Solid fuel pulverizing apparatus and method, and power generation equipment equipped with it.

Abstract

A solid fuel pulverizing apparatus and method, and a power generation device equipped with the same, are disclosed. This solid fuel pulverizing apparatus can supply a boiler with stably pulverized micronized fuel even when using biomass fuel. The solid fuel pulverizing apparatus comprises: a rotary table; a pulverizing roller for pulverizing biomass fuel as solid fuel between the roller and the rotary table; a rotary classifier having multiple blades vertically arranged along a circumferential direction centered on a rotation axis for classifying the pulverized biomass fuel pulverized by the pulverizing roller; an air blower supplying primary air from the rotary table side toward the rotary classifier; and a control unit controlling the primary air supply quantity (A1) supplied from the air blower to be approximately constant within the operating range of the boiler supplied with classified biomass fuel from the rotary classifier.

Description

Technical Field

[0001] This invention relates to a solid fuel pulverizing apparatus suitable for pulverizing biomass fuel, a power generation device equipped with the same, and a solid fuel pulverizing method. Background Technology

[0002] Traditionally, carbonaceous solid fuels such as coal and biomass fuels are pulverized into fine powder smaller than a specified particle size using a grinder (pulverizer) and then supplied to the combustion unit. The grinder pulverizes solid fuels such as coal and biomass fuels fed into a rotating platform by crushing them between the platform and rollers. A classifier then filters the pulverized fuel into fine powder to select the smaller particle size. Primary air, supplied as transport gas (transport gas) from the outer periphery of the rotating platform through pipes, transports the selected small-particle-size fuel to the boiler and where it is burned in the combustion unit. In thermal power generation equipment, steam is generated through heat exchange with the combustion gases produced in the boiler. This steam drives a turbine, thereby generating electricity.

[0003] When using coal as a carbonaceous solid fuel, as shown in Patent Documents 1 and 2, the primary air supply is adjusted according to the coal supply.

[0004] Prior art literature

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2000-130739

[0007] Patent Document 2: Japanese Patent Application Publication No. 2000-140680

[0008] However, as carbon-containing solid fuels, biomass fuels such as wood-based pellets are difficult to grind into finer particles than coal, and have high combustibility, exhibiting the property of being able to burn appropriately even with larger particle sizes. Therefore, when using biomass fuels as solid fuels, they are supplied from the grinder to the combustion unit installed in the boiler in a particle size approximately 5 to 10 times larger than that of finely ground coal.

[0009] Thus, since the particle sizes supplied to the combustion device differ between coal and biomass fuels, the grinding mills used for pulverizing and classifying solid fuels should be designed differently for biomass fuel pulverization and coal pulverization (e.g., shell shape, rotary table speed, classifier speed, etc.), and ideally, they should be designed separately. However, from the perspective of equipment cost and installation space, it is desirable to be able to use the same grinding mill to handle both biomass fuels and coal solid fuels, thereby enabling the use of biomass fuels.

[0010] The transport gas (primary air) supplied to the grinding mill serves to transport and dry the pulverized solid fuel. Coal has a higher moisture content compared to biomass fuels, ranging from high-moisture sub-bituminous coal (approximately 30 wt%) to low-moisture bituminous coal (approximately 10 wt%). Therefore, it is desirable to prioritize dryness during coal pulverization, and the supply rate and temperature of the transport gas (primary air) should be set and controlled according to the type of coal.

[0011] In contrast, the moisture content, particle size, and other properties of biomass fuels differ significantly from those of coal. Compared to coal, pulverized biomass fuels, such as wood-based pellets, have a lower specific gravity and are lighter, but their particle size is larger. Therefore, compared to finely ground coal, pulverized biomass fuel is more difficult to remove from the mill outlet via the blades of a rotary classifier, making it difficult to transport and supply to the combustion unit (burner) of a downstream boiler. Furthermore, pulverized biomass fuel tends to accumulate in gaps and stagnant areas within the mill. Moreover, due to its lower specific gravity, the rotary classifier's rotation speed is typically set slower. Therefore, even if airflow stagnation occurs within the rotary classifier and pulverized biomass fuel accumulates, it is difficult to remove and discharge the accumulated fuel using centrifugal force. On the other hand, the moisture content of biomass fuels, such as wood-based pellets, is usually managed to be lower than that of coal. Therefore, during the pulverization of biomass fuels, transportability of the transport gas (primary air) is prioritized over dryness. Summary of the Invention

[0012] The inventors have discovered that, in the case of pulverizing biomass fuel, it is effective to control the supply and temperature of the transport gas using a different approach than that used for coal.

[0013] The present invention was made in view of the following circumstances, and its object is to provide a solid fuel pulverizing apparatus, a power generation device having the same, and a solid fuel pulverizing method that can supply a stable supply of pulverized micronized fuel to a boiler even when using biomass fuel.

[0014] A solid fuel pulverizing apparatus according to one embodiment of the present invention includes: a rotary table; a pulverizing roller for pulverizing biomass fuel between the pulverizing roller and the rotary table; a rotary classifier for classifying the pulverized biomass fuel obtained by pulverizing the biomass fuel by the pulverizing roller to screen for fine biomass fuel; a transport gas supply unit for supplying transport gas from the rotary table side toward the rotary classifier; and a control unit for controlling the amount of transport gas supplied from the transport gas supply unit to be substantially constant within the operating range of a boiler supplied with the classified fine biomass fuel from the rotary classifier.

[0015] Compared to pulverized coal fuel, pulverized biomass fuel has a larger particle size and lower specific gravity, making it difficult to transport and supply downstream to the boiler via a rotary classifier. Therefore, even at low boiler loads, a specified supply of transport gas (transport gas) is required to ensure the necessary transport force for the pulverized biomass fuel. On the other hand, when pulverized biomass fuel is obtained and classified by the rotary classifier, the biomass fuel undergoes drying during its fuel production process, resulting in a lower moisture content compared to pulverized coal fuel. Therefore, the need for drying using transport gas is less pronounced. Thus, even at high boiler loads, there is no need to increase the transport gas supply to dry the fuel. Therefore, the transport gas supply is controlled to remain approximately constant within the boiler's operating range. This allows for maintaining the transport force of the pulverized biomass fuel within the boiler's operating range and simplifies the control of the transport gas supply.

[0016] The operating range of a boiler refers to the range of operation used during use, such as the range from the boiler operating at its lowest load to operating at overload (e.g., the highest load).

[0017] Furthermore, in a solid fuel pulverizing apparatus according to one embodiment of the present invention, the control unit controls the transport gas supply to be approximately constant in such a way that the ratio of the increase or decrease in the transport gas supply to the increase or decrease in the load of the boiler is ±10% or less.

[0018] When the boiler load changes, the transport gas supply is controlled to be approximately constant, with the percentage change in the transport gas supply before and after the change being ±10% or less. For example, even if the biomass fuel supply increases or decreases corresponding to the boiler load, the transport gas supply is suppressed to an increase or decrease of less than 10% of the initial supply. By keeping the transport gas supply approximately constant, the percentage change in the transport gas supply before and after the change is ±10% or less relative to the increase or decrease in fuel supply caused by the increase or decrease in the boiler's operating range load, resulting in minimal variation in the transport gas supply.

[0019] Furthermore, in a solid fuel pulverizing apparatus according to one embodiment of the present invention, the target value of the transport gas supply controlled by the control unit is determined by the particle size of the micronized biomass fuel required by the combustion device of the boiler.

[0020] In the combustion device (burner) of a boiler, there exists a permissible particle size of finely ground biomass fuel to achieve the desired combustibility. For example, if the particle size is larger than a specified value, the finely ground biomass fuel cannot be completely combusted in the boiler, resulting in unburned portions. On the other hand, even if the particle size is too small, it increases the pressure differential of the grinder and consumes more power, which is uneconomical. Therefore, the target value of the transport gas is determined based on the particle size of the finely ground biomass fuel required by the burner. Specifically, the transport gas supply is determined using the following characteristics: if the transport gas supply is large, finely ground biomass fuel with a larger particle size is supplied to the combustion device; if the transport gas supply is small, finely ground biomass fuel with a smaller particle size is supplied to the burner. Thus, based on the combustion performance of the combustion device, the target value of the transport gas supply that allows the finely ground biomass fuel to combust well in the boiler can be easily determined.

[0021] In addition, the target value for the transport gas supply can also be determined to avoid unstable combustion in the combustion device caused by excess air. For example, when the transport gas supply is set to A (t / h) and the supply of micronized biomass fuel is set to F (t / h), the target value for the transport gas supply can be determined by setting the upper limit of A / F to no more than 2 and no more than 5.

[0022] Furthermore, in a solid fuel pulverizing apparatus according to one embodiment of the present invention, the solid fuel pulverizing apparatus has a biomass fuel pulverizing mode in addition to pulverizing the biomass fuel to supply the micronized biomass fuel, and also has a coal pulverizing mode in which coal is pulverized to supply micronized coal. The control unit switches the amount of transport gas supplied in the biomass fuel pulverizing mode and the amount of transport gas supplied in the coal pulverizing mode.

[0023] In the solid fuel pulverizing apparatus having a coal pulverizing mode that pulverizes coal into fine coal, the amount of transport gas supplied for coal is used when pulverizing coal into fine coal, and the amount of transport gas supplied for biomass fuel is used when pulverizing biomass fuel into fine biomass fuel. Thus, a solid fuel pulverizing apparatus capable of switching between the use of coal and biomass fuel can be provided.

[0024] Furthermore, in a solid fuel pulverizing apparatus according to one embodiment of the present invention, the temperature of the transport gas used by the control unit in the biomass fuel pulverizing mode is lower than the temperature of the transport gas used in the coal pulverizing mode.

[0025] Biomass fuel has a lower moisture content than coal, so there is no need to increase the temperature of the transport gas for drying. Therefore, in biomass fuel pulverization mode, the temperature of the transport gas is kept lower than in coal pulverization mode. This reduces the energy required to heat the transport gas and also lowers the risk of ignition of the biomass fuel within the mill.

[0026] Furthermore, in a solid fuel pulverizing apparatus according to one embodiment of the present invention, when the boiler is operating at its lowest load, the amount of transport gas supplied for the biomass fuel pulverizing mode is greater than the amount of transport gas supplied for the coal pulverizing mode.

[0027] Even at low boiler loads, a specified or higher transport gas supply is required to achieve the transport force needed for the biomass fuel pulverized in the grinder. Therefore, at the boiler's lowest load, the transport gas supply for the biomass fuel pulverization mode is higher than that for the coal pulverization mode. This prevents the accumulation of the lightweight, pulverized biomass fuel in areas where the transport gas stagnates, such as inside the rotary classifier, and thus allows for a more reliable supply to downstream combustion units.

[0028] It should be noted that the amount of transport gas supplied when used in biomass fuel pulverization mode can be greater than that when used in coal pulverization mode, within the entire operating range from minimum load to rated operation or from minimum load to overload operation.

[0029] In addition, a power generation device according to one embodiment of the present invention includes: a solid fuel pulverizing device as described in any of the preceding claims; a boiler that uses the combustion device to burn the solid fuel pulverized by the solid fuel pulverizing device to generate steam; and a power generation unit that uses the steam generated by the boiler to generate electricity.

[0030] In addition, one embodiment of the solid fuel pulverizing method of the present invention uses the following mechanism: a rotary table; a pulverizing roller, which pulverizes biomass fuel as solid fuel between the pulverizing roller and the rotary table; a rotary classifier, which classifies the pulverized biomass fuel obtained by pulverizing the biomass fuel by the pulverizing roller to screen for fine biomass fuel; and a transport gas supply unit, which supplies transport gas from the rotary table side toward the rotary classifier. In the solid fuel pulverizing method, the transport gas supply is controlled to be approximately constant within the operating range of the boiler from which the fine biomass fuel is supplied from the rotary classifier.

[0031] Invention Effects

[0032] By controlling the supply of transport gas to a roughly constant level within the boiler's operating range, a stable supply of finely pulverized fuel can be provided to the boiler even when using biomass fuel. Attached Figure Description

[0033] Figure 1 This is a schematic structural diagram illustrating a power generation device according to one embodiment of the present invention.

[0034] Figure 2 It is a graph showing the primary air supply relative to the fuel supply.

[0035] Figure 3 This is a graph showing the particle size of micronized biomass fuel relative to the primary air supply.

[0036] Figure 4 This is a graph showing the A / F ratio relative to the fuel supply.

[0037] Figure 5 This is a graph showing the rotational speed of the rotary classifier relative to the fuel supply in coal pulverization mode.

[0038] Figure 6 This is a graph showing the rotational speed of the rotary classifier relative to the fuel supply in the biomass fuel pulverization mode.

[0039] Figure 7 This is a graph showing the particle size of micronized biomass fuel relative to the rotational speed of a rotary classifier.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1…Power generation equipment;

[0042] 10…grinding machine;

[0043] 11…outer shell;

[0044] 12… Rotary table;

[0045] 13…roller (crushing roller);

[0046] 14…Drive unit;

[0047] 16… Rotary grading machine;

[0048] 16a…blade;

[0049] 17… Fuel Supply Department;

[0050] 18… motor;

[0051] 19…exports;

[0052] 20…coal feeder;

[0053] 21… silo;

[0054] 22…Transportation Department;

[0055] 23… motor;

[0056] 24… Down spout section;

[0057] 30… Blower section (gas supply section);

[0058] 30a…Hot air blower;

[0059] 30b…Air conditioning blower;

[0060] 30°C…Hot air damper;

[0061] 30d…Air conditioning damper;

[0062] 40… Status Detection Department;

[0063] 41…bottom surface;

[0064] 42…top;

[0065] 45… journal head;

[0066] 47… Support arm;

[0067] 48… Support shaft;

[0068] 49…pressing device;

[0069] 50…Control Department;

[0070] 100… Solid fuel pulverizing device;

[0071] 100a… Primary airflow path;

[0072] 100b…supply path;

[0073] 200… boilers;

[0074] 210…furnace;

[0075] 220…burner (combustion device);

[0076] A… Primary air supply;

[0077] A1…(Primary air supply in biomass fuel pulverization mode);

[0078] A2…(Primary air supply in coal pulverizing mode);

[0079] d1…(target maximum particle size for biomass fuel);

[0080] F... Fuel supply. Detailed Implementation

[0081] Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

[0082] The power generation equipment 1 of this embodiment includes a solid fuel pulverizing device 100 and a boiler 200.

[0083] As an example, the solid fuel pulverizing device 100 is a device that pulverizes solid fuels such as coal and biomass fuel to generate fine fuel and supplies the fine fuel to the burner (combustion device) 220 of the boiler 200. The power generation equipment 1 has one solid fuel pulverizing device 100, but it can also be a system with multiple solid fuel pulverizing devices 100 corresponding to multiple burners 220 of a boiler 200.

[0084] The solid fuel pulverizing device 100 includes a grinder (pulverizing unit) 10, a coal feeder 20, a blower (transport gas supply unit) 30, a status detection unit 40, and a control unit 50.

[0085] It should be noted that in this embodiment, "above" refers to the vertically upper side, and "upper" in terms of upper part, upper surface, etc., refers to the vertically upper part. Similarly, "lower" refers to the vertically lower part.

[0086] The grinding mill 10 grinds coal and biomass fuel, which are supplied to boiler 200, into fine powder. The grinding mill 10 also grinds biomass fuel.

[0087] Here, biomass fuel refers to renewable organic resources derived from living organisms, such as thinned timber, waste wood, driftwood, grass, waste, sludge, tires, and reprocessed fuels (pellets, scrap) that use them as raw materials, and is not limited to the substances shown here. Biomass fuels introduce carbon dioxide during the growth of biomass, thus achieving carbon neutrality without emitting carbon dioxide as a global warming gas; therefore, various studies have been conducted on its utilization.

[0088] The grinding mill 10 includes a housing 11, a rotary table 12, a roller 13 (crushing roller), a drive unit 14, a rotary classifier 16, a fuel supply unit 17, and a motor 18 for driving the rotary classifier 16 to rotate.

[0089] The outer casing 11 is formed into a cylindrical shape extending in the vertical direction and serves as a frame for housing the rotary table 12, roller 13, rotary classifier 16, and fuel supply unit 17.

[0090] A fuel supply unit 17 is installed at the center of the top 42 of the outer casing 11. The fuel supply unit 17 supplies solid fuel introduced from the hopper 21 into the outer casing 11, is arranged vertically at the center of the outer casing 11, and extends into the interior of the outer casing 11 at its lower end.

[0091] A drive unit 14 is provided near the bottom part 41 of the outer casing 11, and a rotary table 12 that rotates under the action of the driving force transmitted from the drive unit 14 is configured to rotate freely.

[0092] The rotary table 12 is a circular component when viewed from above, and is arranged opposite the lower end of the fuel supply section 17. The upper surface of the rotary table 12 may be inclined, for example, with a lower center and a higher outer surface, or it may be bent upwards at the outer periphery. The fuel supply section 17 supplies solid fuel (in this embodiment, for example, coal or biomass fuel) from above to the rotary table 12 below. The rotary table 12 pulverizes the supplied solid fuel between itself and the roller 13, and is therefore also called a pulverizing table.

[0093] When solid fuel is fed from the fuel supply section 17 toward the center of the rotary table 12, the solid fuel is guided to the outer periphery of the rotary table 12 and crushed between it and the roller 13 by the centrifugal force generated by the rotation of the rotary table 12. The crushed solid fuel is swept upward by the transport gas (hereinafter referred to as "primary air") introduced from the transport gas flow path (hereinafter referred to as "primary air flow path") 100a and guided to the rotary classifier 16. That is, multiple outlets (not shown) are provided on the outer periphery of the rotary table 12 to allow the primary air flowing in from the primary air flow path 100a to flow out into the space above the rotary table 12 inside the housing 11. A blade (not shown) is provided above the outlet to apply a swirling force to the primary air blown out from the outlet. The primary air with the swirling force applied by the blade becomes an airflow with a swirling velocity component, which guides the crushed solid fuel on the rotary table 12 toward the rotary classifier 16 above the housing 11. It should be noted that particles larger than the specified particle size in the pulverized solid fuel after primary air mixing are classified by the rotary classifier 16, or fall back to the rotary table 12 before reaching the rotary classifier 16 and are pulverized again.

[0094] Roller 13 is a rotating body that crushes solid fuel supplied from fuel supply unit 17 to rotary table 12. Roller 13 presses against the upper surface of rotary table 12 and works in conjunction with rotary table 12 to crush solid fuel.

[0095] exist Figure 1In this example, only one roller 13 is shown, but multiple rollers 13 can be arranged opposite each other at certain intervals in the circumferential direction by pressing against the upper surface of the rotary table 12. For example, three rollers 13 can be arranged at equal intervals in the circumferential direction by being spaced 120° apart on the outer periphery. In this case, the portions of the three rollers 13 that contact the upper surface of the rotary table 12 (the pressing portions) are equidistant from the rotation center axis of the rotary table 12.

[0096] Roller 13 is supported by journal head 45 and can swing up and down, freely approaching or separating from the upper surface of rotary table 12. When the outer circumferential surface of roller 13 is in contact with the upper surface of rotary table 12, roller 13 rotates in conjunction with the rotary force acting on rotary table 12 as rotary table 12 rotates. When solid fuel is supplied from fuel supply unit 17, the solid fuel is pressed between roller 13 and rotary table 12 and pulverized into fine fuel powder.

[0097] The middle portion of the support arm 47 of the journal head 45 is supported by a support shaft 48 extending horizontally. That is, the support arm 47 is supported by the side portion of the housing 11 so that it can swing about the support shaft 48 in the vertical direction of the roller. In addition, a pressing device 49 is provided at the upper end of the support arm 47 located on the vertical upper side. The pressing device 49 is fixed to the housing 11 and applies load to the roller 13 via the support arm 47, etc., in a manner that presses the roller 13 against the rotary table 12.

[0098] The drive unit 14 is a device that transmits driving force to the rotary table 12 and causes the rotary table 12 to rotate about its central axis. The drive unit 14 generates the driving force that causes the rotary table 12 to rotate.

[0099] A rotary classifier 16 is disposed on the upper part of the housing 11 and has a hollow, generally inverted conical shape. The rotary classifier 16 has multiple blades 16a extending vertically along its outer periphery. Each blade 16a is arranged side-by-side at predetermined intervals (equal intervals) around the central axis of the rotary classifier 16. Furthermore, the rotary classifier 16 is a device for classifying solid fuel pulverized by the roller 13 into solid fuels larger than a predetermined particle size (e.g., 70–100 μm for coal, 0.6–1.0 mm for biomass fuel) (hereinafter, pulverized solid fuel exceeding the predetermined particle size is referred to as "coarse fuel") and solid fuels smaller than the predetermined particle size (hereinafter, solid fuel pulverized to a predetermined particle size is referred to as "fine fuel"). The rotary classifier 16 is driven by a motor 18 controlled by the control unit 50.

[0100] After the solid fuel reaches the rotary classifier 16, due to the relative balance between the centrifugal force generated by the rotation of the blades 16a and the centripetal force generated by the primary airflow, the large-diameter coarse fuel is knocked off by the blades 16a and returned to the rotary table 12 to be crushed again, while the fine fuel is introduced into the outlet 19 located at the top 42 of the outer casing 11.

[0101] The fine fuel, after being classified by the rotary classifier 16, is discharged from outlet 19 into supply path 100b and transported to the next process along with primary air. The fine fuel flowing out of supply path 100b is supplied to burner 220 of boiler 200.

[0102] The fuel supply unit 17 is installed at its lower end, extending vertically into the interior of the housing 11 through the upper end. Solid fuel introduced from the upper part of the fuel supply unit 17 is supplied to approximately the central region of the rotary table 12. Solid fuel is supplied to the fuel supply unit 17 from the coal feeder 20.

[0103] The coal feeder 20 includes a hopper 21, a conveying unit 22, and a motor 23. The conveying unit 22 uses the driving force applied from the motor 23 to convey solid fuel discharged from the lower end of the feed pipe 24 located directly below the hopper 21. The solid fuel conveyed by the conveying unit 22 is introduced into the fuel supply unit 17 of the mill 10.

[0104] Typically, inside the grinder 10, the pressure is higher than atmospheric pressure because primary air is supplied to transport the pulverized solid fuel, i.e., micronized fuel. In the feed pipe 24, which extends vertically directly below the hopper 21, the fuel is held in a stacked state. This stacked layer of solid fuel within the feed pipe 24 ensures a tight seal, preventing backflow of primary air and pulverized fuel from the grinder 10 side. The amount of solid fuel supplied to the grinder 10 can also be adjusted by the belt speed of the conveyor belt in the transport unit 22, controlled by the motor 23 controlled by the control unit 50.

[0105] Compared to coal fuel (i.e., coal with a particle size of 2-50 mm before pulverization), the biomass fuel fragments and pellets before pulverization have a constant particle size (particle size of 6-8 mm in diameter and less than 40 mm in length) and are lighter. Therefore, when biomass fuel is stored in the feed pipe section 24, the gaps formed between each piece of biomass fuel are larger compared to the case of coal fuel.

[0106] Therefore, gaps exist between the biomass fuel fragments and pellets within the feed pipe section 24. This can cause the pressure inside the mill 10 to decrease due to the primary air and fine fuel being blown up from within the mill 10, as these gaps between the biomass fuels can be filled. Furthermore, when primary air is blown into the storage section of the hopper 21, various problems may arise during mill 10 operation, such as a decrease in the amount of fine fuel transported, dust generation, ignition of the feed pipe section 24, or a decrease in pressure if the biomass fuel is blown into the storage section 24. Therefore, a rotary valve (not shown) can be installed midway between the coal feeder 20 and the fuel supply section 17 to suppress backflow caused by the blowing of primary air and fine fuel.

[0107] The blower 30 is a device that blows primary air into the interior of the housing 11. This primary air is used to dry the solid fuel pulverized by the roller 13 and supply it to the rotary classifier 16.

[0108] The blower section 30 is equipped with a hot air blower 30a, a cold air blower 30b, a hot air damper 30c, and a cold air damper 30d to adjust the primary air blown to the outer casing 11 to an appropriate temperature.

[0109] The hot air blower 30a is a blower that blows heated primary air supplied from heat exchangers such as air preheaters. A hot air damper 30c is provided downstream of the hot air blower 30a. The opening degree of the hot air damper 30c is controlled by the control unit 50. The flow rate of primary air blown by the hot air blower 30a is determined according to the opening degree of the hot air damper 30c.

[0110] Air conditioning blower 30b is a blower that blows primary air, which is external gas at room temperature. An air conditioning damper 30d is provided downstream of air conditioning blower 30b. The opening degree of air conditioning damper 30d is controlled by control unit 50. The flow rate of primary air blown by air conditioning blower 30b is determined according to the opening degree of air conditioning damper 30d.

[0111] The primary air flow rate is the sum of the primary air flow rate blown by the hot air blower 30a and the primary air flow rate blown by the cold air blower 30b. The temperature of the primary air is determined by the mixing ratio of the primary air blown by the hot air blower 30a and the primary air blown by the cold air blower 30b, and is controlled by the control unit 50.

[0112] Alternatively, a portion of the combustion gas discharged from the boiler 200, which has passed through environmental devices such as an electrostatic precipitator via a gas recirculation fan, can be introduced into the primary air blown by the hot air blower 30a to form a mixed gas, thereby adjusting the oxygen concentration of the primary air flowing in from the primary air flow path 100a.

[0113] In this embodiment, the state detection unit 40 of the outer casing 11 sends measured or detected data to the control unit 50. The state detection unit 40 in this embodiment is, for example, a differential pressure measurement unit, which measures the pressure difference within the mill 10 as the pressure difference between the portion of primary air flowing into the mill 10 from the primary air flow path 100a and the outlet 19 from the mill 10, which discharges primary air and fine fuel from the supply flow path 100b. For example, based on the classification performance of the rotary classifier 16, the increase or decrease in the circulation amount of the pulverized solid fuel circulating between the vicinity of the rotary classifier 16 and the vicinity of the rotary table 12 within the mill 10, and the corresponding increase or decrease in the pressure difference within the mill 10, can be adjusted and managed for the solid fuel supplied to the mill 10. Therefore, a greater amount of fine fuel can be supplied to the burner 220 of the boiler 200 within a range where the particle size of the fine fuel does not affect the combustibility of the burner 220.

[0114] Furthermore, in this embodiment, the state detection unit 40 is, for example, a temperature measurement unit. It detects the temperature of the primary air, which has been temperature-adjusted by the blower unit 30, within the housing 11, and controls the blower unit 30 to ensure that the temperature does not exceed the upper limit. This blower unit 30 blows primary air into the interior of the housing 11 to supply the solid fuel pulverized by the roller 13 to the rotary classifier 16. It should be noted that the primary air is dried and transported within the housing 11, thereby being cooled. Therefore, the temperature of the upper space of the housing 11 is, for example, approximately 60 to 80°C.

[0115] The control unit 50 is a device that controls various parts of the solid fuel pulverizing apparatus 100. For example, the control unit 50 can control the rotational speed of the rotary table 12 relative to the mill 10 by transmitting a drive instruction to the drive unit 14. For example, the control unit 50 can adjust the classification performance by transmitting a drive instruction to the motor 18 of the rotary classifier 16 and controlling its rotational speed, thereby rationalizing the pressure difference within the mill 10 and stabilizing the supply of fine fuel. Furthermore, for example, the control unit 50 can adjust the amount of solid fuel supplied to the fuel supply unit 17 by the conveying unit 22 transporting solid fuel by transmitting a drive instruction to the motor 23 of the coal feeder 20. Additionally, the control unit 50 can control the opening degree of the hot air damper 30c and the cold air damper 30d by transmitting an opening degree instruction to the blower unit 30, thereby controlling the flow rate and temperature of the primary air.

[0116] The control unit 50 is composed of, for example, a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), and a computer-readable storage medium. Furthermore, a series of processes for implementing various functions are stored as programs in the storage medium, etc. The CPU reads the program from RAM, etc., and performs information processing and arithmetic to achieve various functions. It should be noted that the program can also be pre-installed in ROM, other storage media, provided in a state stored in a computer-readable storage medium, or distributed via a wired or wireless communication unit. Computer-readable storage media refers to disks, optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, etc.

[0117] Next, a boiler 200 that generates steam by burning micronized fuel supplied from a solid fuel pulverizer 100 will be described.

[0118] Boiler 200 is equipped with furnace 210 and burner 220.

[0119] The burner 220 is a device that uses primary air (in this embodiment, pulverized coal or pulverized biomass fuel) supplied from the supply flow path 100b and secondary air supplied from a heat exchanger (not shown) to combust the pulverized fuel to form a flame. The combustion of the pulverized fuel takes place inside the furnace 210, and the high-temperature combustion gases are discharged to the outside of the boiler 200 after passing through heat exchangers such as evaporators, superheaters, and economizers (not shown).

[0120] Combustion gases discharged from boiler 200 undergo prescribed treatment in environmental devices (denitrification unit, electrostatic precipitator, etc., not shown in the diagram), and exchange heat with external gases in heat exchangers such as air preheaters (not shown in the diagram), and are then directed to a chimney (not shown in the diagram) via an induced draft fan (not shown in the diagram) and released into the atmosphere. In the heat exchanger, the external gases heated by heat exchange with the combustion gases are transported to the aforementioned hot air blower 30a.

[0121] The water supplied to each heat exchanger of 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, which is then fed to a steam turbine (not shown) that serves as a power generation unit to drive a generator (not shown) to rotate and generate electricity.

[0122] [Control of primary air supply]

[0123] Next, the control of the primary air supply (transport gas supply) A supplied from the blower 30 to the grinder 10 will be explained. The control of the primary air supply A is based on the control unit 50... Figure 2 The control unit 50 switches and controls the operation of the grinder 10 to a coal grinding mode, which mainly grinds coal as solid fuel supplied to the grinder 10 and supplies fine coal to the burner 220, and a biomass fuel grinding mode, which mainly grinds biomass fuel as solid fuel supplied to the grinder 10 and supplies fine biomass fuel to the burner 220.

[0124] Figure 2 The graph shows the primary air supply A for both the coal pulverizing mode and the biomass fuel pulverizing mode. In this graph, the horizontal axis represents the fuel supply F (weight flow rate), and the vertical axis represents the primary air supply A (weight flow rate).

[0125] On the horizontal axis, the fuel supply quantity F is standardized with 1.0 as the rated operating value of boiler 200. Furthermore, as an example, the fuel supply quantity F for boiler 200's minimum load operation is set to 0.4, and the fuel supply quantity F for boiler 200's overload operation is set to 1.25. Therefore, the operating range of boiler 200 is above 0.4 and below 1.25. It should be noted that the values ​​for boiler 200's minimum load operation and overload operation are merely examples, and various settings can be made for different boilers.

[0126] On the vertical axis, the primary air supply A1 during the lowest load operation in biomass fuel pulverization mode is set to 1.0, thereby standardizing the primary air supply A.

[0127] <Coal Crushing Mode>

[0128] Regarding the primary air supply A2 in the coal pulverizing mode, such as Figure 2 As shown by the dashed line, for example, in the region where the fuel supply F is less than 0.4 when operating at minimum load, it is kept constant at 0.65. It should be noted that the value of 0.65 for the primary air supply A2 is merely an example, meaning it is less than the primary air supply A1 (i.e., 1.0) in the biomass fuel pulverization mode. It should also be noted that within the operating range from minimum load to rated operation, or throughout the entire operating range from minimum load to overload operation, the primary air supply A1 for biomass fuel pulverization mode can be set to be greater than the primary air supply A2 for coal pulverization mode.

[0129] If the fuel supply F during minimum load operation is 0.4 or higher, then the primary air supply A2 in coal pulverizing mode increases to 1.25 during overload operation, for example... Figure 2The increase is monotonically as shown. This takes into account both the dryness of dry coal and the transportability of transportable coal. That is, since the moisture content of coal is higher than that of biomass fuels such as wood-based pellets, when the fuel supply F increases, the primary air volume needs to be increased to achieve dryness in order to increase the heat of gasification. In addition, when the fuel supply F increases, the primary air volume needs to be increased to achieve transportability.

[0130] By controlling the hot air damper 30c and the cold air damper 30d (see reference) Figure 1 This is controlled to adjust the temperature of the primary air near the outlet of the primary air flow path 100a in the coal crushing mode to be above 150°C and below 350°C.

[0131] <Biomas Fuel Pulverization Mode>

[0132] Regarding the primary air supply A1 in the biomass fuel pulverization mode, such as Figure 2 As shown by the solid line, the value is approximately constant at 1.0 throughout the entire operating range of boiler 200, from 0.4 for minimum load operation to 1.25 for overload operation. The reason for this is as follows.

[0133] Compared to pulverized coal fuel, the pulverized biomass fuel has a larger particle size, making it difficult to pass through the blades 16a of the rotary classifier 16. Therefore, it is difficult to discharge from the outlet 19 and transport it to the burner 220 via the rotary classifier 16. Furthermore, the pulverized biomass fuel tends to accumulate in the gaps and stagnant areas of the airflow inside the mill 10. Also, due to its low specific gravity and the slow rotation speed of the rotary classifier 16, areas of primary air stagnation are created within the rotary classifier 16. Even if the pulverized biomass fuel accumulates within the rotary classifier 16, it is difficult to remove and discharge it through the centrifugal force of the rotary classifier 16. Therefore, it is necessary to prevent the formation of areas of primary air stagnation, i.e., to ensure sufficient primary air flow, i.e., transport capacity. Even when the boiler 200 is operating at its lowest load, a primary air supply of at least a specified value A1 is required to ensure the transport capacity needed to transport the pulverized biomass fuel. On the other hand, biomass fuel has a lower moisture content than pulverized coal fuel, so there is less need for drying with primary air. Therefore, even if boiler 200 is operating at high loads such as rated operation, there is no need to increase the primary air supply A1 to dry the moisture in the fuel.

[0134] It should be noted that the primary air supply A1 only needs to be approximately constant, or it does not need to be strictly constant. Here, approximately constant means, for example, that the percentage change in the primary air supply A1 relative to the change in the fuel supply F corresponding to the increase or decrease in the load of boiler 200 is within ±10%.

[0135] By controlling the hot air damper 30c and the cold air damper 30d (see reference) Figure 1 The temperature of the primary air in biomass fuel pulverization mode is controlled to be lower than that in coal pulverization mode, for example, adjusted to be above 100°C but below 150°C. The upper limit temperature is set to not exceed 200°C. This is because if the temperature exceeds 200°C, the biomass fuel may ignite. It should be noted that, for example, the moisture content of wood-based pellet biomass fuel is dried during manufacturing to prevent fermentation, etc., and is approximately 15% or less.

[0136] The primary air supply A1 in biomass fuel pulverization mode is as follows: Figure 3 As shown, the target particle size is determined through static characteristic tests during trial operation. Specifically, it is determined by the particle size of the micronized biomass fuel required by the burner 220 of the boiler 200. The target particle size d1 of the micronized biomass fuel is determined, for example, considering the following conditions. If the particle size of the micronized biomass fuel increases due to the combustibility of the burner 220, the unburned portion in the burner 220 may increase. On the other hand, in order to improve the combustibility of the micronized biomass fuel and reduce its particle size, it is necessary, for example, to increase the pressing pressure on the biomass fuel between the roller 13 and the rotary table 12, which increases the rotational power of the rotary table 12 required for pulverization and reduces efficiency. Therefore, the target particle size d1 of the micronized biomass fuel is set, for example, to about 0.6 mm to 1 mm.

[0137] exist Figure 3 In the figure, the horizontal axis represents the primary air supply A1, and the vertical axis represents the particle size of the fine biomass fuel transported from the mill 10 toward the burner 220.

[0138] like Figure 3 As shown, the target particle size d1 is determined by the combustibility of the burner 220 and the rotational power of the rotary table 12 required for pulverization. Furthermore, regarding the particle size of the transported micro-powdered biomass fuel, as the primary air supply A1 increases, the transport force increases, thus increasing the transported particle size. Conversely, as the primary air supply A1 decreases, the transport force decreases, thus decreasing the transported particle size. Therefore, by increasing or decreasing the primary air supply A1, a primary air supply A1 corresponding to the target particle size d1 can be obtained.

[0139] In the static characteristic tests during trial operation, such as Figure 4 As shown, the A / F (primary air supply / fuel supply) ratio was also studied.

[0140] Figure 4 The graph illustrates the relationship between A / F and fuel supply F. In this graph, the solid line represents the biomass fuel pulverization mode, and the dashed line represents the coal pulverization mode.

[0141] As shown in the figure, in both the coal pulverizing mode and the biomass fuel pulverizing mode, A / F decreases as the fuel supply F increases. However, as... Figure 2 As shown, the primary air supply A in the biomass fuel pulverization mode is greater than that in the coal pulverization mode. Therefore, when comparing the same fuel supply F, the A / F ratio is greater in the biomass fuel pulverization mode than in the coal pulverization mode.

[0142] When the air-to-fuel ratio (A / F) increases, there may be excess air in the burner 220, potentially disrupting stable combustion. Therefore, the primary air supply A1 for the biomass fuel pulverization mode is set such that the A / F at the lowest load operating rate F (=0.4) of the boiler 200, which operates in lean combustion mode, does not exceed the upper limit. The upper limit of the A / F at the fuel supply rate F (=0.4) is determined by the combustibility of the burner 220, and is, for example, above 2 and below 5. Furthermore, the primary air supply A1 is set to a flow rate that, even when the biomass fuel supply is at its maximum during overload operation, will not cause the pulverized biomass fuel to remain in the mill 10, but rather allows the finely pulverized biomass fuel to be transported from the mill 10 to the burner 220. For example, as... Figure 2 As shown, the primary air supply A1 of the biomass fuel pulverizing mode is set to be greater than the primary air supply A2 of the coal pulverizing mode when the coal pulverizing mode is in rated operation. When the coal pulverizing mode is in overload operation, the primary air supply A1 of the biomass fuel pulverizing mode is set to be the same as the primary air supply A2 of the coal pulverizing mode.

[0143] [Spindle speed control of rotary classifier 16]

[0144] Next, the control of the rotational speed of the rotary classifier 16 will be explained. The rotational speed of the rotary classifier 16 is controlled by the control unit 50. When the grinding mill 10 is in operation, the control unit 50 switches and controls the coal crushing mode and the biomass fuel crushing mode.

[0145] The rotational speed of the rotary classifier 16 is controlled by a second adjustment after the first adjustment is made through the control of the primary air supply A mentioned above. The control of the primary air supply A is set to take priority over the rotational speed control of the rotary classifier 16 because the primary air supply A directly affects the combustion performance of the burner 220 of the boiler 200.

[0146] <Coal Crushing Mode>

[0147] Figure 5 The rotational speed control of the rotary classifier 16 in coal pulverization mode is shown. The horizontal axis represents the fuel (coal) supply F, and the vertical axis represents the rotational speed of the rotary classifier 16.

[0148] On the horizontal axis, the fuel supply quantity F is standardized with 1.0 as the rated operating value of boiler 200. Furthermore, as an example, the fuel supply quantity F for boiler 200's minimum load operation is set to 0.4, and the fuel supply quantity F for boiler 200's overload operation is set to 1.25. Therefore, the operating range of boiler 200 is above 0.4 and below 1.25. It should be noted that the values ​​for boiler 200's minimum load operation and overload operation are merely examples, and various settings can be made for different boilers.

[0149] On the vertical axis, the rotational speed of the rotary classifier 16 during the lowest load operation of the boiler 200 in the biomass fuel pulverization mode (described later) is standardized to 1.0.

[0150] The rotational speed of the rotary classifier 16 in coal pulverization mode is set to supply fine-grained coal to promote the classification of fine and coarse coal, thereby ensuring the combustibility of the burner 220. Therefore, the rotational speed of the rotary classifier 16 in coal pulverization mode is set higher than that in biomass fuel pulverization mode (1.0). At 0.4 hours of operation with the fuel supply ratio F as the minimum load, the rotational speed of the rotary classifier 16 is approximately 5.0. As the load increases to 0.4 hours of operation as the minimum load, the speed rises to 8.0. The reason for increasing the rotational speed of the rotary classifier 16 from this low-load side to the minimum load is as follows.

[0151] That is, when operating under a load lower than the minimum load, if the coal is pulverized at the same speed (8.0) as when operating under a load higher than the minimum load, the coal pulverized into a size too fine to pass through the mill 10 of the rotary classifier 16 becomes too fine. The carbon contained in the coal acts as an individual lubricant, reducing friction. This is because the roller 13 may slide relative to the rotary table 12, causing vibration and preventing the desired pulverization. Therefore, in coal pulverization mode, the speed of the rotary classifier 16 is reduced to a speed of approximately 5.0 when operating under a load lower than the minimum load.

[0152] The rotational speed of the rotary classifier 16 is approximately constant at 8.0, ranging from 0.4 to about 1.1, which is more than 1.0 for rated operation.

[0153] In addition, such as Figure 2 As shown, when the fuel supply F increases, the transportability of the pulverized coal increases by increasing the primary air supply A2. Therefore, the pulverized coal fuel supplied to the burner 220 becomes a specified particle size (capable of being graded). In the range of fuel supply F from 0.4 to 1.1, which is more than 1.0 for rated operation, the rotational speed of the rotary classifier 16 is gradually increased in accordance with the increase of primary air supply A2, which can also suppress the increase of coarse powder in the pulverized coal fuel supplied to the burner 220.

[0154] The upper limit of the fuel supply quantity F is set to exceed 1.1 times the rated operating value, but it can also be set to 1.0 times the rated operating value, depending on the application.

[0155] The rotational speed of the rotary classifier 16 is determined during static characteristic tests during trial operation by selecting an appropriate speed that ensures stable combustion in the burner 220 of the boiler 200, based on the particle size and flow rate of the pulverized coal supplied from the outlet of the mill 10 to the burner 220. For example, the rotational speed of the rotary classifier 16 is between 90 rpm and 180 rpm. It should be noted that the rotational speed of the rotary classifier 16 can also be gradually increased as the fuel supply F increases.

[0156] During overload operation, where the fuel supply F exceeds the rated operating speed by 1.1 to 1.25, the rotational speed of the rotary classifier 16 decreases as the fuel supply F increases, not as a fixed speed as indicated by the dashed line, but as shown by the solid line. This is because, as the fuel supply F increases, the rotational power of the rotary table 12 of the mill 10 increases, but does not exceed the power specification limit of the mill 10. That is, as the fuel supply F increases, the amount of coarse fuel classified by the rotary classifier 16 increases, and the amount of coarse fuel falling onto the rotary table 12 increases. As a result, the power of the rotary table 12 increases, approaching the power limit for operating and managing the mill 10, thus reducing the rotational speed of the rotary classifier 16. Consequently, the coarse fuel is also transported downstream to the burner 220 via the rotary classifier 16, suppressing the increase in the amount of coarse fuel falling onto the rotary table 12. On the other hand, since the permissible level of coarse fuel exceeds the level required to maintain the combustibility of the burner 220, the combustibility decreases. Combustion is achieved by increasing the amount of coarse fuel in burner 220. Sometimes the combustibility in burner 220 is slightly reduced, but since the frequency of overload operation of fuel supply F from 1.1 to 1.25 above the rated operating value is low and short, it has almost no impact on the power generation equipment 1, and the power limitation of the grinder 10 can be managed preferentially.

[0157] <Biomas Fuel Pulverization Mode>

[0158] Figure 6The rotational speed control of the rotary classifier 16 in biomass fuel pulverization mode is shown. The horizontal and vertical axes are... Figure 5 same.

[0159] like Figure 6 As shown, in the biomass fuel pulverization mode, the rotational speed of the rotary classifier 16 is approximately constant at 1.0 within the range of fuel supply F, which ranges from 0.4 (minimum load) to 1.25 (overload). This is because the pulverized biomass fuel has a larger particle size compared to pulverized coal, making it difficult to pass between the blades 16a of the rotary classifier 16. Therefore, the rotational speed of the rotary classifier 16 is set relatively low. Furthermore, due to its low specific gravity, fuel accumulated in the stagnant airflow area experiences insufficient centrifugal force even when subjected to centrifugal force by the rotary classifier 16, making it difficult to remove or discharge from the rotary classifier 16. Consequently, it tends to stagnate and accumulate within the rotary classifier, making it difficult to pass from the mill 10 through the rotary classifier 16 and exit from the outlet 19. Therefore, when the load on the boiler 200 increases, leading to an increase in the amount of biomass fuel input, increasing the rotation speed of the rotary classifier 16 to promote coarse particle classification will not result in a corresponding increase in the amount of fine biomass fuel supplied from the rotary classifier 16 to the boiler 200. Instead, the density of coarse biomass fuel particles dislodged by the rotary classifier 16 inside the mill 10 may increase, only increasing the load on the mill 10. Furthermore, the rotation speed of the rotary classifier 16 in biomass fuel pulverization mode is low, making it difficult to effectively control its speed from 0.1 rpm to the 1 rpm level. Therefore, even with an increase in the load on the boiler 200, the rotary classifier 16 is operated at approximately a constant speed while supplying fine biomass fuel corresponding to the increased load on the boiler 200.

[0160] Figure 6 In the middle, on the vertical axis, the rotation speed of the rotary classifier 16 when the boiler 200 is operating at the lowest load in the biomass fuel pulverization mode is selected as the minimum speed, so the rotation speed of the rotary classifier 16 when operating at the lowest load is set to 1.0 and standardized.

[0161] Here, "approximately constant" means, for example, that the change in the fuel supply F corresponding to the increase or decrease in the load of the boiler 200 is within ±10% of the change in the rotational speed of the rotary classifier 16. Depending on the control precision of the rotational speed, the approximately constant speed can also be within ±1 rpm of the rotational speed of the rotary classifier 16 when operating at the lowest load. That is, the rotational speed of the rotary classifier 16 in biomass fuel pulverization mode is approximately constant within ±1 rpm, with a central value, for example, between 10 rpm and 30 rpm. Furthermore, the rotational speed of the rotary classifier 16 in biomass fuel pulverization mode is lower than that in coal pulverization mode. This is because the pulverized biomass fuel has a larger particle size compared to pulverized coal, making it difficult to pass between the blades 16a of the rotary classifier 16. Additionally, the pulverized biomass fuel is lighter than pulverized coal, therefore the centrifugal force exerted on the pulverized biomass fuel by the rotation of the blades 16a of the rotary classifier 16 is smaller. Therefore, the centripetal force generated by the primary airflow increases, and fine powder, including coarse powder of pulverized biomass fuel, easily enters the rotary classifier 16 through the space between the blades 16a. If there is stagnation of the primary airflow within the rotary classifier 16, the fine powder, including coarse powder of pulverized biomass fuel, will be retained. However, the centrifugal force acting on the fine powder is relatively small, so it accumulates within the rotary classifier 16 and is difficult to discharge, making it difficult to pass through the mill 10 and be supplied to the burner 220 from the outlet 19. Therefore, reducing the rotational speed of the rotary classifier 16 eliminates stagnation of the primary airflow in a manner that does not impede the flow of primary air, thus promoting primary air-based transport.

[0162] In the biomass fuel pulverization mode, compared with the coal pulverization mode (see reference) Figure 5 Unlike the minimum load, when the load is smaller than the minimum load, the rotation speed of the rotary classifier 16 is not reduced, but approximately the same speed is used. This is because, in the case of biomass fuel, it will not be ground too finely as in coal, and the possibility of the roller 13 sliding relative to the rotary table 12 is small, similar to that in coal.

[0163] Figure 7 The figure illustrates a method for determining a constant rotational speed of the rotary classifier 16 in a biomass fuel pulverization mode. In this figure, the horizontal axis represents the rotational speed of the rotary classifier 16, and the vertical axis represents the particle size of the fine fuel transported by the rotary classifier 16.

[0164] The rotational speed of the rotary classifier 16 is determined by the target particle size of the micronized biomass fuel required by the burner 220 of the boiler 200. Regarding the target particle size of the micronized biomass fuel, if the particle size increases due to the combustibility of the burner 220, the unburned portion in the burner 220 increases; if the particle size decreases, the pressure difference and power consumption of the mill 10 increase. Therefore, the rotational speed is determined taking these factors into account. If the target particle size (1.0) of the micronized fuel is determined, the rotational speed of the rotary classifier 16 is adjusted to meet this target particle size. Specifically, as... Figure 7 As shown, increasing the rotational speed of the rotary classifier 16 reduces the particle size of the micronized biomass fuel transported to the next process along with the primary air, while decreasing the rotational speed of the rotary classifier 16 increases the particle size. Using this characteristic, the rotational speed of the rotary classifier 16 is determined to be an appropriate value (1.0). In this embodiment, for example, the target particle size of the micronized biomass fuel is set to approximately 0.6 mm to 1 mm.

[0165] According to this embodiment, the following effects are achieved.

[0166] The pulverized biomass fuel has a larger particle size than pulverized coal fuel, making it difficult to pass between the blades 16a of the rotary classifier 16. Furthermore, its lower specific gravity and lighter weight mean that in areas where the gas flow temporarily enters the rotary classifier 16 and is being transported, the centrifugal force on the pulverized biomass fuel is small, making it difficult to accumulate and discharge. Therefore, it is difficult to transport and supply the pulverized biomass fuel to the downstream burner 220 via the rotary classifier 16. Therefore, even at low boiler loads, a primary air supply A1 of a specified value or higher is required to ensure the desired transport capacity of the pulverized biomass fuel. On the other hand, when pulverized biomass fuel is obtained and classified by the rotary classifier 16, the biomass fuel undergoes drying during its fuel production process, resulting in a lower moisture content compared to pulverized coal fuel, thus reducing the need for drying with primary air. Therefore, even at high boiler loads, it is not necessary to increase the primary air supply A1 to dry the moisture in the fuel. Therefore, within the operating range of boiler 200, the primary air supply A1 is controlled to be approximately constant. This allows for the maintenance of the transport capacity of the pulverized biomass fuel within the operating range of boiler 200, and also enables easy control of the primary air supply A1.

[0167] The burner 220 of boiler 200 contains a particle size of fine biomass fuel that is permissible for achieving the desired combustibility. For example, if the particle size is larger than a specified value, the fine biomass fuel cannot be completely combusted within boiler 200, resulting in unburned portions. Therefore, as... Figure 3As shown, the target value of the primary air supply A1 is determined based on the particle size of the micronized biomass fuel required by the burner 220. Therefore, based on the combustion performance of the burner 220, the target value of the primary air supply A1 that enables good combustion of the micronized biomass fuel within the boiler 200 can be easily determined.

[0168] When pulverizing coal into fine coal, the primary air supply A2 for coal is used, and when pulverizing biomass fuel into fine biomass fuel, the primary air supply A1 for biomass fuel is used. Thus, a solid fuel pulverizing device 100 that can switch between using coal and biomass fuel can be provided.

[0169] Biomass fuel has a lower moisture content than coal, so there is no need to raise the temperature of the primary air for drying. Therefore, in the biomass fuel grinding mode, the primary air temperature is lower than in the coal grinding mode. This reduces the energy required to heat the primary air and lowers the risk of ignition of the biomass fuel inside the grinder 10.

[0170] Even at low loads on boiler 200, a primary air supply A1 of at least a specified value is required to achieve the necessary transport force for the biomass fuel pulverized within mill 10. Therefore, at the lowest load on boiler 200, the primary air supply A1 used in biomass fuel pulverization mode is greater than the primary air supply A2 used in coal pulverization mode. This prevents the accumulation of the lightweight, pulverized biomass fuel in areas where primary air flow is stagnant, such as inside rotary classifier 16, and thus ensures a more reliable supply to downstream burner 220.

Claims

1. A solid fuel pulverizing device for supplying micronized biomass fuel to a boiler, wherein, The solid fuel pulverizing device includes a pulverizing section, a conveying gas supply section, and a control section. The pulverizing unit includes: a rotary table; a fuel supply unit that supplies biomass fuel as solid fuel to the rotary table; a pulverizing roller that pulverizes the biomass fuel between the pulverizing roller and the rotary table; and a rotary classifier that classifies the biomass fuel pulverized by the pulverizing roller to screen the micronized biomass fuel. The transport gas supply unit supplies transport gas from the rotary table side toward the rotary classifier. The control unit controls the amount of biomass fuel supplied from the fuel supply unit and the amount of transport gas supplied from the transport gas supply unit. The control unit controls the transport gas supply to be approximately constant relative to changes in the biomass fuel supply within the operating range of the boiler, from minimum load to maximum load. Furthermore, the transport gas supply is controlled to a flow rate that, even when the biomass fuel supply is at its maximum, prevents the pulverized biomass fuel from becoming trapped in the pulverizing section and allows it to be transported from the pulverizing section to the boiler. In addition to a biomass fuel pulverizing mode for pulverizing biomass fuel to supply micro-biomass fuel, the solid fuel pulverizing device also has a coal pulverizing mode for pulverizing coal to supply micro-coal. The control unit switches the transport gas supply for the biomass fuel pulverizing mode and the transport gas supply for the coal pulverizing mode. When the boiler is operating at its minimum load and rated load, the control unit provides a greater amount of transport gas for the biomass fuel pulverization mode than for the coal pulverization mode. When the boiler is operating at overload, the amount of transport gas provided for the biomass fuel pulverization mode is the same as or greater than the amount of transport gas provided for the coal pulverization mode.

2. The solid fuel pulverizing device according to claim 1, wherein, The control unit controls the transport gas supply for the biomass fuel pulverization mode to be approximately constant in such a way that the increase or decrease in the amount of transport gas supplied during the biomass fuel pulverization mode is relative to the increase or decrease in the load of the boiler by less than ±10%.

3. The solid fuel pulverizing device according to claim 1 or 2, wherein, The target value of the transport gas supply for the biomass fuel pulverization mode, controlled by the control unit, is determined by the particle size of the micronized biomass fuel required by the boiler's combustion device.

4. The solid fuel pulverizing device according to claim 1 or 2, wherein, The temperature of the transport gas used by the control unit in the biomass fuel pulverization mode is lower than the temperature of the transport gas used in the coal pulverization mode.

5. A power generation device, wherein, The power generation equipment includes: The solid fuel pulverizing apparatus according to any one of claims 1 to 4; The boiler uses a combustion device to burn solid fuel pulverized by the solid fuel pulverizing device to generate steam. as well as The power generation unit uses the steam generated by the boiler to generate electricity.

6. A method for pulverizing solid fuel, comprising a solid fuel pulverizing device that supplies finely powdered biomass fuel to a boiler, and including a pulverizing section and a conveying gas supply section. The pulverizing unit includes: a rotary table; a fuel supply unit that supplies biomass fuel as solid fuel to the rotary table; a pulverizing roller that pulverizes the biomass fuel between the pulverizing roller and the rotary table; and a rotary classifier that classifies the biomass fuel pulverized by the pulverizing roller to screen the micronized biomass fuel. The transport gas supply unit supplies transport gas from the rotary table side toward the rotary classifier. In the solid fuel pulverization method, The biomass fuel supply from the fuel supply unit and the transport gas supply from the transport gas supply unit are controlled. The transport gas supply is controlled to be approximately constant relative to changes in the biomass fuel supply within the boiler's operating range from minimum load to maximum load. Furthermore, the transport gas supply is controlled to a flow rate that, even when the biomass fuel supply is at its maximum, prevents the pulverized biomass fuel from becoming trapped in the pulverizing section and allows it to be transported from the pulverizing section to the boiler. In addition to a biomass fuel pulverizing mode for pulverizing biomass fuel to supply micro-biomass fuel, the solid fuel pulverizing device also has a coal pulverizing mode for pulverizing coal to supply micro-coal. In the solid fuel pulverization method, The transport gas supply is switched between the biomass fuel pulverization mode and the coal pulverization mode. When the boiler is operating at its minimum load and at its rated load, the amount of transport gas supplied in the biomass fuel pulverization mode is greater than the amount of transport gas supplied in the coal pulverization mode. When the boiler is operating at overload, the amount of transport gas supplied in the biomass fuel pulverization mode is the same as or greater than the amount of transport gas supplied in the coal pulverization mode.

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