JP6627310B2 - Coal-fired power plant - Google Patents

Description

  The present invention relates to a coal-fired power generation facility. More specifically, the present invention relates to a coal-fired power generation facility capable of suppressing deterioration of a denitration catalyst constituting a denitration device.

  In a coal-fired power plant, nitrogen oxides are generated by the burning of coal, but it is necessary to keep the emission of nitrogen oxides below a certain level by the Air Pollution Control Law. Therefore, power plants are equipped with denitration equipment to reduce and decompose nitrogen oxides. In this denitration apparatus, a denitration catalyst containing an active component such as vanadium pentoxide is disposed, and by coexisting ammonia here, denitration is realized by a reduction reaction at a high temperature.

  Since this denitration catalyst generally operates efficiently in a high-temperature atmosphere of 300 ° C. to 400 ° C., it is necessary to denitrate exhaust gas containing a very large amount of dust immediately after burning coal in a boiler. In order to maintain the performance of the denitration device, it is necessary to replace the catalyst with reduced activity with a new catalyst or to regenerate the catalyst.

  For example, Patent Literature 1 below discloses a method of replacing a denitration catalyst of a flue gas denitration apparatus in which a denitration catalyst is filled in a plurality of stages, and a catalyst removal step of removing a first-stage denitration catalyst located on the most upstream side. And a catalyst moving step of sequentially moving all the denitration catalysts of the second and subsequent stages to the first stage upstream, and a catalyst for replenishing a new denitration catalyst in the lowermost stage that has been moved and emptied by the catalyst moving step. A method for replacing a denitration catalyst including a replenishing step is disclosed.

JP 2013-052335 A

  However, in the first place, there is no knowledge about when to replace or regenerate the denitration catalyst. For this reason, the present situation is to measure the decrease in the denitration rate by measuring the exhaust gas on site or actually collecting a catalyst sample and conducting a catalyst performance test or the like. Since the deterioration of the function of the denitration catalyst in the operation of coal-fired power plants gradually progresses over a long period of time, it is extremely important to clarify this deterioration mechanism in predicting deterioration and taking measures to control deterioration. It is.

  The present inventors have conducted intensive studies on the deterioration mechanism of the denitration catalyst, and found that a deposit having a particle size much smaller than the range of the conventional coal ash having a particle size of about several tens μm to about 100 μm was obtained. It was found that the surface of was coated to form a coating layer, whereby the contact between the denitration catalyst and the exhaust gas was hindered, and the performance of the denitration catalyst was reduced.

  Accordingly, an object of the present invention is to provide a coal-fired power generation facility capable of suppressing deterioration of a denitration catalyst by preventing a deposit having a small particle size from covering the surface of the denitration catalyst.

  The present invention provides a pulverized coal machine for pulverizing coal to produce pulverized coal, a fine coal removal device disposed downstream of the pulverized coal machine to remove fine coal as fine pulverized coal, and the fine coal removal device. A combustion boiler for burning pulverized coal from which fine coal has been removed in a device, and a denitrification device disposed downstream of the combustion boiler for removing nitrogen oxides contained in exhaust gas generated by burning the pulverized coal in the combustion boiler And a coal-fired power plant comprising the same.

  In addition, it is preferable that the fine coal removal device is a cyclone separation device that introduces fine coal together with air and separates fine coal contained in the fine coal by centrifugal force.

  Further, it is preferable that the fine charcoal removing device is a classifying device including a plurality of mesh layers having mesh portions having different sizes.

  Further, it is preferable that the fine coal removing device has an ability to remove pulverized coal having a size of less than 2 μm as fine coal.

  ADVANTAGE OF THE INVENTION According to this invention, the coal-fired power generation equipment which can suppress deterioration of a denitration catalyst by preventing that the deposit of a small particle size coats the surface of a denitration catalyst can be provided.

It is a figure showing composition of a coal-fired power generation facility concerning one embodiment of the present invention. It is a figure which shows typically the structure of the cyclone separation apparatus as a micro coal removal apparatus. It is a figure showing typically composition of a classification device as a minute charcoal removal device. It is a figure which expands and shows the vicinity of the combustion boiler shown in FIG. It is a figure which expands and shows the denitration apparatus shown in FIG.

Hereinafter, a preferred embodiment of a coal-fired power generation facility of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the coal-fired power plant 1 of the present embodiment includes a coal bunker 20, a coal feeder 25, a pulverized coal machine 30, a fine coal removal device 10, a combustion boiler 40, and a combustion boiler 40. An exhaust passage 50 provided on the downstream side of the apparatus, and a denitration device 60, an air preheater 70, an electric dust collector 90, a gas heater (for heat recovery) 80, an induced draft fan 210, a desulfurization device provided in the exhaust passage 50 220, a gas heater (for reheating) 230, a desulfurization ventilator 240, and a chimney 250.

The coal bunker 20 stores coal supplied by a coal transportation facility from a coal silo (not shown). The coal feeder 25 supplies the coal supplied from the coal bunker 20 to the pulverized coal machine 30 at a predetermined supply speed.
The pulverized coal machine 30 pulverizes the coal supplied from the coal feeder 25 to produce pulverized coal. In the pulverized coal machine 30, the coal is pulverized to an average particle size of 60 μm to 80 μm. The particle size distribution of pulverized coal is about 10 to 15% for 150 μm or more, about 30 to 40% for 75 μm to 150 μm, and about 45 to 60% for less than 75 μm.
As the pulverized coal machine 30, a roller mill, a tube mill, a ball mill, a beater mill, an impeller mill, or the like is used.

The fine coal removing device 10 is disposed downstream of the pulverized coal machine 30 and removes fine coal as fine pulverized coal. Here, the fine coal means fine coal having a particle size of less than 2 μm.
That is, in the pulverized coal machine 30, pulverized coal having a particle size of less than 75 μm is included in an amount of about 45 to 60%. Micro charcoal).

In the present embodiment, the fine charcoal removing device 10 removes the fine charcoal, thereby suppressing the deterioration of the denitration catalyst described later.
As the fine coal removal device 10, a cyclone separation device 10A as shown in FIG. 2 and a classification device 10B as shown in FIG. 3 can be suitably used.

As shown in FIG. 2, the cyclone separation device 10A includes a conical main body whose apex faces downward, and classifies pulverized coal introduced with air into the main body by centrifugal force. Then, pulverized coal having a large particle diameter (in this embodiment, pulverized coal having a particle diameter of 2 μm or more) is collected below and supplied to the combustion boiler 40 together with air.
Further, pulverized coal having a small particle size (fine coal having a particle size of less than 2 μm) is collected at an upper portion of the main body.

  Further, as shown in FIG. 3, the classifier 10B includes a plurality of mesh layers 11, 12, and 13 having meshes of different sizes. The size of the mesh portion is configured to decrease from the upper mesh layer 11 to the lower mesh layer 13. In the present embodiment, the mesh portion of the upper mesh layer 11 into which pulverized coal is first introduced together with air from the pulverized coal machine 30 is configured to have a mesh size of 45 μm, and the mesh portion of the middle mesh layer 12 has a mesh size of 20 μm. Is configured. The mesh portion of the lower mesh layer 13 has a mesh size of 2 μm.

According to the above classifier 10B, the pulverized coal produced by the pulverized coal machine 130 is first introduced into the upper mesh layer 11, where the pulverized coal having a particle size of 45 μm or more is captured, and the fine powder having a particle size of less than 45 μm is added. The charcoal is sent to the middle mesh layer 12.
In the middle mesh layer 12, pulverized coal having a particle size of 20 μm or more is captured, and pulverized coal having a particle size of less than 20 μm is sent to the lower mesh layer 13.
In the lower mesh layer 13, pulverized coal having a particle size of 2 μm or more is captured, and pulverized coal having a particle size of less than 2 μm is collected.
The pulverized coal captured by the mesh layers 11, 12, 13 is supplied to the combustion boiler 40 together with air.

The combustion boiler 40 burns the pulverized coal supplied from the fine coal removal device 10 together with the forcibly supplied air. Combustion of the pulverized coal generates coal ash such as clinker ash and fly ash, and also generates exhaust gas.
The clinker ash is a lump of coal ash that has fallen to the bottom of the combustion boiler 40 among coal ash generated when pulverized coal is burned. Further, fly ash is a coal ash generated when pulverized coal is burned and has a particle size (particle size of about 200 μm or less) that is blown up together with a combustion gas (exhaust gas) and flows to the exhaust passage 50 side. It refers to spherical coal ash.

  Referring to FIG. 4, the combustion boiler 40 will be described in detail. In FIG. 4, the combustion boiler 40 has a substantially inverted U-shape as a whole, and the exhaust gas (combustion gas) is inverted U-shaped along the arrow in the figure. After passing through the secondary economizer 41e, it is again inverted into a small U-shape.

  Below the combustion boiler 40, a burner 41a for burning pulverized coal near the burner zone 41a 'inside the combustion boiler 40 is arranged. A first superheater 41b is arranged near the U-shaped top inside the combustion boiler 40, and a second superheater 41c is further arranged therefrom. Further, from the vicinity of the end of the second superheater 41c, a primary economizer 41d and a secondary economizer 41e are provided in two stages. Here, the economizer (also referred to as ECO) is a group of heat transfer surfaces provided for preheating boiler feedwater using heat of exhaust gas.

According to the combustion boiler 40 described above, pulverized coal is burned in the burner zone 41a '. The combustion temperature of the pulverized coal ranges from 1300 ° C. to 1500 ° C., and the coal ash generated by the combustion rises along the direction of the arrow, and together with the exhaust gas, the first superheater 41b and the second superheater 41c, 1c. It sequentially passes through the next economizer 41d and the secondary economizer 41e. The combustion gas exchanges heat by passing through a group of heat transfer surfaces provided for preheating the boiler feedwater, and the temperature drops to about 450 to 500 ° C. The time required for the exhaust gas to reach from the burner zone 41a 'to the vicinity of the economizer is about 5 to 10 seconds.
Here, in this embodiment, since the pulverized coal (fine coal) having a particle size of less than 2 μm is removed by the fine coal removal device 10, fine coal ash (particle size of 1 μm or less) contained in the generated coal ash is removed. ) Can be reduced.

  The exhaust passage 50 is disposed downstream of the combustion boiler 40, and allows exhaust gas generated in the combustion boiler 40 and generated coal ash to flow. As described above, the exhaust passage 50 includes a denitration device 60, an air preheater 70, a gas heater (for heat recovery) 80, an electric precipitator 90, an induction ventilator 210, a desulfurization device 220, and a gas heater (for reheating). ) 230, a desulfurization ventilator 240, and a chimney 250 are arranged in this order.

  The denitration device 60 removes nitrogen oxides in the exhaust gas. In the present embodiment, the denitration apparatus 60 injects ammonia gas as a reducing agent into exhaust gas at a relatively high temperature (300 ° C. to 400 ° C.), and converts nitrogen oxides in the exhaust gas into harmless nitrogen by the action of the denitration catalyst. Nitrogen oxides in exhaust gas are removed by a so-called dry ammonia catalytic reduction method that decomposes into steam.

  As shown in FIG. 5, the denitration apparatus 60 includes a denitration reactor 61, a plurality of stages of denitration catalyst layers 62, 62, 62 disposed inside the denitration reactor 61, and an upstream side of the denitration catalyst layer 62. A rectifying layer 63 is disposed, a rectifying plate 64 disposed near the inlet of the denitration reactor 61, and an ammonia injection section 65 disposed upstream of the denitration reactor 61.

The denitration reactor 61 is a place for a denitration reaction in the denitration device 60.
The denitration catalyst layers 62 are arranged inside the denitration reactor 61 at a plurality of stages (three stages in the present embodiment) at predetermined intervals along the flow path of the exhaust gas.

The denitration catalyst layer 62 is configured to include a plurality of honeycomb catalysts (not shown) as denitration catalysts. The honeycomb catalyst is formed in a long shape (a rectangular parallelepiped shape) in which a plurality of exhaust gas flow holes extending in the longitudinal direction are formed. The plurality of honeycomb catalysts are arranged such that the exhaust gas flow holes are along the flow path of the exhaust gas. As the honeycomb catalyst, for example, a catalyst having a rectangular parallelepiped shape of 150 mm x 150 mm x 860 mm and having 400 (20 x 20) exhaust gas flow holes with openings of 6 mm x 6 mm is used. Further, for example, 9000 to 10000 honeycomb catalysts are installed in one layer of the denitration catalyst layer 62.
The honeycomb catalyst is formed by supporting a catalyst substance such as vanadium or tungsten on a ceramic material such as titanium oxide or zirconium oxide and then extruding the catalyst.

  The rectification layer 63 is arranged on the upstream side of the denitration catalyst layer 62. The rectifying layer 63 is formed of a metal member or the like having a plurality of openings formed in a lattice, and divides a flow path of exhaust gas in the denitration reactor 61. The rectification layer 63 rectifies the exhaust gas flowing through the exhaust passage 50 and introduced into the denitration reactor 61, and uniformly guides the exhaust gas to the denitration catalyst layer 62.

  The rectifying plate 64 is arranged near the inlet of the denitration reactor 61 and on the upstream side of the rectifying layer 63. More specifically, the current plate 64 is disposed at a bent portion of the inner wall of the denitration reactor 61 or the exhaust passage 50, and protrudes from the inner wall to the inner surface side. The current plate 64 regulates the flow of the exhaust gas at the bent portion of the exhaust passage 50 or the denitration reactor 61.

  The ammonia injection section 65 is arranged on the upstream side of the denitration reactor 61 and injects ammonia into the exhaust passage 50.

  According to the above denitration apparatus 60, first, in the ammonia injection section 65, ammonia is injected into the high-temperature exhaust gas (300 ° C. to 400 ° C.) flowing through the exhaust passage 50. The exhaust gas into which ammonia has been injected is rectified by the rectifying plate 64 and the rectifying layer 63, and is introduced into the denitration catalyst layer 62.

In the denitration catalyst layer 62, when the exhaust gas containing ammonia passes through the exhaust gas flow hole of the honeycomb catalyst, the nitrogen oxide and ammonia react with each other according to the following chemical reaction formula, and are decomposed into harmless nitrogen and water vapor. .
4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O
NO + NO ₂ + 2NH ₃ → 2N ₂ + 3H ₂ O

  Here, the denitration catalyst is deteriorated by use and the denitration rate is reduced. Causes of the deterioration of the denitration catalyst include thermal deterioration such as sintering, chemical deterioration due to poisoning of the catalyst component, and physical deterioration due to coal ash covering the catalyst surface. The present inventors have recently found that the particle size of coal ash (1 μm or less, more specifically, several tens nm) is much smaller than the average particle size of coal ash in the range of several tens μm to 100 μm. It has been found that the deposits caused by the coal ash cover the surface of the denitration catalyst to form a coating layer, whereby the contact between the denitration catalyst and the exhaust gas is inhibited and the performance of the denitration catalyst is reduced. Since the content of the coal ash having such a small particle size is small, it has not been considered as a cause of deterioration of the denitration catalyst.

  Therefore, in the present embodiment, the coal-fired power plant 1 is configured to include the fine coal removal device 10 that removes pulverized coal having a particle size of less than 2 μm. As a result, the pulverized coal containing no pulverized coal (fine coal) having a particle size of less than 2 μm can be burned in the combustion boiler 40. Can be reduced. Therefore, it is possible to prevent the formation of the coating layer caused by the minute coal ash on the surface of the honeycomb catalyst (denitration catalyst), and it is possible to suppress the deterioration of the honeycomb catalyst.

  The air preheater 70 is disposed downstream of the denitration device 60 in the exhaust passage 50. The air preheater 70 exchanges heat between the exhaust gas passing through the denitration device 60 and the combustion air sent from the push-type ventilator 75, thereby cooling the exhaust gas and heating the combustion air.

  The gas heater 80 is disposed downstream of the air preheater 70 in the exhaust passage 50. The exhaust gas heat recovered in the air preheater 70 is supplied to the gas heater 80. The gas heater 80 further recovers heat from the exhaust gas.

  The electric precipitator 90 is disposed downstream of the gas heater 80 in the exhaust passage 50. The exhaust gas heat recovered by the gas heater 80 is supplied to the electric dust collector 90. The electric precipitator 90 is a device that collects coal ash (fly ash) in exhaust gas by applying a voltage to an electrode. The fly ash collected by the electric dust collector 90 is collected by the fly ash collecting device 120.

  The induction ventilator 210 is arranged downstream of the electric precipitator 90 in the exhaust passage 50. The induction ventilator 210 takes in the exhaust gas from which fly ash has been removed in the electric precipitator 90 from the primary side and sends it out to the secondary side.

  The desulfurization device 220 is arranged in the exhaust passage 50 on the downstream side of the induction ventilator 210. The exhaust gas sent from the induction ventilator 210 is supplied to the desulfurization device 220. The desulfurization device 220 sprays a mixed solution of limestone and water on the exhaust gas to absorb the sulfur oxides contained in the exhaust gas into the mixed solution to generate a desulfurized gypsum slurry, and performs a dehydration treatment on the desulfurized gypsum slurry. This produces desulfurized gypsum. The desulfurized gypsum generated in the desulfurization device 220 is recovered by a desulfurized gypsum recovery device 222 connected to the device.

  The gas heater 230 is disposed downstream of the desulfurization device 220 in the exhaust passage 50. The exhaust gas from which the sulfur oxides have been removed in the desulfurization device 220 is supplied to the gas heater 230. The gas heater 230 heats the exhaust gas. The gas heater 80 and the gas heater 230 are disposed between the exhaust gas flowing between the air preheater 70 and the electrostatic precipitator 90 and the exhaust gas flowing between the desulfurization device 220 and the desulfurization ventilator 240 in the exhaust passage 50. May be configured as a gas gas heater that performs heat exchange.

The desulfurization ventilator 240 is disposed downstream of the gas heater 230 in the exhaust passage 50. The desulfurization ventilator 240 takes in the exhaust gas heated by the gas heater 230 from the primary side and sends it to the secondary side.
The chimney 250 is disposed downstream of the desulfurization ventilator 240 in the exhaust passage 50. The exhaust gas heated by the gas heater 230 is introduced into the chimney 250. The chimney 250 discharges exhaust gas.

  According to the coal-fired power plant 1 of the present embodiment described above, the following effects can be obtained.

  (1) The coal-fired power generation facility 1 was configured to include a fine coal removal device 10 for removing pulverized coal having a particle size of less than 2 μm. As a result, the pulverized coal containing no pulverized coal (fine coal) having a particle size of less than 2 μm can be burned in the combustion boiler 40. Can be reduced. Therefore, it is possible to prevent the formation of the coating layer caused by the minute coal ash on the surface of the honeycomb catalyst (denitration catalyst), and it is possible to suppress the deterioration of the honeycomb catalyst.

  (2) The fine coal removal device 10 is constituted by a cyclone separation device 10A in which pulverized coal is introduced together with air and separates fine coal contained in the pulverized coal by centrifugal force. Thus, by arranging the cyclone separator 10A in the flow path that supplies the pulverized coal produced in the pulverized coal machine 30 to the combustion boiler 40 together with the air, the fine coal contained in the pulverized coal can be suitably removed. Therefore, it is possible to suppress the deterioration of the denitration catalyst without significantly changing the design of the coal-fired power generation facility 1.

  (3) The fine charcoal removing device 10 was constituted by a classifying device 10B including a plurality of mesh layers 11, 12, 13 having mesh portions of different sizes. Thus, by arranging the classifier 10B in the flow path for supplying the pulverized coal produced in the pulverized coal machine 30 to the combustion boiler 40 together with the air, the fine coal contained in the pulverized coal can be suitably removed. Therefore, it is possible to suppress the deterioration of the denitration catalyst without significantly changing the design of the coal-fired power generation facility 1. In addition, by configuring the classification device 10B to include the plurality of mesh layers 11, 12, and 13, the classification accuracy of the fine coal can be improved.

  (4) The pulverized coal having a size of less than 2 μm was removed by the pulverized coal removing apparatus 10 as pulverized coal. Thereby, the ratio of the coal ash having a particle size of less than 1 μm contained in the coal ash generated by burning the pulverized coal can be suitably reduced.

As described above, the preferred embodiment of the coal-fired power plant 1 of the present invention has been described, but the present invention is not limited to the above-described embodiment, and can be appropriately changed.
For example, in the present embodiment, a honeycomb catalyst is used as the denitration catalyst, but the present invention is not limited to this. That is, a plate-like catalyst formed by applying a catalytic substance to the surface of a net-like base material may be used as the denitration catalyst.

  Further, in the present embodiment, the pulverized coal having a size of less than 2 μm is removed as the pulverized coal by the pulverized coal removing device 10, but is not limited thereto. That is, the pulverized coal having a size of less than 5 μm may be removed by the pulverized coal removing apparatus as the pulverized coal.

DESCRIPTION OF SYMBOLS 1 Coal-fired power generation equipment 10 Micro coal removal equipment 10A Cyclone separation equipment 10B Classifier 30 Pulverized coal machine 40 Combustion boiler 60 Denitration equipment

Claims (4)

A pulverized coal machine that pulverizes coal to produce pulverized coal,
A fine coal removal device that is disposed downstream of the pulverized coal machine and removes fine coal that is fine pulverized coal,
A combustion boiler that burns the pulverized coal from which the fine coal has been removed in the fine coal removal device and does not burn the fine coal removed by the fine coal removal device ,
A denitrification device disposed downstream of the combustion boiler to remove nitrogen oxides contained in exhaust gas generated by burning pulverized coal in the combustion boiler.   The coal-fired power plant according to claim 1, wherein the fine coal removal device is a cyclone separation device that introduces pulverized coal together with air and separates fine coal included in the pulverized coal by centrifugal force.   The coal-fired power plant according to claim 1, wherein the fine coal removal device is a classification device including a plurality of mesh layers having meshes of different sizes.   The coal-fired power generation facility according to any one of claims 1 to 3, wherein the fine coal removal device has an ability to remove pulverized coal having a size of less than 2 µm as fine coal.

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