WO2015068209A1

WO2015068209A1 - Dust collection device and dust collection method

Info

Publication number: WO2015068209A1
Application number: PCT/JP2013/079932
Authority: WO
Inventors: 一隆富松; 雅也加藤; 崇雄田中; 泰稔上田; 勝久小嶋
Original assignee: 三菱重工メカトロシステムズ株式会社
Priority date: 2013-11-05
Filing date: 2013-11-05
Publication date: 2015-05-14

Abstract

Provided are: a dust collection device that has high dust collection efficiency and is capable of being made more compact; and a dust collection method using this dust collection device. A collection unit (1) in the dust collection device has: a dust collection area (2); a plurality of discharge electrodes (10) arranged in the depth direction from an inlet (3) in the dust collection area (2); an earth electrode (5) having an opening through which gas can flow and facing the tips of discharge needles (12) in the discharge electrodes (10); a filter (6) arranged on the outside of the earth electrode (5); and a purified-gas passage (17) positioned on the downstream gas side of the dust collection area (2), via the earth electrode (5) and the filter (6). In the collection unit (1), the flow rate of the gas that passes through the filter (6) is made substantially uniform as a result of making the length of the discharge needles (12) longer on the inlet (3) side than on the depth side of the dust collection area (2) or making the filter (6) on the depth side thicker than on the inlet (3) side of the dust collection area (2).

Description

Dust collector and dust collection method

The present invention relates to a dust collector and a dust collection method for removing particulate matter from gas.

In an industrial combustion facility such as a coal-fired or heavy oil-fired power plant or an incinerator, exhaust gas containing dust (for example, particulate matter) and SOx is generated by combustion. In order to exhaust the exhaust gas to the atmosphere after removing these dusts and SOx, an exhaust gas treatment facility is installed in the flue downstream of the combustion facility.

The exhaust gas treatment facility is provided with a desulfurizer, a dust collector, and the like. In a desulfurization apparatus using a wet method, for example, alkali such as magnesium hydroxide (Mg (OH) ₂ ) is used as an absorbent, and a liquid containing the absorbent is sprayed toward exhaust gas. SOx is surrounded by the liquid and reacts with the absorbent to remove SOx from the exhaust gas.

The dust collector includes a discharge electrode for charging the particulate matter and a ground electrode disposed opposite to the discharge electrode in order to remove the particulate matter and mist. When the corona discharge is generated at the discharge electrode, the particulate matter contained in the exhaust gas is charged. The charged particulate matter is collected by the ground electrode.

In Patent Document 1, in order to reliably collect particulate matter while gas flows in the casing, the particulate matter is accelerated in a direction crossing the gas flow in the casing by ion wind, and the conductive mesh is overlapped. A technique for collecting particulate matter by passing through a ground electrode is disclosed.

In Patent Document 2, in a dust collector equipped with a wet electrostatic filter that removes mist (SOx mist) in which dust and SOx have been taken in, a ground electrode is disposed around the discharge electrode, and the discharge electrode and the ground are disposed. It is disclosed that a filter layer for collecting dust is provided between the electrodes.

JP 2007-117968 A JP 2013-123692 A

In the method described in Patent Document 1, when the main gas flow is faster than the flow generated by the ionic wind (the flow in the direction crossing the main gas flow), the ground electrode is within the time that the main gas passes through the apparatus. There are particulate matter that can not reach. For this reason, it has been a problem that the removal efficiency of the particulate matter is poor. In order to improve the removal efficiency by the method of Patent Document 1, it is necessary to lengthen the gas flow path in the apparatus, and the dust collecting apparatus itself becomes large.

In a dust collector using a filter as described in Patent Document 2, a low-pressure loss filter (about 10 to 30 mmAQ at an initial pressure loss) is employed to operate the dust collector with low power. In the apparatus of Patent Document 2, a sufficient filter length is ensured in the depth direction of the wet electrostatic filter to reduce the gas flow rate in the filter. However, in the vicinity of the inlet of the collection part, the gas is contracted and the pressure loss of the filter is low, so that the inflow speed is greatly reduced compared to other parts. On the other hand, the flow velocity of the collecting portion tends to gradually increase as it goes to the back side of the filter due to the influence of dynamic pressure. That is, there is a problem that the gas flow velocity is distributed in the wet electrostatic filter and the dust collection efficiency of the entire filter is lowered.

The present invention has been made in view of the above problems, and provides a dust collector capable of improving dust collection efficiency and further reducing the size of the device, and a dust collection method using the dust collector. The purpose is to do.

According to a first aspect of the present invention, there is provided a dust collection area having an inlet portion into which a gas is introduced, a mounting shaft installed in the dust collection area, and a plurality of thorn-shaped discharge spikes protruding from the mounting shaft. A plurality of discharge electrodes, and an opening through which the gas can flow, an earth that is substantially perpendicular to the direction in which the discharge spike extends, and that constitutes the wall surface of the dust collection area facing the tip of the discharge spike An electrode, a filter installed outside the ground electrode, through which the gas in the dust collection area passes, and a clean gas passage located on the gas downstream side of the dust collection area through the ground electrode and the filter; A power source for applying a voltage to the discharge electrode, and the mounting shaft of each of the discharge electrodes extends in a direction substantially perpendicular to a direction in which the gas flows into the dust collection area, and a plurality of the discharge electrodes The electrode is in the dust collection area. The length of the discharge barb of the discharge electrode arranged in the depth direction from the entry port and located at the inlet part of the dust collection area is equal to the length of the discharge barb of the discharge electrode located at the back side of the dust collection area. A dust collector that generates a corona discharge between the discharge barb and the ground electrode.

1st aspect WHEREIN: It is preferable that the length of the said discharge thorn is changed in steps toward the depth direction from the said entrance part of the said dust collection area.

When there is no discharge, there is an effect of contraction at the inlet of the dust collection area, and under conditions where the pressure loss is low, the gas flow rate distribution is said to be significantly lower than the inlet side, compared with the gas flow rate distribution. Arise. In the dust collector of the present invention, an ion wind is generated by generating a corona discharge between the discharge thorn of the discharge electrode and the ground electrode. In the first aspect, this ion wind is used, and the ion flow is superimposed on the gas flow rate to increase the gas flow rate. The strength of the ion wind is stronger as the distance between the discharge splinter and the ground electrode is closer. For this reason, by increasing the discharge spike on the inlet side where the gas flow rate is low, a flow rate distribution of the ion wind opposite to the gas flow rate distribution when there is no discharge is generated.
Moreover, the uncharged particulate matter contained in the gas flowing into the dust collection area can be charged by corona discharge in the dust collection area.
As a result, in the dust collector of the first aspect, the gas flow rate passing through the filter can be made substantially uniform, and the collection efficiency (dust collection efficiency) of the particulate matter contained in the gas can be increased. .

According to a second aspect of the present invention, there is provided a dust collection area having an inlet portion into which gas is introduced, a mounting shaft installed in the dust collection area, and a plurality of thorn-shaped discharge spikes protruding from the mounting shaft. A plurality of discharge electrodes, and an opening through which the gas can flow, an earth that is substantially perpendicular to the direction in which the discharge spike extends, and that constitutes the wall surface of the dust collection area facing the tip of the discharge spike An electrode, a filter installed outside the ground electrode, through which the gas in the dust collection area passes, and a clean gas passage located on the gas downstream side of the dust collection area through the ground electrode and the filter; A power source for applying a voltage to the discharge electrode, and the mounting shaft of each of the discharge electrodes extends in a direction substantially perpendicular to a direction in which the gas flows into the dust collection area, and a plurality of the discharge electrodes The electrode is in the dust collection area. The filter arranged in the depth direction from the entry port and located on the back side of the dust collection area is thicker than the filter located on the entrance of the dust collection area, and the discharge thorn and the ground electrode It is a dust collector that generates corona discharge.

As described above, a gas flow velocity distribution is generated in which the flow velocity of the gas passing through the filter is significantly lower than that at the back of the inlet portion. In the second aspect, the filter located on the far side of the dust collection area is made thicker than the filter located on the entrance side, thereby increasing the pressure loss of the far side filter and reducing the gas flow rate.
In the second aspect, the gas passing through the filter can be accelerated and the uncharged particulate matter contained in the gas flowing into the dust collection area can be charged by corona discharge in the dust collection area.
As a result, in the dust collector of the second aspect, the gas flow rate passing through the filter can be made substantially uniform, and the collection efficiency of the particulate matter contained in the gas can be increased.

In the first and second aspects, the conductive material is surrounded by a conductive enclosure protruding from the end of the earth electrode on the inlet side toward the outside of the dust collection area, and the side opposite to the inlet side is open. Preferably, the gas can flow inward, and the discharge electrode of the discharge electrode has a precharge portion provided to face the enclosure.
Before the particulate matter flows into the dust collection area, the precharge unit charges the particulate matter in advance. When the precharge unit is installed, the charging time of the particulate matter becomes longer than in the case of only the dust collection area, and the particulate matter that reaches the filter in an uncharged state is reduced. As a result, dust collection efficiency increases.

In the first and second aspects, a plurality of the dust collection areas are arranged in a direction substantially orthogonal to the gas inflow direction, the clean gas passage is disposed between the adjacent dust collection areas, and the dust collection area It is preferable that the width of the clean gas passage in the direction in which the dust collection is arranged is equal to or less than the width in the dust collection area in the direction in which the dust collection area is arranged.

It is preferable to provide a plurality of dust collection areas because dust collection efficiency can be improved. On the other hand, there is a concern about increasing the size of the dust collector. In the case of providing a plurality of dust collection areas, if the width in the dust collection area and the width of the clean gas passage are set as described above, the apparatus can be made compact while having high dust collection efficiency. .

1st and 2nd aspect WHEREIN: It is preferable that the washing | cleaning part which supplies the liquid for wash | cleaning the said filter is installed above the said filter.

By adopting such a configuration, the filter can be washed as appropriate, so that a reduction in the collection efficiency of the particulate matter by the filter can be suppressed.

A third aspect of the present invention is a dust collection method for collecting particulate matter from a gas containing particulate matter and water mist using the dust collector of the first aspect or the second aspect, The step of applying a voltage to the discharge electrode by the power source to generate an ion wind from the discharge electrode to the ground electrode, and charging the particulate matter contained in the gas in the dust collection area; And collecting the charged particulate matter with the filter by passing the gas through the filter.

The gas to be treated in the present invention includes particulate substances of various sizes. Particulate matter larger than the pores of the filter is collected by the filter as the gas passes through the filter. On the other hand, particulate matter having a particle size equal to or smaller than the pores of the filter can be collected by the filter by being mainly charged in the dust collection area.
If the dust collector of the 1st aspect or the 2nd aspect is utilized, the gas flow rate which passes a filter can be made substantially uniform. As a result, the collection efficiency of the particulate matter contained in the gas increases.

According to the present invention, since the gas flow velocity distribution in the dust collection area can be made uniform, the collection efficiency in one dust collection area can be improved. As a result, the volume of the apparatus can be reduced, and the size can be reduced.

It is a perspective view of the collection part of the dust collector which concerns on 1st Embodiment. It is front sectional drawing of the collection part of the dust collector which concerns on 1st Embodiment. It is side surface sectional drawing of the collection part of the dust collector which concerns on 1st Embodiment. It is front sectional drawing of the collection part of the modification of 1st Embodiment. It is the profile of the gas flow rate which passes a filter, when gas is made to flow into a dust collection area in the state where discharge is not performed. It is front sectional drawing of the collection part of another modification of 1st Embodiment. It is front sectional drawing of the collection part of another modification of 1st Embodiment. It is a graph explaining the charge amount of the particulate matter by a precharge part. It is front sectional drawing of the collection part of the dust collector which concerns on 2nd Embodiment. It is a perspective view of the collection part of the dust collector which concerns on 3rd Embodiment. It is front sectional drawing of the collection part of the dust collector which concerns on 3rd Embodiment. It is side surface sectional drawing of the collection part of the dust collector which concerns on 3rd Embodiment. It is a perspective view of the collection part of the dust collector which concerns on 4th Embodiment. It is front sectional drawing of the collection part of the dust collector which concerns on 4th Embodiment. It is side surface sectional drawing of the collection part of the dust collector which concerns on 4th Embodiment.

<First Embodiment>
The dust collector according to the first embodiment is installed in an exhaust gas treatment facility provided in a flue on the downstream side of an industrial combustion facility such as a coal-fired or heavy oil-fired power plant or an incinerator, for example. In addition to industrial combustion equipment, the dust collector can be used for air purification equipment filters (for example, clean room air conditioning filters, virus removal filters, etc.).

In the dust collector according to the first embodiment, a water mist spraying device and a collection unit are installed in order from the upstream side of the gas. When a sufficient amount of water mist is contained in the gas and flows into the dust collector, the water mist spraying device can be omitted.

The water mist spraying device sprays water mist into the gas from the nozzle. The diameter of the water mist is about 10 μm to 100 μm, preferably 30 μm or less. The liquid sprayed from the water mist spraying device may be an aqueous solution containing a dissolved salt capable of absorbing an acidic gas such as SOx contained in the gas in addition to water. For example, a caustic soda (NaOH) aqueous solution and a magnesium hydroxide (Mg (OH) ₂ ) aqueous solution are used.

In addition, when the dust collector of this embodiment is applied to the dust collector which implements environmental dust collection, the water mist spraying device can also spray water containing ethanol or ozone water as a liquid having a disinfecting action. . When environmental dust collection is performed, fungi and viruses may exist in the air. These are inactivated to some extent by corona discharge in the precharged part, but can be more reliably inactivated in the downstream collecting part by spraying a liquid having a disinfecting action.

FIG. 1A is a perspective view of the collection unit 1 as viewed from below, FIG. 1B is a front sectional view of the collection unit 1, and FIG. 1C is a side sectional view of the collection unit 1. The dust collector of the present embodiment is configured such that gas rises in the vertical direction from below the collection unit 1 and flows into the collection unit 1.

The collection unit 1 has a plurality (three in FIG. 1A) of dust collection areas 2. The dust collection area 2 is arranged in parallel with the gas flow.

Each dust collection area 2 has an inlet 3 through which gas can flow. The surface located on the opposite side to the inlet portion 3 is a wall surface 4 through which gas cannot pass. The inlet portion 3 and the wall surface 4 have the same shape. That is, the cross-sectional shape facing the direction in which the gas flows in the dust collection area 2 has the same area from the inlet 3 toward the depth direction. In FIG. 1A, the inlet 3 is oval, but is not limited thereto.

A wall surface in a direction substantially orthogonal to the inlet 3 of the dust collection area 2 is a ground electrode 5. The ground electrode 5 is a conductive member having an opening through which gas can flow, and is, for example, a wire mesh or a punching metal.

A filter 6 is installed around the outside of the ground electrode 5. The filter 6 is a dielectric material having a dielectric constant exceeding that of air (desirably having a dielectric constant of 2 or more). As the filter 6, a porous material having water repellency and allowing gas to flow is selected. Examples thereof include a porous material made of polypropylene or polytetrafluoroethylene. The filter 6 preferably has a low pressure loss (initial pressure loss of 10 to 20 mmAq, at least about 30 mmAq or less). The pores of the filter 6 have a passing particle diameter of several μm to several tens of μm, and the porosity is 90% or more, preferably 95% or more.

In the entrance 3 of the dust collection area 2, a wall surface 8 (however, omitted in FIG. 1A) is installed between adjacent dust collection areas 2. The space upstream of the gas in the dust collection area 2 and the clean gas passage 17 that is located on the gas downstream side of the dust collection area 2 with the ground electrode 5 and the filter 6 interposed therebetween are isolated by the wall surface 8. .

The collection unit 1 includes a pipe (cleaning unit) 7 for supplying a liquid for cleaning the filter 6 on the upper side of the filter 6. In the example shown in FIGS. 1A and 1B, two pipes 7 are installed along the long axis direction of the filter 6 formed in an oval shape. If the liquid can be supplied to the filter 6 from above the filter 6, the installation position and the number of the pipes 7 are not particularly limited.
The cleaning liquid is mainly water, but when collecting viruses and fungi, ethanol, ozone water, etc. are used to inactivate the collected viruses and fungi and disinfect the filter. Substances having a disinfecting effect may be included.
In FIGS. 1A to 1C, the cleaning unit is a pipe, but a configuration in which a plurality of spraying devices are arranged may be employed.

A drain (not shown) for receiving the liquid flowing from the filter is installed below the filter 6.

If a water mist spraying device is provided on the gas upstream side of the collecting unit 1 and a sufficient amount of water mist for washing can be made to fly from the water mist spraying device to the collecting unit 1, the piping 7 may be omitted. good.

A plurality of discharge electrodes 10 are accommodated in each dust collection area 2. Each discharge electrode 10 has an attachment shaft 11 and a plurality of discharge spikes 12 protruding from the attachment shaft 11 in a direction substantially perpendicular to the extending direction of the attachment shaft 11. The attachment shaft 11 extends in a direction substantially perpendicular to the gas inflow direction to the dust collection area 2. The discharge thorn 12 extends from the mounting shaft 11 in a direction substantially orthogonal to the ground electrode 5 so that the tip thereof faces the ground electrode 5. In the dust collection area 2 having an oval cross section shown in FIG. 1A, the mounting shaft extends in the major axis direction of the oval so that the number of discharge thorns 12 facing the ground electrode 5 increases. The discharge thorn 12 extends in the gas inflow direction to the dust collection area 2.
As shown in FIGS. 1B and 1C, in the dust collection area 2, the discharge electrodes 10 are arranged in the depth direction of the dust collection area 2 from the inlet 3.

The discharge electrode 10 and the ground electrode 5 are connected by a power source (not shown).
Within one dust collection area 2, the mounting shafts 11 of the discharge electrodes 10 constitute a group electrically connected in parallel by a discharge electrode support member 13. Between the plurality of dust collection areas 2, the group of discharge electrodes 10 is further connected in parallel by a discharge electrode support member 13. Outside the dust collection area 2, the discharge electrode support 13 is connected to a power source via an insulator 14. On the wall surface 4 located on the side opposite to the inlet 3, the discharge electrode support 13 is taken out of the dust collection area 2 through the opening 15. Between the opening 15 and the insulator 14, the discharge electrode support 13 is covered with a pipe 16 and is isolated from the external space.

The length of the discharge barb of the discharge electrode 10 located on the inlet part 3 side is longer than the discharge barb of the discharge electrode located on the far side of the dust collection area 2 (the side opposite to the inlet part 3). In FIG. 1B, the length of the discharge thorn 12 is changed step by step from the inlet 3 toward the back side of the dust collection area 2.

FIG. 2 is a view for explaining a modification of the collection unit of the present embodiment, and is a front sectional view of the collection unit. In the modification of FIG. 2, the length of the discharge barb 32 protruding from the mounting shaft 31 of the discharge electrode 30 is changed in two steps from the inlet 3 of the dust collection area toward the back side. The configuration of the collection unit 21 of the modification is the same as that of FIGS. 1A to 1C except for the discharge thorn 32. In FIG. 2, the piping for cleaning is omitted.

A dust collection method for removing particulate matter contained in gas using the dust collector of this embodiment will be described. Below, the case where a water mist spraying apparatus is provided is mentioned as an example.

The particulate matter contained in the gas varies depending on the device to which the dust collector is connected. For example, when connected to a combustion facility such as a boiler, suspended dust is contained in the gas as particulate matter. When a wet type flue gas desulfurization device is installed in the flow path (flue) upstream of the dust collector, an aqueous solution containing an SOx absorbent at the absorption tower inlet of the flue gas desulfurization device and inside the absorption tower Is sprayed. The absorbent is, for example, magnesium hydroxide or sodium hydroxide (caustic soda). When the absorbent and SOx react with each other, sulfate is generated, and if it is in a high-temperature gas that does not reach the saturated water concentration, the water is evaporated from the droplets of the aqueous solution and a part of the dissolved salt is precipitated. Accordingly, the gas contains dissolved salt fine particles as particulate matter. Moreover, some of the sprayed droplets flow into the dust collector without being evaporated. SOx (SO ₂ , SO ₃ ) is taken in the non-evaporated droplet (mist). Hereinafter, the mist that incorporates SOx is referred to as “SOx mist”.
In addition, when the dust collector of 1st Embodiment is applied to environmental dust collection, the floating dust containing a virus and fungi is contained as a particulate matter.

¡Gas containing particulate matter flows into the dust collector. When installing the water mist spraying device, the water mist spraying device sprays the water mist into the gas before the gas containing the particulate matter flows into the collecting unit 1.

The diameter of the sprayed water mist in this embodiment is about 10 μm to 100 μm, preferably 30 μm or less. The liquid sprayed from the water mist spraying device may be an aqueous solution containing a dissolved salt capable of absorbing an acidic gas such as SOx contained in the gas in addition to water. For example, a caustic soda (NaOH) aqueous solution and a magnesium hydroxide (Mg (OH) ₂ ) aqueous solution are used.

In addition, when the dust collector of this embodiment is applied to environmental dust collection, the water mist spraying device can also spray water containing ethanol or ozone water as a liquid having a disinfecting action. When environmental dust collection is performed, fungi and viruses may exist in the air. By spraying a liquid having a disinfecting action, it is possible to reliably inactivate the downstream collecting unit 1.

A power source (not shown) applies a voltage to the discharge electrode 10. As a result, a voltage difference is generated between the discharge electrode 10 and the ground electrode 5, and a corona discharge is generated between the discharge barb 12 of the discharge electrode 10 and the ground electrode 5.
The gas containing particulate matter flows into the dust collection area 2 of the collection unit 1. The gas passes through the opening of the ground electrode 5 and the filter 6 and flows into the clean gas passage 17. The gas that has passed through the filter 6 is discharged to the outside of the dust collector through the clean gas passage 17. While the gas is flowing through the dust collection area 2, the particulate matter is charged by corona discharge.
The particulate matter contained in the gas has various particle sizes. When the gas passes through the filter 6, particulate matter that is about the same as or larger than the pore diameter of the filter 6 described above cannot be passed through the pores and is collected by the filter 6. On the other hand, fine particulate matter of, for example, a submicron size is smaller than the pore diameter of the filter 6 and therefore passes through the filter 6 unless charged. Therefore, by charging the particulate matter with the discharge electrode 10 in the dust collection area 2, when the gas passes through the filter 6, the fine particulate matter is collected on the surface of the filter 6 and removed from the gas.

Here, ion wind is generated from the tip of the discharge thorn 12 toward the ground electrode 5 by corona discharge. In the collection unit 1 of the present embodiment, the gas passing through the filter 6 has a flow velocity of about 0.5 to 1 m / s, but the ion wind is about 2.5 m / s. By injecting the gas in a discharged state, as shown in FIG. 3, the influence of the ion wind is superimposed on the gas flow caused by the shape of the dust collection area, and the gas flow rate is increased.

FIG. 3 shows the result of simulating the flow rate of the gas passing through the filter 6 when the gas is allowed to flow into the dust collection area 2 without discharging. In the figure, the horizontal axis represents the length ratio of the filter 6 (based on the length of the dust collection area 2 in the depth direction from the inlet 3), and the vertical axis represents the flow rate ratio of the gas passing through the filter 6 (gas passing through the filter 6). The average flow rate of The profile of FIG. 3 shows the results when the resistance coefficient (ie, pressure loss) of the filter 6 is changed between 30 and 160 mmAq.

Since the gas becomes a contracted flow at the inlet 3, the amount of gas passing through the filter 6 is small, and the passage flow velocity is greatly reduced as compared with other positions. The flow velocity of the gas passing through the filter 6 increases as it goes to the back side of the dust collection area 2. The difference in the passage flow velocity between the inlet 3 side and the back side increases as the filter 6 has a low pressure loss as in this embodiment.

The flow velocity of the ion wind is proportional to the square root of the corona current. When the voltage V is applied between the discharge electrode 10 and the earth electrode 5, the electric field strength E between the tip of the discharge barb 12 and the earth electrode 5 is expressed by the following equation.
E = V / l (1)
In the formula (1), l is the distance between the tip of the discharge thorn 12 and the ground electrode 5. From equation (1), the longer the discharge thorn 12, the greater the electric field strength. For this reason, the corona current increases and the ion wind speed increases.

In the collection unit 1 of the present embodiment, the gas flowing into the dust collection area 2 has a flow velocity of about 0.5 to 1 m / s, but the ion wind is about 2.5 m / s. By injecting the gas in a discharged state, the influence of the ion wind is superimposed on the gas flow caused by the shape of the dust collection area 2 as shown in FIG. If the length and the number of steps of the discharge thorn are appropriately set, the flow velocity of the gas passing through the filter 6 can be made substantially uniform in the depth direction of the dust collection area 2. Specifically, the discharge spike is lengthened in the region where the gas flows slowly without discharging, and the discharge spike is shortened in the region where the gas flows early.

For example, in FIG. 3, an inflection point (filter length ratio is about 0.1) appears in the vicinity of the inlet 3 in the flow velocity ratio. Based on this knowledge, the discharge electrode 30 in FIG. 2 sets the length of the discharge thorn 72 in two stages with the position corresponding to the inflection point of the passage flow velocity of the filter as a boundary.

The length of the discharge thorn is set according to the formula (1) or the like in consideration of the size of the ion wind necessary for making the flow velocity of the gas passing through the filter substantially uniform. However, it is not preferable that the tips of the discharge spikes 12 and 32 are too close to the ground electrode 5 because a problem such as generation of a spark occurs.

When arranging a plurality of the dust collecting area as shown in FIGS. 1A and 1B, L ₁ the width of the dust collecting area 2 arrangement _direction, the distance between adjacent dust-collecting area When L _2, L ₁ ≧ L ₂ It is preferable that L ₁ needs to be about 100 mm in order to secure a space necessary for collecting dust and a space for accommodating the discharge electrode to obtain sufficient dust collection efficiency, and about 200 mm in the case of a large dust collector. However, L ₁ is difficult to change due to the device design. Therefore, the smaller the L _2, can be made compact device. Alternatively, the dust collection area can be expanded, improving the dust collection efficiency. For example, if L ₂ is ½ of L ₁ with the same device volume, it will lead to the installation of a 4 / 3-fold filter. However, the pressure loss at the inlet portion 3 when L ₂ is decreased is increased, the amount of gas passing through the filter 6 in the vicinity of the inlet portion 3 is reduced. Considering the above matters, L _{2 with} respect to L ₁ is preferably ½ or more and less than 1.

The SOx mist contained in the gas is removed from the gas by adhering to the filter 6 when the gas passes through the filter 6 or by being collected by water mist. The water mist that has collected the SOx mist is collected by the filter 6 when the gas passes through the filter 6. The spray amount and spray time of the water mist are preferably set as appropriate so that the SOx mist can be collected efficiently. For example, the water mist spraying need not be performed continuously, and the water mist spraying and stopping may be repeated every predetermined time. Alternatively, the water mist spray amount and the spray amount may be controlled by monitoring the water mist and SOx mist amount in the exhaust gas flowing into the filter 6.
In addition, as above-mentioned, spraying of water mist is not essential in this embodiment. Even when the water mist is not sprayed, the SOx mist can be sufficiently removed by being collected by the filter 6.

When the amount of water mist and SOx mist adhering to the filter 6 increases, the mists aggregate to form large droplets. When the droplet becomes large to some extent, the droplet flows down to the lower part of the filter 6 due to gravity while capturing the particulate matter. In this way, the filter 6 is cleaned by spraying water mist. The dropped liquid droplets are discharged out of the dust collector through the drain. In this process, particulate matter and SOx collected by the filter 6 are also discharged.
Further, when water mist is sprayed, the water mist adheres to the surface of the discharge electrode 10. When the amount of adhesion increases, the mists aggregate to form large droplets that flow down from the discharge electrode 10. Thus, the discharge electrode 10 is also cleaned by spraying water mist.

The filter 6 is washed after a predetermined time has elapsed or when the dust collection efficiency of the filter 6 has decreased. When a plurality of dust collection areas 2 are installed, cleaning of all the dust collection areas 2 may be performed, or cleaning may be performed for each predetermined number of dust collection areas 2. In the dust collection area corresponding to the filter 6 to be cleaned, the corona discharge from the discharge thorn 12 may be stopped.

When cleaning the filter 6, a cleaning liquid is directly supplied from the pipe 7 to the filter 6. It is removed from the filter 6 and discharged from the drain. The filter 6 is periodically cleaned. The liquid supply method at the time of washing may be continuous or intermittent.

When a plurality of dust collection areas 2 are installed, the gas flow rate to the dust collection area 2 corresponding to the filter 6 to be cleaned is reduced or the gas flow is interrupted. Further, corona discharge in the dust collection area 2 corresponding to the filter 6 to be cleaned is stopped.
The gas flow rate is changed and shut off by installing a flow rate control mechanism such as a damper at the inlet 3. Alternatively, a cleaning liquid is supplied from the pipe 7 to form a liquid film on the surface of the filter 6, and the filter 6 is cleaned while blocking the gas flow.

When spraying water mist, since the filter 6 is cleaned with water mist as described above, the above-described cleaning need not be performed. That is, when the water mist spraying device is installed, the pipe 7 may not be installed.

FIG. 4A is a diagram illustrating a modification of the collection unit of the present embodiment, and is a front cross-sectional view of the collection unit 41. In FIG. 4A, the precharge part 42 is installed in the entrance part 3 outer side of the dust collection area 2. FIG. The precharge portion 42 is surrounded by an enclosure 43 that protrudes from the end of the ground electrode 5 on the inlet portion 3 side toward the outside of the dust collection area 2. In FIG. 4, the enclosure 43 is the one in which the ground electrode 5 protrudes from the dust collection area 2 toward the gas upstream side (toward the outside of the dust collection area 2). Therefore, the enclosure 43 is a conductive member having an opening through which gas can flow, like the ground electrode 5. The precharge part 42 has an opening on the side opposite to the inlet part 3, and gas can flow into the dust collection area 2 through the precharge part 42. The opening on the gas upstream side of the precharge portion 42 has the same shape as the inlet portion 3 of the dust collection area 2.

The enclosure 43 may be formed of a conductive plate (that is, a plate that does not have an opening through which gas can flow).

In the precharge portion 42, the discharge electrode 50 has a discharge thorn 52. When a voltage is applied to the discharge electrode 50, a corona discharge occurs between the discharge thorn 12 and the ground electrode 5 in the dust collection area 2, and between the discharge thorn 52 and the enclosure 43 in the precharge portion 42. Corona discharge occurs. In FIG. 4A, the charging time of the particulate matter is increased by the amount of the precharge portion 42. As a result, the particulate matter can be charged before the particulate matter reaches the filter 6.
When the precharge part 42 is not installed, there is a possibility that the particulate matter is insufficiently charged in the vicinity of the inlet part 3. For this reason, in the filter 6 near the inlet 3, fine particulate matter of about submicron passes through the filter 6 without being collected. As a result, the dust collection efficiency is lowered. The precharge unit 42 has a function of performing preliminary charging before the gas flows into the dust collection area 2 in order to compensate for the shortage of the charged amount of the particulate matter in the vicinity of the inlet 3. By installing the precharge portion 42, the dust collection efficiency of the filter 6 near the inlet portion 3 is improved, so that the dust collection efficiency of the entire dust collector is improved.

FIG. 4B is a diagram illustrating a modification of the collection unit of the present embodiment, and is a front sectional view of the collection unit 44. 4B is provided with a precharge portion 45 having a shape different from that in FIG. 4A.
The enclosure 46 of the precharge unit 45 is integrated with the enclosure of the precharge unit of the adjacent dust collection area 2. The enclosure 46 is curved so that the opening on the gas upstream side of the precharge portion 45 is wider than the inlet portion 3 of the dust collection area 2. By setting it as such a shape, a rectification effect can be improved.

FIG. 5 is a simulation result of the charge amount when submicron particles are charged in the precharge portion. In the figure, the horizontal axis represents the residence time of the particulate matter in the precharge section, and the vertical axis represents the charge amount at the dust collection area inlet section 3. FIG. 5 shows the results when the concentration of particulate matter in the gas is 130 mg / m ³ N.
According to FIG. 5, the charge amount tends to increase until the residence time is 10 msec, regardless of the size of the particles. However, if it exceeds 10 msec, the charge amount is saturated even if the residence time is extended, and therefore it can be said that an increase in charge amount that can contribute to performance improvement cannot be expected. Under the conditions shown in FIG. 5, the residence time in the precharge section is preferably 5 to 10 msec.

When the concentration of the particulate matter in the gas is lower than the condition of FIG. 5 (130 mg / m ³ N), since the charged current easily flows, the particulate matter is easily charged. For this reason, the charge amount tends to increase as the residence time becomes longer, but an inflection point of the charge amount appears around the residence time of 10 msec.
In addition, when the concentration of the particulate matter in the gas is higher than the condition of FIG. 5, it becomes difficult for the charging current to flow between the discharge electrode 10 and the ground electrode 5 due to the effect of the space charge effect, and in a shorter time. The charge amount is saturated (in a time shorter than 10 msec).

The precharge unit compensates for the charge of the particulate matter in the gas passing through the filter 6 in the vicinity of the inlet 3, but if the particulate matter is charged to some extent, the filter 6 in the vicinity of the inlet 3 is fine. Efficient particulate matter can be collected efficiently. Therefore, when the density is lower than the above-described condition of FIG. 5, even if a charging time longer than the inflection point of the charge amount is secured, it does not contribute to a significant improvement in dust collection performance. Similarly, even when the concentration is higher than the condition of FIG. 5, even if a residence time exceeding 10 msec is secured, it does not contribute to performance improvement. From this, regardless of the concentration of the particulate matter in the gas, if a residence time of 5 to 10 msec is secured in the precharge portion, a predetermined performance can be obtained.

The length of the precharge section enclosure in the gas flow direction may be designed in consideration of the residence time and gas flow rate described above.

Second Embodiment
The dust collector according to the second embodiment can also be used for exhaust gas treatment equipment, filters for air purification equipment, and the like.
FIG. 6 is a schematic diagram illustrating the collection unit of the dust collector according to the second embodiment, and is a front cross-sectional view of the collection unit 61. A perspective view and a side sectional view of the collection part 61 are substantially the same as those in FIGS. 1A and 1C.

In the second embodiment, the filter 66 is thicker on the inner side in the gas inflow direction of the dust collection area 62 than on the inlet 63 side. Further, the discharge barbs 72 of the discharge electrode 70 have substantially the same length. Other configurations are the same as those in the first embodiment.

A dust collection method for removing particulate matter contained in gas using the collection unit of the second embodiment will be described.
A power source (not shown) applies a voltage to the discharge electrode 70. Thereby, a corona discharge is generated between the discharge barb 72 of the discharge electrode 70 and the ground electrode 65. In addition, a voltage difference is generated between the discharge electrode 70 and the ground electrode 65.

Gas containing particulate matter flows into the dust collection area 62 of the collection unit 61. Particulate matter is charged by corona discharge. The gas passes from the dust collection area 62 through the filter 66 and flows into the clean gas passage 17 and is discharged to the outside of the dust collector. In this process, the charged particulate matter is collected by the filter 66 as in the first embodiment.

Also in the present embodiment, ion wind is generated by corona discharge to accelerate the gas flow rate. However, since the length of the discharge thorn 72 of the discharge electrode 70 is substantially the same, the size of the ion wind is substantially the same within the dust collection area 62. However, in the second embodiment, the flow rate of gas passing through the filter 66 is made uniform by changing the thickness of the filter 66. That is, as shown in FIG. 3, the gas flow rate increases as it goes in the depth direction when viewed from the inlet 63 of the dust collection area 62. When the filter 66 is thickened, the flow rate of the gas passing through the filter 66 is reduced due to pressure loss. As a result, the flow velocity of the gas passing through the filter 66 can be made substantially uniform in the depth direction of the dust collection area 62.

In the present embodiment, the thickness of the filter 66 and the number of steps for changing the thickness are not particularly limited. As shown in FIG. 3, the thickness of the filter 66 and the number of stages for changing the thickness are set in consideration of the flow velocity profile when the filter having a uniform thickness is provided, the gas flow velocity necessary for collection, and the like. The For example, the thickness of the filter 66 is set in two stages with the position corresponding to the inflection point of the passage flow rate ratio found in the vicinity of the inlet portion 63 in the profile of FIG.

<Third Embodiment>
A dust collector according to a third embodiment will be described with reference to the drawings.
The dust collector according to the third embodiment can be used for an exhaust gas treatment facility, an air purification facility filter, and the like. The dust collector of this embodiment may also be provided with a water mist spraying device as necessary.

FIG. 7A is a perspective view of the collection unit 81 of the dust collector of the third embodiment, FIG. 7B is a cross-sectional view of the collection unit 81 viewed from the upper surface side, and FIG. 7C is a side view of the collection unit 81. It is sectional drawing. The same components as those in FIGS. 1A to 1C are denoted by the same reference numerals.

In the third embodiment, the gas flows into the collecting unit 81 from a substantially horizontal direction. A precharge unit 82 is provided in the collection unit 81 shown in FIGS. 7A to 7C. The precharge unit 82 is the same as that described in the first embodiment.

In the third embodiment, one pipe 83 is installed as a cleaning unit above the filter 6, and a cover 84 is installed between the filter 6 and the pipe 83. The cover 84 is not particularly limited as long as the cleaning liquid can be supplied substantially uniformly to the filters 6 on both sides of the pipe 83. For example, in FIG. 7A, the cover 84 is a plate material having an arc-shaped cross section.
In FIGS. 7A to 7C, the piping is illustrated as the cleaning unit, but a configuration in which a plurality of spraying devices are arranged may be employed.

A drain 85 that receives liquid flowing from the filter is installed below the filter 6. The drain 85 is connected to a seal pot 86 outside the dust collector through a drain pipe. The seal pot 86 and the pipe 83 are connected through a pump (not shown).

When the dust collector of the third embodiment is used, the particulate matter is charged and collected as in the first embodiment. 7A to 7C, the liquid droplets that have flowed down from the filter 6 during operation are stored in the seal pot 86 through the drain 85.

When cleaning the filter 6, a pump (not shown) is operated, and the liquid in the seal pot 86 is supplied to the pipe 83. The cleaning liquid discharged from the pipe 83 falls along the cover 84 from the upper part of the filter 6 toward the filter 6. The cleaning liquid that has passed through the filter 6 is stored again in the seal pot 86 through the drain 85.

7A to 7C show an example in which the length of the discharge thorn 12 of the discharge electrode 10 is changed step by step in the depth direction of the dust collection area 2 one by one. The present embodiment is not limited to this, but the configuration in which the length of the discharge thorn is changed stepwise as shown in FIG. 2 or the thickness of the filter without changing the length of the discharge thorn as shown in FIG. It is possible to adopt a configuration in which is changed.

<Fourth embodiment>
A dust collector according to a fourth embodiment will be described with reference to the drawings.
The dust collector according to the fourth embodiment can be used for an exhaust gas treatment facility, an air purification facility filter, and the like. The dust collector of 4th Embodiment may also be provided with the water mist spraying apparatus as needed.

FIG. 8A is a perspective view of the collection unit 91 of the dust collector of the fourth embodiment, FIG. 8B is a cross-sectional view of the collection unit 91 viewed from the upper surface side, and FIG. 8C is a side view of the collection unit 91. It is sectional drawing. In the fourth embodiment, the gas flows into the collection unit 91 from a substantially horizontal direction. 8A to 8C, the same components as those in FIGS. 7A to 7C are denoted by the same reference numerals.

The collection part 91 of the dust collector of the fourth embodiment is also provided with a ground electrode 95 and a filter 96 on the side opposite to the inlet part 93 of the dust collection area 92. In FIG. 8A, the ground electrode 95 and the filter 96 on the side facing the inlet 3 have a curved shape. The filter 96 on the side opposite to the inlet 3 has a higher pressure loss than the filter 66 in the other part. For example, the filter 96 is thicker than other parts of the filter.

In the discharge electrode 100 of FIG. 8B, the length of the discharge barb 102 of the discharge electrode 100 is changed step by step in the depth direction of the dust collection area 2 as described in the first embodiment. In the fourth embodiment, the discharge electrode 100 includes a discharge bar 102 a that protrudes from the tip of the mounting shaft 101 toward the ground electrode 95.

In FIG. 8A, two pipes 97 for cleaning the filter 96 are arranged in the upper part of the filter 96 along the depth direction of the dust collection area 2. However, if the filter 96 can be cleaned, the arrangement and shape of the pipe 97 are not limited to those shown in FIG. 8A. The pipe 97 can be replaced with a configuration in which spraying devices such as sprays are arranged.
In FIG. 8A, for convenience of explanation, the upper side of the filter 96 is shown as being open. Since it is actually necessary to pass the gas through the filter 96, a wall through which no gas can flow is installed above the filter 96.

When the dust collector of the fourth embodiment is used, the particulate matter is charged and collected as in the first embodiment.
In the present embodiment, corona discharge also occurs between the ground electrode 95 located on the side opposite to the inlet 3 and the discharge thorn 102a. If the ground electrode 95 has a curved shape as shown in FIG. 8A, it is possible to design a constant distance from the discharge thorn 102a, and stable corona discharge can be generated.
When the thickness of the filter is uniform in the configuration of the present embodiment, the amount of gas permeation through the filter 96 facing the dust collection area 2 increases. Therefore, if the pressure loss of the filter 96 facing the dust collection area 2 is increased as in the present embodiment, the gas flow rate in the filter 96 is reduced. As a result, the gas passage amount can be made substantially uniform throughout the filter.

8A to 8C show an example in which the length of the discharge thorn 102 is changed step by step in the depth direction of the dust collection area 2. The present embodiment is not limited to this, and it is possible to adopt a configuration in which the length of the discharge thorn is changed stepwise as shown in FIG. Moreover, the structure by which the thickness of the filter is changed like FIG. 6 is employable. In this case, for example, for the filter 6 parallel to the gas inflow direction, the filter 6 is made thicker as it goes in the depth direction of the dust collection area 2, and the filter 96 is installed thicker than the innermost filter 6.

1, 2, 41, 44, 61, 81, 91

Collection part

2, 62, 92

Dust collection area

3, 63, 93

Entrance part

4, 8

Wall surface

5, 65, 95

Ground electrode

6, 66, 96

Filter

7, 83, 97

Piping

10, 30, 50, 70, 100

Discharge electrode

11, 31, 101 Mounting

shaft

12, 32, 52, 72, 102 Discharge bar 13 Discharge electrode support 14 Insulator 15 Opening 16 Pipe 17

Clean gas passage

42 , 45, 82

Precharge unit

43, 46 Enclosure 84 Cover 85 Drain 86 Seal pot

Claims

A dust collection area having an inlet for introducing gas;
A plurality of discharge electrodes installed in the dust collection area and having a mounting shaft and a plurality of thorn-shaped discharge spikes protruding from the mounting shaft;
An earth electrode having an opening through which the gas can flow, substantially perpendicular to an extending direction of the discharge thorn, and constituting a wall surface of the dust collection area facing a tip of the discharge thorn;
A filter installed outside the ground electrode, through which the gas in the dust collection area passes,
A clean gas passage located on the gas downstream side of the dust collection area through the ground electrode and the filter;
A power source for applying a voltage to the discharge electrode,
The mounting shaft of each of the discharge electrodes extends in a direction substantially orthogonal to the direction in which the gas flows into the dust collection area,
The plurality of discharge electrodes are arranged in a depth direction from the entrance of the dust collection area,
The length of the discharge thorn of the discharge electrode located at the entrance of the dust collection area is longer than the length of the discharge thorn of the discharge electrode located on the back side of the dust collection area,
A dust collector that generates a corona discharge between the discharge thorn and the ground electrode.
The dust collector according to claim 1, wherein the length of the discharge thorn is changed stepwise from the entrance of the dust collection area toward the depth direction.
A dust collection area having an inlet for introducing gas;
A plurality of discharge electrodes installed in the dust collection area and having a mounting shaft and a plurality of thorn-shaped discharge spikes protruding from the mounting shaft;
An earth electrode having an opening through which the gas can flow, substantially perpendicular to an extending direction of the discharge thorn, and constituting a wall surface of the dust collection area facing a tip of the discharge thorn;
A filter installed outside the ground electrode, through which the gas in the dust collection area passes,
A clean gas passage located on the gas downstream side of the dust collection area through the ground electrode and the filter;
A power source for applying a voltage to the discharge electrode,
The mounting shaft of each of the discharge electrodes extends in a direction substantially orthogonal to the direction in which the gas flows into the dust collection area,
The plurality of discharge electrodes are arranged in a depth direction from the entrance of the dust collection area,
The filter located on the back side of the dust collection area is thicker than the filter located at the inlet of the dust collection area,
A dust collector that generates a corona discharge between the discharge thorn and the ground electrode.
Surrounded by a conductive enclosure projecting from the end of the ground electrode on the inlet side toward the outside of the dust collection area, the side opposite to the inlet side opens and the gas can flow inward. 4. The dust collector according to claim 1, further comprising a precharge portion provided with the discharge thorn of the discharge electrode facing the enclosure. 5.
A plurality of the dust collection areas are arranged in a direction substantially orthogonal to the inflow direction of the gas,
The clean gas passage is disposed between adjacent dust collection areas;
5. The collection according to claim 1, wherein a width of the clean gas passage in a direction in which the dust collection area is arranged is equal to or less than a width in the dust collection area in a direction in which the dust collection area is arranged. Dust equipment.
The dust collector according to any one of claims 1 to 5, wherein a cleaning unit that supplies a liquid for cleaning the filter is installed above the filter.
A dust collection method for collecting particulate matter from a gas containing particulate matter and water mist using the dust collector according to any one of claims 1 to 6,
The step of applying a voltage to the discharge electrode by the power source to generate an ion wind from the discharge electrode to the ground electrode, and charging the particulate matter contained in the gas in the dust collection area; ,
Passing the gas through the filter and collecting the charged particulate matter with the filter.