Solid fuel pulverizer, power generation plant, and method for operating the solid fuel pulverizer

Abstract

To inhibit deterioration of controllability of a cold gas damper and control a carrier gas preferably.SOLUTION: A solid fuel crushing device 100 includes: a crushing machine 60 which crushes a solid fuel; a blower part 30 which has a cold gas passage 30b in which a cold gas circulates and a hot gas passage 30a in which a hot gas circulates and which supplies the hot gas or a mixed gas formed by mixing the hot gas with the cold gas to the crushing machine 60 as a carrier gas for carrying the crushed solid fuel; and a first seal gas supply part 80 which supplies a seal gas to the crushing machine 60. The cold gas passage 30b is provided with a cold gas damper 30d which adjusts an opening to adjust a flow rate of the cold gas circulating therein. The first seal gas supply part 80 has a first seal gas pipeline 81, which is connected to the downstream side of the cold gas damper 30d in the cold gas passage 30b at its upstream end and, supplies the cold gas circulating in the cold gas passage 30b through the first seal gas pipeline 81 to the crushing machine 60 as the seal gas.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a solid fuel pulverizer and a power generation plant, as well as a method of operating a solid fuel pulverizer. [Background technology]

[0002] Conventionally, solid fuels (carbon-containing solid fuels) such as coal and biomass fuels are pulverized into fine powder within a predetermined particle size range by a pulverizer (mill) and then supplied to a combustion device. In the mill, solid fuels such as coal and biomass fuels fed to a pulverizing table are pinched between the pulverizing table and a pulverizing roller to pulverize them, and fine fuels within a predetermined particle size range are selected by a classifier from the pulverized solid fuels that have been pulverized by a conveying gas (primary air) supplied from the outer periphery of the pulverizing table, and then transported to a boiler and combusted in a combustion device. In a thermal power plant, steam is generated by heat exchange with the combustion gas generated by burning the pulverized fuel in the boiler, and the steam is used to rotate and drive a steam turbine, which then rotates and drives a generator connected to the steam turbine to generate electricity.

[0003] In recent years, pressurized mills have become mainstream. In pressurized mills, pressurized high-temperature primary air is blown into the mill to dry the pulverized solid fuel while transporting it to the furnace. The primary air is supplied to the mill after mixing cold gas supplied directly from a primary gas fan with hot gas passed through an air heater. The temperature of the primary air supplied to the mill is adjusted by the mixture ratio of cold gas and hot gas. The mixture ratio is adjusted by controlling the opening of a cold gas damper provided in a cold gas flow path through which the cold gas flows and a hot gas damper provided in a hot gas flow path through which the hot gas flows. For example, the mill described in Patent Document 1 is known as such a mill.

[0004] Patent Document 1 describes a mill in which a primary air supply duct for supplying primary air is connected to the underside of the grinding table, and the primary air supplied from the primary air supply duct is blown into the mill body casing to dry the pulverized coal and transport the pulverized coal. In this mill, a part of the air supplied from the forced draft fan is pressurized by the primary air fan, and a part of the air is guided to the air preheater through the heating side air duct, where it exchanges heat with the exhaust gas to become heated hot air, and is guided to the primary air supply duct through a hot air damper for adjusting the flow rate. Furthermore, the other part of the air from the primary air fan is guided to the primary air supply duct through the cold air damper as cold air by a cold air duct that does not pass through the air preheater, and the temperature at the mill outlet is maintained at, for example, 70°C by adjusting the opening of the air dampers that are operated inversely to each other. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-15427 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, the temperature of primary air required by mills has tended to become higher. This is because, for example, in order to reduce fuel costs, low-quality coal that contains a lot of moisture and requires a large amount of heat for drying is crushed by a mill. As the temperature of primary air required by the mill becomes higher, the opening of the hot gas damper tends to be increased and the opening of the cold gas damper tends to be decreased, and the opening of the cold gas damper may be close to fully closed. Due to the nature of the damper, the relationship between the opening and the flow rate is close to linear near the intermediate opening, and controllability is good, but the flow rate characteristic relative to the opening decreases near the fully closed or fully open position. This has led to a problem of reduced controllability of the primary air temperature and flow rate.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to provide a solid fuel pulverization device and power generation plant, as well as an operating method for a solid fuel pulverization device, which can suppress a decrease in controllability of the conveying gas and suitably adjust the temperature and flow rate of the conveying gas. [Means for solving the problem]

[0008] In order to solve the above problems, the solid fuel pulverizing apparatus, the power generation plant, and the method of operating the solid fuel pulverizing apparatus of the present disclosure employ the following measures. A solid fuel pulverization apparatus according to one embodiment of the present disclosure has a pulverizer for pulverizing solid fuel, a cold gas flow path through which cold gas flows, and a hot gas flow path through which hot gas, which is a gas with a higher temperature than the cold gas, flows. The apparatus is equipped with a conveying gas supply unit that supplies the hot gas or a mixed gas of the hot gas and the cold gas to the pulverizer as a conveying gas for transporting the pulverized solid fuel, and a first sealing gas supply unit that supplies a sealing gas to the pulverizer. The cold gas flow path is provided with a cold gas damper that adjusts the opening degree of the cold gas damper to adjust the flow rate of the cold gas flowing therethrough. The first sealing gas supply unit has a first sealing gas flow path whose upstream end is connected to the cold gas flow path downstream of the cold gas damper, and supplies the cold gas flowing through the cold gas flow path via the first sealing gas flow path as a sealing gas to the pulverizer.

[0009] A method for operating a solid fuel pulverization apparatus according to one embodiment of the present disclosure includes a pulverizer for pulverizing solid fuel, a cold gas flow path through which a cold gas flows, and a hot gas flow path through which a hot gas, which is a gas with a higher temperature than the cold gas, flows, and the method includes a conveying gas supply unit for supplying the hot gas or a mixed gas of the hot gas and the cold gas to the pulverizer as a conveying gas for transporting the pulverized solid fuel, and a first sealing gas supply unit for supplying a sealing gas to the pulverizer, and the cold gas flow path is provided with a cold gas damper for adjusting the opening degree of the cold gas damper to adjust the flow rate of the cold gas flowing therethrough, and the method includes a step of supplying the cold gas flowing through the cold gas flow path as a sealing gas to the pulverizer by the first sealing gas supply unit via a first sealing gas flow path whose upstream end is connected to the downstream side of the cold gas damper of the cold gas flow path. Effect of the Invention

[0010] According to the present disclosure, it is possible to suppress a decrease in controllability of the carrier gas and to suitably control the carrier gas. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a configuration diagram showing a solid fuel pulverizer and a boiler according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a configuration diagram showing a main part of a solid fuel pulverizing device and a boiler according to an embodiment of the present disclosure. [Diagram 3] 4 is a graph showing pressures at various points of primary air flowing from a primary air ventilator to a burner in a solid fuel pulverizer and a boiler according to an embodiment of the present disclosure. [Figure 4] FIG. 11 is a configuration diagram showing a main part of a solid fuel pulverizing device and a boiler according to a modified example of an embodiment of the present disclosure. [Diagram 5] FIG. 11 is a configuration diagram showing a main part of a solid fuel pulverizing device and a boiler according to a modified example of an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A pulverizer, a power plant, and a method of operating a pulverizer according to an embodiment of the present disclosure will now be described with reference to the drawings. A power plant 1 according to this embodiment includes a solid fuel pulverizer 100 and a boiler 200. In the following explanation, "upper" refers to the vertically upward direction, and "upper" in terms such as upper part and upper surface refers to the vertically upward part. Similarly, "lower" refers to the vertically downward part, and the vertical direction is not precise and may include errors.

[0013] The solid fuel pulverizer 100 of this embodiment is an apparatus that pulverizes solid fuel (carbon-containing solid fuel) such as coal or biomass fuel, generates pulverized fuel, and supplies it to a burner (combustion device) 220 of a boiler 200. The power plant 1 including the solid fuel pulverizer 100 and the boiler 200 shown in FIG. 1 is equipped with one solid fuel pulverizer 100, but it may also be a system equipped with multiple solid fuel pulverizers 100 corresponding to each of the multiple burners 220 of one boiler 200.

[0014] The solid fuel pulverizer 100 of this embodiment includes a mill (pulverizer) 10, a coal feeder (solid fuel supply device) 20, a blower (carrier gas supply unit) 30, a state detector 40, and a controller (determiner) 50. The mill 10 and the coal feeder 20 constitute a pulverizer 60.

[0015] The mill 10, which pulverizes solid fuel such as coal or biomass fuel to be supplied to the boiler 200 into fine fuel, which is a finely powdered solid fuel, may be of a type that pulverizes only coal, may be of a type that pulverizes only biomass fuel, or may be of a type that pulverizes biomass fuel together with coal. Here, biomass fuels are organic resources derived from renewable living organisms, such as thinned wood, waste wood, driftwood, grass, waste, sludge, tires, and recycled fuels (pellets and chips) made from these materials, but are not limited to the ones presented here.Biomass fuels are carbon neutral, meaning they do not emit carbon dioxide, a greenhouse gas, because they capture carbon dioxide during the biomass growth process, and various uses for them are being considered.

[0016] The mill 10 comprises a housing 11, a grinding table (rotary table) 12, grinding rollers 13, a drive unit 14, a mill motor 15 connected to the drive unit 14 and driving the grinding table 12 to rotate, a rotary classifier 16, a fuel supply unit 17, and a classifier motor 18 that drives the rotary classifier 16 to rotate. The housing 11 is formed in a cylindrical shape extending in the vertical direction, and is a case that accommodates the grinding table 12, the grinding rollers 13, the rotary classifier 16, and the fuel supply unit 17. A fuel supply unit 17 is attached to the center of the ceiling portion 42 of the housing 11. This fuel supply unit 17 supplies solid fuel guided from the bunker 21 into the housing 11, and is disposed in the vertical direction at the center position of the housing 11 with its lower end extending into the interior of the housing 11.

[0017] A drive unit 14 is provided near the bottom surface 41 of the housing 11, and the grinding table 12 is rotatably disposed and rotated by the driving force transmitted from a mill motor 15 connected to the drive unit 14. The grinding table 12 is a circular member in a plan view, and is disposed so that the lower end of the fuel supply unit 17 faces it. The upper surface of the grinding table 12 may have an inclined shape that is low in the center and high toward the outside, and the outer periphery may have a shape 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 grinding table 12 below, and the grinding table 12 grinds the supplied solid fuel between the grinding roller 13.

[0018] When solid fuel is fed from the fuel supply unit 17 toward the approximate center region of the grinding table 12, the centrifugal force generated by the rotation of the grinding table 12 guides the solid fuel to the outer periphery of the grinding table 12, where it is pinched and pulverized between the grinding table 12 and the grinding rollers 13. The pulverized solid fuel is blown upward by the carrier gas (hereinafter referred to as primary air) guided from the carrier gas passage (hereinafter referred to as primary air passage) 100a, and is guided to the rotary classifier 16. The downstream end of the primary air passage 100a is connected to the outer periphery of the housing 11. In addition, an outlet (not shown) is provided on the outer periphery of the grinding table 12, which allows the primary air flowing in from the primary air passage 100a to flow out into the space above the grinding table 12 in the housing 11. A swirling blade (not shown) is provided at the outlet, which imparts a swirling force to the primary air blown out from the outlet. The primary air given a swirling force by the swirling blade becomes an airflow having a swirling velocity component, and conveys the solid fuel pulverized on the grinding table 12 to the rotary classifier 16 located at the upper part of the housing 11. Among the pulverized solid fuel, particles larger than a predetermined particle size are classified by the rotary classifier 16, or fall without reaching the rotary classifier 16, are returned to the grinding table 12, and are pulverized again between the grinding table 12 and the grinding roller 13. The mill 10 according to this embodiment is a so-called pressurized mill in which primary air pressurized by a primary air ventilator 31 is blown into the mill 10 to dry the pulverized solid fuel while transporting it to the furnace 210. Therefore, the pressure inside the housing 11 is higher than the atmospheric pressure.

[0019] The crushing roller 13 is a rotating body that crushes the solid fuel supplied onto the crushing table 12 from the fuel supply unit 17. The crushing roller 13 is pressed against the upper surface of the crushing table 12 and cooperates with the crushing table 12 to crush the solid fuel. 1 shows only one representative crushing roller 13, but multiple crushing rollers 13 are arranged at regular intervals in the circumferential direction so as to press against the upper surface of the crushing table 12. For example, three crushing rollers 13 are arranged at equal intervals in the circumferential direction on the outer periphery at angular intervals of 120°. In this case, the portions where the three crushing rollers 13 come into contact with the upper surface of the crushing table 12 (pressing portions) are equidistant from the rotation center axis of the crushing table 12.

[0020] The crushing roller 13 can swing up and down by the journal head 45, and is supported so as to be able to move toward and away from the upper surface of the crushing table 12. When the crushing table 12 rotates with the outer circumferential surface of the crushing roller 13 in contact with the solid fuel on the upper surface of the crushing table 12, the crushing roller 13 receives a rotational force from the crushing table 12 and rotates with the crushing table 12. When solid fuel is supplied from the fuel supply unit 17, the solid fuel is pressed between the crushing roller 13 and the crushing table 12 and crushed.

[0021] A support arm 47 of the journal head 45 is supported on the side of the housing 11 by a support shaft 48 whose middle portion is aligned horizontally so that the crushing roller 13 can swing up and down about the support shaft 48. A pressing device 49 is provided on the upper end portion on the vertically upper side of the support arm 47. The pressing device 49 is fixed to the housing 11 and applies a load to the crushing roller 13 via the support arm 47 etc. so as to press the crushing roller 13 against the crushing table 12.

[0022] The drive unit 14 is a device that transmits a driving force to the grinding table 12 and rotates the grinding table 12 about its central axis. The drive unit 14 is connected to a mill motor 15 and transmits the driving force of the mill motor 15 to the grinding table 12.

[0023] The rotary classifier 16 is provided at the top of the housing 11 and has a hollow, generally inverted cone-shaped exterior. The rotary classifier 16 is provided with a plurality of blades 16a extending in the vertical direction at its outer periphery. The blades 16a are provided at predetermined intervals (equally spaced) around the central axis of the rotary classifier 16. The rotary classifier 16 is a device that classifies the solid fuel (hereinafter, the pulverized solid fuel is referred to as "pulverized fuel") pulverized by the pulverizing table 12 and the pulverizing rollers 13 into fuel having a particle size larger than a predetermined particle size (for example, 70 to 100 μm for coal) (hereinafter, the pulverized fuel having a particle size larger than the predetermined particle size is referred to as "coarse pulverized fuel") and fuel having a particle size smaller than the predetermined particle size (hereinafter, the pulverized fuel having a particle size smaller than the predetermined particle size is referred to as "fine pulverized fuel"). The rotary classifier 16 that classifies by rotation is also called a rotary separator, and is given a rotational driving force by a classifier motor 18 controlled by the control unit 50, and rotates around the fuel supply unit 17 centering on a cylindrical axis (not shown) extending in the vertical direction of the housing 11. The classifier may be a fixed classifier having a fixed hollow inverted cone-shaped casing and a plurality of fixed swirling vanes on the outer periphery of the casing instead of the blades 16a.

[0024] When the pulverized 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 of the primary air flow, large diameter coarse pulverized fuel particles are knocked down by the blades 16a and returned to the pulverizing table 12 to be pulverized again, and the fine pulverized fuel is guided to the outlet port 19 in the ceiling 42 of the housing 11. The fine pulverized fuel classified by the rotary classifier 16 is discharged from the outlet port 19 to the pulverized fuel supply passage 100b together with the primary air, and is supplied to the burner 220 of the boiler 200. When the solid fuel is coal, the pulverized fuel supply passage 100b is also called a pulverized coal pipe.

[0025] The fuel supply unit 17 is attached so that its lower end portion extends vertically into the interior of the housing 11 so as to penetrate the ceiling portion 42 of the housing 11, and supplies solid fuel input from the upper portion of the fuel supply unit 17 to the approximately central region of the grinding table 12. The fuel supply unit 17 is supplied with solid fuel from the coal feeder 20.

[0026] The coal feeder 20 includes a conveying unit 22 and a coal feeder motor 23. The conveying unit 22 is, for example, a belt conveyor, and conveys the solid fuel discharged from the lower end of the downspout 24 located directly below the bunker 21 to the top of the fuel supply unit 17 of the mill 10 by the driving force provided by the coal feeder motor 23, and inputs the solid fuel into the fuel supply unit 17. Normally, primary air is supplied to the inside of the mill 10 to transport pulverized fuel to the burner 220, and the pressure therein is higher than that of the coal feeder 20 and the bunker 21. The downspout 24, which is a pipe extending in the vertical direction directly below the bunker 21, holds fuel in a layered state inside, and the solid fuel layers layered inside the downspout 24 ensure a seal that prevents the primary air and pulverized fuel on the mill 10 side from flowing back to the bunker 21 side. The amount of solid fuel supplied to the mill 10 is adjusted by, for example, the moving speed of the belt conveyor of the transport unit 22.

[0027] The blower 30 is a device that blows primary air into the housing 11 to dry the pulverized fuel and to transport it to the rotary classifier 16 . In order to appropriately adjust the flow rate and temperature of the primary air blown into the housing 11, in this embodiment, the blower section 30 is equipped with a primary air fan (PAF) 31, a hot gas flow path 30a, a cold gas flow path 30b, a hot gas damper 30c, and a cold gas damper 30d.

[0028] In this embodiment, the hot gas flow path 30a supplies a part of the air (outside air) sent out from the primary air fan 31 as hot gas heated by passing through a heat exchanger 34 such as an air preheater. A hot gas damper 30c is provided downstream of the hot gas flow path 30a. The opening degree of the hot gas damper 30c is controlled by the control unit 50. The flow rate of the hot gas supplied from the hot gas flow path 30a is determined by the opening degree of the hot gas damper 30c.

[0029] The cold gas flow path 30b supplies a portion of the air sent out from the primary air ventilator 31 as cold gas at room temperature. A cold gas damper 30d is provided downstream of the cold gas flow path 30b. The opening degree of the cold gas damper 30d is controlled by the control unit 50. The flow rate of the cold gas supplied from the cold gas flow path 30b is determined by the opening degree of the cold gas damper 30d.

[0030] In this embodiment, the flow rate of the primary air is the sum of the flow rate of the hot gas supplied from the hot gas flow path 30a and the flow rate of the cold gas supplied from the cold gas flow path 30b, and the temperature of the primary air is determined by the mixing ratio of the hot gas supplied from the hot gas flow path 30a and the cold gas supplied from the cold gas flow path 30b, and is controlled by the control unit 50. In this embodiment, a flow path downstream of a joining point M of the hot gas flow path 30a and the cold gas flow path 30b will be described as a primary air flow path 100a. In addition, the oxygen concentration of the primary air blown from the primary air passage 100a to the inside of the housing 11 may be adjusted by introducing a portion of the combustion gas discharged from the boiler 200 via a gas recirculation fan (not shown) into the hot gas supplied from the hot gas passage 30a and mixing it.

[0031] In this embodiment, the state detection unit 40 of the mill 10 transmits measured or detected data to the control unit 50. The state detection unit 40 of this embodiment is, for example, a differential pressure measurement means, and measures the differential pressure of the mill 10 as the pressure difference between the pressure at the portion where the primary air flows into the inside of the housing 11 from the primary air flow passage 100a and the pressure at the outlet port 19 where the primary air and the pulverized fuel are discharged from the inside of the housing 11 to the pulverized fuel supply flow passage 100b. An increase or decrease in this differential pressure of the mill 10 corresponds to an increase or decrease in the amount of pulverized fuel circulating between the vicinity of the rotary classifier 16 inside the housing 11 and the vicinity of the grinding table 12 due to the classification effect of the rotary classifier 16. In other words, by adjusting the rotation speed of the rotary classifier 16 in accordance with the pressure difference at the mill 10, the amount of pulverized fuel discharged from the outlet port 19 can be adjusted in relation to the amount of solid fuel supplied to the mill 10.Therefore, within the range in which the particle size of the pulverized fuel does not affect the combustibility of the burner 220, an amount of pulverized fuel corresponding to the amount of solid fuel supplied to the mill 10 can be stably supplied to the burner 220 provided in the boiler 200. The state detection unit 40 in this embodiment is, for example, a temperature measuring means, which detects the temperature of the primary air supplied to the inside of the housing 11 (the primary air temperature at the mill inlet) and the temperature of the primary air from the space above the grinding table 12 inside the housing 11 to the outlet port 19, and controls the blower unit 30 so that the upper limit temperature is not exceeded. The upper limit temperature is determined taking into consideration the possibility of ignition of the solid fuel, etc. The primary air is cooled inside the housing 11 by transporting the pulverized fuel while drying it, and the temperature of the primary air at the outlet port 19 is, for example, about 60 to 90 degrees.

[0032] The control unit 50 is a device that controls each part of the solid fuel pulverization apparatus 100 . The control unit 50 may, for example, transmit a drive command to the mill motor 15 to control the rotation speed of the grinding table 12. The control unit 50, for example, transmits a drive command to the classifier motor 18 to control the rotational speed of the rotary classifier 16 to adjust the classification performance, and optimizes the differential pressure of the mill 10, i.e., the amount of pulverized fuel circulating inside the mill 10, within a predetermined range, thereby enabling a stable supply of pulverized fuel to the burner 220. In addition, the control unit 50 can adjust the amount of solid fuel supplied (amount of coal supplied) that the conveying unit 22 conveys and supplies to the fuel supply unit 17 by, for example, transmitting a drive instruction to the coal supply motor 23 of the coal supply unit 20. Furthermore, the control unit 50 can adjust the flow rate and temperature of the primary air by controlling the opening of the hot gas damper 30c and the cold gas damper 30d by transmitting an opening instruction to the blower unit 30. Specifically, the control unit 50 controls the opening of the hot gas damper 30c and the cold gas damper 30d so that the flow rate of the primary air supplied to the inside of the housing 11 and the temperature of the primary air at the outlet port 19 become predetermined values ​​set in accordance with the amount of coal feed for each type of solid fuel.

[0033] The control unit 50 is composed of, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and a computer-readable storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, and the CPU reads the program into the RAM or the like and executes information processing and arithmetic processing to realize various functions. The program may be installed in a ROM or other storage medium in advance, may be provided in a state stored in a computer-readable storage medium, or may be distributed via a wired or wireless communication means. The computer-readable storage medium may be a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. The HDD may be replaced with a solid state disk (SSD) or the like.

[0034] Next, a description will be given of the boiler 200 which generates steam by performing combustion using the pulverized fuel supplied from the solid fuel pulverizer 100. The boiler 200 includes a furnace 210 and a burner 220.

[0035] The burner 220 is a device that burns pulverized fuel to form a flame using primary air containing pulverized fuel supplied from the pulverized fuel supply passage 100b and secondary air supplied by heating air (outside air) sent out from a forced draft fan (FDF: Forced Draft Fan) 32 by a heat exchanger 34. The pulverized fuel is burned in the furnace 210, and the high-temperature combustion gas is discharged to the outside of the boiler 200 after passing through heat exchangers (not shown) such as an evaporator, a superheater, and a coal economizer.

[0036] An additional air injection port (not shown) for branching off a portion of the secondary air and injecting it into the boiler 200 may be provided above the burner 220. This forms a reduction region between the burner 220 and the additional air injection port in the boiler 200, thereby reducing NOx generated near the burner 220, thereby making it possible to reduce the NOx concentration in the combustion gas discharged from the boiler 200.

[0037] The combustion gas discharged from the boiler 200 flows through the flue 36. The combustion gas flowing through the flue 36 is subjected to a predetermined treatment in an environmental device (such as a denitration device 35, an electric dust collector not shown, and a desulfurization device). The denitration device 35 supplies a reducing agent having an effect of reducing nitrogen oxides, such as ammonia and urea water, into a flow path through which the combustion gas flows, and promotes a reaction between the nitrogen oxides in the combustion gas to which the reducing agent has been supplied and the reducing agent by the catalytic action of a denitration catalyst installed in the denitration device 35, thereby removing and reducing the nitrogen oxides in the combustion gas. The combustion gas that has been subjected to the predetermined treatment is subjected to heat exchange between air sent out from a primary air fan 31 and air sent out from a forced draft fan 32 in a heat exchanger 34 such as an air preheater, and is led to a chimney (not shown) via an induced draft fan (IDF) 33 and released into the outside air. The air discharged from the primary air fan 31 and heated by the combustion gas in the heat exchanger 34 is supplied to the above-mentioned hot gas flow path 30a. The water supplied to each heat exchanger of boiler 200 is heated in a coal economizer (not shown), and then further heated by an evaporator (not shown) and a superheater (not shown) to generate high-temperature, high-pressure steam. This is then sent to the power generation section, a steam turbine (not shown), to rotate the steam turbine, which in turn rotates a generator (not shown) connected to the steam turbine to generate electricity, thereby constituting power generation plant 1.

[0038] The flow rate of air supplied to the boiler 200 is the sum of the primary air supplied from the PAF 31 and the secondary air supplied from the seal gas and FDF 32, and the flow rate is controlled to match the oxygen concentration in the boiler exhaust gas set according to the load of the boiler 200. In other words, when the load of the boiler 200 is the same, if the flow rate of the seal gas increases, the combined flow rate of the primary air and secondary air decreases.

[0039] Next, the second sealing gas supply unit 70 and the first sealing gas supply unit 80 according to this embodiment will be described in detail with reference to FIGS.

[0040] The mill 10 includes a moving part that rotates and moves linearly, and a fixed stationary part. A gap is formed between the moving part and the stationary part to allow the moving part to move. The mill 10 is provided with seal parts at multiple locations to seal the gaps so that the gas and pulverized fuel in the housing 11 do not leak from the gaps. A seal gas is supplied to the seal parts from a second seal gas supply part 70. Examples of the seal parts include a seal part that seals the gap between the housing 11 (stationary part) and the grinding table 12 (moving part), and a seal part that seals the gap between the grinding roller 13 (moving part) and a journal shaft part (stationary part) that rotatably supports the grinding roller 13.

[0041] As described above, the seal portion is supplied with a seal gas by the second seal gas supply unit 70. As shown in Figs. 1 and 2, the second seal gas supply unit 70 has a second seal gas pipe (second seal gas flow path) 71 branched off from the cold gas flow path 30b, and a seal gas fan 72 provided in the second seal gas pipe 71. The second seal gas supply unit 70 prevents leakage of pulverized fuel from the inside to the outside of the mill 10 by supplying high-pressure seal gas (higher than the pressure inside the housing 11 of the mill 10) pressurized by the seal gas fan 72 to the seal portion. Note that, when a pressure higher than the internal pressure of the housing 11 can be obtained at the downstream end of the second seal gas pipe 71, the seal gas fan 72 does not need to be provided.

[0042] The upstream end of the second seal gas pipe 71 is connected to the cold gas passage 30b upstream of the cold gas damper 30d. The downstream end of the second seal gas pipe 71 is connected to the mill 10. More specifically, the downstream end of the second seal gas pipe 71 is connected to a seal portion provided in the mill 10. In addition, in FIG. 1 and FIG. 4, the downstream end of the second seal gas pipe 71 is illustrated as being connected to the bottom surface portion 41 of the housing 11 of the mill 10, but this shows that the downstream end of the second seal gas pipe 71 is connected to a seal portion provided in the mill 10, and does not specifically show the connection portion of the second seal gas pipe 71. The downstream end of the second seal gas pipe 71 is connected to all or some of the seal portions provided in the mill 10.

[0043] In addition, the coal feeder 20, which supplies solid fuel to the mill 10, is connected to the mill 10 via a fuel supply unit 17. Since many driving units such as a conveying unit 22 are provided inside the coal feeder 20, a seal gas is introduced into the coal feeder 20 by a first seal gas supply unit 80, and an air flow is created toward the pressurized mill 10 as shown by arrow A in Fig. 2, thereby preventing the backflow of pulverized solid fuel from the mill 10. In other words, the seal gas supplied to the coal feeder 20 flows toward the mill 10.

[0044] As shown in FIGS. 1 and 2, the first sealing gas supply unit 80 has a first sealing gas pipe (first sealing gas flow path) 81 branching off from the cold gas flow path 30b. An upstream end of the first sealing gas piping 81 is connected to the cold gas passage 30b downstream of the cold gas damper 30d. A downstream end of the first sealing gas piping 81 is connected to the coal feeder 20. In detail, the downstream end of the first sealing gas piping 81 is connected to the coal feeder housing 25 that forms the outer shell of the coal feeder 20.

[0045] 2, the primary air flow passage 100a is provided with a primary air flow meter (carrier gas flow detection unit) 101 that measures the flow rate of the primary air flowing therethrough. The primary air flow meter 101 detects the flow rate of the primary air supplied to the mill 10.

[0046] Further, a seal gas flow meter (seal gas flow rate detection unit) 82 that measures the flow rate of the seal gas flowing inside is provided in the first seal gas piping 81. The seal gas flow meter 82 detects the flow rate of the seal gas supplied to the coal feeder 20.

[0047] As described above, the seal gas supplied to the coal feeder 20 flows into the mill 10. Therefore, the seal gas supplied to the coal feeder 20 is mixed with the primary air in the mill 10 and is led to the furnace 210 through the pulverized fuel supply passage 100b. Therefore, the seal gas supplied to the coal feeder 20 can also be considered as part of the flow rate of the primary air led to the furnace 210. Therefore, the control unit 50 derives the flow rate of the primary air led to the furnace 210 based on the flow rate of the primary air measured by the primary air flow meter 101 and the flow rate of the seal gas measured by the seal gas flow meter 82. At this time, the control unit 50 may correct the flow rates measured by each measuring instrument based on the temperature and / or pressure of the measured gas, and derive the flow rate of the primary air led to the furnace 210 using the corrected value.

[0048] The means for detecting the flow rate of the primary air led to the mill 10 is not limited to the above means. For example, instead of the primary air flow meter 101, as shown by the dashed line in FIG. 2, a hot gas flow meter 30e for measuring the flow rate of the hot gas flowing in the hot gas flow passage 30a and a cold gas flow meter 30f for measuring the flow rate of the cold gas flowing in the cold gas flow passage 30b may be provided, and the flow rate of the primary air supplied to the mill 10 may be detected based on the values ​​measured by the hot gas flow meter 30e and the cold gas flow meter 30f. In this case, the hot gas flow meter 30e is provided upstream of the joining point M of the hot gas flow passage 30a and the cold gas flow passage 30b. The cold gas flow meter 30f is provided upstream of the branching position of the first seal gas pipe 81. The control unit 50 may also correct the flow rates measured by each measuring device based on the temperature and / or pressure of the gas measured, and derive the flow rate of the primary air led to the mill 10 using the corrected value. Furthermore, the cold gas flow meter 30f may be provided downstream of the branching position of the first seal gas pipe 81. In this case, the control unit 50 may derive the flow rate of the primary air led to the mill 10 using the value measured by the seal gas flow meter 82 in addition to the values ​​measured by the hot gas flow meter 30e and the cold gas flow meter 30f. The control unit 50 may also correct the flow rates measured by each measuring instrument based on the temperature and / or pressure of the gas measured, and use the corrected value to derive the flow rate of the primary air led to the mill 10.

[0049] The flows of the primary air and the seal gas in this embodiment will be described. As shown in FIG. 1, the outside air taken into the system by the primary air ventilator 31 branches into the hot gas passage 30a and the cold gas passage 30b. The outside air that flows into the hot gas passage 30a is heated by the heat exchanger 34 to become hot gas. The hot gas flowing through the hot gas passage 30a has its flow rate adjusted by the hot gas damper 30c and flows into the primary air passage 100a from the junction M. On the other hand, the outside air that flows into the cold gas passage 30b flows through the cold gas passage 30b as cold gas. A part of the cold gas flowing through the cold gas passage 30b flows into the second seal gas pipe 71. The cold gas that flows into the second seal gas pipe 71 is guided to the seal part of the mill 10 by the seal gas fan 72. The cold gas that does not flow into the second seal gas pipe 71 flows through the cold gas passage 30b and its flow rate is adjusted by the cold gas damper 30d. A portion of the cold gas whose flow rate has been adjusted flows into the first sealed gas pipe 81. The cold gas that flows into the first sealed gas pipe 81 is led to the coal feeder 20. The cold gas that does not flow into the first sealed gas pipe 81 flows into the primary air passage 100a from the junction M. The cold gas and hot gas that flow into the primary air passage 100a are mixed in the primary air passage 100a, and led to the mill 10 as primary air.

[0050] According to this embodiment, the following advantageous effects are obtained. In this embodiment, the first seal gas pipe 81 branches off from the cold gas flow passage 30b downstream of the cold gas damper 30d. As a result, the amount of gas passing through the cold gas damper 30d is the total amount of the cold gas used for the primary air supplied to the mill 10 and the seal gas supplied to the coal feeder 20. That is, the amount of gas passing through the cold gas damper 30d is greater than the case where only the cold gas used for the primary air supplied to the mill 10 passes through the cold gas damper 30d. Due to the nature of the damper, the flow rate characteristic with respect to the opening degree decreases near the fully closed position. In this embodiment, however, since the amount of gas passing through the cold gas damper 30d increases, the opening degree of the cold gas damper 30d is increased, and the cold gas damper 30d can be operated in a high (good) opening degree range. From the above, it is possible to suppress the decrease in the controllability of the cold gas damper 30d and suitably adjust the temperature and flow rate of the primary air supplied to the mill 10. In particular, in a small mill with a small absolute value of the flow rate of primary air (for example, a mill with a grinding amount of 20 tons or less per hour), the opening degree of the cold gas damper 30d becomes small, and the controllability of the damper is likely to decrease. For this reason, the configuration of this embodiment is particularly effective in a small mill. In addition, in the low load zone of the power plant 1, the absolute value of the flow rate of the primary air is small, and the temperature of the hot gas is also reduced. Therefore, the opening degree of the cold gas damper 30d is reduced, and the controllability of the damper is likely to decrease. Therefore, the configuration of this embodiment is also effective in the operation of the power plant 1 in the low load zone.

[0051] In this embodiment, the first seal gas pipe 81 branches off from the cold gas flow passage 30b downstream of the cold gas damper 30d. That is, the cold gas whose flow rate has been adjusted by the cold gas damper 30d is used as a seal gas for the coal feeder 20. Therefore, the total amount of the seal gas supplied to the coal feeder 20 and the primary air supplied to the mill 10 is the amount adjusted by the hot gas damper 30c and the cold gas damper 30d. On the other hand, for example, when the first seal gas pipe 81 branches off from the cold gas flow passage 30b upstream of the cold gas damper 30d, the amount of primary air supplied to the mill 10 is the amount adjusted by the hot gas damper 30c and the cold gas damper 30d. Therefore, the total amount of the seal gas supplied to the coal feeder 20 and the primary air supplied to the mill 10 is the amount of the primary air adjusted by the hot gas damper 30c and the cold gas damper 30d plus the seal gas led to the seal gas supplied to the coal feeder 20. From the above, in this embodiment, the total amount of the seal gas supplied to the coal feeder 20 and the primary air supplied to the mill 10 can be reduced. In particular, since cold gas after flow rate adjustment is extracted as the seal gas, the flow rate of the cold gas supplied to the mill 10 can be reduced. As described above, the seal gas supplied to the coal feeder 20 and the primary air supplied to the mill 10 are mixed in the mill 10 and directed to the furnace 210. Therefore, in this embodiment, which can reduce the total amount of the seal gas supplied to the coal feeder 20 and the primary air supplied to the mill 10, the flow rate of the primary air directed from the mill 10 to the furnace 210 can be reduced.

[0052] In this manner, in this embodiment, the flow rate of the primary air flowing from the mill 10 to the furnace 210 can be reduced. That is, the increase in the flow rate of the mixed fluid of the primary air and the seal gas flowing through the pulverized fuel supply passage 100b can be suppressed. Since the cross-sectional area of ​​the pulverized fuel supply passage 100b is constant, the flow rate increases when the flow rate of the mixed fluid flowing through the passage increases. However, in this embodiment, the increase in the flow rate of the mixed fluid can be suppressed, so the increase in the flow rate can be suppressed. Therefore, the wear of the inner surface of the pulverized fuel supply passage 100b caused by the pulverized fuel carried by the mixed fluid can be suppressed. Therefore, the damage to the pulverized fuel supply passage 100b can be suppressed, so that the life of the pulverized fuel supply passage 100b can be extended.

[0053] In addition, when the flow rate of the mixed fluid flowing through the pulverized fuel supply passage 100b increases, the flow rate ratio of the secondary air supplied to the burner 220 and the additional air supplied to the upper part of the burner 220 decreases accordingly. In this case, the supply balance of air required for suitable combustion in the burner 220 (flow rate ratio of primary air, secondary air, and additional air) is lost, and there is a possibility that the NOx concentration in the combustion gas and the unburned carbon content in the combustion ash increase. For example, when NOx increases, the consumption of ammonia for reducing NOx in the combustion gas increases in the denitrification device 35 arranged downstream of the boiler 200. In addition, when the unburned carbon content in the ash increases, the heat loss (unburned carbon loss) discharged to the outside of the system as ash increases, and the fuel consumption increases. For this reason, there is a possibility that the operating cost of the power plant 1 increases. On the other hand, in this embodiment, the increase in the flow rate of the mixed fluid flowing through the pulverized fuel supply passage 100b can be suppressed. This ensures a supply balance of air necessary for suitable combustion in the burner 220, and can suppress an increase in the NOx concentration in the combustion gas and an increase in the amount of unburned carbon in the combustion ash. Therefore, in the denitrification device 35, an increase in the consumption of a reducing agent (e.g., ammonia, etc.) for reducing NOx in the combustion gas and an increase in the amount of fuel consumed can be suppressed, and an increase in the operating cost of the power plant 1 can be suppressed.

[0054] In addition, in this embodiment, the flow rate of the cold gas supplied to the mill 10 can be reduced while keeping the opening degree of the cold gas damper 30d within a range with good controllability, so that the temperature of the primary air flowing through the housing 11 of the mill 10 can be increased. Therefore, the drying efficiency of the solid fuel can be improved.

[0055] A structure that throttles the seal gas flow rate cannot be installed in the fuel supply section 17 between the coal feeder 20 and the mill 10. For this reason, a large amount of seal gas is consumed in the first seal gas supply section 80 that supplies seal gas to the coal feeder 20. Therefore, for example, if the first seal gas piping 81 that supplies seal gas to the coal feeder 20 branches off from the second seal gas piping 71 that supplies seal gas to the mill 10, this causes the seal gas fan 72 to become larger and the power consumption of the seal gas fan 72 to increase. On the other hand, in this embodiment, the first seal gas pipe 81 that supplies the seal gas to the coal feeder 20 and the second seal gas pipe 71 that supplies the seal gas to the mill 10 are separate flow paths. That is, the system that supplies the seal gas to the coal feeder 20 and the system that supplies the seal gas to the mill 10 are separate systems. This allows the gas blown by the seal gas fan 72 to be limited to the seal gas supplied to the mill 10, so the amount of gas blown by the seal gas fan 72 can be reduced. Therefore, the seal gas fan 72 can be made smaller. In addition, the energy consumption of the seal gas fan 72 can be reduced.

[0056] The pressure of the seal gas required by the coal feeder 20 is lower than the seal gas pressure required by the seal portion of the mill 10. For this reason, for example, when the first seal gas pipe 81 that supplies seal gas to the coal feeder 20 branches off from the second seal gas pipe 71 that supplies seal gas to the mill 10, the high-pressure seal gas generated by the seal gas fan 72 is reduced in pressure by a throttle valve or the like before being supplied to the coal feeder 20, and energy for changing the pressure of the seal gas is wasted. On the other hand, in this embodiment, the first seal gas pipe 81 that supplies the seal gas to the coal feeder 20 and the second seal gas pipe 71 that supplies the seal gas to the mill 10 are separate flow paths. In addition, the first seal gas pipe 81 is not provided with a device (such as a fan) that increases the pressure of the seal gas. Therefore, there is no need to change the pressure of the seal gas, and energy efficiency can be improved.

[0057] The effect of improving energy efficiency will be described in detail with reference to Fig. 3. Fig. 3 is a graph showing the pressure at each point of the primary air flowing from the primary air fan 31 to the burner 220 of the furnace 210 in this embodiment. The vertical axis of Fig. 3 shows the pressure of the primary air, and the horizontal axis of Fig. 3 shows each point.

[0058] In Fig. 3, P7 indicates the location of the primary air fan 31, P6 indicates the branching point (see Fig. 1) between the hot gas flow path 30a and the cold gas flow path 30b, P5 indicates the location of the heat exchanger 34 (after the hot gas H has been heat exchanged) in the hot gas flow path 30a, P4 indicates the location where the hot gas damper 30c or the cold gas damper 30d is provided, and P3 indicates the joining point (P in Fig. 1) between the hot gas flow path 30a and the cold gas flow path 30b. P2 indicates the inlet of the mill 10, and P1 indicates the outlet of the mill 10.

[0059] In the section A7 from P7 to P6, the pressure of the primary air (outside air taken in by the primary air ventilator 31) gradually decreases due to pressure loss caused by flowing through the piping. At the branch point P6, the primary air is divided into cold gas C flowing through the cold gas passage 30b and hot gas H flowing through the hot gas passage 30a and being heated in the heat exchanger 34.

[0060] In section A6 between points P6 and P5, the pressure of the hot gas H is significantly reduced by heat exchange in the heat exchanger 34. In section A5 between points P5 and P4 where the hot gas damper 30c is provided, the pressure of the hot gas H is gradually reduced by pressure loss caused by flowing through the hot gas flow path 30a. Next, in section A4 between points P4 and P3 where the hot gas flow path 30a and the cold gas flow path 30b join together, the pressure of the hot gas H is significantly reduced by pressure loss in the hot gas damper 30c.

[0061] On the other hand, the pressure of the cold gas C gradually decreases in section A6 and section A5 between point P6 and point P4 where the cold gas damper 30d is provided, due to pressure loss caused by the cold gas flow path 30b. Next, the pressure of the cold gas C significantly decreases in section A4 between point P4 and point P3 where the hot gas flow path 30a and the cold gas flow path 30b join, due to pressure loss in the cold gas damper 30d. In the middle of sections A6 and A5, a part of the cold gas C flows into the second sealing gas pipe 71 (see FIG. 1) as a sealing gas S2. The sealing gas S2 that flows into the second sealing gas pipe 71 is pressurized by the sealing gas fan 72, so that the pressure of the sealing gas S2 increases rapidly. Next, the pressure of the sealing gas S2 gradually decreases due to pressure loss caused by flowing through the second sealing gas pipe 71. After that, the pressure of the sealing gas S2 suddenly decreases due to pressure loss caused by being supplied to the sealing portion of the mill 10, and the sealing gas S2 mixes with the gas in the mill 10. In the middle of section A4, a part of the cold gas C flows into the first seal gas piping 81 as a seal gas S1. The pressure of the seal gas S1 that flows into the first seal gas piping 81 gradually decreases due to pressure loss caused by flowing through the first seal gas piping 81. After that, the pressure of the seal gas S1 suddenly decreases due to pressure loss caused by being supplied to the coal feeder 20, and the seal gas S1 flows from the coal feeder 20 to the mill 10 and mixes with the gas in the mill 10.

[0062] The cold gas C and hot gas H that join at point P3 flow through the primary air passage 100a as primary air. In section A2 up to point P2, which is the inlet of the mill 10, the pressure of the primary air gradually decreases due to pressure loss caused by flowing through the primary air passage 100a. In section A2 from point P2 to outlet P1 of the mill 10, the pressure of the primary air decreases due to various factors within the mill 10 (for example, pressure loss when blowing up the outer periphery of the grinding table 12, etc.). The primary air discharged from the mill 10 at point P1 flows through the pulverized fuel supply passage 100b. In section A1 up to point P0 where the burner 220 is provided, the pressure of the primary air gradually decreases due to pressure loss caused by flowing through the pulverized fuel supply passage 100b.

[0063] On the other hand, the dashed line S1' in FIG. 3 indicates the pressure of the seal gas when it is supplied to the coal feeder 20 in the case where the first seal gas pipe 81' (see FIG. 1) is branched from the middle position of the second seal gas pipe 71 (hereinafter, this case is referred to as "Comparative Example"). In the Comparative Example, as described above, the high-pressure seal gas generated by the seal gas fan 72 is decompressed by a throttle valve or the like and supplied to the coal feeder 20, so it can be seen that the pressure is reduced more rapidly than S1 (see pressure difference D). In this way, in this embodiment, the pressure indicated by the area B2 can be reduced compared to the Comparative Example, so that the energy efficiency can be improved by this amount. Also, in the Comparative Example, the flow rate of the cold gas flowing through the second seal gas pipe 71 branched from the cold gas flow passage 30b is also higher than in this embodiment. Therefore, the energy required to increase the pressure by the seal gas fan 72 is also increased. Therefore, in this embodiment, in addition to the pressure reduction in the area indicated by B2, the energy consumed by the seal gas fan 72 is reduced by the area indicated by B1 compared to the Comparative Example. Therefore, from this point of view, energy efficiency can be improved.

[0064] In addition, in this embodiment, a primary air flow meter 101 and a seal gas flow meter 82 are provided. As a result, the flow rate of primary air introduced into the furnace 210 can be derived based on the flow rate of primary air measured by the primary air flow meter 101 and the flow rate of seal gas measured by the seal gas flow meter 82.

[0065] [Variation 1] 2, the cold gas flow passage 30b may be provided with a throttling section 90 for causing a pressure loss to the cold gas flowing therethrough. The throttling section (pressure loss increasing section) 90 is provided in the cold gas flow passage 30b downstream of a portion where the upstream end of the first sealing gas pipe 81 is connected. The throttling section 90 may be, for example, a fixed orifice or a variable orifice.

[0066] When distributing cold gas to the coal feeder 20, due to the arrangement, the pressure loss may differ between the primary air path (primary air flow path 100a, etc.) and the path for the seal gas supplied to the coal feeder 20 (first seal gas pipe 81, etc.). In particular, if the pressure loss of the first seal gas pipe 81 is higher than the pressure loss of the primary air flow path 100a, a desired amount of seal gas may not flow to the coal feeder 20. Therefore, in such a case, by providing the above-mentioned throttle section 90, it is possible to facilitate the flow of the seal gas through the first seal gas pipe 81. Therefore, the seal gas can be suitably supplied to the coal feeder 20.

[0067] [Variation 2] 4, a check valve (backflow prevention unit) 91 for preventing backflow of gas may be provided in the cold gas flow passage 30b. The check valve 91 is provided downstream of the connection point of the upstream end of the first seal gas pipe 81 in the cold gas flow passage 30b (on the side of the confluence point M of the hot gas flow passage 30a and the cold gas flow passage 30b).

[0068] When the mill 10 requires more heat than expected, for example, when high-moisture coal is used, the cold gas damper 30d may be throttled too much, causing hot gas to flow back from the hot gas passage 30a to the cold gas passage 30b, and the backflowing hot gas may be guided to the coal feeder 20 via the first seal gas piping 81. If hot gas flows into the coal feeder 20, the solid fuel inside the coal feeder 20 may be overheated. In addition, the high-temperature hot gas may deteriorate rubber parts such as the belt of the conveying section 22 of the coal feeder 20, causing a breakdown. By providing the check valve 91, even if the hot gas flows back from the hot gas passage 30a to the cold gas passage 30b, the check valve 91 prevents the hot gas from flowing. Therefore, in the cold gas passage 30b, high-temperature hot gas does not flow upstream of the check valve 91. This makes it difficult for high-temperature hot gas to flow into the first seal gas piping 81. This makes it possible to prevent the hot gas from flowing into the coal feeder 20.

[0069] The backflow valve may be a damper with an adjustable opening (see FIG. 5). That is, when backflow is to be prevented, the damper is fully closed to prevent backflow. By adjusting the opening of this damper, it may be possible to provide the same function as the throttle unit 90 of the first modification.

[0070] [Variation 3] As shown in FIG. 5, an assist pipe 92 may be provided to join the first seal gas pipe 81 at a midpoint. In some cases, such as when the pressure loss in the first seal gas pipe 81 is large, the seal gas that satisfies the amount of seal gas required by the coal feeder 20 may not be supplied. In this case, the shortage of seal gas (assist gas) may be supplied through the assist pipe 92. The upstream end of the assist pipe 92 may be connected to the outlet of the seal gas fan 72 or the upstream side of the cold gas damper 32d of the cold gas flow passage 32b, which have a higher pressure than the branch point of the first seal gas pipe 81. In addition, the assist pipe 92 may be provided with an assist valve 93 to control the supply of the supplementary assist gas. In addition, a check valve 94 may be provided to prevent the high-pressure assist gas from flowing back to the branch point side (cold gas flow passage 30b side) of the first seal gas pipe 81.

[0071] The present disclosure is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present disclosure. For example, in the above-described embodiment, a mill according to the present disclosure is used, but the solid fuel may be a solid fuel such as biomass fuel or PC (Petroleum Coke) fuel generated during oil refining, or a mixture of these solid fuels may be used.

[0072] The solid fuel pulverizing apparatus, the power plant, and the method of operating the solid fuel pulverizing apparatus described in the above-described embodiments can be understood, for example, as follows. A solid fuel pulverization device (100) according to one embodiment of the present disclosure includes a pulverizer (60) for pulverizing solid fuel, a cold gas flow path (30b) through which a cold gas flows, and a hot gas flow path (30a) through which a hot gas, which is a gas with a higher temperature than the cold gas, flows. The solid fuel pulverization device (100) includes a conveying gas supply unit (30) for supplying the hot gas or a mixed gas of the hot gas and the cold gas to the pulverizer (60) as a conveying gas for conveying the pulverized solid fuel, and a first sealing gas supply unit (30) for supplying a sealing gas to the pulverizer (60). The cold gas flow path (30b) is provided with a cold gas damper (30d) for adjusting the opening degree to adjust the flow rate of the cold gas flowing therethrough, and the first seal gas supply unit (80) has a first seal gas flow path (81) whose upstream end is connected to the cold gas flow path (30b) downstream of the cold gas damper (30d), and supplies the cold gas flowing through the cold gas flow path (30b) to the crusher (60) via the first seal gas flow path (81) as a seal gas.

[0073] In the above configuration, the seal gas flow path branches off from the cold gas flow path downstream of the cold gas damper. As a result, the amount of gas passing through the cold gas damper is the sum of the cold gas used as the carrier gas and the seal gas. In other words, the amount of gas passing through the cold gas damper is greater than when only the cold gas used as the carrier gas passes through the cold gas damper. Due to the nature of the damper, the controllability of the flow rate relative to the opening degree decreases near the fully closed position, but in the above configuration, the amount of gas passing through the cold gas damper increases, so the opening degree of the cold gas damper can be increased. As described above, it is possible to suppress the decrease in controllability of the cold gas damper and to suitably adjust the temperature and flow rate of the carrier gas.

[0074] In addition, in a solid fuel pulverization apparatus according to one embodiment of the present disclosure, the pulverizer (60) has a pulverization section (10) that pulverizes the solid fuel and a solid fuel supplying device (20) that supplies the solid fuel to the pulverization section (10), and the first sealing gas supplying section (80) supplies a sealing gas to the solid fuel supplying device (20), and further includes a second sealing gas supplying section (70) that supplies a sealing gas to the solid fuel supplying device (20), and has a second sealing gas flow path (71) whose upstream end is connected to the upstream side of the cold gas damper (30d) of the cold gas flow path (30b), and a blowing section provided in the second sealing gas flow path (71), and supplies the cold gas flowing through the cold gas flow path (30b) via the second sealing gas flow path (71) as a sealing gas to the pulverization section (10).

[0075] In the above configuration, the first seal gas flow path that supplies the seal gas to the solid fuel supply device and the second seal gas flow path that supplies the seal gas to the pulverization section are separate flow paths. That is, the system that supplies the seal gas to the solid fuel supply device and the system that supplies the seal gas to the pulverization section are separate systems. This allows the gas blown by the blower section to be only the seal gas supplied to the pulverization section, so the amount of gas blown by the blower section can be reduced. Therefore, the blower section can be made smaller. Also, the energy consumption of the blower section can be reduced.

[0076] In addition, in the solid fuel pulverization apparatus according to one embodiment of the present disclosure, the cold gas flow passage (30b) is provided with a pressure loss increasing section (90) downstream of the point where the upstream end of the first sealing gas flow passage (81) is connected, which increases the pressure loss of the cold gas flowing therethrough.

[0077] In the above configuration, a pressure loss increasing section is provided downstream of the connection of the upstream end of the first seal gas flow passage in the cold gas flow passage. This increases the pressure loss downstream of the connection of the upstream end of the first seal gas flow passage in the cold gas flow passage. This makes it easier for the seal gas to flow through the first seal gas flow passage. This allows the seal gas to be suitably supplied to the pulverizer.

[0078] In addition, in the solid fuel pulverization apparatus according to one embodiment of the present disclosure, the cold gas flow path (30b) is provided with a backflow prevention section (91) for preventing backflow of gas downstream of the point where the upstream end of the first sealing gas flow path (81) is connected.

[0079] In the above configuration, a backflow prevention unit is provided in the cold gas flow path downstream of the point where the upstream end of the first seal gas flow path is connected. As a result, for example, when high-temperature gas in the pulverizer flows back through the conveying gas supply unit, the high-temperature gas is blocked by the backflow prevention unit. Therefore, in the cold gas flow path, high-temperature gas does not flow upstream of the backflow prevention unit. This makes it difficult for high-temperature gas to flow into the first seal gas flow path.

[0080] In addition, a solid fuel pulverization apparatus according to one embodiment of the present disclosure includes a carrier gas flow rate detection unit (101) that detects the flow rate of the carrier gas supplied to the pulverizer (60), and a sealing gas flow rate detection unit (82) that detects the flow rate of the sealing gas supplied to the pulverizer (60).

[0081] The above-mentioned configuration includes a conveying gas flow rate detector and a seal gas flow rate detector, which can detect the total amount of gas supplied to the crusher, and therefore the amount of gas discharged from the crusher.

[0082] In addition, a solid fuel pulverization apparatus according to one embodiment of the present disclosure includes an assist pipe (92) that joins the first sealing gas flow path (81) at a midpoint, and the assist pipe (92) supplies a sealing gas having a higher pressure than the branching point of the first sealing gas pipe (81) to the first sealing gas pipe (81).

[0083] In cases such as when the pressure loss in the first seal gas piping is large, it may not be possible to supply the seal gas that satisfies the amount of seal gas required by the supply destination. In the above configuration, an assist pipe is provided for supplying a seal gas having a higher pressure than the branch point of the first seal gas pipe to the first seal gas pipe 81. This allows a high-pressure seal gas to be supplied to the first seal gas pipe, thereby increasing the pressure of the seal gas flowing through the first seal gas pipe. Therefore, even if the pressure loss of the first seal gas pipe is large, the seal gas can be easily sent to the supply destination.

[0084] A power plant of the present disclosure includes any one of the solid fuel pulverizers (100) described above, and a boiler (200) that generates steam by burning the solid fuel pulverized by the solid fuel pulverizer (100).

[0085] A method of operating a solid fuel pulverization apparatus according to one aspect of the present disclosure includes a pulverizer (60) for pulverizing solid fuel, a cold gas flow path (30b) through which a cold gas flows, and a hot gas flow path (30a) through which a hot gas that is a gas with a temperature higher than the cold gas flows, the method including: a conveying gas supply unit (30) for supplying the hot gas or a mixed gas of the hot gas and the cold gas to the pulverizer (60) as a conveying gas for conveying the pulverized solid fuel; and a first sealing gas supply unit (80) for supplying a sealing gas to the pulverizer (60). a cold gas flow passage (30b) provided with a cold gas damper (30d) for adjusting the opening degree to adjust the flow rate of the cold gas flowing therethrough, the method comprising the step of supplying the cold gas flowing through the cold gas flow passage (30b) as a seal gas to the pulverizer (60) by the first seal gas supply unit (80) via a first seal gas flow passage (81) having an upstream end connected to the cold gas flow passage (30b) downstream of the cold gas damper (30d). [Explanation of symbols]

[0086] 1: Power plant 10: Mill (grinding section) 11: Housing 12: Grinding table 13: Crushing roller 14: Drive unit 15: Mill motor 16: Rotary classifier 16a: Blade 17:Fuel supply section 18: Classifier motor 19: Exit port 20: Coal feeder (solid fuel supply device) 21: Banka 22: Transport section 23: Coal feeder motor 24: Downspout 25: Coal feeder housing 30: Blower section 30a: Hot gas flow path 30b: Cold gas passage 30c: Thermal gas damper 30d: Cold gas damper 30e: Hot gas flow meter 30f: Cold gas flow meter 31: Primary air ventilator 32: Forced air ventilator 32b: Cold gas passage 32d: Cold gas damper 34:Heat exchanger 35: Denitration equipment 36: Flue 40: Status detection unit 41: Bottom part 42: Ceiling 45: Journal Head 47: Support arm 48: Support shaft 49: Pressing device 50: Control section 60: Crusher 70: Second seal gas supply section 71: Second seal gas piping 72: Seal gas fan 80: First seal gas supply section 81: First seal gas pipe 81´: First seal gas pipe 82: Seal gas flow meter 90: Squeezing section 91: Check valve 92: Assist piping 93: Assist valve 100: Solid fuel crushing device 100a: Primary air flow passage 100b: Pulverized fuel supply passage 101: Primary air flow meter 200: Boiler 210: Furnace 220: Burner

Claims

1. a pulverizer for pulverizing the solid fuel; a conveying gas supply unit having a cold gas flow path through which a cold gas flows and a hot gas flow path through which a hot gas, which is a gas having a higher temperature than the cold gas, flows, and supplies the hot gas or a mixed gas obtained by mixing the hot gas and the cold gas to the pulverizer as a conveying gas for conveying the pulverized solid fuel; A first seal gas supply unit that supplies a seal gas to the crusher, The cold gas flow passage is provided with a cold gas damper that adjusts the flow rate of the cold gas flowing therethrough by adjusting the opening degree thereof, The first sealing gas supply unit has a first sealing gas flow passage whose upstream end is connected to the cold gas flow passage downstream of the cold gas damper, and supplies the cold gas flowing through the cold gas flow passage via the first sealing gas flow passage to the pulverizer as a sealing gas.

2. The pulverizer includes a pulverizing unit that pulverizes the solid fuel, and a solid fuel supplying device that supplies the solid fuel to the pulverizing unit, the first sealing gas supply unit supplies a sealing gas to the solid fuel supply device, A solid fuel pulverization apparatus as described in claim 1, further comprising a second sealing gas supply unit having a second sealing gas flow passage whose upstream end is connected to the upstream side of the cold gas damper of the cold gas flow passage and a blower unit provided in the second sealing gas flow passage, and supplying the cold gas flowing through the cold gas flow passage via the second sealing gas flow passage to the pulverization unit as a sealing gas.

3. A solid fuel pulverization device as described in claim 1 or claim 2, wherein the cold gas flow passage has a pressure loss increasing section downstream of the point where the upstream end of the first sealing gas flow passage is connected, which increases the pressure loss of the cold gas flowing therethrough.

4. A solid fuel pulverization device as described in any one of claims 1 to 3, wherein the cold gas flow passage is provided with a backflow prevention section for preventing backflow of gas downstream of the point where the upstream end of the first seal gas flow passage is connected.

5. a carrier gas flow rate detection unit that detects a flow rate of the carrier gas supplied to the pulverizer; 5. The solid fuel pulverizer according to claim 1, further comprising a seal gas flow rate detector that detects a flow rate of the seal gas supplied to the pulverizer.

6. an assist pipe that joins the first seal gas flow passage at a midpoint; 6. The solid fuel pulverizer according to claim 1, wherein the assist pipe supplies, to the first seal gas flow passage, a seal gas having a pressure higher than that at a branch point of the first seal gas flow passage.

7. A solid fuel pulverizer according to any one of claims 1 to 6, a boiler for burning the solid fuel pulverized by the solid fuel pulverizer to generate steam; A power plant comprising:

8. a pulverizer for pulverizing the solid fuel; a conveying gas supply unit having a cold gas flow path through which a cold gas flows and a hot gas flow path through which a hot gas, which is a gas having a higher temperature than the cold gas, flows, and supplies the hot gas or a mixed gas obtained by mixing the hot gas and the cold gas to the pulverizer as a conveying gas for conveying the pulverized solid fuel; A first seal gas supply unit that supplies a seal gas to the crusher, A method for operating a solid fuel pulverizer, comprising the steps of: adjusting an opening degree of a cold gas damper in the cold gas flow passage to adjust a flow rate of the cold gas flowing therethrough; A method for operating a solid fuel pulverization apparatus comprising a step of supplying the cold gas flowing through the cold gas flow passage as a seal gas to the pulverizer by the first seal gas supply unit via a first seal gas flow passage whose upstream end is connected to the downstream side of the cold gas damper of the cold gas flow passage.

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