X collides with the rectifying portion 10e of the shielding plate 10 and vertically. It is bent and slows down. On the other hand, even if the exhaust gas G1 introduced from the inlet side opening 2a of the inlet duct 2 and flowing along the inner peripheral surface of the inlet duct 2 collides with the rectifying unit 10e, it is introduced into the dust collecting unit 3 and then the casing 12 Since it flows along the inner peripheral surface of, the flow tends to be faster than other parts.

At this time, the exhaust gas G1 introduced into the dust collecting portion 3 along the side surface 2e of the inlet duct 2 flows between the dust collecting plates 13 arranged on both sides in the width direction of the dust collecting portion 3, so that the flow becomes faster. However, dust is relatively easily collected by the dust collecting plate 13.

Further, the exhaust gas G1 introduced into the dust collecting portion 3 along the lower surface 2d of the inlet duct 2 is likely to be introduced into the hopper 5 continuous from the bottom of the casing 12. Therefore, the dust contained in the exhaust gas G1 is likely to be collected directly in the hopper 5 even if the flow of the exhaust gas G1 becomes faster, which leads to a decrease in the dust collection efficiency of the electrostatic precipitator 1 as a whole. hard.

On the other hand, the exhaust gas G1 introduced into the dust collecting portion 3 along the upper surface 2c of the inlet duct 2 flows at a high speed in the axial direction of the casing 12 along the upper surface of the casing 12. As a result, the exhaust gas G1 easily moves at a position away from the collection area of the dust collection plate 13 at high speed, which tends to lead to a decrease in the dust collection efficiency of the electrostatic precipitator 1.

On the other hand, in the electrostatic precipitator 1, since the shielding plate 10 has the shielding portion 10a, the exhaust gas G1 that collides with the shielding portion 10a or bypasses the shielding portion 10a induces a vortex flow on the downstream side of the shielding portion 10a. can do. As a result, the electrostatic precipitator 1 can retain the exhaust gas G1 which is likely to pass through the dust collecting unit 3 at high speed on the downstream side of the shielding unit 10a.

In the electrostatic precipitator 1, since the shielding portion 10a is provided above the expansion flow path X, the exhaust gas G1 passing above the inside of the dust collecting portion 3 can be retained on the downstream side of the shielding portion 10a. .. As a result, the exhaust gas G1 can be easily collected by the plurality of dust collecting plates 13. Therefore, the electrostatic precipitator 1 can improve the dust collecting efficiency by the dust collecting unit 3. In particular, in the electrostatic precipitator 1, since the shielding portion 10a is provided only on the upper part of the expansion flow path X, the eddy current of the exhaust gas G1 can be induced only in the portion particularly necessary for improving the dust collection efficiency. It is possible to improve both the dust collection efficiency by the dust collecting unit 3 and the processing capacity of the entire electrostatic precipitator 1.

Further, in the electrostatic precipitator 1, since the shielding plate 10 has the rectifying unit 10e in addition to the shielding unit 10a, the flow velocity of the exhaust gas G1 colliding with the rectifying unit 10e can be reduced. As a result, the exhaust gas G1 introduced into the expansion flow path X can be rectified more appropriately. Further, by providing both the vortex inducing function and the rectifying function in one shielding plate 10, the number of parts of the electrostatic precipitator 1 can be reduced, and the entire device can be simplified and the cost can be reduced. can.

The shielding plate 10 is preferably arranged at the most downstream portion of the expansion flow path X. According to this configuration, the exhaust gas G1 that collides with the shielding portion 10a or bypasses the shielding portion 10a tends to induce a vortex flow in the dust collecting portion 3. As a result, the flow velocity of the exhaust gas G1 passing through the dust collecting unit 3 can be easily and surely controlled. Further, according to this configuration, the dust contained in the stagnant exhaust gas G1 can be easily collected by the dust collecting plate 13 arranged on the inlet side of the dust collecting unit 3.

As shown in FIG. 5, it is preferable that the shielding portion 10a does not project at a position overlapping the most upstream portion (entry side opening 2a) of the enlarged flow path X in the axial view of the enlarged flow path X. In other words, in the axial view of the enlarged flow path X, it is preferable that the shielding portion 10a does not exist at a position overlapping the entrance side opening of the enlarged flow path X. According to this configuration, the flow velocity of the exhaust gas G1 can be easily controlled within a desired range while sufficiently securing the flow rate of the entire exhaust gas G1.

(Perforated plate)
As shown in FIGS. 2 and 3, the perforated plate 11 is provided on the upstream side of the shielding plate 10 in the flow direction of the exhaust gas G1. In the present embodiment, the electrostatic precipitator 1 has one perforated plate 11. The number of the perforated plates 11 in the electrostatic precipitator 1 is not particularly limited, and for example, two or more perforated plates 11 may be provided. However, even when the electrostatic precipitator 1 has a plurality of perforated plates 11, it is preferable that all the perforated plates 11 are provided on the upstream side of the shielding plate 10 in the flow direction of the exhaust gas G1. That is, it is preferable that the perforated plate 11 does not exist on the downstream side in the flow direction of the exhaust gas G1 with respect to the shielding plate 10. In the electrostatic precipitator 1, the perforated plate 11 is provided on the upstream side of the shielding plate 10 in the flow direction of the exhaust gas G1, so that the exhaust gas G1 after being rectified by the perforated plate 11 is introduced into the shielding plate 10. be able to. Thereby, the flow velocity of the exhaust gas in the dust collecting unit 3 can be easily controlled by the shielding plate 10. That is, the flow velocity of the exhaust gas G1 in the expansion flow path X can be made uniform by the perforated plate 11, and then the flow velocity of the exhaust gas G1 in the dust collecting portion 3 can be easily controlled by the shielding plate 10.

As shown in FIG. 6, the perforated plate 11 has a substantially rectangular shape having an upper edge 11a and a lower edge 11b facing each other in the vertical direction and a pair of side edges 11c facing each other in the horizontal direction. The perforated plate 11 has a plurality of ventilation holes 11d. In the present embodiment, the plurality of ventilation holes 11d are arranged in a grid pattern over the entire surface of the perforated plate 11. However, the arrangement, number, size, etc. of the plurality of ventilation holes 11d are not particularly limited, and can be appropriately set so that the flow velocity of the exhaust gas G1 in the expansion flow path X can be made uniform. Further, the perforated plate 11 may have a rectifying plate or the like protruding from the outer edge of the plurality of ventilation holes 11d in the flow direction of the exhaust gas G1.

(Exit duct)
The outlet duct 4 has an inlet side opening into which the exhaust gas G2 discharged from the dust collecting portion 3 from which dust is removed is introduced, and an outlet side opening into which the exhaust gas G2 is discharged. An exhaust flow path for exhaust gas G2 is formed between the entrance side opening and the exit side opening. The discharge flow path is provided in a tapered shape in which the flow path area is reduced from the entrance side opening to the exit side opening. As shown in FIGS. 2 and 3, a perforated plate 15 may be provided in the discharge flow path.

<Advantage>
In the electrostatic precipitator 1, since the shielding plate 10 has the shielding portion 10a at the peripheral edge of the expansion flow path X, the flow velocity of the exhaust gas G1 introduced into the dust collecting portion 3 is partially increased. It can be suppressed. Therefore, the electrostatic precipitator 1 can appropriately control the flow velocity of the exhaust gas G1 and improve the dust collection efficiency by the dust collector 3.

[Other Embodiments]
The above embodiment does not limit the configuration of the present invention. Therefore, in the above-described embodiment, the components of each part of the above-described embodiment can be omitted, replaced or added based on the description of the present specification and common general technical knowledge, and all of them are construed as belonging to the scope of the present invention. Should be.

For example, the shielding portion may project to a position where it overlaps with the most upstream portion of the enlarged flow path in the axial view of the enlarged flow path. In this case, it is preferable that the shielding portion does not overlap with the region of 1/2 or more of the entrance side opening of the enlarged flow path. If the overlapping ratio of the shielding portion and the entrance side opening becomes large, the flow rate of the exhaust gas in the expanding flow path may decrease, and the processing capacity of the entire electrostatic precipitator may become insufficient.

The shielding plate may be configured not to have the rectifying unit. For example, the shielding plate may be composed of only the shielding portion. In this case, the shielding plate is arranged so as to block only a part of the enlarged flow path in the axial direction of the enlarged flow path.

The electrostatic precipitator is described, for example, when the flow velocity of the exhaust gas in the expansion flow path is substantially uniform, or when the flow velocity of the exhaust gas in the expansion flow path can be sufficiently adjusted by the rectifying portion of the shielding plate. It is not necessary to have a perforated plate in the expansion flow path.

The shielding portion can be arranged according to the arrangement of the dust collecting plate in the dust collecting portion, the shape of the casing, and the like. Therefore, depending on the specific configuration of the dust collecting portion, the shielding portion may be provided in a portion other than the upper portion of the expanded flow path.

The shielding plate can be arranged at a position other than the most downstream portion of the expanded flow path if the flow velocity of the exhaust gas passing through the dust collecting portion can be appropriately controlled.

Hereinafter, the present invention will be described in more detail with respect to Examples, but the present invention is not limited to these Examples.

A numerical fluid simulation was carried out in order to verify the flow velocity control effect exerted by the shielding plate provided in the electrostatic precipitator. In this simulation, as shown in FIG. 7, a model (comparative example) in which two perforated plates 11 are arranged in the enlarged flow path, and as shown in FIG. 8, the perforated plate 11 and the shielding plate 10 are gasified in the enlarged flow path. It was compared with the model (Example) arranged in this order in the flow direction of. In this comparative example and this embodiment, only one division in which the expansion flow path is divided into two in the left-right direction along the axial direction is modeled. 7 and 8 are contour diagrams (contour diagrams) of the downstream component of the gas velocity in the flow direction obtained from the analysis result by the numerical fluid simulation. The second perforated plate 11 in the comparative example and the shielding plate 10 in the example were arranged at the most downstream portion of the expansion flow path. The perforated plate 11 has the configuration shown in FIG. 6 in which a plurality of ventilation holes are arranged in a square lattice dot shape over the entire surface in both Comparative Examples and Examples. Further, the shielding plate 10 has a configuration of FIG. 4 in which a band-shaped shielding portion 10a is provided on the upper portion, and other than the shielding portion 10a is formed as a rectifying portion 10e having a plurality of ventilation holes similar to the perforated plate 11. In the axial view of the enlarged flow path, the shielding portion 10a is configured so as not to protrude at a position overlapping the most upstream portion of the enlarged flow path. Specifically, the ratio of the width W (length in the vertical direction) of the shielding portion 10a to the distance D between the most upstream portion and the most downstream portion of the enlarged flow path in the axial view of the enlarged flow path was set to 0.853. ..

The electrostatic precipitators of Comparative Examples and Examples had the same configuration except for the difference between the perforated plate and the shielding plate arranged at the most downstream part of the expansion flow path. The dust collecting unit has a configuration in which a plurality of dust collecting plates and a plurality of discharging electrodes are arranged in a casing. The plurality of dust collecting plates were arranged in parallel in the width direction of the dust collecting portion and arranged at intervals in the axial direction of the dust collecting portion. The plurality of emission electrodes were arranged between adjacent dust collecting plates in each row. The detailed shape of the unmodeled dust collecting plate and the pressure loss due to the discharge electrode were separately given as an external force. The κ-ω model was used as the turbulence model, and the working gas was air (operating temperature, pressure).

As shown in FIG. 7, in the comparative example in which the shielding plate 10 is not used, a region (high-speed region) having a large gas flow velocity is formed in the upper part of the dust collecting portion on the gas introduction side. The velocity vector of the gas in the high speed region of FIG. 7 is shown in FIG. As shown in FIG. 9, in the comparative example, the gas flow is diffused above the expansion flow path by the rectifying effect of the perforated plate 11, and this gas flows along the inner surface of the casing of the dust collecting portion to create a high-speed region. It can be seen that it is formed.

On the other hand, as shown in FIG. 8, in the embodiment using the shielding plate 10, the high-speed region is not formed in the upper part of the dust collecting portion on the gas introduction side. The velocity vector of the gas in the example is shown in FIG. As shown in FIG. 10, in the embodiment, the gas that collides with the shielding portion 10a or bypasses the shielding portion 10a forms a vortex on the downstream side of the shielding portion 10a, so that the residence time of the gas is increased. I understand.

As described above, the electrostatic precipitator according to one aspect of the present invention is used to remove dust contained in exhaust gas in a business establishment using a coal-fueled heat supply system such as a thermal power plant or a steel mill. It is preferably used. For example, the exhaust gas generated at a power plant may contain unburned carbon. If this unburned carbon cannot be sufficiently collected by the electrostatic precipitator, the gypsum will turn black when the exhaust gas after dust collection is desulfurized by, for example, a wet desulfurization device using the lime-gypsum method in the subsequent stage. May cause a phenomenon. On the other hand, by using the electrostatic precipitator, unburned carbon can be sufficiently collected, and the occurrence of the gypsum blackening phenomenon can be suppressed.

1 Electrostatic precipitator 2 Inlet duct 2a Inlet side opening 2b Outer side opening 2c Top surface 2d Bottom surface 2e Side surface 3 Dust collector 4 Outlet duct 5 Hopper 10 Shielding plate 10a Shielding part 10b, 11a Upper edge 10c, 11b Lower edge 10d, 11c Side edge 10e Rectifying part 10f, 11d Ventilation holes 11, 15 Perforated plate 12 Casing 13 Dust collecting plate 14 Discharge electrode G1, G2 Exhaust gas X Expanded flow path D Distance from the downstream part W Width of the shield part

Claims (6)

An electrostatic precipitator including an inlet duct and a dust collector in which exhaust gas is introduced through the inlet duct.
On the inner peripheral surface of the inlet duct, an enlarged flow path in which the flow path area gradually increases along the flow direction of the exhaust gas is defined.
The expanded flow path is provided with a shielding plate perpendicular to the flow direction of the exhaust gas.
An electrostatic precipitator in which the shielding plate has a shielding portion in a region located outside the most upstream portion of the enlarged flow path in an axial view of the enlarged flow path. The electrostatic dust collector according to claim 1, wherein the shielding plate has a rectifying portion in which a plurality of ventilation holes are formed in a region other than the shielding portion. Further provided with a perforated plate arranged in the enlarged flow path,
The electrostatic precipitator according to claim 1 or 2, wherein the perforated plate is provided on the upstream side of the shielding plate in the flow direction of the exhaust gas. The expansion flow path extends in the horizontal direction,
The electrostatic precipitator according to claim 1, claim 2 or claim 3, wherein the shielding portion is provided above the expansion flow path. The electrostatic precipitator according to any one of claims 1 to 4, wherein the shielding plate is arranged at the most downstream portion of the expansion flow path. The electrostatic precipitator according to any one of claims 1 to 5, wherein the shielding portion does not project at a position where it overlaps with the most upstream portion of the enlarged flow path in the axial view of the enlarged flow path.

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