KR102588781B1 - Solid fuel pulverizer and power plant provided with the same, and method for pulverizing solid fuel - Google Patents

Abstract

Provided is a solid fuel grinding device that can supply stable pulverized fuel to a boiler even when biomass fuel is used. It is provided with a rotary table, a grinding roller for grinding biomass fuel, which is a solid fuel, between the rotary table, and a plurality of blades installed upright along a circumferential direction centered on the rotation axis, and the biomass fuel after being pulverized by the grinding roller is provided. A rotary classifier for classifying mass fuel and a control unit for controlling the rotation speed of the rotary classifier are provided, and the control unit controls the rotation speed of the rotary classifier over the operating range of the boiler to which the biomass fuel is supplied after being classified from the rotary classifier. is controlled to be approximately constant.

Description

Solid fuel grinding device, power plant equipped with the same, and solid fuel grinding method {SOLID FUEL PULVERIZER AND POWER PLANT PROVIDED WITH THE SAME, AND METHOD FOR PULVERIZING SOLID FUEL}

The present invention relates to a solid fuel grinding device suitable for grinding biomass fuel, a power plant equipped with the same, and a solid fuel grinding method.

Conventionally, carbon-containing solid fuels such as coal and biomass fuel are pulverized into fine powder smaller than a predetermined particle size using a grinder (mill) and supplied to a combustion device. The mill pulverizes solid fuel such as coal or biomass fuel fed into the rotary table by crushing it into small pieces between the rotary table and rollers, and blows primary air, which is the conveying gas, supplied through a duct from the outer periphery of the rotary table. In this way, the fuel that has been pulverized into fine powder is sorted out in a classifier to have a small particle size, and is returned to the boiler and burned in the combustion device. In a thermal power plant, steam is generated through heat exchange with combustion gas generated by combustion in a boiler, and power generation is performed by driving a turbine with the steam.

When coal is used as a carbon-containing solid fuel, the rotational speed of the rotary classifier is controlled according to the amount of coal supplied or the particle size of the coal, as shown in Patent Documents 1 to 3.

Japanese Patent Publication No. 2001-254930 Japanese Patent Publication No. 2008-232466 Japanese Patent Publication No. 2001-347176

However, as a carbon-containing solid fuel, biomass fuels such as lignocellulosic pellets are difficult to finely grind compared to coal, and on the other hand, they have high combustibility and have the property of being able to burn preferably even with relatively large particle sizes. Therefore, when biomass fuel is used as a solid fuel, it is supplied from the mill to the combustion device provided in the boiler in a particle size that is approximately 5 to 10 times larger than that of coal pulverized fuel.

In this way, since coal and biomass fuel have different particle diameters supplied to the combustion device, mills that perform pulverization and classification of solid fuel have different designs for biomass fuel pulverization and coal pulverization (e.g., It is inherently desirable to individually design the housing (shape of the housing, rotation speed of the rotary table, rotation speed of the rotary classifier, etc.). However, from the viewpoint of equipment cost and installation space, the same mill can handle both biomass fuel and coal solid fuel, and biomass fuel can be produced using a mill that can share both coal and biomass fuel. There is a demand for something that can be used.

The rotary classifier adopts a method of classifying pulverized fuel with a predetermined particle diameter or less between a plurality of rotating blades arranged in a circumferential direction around the central axis of rotation. For this reason, the pulverized biomass fuel has a larger particle diameter compared to the case of pulverizing coal as described above, so it is difficult to pass between the blades and is difficult to be conveyed to the burner, which is a combustion device of a boiler provided on the downstream side. In addition, pulverized biomass fuel tends to accumulate in gaps or air flow stagnation areas inside the mill, and because it has a small specific gravity and is lighter than coal, for example, air flow stagnation occurs inside a rotary classifier, and biomass fuel Even if pulverized fuel deposits in the rotary classifier, it is difficult to remove and discharge the deposits by centrifugal force, and it tends to remain in the rotary classifier and accumulate.

Therefore, the present inventors and others found that when pulverizing biomass fuel, it is effective to control the rotational speed of the rotary classifier using a different way of thinking from that of coal.

The present invention has been made in light of these circumstances, and its purpose is to provide a solid fuel grinding device that can stably supply pulverized fuel to a boiler even when biomass fuel is used, a power plant equipped with the same, and a solid fuel grinding method. do.

A solid fuel grinding device according to one aspect of the present invention includes a rotary table, a grinding roller for grinding biomass fuel between the rotary table, and pulverized biomass obtained by grinding the biomass fuel by the grinding roller. It is provided with a rotary classifier that classifies fuel and selects pulverized biomass fuel, and a control unit that controls the rotation speed of the rotary classifier, wherein the control unit controls the rotary fraction over the operating range of the boiler to which the pulverized biomass fuel is supplied. The rotational speed of the air supply is controlled to be approximately constant.

Pulverized biomass fuel has a larger particle size than pulverized fuel, which is a pulverized fuel derived from coal, and is difficult to pass between the blades of a rotary classifier. In addition, since the pulverized biomass fuel has a small specific gravity and is light, once it enters the rotary classifier and deposits in the area where the airflow of the carrier gas stays, the centrifugal force acting is small, so it accumulates in the rotary classifier and is difficult to discharge. . Therefore, it is difficult to pass through the rotary classifier and be returned and supplied to the downstream boiler. For this reason, as the load on the boiler increases, if the input amount of biomass fuel is increased and the rotation speed of the rotary classifier is also increased, the amount of pulverized fuel supplied from the rotary classifier to the boiler does not increase to suit the load. No. Therefore, even if the load on the boiler increases, by controlling the rotary classifier at an approximately constant rotation speed, pulverized fuel suitable for the increase in the load on the boiler can be supplied. Additionally, since the rotational speed of the rotary classifier can be controlled to be approximately constant, simple control can be realized.

In addition, in the solid fuel grinding device according to one aspect of the present invention, the control unit controls the rotation speed of the rotary classifier to be approximately constant within the range of ±1 rpm.

Because pulverized biomass fuel has a larger particle diameter than pulverized coal, it is difficult to pass between the blades of a rotary classifier, so the rotation speed of the rotary classifier is reduced. In addition, because the pulverized biomass fuel is lightweight, once it enters the rotary classifier and deposits in the area where the airflow of the carrier gas stays, the centrifugal force acting on the pulverized biomass fuel is small, so it accumulates in the rotary classifier and is discharged. It's hard to be. Therefore, the rotation speed of the rotary classifier is reduced, the flow of the carrier gas is not blocked, and an area where the airflow of the carrier gas stays is not created, so that the pulverized biomass fuel pulverized by the carrier gas is sent to the downstream boiler. It can be easily supplied.

At this time, since the median value of the rotation speed of the rotary classifier is, for example, 10 rpm or more and 30 rpm or less, it is good if it is within the range of ±10% or less. From the control precision of the rotation speed, the rotation speed that becomes approximately constant may be within a range of ±1 rpm from the rotation speed of the rotary classifier during the lowest load operation. Therefore, if the rotational speed of the rotary classifier is controlled to be approximately constant within the range of ±1 rpm, there is no significant change in combustion conditions in the boiler.

Furthermore, in the solid fuel grinding device according to one aspect of the present invention, the target value of the rotational speed of the rotary classifier controlled by the control unit is determined by the particle size of the pulverized biomass fuel required by the combustion device of the boiler. It is decided by

In the combustion device (burner) of a boiler, there is a particle size of pulverized biomass fuel that can be tolerated in order to obtain desired combustibility. For example, if the particle size is larger than a predetermined value, the pulverized biomass fuel cannot be completely burned in the boiler and uncombusted smoke is generated. On the other hand, even if the particle size is too small than the above predetermined value, the differential pressure of the mill or the power consumption increases, making it useless. Therefore, the target value of the rotation speed of the rotary classifier was determined based on the particle size of the pulverized biomass fuel required by the burner. Specifically, when the rotation speed of the rotary classifier is high, pulverized biomass fuel with a relatively small particle size is supplied to the burner, and when the rotation speed of the rotary classifier is low, pulverized biomass fuel with a relatively large particle size is supplied to the combustion device. Using the characteristics, determine the rotational speed of the rotary classifier. Thereby, based on the combustion performance of the combustion device, it is possible to easily determine the target value of the rotational speed of the rotary classifier that can satisfactorily burn pulverized biomass fuel in the boiler.

In addition, in addition to the biomass fuel grinding mode for pulverizing the biomass fuel and supplying the pulverized biomass fuel, the control unit is provided with a coal pulverization mode for pulverizing coal as the solid fuel to supply pulverized coal, and the control unit is provided with the biomass fuel. The rotation speed of the rotary classifier used in the mass fuel grinding mode and the rotation speed of the rotary classifier used in the coal grinding mode are switched.

In the above-described solid fuel grinding device equipped with a coal grinding mode for pulverizing coal into pulverized coal, the rotational speed of a rotary classifier for coal is used to pulverize coal into pulverized coal, and the biomass fuel is pulverized into pulverized coal. When using biomass fuel, the rotation speed of a rotary classifier for biomass fuel was used. As a result, it is possible to provide a solid fuel grinding device that can be used by converting coal and biomass fuel.

Furthermore, in the solid fuel grinding device according to one aspect of the present invention, the control unit controls the rotation speed of the rotary classifier used in the biomass fuel grinding mode to the rotation speed of the rotary classifier used in the coal grinding mode. Make it smaller.

Because pulverized biomass fuel has a larger particle size and is lighter than coal-derived pulverized fuel, it is difficult to pass through a rotary classifier and be supplied to a downstream boiler, and its transportability is poor. Therefore, by making the rotational speed of the rotary classifier in the biomass fuel grinding mode lower than the rotation speed of the rotary classifier in the coal grinding mode, conveyance performance is improved without interfering with the flow of the carrier gas. , it was decided that it would be supplied more reliably to the downstream combustion device.

Furthermore, in the solid fuel grinding device according to one aspect of the present invention, the control unit controls the rotary classifier in the operating range of the boiler in the case of load operation smaller than the minimum load operation of the boiler in the coal grinding mode. A rotational speed smaller than the rotational speed is used, and in the biomass fuel grinding mode, in the case of load operation less than the lowest load operation of the boiler, the rotational speed of the rotary classifier in the operation range of the boiler is approximately Use the same rotation speed.

When pulverizing coal, if the mill is operated with a load less than the minimum load of the boiler, it is pulverized so that it can pass through the rotary classifier by using the same rotational speed as that of the rotary classifier in the boiler's operating range. The coal in the mill becomes too fine, and the carbon contained in the coal functions as an individual lubricant, reducing friction, causing the grinding roller to slip against the rotary table, causing vibration, making it impossible to achieve the desired grinding. There is a possibility that it will not exist. Therefore, in the coal pulverization mode, the rotational speed of the rotary classifier was lowered when the load was less than the minimum load operation.

On the other hand, in the case of pulverized biomass fuel, it is not excessively finely pulverized like pulverized coal, and there is less risk of the roller slipping against the rotary table like coal, so even if it is less than the minimum load operation of the boiler, The rotation speed of the rotary classifier was the same as that during the boiler's operating range. This makes it easy to control the rotational speed of the rotary classifier in the biomass fuel grinding mode.

In addition, in the power plant according to one aspect of the present invention, the solid fuel pulverizing device according to any one of the above, the boiler for generating steam by burning the solid fuel pulverized in the solid fuel pulverizing device in the combustion device, It is provided with a power generation unit that generates electricity using the steam generated by the boiler.

In addition, in the solid fuel grinding method according to one aspect of the present invention, a rotary table, a grinding roller for grinding biomass fuel, which is a solid fuel, between the rotary table, and the biomass fuel is crushed by the grinding roller. In the solid fuel grinding method using a rotary classifier for classifying pulverized biomass fuel and selecting pulverized biomass fuel, the rotary classifier is used over the operating range of the boiler to which the pulverized biomass fuel is supplied from the rotary classifier. The rotation speed is controlled to be approximately constant.

Since the rotational speed of the rotary classifier is controlled to be approximately constant over the boiler's operating range, the pulverized pulverized fuel can be stably supplied to the boiler even when biomass fuel is used.

1 is a schematic configuration diagram showing a power plant according to an embodiment of the present invention.
Figure 2 is a graph showing the primary air supply amount relative to the fuel supply amount.
Figure 3 is a graph showing the particle size of pulverized biomass fuel relative to the primary air supply amount.
Figure 4 is a graph showing A/F for fuel supply amount.
Figure 5 is a graph showing the rotational speed of the rotary classifier versus the fuel supply amount in coal pulverization mode.
Figure 6 is a graph showing the rotational speed of the rotary classifier relative to the fuel supply amount in biomass fuel grinding mode.
Figure 7 is a graph showing the particle size of pulverized biomass fuel versus the rotation speed of the rotary classifier.

Below, an embodiment according to the present invention will be described with reference to the drawings.

The power plant 1 according to this embodiment is equipped with a solid fuel grinding device 100 and a boiler 200.

As an example, the solid fuel grinding device 100 is a device that crushes solid fuel such as coal or biomass fuel, generates pulverized fuel, and supplies it to the burner (combustion device) 220 of the boiler 200. The power plant 1 is provided with one solid fuel pulverizing device 100, but is provided with a plurality of solid fuel pulverizing devices 100 corresponding to each of the plurality of burners 220 of one boiler 200. It can be done as a system.

The solid fuel grinding device 100 includes a mill (crushing unit) 10, a feeder 20, a blower unit (carrier gas supply unit) 30, a state detection unit 40, and a control unit 50. I'm doing it.

In addition, in this embodiment, "upwards" refers to the vertically upper direction, and "up", such as the upper part or upper surface, refers to the vertically upper part. Likewise, “lower” indicates the vertical lower part.

The mill 10, which grinds solid fuel such as coal or biomass fuel supplied to the boiler 200 into pulverized fuel, which is solid fuel in a pulverized state, pulverizes coal and also pulverizes biomass fuel.

Here, biomass fuel refers to renewable organic resources derived from living organisms, such as thinning lumber, waste wood, driftwood, grass, waste, mud, tires, and fuels made from these. Recycled fuel (pellets or chips), etc., but is not limited to those presented here. Biomass fuel takes in carbon dioxide during the growth process of biomass, making it carbon neutral and not emitting carbon dioxide, a global warming gas. Therefore, its use is being considered in various ways.

The mill 10 includes a housing 11, a rotary table 12, a roller 13 (grinding roller), a drive unit 14, a rotary classifier 16, a fuel supply unit 17, and a rotary rotary classifier. It is provided with a motor 18 that rotates the classifier 16.

The housing 11 is formed in a cylindrical shape extending in the vertical direction and is a case that accommodates the rotary table 12, the roller 13, the rotary classifier 16, and the fuel supply unit 17.

A fuel supply unit 17 is mounted on the central portion of the ceiling 42 of the housing 11. This fuel supply unit 17 supplies solid fuel delivered from the bunker 21 into the housing 11, and is disposed at the center position of the housing 11 along the vertical direction, and the lower end extends to the inside of the housing 11. An extension is installed.

A driving unit 14 is installed near the bottom surface 41 of the housing 11, and a rotary table 12 that rotates by a driving force transmitted from the driving unit 14 is rotatably disposed.

The rotary table 12 is a circular member when viewed in plan, and is arranged so that the lower ends of the fuel supply portion 17 face each other. For example, the upper surface of the rotary table 12 may have a low central portion and an inclined shape that increases toward the outside, and may have an outer peripheral portion that is curved upward. The fuel supply unit 17 supplies solid fuel (for example, coal or biomass fuel in this embodiment) from above toward the downward rotary table 12, and the rotary table 12 transfers the supplied solid fuel to a roller ( 13), it is also called a crushing table.

When solid fuel is injected from the fuel supply unit 17 toward the center of the rotary table 12, the solid fuel is guided to the outer circumference of the rotary table 12 by the centrifugal force caused by the rotation of the rotary table 12, and the roller 13 ) and is crushed. The pulverized solid fuel is wound upward by the conveying gas (hereinafter referred to as "primary air") delivered from the conveying gas flow path (hereinafter referred to as "primary air flow path") 100a, and is sent to the rotary classifier ( 16). That is, at a plurality of locations on the outer peripheral side of the rotary table 12, there are outlets (not shown) through which the primary air flowing in from the primary air passage 100a flows out into the space above the rotary table 12 in the housing 11. It is provided. A vane (not shown) is installed above the outlet, and a turning force is applied to the primary air blown out from the outlet. The primary air imparted with a swirling force by the vane becomes an airflow with a rotating speed component, and the solid fuel pulverized on the rotary table 12 is guided to the rotary classifier 16 above within the housing 11. In addition, among the pulverized solid fuel mixed with primary air, those larger than a predetermined particle size are classified by the rotary classifier 16, or fall without reaching the rotary classifier 16 and reach the rotary table 12. ) and is pulverized again.

The roller 13 is a rotating body that crushes the solid fuel supplied from the fuel supply unit 17 to the rotary table 12. The roller 13 is pressed against the upper surface of the rotary table 12 and cooperates with the rotary table 12 to crush the solid fuel.

In FIG. 1 , only one roller 13 is shown, but a plurality of rollers 13 are arranged facing each other at regular intervals in the circumferential direction to press the upper surface of the rotary table 12. For example, three rollers 13 are arranged at equal intervals in the circumferential direction at an angular interval of 120° on the outer periphery. In this case, the portion where the three rollers 13 contact the upper surface of the rotary table 12 (the portion that is pressed) is equidistant from the central axis of rotation of the rotary table 12.

The roller 13 is capable of swinging up and down by the journal head 45, and is supported so as to be close to and away from the upper surface of the rotary table 12. The roller 13 has its outer peripheral surface in contact with the upper surface of the rotary table 12, and when the rotary table 12 rotates, it receives rotational force from the rotary table 12 and rotates along it. When solid fuel is supplied from the fuel supply unit 17, the solid fuel is pressurized and pulverized between the roller 13 and the rotary table 12 to become pulverized fuel.

The support arm 47 of the journal head 45 is supported by a support shaft 48 whose middle portion extends in the horizontal direction. That is, the support arm 47 is supported on the side surface of the housing 11 so as to be able to swing in the roller up and down direction with the support shaft 48 as the center. Additionally, a pressurizing device 49 is provided at the upper end of the support arm 47 vertically. The pressing device 49 is fixed to the housing 11 and applies a load to the roller 13 via the support arm 47 or the like so as to press the roller 13 against the rotary table 12.

The driving unit 14 is a device that transmits driving force to the rotary table 12 and rotates the rotary table 12 around the central axis. The driving unit 14 generates a driving force to rotate the rotary table 12.

The rotary classifier 16 is provided on the upper part of the housing 11 and has a hollow, substantially inverted cone-shaped outer shape. The rotary classifier 16 is provided with a plurality of blades 16a extending in the vertical direction at its outer peripheral position. Each blade 16a is provided in parallel at a predetermined interval (equal interval) around the central axis of the rotary classifier 16. In addition, the rotary classifier 16 divides the solid fuel pulverized by the roller 13 into particles larger than a predetermined particle size (for example, 70㎛ to 100㎛ for coal, 0.6㎜ to 1.0㎜ for biomass fuel). It is a device that classifies pulverized solid fuel that exceeds a predetermined particle size into those (hereinafter, pulverized solid fuel that exceeds a predetermined particle size is referred to as “coarse fuel”) and those that are smaller than a predetermined particle size (hereinafter, pulverized solid fuel that exceeds a predetermined particle size is referred to as “pulverized fuel”). The rotary classifier 16 is provided with a rotational driving force by a motor 18 controlled by the control unit 50.

The fuel after pulverization of the solid fuel that has reached the rotary classifier 16 is divided into large-diameter coarse fuel by the blade ( It is struck down by 16a), returned to the rotary table 12, and pulverized again, and the pulverized fuel is delivered to the outlet 19 at the ceiling 42 of the housing 11.

The pulverized fuel classified by the rotary classifier 16 is discharged from the outlet 19 to the supply passage 100b and is returned to the subsequent process together with primary air. The pulverized fuel flowing out of the supply passage 100b is supplied to the burner 220 of the boiler 200.

The fuel supply unit 17 is mounted with its lower end extending to the inside of the housing 11 along the vertical direction so as to penetrate the top of the housing 11. Solid fuel injected from the top of the fuel supply unit 17 is supplied to approximately the central area of the rotary table 12. Solid fuel is supplied to the fuel supply unit 17 from the feeder 20.

The feeder 20 includes a bunker 21, a transport unit 22, and a motor 23. The transport unit 22 transports the solid fuel discharged from the lower end of the down spout unit 24 directly below the bunker 21 by the driving force provided by the motor 23. The solid fuel transported by the transport unit 22 is delivered to the fuel supply unit 17 of the mill 10.

Normally, primary air for conveying pulverized fuel, which is pulverized solid fuel, is supplied to the inside of the mill 10, and the pressure is higher than atmospheric pressure. Fuel is held in a laminated state inside the downspout portion 24, which is a pipe extending in the vertical direction directly below the bunker 21, and fuel is stored in a laminated state by the solid fuel layer laminated within the downspout portion 24. , sealing is ensured so that the primary air on the mill 10 side and the fuel after grinding do not flow back. The amount of solid fuel supplied to the mill 10 may be adjusted by adjusting the belt speed of the belt conveyor of the conveyance unit 22 by the motor 23 controlled by the control unit 50.

Chips and pellets of biomass fuel before grinding have a constant particle size compared to coal fuel (that is, the particle size of coal before grinding is, for example, about 2 mm to 50 mm) (the size of the pellet is, for example, about 2 mm to 50 mm). , the diameter is about 6 mm to 8 mm, the length is about 40 mm or less), and it is also lightweight. For this reason, when biomass fuel is stored in the downspout portion 24, the gap formed between each biomass fuel becomes larger compared to the case of coal fuel.

Therefore, since there is a gap between the chips or pellets of biomass fuel in the downspout part 24, the primary air and pulverized fuel blown up from the inside of the mill 10 pass through the gap formed between each biomass fuel, and the mill 10 (10) There is a possibility that the internal pressure may decrease. In addition, if primary air blows into the storage part of the bunker 21, the transferability of the biomass fuel deteriorates, dust is generated, the down spout part 24 ignites, and if the pressure inside the mill 10 decreases, the pulverized fuel There is a possibility that various problems may occur in the operation of the mill 10, such as a decrease in the conveyance amount. For this reason, a rotary valve (not shown) may be provided in the middle of the fuel supply section 17 from the feeder 20 to suppress backflow caused by the injection of primary air and pulverized fuel.

The blower 30 is a device that dries the solid fuel pulverized by the roller 13 and simultaneously blows primary air to the inside of the housing 11 to supply it to the rotary classifier 16.

The blower 30 includes a hot gas blower 30a, a cold gas blower 30b, a hot gas damper 30c, and a cold gas damper in order to adjust the primary air blown into the housing 11 to an appropriate temperature. (30d) is provided.

The heat gas blower 30a is a blower that blows heated primary air supplied from a heat exchanger such as an air preheater. A heat gas damper 30c is provided on the downstream side of the heat gas blower 30a. The opening degree of the heat gas damper 30c is controlled by the control unit 50. The flow rate of primary air blown by the heat gas blower (30a) is determined by the opening degree of the heat gas damper (30c).

The cold gas blower 30b is a blower that blows primary air, which is outdoor air at room temperature. A cold gas damper 30d is provided on the downstream side of the cold gas blower 30b. The opening degree of the cold gas damper 30d is controlled by the control unit 50. The flow rate of primary air blown by the cold gas blower (30b) is determined by the opening degree of the cold gas damper (30d).

The flow rate of the primary air is the flow rate of the sum of the flow rate of the primary air blown by the hot gas blower 30a and the flow rate of the primary air blown by the cold gas blower 30b, and the temperature of the primary air is the flow rate of the primary air blown by the hot gas blower (30b). It is determined by the mixing ratio of the primary air blown by 30a) and the primary air blown by the cold gas blower 30b, and is controlled by the control unit 50.

In addition, a part of the combustion gas discharged from the boiler 200, which has passed through an environmental device such as an electric precipitator through a gas recirculation ventilator, is introduced into the primary air blown by the heat gas blower 30a to form a mixer. , the oxygen concentration of the primary air flowing in from the primary air flow path 100a may be adjusted.

In this embodiment, data measured or detected by the state detection unit 40 of the housing 11 is transmitted to the control unit 50. The state detection unit 40 of the present embodiment is, for example, a differential pressure measuring means, and is a portion through which primary air flows into the mill 10 from the primary air passage 100a and a supply passage 100b from the inside of the mill 10. The differential pressure at the outlet 19 through which the primary air and pulverized fuel discharge is measured as the differential pressure within the mill 10. For example, depending on the classification performance of the rotary classifier 16, the amount of circulation of pulverized solid fuel circulating inside the mill 10 between the vicinity of the rotary classifier 16 and the rotary table 12 increases and decreases, and The rise and fall of the differential pressure within the mill 10 changes. That is, since the solid fuel supplied to the inside of the mill 10 can be managed by adjusting the pulverized fuel discharged from the outlet 19, the particle size of the pulverized fuel does not affect the combustibility of the burner 220. Within the range, a lot of pulverized fuel can be supplied to the burner 220 provided in the boiler 200.

In addition, the state detection unit 40 of the present embodiment is, for example, a temperature measuring means, and provides primary air for supplying the solid fuel pulverized by the roller 13 to the rotary classifier 16 into the housing 11. The temperature in the housing 11 of the primary air whose temperature is adjusted by the blower 30 blowing into the inside is detected, and the blower 30 is controlled so as not to exceed the upper temperature limit. Additionally, since the primary air is cooled in the housing 11 by conveying the pulverized material while drying, the temperature of the upper space of the housing 11 is, for example, about 60°C to 80°C.

The control unit 50 is a device that controls each part of the solid fuel grinding device 100. The control unit 50 may control the rotation speed of the rotary table 12 for operation of the mill 10 by, for example, transmitting a drive instruction to the drive unit 14. The control unit 50 adjusts the classification performance by, for example, transmitting a drive instruction to the motor 18 of the rotary classifier 16 to control the rotation speed, thereby optimizing the differential pressure within the mill 10 to differentiate the rotary classifier 16. The supply of fuel can be stabilized. In addition, the control unit 50 transmits a drive instruction to the motor 23 of the fuel feeder 20, for example, so that the transport unit 22 transfers the solid fuel and supplies it to the fuel supply unit 17. The amount of fuel supplied can be adjusted. In addition, the control unit 50 transmits an opening degree instruction to the blower 30 to control the opening degrees of the hot gas damper 30c and the cold gas damper 30d to control the flow rate and temperature of the primary air. You can.

The control unit 50 is composed of, for example, a Central Processing Unit (CPU), Random Access Memory (RAM), Read Only Memory (ROM), and a computer-readable storage medium. As an example, a series of processing to realize various functions is stored in a storage medium, etc. in the form of a program, and the CPU reads this program into RAM, etc., and performs information processing and calculation processing to perform various functions. This comes true. Additionally, the program may be installed in advance on ROM or other storage media, provided as stored in a computer-readable storage medium, or delivered through wired or wireless communication means. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

Next, the boiler 200 that generates steam by performing combustion using pulverized fuel supplied from the solid fuel grinding device 100 will be described.

The boiler 200 is equipped with a furnace 210 and a burner 220.

The burner 220 uses primary air containing pulverized fuel (pulverized coal or pulverized biomass fuel in this embodiment) supplied from the supply passage 100b and secondary air supplied from a heat exchanger (not shown) to produce pulverized fuel. It is a device that combusts to form a flame. Combustion of the pulverized fuel is performed within the furnace 210, and the high-temperature combustion gas is discharged to the outside of the boiler 200 after passing through a heat exchanger (not shown) such as an evaporator, superheater, or economizer.

The combustion gas discharged from the boiler 200 is subjected to predetermined processing in an environmental device (denitrification device, electrostatic precipitator, etc., not shown), and at the same time, heat exchange is performed with the outside air in a heat exchanger such as an air preheater (not shown). It is guided to the chimney (not shown) through an induced ventilator (not shown) and discharged into the atmosphere. The outside air heated by heat exchange with the combustion gas in the heat exchanger is sent to the heat gas blower 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, and the steam that is the power generation unit is heated. It is sent to a turbine (not shown) and rotates a generator (not shown) to generate power.

[Control of primary air supply]

Next, the control of the primary air supply amount (carrier gas supply amount) A supplied from the blower 30 into the mill 10 will be explained. Control of the primary air supply amount A is performed by the control unit 50 based on FIG. 2. When operating the mill 10, the control unit 50 mainly uses a coal grinding mode to grind coal as a solid fuel supplied to the mill 10 and supply pulverized coal to the burner 220, and a coal grinding mode to mainly grind biomass fuel. The biomass fuel grinding mode that supplies the pulverized biomass fuel to the burner 220 is switched and controlled.

Figure 2 shows the primary air supply amount (A) in each of the coal grinding mode and the biomass fuel grinding mode. In the same figure, the horizontal axis represents the fuel supply amount (F) (weight flow rate), and the vertical axis represents the primary air supply amount (A) (weight flow rate).

On the horizontal axis, the fuel supply amount (F) is standardized with 1.0 being the rated operation time of the boiler 200. As an example, the fuel supply amount (F) during the lowest load operation of the boiler 200 is set to 0.4, and the fuel supply amount (F) during the overload operation of the boiler 200 is set to 1.25. Accordingly, the operating range of the boiler 200 is 0.4 or more and 1.25 or less. In addition, the values for the lowest load operation and the overload operation of the boiler 200 are only examples and are set in various ways depending on the boiler 200.

On the vertical axis, the primary air supply amount (A) during the lowest load operation in the biomass fuel grinding mode is set to 1.0, and the primary air supply amount (A) is standardized.

<Coal crushing mode>

The primary air supply amount A2 in the coal pulverization mode is constant at 0.65, as shown by the broken line in FIG. 2, for example, in a region where the fuel supply amount F is less than 0.4 during the lowest load operation. In addition, the value of 0.65 for the primary air supply amount (A2) is only an example and means smaller than the primary air supply amount (A1) (i.e. 1.0) in the biomass fuel grinding mode. In addition, over the operating range from the lowest load operation to the rated operation, or over the entire operating range from the lowest load to the overload operation, the primary air supply amount (A1) used in the biomass fuel grinding mode is calculated as It may be greater than the primary air supply amount (A2) used at the time.

The primary air supply amount (A2) during coal grinding mode increases when the fuel supply amount (F) during minimum load operation becomes 0.4 or more until it reaches 1.25 during overload operation, for example, as shown in Figure 2. increases monotonically. This takes into account the drying performance of drying the coal and the transportability of transporting the coal. In other words, since coal has a higher water content than biomass fuels such as lignocellulosic pellets, when the fuel supply amount (F) increases, the heat of vaporization increases to achieve dryness, so it is necessary to increase the amount of primary air. In addition, as the fuel supply amount (F) increases, transportability is obtained, so it is necessary to increase the amount of primary air.

The temperature of the primary air in the coal grinding mode is, for example, controlled by the hot gas damper 30c and the cold gas damper 30d (see FIG. 1) by the control unit 50 near the outlet of the primary air flow path 100a. By controlling, it is adjusted to 250°C or higher and 350°C or lower.

<Biomass fuel grinding mode>

The primary air supply amount (A1) in the biomass fuel grinding mode is, as shown by the solid line in FIG. 2, over the entire operating range of the boiler 200, that is, from 0.4, which is the lowest load operation, to 1.25, which is the overload operation. Throughout, it is approximately constant at 1.0. The reason is as follows.

The pulverized biomass fuel has a larger particle size than pulverized fuel, which is a pulverized fuel derived from coal, and it is difficult to pass between the blades 16a of the rotary classifier 16, so the rotation speed of the rotary classifier is adjusted as described later. I'm doing it small. In addition, the pulverized biomass fuel tends to accumulate in gaps or stagnant air currents inside the mill 10, has a small specific gravity, and the rotation speed of the rotary classifier 16 is set slow, for example. Even if a region in which the primary air current is stagnated occurs within the rotary classifier 16, and pulverized biomass fuel accumulates within the rotary classifier 16, it is removed and discharged by the centrifugal force of the rotary classifier 16. It's difficult. For this reason, it is necessary not to create an area where the airflow of primary air stays, that is, to secure sufficient conveyance force based on the flow rate of primary air, and even if the boiler 200 is operated at low load such as the minimum load operation, pulverized In order to secure the conveying force necessary for conveying biomass fuel, a primary air supply amount (A1) of a predetermined value or more is required. On the other hand, biomass fuel has a lower moisture content than pulverized coal fuel, so there is relatively little need for primary air drying. Therefore, even if the boiler 200 is operated at a high load such as rated operation, there is no need to increase the primary air supply amount A1 to dry moisture in the fuel.

Additionally, the primary air supply amount A1 may be kept approximately constant, and may not be kept strictly constant. Here, approximately constant means, for example, the ratio of the amount of change in the increase or decrease in the primary air supply amount A1 before and after the change in increase or decrease in the fuel supply amount F corresponding to the increase or decrease in the load of the boiler 200. It is good if it is within the range of ±10% or less.

The temperature of the primary air in the biomass fuel grinding mode is set lower than that in the coal grinding mode by controlling the hot gas damper 30c and the cold gas damper 30d (see FIG. 1) by the control unit 50. For example, it is adjusted to 100℃ or higher and 150℃ or lower. The upper limit temperature is set not to exceed 200℃. This is because there is a risk of ignition of biomass fuel when the temperature exceeds 200°C. In addition, for example, the moisture content of biomass fuel in lignocellulosic pellets is dried to prevent fermentation during production, and becomes about 15 w% or less.

The primary air supply amount (A1) in the biomass fuel grinding mode is determined by a static characteristic test during test run, as shown in FIG. 3. Specifically, it is determined by the particle size of the pulverized biomass fuel required by the burner 220 of the boiler 200. The target particle size (d1) of the pulverized biomass fuel is determined, for example, considering the following conditions. If the particle size of the pulverized biomass fuel increases due to the combustibility of the burner 220, the unburned content may increase without being burned out in the burner 220. On the other hand, in order to improve the combustibility of the pulverized biomass fuel and reduce the particle size of the pulverized biomass fuel, for example, the pressing force on the biomass fuel between the roller 13 and the rotary table 12 is increased. This is necessary, and the rotational power of the rotary table 12 required for pulverization increases, thereby reducing efficiency. For this reason, the target particle size (d1) of the pulverized biomass fuel is set to about 0.6 mm to 1 mm, for example.

In FIG. 3, the horizontal axis represents the primary air supply amount A1, and the vertical axis represents the particle size of the pulverized biomass fuel conveyed from the mill 10 toward the burner 220.

As shown in FIG. 3, the target particle size d1 is determined from the combustibility of the burner 220 and the rotational power of the rotary table 12 required for pulverization. In addition, the particle size of the finely divided biomass fuel to be transported increases as the primary air supply amount (A1) increases because the transport force increases. On the other hand, as the primary air supply amount (A1) decreases, the conveying force decreases, and thus the conveyed particle size decreases. Therefore, by increasing or decreasing the primary air supply amount A1, it is possible to obtain the primary air supply amount A1 conveyed corresponding to the target particle size d1.

In the static characteristics test during test run, A/F (primary air supply amount/fuel supply amount) is also examined, as shown in FIG. 4.

In Figure 4, A/F is shown for the fuel supply amount (F). In the same figure, the solid line represents the biomass fuel grinding mode, and the dashed line represents the coal grinding mode.

As shown in the same figure, A/F decreases as the fuel supply amount (F) increases in either the coal grinding mode or the biomass fuel grinding mode. However, as shown in Figure 2, the primary air supply amount (A) is greater in the biomass fuel grinding mode than in the coal grinding mode, so when compared at the same fuel supply amount (F), the biomass fuel grinding mode is larger than the coal grinding mode. A/F is big.

If A/F becomes large, there is a risk that there will be excess air in the burner 220 and stable combustion may not be maintained. Therefore, so that A/F at the fuel supply amount (F) (=0.4) during the lowest load operation of the lean combustion boiler 200 does not exceed the upper limit, the primary air supply amount (A1) in the biomass fuel grinding mode ) is set. The upper limit value of A/F when the fuel supply amount F (=0.4) is determined from the combustibility of the burner 220 and is, for example, 2 or more and 5 or less. In addition, the primary air supply amount (A1) removes the pulverized biomass fuel from the mill 10 without allowing the pulverized biomass fuel to remain in the mill 10 even if the supply amount of biomass fuel is maximum during overload operation. It is set to a flow rate that can be returned to the burner 220. For example, as shown in Figure 2, the primary air supply amount (A1) of the biomass fuel grinding mode under rated operation in the coal grinding mode is set to be greater than the primary air supply amount (A2) of the coal grinding mode, , During overload operation in coal grinding mode, the primary air supply amount (A1) in biomass fuel grinding mode is set to the same level as the primary air supply amount (A2) in coal grinding mode.

[Control of rotation speed of rotary classifier 16]

Next, control of the rotational speed of the rotary classifier 16 will be explained. Control of the rotational speed of the rotary classifier 16 is performed by the control unit 50. When operating the mill 10, the control unit 50 switches and controls the coal grinding mode and the biomass fuel grinding mode.

The rotation speed of the rotary classifier 16 is controlled primarily by controlling the primary air supply amount A described above, and then secondarily adjusted. The reason that control of the primary air supply amount (A) is given priority over control of the rotation speed of the rotary classifier 16 is that the primary air supply amount (A) has a direct effect on the combustion performance in the burner 220 of the boiler 200. This is because it affects.

<Coal crushing mode>

Figure 5 shows the rotational speed control of the rotary classifier 16 in coal pulverizing mode. The horizontal axis represents the fuel (coal) supply amount (F), and the vertical axis represents the rotational speed of the rotary classifier 16.

On the horizontal axis, 1.0 is standardized as the fuel supply amount (F) during rated operation of the boiler 200. As an example, the fuel supply amount (F) during the lowest load operation of the boiler 200 is set to 0.4, and the fuel supply amount (F) during the overload operation of the boiler 200 is set to 1.25. Accordingly, the operating range of the boiler 200 is 0.4 or more and 1.25 or less. In addition, the values for the lowest load operation and the overload operation of the boiler 200 are only examples and are set in various ways depending on the boiler 200.

On the vertical axis, the rotary classifier during the lowest load operation of the boiler 200 in the biomass fuel grinding mode described later is standardized to 1.0.

The rotational speed of the rotary classifier 16 in the coal pulverization mode is set to promote classification of fine powder and coarse powder to supply pulverized coal with a small particle size to ensure combustibility of the burner 220. For this reason, the rotation speed of the rotary classifier 16 in the coal grinding mode is set higher than the rotation speed (1.0) of the rotary classifier 16 in the biomass fuel grinding mode. When the fuel supply amount (F) is less than 0.4 during minimum load operation, the rotation speed of the rotary classifier 16 is set to about 5.0, and as it increases to 0.4 during minimum load operation, the rotation speed is increased to 8.0. The reason for increasing the rotational speed of the rotary classifier 16 from the low load side to the lowest load operation is as follows.

That is, in the case of load operation smaller than the minimum load operation, if the coal is pulverized using the same rotation speed (8.0) of the rotary classifier 16 during the load operation larger than the minimum load operation, the rotary classifier The coal in the pulverized mill 10 becomes too fine to pass through (16), the carbon contained in the coal functions as an individual lubricant, and the friction force decreases, causing the roller 13 to move against the rotary table 12. This is because there is a possibility that the desired pulverization may not be possible due to slippage and vibration. For this reason, in the coal pulverization mode, the rotational speed of the rotary classifier 16 is lowered when it is less than the minimum load operation, and in this embodiment, the rotational speed is set to about 5.0.

When the fuel supply amount F is from 0.4 to about 1.1, which exceeds the rated operation of 1.0, the rotational speed of the rotary classifier 16 is approximately constant at 8.0.

In addition, as shown in FIG. 2, when the fuel supply amount (F) increases, the primary air supply amount (A2) increases, thereby increasing the transportability of the pulverized coal, so that the pulverized coal fuel supplied to the burner 220 has a predetermined particle size. (To enable classification), the rotational speed of the rotary classifier 16 is gradually increased as the fuel supply amount (F) increases from 0.4 to 1.1, which exceeds 1.0, which is the rated operation, as the primary air supply amount (A2) increases, and the burner ( 220) It may be possible to suppress the increase in coarse powder in the pulverized coal fuel supplied.

The upper limit of the fuel supply amount (F) is set to 1.1, which exceeds the rated operation, but it may be 1.0, which is the rated operation, and is set appropriately depending on the operation.

The rotational speed of the rotary classifier 16 was determined to be stable in the burner 220 of the boiler 200 from the particle size and pulverized coal flow rate of the pulverized coal supplied from the outlet of the mill 10 to the burner 220 in a static characteristic test during test operation. Combustibility is determined by selecting the appropriate rotational speed at which combustibility is achieved. The rotation speed of the rotary classifier 16 is, for example, 90 rpm or more and 180 rpm or less. Additionally, the rotation speed of the rotary classifier 16 may be controlled to gradually increase as the fuel supply amount F increases.

During overload operation where the fuel supply amount (F) exceeds the rated operation from 1.1 to 1.25, the rotation speed of the rotary classifier 16 as shown by the solid line is not a constant rotation speed as shown by the broken line, but the fuel supply amount (F ) should be decreased according to the increase. This is to ensure that when the fuel supply amount (F) increases, the rotational power of the rotary table 12 of the mill 10 increases, so as not to exceed the power specification limit of the mill 10. That is, when the fuel supply amount F increases, the amount of granulated fuel classified by the rotary classifier 16 increases, and the amount of granulated fuel falling on the rotary table 12 increases. In that case, the power of the rotary table 12 increases and approaches the power limit controlled for the operation of the mill 10, so the rotation speed of the rotary classifier 16 is reduced. As a result, the granulated fuel also passes through the rotary classifier 16 and is conveyed to the downstream burner 220, thereby suppressing an increase in the amount of granulated fuel falling on the rotary table 12. On the other hand, since it exceeds the allowable level of the granulated fuel that can maintain combustibility in the burner 220, combustibility is reduced. As the assembly fuel increases in the burner 220 and performs combustion, the combustibility in the burner 220 may slightly decrease, but the frequency during overload operation where the fuel supply amount (F) exceeds the rated operation from 1.1 to 1.25 Since is small and short-term, the power limitation of the mill 10 can be managed with priority, with little effect on the power plant 1.

<Biomass fuel grinding mode>

Figure 6 shows the rotational speed control of the rotary classifier 16 in the biomass fuel grinding mode. The horizontal and vertical axes are the same as in Figure 5.

As shown in FIG. 6, in the biomass fuel grinding mode, the rotational speed of the rotary classifier 16 is approximately constant at 1.0, with the fuel supply amount F ranging from 0.4, which is the lowest load, to 1.25, which is the overload. This means that pulverized biomass fuel has a larger particle size than coal-derived pulverized fuel and is difficult to pass through the blade 16a of the rotary classifier 16. For this reason, the rotation speed of the rotary classifier 16 is set low. In addition, because the specific gravity is small, the accumulated matter in the stagnant area of the air flow cannot be discharged from the rotary classifier 16 because the centrifugal force is small even if centrifugal force is applied by the rotary classifier 16, so it stays in the rotary classifier and accumulates. It is easy to pass through the rotary classifier 16 from the mill 10 and is difficult to discharge from the outlet 19. For this reason, when the input amount of biomass fuel is increased as the load operation of the boiler 200 increases, if the rotation speed of the rotary classifier 16 is increased to promote granular classification, the rotary classifier 16 The supply amount of finely divided biomass fuel supplied from the boiler 200 does not increase to suit the load, but rather, the density of the granulated biomass fuel that falls from the inside of the mill 10 to the rotary classifier 16 increases, causing the mill ( Only the load of 10) is likely to rise. In addition, since the rotation speed of the rotary classifier 16 in the biomass fuel grinding mode is small, the unit required to control the rotation speed of the rotary classifier 16 is refined to the level of 0.1 rpm to 1 rpm, making it impossible to perform practical control. I can't. Therefore, even if the load on the boiler 200 increases, the rotary classifier 16 is operated at an approximately constant rotation speed while supplying pulverized biomass fuel suitable for the increase in the load on the boiler 200.

Here, approximately constant means, for example, the increase/decrease of the rotational speed of the rotary classifier 16 before and after the increase/decrease change in the fuel supply amount F corresponding to the increase/decrease in the load of the boiler 200. It is good if the rate of change is within the range of ±10% or less. From the control precision of the rotation speed, the rotation speed that becomes approximately constant may be within a range of ±1 rpm from the rotation speed of the rotary classifier 16 during the lowest load operation. That is, the rotation speed of the rotary classifier 16 in the biomass fuel grinding mode is approximately constant within the range of ±1 rpm, and the median value is, for example, 10 rpm or more and 30 rpm or less. Additionally, the rotational speed of the rotary classifier 16 in the biomass fuel grinding mode is lower than that in the coal grinding mode. This is because the pulverized biomass fuel has a larger particle diameter compared to pulverized coal and is difficult to pass between the blades 16a of the rotary classifier 16. In addition, since pulverized biomass fuel is lighter than pulverized coal, the centrifugal force generated by the rotation of the blade 16a of the rotary classifier 16 is small in the pulverized biomass fuel. . For this reason, the action of the centripetal force caused by the airflow of primary air increases, making it easier for the fine powder, including coarse powder, of the pulverized biomass fuel to pass between the blades 16a and enter the rotary classifier 16. At this time, if the primary air flow stagnates in the rotary classifier 16, the fine powder including the coarse powder of the pulverized biomass fuel stays, but since the centrifugal force acting on the fine powder including the coarse powder of the pulverized biomass fuel is small, the rotary classifier 16 It accumulates in the classifier 16 and is difficult to discharge, and it becomes difficult to be supplied from the inside of the mill 10 through the rotary classifier 16 to the burner 220 from the outlet 19. For this reason, the rotation speed of the rotary classifier 16 is reduced to prevent the flow of primary air from being disturbed and to promote conveyance by primary air.

In the biomass fuel grinding mode, unlike the coal grinding mode (see FIG. 5), in the case of a load smaller than the minimum load, approximately the same rotation speed is used without lowering the rotation speed of the rotary classifier 16. This is because, in the case of biomass fuel, it is not excessively finely ground like coal, and there is no risk of the roller 13 slipping against the rotary table 12 like coal.

In Figure 7, the concept for determining the constant rotational speed of the rotary classifier 16 in the biomass fuel grinding mode is shown. In the same figure, the horizontal axis represents the rotational speed of the rotary classifier 16, and the vertical axis represents the particle size of the pulverized fuel conveyed through the rotary classifier 16.

The rotational speed of the rotary classifier 16 is determined by the maximum particle size of the pulverized biomass fuel required by the burner 220 of the boiler 200. From the combustibility of the burner 220, if the particle size of the pulverized biomass fuel increases, the unburned content increases without burning out in the burner 220, and if it decreases, the differential pressure of the mill 10 and the power consumption increase, so it is determined by taking this into consideration. . Once the target particle size (1.0) of the pulverized fuel is determined, the rotational speed of the rotary classifier 16 is adjusted to meet this target particle size. Specifically, as shown in FIG. 7, when the rotation speed of the rotary classifier 16 is increased, the particle size of the pulverized biomass fuel returned to the subsequent process together with the primary air becomes smaller, and the rotation of the rotary classifier 16 decreases. Using the characteristic that when the speed is reduced, the particle size of the pulverized biomass fuel returned to the subsequent process together with the primary air increases, the rotational speed of the rotary classifier 16 is determined to be an appropriate value (1.0). In this embodiment, the target particle size of the pulverized biomass fuel is set to about 0.6 mm to 1 mm, for example.

According to this embodiment, the following effects are achieved.

Pulverized biomass fuel has a larger particle size than pulverized fuel, which is pulverized fuel derived from coal, and is difficult to pass between the blades 16a of the rotary classifier 16. In addition, because it has a small specific gravity and is light, once it enters the rotary classifier 16, the centrifugal force on the pulverized biomass fuel is small in the area where the airflow of the carrier gas stays, so it is difficult to accumulate and discharge. Therefore, it is difficult to pass through the rotary classifier 16 and be returned and supplied to the downstream burner 220. For this reason, as the load on the boiler 200 increases, the input amount of biomass fuel is increased and the rotation speed of the rotary classifier 16 is also increased, and the pulverized fuel is supplied from the rotary classifier 16 to the boiler. The supply amount does not increase to suit the load. Therefore, even if the load on the boiler 200 increases, by controlling the rotary classifier 16 at an approximately constant rotation speed, pulverized fuel suitable for the increase in the load on the boiler 200 can be supplied. Additionally, since the rotational speed of the rotary classifier 16 can be controlled to be approximately constant, simple control can be realized.

In the burner 220 of the boiler 200, there is a particle size of pulverized biomass fuel that can be tolerated in order to obtain desired combustibility. For example, if the particle size is larger than a predetermined value, the pulverized biomass fuel cannot be completely burned within the boiler 200 and unburned smoke is generated. Therefore, the target value of the rotation speed of the rotary classifier 16 was determined based on the particle size of the pulverized biomass fuel required by the burner 220. Accordingly, based on the combustion performance of the burner 220, it is possible to easily determine the target value of the rotational speed of the rotary classifier 16 that can satisfactorily combust the pulverized biomass fuel within the boiler 200.

When pulverizing coal into pulverized coal, the rotation speed of the rotary classifier 16 for coal is used, and when pulverizing biomass fuel into pulverized biomass fuel, the rotation speed of the rotary classifier 16 for biomass fuel is used. The rotation speed was used. As a result, it is possible to provide a solid fuel grinding device 100 that can be used by converting coal and biomass fuel.

Since the pulverized biomass fuel has a larger particle size and is lighter than coal-derived pulverized fuel, it is difficult to pass through the rotary classifier 16 and be supplied to the downstream boiler, and the transportability is poor. Therefore, the rotation speed of the rotary classifier 16 in the biomass fuel grinding mode is made smaller than the rotation speed of the rotary classifier 16 in the coal grinding mode, thereby impeding the flow of the carrier gas. By improving transportability, it can be more reliably supplied to the downstream combustion device.

When pulverizing coal, when operating the mill 10 with a load smaller than the minimum load of the boiler 200, the rotation speed is the same as the rotation speed of the rotary classifier 16 in the operating range of the boiler 200. When the coal is pulverized using a , the coal in the pulverized mill 10 is too fine to pass through the rotary classifier 16, and the carbon contained in the coal functions as an individual lubricant, reducing friction, and the rotary table There is a possibility that the roller 13 may slip relative to (12) and generate vibration, making it impossible to achieve desired pulverization. Therefore, as shown in FIG. 5, in the coal pulverizing mode, the rotation speed of the rotary classifier 16 is lowered when the load is less than the minimum load operation.

On the other hand, in the case of pulverized biomass fuel, it is not excessively finely pulverized like pulverized coal, and there is little risk of the roller 13 slipping against the rotary table 12 like coal, so the boiler 200 Even in the case where the operation load is smaller than the lowest load, the rotational speed of the rotary classifier 16 was set to be the same as that in the operating range of the boiler 200 (see FIG. 6). This makes it easy to control the rotational speed of the rotary classifier 16 in the biomass fuel grinding mode.

1: Power plant 10: Mill
11: Housing 12: Rotating table
13: roller (crushing roller) 14: driving unit
16: rotary classifier 16a: blade
17: fuel supply unit 18: motor
19: Exit 20: Feeder
21: bunker 22: transport unit
23: motor 24: down spout part
30: blowing unit (return gas supply unit) 30a: heat gas blower
30b: cold gas blower 30c: hot gas damper
30d: cold gas damper 40: status detection unit
41: bottom part 42: ceiling part
45: journal head 47: support arm
48: support shaft 49: pressurizing device
50: Control unit 100: Solid fuel grinding device
100a: Primary air flow path 100b: Supply flow path
200: boiler 210: furnace
220: Burner (combustion device) A: Primary air supply amount
A1: Primary air supply (in biomass fuel grinding mode)
A2: Primary air supply amount (in coal grinding mode)
d1: Target maximum particle size (of biomass fuel) F: Fuel supply amount

Claims (8)

rotary table,
a grinding roller for grinding biomass fuel between the rotary table;
A rotary classifier for classifying the pulverized biomass fuel obtained by pulverizing the biomass fuel using the pulverizing roller to select finely divided biomass fuel;
Equipped with a control unit that controls the rotation speed of the rotary classifier,
The control unit controls the rotational speed of the rotary classifier to be approximately constant regardless of the increase or decrease in the supply amount of the pulverized biomass fuel in the entire operating range from the lowest load of the boiler to which the pulverized biomass fuel is supplied to the overload operation. do,
When pulverizing the biomass fuel, in the case of load operation less than the lowest load operation of the boiler, a rotation speed approximately equal to the rotation speed of the rotary classifier in the operation range of the boiler is used.
Solid fuel crushing device. According to claim 1,
The control unit controls the rotation speed of the rotary classifier to be approximately constant within the range of ±1rpm.
Solid fuel crushing device. The method of claim 1 or 2,
The target value of the rotational speed of the rotary classifier controlled by the control unit is determined by the particle size of the pulverized biomass fuel required by the combustion device of the boiler.
Solid fuel crushing device. The method of claim 1 or 2,
In addition to the biomass fuel grinding mode for pulverizing the biomass fuel to supply the pulverized biomass fuel, a coal pulverization mode for pulverizing coal to supply pulverized coal,
The control unit switches the rotation speed of the rotary classifier used in the biomass fuel grinding mode and the rotation speed of the rotary classifier used in the coal grinding mode.
Solid fuel crushing device. According to claim 4,
The control unit sets the rotation speed of the rotary classifier used in the biomass fuel grinding mode to be lower than the rotation speed of the rotary classifier used in the coal grinding mode.
Solid fuel crushing device. According to claim 4,
The control unit,
In the coal grinding mode, in the case of load operation smaller than the lowest load operation of the boiler, a rotation speed smaller than the rotation speed of the rotary classifier in the operation range of the boiler is used.
Solid fuel crushing device. The solid fuel grinding device according to claim 1 or 2,
The boiler for generating steam by burning the solid fuel pulverized in the solid fuel pulverizing device,
Equipped with a power generation unit that generates electricity using the steam generated by the boiler
power plant. rotary table,
A grinding roller for grinding biomass fuel, which is a solid fuel, between the rotary table and the rotary table;
In the solid fuel grinding method using a rotary classifier to classify the pulverized biomass fuel obtained by pulverizing the biomass fuel by the grinding roller to select finely divided biomass fuel,
In the entire operating range from the lowest load to the overload operation of the boiler to which the pulverized biomass fuel is supplied from the rotary classifier. Controlling the rotational speed of the rotary classifier to be approximately constant regardless of the increase or decrease in the supply amount of the pulverized biomass fuel,
When pulverizing the biomass fuel, in the case of load operation less than the lowest load operation of the boiler, a rotation speed approximately equal to the rotation speed of the rotary classifier in the operation range of the boiler is used.
Solid fuel grinding method.