WO2022209456A1

WO2022209456A1 - Classifier, power plant, and method for operating classifier

Info

Publication number: WO2022209456A1
Application number: PCT/JP2022/007548
Authority: WO
Inventors: 聡太朗山口
Original assignee: 三菱重工業株式会社; 三菱パワー株式会社
Priority date: 2021-03-31
Filing date: 2022-02-24
Publication date: 2022-10-06
Also published as: JP2022156406A; CN116568403A; EP4238653A1

Abstract

The purpose of the present invention is to improve classifying performance. A rotary classifier (16) classifies crushed solid fuel guided along with primary air into a coarse powder fuel (B1) having a particle size greater than a predetermined particle size and a fine powder fuel (B2) having a particle size equal to or less than the predetermined particle size. The rotary classifier (16) comprises a plurality of blades (60) that extend vertically, that are circumferentially positioned side by side on a virtual circle (V) centered about a vertically extending center axis (C), and that guide solid fuel along with transport gas heading from the outer side to the inner side along the radial direction. The blades (60) have collision surfaces (61) against which the guided crushed fuel collides. Said collision surfaces (61) causing coarse powder fuel (B1) of the crushed fuel that has collided therewith to be repelled radially outward, and fine powder fuel (B2) of the crushed fuel that has collided therewith to be repelled radially inward, the particles of the coarse powder fuel (B1) exceeding a predetermined size and the particles of the fine powder fuel (B2) not exceeding the predetermined particle size. In each of the collision surfaces (61), the angle formed by the tangent of the virtual circle (V) and a normal to the collision surface (61) is greater on the radially outer side than on the radially inner side.

Description

Classifier, power plant, and classifier operation method

The present disclosure relates to a classifier, a power plant, and a classifier operating method.

Conventionally, solid fuels (carbon-containing solid fuels) such as coal and biomass fuels are pulverized into fine powder within a predetermined particle size range by a pulverizer (mill) and supplied to combustion equipment. In the mill, the solid fuel such as coal and biomass fuel put into the grinding table is sandwiched between the grinding table and the grinding rollers to grind it, and the carrier gas (primary air) supplied from the periphery of the grinding table grinds it. Of the solid fuel that has been pulverized into fine powder (hereinafter, pulverized solid fuel is referred to as "pulverized fuel"), pulverized fuel within a predetermined particle size range (fineness) is sorted by a classifier and transported to a boiler. and combusted in a combustion device. In a thermal power plant, steam is generated by exchanging heat with combustion gas produced by combusting pulverized fuel in a boiler, and the steam rotates a steam turbine to rotate a generator connected to the steam turbine. Electricity is generated by this.

For example, a rotary classifier is known as one of the classifiers provided in the mill. A rotary classifier has a plurality of blades that are evenly spaced in the circumferential direction about the axis of rotation. In rotary classifiers, coarse fuel (pulverized fuel with a particle size larger than a predetermined particle size) is heavy and exerts a large centrifugal force when the pulverized fuel passes between multiple blades that rotate about the rotation axis. is repelled to the outer peripheral side of the blade, and finely divided fuel (pulverized fuel smaller than a predetermined particle size), which is small in weight and has a large conveying force due to the primary air flow, is passed through the inner peripheral side of the blade to classify it. is.
Further, the rotary classifier has a main body portion that rotates around a rotation axis. By holding the upper and lower sides of the blade, the main body can revolve the blade around the rotation axis. The main body is held by bearings and rotated at a predetermined rotational speed by a power source such as a motor. By changing the rotation speed, the force acting on the pulverized fuel can be adjusted to obtain a predetermined fineness (classification performance).

In general, the blades of rotary classifiers are flat. However, in order to improve the classification performance (the performance of repelling coarse fuel to the outer periphery of the blade and passing fine fuel through the blade), the blade of the rotary classifier is changed from a simple flat plate shape. There is a thing (for example, patent document 1).
In Patent Document 1, a plurality of classifying blades rotating around a vertical axis form a large angle with the radial direction of rotation at the upstream end (entrance end), and the angle is small at the downstream end (outlet end). A type classifier is described. That is, Patent Document 1 describes a rotary classifier in which classifying blades are bent.

JP-A-7-51630

The classifying vane (blade) described in Patent Document 1 has a shape that is bent such that an inlet side portion (diametrically outer portion) and an outlet side portion (diametrically inner portion) have different angles (angles with respect to the radial direction). doing In general, the particle size range of the pulverized fuel that can be repelled toward the outer circumference changes depending on the angle of the blade. For this reason, the blade described in Patent Document 1 is repelled to the outer peripheral side at the inlet side of the blade, but the pulverized fuel with an intermediate particle size that cannot be repelled to the outer peripheral side at the outlet side collides with the blade. Sometimes. In this case, the result of classification will be greatly different between when the particles collide with the outlet side portion and when they collide with the inlet side portion.
Whether the inlet or outlet portion of the blade is impacted depends on the entry position of the pulverized fuel into the rotary classifier. Specifically, when it enters the rotary classifier from a distance in the radial direction of the blade, it collides with the outlet side, and when it enters the rotary classifier from near the blade in the radial direction, it collides with the inlet side. collide.

As described above, in the apparatus described in Patent Document 1, when pulverized fuel having an intermediate particle size enters the rotary classifier from a distance from the blade and collides with the inlet side portion of the blade, the collided pulverized fuel is It is returned to the crushing section (crushing table) by being repelled to the outer peripheral side. On the other hand, when pulverized fuel with an intermediate particle size enters the rotary classifier from the vicinity of the blade and collides with the exit side of the blade, the pulverized fuel that collides passes through the inner circumference and is led to the boiler. It will happen. Since it is difficult to control the entry position of the pulverized fuel into the rotary classifier, in the device described in Patent Document 1, the pulverized fuel with an intermediate particle size collides with the inlet side portion and bounces to the outer peripheral side. It is random with respect to the particle diameter whether the particles collide with the exit side portion and pass through to the inner peripheral side. That is, even if the pulverized fuel has the same particle size, there are cases where it is classified (repelled toward the outer circumference) and cases where it is not classified (where it is repelled toward the inner circumference). For this reason, there is a possibility that the classification of the pulverized fuel according to the target particle size cannot be performed with high accuracy, that is, the classification performance is deteriorated.
In particular, the greater the difference in the angle between the inlet side portion and the outlet side portion, the larger the particle size range in which whether or not the particles are classified becomes random with respect to the particle size. . In addition, even if the rotational speed of the blade is changed, only the upper limit or lower limit of the particle size range in which whether or not the particles are classified is changed at random with respect to the particle size, thereby solving the problem of deterioration in classification performance. I couldn't.

The present disclosure has been made in view of such circumstances, and aims to provide a classifier, a power plant, and a method of operating the classifier that can improve the classification performance.

In order to solve the above problems, the classifier, power plant, and classifier operating method 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 carrier gas into the particles larger than a predetermined particle diameter and the particles having a predetermined particle diameter or less, wherein A plurality of blades that extend and are arranged in a circumferential direction on a virtual circle centered on the central axis that extends in the vertical direction, and that guide the particles together with the carrier gas directed radially inward from the outer side. , wherein the blade collides with the guided particles, and out of the collided particles, flips the particles larger than a predetermined particle diameter outward in the radial direction, and removes the particles with a predetermined particle diameter or less. It has a collision surface that bounces inward in the radial direction, and the radial outer side of the collision surface is formed by a tangent to the imaginary circle and a perpendicular line to the collision surface more than the radial inner side. Large angle.

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 having a predetermined particle size or less. The classifier extends in the vertical direction and is arranged circumferentially on an imaginary circle centered on the central axis extending in the vertical direction. a plurality of blades through which the particles are guided together with the gas, and the blades collide with the guided particles, and among the collided particles, the particles larger than a predetermined particle diameter are removed in the radially outward direction. and has a collision surface that repels the particles having a predetermined particle diameter or less toward the inner side in the radial direction, and the outer side of the collision surface in the radial direction is closer to the virtual circle than the inner side in the radial direction. and the perpendicular to the collision surface form a large angle, and the blade classifies the particles into the particles larger than a predetermined particle diameter and the particles smaller than the predetermined particle diameter.

According to the present disclosure, it is possible to improve the classification performance.

1 is a configuration diagram showing a solid fuel pulverizer and a boiler according to an embodiment of the present disclosure; FIG. 1 is a vertical cross-sectional view showing a rotary classifier according to an embodiment of the present disclosure; FIG. 1 is a horizontal cross-sectional view showing a rotary classifier according to an embodiment of the present disclosure; FIG. 1 is a horizontal cross-sectional view of a blade according to an embodiment of the present disclosure; FIG. 5 is a graph of blade outward force acting on pulverized fuel and passage characteristics versus distance from the blade inlet in an embodiment of the present disclosure; 5 is a graph showing classification performance of a rotary classifier according to an embodiment of the present disclosure; FIG. 10 illustrates a modified blade according to an embodiment of the present disclosure; FIG. 10 illustrates a modified blade according to an embodiment of the present disclosure; FIG. 10 illustrates a modified blade according to an embodiment of the present disclosure; FIG. 10 illustrates a modified blade according to an embodiment of the present disclosure; 11 is a cross-sectional view taken along line XI-XI of FIG. 10; FIG. 11 is a cross-sectional view taken along line XII-XII of FIG. 10; FIG. FIG. 5 is a diagram showing a modification of the rotary classifier according to the embodiment of the present disclosure; FIG. 10 illustrates a modified blade according to an embodiment of the present disclosure; FIG. 11 shows a blade according to a comparative example of the present disclosure; FIG. 11 shows a blade according to a comparative example of the present disclosure; FIG. 5 is a graph showing blade outward force acting on pulverized fuel and passage characteristics versus distance from the blade inlet in a comparative example of the present disclosure; 4 is a graph showing the relationship between the size of pulverized fuel passing through flat blades and passage characteristics. 5 is a graph showing the relationship between the size of pulverized fuel passing through a flat blade and the distance from the blade inlet. FIG. 4 is a schematic diagram showing the classification effect in airflow; 4 is a graph showing the relationship between the particle size of pulverized fuel that collides with the blade and the distance from the inlet of the blade. 4 is a graph showing classification performance of a rotary classifier according to a comparative example of the present disclosure; FIG. 11 shows a blade according to a comparative example of the present disclosure; FIG. 5 is a graph showing blade outward force acting on pulverized fuel and passage characteristics versus distance from the blade inlet in a comparative example of the present disclosure; 4 is a graph showing classification performance of a rotary classifier according to a comparative example of the present disclosure;

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. A power plant 1 according to this embodiment includes a solid fuel crusher 100 and a boiler 200 .
In the following description, "upper" means the vertically upper direction, and "upper" such as upper part or top surface means the vertically upper part. Similarly, "lower" indicates the vertically lower part, and the vertical direction is not exact and includes errors.

As an example, the solid fuel pulverization device 100 of the present embodiment pulverizes a solid fuel (carbon-containing solid fuel) such as coal or biomass fuel, generates pulverized fuel, and supplies it to the burner (combustion device) 220 of the boiler 200. is.
The power plant 1 including the solid fuel crushing device 100 and the boiler 200 shown in FIG. A system including a plurality of solid fuel pulverizers 100 may be used.

The solid fuel pulverizer 100 of the present embodiment includes a mill 10, a coal feeder (fuel feeder) 20, an air blower (carrier gas feeder) 30, a state detector 40, and a controller (judgment unit). 50.

The mill 10 for pulverizing solid fuel such as coal and biomass fuel to be supplied to the boiler 200 into pulverized fuel, which is finely powdered solid fuel, may be of a type that pulverizes only coal or pulverizes only biomass fuel. Alternatively, it may be a form in which the biomass fuel is pulverized together with the coal.
Here, the biomass fuel is a renewable organic resource derived from living organisms. chips), etc., and are not limited to those presented here. Since biomass fuel takes in carbon dioxide during the growth process of biomass, it is considered to be carbon-neutral because it does not emit carbon dioxide that becomes a global warming gas.

The mill 10 includes a housing 11 , a grinding table (rotary table) 12 , a grinding roller 13 , a drive section 14 , a mill motor 15 connected to the drive section 14 to rotate the grinding table 12 , and a rotary classifier 16 . , a fuel supply unit 17 and a classifier motor 18 for rotating a rotary classifier 16 .
The housing 11 is a casing that is formed in a vertically extending cylindrical shape and houses the grinding table 12 , the grinding roller 13 , the rotary classifier 16 , and the fuel supply section 17 .
A fuel supply unit 17 is attached to the central portion of the ceiling portion 42 of the housing 11 . The fuel supply part 17 supplies the solid fuel introduced from the bunker 21 into the housing 11, is arranged in the center position of the housing 11 along the vertical direction, and extends to the inside of the housing 11 at its lower end. ing.

A driving portion 14 is installed near the bottom portion 41 of the housing 11, and a grinding table 12 that is rotated by driving force transmitted from a mill motor 15 connected to the driving portion 14 is rotatably arranged.
The crushing table 12 is a circular member in plan view, and is arranged so that the lower ends of the fuel supply section 17 face each other. The upper surface of the crushing table 12 may have, for example, a sloping shape in which the central portion is low and the outer peripheral portion is bent upward. The fuel supply unit 17 supplies solid fuel (for example, coal or biomass fuel in this embodiment) from above toward the crushing table 12 below, and the crushing table 12 feeds the supplied solid fuel between the crushing roller 13 and the crushing roller 13. Smash.

When the solid fuel is introduced from the fuel supply portion 17 toward the substantially central region of the grinding table 12, the centrifugal force due to the rotation of the grinding table 12 guides the solid fuel to the outer peripheral side of the grinding table 12, and the solid fuel is pushed toward the grinding table 12. and the crushing roller 13 and crushed. The pulverized solid fuel is blown upward by a carrier gas (hereinafter referred to as primary air) guided from a carrier gas flow path (hereinafter referred to as a primary air flow path) 100a and rotated. It is led to the type classifier 16 .
An air outlet (not shown) is provided on the outer periphery of the grinding table 12 to allow the primary air flowing from the primary air flow path 100 a to flow out to the space above the grinding table 12 in the housing 11 . A swirl vane (not shown) is installed at the blowout port to give a swirling force to the primary air blown out from the blowout port. The primary air to which the swirl force is applied by the swirl vane becomes an air flow having a swirling velocity component, and the solid fuel pulverized on the pulverization table 12 is sent to the rotary classifier 16 located above in the housing 11. transport. Of the pulverized solid fuel, those larger than a predetermined particle size are classified by the rotary classifier 16, or fall without reaching the rotary classifier 16 and are returned to the pulverization table 12. Then, it is pulverized again between the pulverizing table 12 and the pulverizing roller 13 .

The crushing roller 13 is a rotating body that crushes the solid fuel supplied from the fuel supply unit 17 onto the crushing table 12 . The crushing roller 13 is pressed against the upper surface of the crushing table 12 and cooperates with the crushing table 12 to crush the solid fuel.
Although only one crushing roller 13 is shown as a representative in FIG. . For example, three crushing rollers 13 are equally spaced in the circumferential direction at angular intervals of 120° on the outer circumference. In this case, the portions where the three crushing rollers 13 come into contact with the upper surface of the crushing table 12 (the portions pressed) are equidistant from the rotation center axis of the crushing table 12 .

The crushing roller 13 can be vertically swung by a journal head 45, and is supported on the upper surface of the crushing table 12 so as to move toward and away from it. When the crushing table 12 rotates while the outer peripheral surface is in contact with the solid fuel on the upper surface of the crushing table 12 , the crushing roller 13 receives a rotational force from the crushing table 12 and rotates with the crushing roller 13 . When the solid fuel is supplied from the fuel supply unit 17, the solid fuel is pressed between the crushing roller 13 and the crushing table 12 and crushed.

The support arm 47 of the journal head 45 is supported by a horizontal support shaft 48 at its intermediate portion so that the crushing roller 13 can swing vertically around the support shaft 48 on the side surface of the housing 11 . A pressing device 49 is provided at the upper end of the support arm 47 on the vertical upper side. The pressing device 49 is fixed to the housing 11 and applies a load to the crushing roller 13 via the support arm 47 or the like so as to press the crushing roller 13 against the crushing table 12 .

The driving unit 14 is a device that transmits a driving force to the grinding table 12 and rotates the grinding table 12 around its 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 .

The rotary classifier 16 is provided in the upper part of the housing 11 and has a hollow, substantially inverted conical outer shape. The rotary classifier 16 has a plurality of vertically extending blades 60 on its outer periphery. Each blade 60 is provided at predetermined intervals (equal intervals) around the central axis C of the rotary classifier 16 .
The rotary classifier 16 classifies the solid fuel pulverized by the pulverization table 12 and the pulverization roller 13 (hereinafter, the pulverized solid fuel is referred to as "pulverized fuel") into a predetermined particle size (for example, 70 to 100 μm for coal). Classified into larger ones (hereinafter, pulverized fuel exceeding a predetermined particle size is referred to as "coarse fuel") and those with a predetermined particle size or less (hereinafter, pulverized fuel with a predetermined particle size or less is referred to as "fine fuel"). It is a device that The rotary classifier 16, which classifies by rotation, is also called a rotary separator. 2) rotates around the fuel supply unit 17. As shown in FIG. Details of the rotary classifier 16 will be described later.
As the classifier, a fixed classifier having a fixed hollow inverted conical casing and a plurality of fixed swirl vanes instead of the blades 60 on the outer periphery of the casing may be used.

The pulverized fuel reaching the rotary classifier 16 is knocked down by the blades 60 due to the relative balance between the centrifugal force generated by the rotation of the blades 60 and the centripetal force caused by the primary air flow. , is returned to the grinding table 12 to be ground again, and the pulverized fuel is directed to the outlet port 19 in the ceiling 42 of the housing 11. As shown in FIG. The pulverized fuel classified by the rotary classifier 16 is discharged together with the primary air from the outlet port 19 to the pulverized fuel supply channel 100b and supplied to the burner 220 of the boiler 200 . The pulverized fuel supply channel 100b is also called a pulverized coal pipe when the solid fuel is coal.

The fuel supply unit 17 is attached so that the lower end extends to the inside of the housing 11 along the vertical direction so as to penetrate the ceiling part 42 of the housing 11, and the solid fuel introduced from the upper part of the fuel supply unit 17 is pulverized. It is supplied to the substantially central area of the table 12 . The fuel supply unit 17 is supplied with solid fuel from the coal feeder 20 .

The coal feeder 20 includes a conveying unit 22 and a coal feeder motor 23 . The conveying unit 22 is, for example, a belt conveyer, and the solid fuel discharged from the lower end of the down spout 24 directly below the bunker 21 is transferred to the fuel supply unit 17 of the mill 10 by the driving force applied from the coal feeder motor 23 . , and put into the fuel supply unit 17 .
Normally, primary air is supplied to the interior of the mill 10 for conveying the pulverized fuel to the burner 220 and has a higher pressure than the coal feeder 20 and the bunker 21 . A downspout 24, which is a pipe extending vertically and directly below the bunker 21, holds fuel in a stacked state inside. A sealing property is ensured so that primary air and pulverized fuel do not flow back to the bunker 21 side.
The amount of solid fuel supplied to the mill 10 is adjusted, for example, by the moving speed of the belt conveyor of the transport section 22 .

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

In this embodiment, the hot gas flow path 30a converts part of the air (outside air) delivered from the primary air fan 31 into hot gas heated by passing through a heat exchanger 34 such as an air preheater. supply. A hot gas damper 30c is provided downstream of the hot gas flow path 30a. The opening degree of the hot gas damper 30c is controlled by the controller 50. FIG. The flow rate of the hot gas supplied from the hot gas flow path 30a is determined by the degree of opening of the hot gas damper 30c.

The cold gas flow path 30b supplies part of the air sent from the primary air ventilator 31 as a normal temperature cold gas. A cold gas damper 30d is provided downstream of the cold gas flow path 30b. The opening degree of the cold gas damper 30 d is controlled by the controller 50 . The flow rate of the cold gas supplied from the cold gas flow path 30b is determined by the degree of opening of the cold gas damper 30d.

In this embodiment, the flow rate of the primary air is the sum of the flow rate of the hot gas supplied from the hot gas channel 30a and the flow rate of the cold gas supplied from the cold gas channel 30b. It is determined by the mixing ratio of the hot gas supplied from the flow path 30 a and the cold gas supplied from the cold gas flow path 30 b and is controlled by the controller 50 .
In addition, a part of the combustion gas discharged from the boiler 200 is guided to the hot gas supplied from the hot gas flow path 30a through a gas recirculation fan (not shown) and mixed, thereby supplying the heat gas from the primary air flow path 100a to the housing. The oxygen concentration of the primary air blown into the interior of 11 may be adjusted.

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

The controller 50 is a device that controls each part of the solid fuel crusher 100 .
The control unit 50 may, for example, transmit a driving instruction to the mill motor 15 to control the rotation speed of the grinding table 12 .
For example, the control unit 50 transmits a drive instruction to the classifier motor 18 to control the rotation speed of the rotary classifier 16 to adjust the classifying performance, thereby controlling the differential pressure of the mill 10, that is, the amount of pulverized fuel inside the mill 10. By optimizing the circulation amount within a predetermined range, the pulverized fuel can be stably supplied to the burner 220 . The classification performance is the performance necessary for classification, such as classification characteristics, passage characteristics, and classification accuracy, which will be described later.
Further, the control unit 50 transmits a drive instruction to, for example, the coal feeder motor 23 of the coal feeder 20 so that the transport unit 22 transports the solid fuel and supplies the solid fuel to the fuel supply unit 17 ( amount of coal fed) can be adjusted.
Further, the control unit 50 can control the opening degrees of the hot gas damper 30c and the cold gas damper 30d to adjust the flow rate and temperature of the primary air by transmitting the opening instruction to the air blowing unit 30 . Specifically, the control unit 50 sets the flow rate of the primary air supplied to the inside of the housing 11 and the temperature of the primary air at the outlet port 19 in correspondence with the coal supply amount for each type of solid fuel. The opening degrees of the hot gas damper 30c and the cold gas damper 30d are controlled so as to obtain a predetermined value.

The control unit 50 is composed of, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like. Also, the HDD may be replaced with a solid state disk (SSD) or the like.

Next, the boiler 200 that generates steam by burning the pulverized fuel supplied from the solid fuel crusher 100 will be described. Boiler 200 includes furnace 210 and burner 220 .

The burner 220 heats the primary air containing the pulverized fuel supplied from the pulverized fuel supply channel 100b and the air (outside air) delivered from the forced draft fan (FDF) 32 with the heat exchanger 34. It is a device that burns pulverized fuel and forms a flame using supplied secondary air. The pulverized fuel is burned in the furnace 210, and the high-temperature combustion gas is discharged outside the boiler 200 after passing through heat exchangers (not shown) such as an evaporator, superheater, and economizer.

Combustion gas discharged from the boiler 200 flows through the flue 36 . The combustion gas flowing through the flue 36 is denitrified by the denitrification device 35 . The denitrification device 35 supplies a reducing agent such as ammonia or urea water, which has an action to reduce nitrogen oxides, into the flow path through which the combustion gas flows, and reduces the nitrogen oxides and reduction in the combustion gas to which the reducing agent is supplied. By promoting the reaction with the agent by the catalytic action of the denitration catalyst installed in the denitration device 35, nitrogen oxides in the combustion gas are removed and reduced. The denitrified combustion gas undergoes heat exchange between the air sent from the primary air fan 31 and the air sent from the forced draft fan 32 in a heat exchanger 34 such as an air preheater. Via a fan (IDF: Induced Draft Fan) 33, an environmental device (an electric dust collector, a desulfurization device, etc., not shown) performs a predetermined treatment, is led to a chimney (not shown), and is discharged to the outside air. be. The air sent from the primary air ventilator 31 heated by the combustion gas in the heat exchanger 34 is supplied to the hot gas flow path 30a described above.
The feed water to each heat exchanger of the boiler 200 is heated in an 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. , is sent to a steam turbine (not shown), which is a power generation unit, to rotationally drive the steam turbine, and to rotationally drive a generator (not shown) connected to the steam turbine to generate power, forming the power plant 1. .

Next, the details of the rotary classifier 16 will be described. In the following description, "circumferential direction" and "radial direction" mean "circumferential direction" and "radial direction" when the central axis C is the center.

The rotary classifier 16 is provided on the top of the housing 11, as shown in FIG. As shown in FIG. 2, the rotary classifier 16 rotates around a central axis C extending vertically. In this embodiment, the rotary classifier 16 rotates clockwise when viewed from above, as indicated by an arrow A1 in FIGS. 2 and 3 . The direction of rotation of the rotary classifier 16 is opposite to the swirling direction of the primary air formed by swirl vanes installed at the outlet. The rotary classifier 16 is provided with a rotational driving force by a motor (not shown). The number of rotations of the motor is controlled by the controller 50 .

As shown in FIG. 2, the rotary classifier 16 has a main body 70 having a hollow, substantially inverted conical outer shape. An inner space S1 is formed inside the body portion 70 . The body portion 70 includes a cylindrical shaft 71 covering the fuel supply portion 17 and extending along the center axis C, an upper end portion 72 radially extending from the upper end of the cylindrical shaft 71, and a radially extending portion extending from the lower end of the cylindrical shaft 71. and a lower end portion 73 extending to the . The upper end portion 72 defines the upper end of the inner space S1. Further, the lower end portion 73 defines the lower end of the inner space S1.

In addition, the rotary classifier 16 has a plurality of blades 60 provided on the outer circumference of the main body 70 . Each blade 60 extends vertically. Each blade 60 is a plate-like member. Each blade 60 has its upper end fixed to the upper end 72 . Each blade 60 has a lower end fixed to the lower end portion 73 . Each blade 60 is inclined such that the lower end side is closer to the central axis C than the upper end side. The upper end portion 72 is formed with an opening 72a to which the outlet port 19 (see FIG. 1) is connected.

As shown in FIG. 3, the plurality of blades 60 are arranged in parallel around the central axis C of the rotary classifier 16 at predetermined intervals (equal intervals). Specifically, the blades 60 are arranged side by side on a virtual circle V centered on the central axis C at predetermined intervals. Further, each blade 60 is arranged so as to be inclined at a predetermined angle with respect to the radial direction when viewed from above. A gap is formed between the blades 60 adjacent in the circumferential direction. The gap communicates the inner space S<b>1 of the plurality of blades 60 and the outer space S<b>2 of the blades 60 . Pulverized fuel is directed to each blade 60 with primary air directed radially from the outside to the inside.

Each blade 60 has an impact surface 61 that is the surface on the front side in the rotational direction and a back surface 65 that is the surface on the rear side in the rotational direction.
As shown in FIG. 3 , pulverized fuel including finely powdered fuel B2 and coarsely powdered fuel B1 collides with the collision surface 61 . The pulverized fuel that has collided with the collision surface 61 is subjected to a radially outward force (centrifugal force and collision force, hereinafter referred to as an outward force) indicated by an arrow A2 and a radially inward force indicated by an arrow A3. (centripetal force due to primary air flow, hereinafter referred to as inward force) acts. Since the coarse fuel B1 has a large weight, a strong outward force A2 acts on the coarse fuel B1 that has collided with the collision surface 61 due to the centrifugal force. As a result, the coarse fuel powder B1 is repelled to the outside of the blade 60 (outer space S2 side) as indicated by the arrow A4 against the inward force A3. On the other hand, since the pulverized fuel B2 has a small weight, the centrifugal force acting on the pulverized fuel B2 that collides with the collision surface 61 is relatively weak. As a result, the force acting on the pulverized fuel B2 is dominated by the inward force indicated by the arrow A3. be guided.
The rotary classifier 16 classifies the coarse fuel B1 and the fine fuel B2 based on this principle.

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

As shown in FIG. 4, each blade 60 has an impact surface 61 and a back surface 65 opposite impact surface 61, as described above.
The rear surface 65 is a flat surface.

The collision surface 61 has a curved surface 62 arranged radially outward and a flat surface 63 arranged radially inward of 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 radial center of the collision surface 61 .

The curved surface 62 is provided outside the boundary point D in the radial direction. The curved surface 62 is curved so as to protrude forward in the direction of rotation (see arrow A1 in FIG. 3). The curved surface 62 is curved such that the thickness of the curved surface 62 decreases from the boundary point D toward the outside in the radial direction. Specifically, the curved surface 62 is curved such that the plate thickness is zero at the radially outer end of the blade 60 . That is, the curved surface 62 and the back surface 65 are connected at the radially outer end of the blade 60 . By configuring in this manner, the radial outer end of the blade 60 forms an acute angle. Therefore, the outer end of the blade 60 in the radial direction may be covered with a cover or the like to prevent cuts.

In addition, the curved surface 62 has an angle formed between the tangent line L1 of the virtual circle V and the perpendicular line L2 to the collision surface 61 (hereinafter referred to as "inclination angle θ") more than the radially inner side of the curved surface 62. ) is large. That is, as shown in FIG. 4, the curved surface 62 is curved such that the inclination angle .theta.3 at the point P3 radially outside the point P2 is larger than the inclination angle .theta.2 at the point P2.
The curved surface shape of the curved surface 62 is determined according to the required classification characteristics. For example, as described in the present embodiment, the curved surface shape of the curved surface 62 has the largest curvature radius at the connection portion with the flat surface 63, and the farther from the flat surface 63 (the radially outward), the larger the curvature radius. The curved surface 62 may have a constant curvature, although a shape with a small .DELTA. Further, for example, the shape may be an arc shape, a shape of a part of an ellipse, or a parabolic shape. The classification characteristic is an index indicating how difficult it is for the pulverized fuel to pass (repelled by the outer peripheral side of the blade 60), and the value increases as the passage becomes more difficult.

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

It should be noted that the virtual circle V is a virtual circle centered on the central axis C, and is also a rotational trajectory of an arbitrary point within the airfoil cross section of the blade 60 .

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

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

First, the passage characteristics of the flat blade 60X at each position in the radial direction of the blade 60X indicated by G4 in FIG. 17 are obtained. The passing characteristic is an index indicating how easily pulverized fuel passes through the classifier (a value that increases as it easily passes through the inner peripheral side of the blade 60), and will be described later in detail.
FIG. 17 shows the relationship between each radial position (horizontal axis) of the blade 60X, the outward force acting on the pulverized fuel (left vertical axis), and the passage characteristics of the pulverized fuel (right vertical axis). . The horizontal axis of the graph in FIG. 17 indicates the distance from the inlet (outer end in the radial direction) of the blade 60X. That is, the horizontal axis represents the radial position of the blade 60X, the left end of the horizontal axis represents the radial outer end of the blade 60X (the outer end of the blade 60X on the outer space S2 side), and the right end represents the diameter of the blade 60X. The inner end of the direction (the outer end of the blade 60X on the inner space S1 side) is shown. In addition, the outward force acting on the pulverized fuel includes a force due to centrifugal force and a force due to collision. The passage characteristic is positively correlated with the inward forces acting on the pulverized fuel, ie negatively correlated with the outward forces (centrifugal force + impact force).

G1 in FIG. 17 indicates the outward force F3 (see FIG. 16) acting on the pulverized fuel when the pulverized fuel collides with the blade 60X. G2 also indicates the outward force F5 (see FIG. 16) exerted by the centrifugal force acting on the pulverized fuel. The outward force F3 acting on the pulverized fuel due to collision and the outward force F5 due to the centrifugal force acting on the pulverized fuel are obtained as follows.

As shown in FIG. 15, when the pulverized fuel containing the finely divided fuel B2 and the coarsely divided fuel B1 collides with the blade 60X having a flat plate shape, the coarsely divided fuel B1 travels outside the blade 60X (outside space S2 side). On the other hand, the pulverized fuel B2 is repelled to the inside of the blade 60X (toward the inner space S1) as indicated by an arrow A7.

As shown in FIG. 16, the force with which the pulverized fuel collides with the rotating blades 60X is indicated by an arrow F1. The force indicated by the arrow F1 is decomposed into a force (arrow F2) acting perpendicularly to the collision surface of the blade 60X and a force (arrow F3) acting in parallel along the collision surface of the blade 60X. The force acting in the vertical direction is canceled by the vertical force (arrow F4) from the blade 60X. Since no counteracting force acts on the force acting in parallel, the outward force F3 of the blade 60X acts on the colliding pulverized fuel. That is, an outward force F3 due to the collision acts.
In FIG. 16, the arrow F5 indicates the radial outward force along the collision surface of the blade 60X due to the centrifugal force, and the arrow F6 indicates the radial inner force along the collision surface of the blade 60X due to the primary air flow. indicates a directional force. The outward force F3 is obtained by the following formula (1).

[Number 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 ) Note that the frictional force generated between the pulverized fuel and the blade 60X is small compared to the other forces under the operating conditions of the actual machine, so it is ignored in the calculation.

Thus, the outward force F5 of the blade 60X acts as the inclination of the blade 60X with respect to the radial direction increases. Also, the blade 60X is flat. Therefore, in the blade 60X, the angle θ is constant at any point in the radial direction. Therefore, as indicated by G1 in FIG. 17, the blade 60X has a constant outward force F5 at any point in the radial direction.

Also, the pulverized fuel that has collided with the blade 60X is given a centrifugal force F5 by the blade 60X. Centrifugal force F5 is obtained from the following equation (2).

[Number 2]
F5=m×r×ω ² (2)
where m: mass of pulverized fuel r: radius of rotation at collision position ω: angular velocity of blade 60X

Therefore, the centrifugal force F5 acting on the pulverized fuel colliding with the blade 60X with the same rotational speed is determined by the mass of the pulverized fuel and the radius of rotation of the collision position.
Further, the pulverized fuel B2 has a small mass. Further, as will be described later, the pulverized fuel B2 collides with the inner side of the blade 60X in the radial direction, that is, the point where the radius of rotation is small, so the centrifugal force F5 acting on the pulverized fuel B2 is reduced. Therefore, when the radially inward force F7 due to the primary air flow overcomes the centrifugal force F5, the pulverized fuel B2 moves radially inward of the blade 60X.
On the other hand, the coarse fuel B1 has a large mass. In addition, as will be described later, the coarse fuel particle B1 collides with the radially outer side of the blade 60X, that is, a portion having a large rotation radius, so the centrifugal force F5 acting on the coarse fuel particle B1 increases. Therefore, when the centrifugal force F5 overcomes the radially inward force F6 due to the primary air flow, the coarse fuel powder B1 is repelled radially outward of the blade 60X.
From the above, as indicated by G2 in FIG. 17, the force due to the centrifugal force F5 becomes a linear function, and thus becomes a straight line that slopes downward to the right.

In addition, G3 in FIG. 17 indicates the outward force resulting from the sum of the outward force F5 due to the centrifugal force and the outward force F3 due to collision. As described above, if the blade 60X is flat, the outward force F3 due to collision is constant. Therefore, as shown in G3 in FIG. 17, the outward force (centrifugal force + collision force) becomes a straight line.

The passing characteristic indicated by G4 in FIG. 17 is in an inversely proportional relationship (negative correlation) with the outward force (centrifugal force+collision force). Therefore, as shown by G4, the passing characteristic is a straight line that slopes upward to the right, the slope of which is opposite to that of G3, which indicates the outward force (centrifugal force + collision force).
In this way, the passing characteristics of the plate-shaped blade 60X are obtained.

Here, the passing characteristic shown in FIG. 17 indicates the mass of a single pulverized fuel that can pass. Given that the density of pulverized fuel is constant, this indicates the volume of pulverized fuel, that is, the size of pulverized fuel. Therefore, as indicated 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 indicated by G4 in FIG. 17, the passage characteristic is proportional to the distance from the outer end side of the blade 60X. Therefore, as indicated by G5b in FIG. 18B, the size of the passing pulverized fuel 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 pulverized fuel passing through blade 60X and passage characteristics. FIG. 18B is a graph showing the relationship between the size of pulverized fuel passing through blade 60X and the distance from the inlet of blade 60X.

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

As shown in FIG. 19, the airflow E reaching the side surface of the blade 60X sharply bends toward the flow path between the adjacent blades 60X. At this time, the pulverized fuel B2, which has a light mass and a small inertia, tends to change course along with the airflow E. On the other hand, the course of the coarse fuel B1, which has a heavy mass and a large inertia, is difficult to change. Due to this characteristic, as shown in FIG. 19, the finely divided fuel B2 passes through the inner side of the airflow curve, and the coarsely powdered fuel B1 passes through the outer side of the airflow curve, whereby rough classification by the airflow is performed. . As a result of the rough classification, the proportion of the finely divided fuel B2 colliding with the exit side (inside in the radial direction) of the blade 60X and the proportion of the coarsely divided fuel B1 colliding with the inlet side (outside in the radial direction) of the blade 60X increases. 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 of F (force)=m (mass)·a (acceleration), when the same fluid force is applied from the primary air stream, lighter particles (pulverized fuel B2) generate greater acceleration. Further, since the movement distance of an object given a constant acceleration is X=a (acceleration) t (time) ² , the distribution of particles colliding with the blade 60X is approximately quadratic as shown in FIG. It becomes a curved distribution close to a function. FIG. 20 is a graph showing the relationship between the particle size of 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 begins to change direction toward the blade 60X depends on the flight trajectory of the particles, this variation results in a broad distribution with a certain width. Thus, the size of the pulverized fuel particles colliding with each position in the radial direction of the blade 60X (hereinafter referred to as "impingement particle size distribution") falls within the hatched range in FIG. In the above description, the case of colliding with the flat blade 60X has been described, but the size of the pulverized fuel particles colliding with the blade does not change depending on the shape of the blade. Therefore, for example, even when colliding with the blade 60 provided with the curved surface 62 described in this embodiment, the colliding particle size distribution becomes the distribution shown in FIG.

Next, with reference to FIG. 21, passage characteristics of the entire rotary classifier 16 provided with flat blades 60X (that is, classification performance of the rotary classifier 16) will be described. 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. Also, the horizontal axis indicates the distance from the entrance (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 blades 60X indicated by G5b in FIG. 18B and the pulverized fuel distribution shown in FIG. In FIG. 21, the target particle size of the rotary classifier 16 is the particle size of the pulverized fuel at which G5b, which indicates the size of the pulverized fuel passing through the blade 60X, and the upper edge line of the collision particle size distribution intersect. The target particle size is the upper limit of the particle size of pulverized fuel that is to be passed through the rotary classifier 16 and discharged from the mill 10 (supplied to the burner 220 of the boiler 200).

In FIG. 21, the area below G5b, which indicates the size of the crushed fuel passing through the upper edge line of the collision particle size distribution and the blade 60X, is the region of the crushed fuel passing through the rotary classifier 16. That is, the area below the dashed line G6 is the area of the pulverized fuel that passes through the rotary classifier 16. As shown in FIG. Passage characteristics are relatively low on the blade inlet side (outer end side) where coarse fuel is abundant (that is, it is difficult to pass), and conversely, passage characteristics on the blade exit side (inner end side) where fine powder fuel is abundant are relatively high. (i.e. easier to pass). As a result, the fine fuel can be allowed to pass through while the coarse fuel is not allowed to pass through. Therefore, the effect of classification can be obtained efficiently.

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

As shown in FIG. 22 , even when pulverized fuel containing finely powdered fuel B2 and coarsely powdered fuel B1 collides with the blade 60Y in the form of a folded plate, the coarsely powdered fuel B1 travels toward the outside of the blade 60Y as indicated by an arrow A8. (Outer space S2 side). On the other hand, the pulverized fuel B2 is repelled to the inside of the blade 60Y (toward the inner space S1) as indicated by an arrow A9.

The outer portion 60Ya and the inner portion 60Yb of the blade 60Y have different angles of inclination with respect to the radial direction. This means that the direction of the impact force of the pulverized fuel colliding with the blade 60Y is different. Therefore, the outward force acting on the pulverized fuel that collides with the inner portion 60Yb with a small inclination angle (the force calculated by the above formula (1); see F3 in FIG. 16) is small, and the outer portion 60Ya with a large inclination angle The outward force acting on the colliding particles will be large.

Therefore, as indicated by G7 in FIG. 23, the outer portion 60Ya of the blade 60Y has a greater outward force due to the impact force, and the inner portion 60Yb has a smaller outward force due to the impact force. Note that G2 in FIG. 23 indicates the outward force due to the centrifugal force acting on the pulverized fuel, as in FIG. G8 indicates an outward force resulting from the sum of the outward force due to the centrifugal force and the outward force due to the collision force. As shown in G7, since the outward force due to the collision force changes greatly at the break point H, G8 also changes greatly at the break point H. In the following description, a portion where the outward force changes greatly is called a "stepped portion". Also, the passing characteristic indicated by G9 in FIG. 23 is in an inversely proportional relationship (negative correlation) with the outward force (centrifugal force+collision force). In addition, hatched K1 in FIG. 23 indicates a region where passage characteristics can be reduced as compared with the flat blade 60X. In this way, in the outer portion 60Ya where the coarse fuel particles B1 are likely to collide, the passage characteristics (inward force) can be reduced. know that you can.

Next, using FIG. 24, the passage characteristics of the rotary classifier 16 as a whole (that is, the classification performance of the rotary classifier 16) provided with the folded-plate blades 60Y will be described. The passage characteristics of the entire rotary classifier 16 in this description are derived from G10, which indicates the size of pulverized fuel passing through the blade 60Y based on G9 in FIG. 23, and the impact particle size distribution shown in FIG. be

In FIG. 24 , the area below G11 indicated by the dashed line is the area of pulverized fuel passing through the rotary classifier 16 . As indicated by hatching K2, the passage characteristics of the outer portion 60Ya are reduced compared to when the flat blade 60X is employed. In addition, the passage characteristics are extremely reduced in a region where the particle size is large, particularly in a region where the proportion of particles having a particle size equal to or smaller than the target particle size is very small. As a result, it is possible to suppress the passage of coarse fuel particles and improve the classification performance.
On the other hand, the hatched area K3 is repelled to the outer peripheral side by the blade 60Y even though it is within the range of the collision particle size distribution and is equal to or smaller than the target particle size. Therefore, it can be seen that the classification performance is lower than when the flat blade 60X is used (the pulverized fuel that should be passed and does not need to be classified is repelled to the outer peripheral side).
Further, there is a stepped portion in the classification characteristics, and whether or not the pulverized fuel in the particle size range J corresponding to the stepped portion passes through the blade 60Y depends on the collision position. Therefore, whether or not the particles are classified is random with respect to the particle diameter. Therefore, there is a problem that part of the pulverized fuel that should pass through the rotary classifier 16 is repelled by the blade 60Y, and the classification performance deteriorates.
The repelled pulverized fuel is returned to the pulverizing table 12 and pulverized again. Since the pulverized fuel, which has already become finer, is further pulverized, the pulverization power is wasted, and the pulverized fuel that has flowed back acts as a solid lubricant, causing the pulverizing rollers 13 to slip on the pulverizing table 12, causing slip vibration. is likely to occur in the mill 10.

Next, the classification performance of the rotary classifier 16 having the blade 60 having the curved surface 62 according to this embodiment will be described with reference to FIGS. 5 and 6. FIG. In this description, an example in which the angle of inclination of the flat surface 63 is the same as the angle of inclination of the blade 60X described above will be described.
In the curved surface 62, it can be assumed that the inclination angle changes continuously. Therefore, as indicated by G20 in FIG. 5, the outward force due to the collision force also changes smoothly. Specifically, the curved surface 62 has a larger inclination angle on the radially outer side than on the radially inner side. Therefore, the outward force due to the collision force increases toward the outside in the radial direction. In addition, G21, which 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, also changes smoothly so that the outward force increases toward the outside in the radial direction. is doing. Note that G2 in FIG. 5 indicates the outward force due to the centrifugal force acting on the pulverized fuel, as in FIG. 17 and the like. Also, the passing characteristic indicated by G22 in FIG. 5 is in an inversely proportional relationship (negative correlation) with the outward force (centrifugal force+collision force). Therefore, like G21, G22 also changes smoothly. Further, the hatched K4 in FIG. 5 indicates a region where the passing characteristic can be reduced more than the plate-shaped blade 60X. In this way, since the passing characteristic (inward force) can be reduced on the radially outer side where the coarse fuel particles B1 tend to collide, the situation where the coarse fuel particles B1 pass through more than the flat blade 60X can be prevented. It turns out that it can be suppressed.

Next, using FIG. 6, the passage characteristics of the entire rotary classifier 16 having the blades 60 according to the present embodiment (that is, the classification performance of the rotary classifier 16) will be described. The passage characteristics of the entire rotary classifier 16 in this description are derived from G23, which indicates the size of the pulverized fuel passing through the blades 60 based on G22 in FIG. 5, and the impact particle size distribution shown in FIG. be

In FIG. 6, the area below the dashed line G24 is the region of the pulverized fuel passing through the rotary classifier 16. As shown in FIG. As indicated by hatchings K5 and K6, the passage characteristics are reduced on the curved surface 62 compared to when the flat blade 60X is employed. In addition, as shown by hatching K6, the passage characteristics of the curved surface 62 are smaller than when the folded plate blade 60Y is employed. In addition, the passage characteristics are extremely reduced in a region where the particle size is large, particularly in a region where the proportion of particles having a particle size equal to or smaller than the target particle size is very small. As a result, it is possible to further suppress the passage of coarse fuel particles and improve the classification performance.
By suppressing passage of coarse fuel particles in this way, it is possible to suppress supply of coarse fuel particles having a target particle size or more to the burner 220 . As a result, the amount of pulverized fuel that is not completely burned in the burner 220 (unburned pulverized fuel) can be reduced, and the unburned content in the ash discharged from the boiler 200 can be reduced. Moreover, since the unburned content in the ash can be reduced, the amount of air supplied to the boiler 200 can be reduced (low air ratio combustion), and the amount of nitrogen oxides produced can also be suppressed. Therefore, the environmental load can be reduced. In addition, the amount of reducing agent (such as ammonia) used in the denitrification device 35 can be reduced, and the running cost can be reduced.

On the other hand, the hatched area K7 is repelled to the outer peripheral side by the blade 60Y even though it is within the collision particle size distribution range and is equal to or smaller than the target particle size. The area where the classification performance is lowered can be made smaller than when the folded-plate blade 60Y is employed (see hatching K3 in FIG. 24). Therefore, deterioration in classification performance can be suppressed.
By suppressing the recirculation of the finely divided fuel B2 in this way, it is possible to suppress the re-pulverization of the finely divided fuel B2. Thereby, reduction of the grinding|pulverization power of the mill 10 can be aimed at. In addition, slip vibration of the mill 10 due to the recirculated pulverized fuel acting as a lubricant can be made less likely to occur.

In addition, by adopting a structure in which the angle of inclination is changed by the curved surface 62, the stepped portion that occurs when the folded-plate-shaped blade 60Y is adopted is eliminated. As a result, it is possible to eliminate the region where whether or not the particles are classified is random with respect to the particle size, so that the classification performance can be improved.

In this embodiment, in addition to the improvement in the classification performance described above, the following effects are obtained.
In this embodiment, a curved surface 62 is formed on the radially outer side of the blade 60 . With such a curved tip blade 60, even if the blade 60 wears due to collision with pulverized fuel during use of the rotary classifier 16, the curved shape is generally maintained. In other words, the blade 60 with a curved tip surface can have a self-shaping property in which the blade 60 wears so that the radial length of the blade 60 decreases. This is because the outer side of the blade 60 tends to be rougher and heavier particles collide with each other at high speed, and wear tends to be accelerated. The curved surface shape of the curved surface 62 of 60 is maintained, and its performance can be maintained.

Further, in this embodiment, the collision surface 61 has a curved surface 62 and a flat surface 63 . Since the flat surface 63 is easier to manufacture than the curved surface 62 , the blade 60 can be manufactured more easily than when the entire impact surface 61 is the curved surface 62 .
In general, the radially inner side of the collision surface 61 is affected by the force of the primary air (that is, the force directed from the radially outer side to the inner side of the blade 60). The effect of the force directed toward the In this embodiment, a flat surface 63 is formed on the inner side in the radial direction. Thereby, compared with the case where the flat surface 63 is formed on the outer side in the radial direction, deterioration of the classification performance can be suppressed.
A boundary point D, which is a boundary between the curved surface 62 and the flat surface 63, is a point where G23, which indicates the size of pulverized fuel passing through the blade 60 in FIG. It may be radially inside of L. 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. can be done.

In addition, in this embodiment, the length of the blade 60 in the circumferential direction (the length in the plate thickness direction) becomes shorter toward the outer side in the radial direction. As a result, since the plate thickness of the blade 60 can be reduced, it is possible to make it difficult for a tool or the like to interfere with an adjacent blade or the like when the blade 60 is attached. Therefore, the attachment work of the blade 60 can be facilitated.

It should be noted that the present disclosure is not limited to the above-described embodiments, and modifications can be made as appropriate without departing from the scope of the present disclosure.
For example, in the above-described embodiment, the mill of the present disclosure is used, but the solid fuel may be biomass fuel or PC (petroleum coke) fuel generated during petroleum refining. may be used.

Also, in the above embodiment, an example in which the classifier of the present disclosure is applied to a mill that pulverizes solid fuel has been described, but the present disclosure is not limited to this. For example, the classifier of the present disclosure may be applied to crushers that crush ores.

In addition, the radial length of the blade 60 decreases as it wears. For this reason, it is desirable to set the replacement reference by the length in the radial direction. Along with this, the blade 60 may be provided with detection means for detecting the length in the radial direction, and this detection means may be used as a wear detection sensor.

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. may It is desirable that the flat surface 63 of the blade 60 is provided with the mounting surface and the bolt bearing surface that are attached to the body portion 70 , but the curved surface 62 may be provided with the mounting surface or the like. When a mounting surface or the like is provided on the curved surface 62, a counterbore or the like may be provided, or a washer or the like matching the curvature may be used to form the seat surface.

[Modified example of blade]
Also, the present disclosure is not limited to the shapes of the blades 60 described above. Modifications of the blade 60 will be described below with reference to the drawings.

[Modification 1]
As shown in FIG. 7, the blade may be manufactured by laminating a plurality of thin plates in the plate thickness direction. The blade 60A is formed by stacking thin plate materials (60Aa, 60Ab, and 60Ac) having different lengths in the radial direction. Each plate member may be made of the same material, or may be made of different materials. In the case of forming with different materials, the plate members may be arranged so that the plate members are formed of a material having high wear resistance in order from the collision surface 61 side to the back surface 65 side. By doing so, the self-shaping property can be exhibited more preferably.

[Modification 2]
Further, as shown in FIG. 8, the blade may have a constant length (thickness) in the circumferential direction throughout the radial direction. A curved surface 62 is formed on the collision surface 61 of the blade 60B by bending a plate-like blade. As described above, in this modified example, the blade 60B having a curved surface can be formed simply by bending, so that the blade 60B can be easily manufactured.
In addition, since the circumferential length (thickness) of the blade 60B is constant throughout the radial direction, the length that allows wear is increased throughout the radial direction. Therefore, the durability of the blade 60B can be improved.

[Modification 3]
Also, as shown in FIG. 9, the blade may have a plurality of recesses 80 formed in the curved surface 62 . The blade 60</b>C has a constant circumferential length (plate thickness) throughout the radial direction, and a plurality of concave portions 80 are formed in the curved surface 62 . Examples of the recesses 80 include, for example, dimples.
The blade 60</b>C has a self-lining structure with a plurality of recesses 80 . The recess 80 is formed to have a sufficiently small radius of curvature compared to the radius of curvature of the curved surface 62 . That is, the recessed portion 80 has a size that does not affect the shape of the curved surface 62 . Specifically, for example, when the radius of curvature R of the curved surface 62 is 100, and the radius of curvature R of the concave portion 80 is about 10 or less, the shape of the curved surface 62 is largely unaffected.
In the self-lining structure, recesses 80 are formed in the curved surface 62 so that pulverized fuel enters the recesses 80 . Thereby, the surface of the curved surface 62 is covered with pulverized fuel. The pulverized fuel covering the surface of the curved surface 62 suppresses contact between the flowing pulverized fuel and the curved surface 62 . Therefore, abrasion of the curved surface 62 can be suppressed.
A similar effect can be obtained by forming waves instead of the concave portions 80 .
Further, the concave portion 80 or the corrugations may be provided not only on the curved surface 62 but also on the flat surface 63, and by providing them on the collision surface 61, abrasion can be suppressed.

[Modification 4]
Further, in the above 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 to this. 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 at the upper portion of the blade 60D (see FIG. 11) and the cross-sectional shape at the lower portion (see FIG. 12) may be different. Specifically, in the example shown in FIG. 10, the upper section of the blade 60D has a smaller curved surface than the lower section of the blade 60D. This is because, as shown in FIG. 2, etc., the blade 60D is inclined so that the upper part is further away from the central axis C than the lower part, so the centrifugal force R1 (see FIG. 2) acting on the upper part moves to the lower part. This is because it is greater than the acting centrifugal force R2 (see FIG. 2). In the upper portion where the centrifugal force acting is strong, even if the curved surface 62 is made small to make it difficult to repel the pulverized fuel radially outward, it is possible to sufficiently repel the pulverized fuel radially outward. On the other hand, at the lower portion where the centrifugal force acting is weak, the pulverized fuel can be sufficiently repelled radially outward by enlarging the curved surface 62 to facilitate repulsion radially outward. Therefore, in the example shown in FIG. 10, even if the blade 60D is inclined with respect to the vertical direction, the manner in which the pulverized fuel is repelled radially outward can be made uniform in the vertical direction.

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 it is not inclined), the centrifugal force R3 acting on the blade 60E is Since it does not change in the vertical direction, it may have a uniform shape in the vertical direction as shown in FIG. By making the shape uniform in the vertical direction, the structure can be simplified, so that it can be easily manufactured.

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

In addition, the curved surface 62 may not be a perfect curved surface, but may be formed by digitally forming a curved surface by combining planes with minute differences in angles, or by combining thin layers stepwise. Further, depending on the required classification performance, a flat surface may be inserted at the tip of the curved surface 62 or part of the middle of the curved surface 62 .

The classifier, the power plant, and the method of operating the classifier according to the embodiments described above are grasped, for example, as follows.
A classifier according to an aspect of the present disclosure is a classifier (16) that classifies particles guided together with a carrier gas into the particles larger than a predetermined particle size and the particles having a predetermined particle size or less, The carrier gas extends in the vertical direction, is arranged in the circumferential direction on a virtual circle (V) centered on the central axis (C) extending in the vertical direction, and flows from the outer side to the inner side in the radial direction. and a plurality of blades (60) through which the particles are guided, the blades (60) colliding with the guided particles, and removing the particles larger than a predetermined particle diameter among the colliding particles with the particle diameter It has a collision surface (61) that repels the particles of a predetermined particle size or less in the radially outward direction, and the collision surface (61) has a radially outer side that faces the The angle formed by the tangent to the virtual circle (V) and the perpendicular to the collision surface (61) is larger than the radially inner side.

In general, the classifier blades are more likely to collide with pulverized solid fuel having a larger particle size (hereinafter referred to as "pulverized fuel") toward the outer side in the radial direction, and pulverized solid fuel having a smaller particle size toward the inner side in the radial direction. Fuel tends to collide easily. Further, the greater the angle formed by the tangent to the virtual circle and the perpendicular to the collision surface (hereinafter referred to as the "tilt angle"), the more strongly the pulverized fuel is repelled radially outward.
In the above configuration, the collision surface of the blade has a larger inclination angle on the radially outer side than on the radially inner side. That is, the shape has a strong force that repels the pulverized fuel radially outward at the radially outer side where the pulverized fuel having a large particle size tends to collide. Therefore, pulverized fuel having a large particle size can be strongly repelled radially outward. On the other hand, the collision surface of the blade has a larger inclination angle on the radially inner side than on the radially outer side. That is, the shape is such that the force for repelling the pulverized fuel to the radially outer side is weak at the radially inner side where the pulverized fuel having a small particle size tends to collide. Therefore, the pulverized fuel having a small particle size is easily guided radially inward together with the carrier gas flowing radially inward. As a result, the pulverized fuel having a small particle size can be repelled radially inward.
In this manner, pulverized fuel having a large particle size is easily repelled radially outward, and pulverized fuel having a small particle size is easily repelled radially inward, so that the classification performance of the classifier can be improved.

Further, in the classifier according to an 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) extends outward in the radial direction. The angle formed by the tangent to the virtual circle (V) and the perpendicular to the collision surface (61) is larger on the inner side in the radial direction.

For example, if the blade has a folded plate shape in which flat plate-shaped outer and inner portions with different inclination angles are connected, the pulverized fuel collides with the outer portion according to the intrusion position of the pulverized fuel. will determine whether the pulverized fuel hits the inner portion and is repelled to the inside of the blade. For this reason, even pulverized fuel with the same particle size may be classified (repelled to the outside) or not classified (repelled to the outside) depending on the entry position. Therefore, there was a possibility that the classification performance would deteriorate.
On the other hand, in the above configuration, the collision surface is curved. This can reduce the area dependent on the intrusion position. Therefore, the classification performance can be improved.

Further, in the above configuration, the curved surface of the blade has a larger inclination angle on the radially outer side than on the radially inner side. That is, the shape has a strong force that repels the pulverized fuel radially outward at the radially outer side where the pulverized fuel having a large particle size tends to collide. Therefore, pulverized fuel having a large particle size can be strongly repelled radially outward. On the other hand, the curved surface of the blade has a greater angle of inclination on the radially inner side than on the radially outer side. That is, the shape is such that the force for repelling the pulverized fuel to the radially outer side is weak at the radially inner side where the pulverized fuel having a small particle size tends to collide. Therefore, the pulverized fuel having a small particle size is easily guided radially inward together with the carrier gas flowing radially inward. As a result, the pulverized fuel having a small particle size can be repelled radially inward.
In this way, on the curved surface, pulverized fuel with a large particle size is easily flipped radially outward, and pulverized fuel with a small particle size is easily flipped radially inward, so that the classification performance of the classifier can be improved. .

It should be noted that the curved surface includes a polygonal surface formed by combining planes with a small angle difference, and a stepped surface formed by laminating thin layers with their edges shifted.

Further, in the classifier according to an aspect of the present disclosure, the collision surface (61) includes the curved surface (62) and a flat surface (63) arranged inside the curved surface (62) in the radial direction. ) and

In the above configuration, the collision surface has a curved surface and a flat surface. Since a flat surface is easier to manufacture than a curved surface, the blade can be manufactured more easily than when the entire collision surface is curved.
In general, the influence of the force of the carrier gas (that is, the force directed from the outside to the inside in the radial direction) increases toward the radially inner side of the collision surface. 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 the deterioration of the classification performance due to the formation of the flat surface.

In addition, in the classifier according to one aspect of the present disclosure, the blade (60) has a length in the circumferential direction that decreases toward the outer side in the radial direction.

In the above configuration, the length of the blade in the circumferential direction (the length in the plate thickness direction) becomes shorter toward the outer side in the radial direction. As a result, the plate thickness of the blade can be reduced, so that it is difficult for a tool or the like to interfere with an adjacent blade or the like when attaching the blade. Therefore, the work of attaching the blade can be facilitated.

In addition, in the classifier according to one aspect of the present disclosure, the blades (60) have a constant length in the circumferential direction over the entire area in the radial direction.

In the above configuration, the length of the blade in the circumferential direction (the length in the plate thickness direction) is constant throughout the radial direction. Thereby, for example, a blade having a curved surface can be manufactured by bending a plate-like blade. Therefore, the blade can be manufactured easily.
In addition, since the length of the blade in the circumferential direction (the length in the plate thickness direction) is constant throughout the radial direction, the length that allows wear is longer. Therefore, durability of the blade can be improved.

Further, in the classifier according to one aspect of the present disclosure, the collision surface (61) is formed with a plurality of concave portions.

In the above configuration, a plurality of recesses are formed on the collision surface. That is, the self-lining structure is configured by the plurality of recesses. As a result, the pulverized fuel enters the concave portion and covers the surface of the collision surface with the pulverized fuel. The pulverized fuel covering the surface of the collision surface suppresses contact between the flowing pulverized fuel and the collision surface. Therefore, abrasion of the collision surface can be suppressed.

Further, a power plant according to an aspect of the present disclosure includes a classifier (16) according to any one of the above, and a pulverized solid fuel having a predetermined particle size or less classified by the classifier (16). It comprises a boiler (200) and a power generation section that generates power using the steam generated by the boiler (200).

Further, a classifier operating method according to an aspect of the present disclosure includes a classifier (16 ), wherein the classifiers (16) extend vertically and are arranged circumferentially on a virtual circle (V) centered on the central axis extending vertically. and a plurality of blades (60) through which the particles are guided along with the carrier gas directed radially inward from the outer side, the blades (60) colliding with the guided particles and Among them, it has a collision surface (61) that repels the particles larger than a predetermined particle diameter outward in the radial direction and repels the particles smaller than the predetermined particle diameter inward in the radial direction, and the collision surface (61 ), the angle formed by the tangent of the virtual circle (V) and the perpendicular to the collision surface (61) is larger on the radially outer side than on the radially inner side, and the blade (60) and classifying the particles into the particles larger than a predetermined particle diameter and the particles having a predetermined particle diameter or less.

Reference Signs List 1: power plant 10: mill 11: housing 12: grinding table 13: grinding 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 : Conveyor 23 : Coal feeder motor 24 : Downspout 30 : Air blower 30a : Hot gas flow path 30b : Cold gas flow path 30c : Hot gas damper 30d : Cold gas damper 31 : Primary air ventilator 32 : Pushing Ventilator 34 : Heat exchanger 35 : Denitrification device 36 : Flue 40 : State detection part 41 : Bottom part 42 : Ceiling part 45 : Journal head 47 : Support arm 48 : Support shaft 49 : Pressing device 50 : Control part 60 : Blade 61 : Collision surface 62 : Curved surface 63 : Flat surface 65 : Back surface 70 : Main body 71 : Cylindrical shaft 72 : Upper end 73 : Lower end 80 : Recess 100 : Solid fuel crusher 100a : Primary air flow path 100b : Fine powder Fuel supply channel 200: Boiler 210: Furnace 220: Burner

Claims

A classifier for classifying particles guided together with a carrier gas into the particles larger than a predetermined particle diameter and the particles having a predetermined particle diameter or less,
The particles are arranged side by side in the circumferential direction on an imaginary circle extending in the vertical direction and centered on the central axis line extending in the vertical direction, and the particles are guided along with the carrier gas directed radially inward from the outer side. with multiple blades,
The blade collides with the guided particles, and among the collided particles, the blade repels the particles larger than a predetermined particle diameter in the radial direction, and removes the particles with a predetermined particle diameter or less in the radial direction. It has a collision surface that bounces inward,
In the classifier, the collision surface has a larger angle between a tangent to the imaginary 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 collision surface has a curved surface that curves so as to protrude,
2. The classifier according to claim 1, wherein said curved surface has a larger angle formed by a tangent to said imaginary circle and a perpendicular to said collision surface on the outer side in the radial direction than on the inner side in the radial direction.
The classifier according to claim 2, wherein the collision surface has the curved surface and a flat surface arranged inside the curved surface in the radial direction.
The classifier according to claim 2 or 3, wherein the blades have a length in the circumferential direction that decreases toward the outer side in the radial direction.
The classifier according to claim 2 or 3, wherein the blade has a constant length in the circumferential direction throughout the radial direction.
The classifier according to any one of claims 1 to 5, wherein the collision surface is formed with a plurality of concave portions.
A classifier according to any one of claims 1 to 6;
A boiler that burns pulverized solid fuel having a predetermined particle size or less classified by the classifier;
and a power generation unit that generates power using the steam generated by the boiler.
A classifier operating method for classifying particles introduced with a carrier gas into particles larger than a predetermined particle size and particles smaller than a predetermined particle size,
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. a plurality of blades through which the particles are directed;
The blade collides with the guided particles, and among the collided particles, the blade repels the particles larger than a predetermined particle diameter in the radial direction, and removes the particles with a predetermined particle diameter or less in the radial direction. It has a collision surface that bounces inward,
the radially outer side of the collision surface has a larger angle formed by a tangent to the imaginary circle and a perpendicular line to the collision surface than the radially inner side;
A method for operating a classifier, comprising the step of classifying the particles into the particles larger than a predetermined particle diameter and the particles having a predetermined particle diameter or less by the blade.