Dust collecting apparatus

Abstract

To improve collection efficiency of fine particles contained in exhaust gas.SOLUTION: A dust collecting apparatus includes: a casing in which an exhaust gas flow path through which exhaust gas flows upward in a vertical direction is formed; a droplet supply unit which is disposed in the exhaust gas flow path and supplies droplets having a temperature lower than that of the exhaust gas upward in the vertical direction; a charging unit which is disposed in the exhaust gas flow path above the droplet supply unit in the vertical direction, formed in a ring shape, and charges the droplets that have passed through an interior thereof; and a dust collecting unit which is disposed in the exhaust gas flow path above the charging unit in the vertical direction in a grounded state and collects fine particles contained in the exhaust gas and the droplets.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a dust collection device. [Background technology]

[0002] In power plants that burn fossil fuels and waste treatment plants that burn garbage, dust collection systems that capture fine particles contained in exhaust gases are installed as exhaust gas treatment devices. Dust collection systems include electrostatic precipitators that form an electric field in the exhaust gas passage and collect charged fine particles by attaching them to electrodes, wet dust collectors that inject liquid droplets into the exhaust gas and collect the fine particles with the liquid droplets, and cyclone dust collectors that rotate the exhaust gas and separate the fine particles by centrifugal separation.

[0003] For example, Patent Document 1 describes an apparatus in which exhaust gas is denitrified using a corona discharge reaction tube and then supplied to a gas absorption tower to remove harmful gases and soot contained in the exhaust gas. Furthermore, in the gas absorption tower of Patent Document 1, a high-voltage electrode and a ground electrode are provided in the packed bed, and a high DC voltage is applied between the two electrodes. This electrode configuration imparts an electric charge to solid particles flowing into the gas absorption tower, and the capture of the particles is promoted by the electric field applied to the gas absorption tower, thereby improving the absorption performance of the packed bed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-229418 Summary of the Invention [Problem to be solved by the invention]

[0005] In a gas absorption tower configured as described in Patent Document 1, the exhaust gas supplied into the tower is mixed with a cleaning solution sprayed from a cleaning solution spray nozzle and collides with a packed bed to which an electric field is applied. However, if the particulate matter contained in the exhaust gas is in the form of a fine mist, the dust collection effect of the dust collection unit, such as a packing, demister, or filter, may not be sufficient. Therefore, it is desirable to improve the recovery efficiency of the particulate matter contained in the exhaust gas.

[0006] The present disclosure has been made to address the above-mentioned needs, and has an object to provide a dust collecting device that can improve the efficiency of collecting fine particles contained in exhaust gas. [Means for solving the problem]

[0007] In order to solve the above problems, the dust collecting device according to the present disclosure includes a casing having an exhaust gas flow path formed therein through which exhaust gas flows vertically upward, a droplet supply unit disposed in the exhaust gas flow path and supplying droplets having a temperature lower than that of the exhaust gas vertically upward, a ring-shaped charging unit disposed in the exhaust gas flow path vertically above the droplet supply unit and charging the droplets that pass through the charging unit, and a dust collecting unit disposed in the exhaust gas flow path vertically above the charging unit and in a grounded state, for collecting fine particles and the droplets contained in the exhaust gas. [Effects of the Invention]

[0008] According to the dust collecting device of the present disclosure, it is possible to improve the efficiency of collecting fine particles contained in exhaust gas. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing a dust collection system according to an embodiment of the present invention; [Figure 2] 1 is a schematic view showing a dust collecting device according to a first embodiment. [Figure 3] 3 is an enlarged view of a main part illustrating the positional relationship between a droplet supply unit, a charging unit, and a dust collection unit according to the embodiment. FIG. [Figure 4] FIG. 4 is a schematic view showing a dust collecting device according to a second embodiment. [Figure 5] FIG. 10 is a schematic view showing a dust collecting device according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of a dust collecting device according to the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to this embodiment.

[0011] First Embodiment (Exhaust gas treatment system) The dust collector in the exhaust gas treatment system will be described as treating exhaust gas discharged from an exhaust gas discharge device, but is not limited to this. The dust collector 2 can be used to collect various fine particles contained in exhaust gas. For example, it can be used as a system for collecting fine particles contained in the air inside a manufacturing plant, or as a system for collecting fine particles, such as dust, from work sites such as demolition work. Furthermore, the fine particles are not limited to solids, and can also be liquids such as droplets or tar.

[0012] In an exhaust gas treatment system 1, various fine particles are collected from exhaust gas discharged from an apparatus using a dust collector 2 and supplied to another apparatus outside the system. As shown in FIG. 1, the exhaust gas treatment system 1 includes an exhaust gas discharge device 10 and a dust collector 2. The exhaust gas discharge device 10 is a device that combusts fossil fuels, waste materials, etc. The exhaust gas discharge device 10 is, for example, a boiler or a gas turbine. The exhaust gas discharge device 10 discharges exhaust gas generated during combustion to the dust collector 2. The heat generated by burning the target in the exhaust gas can be used for power generation or as a heat source. The exhaust gas treatment system 1 may also include an exhaust heat recovery device that recovers heat from the exhaust gas and an exhaust gas treatment device that treats harmful components other than fine particles in the exhaust gas path.

[0013] As shown in FIG. 2, the dust collector 2 collects fine particles contained in the exhaust gas by circulating the exhaust gas therethrough. The fine particles are in the form of a mist with a particle size of 0.5 μm or less. The exhaust gas contains, for example, sulfur trioxide (SO3) as the fine particles. The exhaust gas also contains saturated water vapor and has a temperature of about 20°C to 80°C. The dust collector 2 of this embodiment is configured as, for example, a packed tower or a desulfurization device. The dust collector 2 cools and charges the exhaust gas in one go, and then collects the fine particles. The dust collector 2 includes a casing 21, a droplet supply unit 22, an electrification unit 23, a dust collection unit 24, and a water supply unit 26.

[0014] The casing 21 is a cylindrical container extending in the vertical direction Dv. An exhaust gas flow path is formed inside the casing 21, through which exhaust gas flows upward in the vertical direction Dv. A pipe (not shown) for supplying exhaust gas is connected near the bottom of the casing 21. A pipe (not shown) for discharging gas after particulate matter has been captured is connected near the top of the casing 21. As a result, an exhaust gas flow path is formed inside the casing 21, through which exhaust gas flows from below to above in the vertical direction Dv.

[0015] The droplet supply unit 22 cools the exhaust gas flowing through the exhaust gas flow path and increases the moisture content in the exhaust gas. The droplet supply unit 22 supplies droplets having a lower temperature than the exhaust gas upward in the vertical direction Dv. The droplet supply unit 22 supplies droplets by spraying a liquid having a different component from the sulfur trioxide-containing liquid contained in the exhaust gas. Specifically, the droplet supply unit 22 of this embodiment is capable of ejecting cooling water supplied from the outside as droplets. The supplied cooling water has a temperature of, for example, about 10°C to 30°C.

[0016] Furthermore, the droplet supply unit 22 is arranged in the exhaust gas flow path inside the casing 21. A plurality of droplet supply units 22 are arranged in a horizontal direction perpendicular to the vertical direction Dv. The plurality of droplet supply units 22 are arranged at equal intervals on an imaginary horizontal plane. The droplet supply unit 22 is a spray nozzle or spray gun that is arranged with its injection hole facing upward in the vertical direction Dv and that sprays cooling water in the form of a mist or fine droplets.

[0017] The droplet supply units 22 preferably lower the temperature of the exhaust gas flowing through the exhaust gas flow path by 5°C to 50°C. It is more preferable that the droplet supply units 22 lower the temperature of the gas flowing through the exhaust gas flow path by 5°C to 50°C.

[0018] More specifically, the droplet supply unit 22 preferably injects droplets so that the droplets have an average particle size (for example, median diameter) of 10 μm to 100 μm. Furthermore, the droplet supply unit 22 preferably injects droplets so that the spray angle θ of the droplets shown in FIG. 3 is 30° to 120°. The interval (pitch) between the plurality of droplet supply units 22 on a virtual horizontal plane is preferably 0.2 m to 1.0 m. In addition, the flow rate per unit time [L / min] of the droplets injected from the droplet supply unit 22 and the flow rate per unit time [m 3 / min], the flow rate ratio is 0.2 [L / m 3 ] and ~3.0 [L / m 3 Furthermore, it is preferable that the droplet supply section 22 jets droplets at a speed of 20 [m / s] to 150 [m / s].

[0019] As shown in FIG. 2, the charging unit 23 charges droplets that pass nearby. The charging unit 23 is arranged in the exhaust gas flow path above the droplet supply unit 22 in the vertical direction Dv. The charging unit 23 is arranged apart from the droplet supply unit 22 in the vertical direction Dv. The charging unit 23 is formed in a ring shape. Specifically, the charging unit 23 is a ring-shaped electrode connected to a high-voltage power supply 25. The charging unit 23 is connected to the high-voltage power supply 25 together with the droplet supply unit 22. The charging unit 23 is positively charged with respect to the droplet supply unit 22. The charging unit 23 is also connected to the casing 21 and grounded. The charging units 23 are arranged so that one charging unit corresponds to one droplet supply unit 22. Specifically, the charging units 23 are arranged so that the center of the ring-shaped charging unit 23 coincides with the center of the injection hole of the droplet supply unit 22 when viewed from the vertical direction Dv. This allows most of the droplets ejected from droplet supply unit 22 to pass through the inside of ring-shaped charging unit 23 when viewed from the vertical direction Dv. Then, charging unit 23 charges the droplets that pass through its interior together with the exhaust gas.

[0020] The dust collecting unit 24 collects fine particles and liquid droplets contained in the exhaust gas. The dust collecting unit 24 is grounded and disposed in the exhaust gas flow path within the casing 21 above the charging unit 23 in the vertical direction Dv. The dust collecting unit 24 is disposed away from the charging unit 23 in the vertical direction Dv. The dust collecting unit 24 is disposed in contact with the inner circumferential surface of the casing 21 without any gaps. The dust collecting unit 24 of this embodiment is, for example, a filler that can collect fine particles and liquid droplets by causing gas-liquid contact on its surface within the casing 21. Note that the dust collecting unit 24 is not limited to a filler, and may be any material that can collect fine particles and liquid droplets. Therefore, the dust collecting unit 24 may be a demister or a filter. The dust collecting unit 24 is connected to the casing 21 and is grounded. The dust collecting unit 24 is positively grounded on the positive side with respect to the droplet supply unit 22.

[0021] Furthermore, the dust collection unit 24 is preferably spaced above the droplet supply unit 22 in the vertical direction Dv by a distance such that 90% or more of the fine particles of about 0.5 μm contained in the exhaust gas have a particle size of 2 μm or more. Specifically, as shown in Fig. 3, the dust collection unit 24 is preferably spaced about 0.1 m to 2.0 m from the droplet supply unit 22 in the vertical direction Dv.

[0022] As shown in FIG. 2, the water supply unit 26 supplies liquid to the exhaust gas that has passed through the dust collecting unit 24. The water supply unit 26 supplies the liquid downward in the vertical direction Dv. The water supply unit 26 is arranged in the exhaust gas flow path inside the casing 21 above the dust collecting unit 24 in the vertical direction Dv. The water supply unit 26 is arranged apart from the dust collecting unit 24 in the vertical direction Dv. Therefore, in the exhaust gas flow path inside the casing 21 of the first embodiment, the droplet supply unit 22, the charging unit 23, the dust collecting unit 24, and the water supply unit 26 are arranged in the vertical direction Dv in this order from below in the vertical direction Dv.

[0023] Furthermore, the water supply unit 26 sprays a liquid having a different component from the sulfur trioxide-containing liquid contained in the exhaust gas to supply droplets. Specifically, the water supply unit 26 of this embodiment is capable of ejecting cooling water supplied from an external source as droplets. The cooling water is, for example, about 10°C to 30°C, similar to the cooling water supplied from the droplet supply unit 22. Therefore, the water supply unit 26 cools the exhaust gas that has passed through the dust collection unit 24. A plurality of water supply units 26 are arranged in a horizontal direction perpendicular to the vertical direction Dv. The plurality of water supply units 26 are arranged at equal intervals on an imaginary horizontal plane. The water supply unit 26 is a spray gun similar to the droplet supply unit 22. The water supply unit 26 is arranged with its injection hole facing downward in the vertical direction Dv and sprays the cooling water in the form of a mist or fine droplets. Here, the mist refers to, for example, a state in which the particle diameter of the cooling water is 10 μm or less. Furthermore, the term "fine droplets" refers to a state in which the particle size of the cooling water is 100 μm or less, for example.

[0024] The water supply unit 26 is not limited to a configuration that supplies cooling water. When the dust collector 2 is, for example, an absorption tower, the water supply unit 26 may supply an absorbing liquid that is an aqueous amine solution or a non-aqueous amine liquid that uses a physical absorption solvent instead of water.

[0025] (Example) Next, the results of actually collecting particulates contained in exhaust gas using the dust collector 2 of this embodiment are shown below. In this example, the dust collector 2 is configured under the following conditions.

[0026] Specifically, for example, in the dust collector 2, exhaust gas containing sulfur trioxide particles with an average particle size of 0.5 μm is supplied to the exhaust gas flow path from below (upstream) in the vertical direction Dv relative to the droplet supply unit 22 at 60°C. The droplet supply unit 22 sprays droplets with an average particle size of 75 μm, a spray angle θ of 75°, a pitch of 0.4 m between the droplet supply units 22, a flow rate ratio of 1.4, and an injection speed of the droplets of 30 m / s. The droplet supply unit 22 reduces the temperature of the exhaust gas flowing through the exhaust gas flow path by 15°C. Specifically, the temperature of the exhaust gas is reduced from 60°C to 45°C at a point approximately 500 mm above (downstream) the injection hole of the droplet supply unit 22 in the vertical direction Dv. Furthermore, the distance Dv between the dust collection unit 24 and the droplet supply unit 22 in the vertical direction is set to 1.0 [m].

[0027] In the dust collecting device 2 under these conditions, droplets are supplied from the droplet supply unit 22, and as a result, water vapor condenses, causing particles of 2 μm or less to become coarser in size than 2 μm. In other words, the particle size of particles of about 0.5 μm increases by up to four times.

[0028] (Action and effect) In the dust collecting device 2 of this embodiment, cooling water is sprayed from the droplet supply unit 22 upward in the vertical direction Dv toward the exhaust gas flowing through the exhaust gas flow path. The sprayed cooling water is mixed with the exhaust gas flowing through the exhaust gas flow path. As a result, the high-temperature exhaust gas is cooled, and saturated water vapor in the exhaust gas condenses into liquid containing sulfur trioxide contained in the exhaust gas. As a result, the liquid containing sulfur trioxide contained in the exhaust gas coarsens from a small particle size of 0.5 μm or less to a large particle size. Furthermore, the cooling water in the form of a mist or fine droplets sprayed from the droplet supply unit 22 passes through the ring-shaped charging unit 23 and becomes electrically charged. Since the charging unit 23 is ring-shaped and does not have a discharge needle, the occurrence of corona discharge between the cooling water and the droplet supply unit 22 can be suppressed. Then, the charged cooling water in the form of a mist or fine droplets collides with the coarse liquid containing sulfur trioxide, and the coarse liquid containing sulfur trioxide is absorbed into the large, charged droplets of cooling water. As a result, the sulfur trioxide becomes contained in droplets with very large particle diameters and further coarsens. In this state, the cooling water that has become large droplets containing sulfur trioxide enters the dust collector 24 together with the exhaust gas. As a result, the dust collector 24 can capture most of the fine particles, such as sulfur trioxide, contained in the exhaust gas simply by collecting droplets with large particle diameters that are easy to capture. This improves the efficiency of collecting the fine particles contained in the exhaust gas.

[0029] Furthermore, the droplet supply unit 22 sprays cooling water, which is a liquid with a different composition from the sulfur trioxide-containing liquid contained in the exhaust gas, to supply droplets into the exhaust gas flow path. Therefore, only the sulfur trioxide originally present in the exhaust gas can be coarsened without additionally supplying sulfur trioxide to be removed from the exhaust gas into the exhaust gas flow path. This improves the efficiency of collecting fine particles contained in the exhaust gas.

[0030] Furthermore, a plurality of droplet supply units 22 are arranged in a horizontal direction perpendicular to the vertical direction Dv, and charging units 23 are arranged to correspond to each of the droplet supply units 22. This makes it possible to stably supply charged droplets over a wide range that covers the entire exhaust gas flow path within the casing 21. This makes it possible to uniformly collect fine particles contained in the exhaust gas flowing through the exhaust gas flow path over a wide range of the exhaust gas flow path.

[0031] Second Embodiment Next, a dust collecting device 2A according to a second embodiment of the present disclosure will be described. In the second embodiment described below, components common to the first embodiment will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted. The second embodiment differs from the first embodiment in that it includes a current plate 31.

[0032] In FIG. 4, the dust collecting device 2A is illustrated with the casing 21 and the water supply unit 26 omitted. As shown in FIG. 4, the rectifying vane 31 rectifies an uneven flow of a mixed fluid of gas flowing through the exhaust gas flow path and cooling water supplied from the droplet supply unit 22 and charged by the charging unit 23. The rectifying vane 31 is grounded and disposed between the charging unit 23 and the dust collecting unit 24 in the vertical direction Dv. The rectifying vane 31 is disposed at a position away from both the charging unit 23 and the dust collecting unit 24 in the vertical direction Dv. The rectifying vane 31 is disposed closer to the dust collecting unit 24 than the charging unit 23 in the vertical direction Dv. The rectifying vane 31 has a plurality of through holes 32. The rectifying vane 31 of this embodiment is formed in a plate shape extending perpendicular to the vertical direction Dv. The rectifying vane 31 is disposed in close contact with the inner circumferential surface of the casing 21. The plurality of through holes 32 are formed at equal intervals in a direction perpendicular to the vertical direction Dv. When viewed from the vertical direction Dv, the through holes 32 are formed with a diameter larger than that of the ring-shaped charging portion 23. The restriction ratio of the straightening vane 31 of this embodiment is preferably 0.2 to 0.8. Here, the restriction ratio is the ratio of the throttle area, which is the sum of the opening areas of the plurality of through holes 32, to the flow cross-sectional area of ​​the exhaust gas flow path. The flow cross-sectional area of ​​the exhaust gas flow path of this embodiment is the cross-sectional area in a direction perpendicular to the vertical direction Dv of the casing 21, and is the overall area of ​​the straightening vane 31 when no through holes 32 are formed. Therefore, the restriction ratio is expressed as the throttle area / flow cross-sectional area of ​​the exhaust gas flow path.

[0033] (Action and effect) In this dust collector 2A, the cooling water droplets sprayed from the droplet supply unit 22 and charged by the charging unit 23 pass through the multiple through-holes 32 in the straightening plate 31. At this time, the spray and the exhaust gas containing sulfur trioxide around the spray are gathered toward the through-holes 32 in the straightening plate 31 and mixed there. This increases the chance of the droplets and sulfur trioxide colliding with each other. As a result, a large amount of cooling water containing sulfur trioxide with large particle diameters flows into the dust collecting unit 24, which increases the efficiency of capturing sulfur trioxide particulates. This further improves the efficiency of collecting particulates contained in the exhaust gas.

[0034] Third Embodiment Next, a dust collecting device 2B according to a third embodiment of the present disclosure will be described. In the third embodiment described below, components common to the first and second embodiments will be denoted by the same reference numerals in the drawings, and descriptions thereof will be omitted. The third embodiment differs from the other embodiments in that it includes a heating unit 41, an upper droplet supply unit 42, and an upper charging unit 43.

[0035] The dust collector 2B of the third embodiment reheats and cools the exhaust gas once cooled, and then collects the particulates. As shown in Fig. 5, the dust collector 2B of the third embodiment includes a casing 21, a droplet supply unit 22, a charging unit 23, a dust collection unit 24, a water supply unit 26, a heating unit 41, an upper droplet supply unit 42, and an upper charging unit 43.

[0036] The heating unit 41 heats the exhaust gas that has passed through the electrification unit 23. The heating unit 41 of this embodiment heats the exhaust gas so as to raise its temperature to approximately 40°C to 80°C. The heating unit 41 supplies liquid or steam that is at a higher temperature than the exhaust gas and droplets, in a direction opposite to the flow of the fluid flowing through the exhaust gas flow path. In other words, the heating unit 41 supplies liquid supplied from the outside downward in the vertical direction Dv. The heating unit 41 sprays liquid of a different composition from the liquid containing sulfur trioxide contained in the exhaust gas. The heating unit 41 of this embodiment is capable of ejecting high-temperature water supplied from the outside as droplets or steam. In addition to spraying in the direction opposite to the flow of exhaust gas, the heating unit 41 may also spray in the same direction as the exhaust gas.

[0037] Furthermore, the heating unit 41 is disposed in the exhaust gas flow path within the casing 21 above the charging unit 23 in the vertical direction Dv. The heating unit 41 is disposed at a distance from the charging unit 23 in the vertical direction Dv. The heating unit 41 is disposed above the droplet supply unit 22 in the vertical direction Dv approximately twice the distance between the liquid supply unit and the dust collection unit 24 in the first and second embodiments. Specifically, the heating unit 41 is disposed above the droplet supply unit 22 in the vertical direction Dv by at least one but not more than five times that distance. Furthermore, in the vertical direction Dv, nothing but the charging unit 23 is disposed between the heating unit 41 and the droplet supply unit 22. In other words, a space is formed between the heating unit 41 and the droplet supply unit 22 in the vertical direction Dv in which the exhaust gas, cooled droplets, and a fluid such as high-temperature water can be sufficiently mixed.

[0038] Furthermore, a plurality of heating units 41 are arranged in a horizontal direction perpendicular to the vertical direction Dv. The plurality of heating units 41 are arranged at equal intervals on an imaginary horizontal plane. The heating units 41 are arranged with their injection holes facing downward in the vertical direction Dv, and inject high-temperature water in the form of a mist or fine droplets.

[0039] The upper droplet supply unit 42 cools the exhaust gas heated by the heating unit 41 and flowing through the exhaust gas flow path, and increases the amount of condensed water in the exhaust gas. The upper droplet supply unit 42 supplies droplets having a temperature lower than that of the exhaust gas upward in the vertical direction Dv. The upper droplet supply unit 42 supplies droplets by spraying a liquid having a different component from the sulfur trioxide-containing liquid contained in the exhaust gas. Specifically, the upper droplet supply unit 42 of this embodiment is capable of ejecting cooling water supplied from the outside as droplets, similar to the droplet supply unit 22. The supplied cooling water has a temperature of, for example, about 10°C to 30°C, similar to the droplet supply unit 22.

[0040] The upper droplet supply unit 42 is disposed in the exhaust gas flow path inside the casing 21. The upper droplet supply unit 42 is disposed in the exhaust gas flow path above the heating unit 41 in the vertical direction Dv. The upper droplet supply unit 42 of this embodiment is preferably disposed as close as possible to the heating unit 41. Therefore, the upper droplet supply unit 42 is preferably disposed above the heating unit 41 in the vertical direction Dv so as to be adjacent to the heating unit 41.

[0041] Furthermore, a plurality of upper droplet supply units 42 (for example, the same number as the droplet supply units 22) are arranged in a horizontal direction perpendicular to the vertical direction Dv. The plurality of upper droplet supply units 42 are arranged at equal intervals on an imaginary horizontal plane. The upper droplet supply units 42 are arranged with their injection holes facing upward in the vertical direction Dv, and inject the cooling water in the form of a mist or fine droplets.

[0042] The multiple upper droplet supply units 42 preferably lower the temperature of the exhaust gas flowing through the exhaust gas flow path by 5°C to 30°C, similar to the droplet supply unit 22. The upper droplet supply units 42 are formed in the same configuration as the droplet supply unit 22 so that they can supply droplets under the same conditions as the droplet supply unit 22.

[0043] The upper charging unit 43 charges droplets that pass nearby. The upper charging unit 43 is disposed in the exhaust gas flow path above the upper droplet supply unit 42 in the vertical direction Dv. The upper charging unit 43 is disposed apart from the upper droplet supply unit 42 in the vertical direction Dv. The upper charging unit 43 has the same configuration as the charging unit 23. That is, the upper charging unit 43 is formed in a ring shape. Specifically, the upper charging unit 43 is a ring-shaped electrode connected to a high-voltage power supply 45 (upper high-voltage power supply) that is separate from the high-voltage power supply 25 (lower high-voltage power supply) connected to the charging unit 23. The upper charging unit 43 is connected to the high-voltage power supplies 25 and 45 together with the upper droplet supply unit 42. The upper charging unit 43 is positively charged relative to the upper droplet supply unit 42. The upper charging unit 43 is also connected to the casing 21 and is grounded. The upper droplet supply unit 42 is given a negative potential difference with respect to the high-voltage power supply 45 and the ground electrode. The upper charging unit 43 is arranged so that one corresponds to one upper droplet supply unit 42. Specifically, the upper charging unit 43 is arranged so that the center of the ring-shaped upper charging unit 43 coincides with the center of the injection hole of the upper droplet supply unit 42 when viewed from the vertical direction Dv. This allows most of the droplets injected from the upper droplet supply unit 42 to pass through the inside of the ring-shaped upper charging unit 43 when viewed from the vertical direction Dv. The upper charging unit 43 then charges the droplets that pass through its interior, along with the liquid component containing sulfur trioxide in the exhaust gas.

[0044] The dust collecting unit 24 of the third embodiment is grounded and disposed in the exhaust gas flow path inside the casing 21 above the upper charging unit 43 in the vertical direction Dv. The dust collecting unit 24 is disposed away from the upper charging unit 43 in the vertical direction Dv. That is, in the exhaust gas flow path inside the casing 21 of the third embodiment, the droplet supply unit 22, the charging unit 23, the heating unit 41, the upper droplet supply unit 42, the upper charging unit 43, the dust collecting unit 24, and the water supply unit 26 are disposed in this order from bottom to top in the vertical direction Dv.

[0045] (Action and effect) In this dust collector 2B, high-temperature water or water vapor is supplied from the heating unit 41 to the cooling water and exhaust gas that have been sprayed from the droplet supply unit 22 and charged by the charging unit 23. As a result, the droplets and exhaust gas flowing through the exhaust gas flow path are heated. That is, the exhaust gas that has been cooled by the cooling water supplied from the droplet supply unit 22 is heated by the heating unit 41. As a result, some of the droplets in the low-temperature exhaust gas evaporate, increasing the amount of water vapor in the exhaust gas. Then, cooling water is sprayed from the upper droplet supply unit 42 upward in the vertical direction Dv toward the heated cooling water and exhaust gas. The sprayed cooling water is mixed with the droplets and exhaust gas flowing through the exhaust gas flow path. As a result, the high-temperature exhaust gas and water vapor heated by the heating unit 41 are cooled again, and the water vapor contained in the exhaust gas condenses into a liquid component containing sulfur trioxide. Therefore, the liquid containing sulfur trioxide in the exhaust gas is condensed once in the droplet supply unit 22 and then re-condensed in the upper droplet supply unit 42. As a result, the liquid containing sulfur trioxide becomes coarse and its particle size becomes very large. In addition, the cooling water sprayed from the upper droplet supply unit 42 passes through the ring-shaped upper charging unit 43 and is further charged. Then, the charged cooling water in droplet form collides with the very coarse liquid containing sulfur trioxide, and the coarse liquid containing sulfur trioxide is absorbed into the charged droplets. As a result, the sulfur trioxide is contained in the cooling water with very large particle size, and becomes even coarser. Therefore, the particle size of the large droplets containing sulfur trioxide can be significantly larger than when cooling and charging are performed only once. In this state, the cooling water in the form of large droplets containing sulfur trioxide enters the dust collection unit 24. As a result, the dust collection unit 24 can capture fine particles such as sulfur trioxide contained in the exhaust gas simply by collecting cooling water particles with very large particle diameters that are easy to collect, thereby further improving the efficiency of collecting fine particles contained in the exhaust gas.

[0046] The heating unit 41 also sprays water at a higher temperature than the exhaust gas that has passed through the charging unit 23 downward in the vertical direction Dv. This allows high-temperature water to be supplied so that it comes into counterflow contact with the cooling water and exhaust gas that have been cooled and charged. This allows the cooling water droplets and exhaust gas flowing through the exhaust gas flow path to be efficiently heated. As a result, the amount of water vapor in the exhaust gas can be increased.

[0047] Furthermore, a plurality of heating units 41 and upper droplet supply units 42 are arranged in a horizontal direction perpendicular to the vertical direction Dv, and an upper charging unit 43 is arranged to correspond to each of the upper droplet supply units 42. This makes it possible to stably supply heated, re-cooled, and charged droplets over a wide range that covers the entire exhaust gas flow path within the casing 21. This makes it possible to uniformly collect fine particles contained in the exhaust gas flowing through the exhaust gas flow path over a wide range of the exhaust gas flow path.

[0048] (Other embodiments) The above describes in detail the embodiments of the present disclosure with reference to the drawings, but the specific configuration is not limited to this embodiment, and design changes and the like are also included within the scope that does not deviate from the gist of the present disclosure.

[0049] The dust collecting devices 2, 2A, and 2B are not limited to the structure of this embodiment. Therefore, for example, the dust collecting devices 2, 2A, and 2B may not include the water supply unit 26. The dust collecting device 2A of the second embodiment may also include a heating unit 41, an upper droplet supply unit 42, and an upper charging unit 43. Furthermore, the dust collecting device 2B of the third embodiment is not limited to a structure in which only one set of the heating unit 41, the upper droplet supply unit 42, and the upper charging unit 43 is provided. Multiple sets of the heating unit 41, the upper droplet supply unit 42, and the upper charging unit 43 may be provided between the charging unit 23 and the dust collecting unit 24.

[0050] The droplet supply unit 22 is not limited to being a spray gun that sprays cooling water in the form of a mist or fine droplets, as in this embodiment. The droplet supply unit 22 may have any structure as long as it can supply droplets that are at a temperature lower than the exhaust gas upward in the vertical direction Dv. Furthermore, the droplet supply unit 22 is not limited to supplying cooling water. The droplet supply unit 22 may supply any liquid as long as the liquid has a different component from the sulfur trioxide-containing liquid contained in the exhaust gas.

[0051] The heating unit 41 is not limited to being a spray gun that sprays high-temperature water in the form of a mist or fine droplets, as in this embodiment. Therefore, the heating unit 41 does not have to be structured to spray a liquid, as long as it can heat the exhaust gas that has passed through the charging unit 23. Furthermore, even when the heating unit 41 supplies a liquid, it is not limited to supplying water. The heating unit 41 may supply any liquid as long as it is at a temperature higher than that of the exhaust gas and droplets.

[0052] The upper droplet supply unit 42 is not limited to being a spray gun that sprays cooling water in the form of a mist or fine droplets, as in this embodiment. The upper droplet supply unit 42 may have any structure as long as it can supply droplets having a temperature lower than that of the exhaust gas upward in the vertical direction Dv. Furthermore, the droplet supply unit 22 is not limited to supplying cooling water. The droplet supply unit 22 may supply any liquid as long as the liquid has a component different from the sulfur trioxide-containing liquid contained in the exhaust gas. Therefore, the upper droplet supply unit 42 may supply a liquid different from that of the droplet supply unit 22.

[0053] Furthermore, the droplet supply unit 22, the charging unit 23, the heating unit 41, the upper droplet supply unit 42, and the upper charging unit 43 are not limited to being provided in multiple numbers as in this embodiment. Therefore, for example, only one droplet supply unit 22, one charging unit 23, one heating unit 41, one upper droplet supply unit 42, and one upper charging unit 43 may be provided.

[0054] <Additional Notes> The dust collecting devices 2, 2A, and 2B described in the respective embodiments can be understood, for example, as follows.

[0055] (1) The dust collector 2, 2A, 2B according to the first aspect includes a casing 21 having an exhaust gas flow path formed therein through which exhaust gas flows upward in a vertical direction Dv, a droplet supply unit 22 arranged in the exhaust gas flow path and supplying droplets having a temperature lower than that of the exhaust gas upward in the vertical direction Dv, a ring-shaped charging unit 23 arranged in the exhaust gas flow path above the vertical direction Dv relative to the droplet supply unit 22 and charging the droplets that have passed through it, and a dust collector 24 arranged in the exhaust gas flow path above the vertical direction Dv relative to the charging unit 23 in a grounded state and collecting fine particles and the droplets contained in the exhaust gas.

[0056] According to this configuration, droplets having a lower temperature than the exhaust gas are supplied from the droplet supply unit 22 upward in the vertical direction Dv to the exhaust gas flowing through the exhaust gas flow path. The supplied droplets are mixed with the exhaust gas flowing through the exhaust gas flow path. As a result, the high-temperature exhaust gas is cooled, and saturated water vapor contained in the exhaust gas condenses into fine particles, typically sulfur trioxide. As a result, the fine particles grow larger and coarser. Furthermore, the droplets supplied from the droplet supply unit 22 pass through the ring-shaped charging unit 23 and are charged. The ring-shaped charging unit 23 prevents corona discharge from occurring between the droplet supply unit 22 and the droplets. The charged droplets then collide with the coarse sulfur trioxide-containing fine particles, which are then absorbed into the charged droplets. As a result, the fine particles are entrained in droplets with very large diameters, further increasing their size. In this state, the large droplets containing the fine particles enter the dust collection unit 24. As a result, the dust collection unit 24 can capture most of the fine particles such as sulfur trioxide contained in the exhaust gas by simply collecting droplets with large particle diameters that are easy to collect, thereby improving the efficiency of collecting the fine particles contained in the exhaust gas.

[0057] (2) The dust collectors 2, 2A, and 2B according to the second aspect are the dust collectors 2, 2A, and 2B of (1), in which the droplet supply unit 22 supplies the droplets by spraying a liquid having a different component from the liquid containing sulfur trioxide contained in the exhaust gas.

[0058] This configuration allows only the sulfur trioxide originally present in the exhaust gas to be coarsened without supplying additional sulfur trioxide to be removed from the exhaust gas into the exhaust gas flow path, thereby improving the efficiency of collecting particulates contained in the exhaust gas.

[0059] (3) The dust collecting device 2A according to the third aspect is the dust collecting device 2, 2A, 2B of (1) or (2), and further includes a straightening plate 31 having a plurality of through holes 32 and arranged between the charging section 23 and the dust collecting section 24 in the vertical direction Dv in a grounded state.

[0060] With this configuration, the droplets pass through the through holes 32. At this time, the exhaust gas containing sulfur trioxide mixes with the through holes 32, increasing the chances of the droplets and sulfur trioxide colliding with each other. As a result, many large droplets containing fine particles flow into the dust collecting section 24, increasing the efficiency of capturing the fine particles. This further improves the efficiency of collecting the fine particles contained in the exhaust gas.

[0061] (4) A dust collecting device 2B according to a fourth aspect is a dust collecting device 2, 2A, 2B according to any one of (1) to (3), and further includes a heating section 41 arranged in the exhaust gas flow path above the charging section 23 in the vertical direction Dv, for heating the exhaust gas that has passed through the charging section 23; an upper droplet supply section 42 arranged in the exhaust gas flow path above the heating section 41 in the vertical direction Dv, for supplying droplets having a lower temperature than the exhaust gas upward in the vertical direction Dv; and an upper charging section 43 arranged in the exhaust gas flow path above the vertical direction Dv relative to the upper droplet supply section 42, formed in a ring shape, for charging the droplets that have passed through its interior, and the dust collecting section 24 is arranged in the exhaust gas flow path above the vertical direction Dv relative to the upper charging section 43.

[0062] With this configuration, the droplets and exhaust gas sprayed from the droplet supply unit 22 and charged by the charging unit 23 are heated. That is, the exhaust gas cooled by the droplet supply unit 22 is heated by the heating unit 41. As a result, the amount of saturated water vapor in the exhaust gas increases. Then, cooling water is sprayed from the upper droplet supply unit 42 upward in the vertical direction Dv onto the heated droplets and exhaust gas. The sprayed cooling water mixes with the droplets and exhaust gas flowing through the exhaust gas flow path. As a result, the high-temperature exhaust gas heated by the heating unit 41 is cooled again, and the saturated water vapor contained in the exhaust gas condenses into liquid containing fine particles. Therefore, the liquid containing fine particles in the exhaust gas is condensed once by the droplet supply unit 22 and then condensed again by the upper droplet supply unit 42. As a result, the liquid containing fine particles becomes coarse and has a very large particle size. In addition, the droplets sprayed from the upper droplet supply unit 42 are charged as they pass through the ring-shaped upper charging unit 43. Then, when the charged droplets collide with the liquid containing very coarse particles, the liquid containing the coarse particles is absorbed into the charged droplets. As a result, the particles are contained in droplets of very large diameter and become even coarser. Therefore, compared to when cooling and charging are performed only once, the large droplets containing the particles can be made much larger. In this state, the large droplets containing sulfur trioxide enter the dust collector 24. As a result, the dust collector 24 can capture many of the fine particles, such as sulfur trioxide, contained in the exhaust gas by simply collecting droplets of very large diameter, which are easy to capture. This further improves the efficiency of collecting fine particles contained in the exhaust gas.

[0063] (5) The dust collecting device 2B according to the fifth aspect is the dust collecting device 2, 2A, 2B of (4), in which the heating section 41 sprays a liquid having a higher temperature than the exhaust gas that has passed through the charging section 23 downward in the vertical direction Dv.

[0064] With this configuration, the high-temperature liquid can be supplied so as to come into countercurrent contact with the cooled and charged droplets and exhaust gas, thereby efficiently heating the droplets and exhaust gas flowing through the exhaust gas flow path. [Explanation of symbols]

[0065] 1. Exhaust gas treatment system 10 Exhaust gas emission equipment 2,2A,2B Dust collector 21 Casing 22 Droplet supply section 23 Charging section 24 Dust collection section 25,45 High voltage power supply 26 Water supply section 31 Rectifier plate 32 Through hole 41 Heating section 42 Upper droplet supply section 43 Upper charging part Dv vertical direction

Claims

1. a casing having an exhaust gas flow path formed therein through which exhaust gas flows vertically upward; a droplet supply unit disposed in the exhaust gas flow path and configured to supply droplets having a temperature lower than that of the exhaust gas upward in the vertical direction; a charging unit that is arranged in the exhaust gas flow path above the droplet supply unit in the vertical direction, is formed in a ring shape, and charges the droplets that have passed through an interior thereof; a dust collecting unit that is grounded and disposed in the exhaust gas flow path above the charging unit in the vertical direction, and that collects fine particles and the liquid droplets contained in the exhaust gas.

2. The dust collecting device according to claim 1 , wherein the droplet supplying unit supplies the droplets by spraying a liquid having a component different from the liquid containing sulfur trioxide contained in the exhaust gas.

3. The dust collecting device according to claim 1 or 2, further comprising a current plate having a plurality of through holes, the current plate being disposed between the charging unit and the dust collecting unit in the vertical direction in a grounded state.

4. a heating unit that is disposed in the exhaust gas flow path above the charging unit in the vertical direction and heats the exhaust gas that has passed through the charging unit; an upward droplet supply unit that is disposed in the exhaust gas flow path above the heating unit in the vertical direction and that supplies droplets having a temperature lower than that of the exhaust gas upward in the vertical direction; an upper charging unit that is arranged in the exhaust gas flow path above the upper droplet supply unit in the vertical direction, is formed in a ring shape, and charges the droplets that have passed through an interior thereof; The dust collecting device according to claim 1 or 2, wherein the dust collecting unit is disposed in the exhaust gas flow path above the upper charging unit in the vertical direction.

5. The dust collecting device according to claim 4 , wherein the heating unit sprays liquid having a temperature higher than that of the exhaust gas that has passed through the charging unit, downward in the vertical direction.

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