JP2018030090A - Particle removal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a particle removal device capable of improving collection efficiency of very fine particles without changing greatly a conventional constitution.SOLUTION: A particle removal device 1 includes the first cooling part 3 for spraying droplets to exhaust gas containing particles charged positively or negatively, and cooling the exhaust gas to a temperature near a water dew point and higher than the water dew point, the second cooling part 4 for spraying very fine droplets to the exhaust gas having passed through the first cooling part 3, and an electric field formation part 5 for forming an electric field to a space where the exhaust gas having passed through the second cooling part 4 is circulated.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particle removing device, for example, a particle removing device using water spray applied as a dust removing device of an exhaust gas treatment facility.

  Conventionally, an electrostatic precipitator (EP) is generally used as a dust removing device, and thereafter a wet desulfurization device is installed. As a wet desulfurization method for removing sulfur contained in a gas such as exhaust gas, a magnesium hydroxide method, a soda method, a lime gypsum method and the like are known. In the magnesium hydroxide method or the soda method, magnesium hydroxide or caustic soda is used as an alkaline absorbent, respectively. In these methods, the equipment is simple, but the absorbent is expensive. In the lime-gypsum method, slurry-like limestone is used as the absorbent, the price of the absorbent is low, and gypsum can be recovered as a by-product, so the operating cost can be reduced. However, the lime gypsum method has complicated facilities and high construction costs.

  In either method, in the absorption tower in the latter stage, the exhaust gas containing sulfur content is desulfurized by absorption by the absorption liquid, so that the exhaust gas is treated with the moisture saturation temperature in the cooling section upstream from the inlet section of the absorption tower. Need to cool down. As a method for cooling the exhaust gas, it is common to spray water in the exhaust gas. In addition, both the cooling of the exhaust gas and the absorption of the sulfur content by the absorbent, the water is sprayed in a large amount, and it is effectively cooled using evaporation. Since water is lost by evaporation, water is newly supplied from the outside.

JP 10-174899 A (Patent No. 3572164) Japanese Patent Laying-Open No. 2005-349272 (Japanese Patent No. 4326403)

  In general, the smaller the particle size of the droplets sprayed on the exhaust gas, the more the specific surface area increases in inverse proportion to the particle size even with the same spray amount. However, in order to reduce the particle size, a special device such as a rotary atomizer or a two-fluid nozzle, high-pressure air, or the like is required. Therefore, in a large-scale industrial desulfurization apparatus, an ordinary nozzle is used, and the efficiency of cooling and sulfur absorption is increased by increasing the amount of spray.

  In general, particles (for example, dust) in the exhaust gas are removed by spraying water in the desulfurization apparatus. However, dust removal efficiency is not high in the collection only by the physical collision between the droplet and the dust.

  In a normal nozzle, the average particle diameter of the sprayed droplets is on the order of mm, and there is a distance between particles even if the liquid volume ratio (liquid gas ratio; L / G) per unit gas volume is increased. . For example, in the case of a cooling tower of a desulfurization apparatus, assuming that L / G = 0.5 and an average particle diameter of 2 mm, the average distance between particles when the particle diameter is uniformly dispersed is 20 mm. Further, in the absorption tower, even when L / G = 7.0, the average distance is 8.5 mm. Therefore, when trying to cope with a normal nozzle, the probability that fine dust contained in the gas collides with the spray droplets existing in the vicinity of the dust and is collected is not so high.

  Increasing L / G by increasing the amount of droplets sprayed from the nozzle can increase dust collection efficiency. However, a large amount of power is required to increase the amount of liquid, which causes an increase in equipment scale and cost, and a method for increasing the spray amount is difficult to realize.

  In recent years, with the tightening of emission regulations for fine particles such as PM2.5 and soot (dust), coal-fired power plants have installed a wet electrostatic precipitator (EP) at the outlet of the wet desulfurizer, or a wet desulfurizer. There is a tendency to install a bag filter instead of an electric dust collector installed upstream. However, when installing a bag filter, it is necessary to increase the capacity of the ventilator due to a significant increase in pressure loss, and there is also a problem that the power cost increases, both of which require significant equipment modifications. Become.

  The present invention has been made in view of such circumstances, and provides a particle removal apparatus capable of improving the collection efficiency of fine particles without making a significant change to the conventional configuration. The purpose is to do.

In order to solve the above problems, the particle removing apparatus of the present invention employs the following means.
That is, the particle removal apparatus according to the present invention sprays droplets on a gas containing positively or negatively charged particles, and cools the gas to a temperature near the water dew point and above the water dew point. An electric field with respect to a space in which the gas that has passed through the second cooling unit circulates, a second cooling unit that sprays fine droplets on the gas that has passed through the first cooling unit And an electric field forming portion for forming the.

  According to this configuration, in the first cooling unit, droplets are sprayed on the gas containing particles, cooled to a temperature equal to or higher than the water dew point near the water dew point (for example, within the water dew point + 20 ° C.), In the two cooling units, fine droplets are sprayed on the gas that has passed through the first cooling unit. The particles contained in the gas have a particle size of 10 μm or less, for example. At this time, since the gas is cooled in the first cooling unit in advance, even if the second cooling unit sprays the fine droplets, the fine droplets do not instantly evaporate, and the particles contained in the gas are removed. The time which can be made to adhere to a fine droplet is securable. Then, an electric field is formed in the space where the gas flows by the electric field forming unit, and the gas flows in the formed electric field, so that the fine droplets are dielectrically polarized, and the charged particles contained in the gas The droplet is attracted to the fine droplet by an electrostatic force acting between a portion of the droplet having a polarity opposite to that of the particle. The fine droplets sprayed by the second cooling unit have a particle size smaller than that of water (droplet to be sprayed) supplied by the first cooling unit, and the average particle size is 100 μm or less, preferably 50 μm or less. 10 μm or more.

  The particle removing apparatus according to the present invention sprays droplets on a gas containing positively or negatively charged particles, and cools the gas to a temperature near the water dew point and above the water dew point. 1 cooling part, 2nd cooling part which sprays a fine droplet with respect to the gas which passed the 1st cooling part, and the fine droplet sprayed from the 2nd cooling part are contrary to the particle A droplet charging unit that is charged to a polarity.

  According to this configuration, in the first cooling unit, droplets are sprayed on the gas containing particles, cooled to a temperature equal to or higher than the water dew point near the water dew point (for example, within the water dew point + 20 ° C.), In the two cooling units, fine droplets are sprayed on the gas that has passed through the first cooling unit. The particles contained in the gas have a particle size of 10 μm or less, for example. At this time, since the gas is cooled in the first cooling unit in advance, even if the second cooling unit sprays the fine droplets, the fine droplets do not instantly evaporate, and the particles contained in the gas are removed. The time which can be made to adhere to a fine droplet is securable. The droplet charging unit charges the fine droplet with a polarity opposite to the polarity of the particle, and the charged particle contained in the gas acts between a portion of the droplet with a polarity opposite to the polarity of the particle. Is attracted to the fine droplets by the electrostatic force. The fine droplets sprayed by the second cooling unit have a particle size smaller than that of water (droplet to be sprayed) supplied by the first cooling unit, and the average particle size is 100 μm or less, preferably 50 μm or less. 10 μm or more.

  In the above invention, the first cooling section may cool to a temperature within 50 ° C. higher than the water dew point.

  The said invention WHEREIN: You may further provide the collection part which collects the said fine droplet to which the said particle | grains adhered.

  According to this configuration, the fine droplets to which the particles are attached are collected by the collection unit. The fine droplets to which the particles are attached are at least 10 μm to 20 μm or more. The collection unit may be a simple device such as a mist eliminator, and can be collected if the particle diameter is 10 μm or more. The collecting unit may be a small electric dust collector. By installing the collection unit, the fine particles are not included in the gas supplied to the wet desulfurization apparatus installed on the downstream side of the particle removal apparatus. When collecting fine particles with a wet desulfurization device installed downstream of the particle removal device, the wet droplets are collected in the wet desulfurization device, so that the collection unit can be omitted.

  In the above invention, the collection unit is a mist eliminator, and water discharged from the mist eliminator is supplied to the first cooling unit, and the first cooling unit re-uses as water to be supplied to the gas. It may be used.

  According to this structure, the water used in a 1st cooling part circulates within a particle removal apparatus, and the quantity of the water which needs to be newly supplied can be reduced.

  In the above invention, the fine droplet sprayed by the second cooling unit may be generated by water newly supplied from the outside.

  According to this configuration, since water is newly supplied from the outside to the second cooling unit, stable spraying can be continued without blocking the second cooling unit that generates fine particles. The water newly supplied from the outside is, for example, clean water that does not contain fine particles that cause the second cooling unit to be blocked.

  In the above invention, the fine droplets to which the particles are attached are supplied to an absorption tower of a wet desulfurization apparatus, water stored in the absorption tower is supplied to the first cooling unit, and the first cooling unit is It may be reused as water to be supplied to the gas.

  According to this configuration, the water used in the first cooling section of the particle removal apparatus circulates between the particle removal apparatus and the absorption tower of the wet desulfurization apparatus, and the amount of water that needs to be newly supplied is reduced. Can be reduced.

  The said invention WHEREIN: You may further provide the charging part which charges the said particle | grains contained in the said gas supplied to a said 1st cooling part.

  According to this configuration, even when the electrostatic precipitator is not installed on the upstream side of the particle removing device, the particles contained in the gas supplied to the first cooling unit are charged by the charging unit. When the electrostatic precipitator is installed on the upstream side of the particle removing device, the particles included in the gas supplied to the first cooling unit are charged in the electrostatic precipitator, so that the charging unit can be omitted.

  In the above invention, the electric field forming unit may include two electrodes facing each other and form an electric field between the two electrodes.

  According to this configuration, when a voltage is applied to one electrode, an electric field is formed. When the fine droplets are sprayed from the second cooling unit, the fine droplets are dielectrically polarized positively and negatively by the formed electric field. The charged fine particles are attracted to the positive electrode side of the fine droplets and attracted to and attached to the fine droplets.

  In the above invention, the electric field forming unit includes a ground electrode and a discharge electrode having a barb portion provided to face the ground electrode, and an AC voltage is applied to the discharge electrode, and the second cooling unit The fine droplets sprayed from may be charged alternately with a positive charge and a negative charge with a time difference.

  According to this configuration, a group of sprayed droplets are alternately charged to positive and negative charges with a time difference, respectively, so that a fine droplet group having a positive charge and a fine liquid having a negative charge are charged. An electric field is formed between the droplet groups.

  In the above invention, the electric field forming unit may have a configuration capable of charging a fine droplet sprayed from a nozzle included in the second cooling unit to a positive charge and a negative charge.

  According to this configuration, the sprayed fine droplets can be charged to positive and negative charges, so that a group of fine droplets having a positive charge and negative charges can be obtained without providing an external electrode. An electric field is formed between the fine droplet groups having the following charges.

In the above invention, the electric field forming section may be installed in a plurality of stages along the gas flow direction.
According to this configuration, the collection efficiency can be further increased as compared with the case where only one electric field forming unit is installed.

  According to the present invention, it is possible to improve the collection efficiency of fine particles without making significant changes to the conventional configuration.

It is a schematic block diagram which shows the absorption tower of the particle removal apparatus and wet desulfurization apparatus which concern on 1st Embodiment of this invention. It is a schematic block diagram which shows the absorption tower of the modification of the particle | grain removal apparatus which concerns on 1st Embodiment of this invention, and a wet desulfurization apparatus. It is a schematic block diagram which shows the 1st Example of the electric field formation part of the particle removal apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the 1st modification of the 1st Example of the electric field formation part of the particle removal apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the 2nd modification of the 1st Example of the electric field formation part of the particle | grain removal apparatus which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the 2nd Example of the electric field formation part of the particle removal apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the modification of the 2nd Example of the electric field formation part of the particle | grain removal apparatus which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the 3rd Example of the electric field formation part of the particle removal apparatus which concerns on 1st Embodiment of this invention. It is a schematic block diagram which shows the 4th Example of the electric field formation part of the particle removal apparatus which concerns on 1st Embodiment of this invention. It is a longitudinal cross-sectional view which shows the electric field formation part of the particle removal apparatus which concerns on 2nd Embodiment of this invention. It is a schematic diagram which shows the fine droplet and particle | grains in an electric field.

[First Embodiment]
The particle removal apparatus 1 according to the first embodiment of the present invention is applied to, for example, an exhaust gas treatment facility. The exhaust gas treatment facility includes an electrostatic precipitator (EP) 2 that removes particles (for example, dust), a particle removal device 1, a wet desulfurization device, and the like. As shown in FIG. 1, the particle removing device 1 is installed on the downstream side of the electrostatic precipitator 2 and on the upstream side of the gas flow of the absorption tower 40 of the wet desulfurization device. In the process of lowering to the water dew point, fine particles are attached to the droplets. The droplets to which the fine particles are attached are collected by a collection unit such as an absorption tower 40 or a mist eliminator of a wet desulfurization apparatus provided on the downstream side, and the fine particles are removed from the exhaust gas. In the example shown in FIG. 1, a mist eliminator 41 as a collection unit is installed at the upper part of the absorption tower 40.

  The exhaust gas is a gas generated when fuel (for example, coal, petroleum coke, etc.) is burned. The fine particles to be removed are, for example, PM2.5, and the particle size is, for example, 10 μm or less.

  The electric dust collector 2 is charged with particles contained in the exhaust gas by introducing the exhaust gas to be removed. The electric dust collector 2 can be applied with a normally used device, and has, for example, a plurality of ground electrodes arranged in parallel and a discharge electrode disposed between adjacent ground electrodes. The exhaust gas that has passed through the electric dust collector 2 is supplied to the first cooling unit 3 of the particle removing device 1. The particles contained in the exhaust gas supplied to the first cooling unit 3 are positively or negatively charged by the discharge in the electric dust collector 2.

  As shown in FIG. 1, the particle removing apparatus 1 includes a first cooling unit 3, a second cooling unit 4, an electric field forming unit 5, and the like. The first cooling unit, the second cooling unit 4 and the electric field forming unit 5 are accommodated in the casing 10.

  In the exhaust gas treatment facility, when the electric dust collector is not installed in the previous stage of the particle removing device 1, a preliminary charging unit for charging the dust is installed in the casing 10 before the first cooling unit 3. . For the preliminary charging unit, a commonly used device can be applied. For example, the preliminary charging unit includes a plurality of ground electrodes arranged in parallel and a discharge electrode disposed between adjacent ground electrodes. In this case, particles contained in the exhaust gas supplied to the first cooling unit 3 are positively or negatively charged by the discharge in the preliminary charging unit.

  In the present embodiment in which an electric dust collector (EP) (not shown) is installed upstream of the particle removing device 1, it is included in the exhaust gas supplied to the first cooling unit 3 in the electric dust collector 2. Since the particles to be charged are charged, the preliminary charging portion can be omitted. For example, in a fluidized bed boiler or the like, when the particles themselves have a charge due to frictional charging or the like, it is possible that an electrostatic precipitator (EP) or a preliminary charging unit is not installed.

  The first cooling unit 3 sprays droplets of, for example, millimeters on the exhaust gas containing particles, so that the exhaust gas is at a temperature near the water dew point and above the water dew point (for example, the water dew point above the water dew point). Cool to within + 50 ° C, preferably within water dew point + 30 ° C, more preferably within water dew point + 20 ° C. Since the exhaust gas is preliminarily cooled to the vicinity of the water dew point in the first cooling unit 3, even if the fine droplets are sprayed in the second cooling unit 4 in the subsequent stage, the fine droplets do not instantly evaporate, A time during which the contained particles can be attached to the fine droplets can be secured. The exhaust gas that has passed through the first cooling unit 3 is supplied to the second cooling unit 4.

The first cooling unit 3 is, for example, a one-fluid nozzle, and is configured such that the flow rate distribution is uniform in the width direction. The average particle diameter of the droplets sprayed by the first cooling unit 3 is, for example, 1 mm to 3 mm. Further, the liquid volume ratio per unit gas volume (liquid gas ratio; L / G [L / m ³ ]. Here, the liquid volume L [L / min] and the gas volume G [m ³ / min].) Is, for example, 0.3 [L / m ³ ]. Assuming that the average particle diameter of droplets sprayed by the first cooling unit 3 is 1 mm and L / G = 0.3 [L / m ³ ], the number of droplets sprayed by the first cooling unit 3 is 38.2. The number of droplets / m ³ is calculated, and the calculated distance between droplets is 12.1 mm (center-to-center).

  The first cooling unit 3 desirably cools the exhaust gas within a water dew point of + 20 ° C. It is known that a semi-dry desulfurization apparatus put into practical use can be operated stably when the drying condition is higher than the water dew point + 20 ° C. On the other hand, under wet conditions within a water dew point of + 20 ° C., the droplets are difficult to evaporate, and the fine droplets sprayed by the second cooling unit 4 also take time to evaporate. Therefore, it is possible to ensure a long time for the fine droplets and fine particles to coexist in the electric field.

  The second cooling unit 4 sprays fine droplets on the exhaust gas that has passed through the first cooling unit 3. The average particle size of the fine droplets sprayed by the second cooling unit 4 is smaller than the average particle size of the droplets sprayed by the first cooling unit 3, for example, 100 μm or less, preferably 50 μm or less, and 10 μm or more. .

The second cooling unit 4 is, for example, a two-fluid nozzle, and is configured so that the flow rate distribution is uniform in the width direction. The liquid amount ratio (liquid gas ratio; L / G) per unit gas amount sprayed by the second cooling unit 4 is, for example, 0.05 [L / m ³ ]. Assuming that the average particle diameter of the fine droplets sprayed by the second cooling unit 4 is 50 μm and L / G = 0.05 [L / m ³ ], the number of droplets sprayed by the second cooling unit 4 is It is 7.64 billion pieces / m ³ , and the calculated inter-droplet distance is 1.1 mm (center to center). Therefore, in the electric field formed by the electric field forming unit 5 at the subsequent stage, the probability that the fine particles contained in the exhaust gas collide with the fine droplets sprayed by the second cooling unit 4 and are collected is greatly increased.

  Fine droplets sprayed by the second cooling unit 4 are generated by water newly supplied from the outside. Since water is newly supplied to the second cooling unit 4 from the outside, stable spraying can be continued without blocking the second cooling unit 4 that generates fine particles. The water newly supplied from the outside is, for example, clean water that does not contain fine particles that cause the second cooling unit 4 to be blocked.

  The electric field forming unit 5 forms an electric field in the space in which the exhaust gas that has passed through the second cooling unit 4 flows. As shown in FIG. 11, an electric field is formed in the space in which the exhaust gas flows by the electric field forming unit 5, and the exhaust gas flows in the formed electric field, so that the fine droplet 51 sprayed by the second cooling unit 4. Is dielectrically polarized and the charged particles 52 contained in the exhaust gas are attracted to the fine droplets 51.

Next, operation | movement of the particle removal apparatus 1 which concerns on this embodiment is demonstrated.
When the exhaust gas is supplied to the electrostatic precipitator 2 installed at the front stage of the particle removing device 1, the particles contained in the exhaust gas are collected by the electrostatic precipitator 2. Thereafter, the exhaust gas that has passed through the electrostatic precipitator 2 is supplied to the particle removing device 1. The exhaust gas supplied to the particle removing device 1 includes particles that have not been collected by the electric dust collector 2. In the electric dust collector 2, fine particles contained in the exhaust gas are positively or negatively charged by discharge. Then, the exhaust gas containing the particles charged by the discharge is supplied to the first cooling unit 3 of the particle removing device 1.

  In the first cooling unit 3, exhaust gas containing charged fine particles is supplied, and the exhaust gas has a temperature equal to or higher than the water dew point in the vicinity of the water dew point (for example, the water dew point to the water dew point + 50 ° C., preferably the water dew point +30 In the second cooling unit 4, fine droplets are sprayed on the gas that has passed through the first cooling unit 3.

  Then, as shown in FIG. 11, an electric field is formed in the space in which the gas flows by the electric field forming unit 5, and the gas flows in the formed electric field, so that the fine droplet 51 is dielectrically polarized, and The charged particles 52 contained in the gas are attracted to the nearby fine droplets 51 by electrostatic force. That is, under the condition that the fine droplet 51 exists and the distance between the fine droplet 51 and the particle 52 is short, the electrostatic force is applied between the particle 52 and the portion of the fine droplet 51 having a polarity opposite to the polarity of the particle 52. Works. For example, when the fine particles are charged with a negative polarity, electrostatic force acts between the particles 52 and the positive polarity of the fine droplets 51 in the immediate vicinity, and the particles 52 are attracted to the fine droplets 51.

  Particles contained in the gas are attached to the fine droplets that have passed through the electric field formed by the electric field forming unit 5, and are collected later by a collection unit such as an absorption tower 40 of a wet desulfurization apparatus or a mist eliminator. Fine droplets with fine particles attached are collected.

  Note that water is newly supplied to the second cooling unit 4 from the outside, and stable spraying is continued without blocking the second cooling unit 4 that generates fine particles.

  As described above, according to the present embodiment, since the fine droplets are sprayed by the second cooling unit 4, the charged fine particles contained in the exhaust gas are fine droplets in the electric field formed by the electric field forming unit 5. The probability of being collected by colliding with will increase. The fine particles collected by the particle removing device 1 are particles that are charged by the electric dust collector 2 installed on the upstream side of the particle removing device 1 and are not collected by the electric dust collector 2, for example, The particle size is 10 μm or less.

Assuming that the average particle size of the fine droplets sprayed by the second cooling unit 4 is 50 μm and L / G = 0.05 [L / m ³ ], as described above, the calculated inter-droplet distance is 1.1 mm. (Between the centers). On the other hand, assuming that the average particle diameter of the droplet is 1 mm and L / G = 0.5 [L / m ³ ], the calculated inter-drop distance is about 10 mm (center-to-center). Compared to the assumed example, the distance between droplets is long despite the high L / G. Therefore, the probability of colliding with fine droplets is increased when the particle size is reduced rather than increasing L / G. In this embodiment, the closer the distance between the charged particles and the atomized fine droplets, the better the collection efficiency.

  If the fine droplets are sprayed at a high temperature in the gas flow of the exhaust gas, the fine droplets instantly evaporate. When droplets having different droplet diameters are mixed, the evaporation rate of the droplets increases in inverse proportion to the square of the droplet diameter. For example, when a 1 mm droplet and a 50 μm droplet are mixed, the 50 μm droplet evaporates at a speed of about 400 times (20 × 20).

  In this embodiment, two-stage spraying of the first cooling unit 3 and the second cooling unit 4 is performed, and when the second cooling unit 4 sprays fine droplets, the exhaust gas is cooled in advance in the first cooling unit 3. ing. For this reason, the evaporation rate of the fine droplets is slow, and even if the second cooling unit 4 sprays the fine droplets, the fine droplets do not instantly evaporate, and the particles contained in the exhaust gas are finely divided by the action of the electric field. The time which can be made to adhere to a droplet is securable.

  Therefore, according to the present embodiment, it is possible to improve the collection efficiency of fine particles while suppressing an increase in pressure loss as compared with the case where a bag filter or the like is employed. Moreover, the collection efficiency of fine particles can be improved without making significant changes to the conventional configuration.

  In addition, although embodiment mentioned above demonstrated the case where the 2nd stage spray of the 1st cooling part 3 and the 2nd cooling part 4 was performed, this invention includes the case where the multistage spray of 3 or more stages is performed.

Next, the case where the particle removal apparatus 1 which concerns on this embodiment is used in combination with a wet desulfurization apparatus is demonstrated.
When the particle removal apparatus 1 is used in combination with a wet desulfurization apparatus, in the magnesium hydroxide method or the soda method, as shown in FIG. 1, fine droplets that have passed through the electric field formed by the electric field forming unit 5 are It is supplied to the absorption tower 40 of the wet desulfurization apparatus. And the water stored in the absorption tower 40 is supplied to the 1st cooling part 3 via the circulation path 42, and is reused as the droplet which the 1st cooling part 3 supplies with respect to waste gas. A circulating water pump 43 is provided in the circulation path 42.

  Thereby, the water used in the 1st cooling part of a particle removal apparatus circulates between the particle removal apparatus 1 and the absorption tower 40 of a wet desulfurization apparatus, and reduces the quantity of the water which needs to be newly supplied. it can.

  When the particle removal device 1 is used in combination with a wet desulfurization device, in the lime gypsum method, a mist eliminator 6 is provided inside the casing 10 of the particle removal device 1 as shown in FIG. The mist eliminator 6 collects fine droplets that have passed through the electric field formed by the electric field forming unit 5. Particles contained in the exhaust gas are attached to the fine droplets that have passed through the electric field, and the mist eliminator 6 collects the fine droplets to which the particles are attached.

  Thereby, it can suppress that the particle | grains (ash component) contained in waste gas penetrate | invade into the absorption tower 40 of a back | latter stage. As a result, in the lime gypsum method, it is possible to prevent problems caused by elution of the ash component generated in the absorption tower 40 (for example, a decrease in reaction rate due to the coating of the inert component on the absorbent) and mixing of the ash component, gypsum, etc. It is possible to improve the purity of by-products. A small electric dust collector may be installed in place of the mist eliminator 6. When the fine particles are collected by the wet desulfurization apparatus installed on the downstream side of the particle removal apparatus 1, since the fine droplets to which the particles adhere are collected in the wet desulfurization apparatus, as shown in FIG. The mist eliminator 6 can be omitted.

Furthermore, the water discharged from the mist eliminator 6 is supplied to the first cooling unit 3 through the circulation path 7 and reused as water supplied to the exhaust gas by the first cooling unit 3. Thereby, the water used in the 1st cooling part 3 circulates in the particle removal apparatus 1, and the quantity of the water which needs to be newly supplied can be reduced. The circulation system includes a circulation path 7, a circulation water tank 8 and a circulation water pump 9 installed in the circulation path 7.
Although not shown in the figure, since water absorbs acidic gas and the pH is lowered significantly, it becomes easy to corrode. Therefore, in order to prevent corrosion, it is also possible to adjust the pH by appropriately adding alkali. .

<Electric field forming part>
Next, with reference to FIGS. 3 to 9, the electric field forming unit 5 applied in the particle removing apparatus 1 according to the present embodiment will be described.

<Electric field forming portion (first embodiment)>
The electric field forming unit 5 includes opposed electrodes and forms an electric field between the opposed electrodes as in the examples illustrated in FIGS. 3 to 5, for example.

  As shown in FIG. 3, the electric field forming unit 5 includes a mesh-shaped electrode 11 having a large aperture ratio that does not hinder the flow of two exhaust gases arranged in parallel, and the same exhaust gas disposed in parallel with these electrodes 11. A mesh-shaped electrode 12 having a large aperture ratio that does not inhibit the flow is provided so as to be orthogonal to the flow direction of the exhaust gas. A voltage is applied to the electrode 12 by a high voltage generator. The aperture ratio of the mesh-like electrodes 11 and 12 is, for example, 70% or more, desirably 80% or more. By increasing the aperture ratio, the probability that the sprayed droplets are collected by the electrodes 11 and 12 can be lowered, and the fine droplets necessary for collecting the fine particles can be kept in the space for as long as possible. It can be secured.

  When a voltage is applied to the electrode 12, an electric field is formed in the gas flow direction. Here, when the fine droplets are sprayed from the second cooling unit 4 from the top to the bottom, that is, in the same direction as the gas flow direction, the fine droplets are dielectrically polarized positively and negatively by the formed electric field.

  In the case where the charged fine particles contained in the exhaust gas are negatively charged, the fine particles are attracted to the positive electrode side of the fine droplets and are attracted to and attached to the fine droplets. And the fine droplet which caught the fine particle is collected by collection parts, such as absorption tower 40 or a mist eliminator.

  In the example shown in FIG. 3, a combination of two electrodes 11 and two electrodes 12 is arranged, but a plurality of electrodes 12 to which a high voltage is applied may be arranged in multiple stages. . For example, as shown in FIG. 4, three electrodes 11 are arranged in parallel with each other, and two electrodes 12 are arranged in parallel with each other. One electrode 12 is disposed between two adjacent electrodes 11. The two electrodes 11 may be connected by a connecting rod 13. In this case, an opening 14 through which the connecting rod 13 passes is formed in the electrode 12 disposed between the electrodes 11.

  3 and 4 show the case where the exhaust gas flowing through the particle removal apparatus 1 flows in the vertical direction (from the upper part to the lower part), but as shown in FIG. 5, the exhaust gas flowing through the particle removal apparatus 1 is The present invention can also be applied to the case of flowing in the horizontal direction. Also in the example shown in FIG. 5, the electrodes 11 and 12 are installed so as to be orthogonal to the flow direction of the exhaust gas.

<Electric field forming portion (second embodiment)>
Moreover, the electric field formation part 5 may form the electric field which generates a corona discharge, as shown in FIG.6 and FIG.7.
In this case, the electric field forming unit 5 includes a mesh-shaped ground electrode 21 having a large aperture ratio that does not inhibit the flow of exhaust gas, and a discharge electrode 22 having a barb portion 23 provided to face the ground electrode 21 in the flow direction of exhaust gas. And so as to be orthogonal. A voltage is applied to the discharge electrode 22 by an AC high voltage generator. The aperture ratio of the mesh-like earth electrode 21 is, for example, 70% or more, preferably 80% or more. By increasing the aperture ratio, the probability that the sprayed droplets are collected by the ground electrode 21 can be lowered, and the fine droplets necessary for collecting the fine particles are secured in the space for as long as possible. it can.

  Due to the discharge by the discharge electrode 22, an alternating voltage is used to form a droplet group in which positive and negative are alternately charged with a temporal phase difference. That is, a group of droplets having a positive charge is repeated by applying a positive charge to the droplet, then applying a negative charge to the droplet, and then applying a positive charge. And droplet groups having negative charges are alternately formed. An electric field is formed between the droplet group having a positive charge and the droplet group having a negative charge. The fine droplets in the electric field are dielectrically polarized positively and negatively by the formed electric field.

  In the case where the charged fine particles contained in the exhaust gas are negatively charged, the fine particles are attracted to the positive electrode side of the fine droplets and are attracted to and attached to the fine droplets. And the fine droplet which caught the fine particle is collected by collection parts, such as absorption tower 40 or a mist eliminator.

  The charged fine particles are charged again in the space of the electric field forming unit 5. However, the speed at which the fine particles are charged and the speed at which the droplets are charged by the water spray are overwhelming with the liquid spray. Very fast. Therefore, by shortening the period in which the particles are charged by the ground electrode 21 and the discharge electrode 22, the charge of the fine particles can be obtained even in the time zone in which the negatively charged fine particles have received a positive charge having a polarity opposite to that of the fine particles. The polarity of is maintained.

  6 shows the case where the exhaust gas flowing through the particle removal apparatus 1 flows in the vertical direction (from the upper part to the lower part), the exhaust gas flowing through the particle removal apparatus 1 is horizontal as shown in FIG. The present invention can also be applied to the case of flowing. Also in the example shown in FIG. 7, the ground electrode 21 and the discharge electrode 22 are installed so as to be orthogonal to the flow direction of the exhaust gas.

<Electric field forming portion (third embodiment)>
Further, as shown in FIG. 8, the electric field forming unit 5 may form an electric field by sprayed droplets by a charging nozzle method combined with the second cooling unit 4.

As shown in FIG. 8, the second cooling unit 4 includes charging nozzles 31a and 31b.
The charging nozzle 31a has a configuration capable of charging the fine droplets to be sprayed so that the fine droplets to be sprayed are positive, and the charging nozzle 31b is negative to the fine droplets to be sprayed. For example, the electric field forming unit 5 includes a voltage applying unit 32a that applies a negative DC voltage to the charging nozzle 31a and a voltage applying unit 32b that applies a positive DC voltage to the charging nozzle 31b.

  As a result, the sprayed groups of fine droplets are charged with positive and negative charges, respectively, and there is an electric field in the direction perpendicular to the gas flow between these groups without providing an external electrode. Is formed.

  The negatively charged fine particles contained in the exhaust gas are guided into an electric field formed by a group of positively charged fine droplets and a group of negatively charged fine droplets. The fine particles are effectively trapped in the fine droplets by electrostatic force. Thereafter, the fine droplets capturing the fine particles are collected by a collection unit such as the absorption tower 40 or a mist eliminator.

<Electric field forming portion (fourth embodiment)>
As shown in FIG. 9, the electric field forming unit 5 may form an electric field by sprayed droplets by a charging nozzle method combined with the second cooling unit 4.
As shown in FIG. 9, the second cooling unit 4 includes charging nozzles 33a and 33b.
The electric field forming unit 5 includes a voltage applying unit 34 that supplies an alternating voltage to the charging nozzles 33a and 33b, and the voltage applying unit 34 applies an alternating electric field to the charging nozzles 33a and 33b.

  In the case of having this configuration, the polarity of the charge held by the fine droplets varies with time. For this reason, groups of fine droplets having positive and negative charges in the upper and lower gas flow directions are alternately formed, and an electric field is formed in the gas flow direction.

  The negatively charged fine particles contained in the exhaust gas are guided into an electric field formed by a group of positively charged fine droplets and a group of negatively charged fine droplets. The fine particles are effectively trapped in the fine droplets by electrostatic force. Thereafter, the fine droplets capturing the fine particles are collected by a collection unit such as the absorption tower 40 or a mist eliminator.

  In addition, although the structure of the electric field formation part 5 mentioned above demonstrated 1 step | paragraph, this invention is not limited to this example, You may arrange | position with two or more steps | paragraphs. Thereby, the collection efficiency of fine particles can be further increased.

[Second Embodiment]
Next, with reference to FIG. 10, the particle removal apparatus 1 which concerns on 2nd Embodiment of this invention is demonstrated.
Although 1st Embodiment mentioned above demonstrated the case where the electric field formation part 5 was installed in the particle removal apparatus 1, this invention is not limited to this example. For example, instead of the electric field forming unit 5, a droplet charging unit 15 is installed. In the following, detailed description of configurations and operational effects overlapping with those of the first embodiment will be omitted.

  The droplet charging unit 15 charges the fine droplets sprayed from the second cooling unit 4 with a polarity opposite to that of the particles. For example, when the particles are negatively charged, the droplet charging unit 15 charges the fine droplets positively.

The droplet charging unit 15 includes a charging nozzle 16 as shown in FIG.
When the particles are negatively charged, the charging nozzle 16 has a configuration capable of charging the fine droplets to be sprayed so that the fine droplets to be sprayed become positive. For example, the droplet charging unit 15 includes a voltage applying unit 17 that applies a negative DC voltage to the charging nozzle 16. As a result, the sprayed fine droplets are always charged with a positive charge.

  In the space on the downstream side of the droplet charging unit 15, negatively charged fine particles contained in the exhaust gas and positively charged fine droplets exist simultaneously. Since the fine droplets have the same polarity, they repel each other, so the fine droplets try to be distributed uniformly. The negatively charged fine particles and the positively charged fine droplets rapidly increase in electrostatic force in an area close to each other, and the probability of being collected increases.

  Then, after the fine particles are effectively captured in the fine droplets by electrostatic force, the fine droplets that have captured the fine particles are collected by a collection unit such as the absorption tower 40 or the mist eliminator.

  According to the present embodiment, since the object is not charged by corona discharge in the space, when the fine droplets are charged with the opposite polarity to the particles, the fine particles have the opposite polarity. The charge is not given, and the amount of charge initially possessed by the fine particles is not reduced.

DESCRIPTION OF SYMBOLS 1: Particle removal apparatus 2: Electric dust collector 3: First cooling part 4: Second cooling part 5: Electric field formation part 6: Mist eliminator 7: Circulation path 8: Circulating water tank 9: Circulating water pump 10: Casing 11 : Electrode 12: Electrode 13: Connecting rod 14: Opening part 15: Droplet charging part 16: Charging nozzle 17: Voltage application part 21: Earth electrode 22: Discharge electrode 23: Barbed part 31a: Charging nozzle 31b: Charging nozzle 32a: Voltage application unit 32b: Voltage application unit 33a: Charging nozzle 33b: Charging nozzle 40: Absorption tower 41: Mist eliminator 42: Circulation path 43: Circulating water pump

Claims (12)

A first cooling unit that sprays droplets on a gas containing positively or negatively charged particles, and cools the gas to a temperature near the water dew point and above the water dew point;
A second cooling unit that sprays fine droplets on the gas that has passed through the first cooling unit;
An electric field forming unit that forms an electric field in a space in which the gas that has passed through the second cooling unit flows;
A particle removal apparatus comprising: A first cooling unit that sprays droplets on a gas containing positively or negatively charged particles, and cools the gas to a temperature near the water dew point and above the water dew point;
A second cooling unit that sprays fine droplets on the gas that has passed through the first cooling unit;
A droplet charging unit that charges the fine droplets sprayed from the second cooling unit with a polarity opposite to that of the particles;
A particle removal apparatus comprising:   The particle removal apparatus according to claim 1 or 2, wherein the first cooling unit cools to a temperature within 50 ° C higher than the water dew point.   The particle removal apparatus according to claim 1, further comprising a collection unit that collects the fine droplets to which the particles are attached. The collection unit is a mist eliminator,
The particle removal apparatus according to claim 4, wherein water discharged from the mist eliminator is supplied to the first cooling unit, and the first cooling unit is reused as water supplied to the gas.   The particle removing apparatus according to claim 1, wherein the fine droplets sprayed by the second cooling unit are generated by water newly supplied from the outside. The fine droplets to which the particles are attached are supplied to an absorption tower of a wet desulfurization apparatus,
The water stored in the absorption tower is supplied to the first cooling unit, and the first cooling unit is reused as water to be supplied to the gas. Particle removal equipment.   The particle removal apparatus according to any one of claims 1 to 7, further comprising a charging unit that charges the particles contained in the gas supplied to the first cooling unit.   The particle removing apparatus according to claim 1, wherein the electric field forming unit includes two electrodes facing each other, and forms an electric field between the two electrodes.   The electric field forming unit includes a ground electrode and a discharge electrode having a barb portion provided to face the ground electrode, and an AC voltage is applied to the discharge electrode and sprayed from the second cooling unit. The particle removing apparatus according to claim 1, wherein the fine droplets are alternately charged with a positive charge and a negative charge with a time difference.   The particle removing apparatus according to claim 1, wherein the electric field forming unit has a configuration capable of charging a fine droplet sprayed from a nozzle included in the second cooling unit to a positive charge and a negative charge.   The particle removal apparatus according to any one of claims 9 to 11, wherein the electric field forming unit is installed in a plurality of stages along the gas flow direction.

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