Classifier, power generation plant, and method for operating a classifier

Abstract

To improve classification performance.SOLUTION: A rotary typed classifier 16 classifies pulverized solid fuel introduced with primary air into coarse powder fuel B1 whose diameter is larger than a prescribed particle size and fine powder fuel B2 whose diameter is the prescribed particle size or less. The rotary typed classifier 16 includes a plurality of blades 60 which extend in a vertical direction, are arrayed in a circumferential direction of a virtual circle V around a center axis C extending in a vertical direction, and introduce solid fuel with carrier gas from outside in a radial direction to inside. The blade 60 has a collision surface 61 with which the pulverized fuel collides so that the coarse powder fuel B1 of the collided pulverized fuel whose diameter is larger than a prescribed particle size is repelled to outside in a radial direction, and the fine powder fuel B2 thereof whose diameter is the prescribed particle size or less is repelled to inside in a radial direction. An angle between a tangent line of the virtual circle V and a perpendicular line to the collision surface 61 is larger in a radially outside direction than that in a radially inside direction.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a classifier, a power generation plant, and an operation method of the classifier.

Background Art

[0002] Conventionally, solid fuels such as coal and biomass fuels (carbon-containing solid fuels) are pulverized into fine powders within a predetermined particle size range by a pulverizer (mill) and supplied to a combustion device. The mill sandwiches solid fuels such as coal and biomass fuels input to a pulverizing table between the pulverizing table and a pulverizing roller to pulverize them, and among the solid fuels pulverized into fine powders (hereinafter, the pulverized solid fuels are referred to as "pulverized fuels") by conveying gas (primary air) supplied from the outer periphery of the pulverizing table, fine pulverized fuels within a predetermined particle size range (fineness) are selected by a classifier, conveyed to a boiler, and burned in a combustion device. In a thermal power generation plant, steam is generated by heat exchange with combustion gas generated by burning fine pulverized fuel in a boiler, and the steam rotates a steam turbine to rotationally drive a generator connected to the steam turbine, thereby generating electricity.

[0003] As one of the classifiers provided in a mill, for example, a rotary classifier is known. The rotary classifier has a plurality of blades arranged at equal intervals in the circumferential direction around a rotation axis. When the pulverized fuel passes between the plurality of blades rotating around the rotation axis, the coarse pulverized fuel (pulverized fuel larger than a predetermined particle size) with a large weight and a large centrifugal force acting thereon is bounced to the outer peripheral side of the blade, and the fine pulverized fuel (pulverized fuel smaller than a predetermined particle size) with a small weight and a large conveying force by the airflow of the primary air acting thereon passes to the inner peripheral side of the blade, thereby performing classification. In addition, the rotary classifier has a main body that rotates about a rotation axis. By holding the upper and lower parts of the blades, the main body can revolve the blades about the rotation axis. The main body is held by bearings and rotates at a predetermined rotational speed by a power source such as a motor. By changing this rotational speed, the force acting on the pulverized fuel can be adjusted, and a predetermined fineness (classification performance) can be obtained.

[0004] Generally, the blades of a rotary classifier are in a flat plate shape. However, for the purpose of improving classification performance (the performance of bouncing coarse powder fuel to the outer peripheral side of the blades and passing fine powder fuel through between the blades), the blades of the rotary classifier may be shaped other than simply flat (for example, Patent Document 1). Patent Document 1 describes a rotary classification device in which, at the upstream end (inlet end) of a plurality of classification vanes rotating around a vertical axis, the angle formed with the radial direction of the rotation radius is large, and at the downstream end (outlet end), this angle is small. That is, Patent Document 1 describes a rotary classification device in which the classification vanes are bent.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] The classification blades (blades) described in Patent Document 1 are bent so that the angles (angles with respect to the radial direction) are different between the inlet side portion (outer portion in the radial direction) and the outlet side portion (inner portion in the radial direction). Generally, the particle size range of the pulverized fuel that can bounce to the outer peripheral side varies depending on the angle of the blade. For this reason, in the blade described in Patent Document 1, pulverized fuel with an intermediate particle size that can bounce to the outer peripheral side at the inlet side portion of the blade may collide with the blade, but cannot bounce to the outer peripheral side at the outlet side portion. In this case, the classification results will be significantly different depending on whether it collides with the outlet side portion or the inlet side portion. Whether it collides with the inlet side portion or the outlet side portion of the blade is determined by the intrusion position of the pulverized fuel into the rotary classifier. Specifically, when it intrudes into the rotary classifier from a distance in the radial direction of the blade, it collides with the outlet side portion, and when it intrudes into the rotary classifier from the vicinity of the radial direction of the blade, it collides with the inlet side portion.

[0007] Thus, in the device described in Patent Document 1, when pulverized fuel with an intermediate particle size intrudes into the rotary classifier from a distance from the blade and collides with the inlet side portion of the blade, the collided pulverized fuel is bounced to the outer peripheral side and returned to the pulverizing section (pulverizing table). On the other hand, when pulverized fuel with an intermediate particle size intrudes into the rotary classifier from the vicinity of the blade and collides with the outlet side portion of the blade, the collided pulverized fuel passes through to the inner peripheral side and is led to the boiler. Since it is difficult to control the intrusion position of the pulverized fuel into the rotary classifier, in the device described in Patent Document 1, for pulverized fuel with an intermediate particle size, whether it collides with the inlet side portion and is bounced to the outer peripheral side or collides with the outlet side portion and passes through to the inner peripheral side is random with respect to the particle size. That is, even for pulverized fuel with the same particle size, cases where it is classified (bounced to the outer peripheral side) and cases where it is not classified (bounced to the inner peripheral side) will occur. For this reason, it becomes impossible to accurately classify the pulverized fuel according to the target particle size, that is, there was a possibility that the classification performance would deteriorate. In particular, the greater the difference in the angles between the inlet-side portion and the outlet-side portion, the larger the particle size range in which whether the particles are classified or not becomes random with respect to the particle size, and thus the degradation of the classification performance was significant. Further, even when the rotational speed of the blade was changed, only the upper limit or the lower limit of the particle size range in which whether the particles are classified or not becomes random with respect to the particle size changed, and the problem of the degradation of the classification performance could not be solved.

[0008] The present disclosure has been made in view of such circumstances, and an object thereof is to provide a classifier, a power generation plant, and an operation method of the classifier that can improve the classification performance.

Means for Solving the Problems

[0009] In order to solve the above problems, the classifier, the power generation plant, and the operation method of the classifier of the present disclosure employ the following means. A classifier according to an aspect of the present disclosure is a classifier that classifies particles guided together with a conveying gas into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size, and includes a plurality of blades that extend in the vertical direction and are arranged side by side in the circumferential direction on a virtual circle centered on a central axis extending in the vertical direction, and the particles are guided together with the conveying gas from the outer side in the radial direction toward the inner side. The blade has a collision surface on which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer side direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner side direction in the radial direction. The collision surface has a larger angle formed by a tangent line of the virtual circle and a perpendicular line to the collision surface on the outer side in the radial direction than on the inner side in the radial direction.

[0010] A method for operating a classifier according to an aspect of the present disclosure is a method for operating a classifier that classifies particles guided together with a carrier gas into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size. The classifier extends in the vertical direction and includes a plurality of blades arranged circumferentially on a virtual circle centered on a central axis extending in the vertical direction, and the particles are guided together with the carrier gas flowing from the outside in the radial direction toward the inside. The blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction. The collision surface has an angle formed by a tangent line of the virtual circle and a perpendicular line to the collision surface that is larger on the outer side in the radial direction than on the inner side in the radial direction. The method includes a step of classifying the particles into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size by the blade.

Advantages of the Invention

[0011] According to the present disclosure, the classification performance can be improved.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The power generation plant 1 according to this embodiment includes a solid fuel pulverizer 100 and a boiler 200. In the following description, the upper direction refers to the vertically upward direction, and the "upper" such as the upper part or the upper surface indicates the vertically upper part. Similarly, "lower" indicates the vertically lower part, and the vertical direction is not strict and includes errors.

[0014] The solid fuel pulverizer 100 of the present embodiment is, as an example, a device that pulverizes solid fuels (carbon-containing solid fuels) such as coal and biomass fuel, generates pulverized fuel, and supplies it to the burner (combustion device) 220 of the boiler 200. The power generation plant 1 including the solid fuel pulverizer 100 and the boiler 200 shown in FIG. 1 includes one solid fuel pulverizer 100, but may also be a system including a plurality of solid fuel pulverizers 100 corresponding to each of the plurality of burners 220 of one boiler 200.

[0015] The solid fuel pulverizer 100 of the present embodiment includes a mill 10, a coal feeder (fuel supply machine) 20, a blower section (conveying gas supply section) 30, a state detection section 40, and a control section (judgment section) 50.

[0016] The mill 10 that pulverizes solid fuels such as coal and biomass fuel supplied to the boiler 200 into pulverized fuel, which is pulverized solid fuel, may be in a form that pulverizes only coal, may be in a form that pulverizes only biomass fuel, or may be in a form that pulverizes biomass fuel together with coal. Here, biomass fuel is a renewable organic resource derived from organisms. For example, it includes thinned wood, waste wood, driftwood, grasses, waste, sludge, tires, and recycled fuels (pellets and chips) made from these materials, but is not limited to those presented here. Since biomass fuel absorbs carbon dioxide during the growth process of biomass, it is considered carbon-neutral and does not emit carbon dioxide, which is a greenhouse gas, and thus its utilization is being variously studied.

[0017] Mill 10 includes a housing 11, a grinding table (rotating table) 12, grinding rollers 13, a drive unit 14, a mill motor 15 connected to the drive unit 14 for rotationally driving the grinding table 12, a rotary classifier 16, a fuel supply unit 17, and a classifier motor 18 for rotationally driving the rotary classifier 16. The housing 11 is formed in a cylindrical shape extending in the vertical direction and is a housing that accommodates the grinding table 12, the grinding rollers 13, the rotary classifier 16, and the fuel supply unit 17. A fuel supply unit 17 is attached to the central part of the ceiling part 42 of the housing 11. This fuel supply unit 17 supplies the solid fuel led from the bunker 21 into the housing 11, is arranged along the vertical direction at the central position of the housing 11, and its lower end extends to the inside of the housing 11.

[0018] A drive unit 14 is installed near the bottom surface part 41 of the housing 11, and the grinding table 12 that rotates by the driving force transmitted from the mill motor 15 connected to this drive unit 14 is rotatably arranged. The grinding table 12 is a member circular in plan view and is arranged so that the lower end part of the fuel supply unit 17 faces it. The upper surface of the grinding table 12 may have, for example, an inclined shape where the central part is low and it becomes higher toward the outside, and the outer peripheral part may have a shape that bends upward. The fuel supply unit 17 supplies solid fuel (for example, coal or biomass fuel in this embodiment) from above toward the lower grinding table 12, and the grinding table 12 grinds the supplied solid fuel between the grinding rollers 13.

[0019] When the solid fuel is fed from the fuel supply unit 17 toward the substantially central region of the grinding table 12, the centrifugal force generated by the rotation of the grinding table 12 guides the solid fuel toward the outer peripheral side of the grinding table 12, where it is sandwiched between the grinding table 12 and the grinding roller 13 and ground. The ground solid fuel is blown upward by the conveying gas (hereinafter referred to as primary air) introduced from the conveying gas flow path (hereinafter referred to as the primary air flow path) 100a and guided to the rotary classifier 16. On the outer periphery of the grinding table 12, there is provided an air outlet (not shown) for discharging the primary air flowing in from the primary air flow path 100a into the space above the grinding table 12 in the housing 11. A swirler (not shown) is installed at the air outlet to impart a swirling force to the primary air blown out from the air outlet. The primary air imparted with the swirling force by the swirler becomes an airflow having a swirling speed component and conveys the solid fuel ground on the grinding table 12 to the rotary classifier 16 located above in the housing 11. Among the ground solid fuel, those having a particle size larger than a predetermined particle size are classified by the rotary classifier 16 or fall without reaching the rotary classifier 16 and are returned onto the grinding table 12, where they are ground again between the grinding table 12 and the grinding roller 13.

[0020] The grinding roller 13 is a rotating body that grinds the solid fuel supplied onto the grinding table 12 from the fuel supply unit 17. The grinding roller 13 is pressed against the upper surface of the grinding table 12 and cooperates with the grinding table 12 to grind the solid fuel. In FIG. 1, only one grinding roller 13 is shown as a representative, but a plurality of grinding rollers 13 are arranged at regular intervals in the circumferential direction so as to press the upper surface of the grinding table 12. For example, three grinding rollers 13 are arranged at equal intervals in the circumferential direction with an angular interval of 120° on the outer peripheral portion. In this case, the portions (pressing portions) where the three grinding rollers 13 contact the upper surface of the grinding table 12 are equidistant from the rotation center axis of the grinding table 12.

[0021] The grinding roller 13 can swing vertically by means of the journal head 45 and is supported so as to be able to approach and separate from the upper surface of the grinding table 12. When the grinding table 12 rotates with the outer peripheral surface of the grinding roller 13 in contact with the solid fuel on the upper surface of the grinding table 12, the grinding roller 13 receives a rotational force from the grinding table 12 and rotates along with it. When solid fuel is supplied from the fuel supply unit 17, the solid fuel is pressed and ground between the grinding roller 13 and the grinding table 12.

[0022] The support arm 47 of the journal head 45 is supported by a support shaft 48 along the horizontal direction at the middle part, and the grinding roller 13 is supported by the support shaft 48 at the side surface of the housing 11 so as to be able to swing vertically. Further, a pressing device 49 is provided at the upper end portion above the vertical upper side of the support arm 47. The pressing device 49 is fixed to the housing 11 and applies a load to the grinding roller 13 via the support arm 47 and the like so as to press the grinding roller 13 against the grinding table 12.

[0023] The drive unit 14 is a device that transmits a driving force to the grinding table 12 and rotates the grinding table 12 around the central axis. The drive unit 14 is connected to the mill motor 15 and transmits the driving force of the mill motor 15 to the grinding table 12.

[0024] The rotary classifier 16 is provided at the upper part of the housing 11 and has a hollow substantially inverted conical outer shape. The rotary classifier 16 is provided with a plurality of blades 60 extending in the vertical direction at its outer peripheral position. Each blade 60 is provided at a predetermined interval (equal interval) around the central axis C of the rotary classifier 16. The rotary classifier 16 classifies the solid fuel pulverized by the pulverizing table 12 and the pulverizing roller 13 (hereinafter, the pulverized solid fuel is referred to as "pulverized fuel") into those larger than a predetermined particle size (for example, 70 to 100 μm for coal, hereinafter, the pulverized fuel exceeding the predetermined particle size is referred to as "coarse powder fuel") and those equal to or smaller than the predetermined particle size (hereinafter, the pulverized fuel equal to or smaller than the predetermined particle size is referred to as "fine powder fuel"). The rotary classifier 16 that classifies by rotation, also called a rotary separator, is rotationally driven by a classifier motor 18 controlled by a control unit 50, and rotates around the fuel supply unit 17 about a cylindrical shaft 71 (see FIG. 2) extending in the vertical direction of the housing 11. Details of the rotary classifier 16 will be described later. Note that, as the classifier, a fixed classifier including a fixed hollow inverted conical casing and a plurality of fixed swirling blades instead of the blade 60 at the outer peripheral position of the casing may be used.

[0025] The pulverized fuel that reaches the rotary classifier 16 is, due to the relative balance between the centrifugal force generated by the rotation of the blade 60 and the centripetal force by the airflow of the primary air. Coarse powder fuel with a large diameter is knocked off by the blade 60, returned to the pulverizing table 12, pulverized again, and the fine powder fuel is guided to an outlet port 19 in the ceiling portion 42 of the housing 11. The fine powder fuel classified by the rotary classifier 16 is discharged from the outlet port 19 together with the primary air into the fine powder fuel supply flow path 100b and supplied to the burner 220 of the boiler 200. The fine powder fuel supply flow path 100b is also called a fine coal pipe when the solid fuel is coal.

[0026] The fuel supply unit 17 is attached so that its lower end extends along the vertical direction through the ceiling portion 42 of the housing 11 to the inside of the housing 11, and supplies the solid fuel input from the upper part of the fuel supply unit 17 to a substantially central region of the pulverizing table 12. The fuel supply unit 17 is supplied with solid fuel from the coal feeder 20.

[0027] The coal feeder 20 includes a conveying unit 22 and a coal feeder motor 23. The conveying unit 22 is, for example, a belt conveyor, and by the driving force given from the coal feeder motor 23, it conveys the solid fuel discharged from the lower end of the downspout 24 directly below the bunker 21 to above the fuel supply unit 17 of the mill 10 and inputs it into the interior of the fuel supply unit 17. Normally, primary air for conveying pulverized fuel to the burner 220 is supplied inside the mill 10, and the pressure is higher than that of the coal feeder 20 and the bunker 21. In the downspout 24, which is a pipe extending vertically directly below the bunker 21, fuel is held in a stacked state inside, and the stacked solid fuel layer in the downspout 24 ensures a sealing property such that the primary air and pulverized fuel on the mill 10 side do not flow backward to the bunker 21 side. The supply amount of the solid fuel supplied to the mill 10 is adjusted, for example, by the moving speed of the belt conveyor of the conveying unit 22.

[0028] The air supply unit 30 is a device that dries the pulverized fuel and blows primary air for conveying it to the rotary classifier 16 into the interior of the housing 11. In order to appropriately adjust the flow rate and temperature of the primary air blown into the interior of the housing 11, in this embodiment, the air supply unit 30 includes a primary air fan (PAF: Primary Air Fan) 31, a hot gas flow path 30a, a cold gas flow path 30b, a hot gas damper 30c, and a cold gas damper 30d.

[0029] In this embodiment, the hot gas flow path 30a supplies a part of the air (outside air) sent out from the primary air fan 31 as hot gas heated by passing through a heat exchanger 34 such as an air preheater. A hot gas damper 30c is provided on the downstream side of the hot gas flow path 30a. The opening degree of the hot gas damper 30c is controlled by the control unit 50. The flow rate of the hot gas supplied from the hot gas flow path 30a is determined by the opening degree of the hot gas damper 30c.

[0030] The cold gas flow path 30b supplies a part of the air sent out from the primary air blower 31 as cold gas at room temperature. A cold gas damper 30d is provided on the downstream side of the cold gas flow path 30b. The opening degree of the cold gas damper 30d is controlled by the control unit 50. The flow rate of the cold gas supplied from the cold gas flow path 30b is determined by the opening degree of the cold gas damper 30d.

[0031] In this embodiment, the flow rate of the primary air is the total flow rate of the hot gas supplied from the hot gas flow path 30a and the cold gas supplied from the cold gas flow path 30b. The temperature of the primary air is determined by the mixing ratio of the hot gas supplied from the hot gas flow path 30a and the cold gas supplied from the cold gas flow path 30b, and is controlled by the control unit 50. Further, a part of the combustion gas discharged from the boiler 200 may be introduced into the hot gas supplied from the hot gas flow path 30a through a gas recirculation blower (not shown) and mixed, so as to adjust the oxygen concentration of the primary air blown from the primary air flow path 100a into the interior of the housing 11.

[0032] In this embodiment, the state detection unit 40 of the mill 10 transmits the measured or detected data to the control unit 50. The state detection unit 40 of this embodiment is, for example, differential pressure measurement means, and measures the differential pressure between the pressure at the portion where the primary air flows into the interior of the housing 11 from the primary air flow path 100a and the pressure at the outlet port 19 where the primary air and the pulverized fuel are discharged from the interior of the housing 11 to the pulverized fuel supply flow path 100b as the differential pressure of the mill 10. The increase or decrease of the differential pressure of this mill 10 corresponds to the increase or decrease of the circulation amount of the pulverized fuel circulating between the vicinity of the rotary classifier 16 and the vicinity of the grinding table 12 inside the housing 11 due to the classification effect of the rotary classifier 16. That is, by adjusting the rotation speed of the rotary classifier 16 according to the differential pressure of this mill 10, the amount of pulverized fuel discharged from the outlet port 19 can be adjusted with respect to the supply amount of the solid fuel supplied to the mill 10. Therefore, within the range where the particle size of the pulverized fuel does not affect the combustibility of the burner 220, a corresponding amount of pulverized fuel can be stably supplied to the burner 220 provided in the boiler 200 with respect to the supply amount of the solid fuel to the mill 10. Further, the state detection unit 40 of the present embodiment is, for example, a temperature measurement means, which detects the temperature of the primary air supplied into the housing 11 (the temperature of the primary air at the mill inlet) and the temperature of the primary air from the space above the grinding table 12 inside the housing 11 to the outlet port 19, and controls the blower unit 30 so as not to exceed the upper limit temperature. The upper limit temperature is determined in consideration of the possibility of ignition of the solid fuel and the like. The primary air is cooled by transporting while drying the pulverized fuel inside the housing 11, and the temperature of the primary air at the outlet port 19 is, for example, about 60 to 90 degrees.

[0033] The control unit 50 is a device that controls each part of the solid fuel pulverizing apparatus 100. The control unit 50 may, for example, transmit a drive instruction to the mill motor 15 to control the rotation speed of the grinding table 12. The control unit 50 may, for example, transmit a drive instruction to the classifier motor 18 to control the rotation speed of the rotary classifier 16 to adjust the classification performance, and optimize the differential pressure of the mill 10, that is, the circulation amount of the pulverized fuel inside the mill 10 within a predetermined range, so that the fine pulverized fuel can be stably supplied to the burner 220. The classification performance is the performance required for classification such as the classification characteristics, passing characteristics, and classification accuracy described later. Further, the control unit 50 can adjust the supply amount (coal feeding amount) of the solid fuel that the conveying unit 22 conveys and supplies to the fuel supply unit 17 by, for example, transmitting a drive instruction to the coal feeder motor 23 of the coal feeder 20. Further, the control unit 50 can control the opening degrees of the hot gas damper 30c and the cold gas damper 30d by transmitting an opening degree instruction to the blower unit 30 to adjust the flow rate and temperature of the primary air. Specifically, the control unit 50 controls the opening degrees of the hot gas damper 30c and the cold gas damper 30d so that the flow rate of the primary air supplied into the housing 11 and the temperature of the primary air at the outlet port 19 become predetermined values set corresponding to the coal feeding amount for each type of solid fuel.

[0034] The control unit 50 is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. And a series of processes for realizing various functions are stored in a storage medium or the like in the form of a program as an example. The CPU reads this program into the RAM or the like and executes information processing and arithmetic processing, thereby realizing various functions. Note that the program may be in a form pre-installed in the ROM or other storage media, in a form provided in a state stored in a computer-readable storage medium, in a form distributed via wired or wireless communication means, or the like. A computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Also, the HDD may be replaced with a solid state disk (SSD) or the like.

[0035] Next, a boiler 200 that generates steam by burning using the fine powder fuel supplied from the solid fuel pulverizer 100 will be described. The boiler 200 includes a furnace 210 and a burner 220.

[0036] The burner 220 is a device that forms a flame by burning the fine powder fuel using primary air containing the fine powder fuel supplied from the fine powder fuel supply passage 100b and secondary air supplied by heating the air (outside air) sent from the forced draft fan (FDF) 32 with the heat exchanger 34. The combustion of the fine powder fuel is performed in the furnace 210, and the high-temperature combustion gas is discharged to the outside of the boiler 200 after passing through heat exchangers (not shown) such as an evaporator, a superheater, and a economizer.

[0037] The combustion gas discharged from the boiler 200 flows through the flue 36. The combustion gas flowing through the flue 36 is subjected to denitrification treatment in the denitrification device 35. The denitrification device 35 supplies a reducing agent having the function of reducing nitrogen oxides such as ammonia and aqueous urea into the flow path through which the combustion gas flows, and promotes the reaction between the nitrogen oxides in the combustion gas supplied with the reducing agent and the reducing agent by the catalytic action of the denitrification catalyst installed in the denitrification device 35, thereby removing and reducing the nitrogen oxides in the combustion gas. The combustion gas subjected to the denitrification treatment undergoes heat exchange with the air sent from the primary air blower 31 and the air sent from the forced draft blower 32 in a heat exchanger 34 such as an air preheater, and is subjected to predetermined treatment in an environmental device (an electrostatic precipitator, a desulfurization device, etc., not shown) via an induced draft fan (IDF), and is led to a chimney (not shown) and discharged to the outside air. The air sent from the primary air blower 31 heated by the combustion gas in the heat exchanger 34 is supplied to the hot gas flow path 30a described above. The water supply to each heat exchanger of the boiler 200 is heated in a economizer (not shown), and then further heated by an evaporator (not shown) and a superheater (not shown) to generate high-temperature and high-pressure steam, which is sent to a steam turbine (not shown) that is a power generation unit to rotationally drive the steam turbine, and rotationally drive a generator (not shown) connected to the steam turbine to generate electricity, thus constituting the power generation plant 1.

[0038] Next, the details of the rotary classifier 16 will be described. In the following description, the "circumferential direction" and the "radial direction" mean the "circumferential direction" and the "radial direction" centered on the central axis C.

[0039] As shown in FIG. 1, the rotary classifier 16 is provided at the upper part of the housing 11. As shown in FIG. 2, the rotary classifier 16 rotates about a central axis C extending in the vertical direction. In the present embodiment, the rotary classifier 16 rotates clockwise when viewed in plan view, as indicated by the arrow A1 in FIGS. 2 and 3. The rotation direction of the rotary classifier 16 is opposite to the swirling direction of the primary air formed by the swirling blades installed at the air outlet. The rotary classifier 16 is rotationally driven by a motor (not shown). The rotation speed of the motor is controlled by the control unit 50.

[0040] As shown in FIG. 2, the rotary classifier 16 has a main body portion 70 having an outer shape of a hollow substantially inverted conical shape. An inner space S1 is formed inside the main body portion 70. The main body portion 70 integrally has a cylindrical shaft 71 that covers the fuel supply portion 17 and extends along the central axis C, an upper end portion 72 that extends radially from the upper end of the cylindrical shaft 71, and a lower end portion 73 that extends radially from the lower end of the cylindrical shaft 71. The upper end portion 72 partitions the upper end of the inner space S1. Also, the lower end portion 73 partitions the lower end of the inner space S1.

[0041] Further, the rotary classifier 16 includes a plurality of blades 60 provided at the outer peripheral position of the main body portion 70. Each blade 60 extends in the vertical direction. Each blade 60 is a plate-like member. The upper end of each blade 60 is fixed to the upper end portion 72. Also, the lower end of each blade 60 is fixed to the lower end portion 73. Each blade 60 is inclined such that the lower end side approaches the central axis C more than the upper end side. An opening 72a to which the outlet port 19 (see FIG. 1) is connected is formed in the upper end portion 72.

[0042] As shown in Fig. 3, the plurality of blades 60 are provided in parallel at a predetermined interval (equal interval) around the central axis C of the rotary classifier 16. Specifically, each blade 60 is arranged at a predetermined interval on a virtual circle V centered on the central axis C. Further, each blade 60 is arranged so as to be inclined at a predetermined angle with respect to the radial direction when viewed in plan. Further, a gap is formed between adjacent blades 60 in the circumferential direction. The gap communicates the inner space S1 of the plurality of blades 60 with the outer space S2 outside the blades 60. Pulverized fuel is guided to each blade 60 together with the primary air flowing from the outside to the inside in the radial direction.

[0043] Each blade 60 has a collision surface 61 which is the front surface in the rotation direction and a back surface 65 which is the rear surface in the rotation direction. As shown in Fig. 3, pulverized fuel containing fine powder fuel B2 and coarse powder fuel B1 collides with the collision surface 61. An outward force in the radial direction (centrifugal force and collision force, hereinafter referred to as the outward force) indicated by arrow A2 and an inward force in the radial direction (centripetal force due to the flow of the primary air, hereinafter referred to as the inward force) indicated by arrow A3 act on the pulverized fuel that has collided with the collision surface 61. Since the coarse powder fuel B1 has a large weight, the outward force A2 acts strongly on the coarse powder fuel B1 that has collided with the collision surface 61 due to the influence of the centrifugal force. As a result, the coarse powder fuel B1 is repelled toward the outside of the blade 60 (the outer space S2 side) as shown by arrow A4 against the inward force A3. On the other hand, since the fine powder fuel B2 has a small weight, the centrifugal force acting on the fine powder fuel B2 that has collided with the collision surface 61 is relatively weak. As a result, the force acting on the fine powder fuel B2 is dominated by the inward force indicated by arrow A3, so the fine powder fuel B2 is guided to the inside of the blade 60 (the inner space S1 side) as shown by arrow A5. The rotary classifier 16 classifies the coarse powder fuel B1 and the fine powder fuel B2 based on such a principle.

[0044] [Cross-sectional shape of the blade] Next, regarding the shape of each blade 60, the vertical cross-sectional shape (the cross-sectional shape when cut by a plane (horizontal plane) orthogonal to the vertical direction) will be described. In the following description, when simply referring to the "cross-sectional shape", it means the cross-section (airfoil cross-section) when the blade is cut by a horizontal plane. Each blade 60 has a uniform shape along the vertical direction. That is, the cross-sectional shape of each blade 60 is the same at any position in the vertical direction.

[0045] As shown in FIG. 4, each blade 60 has, as described above, a collision surface 61 and a back surface 65 which is the surface on the opposite side of the collision surface 61. The back surface 65 is a flat surface.

[0046] The collision surface 61 has a curved surface 62 disposed on the outer side in the radial direction and a flat surface 63 disposed more radially inward than the curved surface 62. The curved surface 62 and the flat surface 63 are smoothly connected at a boundary point D. The boundary point D is provided substantially at the center in the radial direction of the collision surface 61.

[0047] The curved surface 62 is provided on the outer side in the radial direction from the boundary point D. The curved surface 62 is curved so as to protrude forward in the rotation direction (see arrow A1 in FIG. 3). The curved surface 62 is curved such that the plate thickness becomes thinner toward the outer side in the radial direction from the boundary point D. Specifically, the curved surface 62 is curved such that the plate thickness becomes zero at the outer end in the radial direction of the blade 60. That is, at the outer end in the radial direction of the blade 60, the curved surface 62 and the back surface 65 are connected. By configuring in this way, the outer end in the radial direction of the blade 60 becomes an acute angle. Therefore, the outer end in the radial direction of the blade 60 may be covered with a cover or the like to take measures for preventing incisions.

[0048] Further, on the curved surface 62, the angle (hereinafter referred to as "tilt angle θ") formed by the tangent line L1 of the virtual circle V and the perpendicular line L2 to the collision surface 61 is larger on the radially outer side than on the radially inner side. That is, as shown in FIG. 4, the curved surface 62 is curved such that the tilt angle θ3 at the point P3, which is radially outside the point P2, is larger than the tilt angle θ2 at the point P2. Note that the curved surface shape of the curved surface 62 is determined by the required classification characteristics. For example, as described in this embodiment, the curved surface shape of the curved surface 62 is preferably such that the connection portion with the flat surface 63 has the largest radius of curvature, and the radius of curvature decreases as it moves away from the flat surface 63 (towards the radially outer side). However, the curved surface 62 may have a constant curvature. Also, for example, it may have an arc shape, a part of an ellipse shape, or a parabola shape. Note that the classification characteristic is an index indicating the difficulty for the pulverized fuel to pass through (being repelled to the outer peripheral side of the blade 60), and is a value that increases as it becomes more difficult to pass through.

[0049] The flat surface 63 is inclined at a predetermined angle with respect to the radial direction. Also, the tilt angle θ1 of the flat surface 63 is smaller than the tilt angle of the curved surface 62 (for example, tilt angle θ2 or tilt angle θ3).

[0050] Note that the virtual circle V is a virtual circle centered on the central axis C and is also the rotation locus of any point within the blade cross-section of the blade 60.

[0051] [Blade processing method] Next, the processing method of the blade 60 will be described. The processing method of the blade 60 is not particularly limited. For example, a blade 60 having a curved surface portion on the collision surface 61 may be processed by cutting a flat plate-shaped material. Also, by appropriately selecting the material and hardness of the flat blade in consideration of the difference in wear rate depending on the blade part, a curved surface part may be formed on the collision surface of the blade due to wear associated with the use of the rotary classifier 16. That is, assuming that the contact frequency with the pulverized particles is higher and the wear rate is larger toward the outer periphery in the radial direction of the blade, for example, if the surface hardness of the collision surface of the flat blade is made uniform, the reduction in plate thickness due to wear becomes larger toward the outer periphery in the radial direction, and a curved surface part will be formed with use. Further, it is preferable to appropriately select the material and hardness of the blade 60 so that the curved surface part is maintained due to the wear of the blade 60 associated with the use of the rotary classifier 16. By doing so, the maintenance frequency of the blade 60 can be reduced.

[0052] [Classification performance] Next, the classification performance of the rotary classifier will be described. First, the classification performance of the rotary classifier 16 equipped with the flat blade 60X according to the comparative example will be described with reference to FIGS. 15 to 21. The flat blade 60X is inclined at a predetermined angle with respect to the radial direction when viewed in the horizontal cross section.

[0053] First, the passing characteristics of the flat blade 60X at each position in the radial direction of the blade 60X shown by G4 in FIG. 17 are obtained. The passing characteristics are an index indicating the ease of passing of the pulverized fuel through the classifier (the larger the value, the easier it is to pass through the inner peripheral side of the blade 60), and the details will be described later. Figure 17 shows the relationship between each position in the radial direction of blade 60X (horizontal axis), the outward force acting on the pulverized fuel (left vertical axis), and the passing characteristics of the pulverized fuel (right vertical axis). The horizontal axis of the graph in Figure 17 indicates the distance from the inlet (outer end in the radial direction) of blade 60X. That is, the horizontal axis indicates the radial position of blade 60X, with the left end of the horizontal axis indicating the outer end in the radial direction of blade 60X (the outer end on the side of outer space S2 of blade 60X), and the right end indicating the inner end in the radial direction of blade 60X (the outer end on the side of inner space S1 of blade 60X). Also, the outward force acting on the pulverized fuel includes the force due to centrifugal force and the force due to collision. The passing characteristics are positively correlated with the inward force acting on the pulverized fuel, that is, they are negatively correlated with the outward force (centrifugal force + collision force).

[0054] In Figure 17, G1 indicates the outward force F3 (see Figure 16) acting on the pulverized fuel when the pulverized fuel collides with blade 60X. Also, G2 indicates the outward force F5 (see Figure 16) acting on the pulverized fuel due to the centrifugal force acting on the pulverized fuel. The outward force F3 acting on the pulverized fuel due to the collision and the outward force F5 due to the centrifugal force acting on the pulverized fuel are obtained as follows.

[0055] As shown in Figure 15, when pulverized fuel containing fine powder fuel B2 and coarse powder fuel B1 collides with the flat blade 60X, the coarse powder fuel B1 is bounced to the outside of blade 60X (to the side of outer space S2) as shown by arrow A6. On the other hand, the fine powder fuel B2 is bounced to the inside of blade 60X (to the side of inner space S1) as shown by arrow A7.

[0056] As shown in Figure 16, the force with which the pulverized fuel collides with the rotating blade 60X is indicated by arrow F1. The force indicated by this arrow F1 is decomposed into a force (arrow F2) acting perpendicular to the collision surface of blade 60X and a force (arrow F3) acting parallel along the collision surface of blade 60X. The force acting in the vertical direction is canceled out by the vertical resistance force (arrow F4) from blade 60X. Since no canceling force acts on the force acting in parallel, an outward force F3 of blade 60X acts on the collided pulverized fuel. That is, an outward force F3 due to the collision acts. In addition, in FIG. 16, arrow F5 indicates the radially outward force along the collision surface of blade 60X due to the centrifugal force, and arrow F6 indicates the radially inward force along the collision surface of blade 60X due to the flow of the primary air. The outward force F3 is obtained by the following formula (1).

[0057] [Equation 1] F3 = F1 × sin θ ··· (1) However, F1: the force with which the pulverized fuel collides with the rotating blade 60X θ: the angle formed by the direction in which the force with which the pulverized fuel collides with the rotating blade 60X acts (see arrow F1) and the direction of the force acting in the vertical direction (see arrow F2) In addition, under the actual machine operating conditions, the frictional force generated between the pulverized fuel and the blade 60X is small compared to other forces, and thus is ignored in the calculation.

[0058] Thus, the greater the inclination of the blade 60X with respect to the radial direction, the greater the outward force F5 of the blade 60X acts. Also, the blade 60X is flat. For this reason, in the blade 60X, the angle θ is constant at any point in the radial direction. Therefore, as shown by G1 in FIG. 17, in the blade 60X, the outward force F5 is constant at any point in the radial direction.

[0059] Also, the pulverized fuel that has collided with the blade 60X is given a centrifugal force F5 by the blade 60X. The centrifugal force F5 is obtained from the following formula (2).

[0060] [Equation 2] F5 = m × r × ω 2 ··· (2) However, m: the mass of the pulverized fuel r: the radius of rotation of the collision position ω: the angular velocity of the blade 60X

[0061] Therefore, the centrifugal force F5 acting on the pulverized fuel that has collided with the blade 60X at the same rotational speed is determined by the mass of the pulverized fuel and the radius of rotation of the collision position. In addition, the fine powder fuel B2 has a small mass. Also, as will be described later, since the fine powder fuel B2 collides with the inner side in the radial direction of the blade 60X, that is, at a location with a small rotational radius, the centrifugal force F5 acting on the fine powder fuel B2 becomes small. Therefore, when the inward radial force F7 due to the flow of the primary air overcomes the centrifugal force F5, the fine powder fuel B2 moves toward the inner side in the radial direction of the blade 60X. On the other hand, the coarse powder fuel B1 has a large mass. Also, as will be described later, since the coarse powder fuel B1 collides with the outer side in the radial direction of the blade 60X, that is, at a location with a large rotational radius, the centrifugal force F5 acting on the coarse powder fuel B1 becomes large. Therefore, when the centrifugal force F5 overcomes the inward radial force F6 due to the flow of the primary air, the coarse powder fuel B1 will be bounced to the outer side in the radial direction of the blade 60X. From the above, as shown by G2 in FIG. 17, since the force due to the centrifugal force F5 is a linear function, it becomes a downward-sloping straight line.

[0062] Also, G3 in FIG. 17 shows the outward force resulting from the sum of the outward centrifugal force F5 and the outward force F3 due to the collision. As described above, if the blade 60X is flat, the outward force F3 due to the collision is constant. Therefore, as shown by G3 in FIG. 17, the outward force (centrifugal force + collision force) becomes a downward-sloping straight line.

[0063] The passing characteristic shown by G4 in FIG. 17 is in an inverse proportional relationship (negative correlation) with the outward force (centrifugal force + collision force). Therefore, as shown by G4, the passing characteristic becomes an upward-sloping straight line with an inclination opposite to that of G3 showing the outward force (centrifugal force + collision force). In this way, the passing characteristic of the flat blade 60X is obtained.

[0064] Here, the passing characteristics shown in FIG. 17 indicate the mass of a single pulverized fuel that can pass through. If the density of the pulverized fuel is constant, this indicates the volume of the pulverized fuel, i.e., the size of the pulverized fuel. Therefore, as shown by G5a in FIG. 18A, the passing characteristics and the size of the pulverized fuel passing through are in a proportional relationship (positive correlation). Also, as shown by G4 in FIG. 17, the passing characteristics are proportional to the distance from the outer end side of the blade 60X. From this, as shown by G5b in FIG. 18B, the size of the pulverized fuel passing through is also proportional to the distance from the outer end side of the blade 60X. FIG. 18A is a graph showing the relationship between the size of the pulverized fuel passing through the blade 60X and the passing characteristics. FIG. 18B is a graph showing the relationship between the size of the pulverized fuel passing through the blade 60X and the distance from the inlet of the blade 60X.

[0065] Next, the classification effect by the flow of the primary air will be described with reference to FIGS. 19 and 20. First, the pulverized fuel is pulverized on the pulverizing table 12 of the mill 10 and is pneumatically conveyed to the rotary classifier 16 by the primary air (conveying gas) blown out from the periphery of the pulverizing table 12. As described above, at this time, the air flow E (the flow of the primary air) is a flow that rises while swirling inside the housing 11, and as shown in FIG. 19, it reaches the rotary classifier 16 from the outer peripheral side of the blade in the reverse rotation direction with respect to the rotation direction A1 of the blade 60X.

[0066] The airflow E that has reached the side surface of the blade 60X sharply changes its course toward the flow path between the adjacent blades 60X as shown in Fig. 19. At this time, the fine powder fuel B2, which is light in mass and has little inertia, easily changes its course along with the airflow E. On the other hand, the coarse powder fuel B1, which is heavy in mass and has large inertia, hardly changes its course. Due to this characteristic, as shown in Fig. 19, the fine powder fuel B2 passes through the inner peripheral side of the curve of the airflow, and the coarse powder fuel B1 passes through the outer peripheral side of the curve of the airflow, thereby roughly classifying the airflow. As a result of the rough classification, the fine powder fuel B2 has a higher probability of colliding with the outlet side (inner side in the radial direction) of the blade 60X, and the coarse powder fuel B1 has a higher probability of colliding with the inlet side (outer side in the radial direction) of the blade 60X. The distribution of the pulverized fuel at this time generally depends on the inertial force of the pulverized fuel. That is, according to the relationship F (force) = m (mass) · a (acceleration), when receiving the same fluid force from the airflow of the primary air, a lighter particle (fine powder fuel B2) generates a larger acceleration. Also, the moving distance of an object given a constant acceleration is X = a (acceleration) · t (time) 2 Therefore, the distribution of the particles colliding with the blade 60X generally becomes a curve-like distribution close to a quadratic function as shown in Fig. 20. Fig. 20 is a graph showing the relationship between the particle size of the pulverized fuel colliding with the blade 60X and the distance from the inlet of the blade 60X. However, since the starting point at which the pulverized fuel starts to change its direction toward the blade 60X depends on the flight trajectory of the particles, due to this variation, the distribution characteristics become a broad distribution with a certain width. Thus, the size of the particles of the pulverized fuel colliding with each position in the radial direction of the blade 60X (hereinafter referred to as "collision particle size distribution") is within the range indicated by the hatching in Fig. 20. In the above description, the case of colliding with the flat blade 60X has been described, but the size of the particles of the pulverized fuel colliding with the blade does not change depending on the shape of the blade. Therefore, for example, even in the case of colliding with the blade 60 provided with the curved surface 62 described in the present embodiment, the collision particle size distribution is the distribution shown in Fig. 20.

[0067] Next, the passage characteristics of the entire rotary classifier 16 equipped with the flat blade 60X (i.e., the classification performance of the rotary classifier 16) will be described with reference to FIG. 21. In the graph of FIG. 21, the left vertical axis indicates the particle size of the pulverized fuel that collides with the blade 60X, and the right vertical axis indicates the particle size of the pulverized fuel that passes through the blade 60X. The horizontal axis indicates the distance from the inlet (outer end) of the blade 60X. The passage characteristics of the entire rotary classifier 16 in this description are derived from the size of the pulverized fuel passing through the blade 60X shown by G5b in FIG. 18B and the pulverized fuel distribution shown in FIG. 20. In FIG. 21, the particle size of the pulverized fuel at the intersection of G5b indicating the size of the pulverized fuel passing through the blade 60X and the upper edge line of the collision particle size distribution is defined as the target particle size of the rotary classifier 16. The target particle size is the upper limit value of the particle size of the pulverized fuel that is desired to pass through the rotary classifier 16 and be discharged from the mill 10 (supplied to the burner 220 of the boiler 200).

[0068] In FIG. 21, the region below the upper edge line of the collision particle size distribution and G5b indicating the size of the pulverized fuel passing through the blade 60X is the region of the pulverized fuel passing through the rotary classifier 16. That is, the region below the dashed line G6 is the region of the pulverized fuel passing through the rotary classifier 16. The passage characteristics on the blade inlet side (outer end side) with a large amount of coarse pulverized fuel are relatively low (i.e., difficult to pass), and conversely, the passage characteristics on the blade outlet side (inner end side) with a large amount of fine pulverized fuel are relatively high (i.e., easy to pass). Thus, coarse pulverized fuel can be prevented from passing through, and fine pulverized fuel can be made to pass through. Therefore, the classification effect can be obtained efficiently.

[0069] Next, the classification performance of the rotary classifier 16 provided with the folded plate-shaped blade 60Y according to the comparative example will be described with reference to FIGS. 22 to 24. As shown in FIG. 22, the folded plate-shaped blade 60Y has a plate-shaped outer portion 60Ya and a plate-shaped inner portion 60Yb connected to form an angular fold point H. The blade 60Y has different inclination angles with respect to the radial direction between the outer portion 60Ya and the inner portion 60Yb. Also, the inclination angle of the outer portion 60Ya of the blade 60Y is larger than that of the inner portion 60Yb. In this description, an example in which the inclination angle of the inner portion 60Yb is the same as the inclination angle of the blade 60X described above will be described.

[0070] As shown in FIG. 22, even when the pulverized fuel containing the fine powder fuel B2 and the coarse powder fuel B1 collides with the folded plate-shaped blade 60Y, the coarse powder fuel B1 is repelled toward the outside of the blade 60Y (toward the outside space S2 side) as indicated by the arrow A8. On the other hand, the fine powder fuel B2 is repelled toward the inside of the blade 60Y (toward the inside space S1 side) as indicated by the arrow A9.

[0071] The blade 60Y has different inclination angles with respect to the radial direction between the outer portion 60Ya and the inner portion 60Yb. This means that the directions of the collision forces of the pulverized fuel colliding with the blade 60Y are different. Therefore, the outward force acting on the pulverized fuel that has collided with the inner portion 60Yb having a small inclination angle (the force calculated by the above formula (1); see F3 in FIG. 16) is small, and the outward force acting on the particles that have collided with the outer portion 60Ya having a large inclination angle is large.

[0072] Therefore, as shown by G7 in Fig. 23, in the outer portion 60Ya of the blade 60Y, the outward force due to the collision force becomes large, and in the inner portion 60Yb, the outward force due to the collision force becomes small. Note that G2 in Fig. 23 indicates the outward force due to the centrifugal force acting on the pulverized fuel, similar to Fig. 17. Also, G8 indicates the outward force due to the sum of the outward force due to the centrifugal force and the outward force due to the collision force. As shown by G7, since the outward force due to the collision force changes greatly at the inflection point H, G8 also changes greatly at the inflection point H. In the following description, the portion where the outward force changes greatly is referred to as the "stepped portion". Also, the passing characteristic shown by G9 in Fig. 23 is in an inverse proportional relationship (negative correlation) with the outward force (centrifugal force + collision force). Also, K1 of the hatching in Fig. 23 indicates the region where the passing characteristic can be reduced compared to the flat blade 60X. Thus, it can be seen that in the outer portion 60Ya where the coarse powder fuel B1 is likely to collide, the passing characteristic (the force toward the inside) can be reduced, so that the situation where the coarse powder fuel B1 passes through can be suppressed more than in the case of the flat blade 60X.

[0073] Next, with reference to Fig. 24, the passing characteristic of the entire rotary classifier 16 provided with the folded blade 60Y (that is, the classification performance of the rotary classifier 16) will be described. The passing characteristic of the entire rotary classifier 16 in this description is derived from G10 indicating the size of the pulverized fuel passing through the blade 60Y based on G9 in Fig. 23 and the collision particle size distribution shown in Fig. 20.

[0074] In Fig. 24, the region below the dashed line G11 is the region of the pulverized fuel passing through the rotary classifier 16. As shown by the hatching K2, the passing characteristic in the outer portion 60Ya becomes smaller compared to the case where the flat blade 60X is employed. Also, the passing characteristic in the region with a large particle size, particularly in the region where the ratio of particles below the target particle size is very small, becomes extremely small. Thereby, the passage of the coarse powder fuel can be suppressed, and the classification performance can be improved. On the other hand, for the region of the hatching K3, even though it is within the range of the collision particle size distribution and below the target particle size, it will be bounced to the outer peripheral side by the blade 60Y. Therefore, it can be seen that the classification performance is deteriorated compared with the case where the flat blade 60X is adopted (the fine powder fuel that should pass through and does not need to be classified is bounced to the outer peripheral side). In addition, the classification characteristics have a stepped portion, and whether the pulverized fuel in the particle size range J corresponding to the stepped portion passes through the blade 60Y or not depends on the collision position. For this reason, whether it is classified or not becomes random with respect to the particle size. Therefore, there is a problem that a part of the fine powder fuel that should pass through the rotary classifier 16 is bounced by the blade 60Y, resulting in a deterioration of the classification performance. The bounced fine powder fuel is refluxed to the pulverizing table 12 and re-pulverized. In order to further pulverize the already fine fine powder fuel, there is a waste of pulverizing power. In addition, there is a problem that the slip vibration generated by the fact that the refluxed fine powder fuel acts as a solid lubricant and the pulverizing roller 13 slips on the pulverizing table 12 is likely to occur in the mill 10.

[0075] Next, the classification performance of the rotary classifier 16 provided with the blade 60 having the curved surface 62 according to the present embodiment will be described with reference to FIGS. 5 and 6. In this description, an example in which the inclination angle of the flat surface 63 is the same as the inclination angle of the blade 60X described above will be described. In the curved surface 62, it can be regarded that the inclination angle changes continuously. Therefore, as shown by G20 in FIG. 5, the outward force due to the collision force also changes smoothly. Specifically, in the curved surface 62, the inclination angle is larger on the outer side in the radial direction than on the inner side in the radial direction. Therefore, as going toward the outer side in the radial direction, the outward force due to the collision force increases. Also, G21 indicating the outward force due to the sum of the outward force due to the centrifugal force and the outward force due to the collision force also changes smoothly so that the outward force increases as going toward the outer side in the radial direction. Note that G2 in FIG. 5 indicates the outward force due to the centrifugal force acting on the pulverized fuel, similar to FIG. 17 and the like. Further, the passing characteristics indicated by G22 in FIG. 5 are in an inverse proportion relationship (negative correlation relationship) with the outward force (centrifugal force + collision force). Therefore, similar to G21, G22 also changes smoothly. Also, K4 with hatching in FIG. 5 indicates a region where the passing characteristics can be reduced compared to the flat blade 60X. Thus, it can be understood that in the outer side in the radial direction where the coarse powder fuel B1 is likely to collide, the passing characteristics (force toward the inner side) can be reduced, so that the situation where the coarse powder fuel B1 passes through can be suppressed compared to the flat blade 60X.

[0076] Next, with reference to FIG. 6, the passing characteristics of the entire rotary classifier 16 provided with the blade 60 according to the present embodiment (that is, the classification performance of the rotary classifier 16) will be described. The passing characteristics of the entire rotary classifier 16 in this description are derived from G23 indicating the size of the pulverized fuel passing through the blade 60 based on G22 in FIG. 5 and the collision particle size distribution shown in FIG. 20.

[0077] In FIG. 6, the region below the dashed line G24 is the region of the pulverized fuel passing through the rotary classifier 16. As shown by the hatchings K5 and K6, the passing characteristics are reduced on the curved surface 62 as compared with the case where the flat blade 60X is employed. Further, as shown by the hatching K6, the passing characteristics are reduced on the curved surface 62 as compared with the case where the folded plate blade 60Y is employed. Further, the passing characteristics are extremely reduced in the region where the particle size is large, particularly in the region where the proportion of particles below the target particle size is very small. Thereby, the passage of the coarse powder fuel can be further suppressed, and the classification performance can be improved. Thus, by suppressing the passage of the coarse powder fuel, it is possible to suppress the supply of the coarse powder fuel having a particle size equal to or larger than the target particle size to the burner 220. Thereby, the amount of the pulverized fuel (unburned pulverized fuel) that cannot be completely burned in the burner 220 can be reduced, and the unburned content in the ash discharged from the boiler 200 can be reduced. Further, since the unburned content in the ash can be reduced, it becomes possible to reduce the amount of air supplied to the boiler 200 (low air ratio combustion), and the amount of nitrogen oxides generated can also be suppressed. Therefore, the environmental load can be reduced. Further, the amount of the reducing agent (such as ammonia) used in the denitration device 35 can also be reduced, and the running cost can be reduced.

[0078] On the other hand, regarding the region of the hatching K7, although it is within the collision particle size distribution range and below the target particle size, it will be bounced to the outer peripheral side by the blade 60Y. The region where this classification performance deteriorates can be made smaller as compared with the case where the folded plate blade 60Y is employed (see the hatching K3 in FIG. 24). Therefore, the deterioration of the classification performance can be suppressed. Thus, by suppressing the recirculation of the fine powder fuel B2, the re-pulverization of the fine powder fuel B2 can be suppressed. Thereby, the pulverization power of the mill 10 can be reduced. Further, it is possible to make it difficult to cause the slip vibration of the mill 10 caused by the refluxed fine powder fuel serving as a lubricant.

[0079] In addition, by adopting a structure that changes the inclination angle with the curved surface 62, the stepped portion that occurred when the blade 60Y in the shape of a folded plate was adopted is eliminated. As a result, it is possible to eliminate the region where whether or not it is classified is random with respect to the particle size, so that the classification performance can be improved.

[0080] In the present embodiment, in addition to the improvement in the classification performance described above, the following operational effects are achieved. In the present embodiment, the curved surface 62 is formed on the outer side in the radial direction of the blade 60. In such a blade 60 of the tip curved surface type, even if the blade 60 is worn due to the collision with the pulverized fuel as the rotary classifier 16 is used, the curved surface shape thereof is generally maintained. That is, the blade 60 of the tip curved surface type can have self-shaping properties such that it wears so that the length in the radial direction of the blade 60 decreases. This is because the outer side of the blade 60 is rougher and the wear is promoted by the large amount and high speed collision of heavy particles. By appropriately manufacturing the material and hardness of the blade 60, the curved surface shape of the curved surface 62 of the blade 60 can be maintained over a long period of time and its performance can be sustained.

[0081] In addition, in the present embodiment, the collision surface 61 has the curved surface 62 and the flat surface 63. Since the flat surface 63 is easier to manufacture than the curved surface 62, the blade 60 can be easily manufactured as compared with the case where the entire surface of the collision surface 61 is the curved surface 62. In general, the influence of the force of the primary air (that is, the force from the outer side to the inner side in the radial direction of the blade 60) becomes larger toward the inner side in the radial direction of the collision surface 61, so the influence of the outward force due to the collision force of the pulverized fuel becomes smaller. In the present embodiment, the flat surface 63 is formed on the inner side in this radial direction. Thereby, it is possible to suppress a decrease in the classification performance as compared with the case where the flat surface 63 is formed on the outer side in the radial direction. Note that the boundary point D, which is the boundary between the curved surface 62 and the flat surface 63, may be radially inside the point L where G23 indicating the size of the pulverized fuel passing through the blade 60 in FIG. 6 intersects the upper edge line of the collision particle size distribution. By configuring in this way, the entire surface of the flat surface 63 can be made into a region where the influence of the outward force due to the collision force is small, so that the decrease in the classification performance due to the formation of the flat surface 63 can be further suppressed.

[0082] Also, in the present embodiment, the circumferential length (length in the plate thickness direction) of the blade 60 becomes shorter as it goes radially outward. Thereby, the plate thickness of the blade 60 can be made thinner, so that it is difficult for tools or the like to interfere with adjacent blades or the like when the blade 60 is attached. Therefore, the attachment work of the blade 60 can be facilitated.

[0083] Note that the present disclosure is not limited to the above-described embodiment, and can be appropriately modified without departing from the gist thereof. For example, in the above-described embodiment, the mill of the present disclosure is used, but as the solid fuel, it may be biomass fuel or PC (Petroleum Coke) fuel generated during petroleum refining, and these fuels may be used in combination.

[0084] Also, in the above-described embodiment, an example in which the classifier of the present disclosure is applied to a mill for pulverizing solid fuel has been described, but the present disclosure is not limited thereto. For example, the classifier of the present disclosure may be applied to a pulverizer for pulverizing ore.

[0085] Also, as the blade 60 wears, the radial length of the blade 60 decreases. For this reason, it is desirable to provide a replacement criterion based on the radial length. Along with this, a detection means for detecting the radial length may be provided on the blade 60, and this detection means may be used as a wear detection sensor.

[0086] The blade 60 is preferably detachably fixed to the main body 70 with bolts or the like so that it can be replaced when worn. However, when the blade 60 is made of a material with sufficient wear resistance, it may be fixed by welding or the like. The mounting surface and the bolt seat surface attached to the main body 70 are preferably provided on the flat surface 63 of the blade 60, but the mounting surface or the like may be provided on the curved surface 62. When providing the mounting surface or the like on the curved surface 62, a counterbore or the like may be provided, or a washer or the like that matches the curvature may be used to form the seat surface.

[0087] [Modification Example of Blade] Further, the present disclosure is not limited to the shape of the blade 60 described above. Hereinafter, modification examples of the blade 60 will be described with reference to the drawings.

[0088] [Modification Example 1] As shown in FIG. 7, the blade may be manufactured by laminating a plurality of thin plate materials in the plate thickness direction. The blade 60A is formed by stacking thin plate materials (60Aa, 60Ab, and 60Ac) having different radial lengths. Each plate material may be formed of the same material or different materials. When formed of different materials, the plate materials may be arranged so that the plate material formed of a material with high wear resistance is used as the plate material from the collision surface 61 side toward the back surface 65 side. By doing so, self-shaping can be more suitably exhibited.

[0089] [Modification Example 2] Also, as shown in FIG. 8, the blade may have a constant circumferential length (plate thickness) throughout the radial direction. The blade 60B has a curved surface 62 formed on the collision surface 61 by bending a flat plate-shaped blade. Thus, in this modification example, the blade 60B having a curved surface can be formed only by bending, so that the blade 60B can be easily manufactured. In addition, since the circumferential length (plate thickness) of the blade 60B is constant throughout the radial direction, the length that can tolerate wear becomes longer throughout the radial direction. Therefore, the durability of the blade 60B can be improved.

[0090] [Modification Example 3] Also, as shown in FIG. 9, a plurality of recesses 80 may be formed in the curved surface 62 of the blade. The blade 60C has a constant circumferential length (plate thickness) throughout the radial direction, and a plurality of recesses 80 are formed in the curved surface 62. Examples of the recess 80 include, for example, dimples. In the blade 60C, a self-aligning structure is formed by the plurality of recesses 80. The recess 80 is formed to have a curvature radius that is sufficiently smaller than the curvature radius of the curved surface 62. That is, the recess 80 is sized so as not to affect the general shape of the curved surface 62. Specifically, for example, when the curvature radius R of the curved surface 62 is 100, if the curvature radius R of the recess 80 is about 10 or less, it does not affect the general shape of the curved surface 62. In the self-aligning structure, by forming the recess 80 in the curved surface 62, the pulverized fuel enters the recess 80. Thereby, the surface of the curved surface 62 is covered with the pulverized fuel. The contact between the flowing pulverized fuel and the curved surface 62 is suppressed by the pulverized fuel covering the surface of the curved surface 62. Therefore, wear of the curved surface 62 can be suppressed. Note that the same effect can be obtained by forming corrugations instead of the recesses 80. Also, the recesses 80 or corrugations are not limited to the curved surface 62 and may be provided on the flat surface 63, and wear can be suppressed by providing them on the collision surface 61.

[0091] [Modification Example 4] In the above-described embodiment, an example in which the blade 60 has a uniform shape in the vertical direction has been described, but the present disclosure is not limited thereto. For example, as shown in FIG. 10, the cross-sectional shape of the blade 60D may smoothly change in the vertical direction. That is, as shown in FIG. 10, the cross-sectional shape (see FIG. 11) at the upper part of the blade 60D and the cross-sectional shape (see FIG. 12) at the lower part may be different shapes. Specifically, in the example shown in FIG. 10, the blade 60D has a smaller curved surface in the cross-sectional shape at the upper part than in the cross-sectional shape at the lower part. This is because, as shown in FIG. 2 and the like, the blade 60D is inclined such that the upper part is farther from the central axis C than the lower part, so the centrifugal force R1 (see FIG. 2) acting on the upper part is greater than the centrifugal force R2 (see FIG. 2) acting on the lower part. In the upper part where the acting centrifugal force is strong, even if the curved surface 62 is made smaller to make it difficult to bounce outward in the radial direction, the pulverized fuel can be sufficiently bounced outward in the radial direction. On the other hand, in the lower part where the acting centrifugal force is weak, by making the curved surface 62 larger to make it easier to bounce outward in the radial direction, the pulverized fuel can be sufficiently bounced outward in the radial direction. Therefore, in the example shown in FIG. 10, even when the blade 60D is inclined with respect to the vertical direction, the mode of bouncing the pulverized fuel outward in the radial direction can be made uniform in the vertical direction.

[0092] In addition, as shown in FIG. 13, in the case of the rotary classifier 16A in which the blade 60E extends along the vertical direction (that is, when not inclined), since the centrifugal force R3 acting on the blade 60E does not change in the vertical direction, as shown in FIG. 14, it may have a uniform shape in the vertical direction. By having a uniform shape in the vertical direction, a simple structure can be achieved, so it can be easily manufactured.

[0093] Further, the blade may have a rectangular cross-sectional shape without forming a curved surface at the upper end portion 72 and the lower end portion 73 of the main body portion 70 where it is fixed to the upper end portion and the lower end portion. By doing so, the surface for fixing the blade to the main body portion 70 can be enlarged as compared with the case of forming a curved surface. Therefore, the blade can be firmly fixed.

[0094] Further, the curved surface 62 does not have to be a complete curved surface, and a digital curved surface may be formed by combining planes with a minute difference in angle or by combining thin layers in a stepped manner. Also, depending on the required classification performance, a plane may be inserted at the tip or a part of the middle of the curved surface 62.

[0095] The classifier, power generation plant, and operating method of the classifier described in the embodiments described above are understood as follows, for example. A classifier according to one aspect of the present disclosure is a classifier (16) that classifies particles guided together with a carrier gas into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size, and extends in the vertical direction, and is arranged circumferentially on a virtual circle (V) centered on a central axis (C) extending in the vertical direction, and includes a plurality of blades (60) through which the particles are guided together with the carrier gas directed from the outer side in the radial direction toward the inner side, and the blade (60) has a collision surface (61) against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction, and the collision surface (61) has a larger angle formed by a tangent line of the virtual circle (V) and a perpendicular line to the collision surface (61) on the outer side in the radial direction than on the inner side in the radial direction.

[0096] Generally, for the blades of a classifier, crushed solid fuel (hereinafter referred to as "crushed fuel") having a larger particle size is more likely to collide with the outer side in the radial direction, and crushed fuel having a smaller particle size is more likely to collide with the inner side in the radial direction. Also, the larger the angle formed by a tangent line of the virtual circle and a perpendicular line to the collision surface (hereinafter referred to as the "inclination angle"), the stronger the crushed fuel is bounced to the outer side in the radial direction. In the above configuration, the collision surface of the blade has a larger inclination angle on the outer side in the radial direction than on the inner side in the radial direction. That is, on the outer side in the radial direction where pulverized fuel with a large particle size is likely to collide, it has a shape with a strong force to bounce the pulverized fuel to the outer side in the radial direction. Therefore, the pulverized fuel with a large particle size can be strongly bounced to the outer side in the radial direction. On the other hand, the collision surface of the blade has a larger inclination angle on the inner side in the radial direction than on the outer side in the radial direction. That is, on the inner side in the radial direction where pulverized fuel with a small particle size is likely to collide, it has a shape with a weak force to bounce the pulverized fuel to the outer side in the radial direction. Therefore, the pulverized fuel with a small particle size is easily guided to the inner side in the radial direction together with the conveying gas flowing from the outer side to the inner side in the radial direction. Thereby, the pulverized fuel with a small particle size can be bounced to the inner side in the radial direction. In this way, since it is easy to bounce the pulverized fuel with a large particle size to the outer side in the radial direction and easy to bounce the pulverized fuel with a small particle size to the inner side in the radial direction, the classification performance of the classifier can be improved.

[0097] Further, in the classifier according to one aspect of the present disclosure, the collision surface (61) has a curved surface (62) that curves so as to protrude, and the curved surface (62) has a larger angle formed by the tangent of the virtual circle (V) and the perpendicular to the collision surface (61) on the outer side in the radial direction than on the inner side in the radial direction.

[0098] For example, when the blade has a folded plate shape in which a flat plate-like outer portion and an inner portion with different inclination angles are connected, depending on the intrusion position of the pulverized fuel, it is determined whether the pulverized fuel collides with the outer portion and is bounced to the outside of the blade, or the pulverized fuel collides with the inner portion and is bounced to the inside of the blade. Therefore, even for pulverized fuel of the same particle size, depending on the intrusion position, a case where it is classified (when bounced to the outside) and a case where it is not classified (when bounced to the outside) may occur. Thus, there is a possibility that the classification performance may deteriorate. On the other hand, in the above configuration, the collision surface is curved. Thereby, the region depending on the intrusion position can be reduced. Therefore, the classification performance can be improved.

[0099] In addition, in the above configuration, the curved surface of the blade has a larger inclination angle on the outer side in the radial direction than on the inner side in the radial direction. That is, on the outer side in the radial direction where pulverized fuel with a large particle size is likely to collide, the shape is such that the force that repels the pulverized fuel to the outer side in the radial direction is strong. Therefore, the pulverized fuel with a large particle size can be strongly repelled to the outer side in the radial direction. On the other hand, the curved surface of the blade has a larger inclination angle on the inner side in the radial direction than on the outer side in the radial direction. That is, on the inner side in the radial direction where pulverized fuel with a small particle size is likely to collide, the shape is such that the force that repels the pulverized fuel to the outer side in the radial direction is weak. Therefore, the pulverized fuel with a small particle size is easily guided to the inner side in the radial direction together with the conveying gas flowing from the outer side to the inner side in the radial direction. Thereby, the pulverized fuel with a small particle size can be repelled to the inner side in the radial direction. In this way, in the curved surface, the pulverized fuel with a large particle size is easily repelled to the outer side in the radial direction, and the pulverized fuel with a small particle size is easily repelled to the inner side in the radial direction, so that the classification performance of the classifier can be improved.

[0100] The curved surface includes a polygonal surface formed by combining planes with a minute difference in angle, and a stepped surface formed by shifting and laminating the ends of thin layers.

[0101] Further, in the classifier according to one aspect of the present disclosure, the collision surface (61) has the curved surface (62) and a flat surface (63) disposed on the inner side in the radial direction than the curved surface (62).

[0102] In the above configuration, the collision surface has a curved surface and a flat surface. Since the flat surface is easier to manufacture than the curved surface, the blade can be easily manufactured as compared with the case where the entire collision surface is a curved surface. Also, generally, the influence of the force of the conveying gas (that is, the force from the outer side to the inner side in the radial direction) becomes larger toward the inner side in the radial direction of the collision surface, so the influence of the force repelling to the outer side due to the inclination angle becomes smaller. In the above configuration, since the flat surface is formed on the inner side in the radial direction, it is possible to suppress a decrease in classification performance due to the formation of the flat surface.

[0103] Further, in the classifier according to one aspect of the present disclosure, the blade (60) has a shorter circumferential length as it extends toward the outer side in the radial direction.

[0104] In the above configuration, the circumferential length (length in the plate thickness direction) of the blade becomes shorter as it extends toward the outer side in the radial direction. As a result, the plate thickness of the blade can be reduced, making it difficult for tools or the like to interfere with adjacent blades or the like when the blade is attached. Therefore, the blade attachment work can be facilitated.

[0105] Further, in the classifier according to one aspect of the present disclosure, the blade (60) has a constant circumferential length throughout the entire radial direction.

[0106] In the above configuration, the circumferential length (length in the plate thickness direction) of the blade is constant throughout the entire radial direction. As a result, for example, by bending a flat plate-shaped blade, a blade having a curved surface can be manufactured. Therefore, the blade can be easily manufactured. In addition, since the circumferential length (length in the plate thickness direction) of the blade is constant throughout the entire radial direction, the length that can tolerate wear becomes longer. Therefore, the durability of the blade can be improved.

[0107] Further, in the classifier according to one aspect of the present disclosure, a plurality of recesses are formed in the collision surface (61).

[0108] In the above configuration, a plurality of recesses are formed in the collision surface. That is, a self-aligning structure is configured by the plurality of recesses. As a result, when the pulverized fuel enters the recesses, the surface of the collision surface is covered with the pulverized fuel. The contact between the flowing pulverized fuel and the collision surface is suppressed by the pulverized fuel covering the surface of the collision surface. Therefore, wear of the collision surface can be suppressed.

[0109] In addition, a power generation plant according to one aspect of the present disclosure includes the classifier (16) described in any of the above, a boiler (200) that burns pulverized solid fuel having a predetermined particle size or less classified by the classifier (16), and a power generation unit that generates power using steam generated by the boiler (200).

[0110] In addition, an operation method of a classifier according to one aspect of the present disclosure is an operation method of a classifier (16) that classifies particles guided together with a conveying gas into the particles larger than a predetermined particle size and the particles having a predetermined particle size or less. The classifier (16) extends in the vertical direction and is arranged side by side in the circumferential direction on a virtual circle (V) centered on the central axis extending in the vertical direction. The classifier (16) includes a plurality of blades (60) through which the particles are guided together with the conveying gas directed from the outside in the radial direction toward the inside. The blade (60) has a collision surface (61) against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles having a predetermined particle size or less are bounced in the inner direction in the radial direction. The collision surface (61) has a larger angle formed by the tangent to the virtual circle (V) and the perpendicular to the collision surface (61) on the outer side in the radial direction than on the inner side in the radial direction. The method includes a step of classifying the particles into the particles larger than a predetermined particle size and the particles having a predetermined particle size or less by the blade (60).

Explanation of Reference Numerals

[0111] 1: Power generation plant 10: Mill 11: Housing 12: Pulverizing table 13: Pulverizing roller 14: Driving unit 15: Mill motor 16: Rotary classifier 17: Fuel supply unit 18: Classifier motor 19: Outlet port 20: Coal feeder 21: Bunker 22: Conveying unit 23: Coal feeder motor 24: Downspout 30: Blower section 30a: Hot gas flow path 30b: Cold gas flow path 30c: Hot gas damper 30d: Cold gas damper 31: Primary air blower 32: Forced ventilation fan 34: Heat exchanger 35: Denitration device 36: Flue 40: State detection section 41: Bottom surface part 42: Ceiling part 45: Journal head 47: Support arm 48: Support shaft 49: Pressing device 50: Control section 60: Blade 61: Collision surface 62: Curved surface 63: Flat surface 65: Back surface 70: Main body part 71: Cylindrical shaft 72: Upper end part 73: Lower end part 80: Concave part 100: Solid fuel pulverizing device 100a: Primary air flow path 100b: Fine powder fuel supply flow path 200: Boiler 210: Firebox 220: Burner

Claims

1. A classifier that classifies particles guided together with a conveying gas into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size, comprising a plurality of blades that extend in the vertical direction, are arranged side by side in the circumferential direction on a virtual circle centered on a central axis extending in the vertical direction, and through which the particles are guided together with the conveying gas that flows from the outside in the radial direction toward the inside, wherein the blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction, wherein the collision surface has a larger angle formed by a tangent to the virtual circle and a perpendicular to the collision surface on the outer side in the radial direction than on the inner side in the radial direction, wherein the collision surface has a curved surface that curves so as to protrude, wherein the curved surface has a larger angle formed by a tangent to the virtual circle and a perpendicular to the collision surface on the outer side in the radial direction than on the inner side in the radial direction, wherein the blade has a smaller curved surface in the cross-sectional shape at the upper part than in the cross-sectional shape at the lower part.

2. The classifier according to claim 1, wherein the collision surface has the curved surface and a flat surface arranged on the inner side in the radial direction than the curved surface.

3. The classifier according to claim 1 or claim 2, wherein the blade has a shorter circumferential length as it goes toward the outer side in the radial direction.

4. A classifier that classifies particles guided together with a conveying gas into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size, comprising a plurality of blades that extend in the vertical direction, are arranged side by side in the circumferential direction on a virtual circle centered on a central axis extending in the vertical direction, and through which the particles are guided together with the conveying gas that flows from the outside in the radial direction toward the inside, wherein the blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction, wherein the collision surface has a larger angle formed by a tangent to the virtual circle and a perpendicular to the collision surface on the outer side in the radial direction than on the inner side in the radial direction, wherein the collision surface has a curved surface that curves so as to protrude, wherein the curved surface has a larger angle formed by a tangent to the virtual circle and a perpendicular to the collision surface on the outer side in the radial direction than on the inner side in the radial direction, The blade has self-shaping wear resistance so that the curved surface is maintained, and is a classifier. **Claim 5**: A classifier that classifies particles guided together with a conveying gas into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size, including a plurality of blades that extend in the vertical direction, are arranged side by side in the circumferential direction on a virtual circle centered on the central axis extending in the vertical direction, and guide the particles together with the conveying gas that flows from the outside in the radial direction toward the inside. The blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent of the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. The blade has a plurality of plate materials laminated in the circumferential direction. A classifier in which the plurality of plate materials are arranged so as to be plate materials formed of a material with high wear resistance from the collision surface side toward the back surface side. **Claim 6**: A classifier that classifies particles guided together with a conveying gas into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size, including a plurality of blades that extend in the vertical direction, are arranged side by side in the circumferential direction on a virtual circle centered on the central axis extending in the vertical direction, and guide the particles together with the conveying gas that flows from the outside in the radial direction toward the inside. The blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent of the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. The blade has a plurality of plate materials laminated in the circumferential direction. A classifier in which the plurality of plate materials have different lengths in the radial direction. **Claim 7** The classifier according to claim 1 or claim 2, wherein the blade has a constant length in the circumferential direction throughout the entire radial direction. **Claim 8**: A classifier that classifies particles guided together with a conveying gas into the particles larger than a predetermined particle size and the particles equal to or smaller than the predetermined particle size, extending in the vertical direction, arranged side by side in the circumferential direction on a virtual circle centered on the central axis extending in the vertical direction, and including a plurality of blades through which the particles are guided together with the conveying gas flowing from the outside in the radial direction toward the inside. The blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than a predetermined particle diameter are bounced in the outer direction in the radial direction, and the particles having a diameter less than or equal to the predetermined particle diameter are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. A classifier in which a plurality of recesses are formed on the collision surface.

9. A classifier according to any one of Claims 1 to 8, a boiler that burns the pulverized solid fuel having a particle diameter less than or equal to a predetermined particle diameter classified by the classifier, and a power generation unit that generates power using the steam generated by the boiler. A power generation plant comprising:

10. An operation method of a classifier that classifies particles guided together with a conveying gas into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter, wherein the classifier extends in the vertical direction, includes a plurality of blades arranged side by side in the circumferential direction on a virtual circle centered on the central axis extending in the vertical direction, and the particles are guided together with the conveying gas flowing from the outside in the radial direction toward the inside. The blade has a collision surface against which the guided particles collide, and among the collided particles, the particles larger than a predetermined particle diameter are bounced in the outer direction in the radial direction, and the particles having a diameter less than or equal to the predetermined particle diameter are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. The collision surface has a curved surface that curves so as to protrude. On the curved surface, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. The blade has a smaller curved surface in the cross-sectional shape at the upper part than in the cross-sectional shape at the lower part. An operation method of a classifier including a step of classifying the particles into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter by the blade.

11. An operation method of a classifier that classifies particles guided together with a conveying gas into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter, The classifier extends in the vertical direction and is arranged circumferentially on a virtual circle centered on the central axis extending in the vertical direction. The classifier includes a plurality of blades through which the particles are guided together with the conveying gas flowing from the outer side in the radial direction toward the inner side. The blade has a collision surface against which the guided particles collide. Among the collided particles, the particles larger than a predetermined particle diameter are repelled in the outer direction in the radial direction, and the particles having a diameter less than or equal to the predetermined particle diameter are repelled in the inner direction in the radial direction. On the outer side in the radial direction, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger than that on the inner side in the radial direction with respect to the collision surface. The collision surface has a curved surface that curves so as to protrude. On the outer side in the radial direction, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger than that on the inner side in the radial direction with respect to the curved surface. The blade has self-shaping properties such that it wears in a manner that maintains the curved surface. A method for operating a classifier, the method including a step of classifying the particles by the blade into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter.

12. A method for operating a classifier that classifies particles guided together with a conveying gas into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter, wherein the classifier extends in the vertical direction and is arranged circumferentially on a virtual circle centered on the central axis extending in the vertical direction. The classifier includes a plurality of blades through which the particles are guided together with the conveying gas flowing from the outer side in the radial direction toward the inner side. The blade has a collision surface against which the guided particles collide. Among the collided particles, the particles larger than a predetermined particle diameter are repelled in the outer direction in the radial direction, and the particles having a diameter less than or equal to the predetermined particle diameter are repelled in the inner direction in the radial direction. On the outer side in the radial direction, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger than that on the inner side in the radial direction with respect to the collision surface. The blade has a plurality of plate materials laminated in the circumferential direction. The plurality of plate materials are arranged such that, from the collision surface side toward the back surface side, the plate materials are formed of a material having high wear resistance. A method for operating a classifier, the method including a step of classifying the particles by the blade into particles larger than a predetermined particle diameter and particles having a diameter less than or equal to the predetermined particle diameter.

13. A method of operating a classifier that classifies particles introduced together with a conveying gas into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size, comprising: The classifier extends in the vertical direction and includes a plurality of blades arranged circumferentially on a virtual circle centered on a central axis extending in the vertical direction, and the particles are introduced together with the conveying gas flowing from the outside in the radial direction toward the inside. The blade has a collision surface against which the introduced particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. The blade has a plurality of plate materials laminated in the circumferential direction. The plurality of plate materials have different lengths in the radial direction. A method of operating a classifier, comprising a step of classifying the particles into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size by the blade.

14. A method of operating a classifier that classifies particles introduced together with a conveying gas into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size, comprising: The classifier extends in the vertical direction and includes a plurality of blades arranged circumferentially on a virtual circle centered on a central axis extending in the vertical direction, and the particles are introduced together with the conveying gas flowing from the outside in the radial direction toward the inside. The blade has a collision surface against which the introduced particles collide, and among the collided particles, the particles larger than the predetermined particle size are bounced in the outer direction in the radial direction, and the particles equal to or smaller than the predetermined particle size are bounced in the inner direction in the radial direction. On the collision surface, the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface is larger on the outer side in the radial direction than on the inner side in the radial direction. A plurality of recesses are formed in the collision surface. A method of operating a classifier, comprising a step of classifying the particles into particles larger than a predetermined particle size and particles equal to or smaller than the predetermined particle size by the blade.

Images