JP2000140691A - Dry type dust collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently remove dust, and to make the collector compact as a whole and reduced in cost by integrating a rough electric dust collector with a dielectric sphere type dust collector. SOLUTION: This dry type dust collector includes a 1st stage rough electric dust collector 10 for previously electrostatically charging and collecting dust in a dust-containing exhaust gas, a 2nd stage dust collector 16, provided in the down stream from the 1st stage rough electric dust collector in the flow direction of the exhaust gas and provided with high voltage electrodes 13, 13', earth electrodes 11, 11', 11" and electrically insulating dielectric balls 14 for attracting and collecting the electrostatically charged dust, and a dust separating means for separating the dust from the dielectric balls 14 on which the dust discharged from the 2nd stage dust collector 16 is deposited.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry dust remover for removing dust from dust-containing gas discharged from a boiler or an incinerator.

[0002]

2. Description of the Related Art The most common type of dust collector is an electric dust collector, which is used in a wide range of fields by utilizing the characteristics of low pressure loss, high performance and maintenance free. This electrostatic precipitator charges the dust in the exhaust gas by corona discharge, moves the charged dust to the precipitating pole by Coulomb force, and collects and accumulates it on the precipitating pole. Dust had to travel a distance. Such a dry dust collecting device that adheres and collects by reducing the moving distance of the dust is, for example, a device that continuously removes dust from dust-containing exhaust gas, such as a filling device disposed between electrodes to which a high voltage is applied. BACKGROUND ART An electrostatic filter that collects dust by passing a dust-containing gas between objects is known.

[0003] Japanese Patent Publication No. 56-48214 discloses a method in which a particulate filler is filled between electrodes to which a high voltage is applied, and exhaust gas containing dust is passed through the packed layer to remove dust in the exhaust gas. An apparatus for collecting dust and a method for collecting dust using the apparatus are disclosed. Further, JP-A-63-27056
No. 0 describes a packed bed dust collecting apparatus in which dust is forcibly charged, and charges of opposite polarity are continuously supplied to the insulating spheres in the packed bed to improve the dust collecting performance. When the dust layer adheres to the packed layer and collects it, the charged layer consists of a high-dielectric-constant insulator sphere that is charged in the opposite polarity to the dust particles. The charging device to be provided is provided on the upstream side of the packed bed.

[0004] The above-mentioned dry type dust collecting apparatus is an expensive equipment, and when a large amount of dust is treated by dust collection using only an electrostatic filter or a packed bed, the dust removing efficiency is reduced immediately and the pressure loss is reduced. The increase is also large. That is, conventionally, a charging device is provided on the upstream side of the packed layer to charge the dust, but if only the charging of the dust is performed, the amount of the dust to be processed by the packed layer is large, and the performance immediately deteriorates. Similarly, the pressure loss rises quickly. Therefore, if the amount of dust is large, it is necessary to increase the capacity of the dust collection equipment, and not only the site area but also the installation cost and the operating cost increase.

[0005] Therefore, in order to solve the above-mentioned difficulties, it is required to reduce the capacity of the dry dust collection equipment. However, it is not preferable that the dust-removing performance is reduced due to the reduction in the capacity of the dry dust collection equipment. Further, in the conventional apparatus, since the dirty insulating balls in the packed bed are replaced by the gate valve at regular time intervals, there is a disadvantage that the replacement operation is troublesome. Further, the related art only discloses the dust removing action of the insulating sphere, but does not disclose the acid gas absorbing action.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-mentioned problems of the prior art, and has been described in view of the above.
It is an object of the present invention to provide an inexpensive and highly efficient exhaust gas dust removal facility capable of achieving compactness.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a first-stage coarse electric dust collecting apparatus which performs charging of dust and coarse dust collection to form a second-stage dust collecting apparatus. The dust removal load has been reduced. Therefore, according to one aspect of the present invention, a first-stage roughing electrostatic precipitator having both dust collecting and charging functions in advance for dust contained in dust-containing exhaust gas, A second stage dust collector downstream of the device in the flow of the exhaust gas and comprising a high voltage electrode, a ground electrode and an electrically insulating dielectric sphere for adhering and collecting the charged dust. There is provided a dry dust remover including an apparatus and dust separating means for separating dust from dielectric balls to which dust discharged from the second-stage dust collector adheres. here,
Although it is preferable that the first-stage dust collector and the second-stage dust collector are integrally formed, they need not always be integrated. Both dust collectors need only be installed adjacent to each other, and can be connected between them by a ventilation pipe.

[0008] By integrally providing an electrically insulating dielectric ball type dust collector and a coarse dust collecting device upstream thereof, a large amount of dust can be collected. As compared with the case of dust removal using only a layer, a dry dust remover that can achieve downsizing of the entire equipment can be provided by reducing the dust removal load on one of the devices. In addition, after the dust-containing exhaust gas is passed through an upstream roughing electrostatic precipitator to pre-charge the dust in the dust-containing gas, the charged dust adheres to the dielectric spheres using a dielectric sphere type dust collector. By collecting, it is possible to collect particles having a particle diameter of several μm or less that are difficult to be collected by the coarse electric precipitator, thereby improving the dust removal efficiency as a whole.

Further, according to the present invention, in the above-mentioned dry dust remover, a rotary exhaust means for extracting the dielectric sphere to which the dust adheres can be provided below the second-stage dust collector. . By providing the rotary discharge device below the electrically insulating dielectric sphere type dust collector, the dielectric sphere to which the dust adheres is taken out. The rotary discharge means includes a plurality of rollers, and the number of rotations of the rollers is controlled by controlling the number of rotations of the motor of each roller to adjust the discharge speed of the dielectric sphere. Thereby, the residence time of the dielectric sphere in the gas can be adjusted. Still further, according to the present invention, a vibrating screen, a washing device, or an air blowing device can be additionally provided as a means for separating the dust from the dielectric spheres to which the dust has adhered. A dryer is installed at the outlet of the second-stage dust collector for drying the dielectric balls later.

Further, according to the present invention, the second-stage dust collector is arranged so that the cross-sectional area of the dielectric sphere layer is large so that the flow rate of the passing exhaust gas can be made uniform and equal to or less than a predetermined value. Can be changed. That is, by arranging a plurality of dielectric sphere layers in parallel at a distance, the flow velocity of the exhaust gas can be made uniform and equal to or less than a fixed value, and the pressure loss can be reduced. At this time, the dielectric sphere layer can be arranged so as to be parallel to the flow of the exhaust gas from the first-stage dust collector. Further, according to the present invention, the dielectric sphere filled in the second-stage dust collector can be selected from ceramic spheres of alumina, granules of alkali agent, and the like. When an alkaline agent is used, it can absorb an acid gas in addition to the dust removing action.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a dry dust remover according to the present invention will be further described with reference to the drawings. FIG. 1 shows an embodiment of an example of a dry dust remover according to the present invention, but it goes without saying that the present invention is not limited to this example. First, in the first-stage coarse dust collection device 10, coarse dust, mainly dust of the order of 10 μm, is roughly removed while passing dust in the exhaust gas in the direction of G through a corona discharge in advance to charge the dust in the exhaust gas. I do. By pre-charging and roughly removing the dust by the coarse dust collecting device 10, a good dust collecting effect can be obtained comprehensively including the second-stage dust collecting device.

The first-stage coarse dust collecting apparatus 10 may basically have a configuration similar to a conventional electric dust collecting apparatus. In the first-stage coarse dust collection device 10, a high-voltage electrode (discharge electrode) 30 to which a high voltage is applied is arranged between a plurality of ground electrodes (dust collection electrodes) 31. The high-voltage electrode 30 is composed of linear conductors having various cross-sectional shapes. When a DC or AC high voltage is applied, a corona discharge occurs between the high voltage electrode 30 and the ground electrode 31, and the corona discharge charges the dust. At least a part of the charged dust is attracted to the ground electrode 31 by Coulomb force and collected. In order to be able to easily remove the collected dust by known means such as hammering,
It is preferable that the ground electrode (dust collecting electrode) 31 be disposed upright in a substantially vertical direction. In order to increase the efficiency of collection, it is preferable to have a certain area. Therefore, the number of the high-voltage electrodes (discharge electrodes) 30 is preferably two or more per one ground electrode, and more preferably about three to five.

The dust particles which have been charged but not collected by the coarse dust collecting device 10 are integrated with the first stage coarse dust collecting device 10 by the casing 9 and provided downstream thereof. -Stage dust collector 1 consisting of a dielectric sphere layer
Collected at 6. The dielectric sphere layer 16 is formed on the high-voltage electrode 1.
3, 13 'and ground electrodes 11, 11', 11 ", and an insulating dielectric sphere 14 is filled between the high-voltage electrode and the ground electrode. In FIG. 1, two sets of dielectric sphere layers are shown. Although described, the present invention is not limited to this, and one set or three or more sets of dielectric sphere layers can be used.

According to the present invention, a DC high voltage is applied to the dielectric sphere to dielectrically polarize the dielectric sphere, and the charged dust is generated by the Coulomb force strengthened by the opposite polarity electric charge appearing on the surface of the adjacent dielectric sphere. It adheres to the surface of the dielectric sphere and is collected. That is, the high-voltage generating device 17 uses the high-voltage electrodes 13 and 13 ′.
When a high voltage is applied to the dielectric particles 14, the dielectric spheres 14 sandwiched between the high-voltage electrodes 13, 13 'and the ground electrodes 11, 11', 11 "are dielectrically polarized. Is subjected to Coulomb force by an electric field formed between a plurality of polarized dielectric spheres 14, and is collected on the surface of the dielectric sphere 14. The above-described dielectric sphere 14 is not particularly limited, but is not limited thereto. Here, a ceramic sphere such as alumina is used, and the dielectric sphere 14 has a particle diameter of 3 to 40 mm, preferably 5 to 10 mm.
In the case of No. 4, if it becomes dirty with dust, the performance of collecting dust particles decreases. Therefore, the dielectric sphere is moved out of the dielectric sphere layer within a time during which no significant performance deterioration occurs.

The dielectric sphere may be an alkaline solid absorbent that reacts with an acidic gas, for example, MgO, C
An aO powder can be used, which enables simultaneous processing of dust removal and acid gas absorption. Such an alkaline agent powder is commercially available, and may have a particle size of about 200 μm. If desired, the powder can be formed into larger diameter spheres. The above-mentioned alkaline absorbent is withdrawn and supplied in a fixed amount according to the reaction amount with an acidic gas (SO _x , HCl, etc.). The reacted surface of the alkaline agent powder is renewed by rubbing between the particles or between the particles and each part of the device, so that the absorption capacity of the acidic gas can be maintained for a relatively long period.

Subsequently, a moving bed method is used for moving the dielectric spheres on which dust is adhered and collected. That is, a rotary discharge means 15 for moving the dielectric sphere 14 below the second-stage dust collector is provided, and the dielectric sphere to which the dust adheres is taken out. The rotary discharge means 15 includes a discharge device driven by a motor or the like (not shown), for example, a roller, and rotary blades 25, 26, 27, and 28.
At this time, the removal amount of the dielectric sphere can be changed by controlling the rotation speed of the rotary blades 25 and 26 on the upstream side of the rotary discharge means 15 and the rotary blades 27 and 28 on the downstream side. That is, by making the rotation speed of the upstream rotary blades 25, 26 of the rotary discharge means 15 faster than the rotation speed of the downstream rotary blades 27, 28,
By performing control such that the movement of the upstream dielectric sphere to which more dust adheres is made faster, the dielectric sphere 14 can be updated in accordance with the amount of dust attached.

If the dielectric spheres are contaminated with dust, the performance of the dielectric spheres to collect dust is reduced. for that reason,
It is preferable to move the dielectric sphere out of the dielectric sphere layer within a time when its trapping performance is not significantly reduced. Therefore, an operation of setting a sequence to control the discharge amount according to the dust load at the inlet, for example, monitoring the gas amount and the dust concentration, and moving the dielectric sphere when the amount of collected dust exceeds the reference value is performed. It is possible. Further, the rotary discharge means 15 may be grounded to reduce dust adhesion.

For the separation of the dust from the dielectric sphere that has collected the dust, mechanical vibration by the vibrating screen 20 can be used. The vibrating screen 20 is used as a metal mesh to separate dust on the screen 20 and collect the dust in the dust hopper 22. The vibrating screen 20 includes
The dielectric sphere has a slope so that it can roll off smoothly. The mesh of the vibrating screen 20 has a size corresponding to the particle diameter of the dielectric sphere, for example, a size of about 2 mm. The vibrating screen should be grounded to reduce dust adhesion. The dielectric sphere reproduced through the vibrating screen 20 is moved to the upper part of the dielectric sphere layer via the conveyor 21 and reused. Further, in order to more efficiently separate the adhering dust, when the dielectric sphere on which the dust is adhering is taken out by the rotary discharge means 15, air may be blown down. The dust separated in this way is omitted in the drawing, but is pulled by a fan and collected by a bag filter.

Further, in order to separate the dust from the dielectric sphere 14, a washing device may be used instead of the vibrating screen. Fig. 2 shows the case where this washing device is provided.
Shown in In FIG. 2, after the dielectric spheres are rinsed with a water rinsing device 41, the dielectric spheres are dried by a dryer 40 provided at the outlet of the dust removing device in order to ensure insulation of the dielectric spheres 14. At this time, exhaust heat from an exhaust gas source can be used as a drying heat source. The dried dielectric sphere 14 is line C
To the second-stage dust collecting device 16. The contaminated water extracted from the washing device is omitted in the drawing,
Dispose of in wastewater treatment equipment. Further, at the time of collecting and separating the dielectric sphere, an air blowing device may be provided to wash the dielectric sphere. At that time, the air is pulled by a fan and collected by a bag filter. Further, the washing device and the vibrating screen can be combined.

FIG. 3 is a top view of another embodiment of the dry dust remover of the present invention as a modification of the dielectric ball layer.
As shown in FIG. 3, a pair of dielectric sphere layers composed of two ground electrodes opposed to each other with a high voltage electrode therebetween and an insulating dielectric sphere filled therebetween are arranged at regular intervals as shown in FIG. A plurality is arranged so as to be parallel to the exhaust gas flow from the dust collector. According to such a configuration, the surface area of the dielectric sphere layer with respect to the gas flow can be increased while having a compact design, so that the flow velocity of the passing gas can be reduced and the pressure loss can be reduced. This can reduce the power of the fan for maintaining the exhaust gas flow.

[0021]

EXAMPLE Except for the number of ground electrodes and the number of high-voltage electrodes being 1, the dry dust removing apparatus of the present invention having the same structure as that shown in FIG. First, a test for the base pressure loss characteristics was performed, and the pressure loss with respect to the gas flow rate during air loading is shown in FIG. At this time, the pressure loss of the perforated plate was very small compared to the whole, and was ignored. When the pressure loss ΔP is measured, the pressure loss coefficient ξ is obtained by the following equation. [Equation 1] ΔP = L · ξ (1/2) ρu ² [Pa] where L is the layer thickness (m), and ρ is the air density (kg /
m ³ ) and u represent the cross-sectional average gas flow rate (m / s). The pressure loss coefficient に よ り calculated by the above equation is as follows.

Next, the effect of charging the first-stage coarse dust collector and the charging of the dielectric sphere layer (second-stage dust collector) was tested. In order to confirm the operation of the principle, the first-stage coarse-dust collecting device and the dielectric sphere were turned on and off, respectively, and measurement was performed under each condition. Table 1 shows the results. Example C and Example D
There is no big difference, and there is a big difference between Example B and Example C.
It can be seen from the effect of the first-stage coarse dust collector that the influence of the charge of the dielectric sphere is strong.

[Table 1]

In the above test, it was found that the electric field strength of the dielectric sphere greatly affected the dust collection efficiency. Therefore, the change in the dust collection efficiency was grasped using the electric field strength as a parameter. Under the following test conditions, a test regarding the change in the electric field strength of the dielectric sphere was performed, and the results are shown in FIG. As is apparent from FIG. 5, the electric field intensity is saturated at 3 kV / cm, and thereafter, the electric field intensity becomes 3.kV / cm.
The test was performed at 3 kV / cm (applied voltage: 50 kV). The electric field strength is calculated by dividing the dielectric sphere voltage by the distance (here, 15 cm) between the high-voltage electrode and the ground electrode. Test conditions Dielectric sphere diameter: φ40 mm First stage roughing unit voltage: 20 kV Dielectric sphere voltage: 10 to 80 kV Gas flow rate: 1 m / s Dielectric sphere layer thickness: 300 mm Dielectric sphere entrance dust concentration: 1 g / M ³ N Operating time: 3 hours

With respect to the dielectric spheres having a particle diameter of 40 mm and 10 mm, the dust collection efficiency was measured when the flow velocity was changed, and the results were shown in FIG. 6 (φ = 40 mm) and FIG.
0 mm). The test conditions are as follows. Test conditions Dielectric sphere diameter: φ10 mm, φ40 mm First stage roughing unit voltage: 20 kV Dielectric sphere voltage: 50 kV Gas flow rate: 0.25, 0.5, 1.0 m / s Dielectric sphere layer thickness: 300 mm dielectric sphere entrance dust concentration: 1 g / m ³ N

With respect to the pressure loss and the dust collection efficiency of the dielectric sphere layer, their time changes were measured. The test conditions are summarized in Table 2. With respect to the pressure loss, there was almost no change over the operation time of 3 hours, and even in the case of the highest dust collection efficiency (dielectric sphere particle diameter 10 mm, gas flow rate 0.25 m / s), the initial 6.5 mmAq to 7.5 mmAq. Has changed. FIG. 8 (φ = 40 mm) and FIG. 9 (φ = 10 mm) show the time change of the dust collection efficiency. It can be seen that the efficiency has decreased from one hour after the start.

[Table 2]

[0026]

As is apparent from the above description, according to the dry dust removing apparatus of the present invention, the electrically insulating dielectric ball type dust collecting apparatus and the coarse dust collecting apparatus are integrally provided upstream of the dust collecting apparatus. Accordingly, dust can be collected with high efficiency. Further, as compared with the case of dust removal using only the rough dust collection device or the electrically insulating dielectric sphere layer, the size of the entire dust removal facility can be reduced by reducing the dust removal load applied to one of the devices. In other words, the electric dust collector does not require a high degree of dust collection because it aims at charging and roughing the dust, and can reduce the dust removal load. In addition, the dust collection by the dielectric sphere can reduce the dust removal load by treating the low-concentration dust roughly removed on the upstream side, so that only a small capacity is required. And even if it combines comprehensively, compared with the apparatus scale which one conventional apparatus processed, downsizing of the whole dust removal equipment can be achieved.

Further, the dust-containing exhaust gas is passed through an upstream dust-collecting electric precipitator, and the dust in the dust-containing gas is charged in advance to roughly remove the dust. By adhering and collecting the dielectric spheres with the device, dust having a particle size of several μm or less, which is difficult to be collected by the roughing electrostatic precipitator, can be collected, and the dust removal efficiency can be improved. Furthermore, by installing a rotary discharge means below the second-stage dust collector and changing the rotation speed of a motor or the like of this means, the discharge speed of the dielectric sphere can be changed. Thereby, the residence time of the dielectric sphere can be adjusted. Further, in the second-stage dust collector, a plurality of dielectric sphere layers are arranged in parallel at a distance from each other, so that the flow velocity of the passing exhaust gas is made uniform and equal to or less than a predetermined value, thereby reducing the pressure loss of the dielectric sphere layers. As a result, energy consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining the principle of dust removal in an embodiment of a dry dust remover according to the present invention.

FIG. 2 is a block diagram illustrating an embodiment of a dry dust remover according to the present invention.

FIG. 3 is a view showing an arrangement of a modified example of the second-stage dust collector of the present invention.

FIG. 4 is a view showing a base pressure loss characteristic of a dielectric layer in the dry dust remover of the present invention.

FIG. 5 is a diagram showing a change in dust removal efficiency with respect to an electric field intensity of a dielectric layer in the dry dust remover of the present invention.

FIG. 6 is a diagram showing the dust collection efficiency (when the particle diameter of the dielectric sphere is 40 mm) depending on the change in gas flow velocity in the dry dust remover of the present invention.

FIG. 7 is a diagram showing the dust collection efficiency (when the particle diameter of the dielectric sphere is 10 mm) depending on the change in the gas flow rate in the dry dust remover of the present invention.

FIG. 8 is a diagram showing a change over time in dust removal efficiency (when the particle diameter of the dielectric sphere is 40 mm) in the dry dust remover of the present invention.

FIG. 9 is a diagram showing a change over time in dust removal efficiency (when the particle diameter of the dielectric sphere is 10 mm) in the dry dust remover of the present invention.

[Explanation of symbols]

 Reference Signs List 8 Dust 9 Casing 10 First stage coarse dust collector 11, 11 ', 11 "Ground electrode 13, 13' High voltage electrode 14 Dielectric ball 15 Rotary discharge means 16 Second stage dust collector 17 High voltage generator Reference Signs List 20 Vibrating screen 21 Conveyor 22 Dust recovery hopper 25, 26, 27, 28 Rotary blade 30 High voltage electrode 31 Ground electrode 40 Dryer 41 Washing device G Inflow direction of dust-containing exhaust gas G 'Outflow direction of clean gas C Dielectric ball Resupply line

Continued on the front page (72) Inventor Yasuminori Ueda 2-1-1 Shinama, Arai-machi, Takasago City, Hyogo Prefecture Inside the Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Keishiro Saito 2-1-1, Niihama, Arai-machi, Takasago City, Hyogo Prefecture F term in Takasago Research Laboratory, Mitsubishi Heavy Industries, Ltd. (reference) 4D002 AA02 AA19 AB01 BA03 BA07 BA14 CA08 DA05 DA06 DA11 DA46 EA02 EA09 EA20 GA01 GA03 GB01 GB04 GB12 GB20 HA03 HA10 4D054 AA02 BA07 BC14 BC31 DA01 DA06 DA07 DA15 EA27 EA30

Claims (8)

[Claims] Claims: 1. Dust in a dust-containing exhaust gas is charged in advance,
A first-stage coarse electric precipitator for collecting dust; a high-voltage electrode, a ground electrode, and the above-mentioned charged electric charge downstream of the exhaust gas flow with respect to the first-stage coarse electric precipitator; A second-stage dust collector comprising an electrically insulating dielectric sphere for adhering and collecting the dust, and separating the dust from the dielectric sphere to which the dust discharged from the second-stage dust collector adheres A dry dust removing device including dust separating means. 2. A rotary discharge means for discharging the dielectric sphere from below the second-stage dust collector, and a conveyor for moving the dielectric sphere to an upper part of the second-stage dust collector. The dry dust removal apparatus according to claim 1, further comprising: 3. The dry dust removing apparatus according to claim 2, wherein said dust separating means is a vibrating screen. 4. The dry dust removing apparatus according to claim 2, wherein said dust separating means includes a water washing device and a dryer for drying the dielectric balls after the water washing by said water washing device. 5. The dry dust removing apparatus according to claim 2, wherein said dust separating means includes an air blowing device. 6. The rotary discharge means comprises a plurality of discharge devices, and independently controls the number of revolutions of each discharge device to adjust the residence time of the dielectric sphere. The dry dust remover according to any one of 2 to 5. 7. The second-stage dust collector comprises a plurality of dielectric sphere layers through which exhaust gas passes, and the dielectric layers are spaced apart from each other and arranged substantially in parallel. The dry dust remover according to any one of claims 1 to 6. 8. The dry dust remover according to claim 1, wherein the dielectric sphere is an alkali agent, and absorbs an acid gas in addition to a dust removing action.