JPH06257463A - Dust removing system for pressure fluidized-bed boiler compound electric power plant - Google Patents

Abstract

PURPOSE:To provide a dust removing system having high reliability in operation of the plant, for effectively removing soot and dust discharged from a pressure fluidized-bed boiler electric power plant. CONSTITUTION:Soot and dust discharged from a pressure fluidized-bed boiler 1 are roughly removed by a single cyclone separator 21, and then soot and dust having such a size to apply abrasion to the blade of a gas turbine 4 are completely removed by a multi-cyclone separator 31. Exhaust gas in a gas turbine outlet is removed in a funnel inlet flue by a dust collector 8 so as to have the dust density not disturbing the atmospheric environment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dust removing system for removing dust from combustion exhaust gas of a pressurized fluidized bed boiler combined cycle power plant.

[0002]

2. Description of the Related Art Currently, pulverized coal cooking is the mainstream of thermal power generation boilers that use coal as a fuel, but in order to deal with the environmental problem of global warming due to carbon dioxide, a highly efficient fuel utilization technology is strongly required. Has been done. As this environmentally friendly coal-fired power plant, the pressurized fluidized bed boiler combined cycle power plant currently under development in Japan and overseas has higher power generation efficiency than pulverized coal cooking, and is attracting attention as a promising power generation system.

[0003] The pressurized fluidized bed boiler combined cycle power plant, instead of the conventional pulverized coal combustion boiler, fluidizes and combusts finely crushed coal in the boiler under pressure, and a water pipe laid in the fluidized bed. The steam generated from the steam turbine drives the steam turbine, and the high-pressure combustion exhaust gas discharged from the boiler drives the gas turbine to generate electric power.

In this system, limestone is used as a fluid medium in the fluidized bed, sulfur content in coal and calcium in limestone can be reacted to desulfurize in a boiler, and the flame temperature in the fluidized bed is pulverized coal. Since it is lower, the production amount of nitrogen oxide is small. However, as a problem in operating this plant, there is selection of an effective dust collection method that clears emission regulations for preventing wear of gas turbine blades and air pollution due to dust produced by combustion of coal.

For this reason, various dust removal methods have been proposed. For example, the 9th PARTICULATE CONTRO sponsored by EPRI
L SYMPOSIUM (1991,10) 5B-1 discloses a dedusting method for a pressurized fluidized bed boiler power plant. An atmosphere with a gas temperature of 850 to 900 ° C after roughly collecting high concentration dust of 20 to ³⁰ g / Nm ³ contained in the gas discharged from the fluidized bed combustion boiler with a centrifugal cyclone and before introducing it into the gas turbine. A method of removing dust with a ceramic filter has been proposed.

[0006] As another method, at the boiler outlet, first, a single cyclone having a large amount of treated gas is used to roughly remove dust, and then a multi-cyclone having a small amount of treated but high dust collecting performance is used for the turbine blade. A method has been proposed in which exhaust gas larger than about 5 μm, which does not affect wear, is removed, and then exhaust gas is introduced into a gas turbine.

In this case, it is preferable that the multi-cyclone can exhibit the dust collection performance satisfying the emission regulation to the atmosphere, but the cyclone system using the centrifugal force has a limit in separating the dust from the gas, I can't meet the regulations. In particular, in fluidized bed combustion, fine dust is discharged due to friction between coal as a fuel and a fluid medium, and a high-performance dust collector is required to satisfy emission regulations. For this reason, a dust collection system has been proposed in which an electric dust collection or a bag filter device is provided at the gas turbine outlet, that is, the chimney inlet.

[0008]

The above-mentioned removal method using the ceramic filter has a high dust collecting performance and is free from the fear of wear of the turbine blade, and can also meet the emission control from the chimney, but it is operated under high temperature and high pressure. Therefore, the ceramic filter may be cracked or damaged, and there is a problem in reliability during long-term operation. If the ceramic filter is damaged during operation, it may cause a situation in which the operation must be stopped even during power generation because the turbine blade is worn.

On the other hand, it has been confirmed by experiments that the dust removal performance of each cyclone of a small-diameter multi-cyclone can efficiently remove dust particles having a size of about 3 to 5 μm or more that affect the wear of turbine blades. When a large number of cyclones are arranged in parallel, a slight pressure difference occurs between the cyclones, and the dust particles separated by the cyclones flow from the bottom of other cyclones, so the dust collection performance of the conventional multi-cyclone deteriorates. However, there is a problem that the turbine blade is worn.

Further, since each individual cyclone has a small tube diameter, there is a problem that clogging occurs in the dust separating part and the function of the cyclone is not fulfilled. On the other hand, the soot and dust discharged from the fluidized bed combustion boiler contains a large amount of fine particles of 1 μm or less due to friction between the fluid medium and pulverized coal during fluid combustion.
In the electrostatic precipitator described above, the amount of electric charge received by the particles is small, and the moving speed of the particles due to the electric field is slow, so not only the volume of the device becomes large, but also the dust collected by the dust collecting electrode is removed by hammering. However, there is a problem in that limestone used as a fluid medium in a fluidized combustion furnace has a high electric resistance and thus the dust collection performance is deteriorated due to a reverse ionization phenomenon.

On the other hand, the bag filter method has a drawback that the filter is quickly clogged because the particle size of the dust is small and it is necessary to frequently remove the filter, which shortens the life of the filter.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a dedusting system for a pressurized fluidized bed boiler combined cycle power plant that efficiently removes dust from the exhaust gas of the pressurized fluidized bed boiler. To aim.

[0013]

The above object can be achieved as follows. That is, in a pressurized fluidized bed boiler combined cycle power plant consisting of a pressurized fluidized bed boiler, a steam turbine generator and a gas turbine generator, soot and dust in boiler combustion exhaust gas is removed by a cyclone having a large cylinder diameter. Then, together with the newly improved multi-cyclone with a small cylinder diameter, blow-down that sucks part of the exhaust gas from the multi-cyclone hopper is carried out to reliably remove the dust that causes the turbine blades to be introduced into the gas turbine. Then
Fine dust that could not be removed by the multi-cyclone is removed by the effective dust collector at the gas turbine outlet flue to a concentration below the atmospheric environment.

[0014]

The flue gas discharged from the pressurized fluidized bed boiler is about 10 μm in the centrifugal cyclone before being introduced into the gas turbine by the large-diameter cyclone.
Remove the above dust. Then, particles having a size of 3 to 5 μm or more that cause wear to the turbine blades are almost completely removed by the multi-cyclone having a small cyclone cylinder diameter. Multi cyclone Each cyclone is provided with a gas buffer cylinder below the dust separator, and the dust separated by the cyclone can be efficiently collected in the hopper without interfering with each other. By performing the above-mentioned blowdown, the separation effect in the multi cyclone dust separator is further enhanced, and finer dust is removed.

The gas discharged from the multi-cyclone is
It flows into the gas turbine, where the energy of pressure and temperature disappears and is discharged. The exhaust gas at the gas turbine outlet is introduced into a charging device including, for example, a discharge electrode and a ground electrode, and dust in the gas is charged by corona discharge. At this time, the soot and dust adhering to the ground electrode due to corona discharge is heated by the heating device provided to the ground electrode, so that the soot and dust with high electric resistance is reduced, and stable discharge is maintained.

Further, by scraping off the dust and dirt adhering to the ground electrode, the ground electrode surface is cleaned and the corona discharge is stabilized, so that the dust and particles can be efficiently charged. The charged dust is introduced into the filter and collected on the filtration surface, and the collected dust raises the potential of the filtration surface. The charged dust that newly flows into the filtration surface formed by the surface potential repels each other because it has the same polarity as the potential of the filtration surface, and the particles agglomerate to improve the dust collection performance. The ventilation resistance is suppressed. For this reason, the frequency of brushing off is low, and the life of the filter can be maintained long.

[0017]

Embodiment An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of an embodiment of a dedusting system for a pressurized fluidized bed boiler combined cycle power plant of the present invention. 1 is a pressurized fluidized bed boiler, 2 is a pressure vessel that houses a large-diameter cyclone 21, 3 is a pressure vessel that houses a small-diameter multi-cyclone 31, 4 is a gas turbine, 5 is a generator, and 6 is a multi-cyclone. It is a filter that sucks a part of the exhaust gas from the hopper 31 and removes the dust contained in the gas, and the exhaust gas at the outlet thereof is introduced to the inlet of the gas turbine 4. Reference numeral 7 is an air heater, and 8 is a dust collector. For example, the dust collector 8 is composed of a charging device 81 and a bag filter 82. 9 is a chimney.

Limestone is used as the fluid medium of the pressurized fluidized bed boiler 1, and pulverized coal and air are supplied into the fluidized bed of heated limestone and burned. The combustion exhaust gas discharged from the boiler contains about 30 g of soot and dust per 1 Nm ³ ,
The particle size of soot and dust is distributed in the range of about 0.1 to 100 μm. The gas temperature is as high as 850 to 900 ° C., and the gas pressure is also as high as 10 to ²⁰ kg / cm ² .

In the exhaust gas from the boiler, first, a large-diameter cyclone 21 having a cyclone outer cylinder diameter of about 1000 mm removes dust particles of about 10 μm or more. The limit particle size of soot and dust that the cyclone removes affects the size of the outer cylinder diameter. When it is large, the amount of processing gas is large, but the limit particle size that can be removed is also large, and the removal rate decreases. The material of the cyclone 21 is a heat resistant material, for example, the outer wall is stainless steel or a steel plate, but the inner wall is lined with a refractory material such as silica or alumina, and is housed in the pressure vessel 2.

The outer diameter of the multi-cyclone 31 is smaller than that of the cyclone 2 by an order of magnitude, and a plurality of small-diameter cyclones of about 100 mm are installed in parallel. The multi-cyclone 31 removes dust particles of 3 to 5 μm or more. .

Here, individual cyclone shapes used in the multi-cyclone of the present invention will be described with reference to FIGS. In FIG. 2, reference numeral 32 denotes a gas inlet,
It is located on the upper part of the dust separation cylinder 34 and has a structure in which gas flows in a tangential direction. Reference numeral 35 is a dust separator, and the outer periphery of the dust separator 35 and the dust separating cylinder 34 have a space of several mm for the dust to flow down. The soot and dust separator 35 has an upwardly convex triangular pyramid shape having a small hole in the center and has a structure in which the soot and dust easily flows down so that the gas separator and the gas separation cylinder do not become blocked by the separated soot and dust. I have to. Reference numeral 36 is a support frame for the dust separator, and 37 is a gas buffer cylinder. The gas flowing in through the inlet 32 descends while swirling in the separation cylinder 34 as indicated by the arrow 32 ′, reverses and rises near the tip of the dust separator 35, and is discharged through the outlet 33. On the other hand, the soot and dust descends along the inner wall of the separation cylinder due to the centrifugal force.

When a plurality of individual cyclones are arranged in parallel, it is difficult to evenly distribute the gas to the individual cyclones. Therefore, the gas buffer cylinder improves the separation so that the separated dust is not re-scattered. Acts like. That is, since the separated dust and soot loses its turning force in the buffer cylinder and descends due to gravity settling, interference between adjacent cyclones is suppressed.

Further, as shown by the arrow 38, blowdown is performed to remove a part of the gas from the cyclone hopper, so that the separating effect of the multi-cyclone can be further exerted. In FIG. 1, the passage of the gas introduced into the filter 6 is a blowdown flow path.

FIG. 3 shows an example in which the buffer cylinder has a cylindrical shape.
Shows a modification in which the dust separator has a cross shape. The cruciform separator has the effect of extinguishing the swirling flow of gas, and is effective in preventing re-scattering of separated and collected dust. Figure 5
2 is a view taken along the line AA 'in FIG. 2, and FIG. 6 is a view taken along the line BB' in FIG.

FIG. 7 shows an example of the structure of the multi-cyclone 31. 311 indicates a gas inlet, 312 indicates a gas outlet,
Reference numeral 313 denotes a partition plate that shields the individual inlet portions 32 of the cyclone and the separated dust, and reference numeral 314 denotes a partition plate that shields the gas inlet portion 32 and the gas outlet portion 33. As described above, the gas containing dust that has flowed in through the gas inlet 311 is
Most of the soot and dust that have flowed in from the individual cyclone inlets 32 are separated and removed and collected in the hopper 315, and the gas is discharged from the outlets 33 and the outlets 312 of the multi-cyclone.
More discharged to the flue.

The gas discharged from the multi-cyclone 31 drives the gas turbine 4 and the energy of pressure and temperature disappears. The gas flowing out from the gas turbine 4 is introduced into the dust collector 8 via the air heater 7.

8 and 9 show an embodiment of the charging device 81. FIG. 8 shows a charging device in which the heater 83 is provided inside the ground electrode 802. 801 is a discharge electrode, 802 is a ground electrode, and when a voltage is charged from the high voltage power supply 84 to both ends of the discharge electrode 801 and the ground electrode 802, corona discharge occurs between both electrodes and a large number of ions are generated. Dust passing through the corona discharge field is charged with ions. The electric resistance of the soot and dust passing through the discharge field is determined by the type of coal and the fluid medium. When limestone, which is the fluid medium, is mixed into the soot and dust, the electrical resistance becomes high. Discharge is significantly hindered. The electric resistance of soot and dust depends on temperature, and has the property of decreasing with increasing temperature. Utilizing this characteristic, the grounding electrode is provided with a heater 83, and when an abnormality occurs in the discharge, the grounding electrode is heated via a temperature controller to lower the electric resistance of the adhering dust and particles so that stable charging is performed. To do.

FIG. 9 shows another embodiment of the charging device, which is a moving electrode type charging device. The effect is that the dust and dirt adhering to the ground electrode is scraped off with a brush, so that the ground electrode is always kept clean and stable discharge is achieved. 91
Is a discharge electrode, 92 is a ground electrode, and this ground electrode 92 can be moved by a rotating drum 93. The portion where the discharge electrode 91 is laid is a gas passage, and the gas is from above in the direction perpendicular to the paper surface.
Or flow from below. 95 and 95 'are partition plates 9
6, 96 'is a chamber which is isolated from the gas passage, in which dust and dirt adhering to the ground electrode 92 can be scraped off by the brush 94.

As described above, even if dust having a high electric resistance is used, the dust can be effectively charged. Next, the trapping property of charged dust on the filter will be described.

FIG. 10 shows an example of the dust collection state on the filter when no charge is applied to the dust, which is not related to the present invention. Reference numeral 82 denotes a filter, and 101 denotes soot and dust. The particle size of the soot and dust introduced into the filter 82 is the residue after the majority of the soot and dust has already been removed by the multi-cyclone, and since it is fine with an average diameter of about 1 μm, the particles adhere to each other when collected by the filter. However, the ventilation resistance increases in a short time.

FIG. 11 shows the state of collection when dust is charged, according to the present invention. Reference numeral 102 denotes charged particles. When the particles are collected by the filter 82, the particles have the same electric charge, and therefore repel each other and adhere to each other in a chain shape, whereby the ventilation resistance can be significantly reduced. Giving an electric charge to dust not only reduces the ventilation resistance but also
The collection efficiency of the filter is also improved. In particular, when the filter is clean, the charging effect is remarkable.

As described above, the dust removal system of the present invention is
For the high temperature and high pressure exhaust gas flowing into the gas turbine 4, a cyclone dust collection method applying centrifugal separation is adopted,
The characteristic feature of the exhaust gas of the gas turbine 4, that is, the electrostatic precipitating method is adopted at low temperature and low pressure.

In the present embodiment, the dust collector 8 has been described as a filtration type, but the electric dust collector is a moving electrode type electrostatic dust collector shown in FIG. 9 as a system capable of dealing with high and low electric resistance of dust. By adopting, it is possible to achieve the dust collection performance equivalent to that of the filtration method.

[0034]

According to the dedusting system of the present invention, high-temperature dedusting is highly reliable, and high-resistance dust and soot can be efficiently removed. Therefore, reliability of operation of the pressurized fluidized bed boiler power plant is improved. It is possible to provide a power plant that is enhanced and can stably supply electric power, and that is also friendly to the atmospheric environment.

[Brief description of drawings]

FIG. 1 is an explanatory view of an embodiment of a dedusting system for a pressurized fluidized bed boiler power plant of the present invention.

FIG. 2 is an individual cyclone configuration diagram of the multi-cyclone of the present invention.

FIG. 3 is an explanatory view of another embodiment of the cyclone.

FIG. 4 is an explanatory view of another embodiment of the cyclone.

5 is an AA ′ view of FIG.

6 is a BB ′ view of FIG. 4. FIG.

FIG. 7 is an explanatory diagram of an embodiment of the multi-cyclone of the present invention.

FIG. 8 is a schematic view of a heating electrode type charging device.

FIG. 9 is a schematic diagram of a moving electrode type charging device.

FIG. 10 is a schematic view of a dust collection state on a filter when not charged.

FIG. 11 is a schematic view of a dust collection state on a filter during charging.

[Explanation of symbols]

1 ... Pressure fluidized bed boiler, 21 ... Single cyclone, 3
1 ... Multi-cyclone, 35 ... Dust separator, 37 ...
Gas buffer cylinder, 4 ... Gas turbine, 8 ... Dust collector, 81 ...
Charging device, 82 ... Bag filter.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Shinichi Tomuro, 7-1, 1-1, Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor, Masato Machida 3-chome, Saiwai-cho, Hitachi-shi, Ibaraki No. 1 No. 1 Stock Company Hitachi Ltd. Hitachi factory

Claims (11)

[Claims] 1. A pressurized fluidized bed boiler combined cycle power generation plant having a pressurized fluidized bed boiler, a steam turbine generator and a gas turbine generator, wherein dust in the exhaust gas of the pressurized fluidized bed boiler is removed by a large-diameter cyclone. After that, an electrostatic precipitator for removing fine dust that could not be removed by the multi cyclone is introduced into the gas turbine outlet flue by removing it with a small caliber multi cyclone equipped with a gas buffer cylinder. A dedusting system for a pressurized fluidized bed boiler combined cycle power plant characterized by being equipped. 2. In a pressurized fluidized bed boiler combined cycle power plant, soot and dust in boiler exhaust gas are removed by a centrifugal dust collection method in a high temperature / high pressure exhaust gas area and an electrostatic dust collection method in a low temperature / low pressure area. A dedusting system for a pressurized fluidized bed boiler combined cycle power plant, which is characterized in that 3. A blowdown system for sucking a part of exhaust gas from a hopper of a small-diameter multi-cyclone according to claim 1 and discharging the exhaust gas to a flue on the downstream side of the multi-cyclone. Dedusting system. 4. The small-diameter multicyclone according to claim 1, wherein the small-diameter multicyclone is provided with a dust buffer cylinder below the dust separator. 5. The small-diameter multi according to claim 4, wherein the dust separator of the small-diameter multi-cyclone is a convex conical shape having a small hole in the center, or a cruciform separator, for example. Cyclone. 6. The small diameter multi-cyclone according to claim 4, wherein a gas buffer cylinder is provided below the dust separator of the small diameter multi-cyclone. 7. The electrostatic precipitator according to claim 1 is composed of a charging device for giving an electric charge to the dust and a bag filter for removing the charged dust in the charging device. Dust removal system. 8. The static charging device according to claim 7, wherein the charging device comprises a discharging electrode and a grounding electrode facing the discharging electrode, and is equipped with a scraping device for removing dust and dirt adhering to the grounding electrode. Electrostatic precipitator. 9. The charging device comprises a discharge electrode and a ground electrode facing the discharge electrode, and the ground electrode is equipped with a heating device capable of adjusting the surface of the ground electrode to an arbitrary temperature. The electrostatic dust collector according to claim 7. 10. The electrostatic precipitator according to claim 7, wherein the bag filter of the precipitator is a filter which becomes an electrically insulating material. 11. An electrostatic precipitator according to claim 1 is an electrostatic precipitator comprising a discharge electrode and a dust collecting electrode, wherein the discharge electrode is a fixed pole, and the dust collecting pole is provided with an operating part. The dust removing system according to claim 1, further comprising a device for scraping off the dust collected on the dust collecting electrode with a brush.