CN111032222A

CN111032222A - Pulverizer and operation method of pulverizer

Info

Publication number: CN111032222A
Application number: CN201880053020.1A
Authority: CN
Inventors: 泽昇吾; 山口启树; 滨屋秀行; 山口聪太朗; 松崎光辉; 近藤祐树
Original assignee: Mitsubishi Hitachi Power Systems Ltd
Current assignee: Mitsubishi Power Ltd
Priority date: 2017-08-25
Filing date: 2018-08-24
Publication date: 2020-04-17
Also published as: WO2019039580A1; JP6918641B2; KR20200035046A; KR102400696B1; JP2019037941A

Abstract

The purpose of the present invention is to suppress rapid combustion by spraying a fire extinguishing agent in at least the case where rapid combustion occurs in a housing in any operating state in which the pressure in the housing is different. A pulverizer (5) for pulverizing a solid fuel into fine powder, comprising: a housing (41) that constitutes a housing of the pulverizer (5); pressure sensors (61A, 61B) that detect the pressure inside the housing (41); a1 st fire extinguishing agent spraying unit (60A) that sprays a fire extinguishing agent when the pressure detected by the pressure sensor (61A) is equal to or greater than a1 st predetermined threshold value in a normal operation state of the pulverizer (5); and a2 nd fire extinguishing agent spraying unit (60B) that sprays the fire extinguishing agent when the pressure detected by the pressure sensor (61B) is equal to or greater than a2 nd threshold value, which is a threshold value different from the 1 st threshold value, in the stopped state of the crusher (5).

Description

Pulverizer and operation method of pulverizer

Technical Field

The present invention relates to a crusher equipped with a fire extinguishing facility and a method for operating the crusher.

Background

Solid fuels such as coal and biomass used in thermal power plants and the like are pulverized into fine powder by a pulverizer and supplied to a combustion device such as a boiler. In the pulverizer, a solid fuel such as coal or biomass fed from a coal supply pipe onto a pulverizing table is pulverized by grinding between the pulverizing table and a pulverizing roller, and the pulverized fuel in a fine powder form is divided into fuel having a small particle size by a classifier and is conveyed to a combustion device by a conveying gas supplied from the outer periphery of the pulverizing table.

Biomass fuel has attracted attention as one of measures for reducing the amount of carbon dioxide discharged from boilers and the like using fossil fuel. Biomass fuel is supplied to a pulverizer in the form of pellets and pulverized, but because it is easily ignited by static electricity, for example, it has a possibility of causing rapid combustion, and there is a possibility of rapid combustion compared to coal (pulverized coal), and therefore, when biomass is used as fuel, it is necessary to enhance safety control.

Patent document 1 discloses the following: when a pressure equal to or higher than the normal pressure is generated in the mill, a plurality of compactors are operated, and the pulverized coal supply mechanism, the pulverization mechanism, and the separation mechanism are stopped.

Patent document 2 discloses the following: when the differential pressure between the pressure in the traveling direction of the shock wave generated by the rapid combustion and the pressure in the direction perpendicular to the traveling direction becomes equal to or higher than a predetermined value or the internal pressure of the micro-pulverizer or the hot air duct becomes equal to or higher than a predetermined value, the micro-pulverizer is stopped.

Prior art documents

Patent document

Patent document 1: japanese examined patent publication No. 58-35239

Patent document 2: japanese patent laid-open publication No. 2002-143714

Disclosure of Invention

Problems to be solved by the invention

Patent documents 1 and 2 describe the interest of stopping the function of the pulverizer when the pressure in the pulverizer becomes equal to or higher than a predetermined pressure, but do not describe the content relating to ignition of the solid fuel inside the pulverizer when the pulverizer is stopped or when the pulverizer is shifted to a stop.

In the pulverizer, the pressure in the pulverizer differs depending on the operating state (for example, a normal operating state, an operation stop state, or the like), and in any operating state, when solid fuel is present inside, there is a possibility that the solid fuel ignites and rapidly burns inside the pulverizer. Therefore, even if ignition of the solid fuel is sensed only for a specific operating state and rapid combustion is suppressed, rapid combustion may not be suppressed in other operating states.

The present invention has been made in view of such circumstances, and an object thereof is to provide a pulverizer and a method of operating the pulverizer, which can suppress rapid combustion by injecting a fire extinguishing agent at least when rapid combustion occurs in a housing in any operating state in which pressures in the pulverizer are different.

Means for solving the problems

In order to solve the above problems, the following aspects are adopted in a crusher and a method of operating a crusher according to the present invention.

A pulverizer according to an aspect of the present invention pulverizes a solid fuel into a fine powder solid fuel, the pulverizer including: a frame constituting a housing of the pulverizer; a pressure sensor that detects a pressure inside the frame; a1 st fire extinguishing agent spraying unit configured to spray a fire extinguishing agent into the housing when the pressure detected by the pressure sensor is equal to or greater than a1 st predetermined threshold value in a1 st operation state of the pulverizer; and a2 nd fire extinguishing agent spraying unit configured to spray a fire extinguishing agent into the housing when the pressure detected by the pressure sensor is equal to or higher than a2 nd threshold value, which is a threshold value different from the 1 st threshold value, in a2 nd operation state, which is an operation state different from the 1 st operation state of the crusher.

Since a large amount of pulverized solid fuel exists in the housing of the pulverizer, there is a possibility that the pulverized fine-powder solid fuel may ignite. When the fine powder solid fuel is ignited, the pressure in the housing rises to a level higher than the pressure before rapid combustion (i.e., the pressure during normal operation). Therefore, the occurrence of rapid combustion can be determined by detecting the pressure in the frame.

In the above configuration, the 1 st threshold is set in the 1 st operation state, and the 2 nd threshold is set in the 2 nd operation state, and different thresholds are set. Therefore, even when the pressures in the normal operation in the 1 st operation state and the 2 nd operation state are different, the occurrence of rapid combustion in the frame in each operation state can be determined. In the 1 st operation state and the 2 nd operation state, different fire extinguishing agent spraying portions are operated. Thus, even in the case where the fire extinguishing agent is injected in one of the operation states and then the other operation state is reached, the fire extinguishing agent can be injected when rapid combustion occurs in the other operation state. Therefore, in any operating state in which the pressure inside the housing is different, at least when rapid combustion occurs inside the housing, the extinguishing agent can be sprayed to suppress the rapid combustion.

In the pulverizer according to one aspect of the present invention, the 1 st operating state is a normal operating state of the pulverizer, the 2 nd operating state is a stop operating state including a time when the pulverizer stops operating and a time when the pulverizer transitions to the stop operating state, the 1 st threshold value may be set based on a maximum pressure in the housing in the normal operating state, and the 2 nd threshold value may be set based on a pressure in the housing in the stop operating state. Also, the 2 nd threshold may be set higher than the 1 st threshold.

In the above configuration, the 1 st threshold is set according to the pressure in the housing in which the crusher is in the normal operation state. Thus, the fire extinguishing agent can be sprayed in response to rapid combustion occurring in the housing in a normal operation state of the pulverizer, and rapid combustion can be suppressed. In addition, since the pressure value in the housing changes depending on each operating state in the stopped operating state, the 2 nd threshold is set according to the highest pressure in the housing in which the crusher is in the stopped operating state. Thus, the fire extinguishing agent can be sprayed in response to rapid combustion occurring in the housing in a state where the pulverizer is stopped, and rapid combustion can be suppressed.

Therefore, for example, in the normal operation state, the rapid combustion occurs in the housing, and the crusher is stopped after the 1 st fire extinguishing agent injection part injects the fire extinguishing agent to suppress the rapid combustion, so even when the rapid combustion occurs again in the housing in the operation in the stopped state, the rapid combustion in the housing can be suppressed by the 2 nd fire extinguishing agent injection part injecting the fire extinguishing agent.

As a method of setting the 1 st threshold value based on the pressure in the frame in the normal operation state, for example, a pressure obtained by adding a predetermined pressure to the pressure in the normal state in the normal operation state may be set as the 1 st threshold value. As a method of setting the 2 nd threshold value based on the pressure in the frame in the stopped state, for example, a pressure obtained by adding a predetermined pressure to the pressure in the normal state in the stopped state may be set as the 2 nd threshold value.

In the pulverizer according to one aspect of the present invention, the 1 st fire extinguishing agent spraying portion and the 2 nd fire extinguishing agent spraying portion may be provided in pair.

In the above structure, the 1 st fire extinguishing agent spraying part and the 2 nd fire extinguishing agent spraying part are provided in pairs. Thus, when the 1 st and 2 nd fire extinguishing agent spraying parts are installed and maintained, the 1 st and 2 nd fire extinguishing agent spraying parts can be simultaneously operated. Therefore, as compared with the case where the 1 st fire extinguishing agent spraying portion and the 2 nd fire extinguishing agent spraying portion are provided independently, the workload at the time of installation and the workload at the time of maintenance can be reduced.

In the pulverizer according to one aspect of the present invention, the fire extinguishing agent may not be injected from the 1 st fire extinguishing agent injection unit and/or the 2 nd fire extinguishing agent injection unit depending on the type of the solid fuel.

In the above configuration, the fire extinguishing agent is not sprayed from the 1 st fire extinguishing agent spraying portion and/or the 2 nd fire extinguishing agent spraying portion according to the type of the solid fuel to be pulverized by the pulverizer. Thus, whether or not the fire extinguishing agent is injected into the housing can be determined according to the type of the solid fuel. Therefore, for example, when the fire extinguishing agent is not ejected from the 1 st fire extinguishing agent ejection part and/or the 2 nd fire extinguishing agent ejection part when the solid fuel having low ignitability is pulverized, it is possible to prevent a malfunction in which the pressure is increased due to a factor other than rapid combustion and the fire extinguishing agent is ejected into the housing in a state where rapid combustion does not occur in the housing.

A pulverizer according to an aspect of the present invention includes a carrier gas supply pipe through which a carrier gas supplied into the housing flows, and a part of the carrier gas supply pipe is openable because an inside of the carrier gas supply pipe is at a predetermined pressure or higher.

In the above configuration, a part of the carrier gas supply pipe is opened when the pressure inside the carrier gas supply pipe is equal to or higher than a predetermined pressure. As a result, when rapid combustion occurs in the housing and a pressure rise in the housing propagates into the carrier gas supply pipe, a part of the carrier gas supply pipe is opened when the pressure in the carrier gas supply pipe becomes equal to or higher than a predetermined pressure. When a part of the carrier gas supply pipe is opened, the pressure is effectively released from the opened part, and therefore, the pressure in the carrier gas supply pipe can be prevented from rising above a predetermined pressure. This makes it possible to keep the pressure in the carrier gas supply pipe at or below a predetermined pressure, and also to suppress a rapid increase in the pressure in the housing of the pulverizer, thereby suppressing an increase in the density of the partially pulverized solid fuel in the housing and further suppressing the progress of rapid combustion. Therefore, the breakage of the carrier gas supply pipe due to the pressure in the carrier gas supply pipe being equal to or higher than the expected pressure can be prevented, and the rapid combustion at the time of spraying the fire extinguishing agent in the housing of the pulverizer can be more effectively suppressed.

Further, since a part of the carrier gas supply pipe is opened, it is not necessary to provide a new space in the carrier gas supply pipe and provide a device such as another rupture plate, and the pressure in the carrier gas supply pipe can be released. Therefore, space saving and cost reduction can be achieved as compared with the case where another device or the like is provided.

A method of operating a pulverizer according to an aspect of the present invention is a method of operating a pulverizer that pulverizes a solid fuel supplied into a frame constituting a casing, the method including: a pressure detection step of detecting a pressure inside the frame; a1 st fire extinguishing agent spraying step of spraying the fire extinguishing agent from a1 st fire extinguishing agent spraying portion into the housing when the pressure detected in the pressure detecting step is equal to or higher than a predetermined 1 st threshold value in a1 st operation state of the pulverizer; and a2 nd fire extinguishing agent spraying step of spraying the fire extinguishing agent from the 2 nd fire extinguishing agent spraying portion into the housing when the pressure detected in the pressure detecting step is not less than a2 nd threshold value which is a threshold value different from the 1 st threshold value in a2 nd operation state which is an operation state different from the 1 st operation state of the crusher.

Effects of the invention

According to the present invention, in any operating state in which the pressure inside the housing is different, at least when rapid combustion occurs inside the housing, the fire extinguishing agent can be sprayed to suppress the rapid combustion.

Drawings

Fig. 1 is a schematic configuration diagram showing a boiler facility including a pulverizer according to embodiment 1 of the present invention.

Fig. 2 is a longitudinal sectional view showing a pulverizer according to embodiment 1 of the present invention.

Detailed Description

Hereinafter, an embodiment of a crusher and an operation method of a crusher according to the present invention will be described with reference to the drawings.

[ 1 st embodiment ]

Hereinafter, embodiment 1 of the present invention will be described with reference to fig. 1 and 2.

Fig. 1 shows a boiler facility 1 including a pulverizer according to the present embodiment. In the present embodiment, the upper side indicates the vertical upper side direction, and the lower side indicates the vertical lower side direction.

In the present embodiment, the boiler facility 1 includes a pulverizer 5, and the pulverizer 5 pulverizes the solid fuel such as the biomass fuel supplied to the boiler main body 3 into fine-powder solid fuel by using, for example, the biomass fuel as the solid fuel. The pulverizer 5 may be a type that pulverizes only the biomass fuel, or may be a type that pulverizes coal and the biomass fuel. The biomass fuel is a renewable organic resource derived from a living organism, and examples thereof include, but are not limited to, metaw wood, waste wood, driftwood, grasses, waste, sludge, tires, and recycled fuels (pellets, chips) using these as a raw material. Regarding biomass fuel, since carbon dioxide is absorbed during the growth of biomass, carbon neutralization, which is regarded as not emitting carbon dioxide that becomes global warming gas, is considered, and thus various studies are made on the use thereof.

The fine powder fuel supply pipe 7 is connected to the pulverizer 5, and the fine powder fuel pulverized by the pulverizer 5 is introduced into the burner 9 through the fine powder fuel supply pipe 7 together with hot air as a carrier gas.

The biomass fuel stored in the biomass silo 11 is introduced into the pulverizer 5 through the hopper 13.

A hot air supply pipe (conveying gas supply pipe) 15 is connected to the pulverizer 5. The hot air supply duct 15 is connected to the 1 st-order ventilation fan 17, and introduces air that is mixed and temperature-conditioned with air preheated by the air preheater 19 and air bypassing the air preheater 19. A part of the exhaust gas passing through the electric dust collector 23 is introduced into the hot air supply pipe 15 through the gas recirculation fan 21. Therefore, the air-fuel mixture whose temperature is adjusted by the air preheater 19 and whose oxygen concentration is adjusted by the exhaust gas is introduced into the pulverizer 5 through the hot air supply pipe 15.

A flame is formed by the burner 9 in the furnace in the boiler main body 3, and steam is generated by a heat exchanger, not shown, in the boiler main body 3. The generated steam is introduced into a steam turbine, not shown, to generate electricity.

The exhaust gas discharged from the boiler main body 3 is denitrated by the denitrator 25, and then the air introduced from the 1 st ventilator 17 is heated by the air preheater 19 and introduced into the electric dust collector 23. The exhaust gas is introduced into the desulfurization device 29 through the induced draft fan 27 after being dedusted by the electrostatic precipitator 23. A part of the exhaust gas may be drawn out on the upstream side of the induction ventilator 27 and introduced into the hot air supply duct 15 via the gas recirculation ventilator 21.

The exhaust gas introduced from the induction fan 27 is desulfurized by the desulfurizer 29, and then introduced into the stack 31 and discharged to the atmosphere.

The details of the shredder 5 shown in figure 1 are shown in figure 2. The pulverizer 5 is a vertical mill, and pulverizes a solid fuel such as a biomass fuel to produce fine powder.

A casing (housing) 41 constituting a housing of the pulverizer 5 has a vertical cylindrical hollow shape, and a fuel supply pipe 43 is attached to a central portion of a ceiling portion 42. The fuel supply pipe 43 supplies the granular biomass fuel introduced from the biomass silo 11 (see fig. 1) into the housing 41, and is disposed at a central position of the housing 41 in the vertical direction (vertical direction), and has a lower end portion extending into the housing 41.

A base 44 is provided on the bottom surface portion 40 of the housing 41, and a pulverization table 45 is rotatably disposed on the base 44. The lower end of the fuel supply pipe 43 is disposed to face the center of the pulverization table 45. As indicated by an arrow a0, the fuel supply pipe 43 supplies the biomass fuel from above toward below.

The grinding table 45 is rotatable about a central axis in the vertical direction (vertical direction), and is driven by a driving device (not shown). The upper surface of the pulverization table 45 may have, for example, an inclined shape in which the center portion is high and becomes lower as it goes outward, and an outer peripheral portion may be curved upward.

A plurality of mill rollers 46 are disposed above the mill table 45 so as to face each other. Each of the mill rollers 46 is disposed above the outer peripheral portion of the mill table 45 at equal intervals in the circumferential direction (in fig. 2, only 1 mill roller 46 and its peripheral devices are shown as a representative example). The mill roller 46 is supported to be freely movable in the vertical direction so as to be close to and apart from the upper surface of the mill table 45. When the mill table 45 is rotated in a state where the outer peripheral surface of the mill roller 46 is in contact with the upper surface of the mill table 45, the mill roller 46 receives a rotational force from the mill table 45 and rotates in conjunction therewith. When the biomass fuel is supplied from the fuel supply pipe 43, the biomass fuel is pressed and pulverized between the pulverization roller 46 and the pulverization table 45.

A scraper 48 is provided vertically below the mill table 45, and the scraper 48 discharges the biomass fuel and foreign matter accumulated on the bottom surface portion 40 of the casing 41 to the outside of the casing 41. The scraper 48 is fixed to a part of the mill table 45 and is rotatable coaxially with the mill table 45. A brush 49 is provided at the tip of the scraper 48. Brush 49 is disposed so that the lower end thereof abuts the upper surface of bottom surface 40 of case 41, and slides on the upper surface of bottom surface 40. Further, a discharge opening 50 is formed in the rotation orbit of the brush portion 49 at the bottom surface portion 40 of the housing 41. The discharge opening 50 communicates with a pyrite storage tank 52 disposed outside the casing 41 via a discharge pipe 51.

A hot air supply duct 15 (refer to fig. 1) is connected to a lower portion of the connection housing 41. The hot air supply pipe 15 includes: a preheated air flow pipe 15b through which air preheated by the air preheater 19 flows; a cooling air flow pipe 15c through which cooling air bypassing the air preheater 19 flows; a merging section 15a that merges (mixes) the preheated air flowing through the preheated air flow pipe 15b and the cooling air flowing through the cooling air flow pipe 15 c; and a mixed air flow pipe 15d for circulating the air mixed at the merging portion 15 a. The mixed air flow passage 15d communicates with the housing 41. The air is supplied from the sub-1 st ventilation fan 17, and the preheated air heated by the air preheater 19 and the cold air supplied bypassing the air preheater 19 are supplied, and the preheated air and the cold air are controlled so that the temperature of the hot air is within a predetermined range at the junction 15 a. Further, a part of the exhaust gas passing through the electric dust collector 23 is introduced via the gas recirculation fan 21, and the oxygen concentration of the hot air is adjusted by the exhaust gas.

A part of the cooling air flow duct 15c is formed of, for example, a flexible expansion/contraction portion 47 to allow expansion/contraction in the extending direction of the cooling air flow duct 15 c. The expansion/contraction portion 47 is formed so as to be ruptured (opened) when the pressure inside the hot air supply pipe 15 reaches a predetermined pressure. The predetermined pressure at which the expansion/contraction portion 47 ruptures is set according to the pressure in the housing 41 in the normal operation state. Specifically, the pressure is set to be higher than the pressure applied to the expansion/contraction part 47 during normal operation of the pulverizer 5 (i.e., in a state where no abnormality such as rapid combustion occurs), and lower than the pressure at which various devices (e.g., the 1-time ventilator 17 and the air preheater 19) disposed on the upstream side of the flow of the hot air supplied to the hot air supply pipe 15 are damaged. In the present embodiment, the stretchable part 47 is creased, but the present invention is not limited to this, and may be creased (opened) at a part of the flange joint part or at another replaceable part such as a measuring seat.

As indicated by an arrow a1, the hot air supplied from the hot air supply pipe 15 is introduced into the casing 41 and supplied to the lower space S1 located below the pulverization table 45.

In fig. 2, the piping for circulating the exhaust gas from the gas recirculation fan 21 is omitted for the sake of illustration.

A space having a possibility of ignition and rapid combustion is explained. In the present embodiment, the lower space S1, the upper space S2, and the classification space S3 correspond to each other.

A side wall portion of the case 41 forming the lower space S1 is provided with a fire extinguishing agent spraying device 60 that sprays a fire extinguishing agent into the lower space S1. The fire extinguishing agent spraying device 60 includes the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B. The 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B are provided in pairs. That is, the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B are disposed close to each other. In addition, the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B may be separately disposed.

In the present embodiment shown in fig. 2, for example, 2 fire extinguishing agent spraying devices 60 (2 fire extinguishing

agent spraying portions

60A and 60B, respectively) are provided in the lower space S1 so as to face each other with the center axis of the housing 41 interposed therebetween. However, the number of the fire extinguishing agent spraying devices 60 is not limited to 2, and is determined according to the size of the lower space S1.

The pressure sensor 61 may be provided at a position indicated by an x mark in the lower space S1. The pressure sensor 61 includes a1 st pressure sensor 61A and a2 nd pressure sensor 61B, and the 1 st pressure sensor 61A and the 2 nd pressure sensor 61B are provided in a pair. That is, the 1 st pressure sensor 61A and the 2 nd pressure sensor 61B are disposed close to each other. In addition, the 1 st pressure sensor 61A and the 2 nd pressure sensor 61B may be separately arranged.

The pressure sensor 61 in the lower space S1 can be omitted (described later).

A rotary classifier (classifier) 53 is provided at an upper portion of the casing 41. The rotary classifier 53 is disposed so as to surround the fuel supply pipe 43, and rotates around the fuel supply pipe 43. As the rotary classifier 53 rotates, the plurality of blades 53a attached to the outer peripheral side thereof travel in the circumferential direction. The fine biomass fuel particles pulverized by the pulverization table 45 and the pulverization rollers 46 are entrained upward by the flow of the hot air (refer to arrow a2) that passes through the outer peripheral side of the pulverization table 45 from the lower space S1 and rises. The fine powder having a relatively large diameter among the fine powder that has been hoisted is dropped by the blade 53a, returned to the grinding table 45, and ground again. Thereby, the fine particles of the biomass fuel having a predetermined diameter or less are classified by the size of the fine particles by the rotary classifier 53, and the fine particles of the biomass fuel are conveyed and carried out from the fine particle fuel supply pipe 7 together with the hot air.

An upper space S2 is formed between the upstream side of the rotary classifier 53 (the lower side of the rotary classifier 53) and the upper side of the pulverization table 45. A side wall portion of the housing 41 forming the upper space S2 is provided with a fire extinguishing agent spraying device 60 that sprays a fire extinguishing agent into the upper space S2. In fig. 2, for example, 2 fire extinguishing agent spraying devices 60 are provided in the upper space S2, and are provided so as to face each other across the center axis of the housing 41 and form a pair. The number of the fire extinguishing agent spraying devices 60 is not limited to 2. However, the number of the fire extinguishing agent spraying devices 60 is determined according to the size of the upper space S2.

In the case where 2 fire extinguishing agent spraying devices 60 are provided, for example, so as to be opposed and paired across the central axis of the housing 41, the fire extinguishing agent spraying devices 60 of the upper space S2 and the fire extinguishing agent spraying devices 60 of the lower space S1 need not be at the same position in the circumferential direction of the housing 41 and may be offset from each other in the circumferential direction. Therefore, the fire extinguishing agent can be sprayed in two large areas, the upper space S2 and the lower space S1, with less variation.

A pressure sensor 61 for detecting rapid combustion is provided at a position indicated by an x mark in the upper space S2. The number of pressure sensors 61 is determined according to the volume in the headspace S2, and is set to 2, for example, in the present embodiment shown in fig. 2. The number of the pressure sensors 61 is not limited to 2.

The fine powder fuel supply pipe 7 is connected to the ceiling portion 42. The fine fuel supply pipe 7 discharges the fine biomass fuel particles classified by the rotary classifier 53 as indicated by an arrow a3 together with the hot air, and introduces the particles into the boiler main body 3 (see fig. 1). A classification space S3 is formed in a space on the downstream side of the rotary classifier 53 and on the upstream side of the fine powder fuel supply pipe 7 (i.e., a space inside surrounded by the vanes 53a of the rotary classifier 53).

A fire extinguishing agent spraying device 60 for spraying a fire extinguishing agent into the classification space S3 is provided in the ceiling portion 42 forming the classification space S3. In fig. 2, for example, 1 extinguishing agent spraying device 60 is provided in the classification space S3. The number of the fire extinguishing agent spraying devices 60 is not limited to 1. However, the number of the fire extinguishing agent spraying devices 60 is determined according to the size of the classification space S3.

A pressure sensor 61 for detecting rapid combustion is provided at a position indicated by an x mark in the classification space S3. The number of pressure sensors 61 provided in the classification space S3 is determined according to the volume in the classification space S3, and is, for example, 1 in the present embodiment shown in fig. 2. The number of the pressure sensors 61 is not limited to 1.

The type of fire extinguishing agent injected from the fire extinguishing agent injection devices 60 installed in the lower space S1, the upper space S2, and the classification space S3 (i.e., the fire extinguishing agent injected from the 1 st fire extinguishing agent injection unit 60A and the 2 nd fire extinguishing agent injection unit 60B) is not particularly limited as long as it has a fire extinguishing function, and for example, powder (sodium bicarbonate, usually sodium bicarbonate, etc.) may be used.

The pressure sensors 61 provided in the lower space S1, the upper space S2, and the classifying space S3 detect a pressure rise when the biomass fuel ignites and burns rapidly in the pulverizer 5. The output of the pressure sensor 61 is sent to a control unit not shown. The control unit determines the occurrence of rapid combustion based on the pressure value transmitted from the pressure sensor 61, and controls the operation of the fire extinguishing agent spraying device 60 provided in the lower space S1, the upper space S2, and the classification space S3 based on the result.

More specifically, as described below, the control unit determines the occurrence of rapid combustion and controls the operation of the fire extinguishing agent spraying device 60.

The control unit always grasps the operation state of the crusher 5. The control unit may automatically determine the operation state of the crusher 5 or may manually input the operation state.

When the operating state of the pulverizer 5 is the normal operating state (1 st operating state), the control unit determines that the rapid combustion has occurred when the pressure detected by the 1 st pressure sensor 61A exceeds a predetermined 1 st threshold value. When the control unit determines that rapid combustion has occurred during the normal operation, the control unit controls the fire extinguishing agent injection unit 60A to inject the fire extinguishing agent from the 1 st fire extinguishing agent injection unit substantially simultaneously with the rapid combustion.

When the operating state of the pulverizer 5 is the stopped state (2 nd operating state), the control unit determines that rapid combustion has occurred even when the pressure detected by the 2 nd pressure sensor 61B exceeds the predetermined 2 nd threshold value. When the control unit determines that rapid combustion has occurred in the stopped state, the control unit controls the second fire extinguishing agent spraying unit 60B to spray the fire extinguishing agent substantially simultaneously therewith.

The normal operation state is an operation state in which the biomass fuel is pulverized into fine powder in the pulverizer 5, and the pulverized fine powder of the biomass fuel is supplied to the boiler main body 3 by hot air for conveyance. The operation stop state is an operation state including both a state in which the crusher 5 is stopped (at the time of stopping the operation) and a state in which the crusher is transitioned to the operation stop state (at the time of transitioning to the operation stop state). In the state of transition to the shutdown operation, the method includes: a cleaning state in which the rotary separator 53 is rotated at a high speed and the rotary separator 53 is cleaned; and an empty state in which the biomass fuel and the hot air are not supplied into the housing 41, the mill table 45 and the scraper 48 are rotated, and the biomass fuel is discharged from the mill 5; and the like.

The determination of the occurrence of rapid combustion by the control unit may be performed as follows. When any one of the pressure sensors 61 provided in the lower space S1, the upper space S2, and the classifying space S3 detects a pressure exceeding a predetermined threshold value, the control unit determines that rapid combustion has occurred. Alternatively, in the case where 2 of the 31 st pressure sensors 61A configured by 2 of the pressure sensors 61 provided in the upper space S2 and 1 of the 1 st pressure sensors 61A provided in the pressure sensor 61 of the classification space S3 detect a pressure exceeding a predetermined threshold value in the normal operation state, it is possible to determine that rapid combustion is occurring and suppress erroneous determination. Similarly, in the operation stop state, when 2 of the 3 2 nd pressure sensors 61B including the 2 nd pressure sensors 61B of the pressure sensors 61 provided in the upper space S2 and the 1 nd pressure sensor 61B of the pressure sensors 61 provided in the classifying space S3 detect a pressure exceeding a predetermined threshold, the control unit may determine that rapid combustion is occurring and suppress an erroneous determination. When the control unit determines that rapid combustion has occurred, the control unit controls the fire extinguishing agent injection device 60 to inject the fire extinguishing agent from the lower space S1, the upper space S2, and the classification space S3 at substantially the same time.

The 1 st threshold is set according to the pressure in the housing 41 in the normal operation state. Specifically, the predetermined pressure (for example, 200Aq or more and 500Aq or less) is set to a pressure obtained by adding the pressure in the case 41 during normal operation in the normal operation state. The 2 nd threshold is set according to the maximum pressure in the casing 41 in the stopped state. Specifically, in the operation stop state, the pressure value differs depending on each operation state, and therefore, the predetermined pressure (for example, 200Aq or more and 500Aq or less) is set to a pressure obtained by adding the highest pressure in the casing 41 during normal operation. Further, since the pressure in the case during normal operation and the pressure in the case 41 during normal operation in the stopped state are different pressure values, the 1 st threshold value and the 2 nd threshold value are different pressures. Specifically, in the stop operation state, a large amount of inert gas is supplied into the casing 41 in an empty state in which the biomass fuel is discharged from the pulverizer 5, and the like, and therefore, the pressure becomes higher than that in the normal operation. That is, in the operation stop state, the operation of injecting the inert gas is performed to reduce the oxygen concentration in the casing 41, and the internal pressure of the casing 41 is increased in accordance with the amount of the medium to be injected. The 2 nd threshold is set higher than the 1 st threshold.

The control Unit includes, for example, a CPU (Central Processing Unit), a RAM (Random access Memory), a ROM (Read Only Memory), a computer-readable storage medium, and the like. Further, as an example of a series of processes for realizing various functions, various functions are realized by storing a program in a storage medium or the like, reading the program out of a RAM or the like by a CPU, and executing processing and arithmetic processing of information. The program may be installed in advance in a ROM or another storage medium, provided in a state of being stored in a computer-readable storage medium, transmitted via a wired or wireless communication means, or the like. The computer-readable storage medium refers to a magnetic disk, an optical magnetic disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The reason why the fire extinguishing agent spraying device 60 is provided in the lower space S1, the upper space S2, and the classification space S3 will be described.

The reason why the fire extinguishing agent spraying device 60 is provided in the upper space S2 and the classifying space S3 is that: in the upper space S2, a large amount of biomass fuel after pulverization exists due to the upper portion of the pulverization table 45; and in the classification space S3, there is a large amount of biomass fuel that becomes fine powder, and when the hot air that becomes the carrier gas is heated, ignition is easier than in other spaces. Moreover, this is because: the spark is generated due to the presence of volatile matter and foreign matter from the biomass fuel, and the spark is a space that is more easily ignited than other spaces, and is a space that exists as fine powder, has a large surface area, and is easily ignited. Therefore, in such a space, the pressure sensor 61 is further provided, and fire can be extinguished at an appropriate timing.

On the other hand, the lower space S1 is below the mill table 45, and the biomass fuel milled on the mill table 45 is entrained by the hot air supplied to the lower space S1, so the amount of fine powder present is smaller than the upper space S2. However, since the space is a space in which a large amount of hot air is supplied while containing a large amount of fine particles of biomass fuel, there is a possibility that ignition may occur in comparison with other spaces. Accordingly, the fire extinguishing agent spraying device 60 is provided. However, the pressure sensor 61 may be omitted, and the signals of the pressure sensor 61 of the upper space S2 and the classifying space S3 near the lower space S1 may be used.

As described above, the hot air is supplied from the hot air supply pipe 15 to the lower space S1, passes through the upper space S2, passes through the classification space S3, and flows into the fine powder fuel supply pipe 7. The fuel pulverized between the pulverizing roller 46 and the pulverizing table 45 is turned into fine powder, is entrained by hot air, passes through the rotary classifier 53, is classified, and then passes through the fine powder fuel supply pipe 7 and is introduced into the burner 9 of the boiler main body 3. Therefore, there is a space affected by rapid combustion in addition to the lower space S1, the upper space S2, and the classifying space S3.

Next, a space in which ignition occurs in a space different from the space in which ignition occurs and rapid combustion occurs and in which ignition occurs in another space and delay of rapid combustion may occur will be described. In the present embodiment, the fuel supply pipe 43, the hot air supply pipe 15, and the fine powder fuel supply pipe 7 correspond.

The fire extinguishing agent spraying device 60 is also provided in the fuel supply pipe 43, the hot air supply pipe 15, and the fine powder fuel supply pipe 7. The fire extinguishing agent spraying device 60 provided in the hot air supply pipe 15 is provided on the downstream side of the flow of hot air with respect to the junction 15 a. Each fire extinguishing agent spraying device 60 is controlled by the control unit, as in the fire extinguishing agent spraying device 60 described above. The delay of rapid combustion can be prevented by these fire extinguishing agent spraying means 60.

In addition, in the case of a space having a capacity in which the fire extinguishing agent spraying device 60 provided in the hot air supply pipe 15 can be omitted, in some cases, when the expansion/contraction portion 47 that is ruptured at a predetermined pressure is provided in a part of the cooling air circulation pipe 15c, the pressure in the hot air supply pipe 15 cannot be set to a predetermined pressure or higher by rupturing of the expansion/contraction portion 47, and therefore, a space having a capacity of rapid combustion and delay of combustion can be suppressed.

Further, since there is a possibility of ignition, it is necessary to provide the fire extinguishing agent spraying device 60 in the fuel supply pipe 43, the hot air supply pipe 15, and the fine powder fuel supply pipe 7, but since there is a low possibility of ignition, it is not necessary to provide the pressure sensor 61, and it is preferable to spray the fire extinguishing agent at an appropriate timing in consideration of the propagation time of rapid combustion by using the signals of the pressure sensor 61 in the upper space S2 and the classification space S3 close to the space where ignition is performed.

The location of the fire extinguishing agent spraying device 60 is set in consideration of the propagation time of rapid combustion. Specifically, when rapid combustion occurs, the fire extinguishing device is provided at a position where the fire extinguishing device can be sprayed before and after the rapidly-burning flame propagates. By spraying the fire extinguishing agent before and after the propagation of the delay burn reaches, the pressure rise can be suppressed.

On the other hand, when the fire extinguishing agent spraying device 60 is installed at a position closer to a site where rapid combustion occurs than the proper position, the fire extinguishing agent is sprayed too quickly with respect to the spread of the flame, and therefore, the fire extinguishing agent is sprayed after passing through the fire extinguishing agent spraying device 60 in a state where the flame does not spread due to spread of the flame, and therefore, the spread of the flame is not effectively suppressed, and the flame spreads after spraying the fire extinguishing agent, and the pressure is increased.

In addition, when the installation position of the fire extinguishing agent spraying device 60 is farther from the rapid combustion occurrence portion than the proper position, the fire extinguishing agent is sprayed after propagation of the spread fire, and the fire is not extinguished in time, or the fire extinguishing agent needs to be put in a state where the propagation of the fire is larger than that in the design time, and a large amount of fire extinguishing agent is required compared to the desired fire extinguishing agent amount, and rapid combustion cannot be effectively suppressed. Therefore, this is a factor of increasing the cost.

The crusher 5 having the above-described structure operates as follows.

When the biomass fuel is fed from the fuel supply pipe 43 toward the center of the mill table 45 (see arrow a0), the biomass fuel is introduced to the outer peripheral side of the mill table 45 by the centrifugal force caused by the rotation of the mill table 45, and is nipped between the mill table 45 and the mill roller 46 to be milled. The pulverized biomass fuel is lifted upward by the hot air introduced from the hot air supply pipe 15 (see arrow a2), and is introduced into the rotary separator 53. In the rotary classifier 53, the fine particles having a relatively large diameter are dropped by the blade 53a and returned to the grinding table 45. The fine powder that has passed through the classification by the blade 53a is introduced into the fine powder fuel supply pipe 7 together with hot air, and is supplied to the burner 9 of the boiler main body 3 (see fig. 1).

In the case where the biomass fuel is ignited and the rapid combustion occurs in the normal operation state of the pulverizer 5 as described above, the control portion determines the occurrence of the rapid combustion based on the detection value of the 1 st pressure sensor 61A appropriately provided in each space, and ejects the fire extinguishing agent from each of the 1 st fire extinguishing agent ejection portions 60A appropriately provided in each space at an appropriate timing. When the biomass fuel is ignited and rapidly burns in the stopped state of the pulverizer 5, the control unit determines the occurrence of rapid combustion based on the detection value of the 2 nd pressure sensor 61B appropriately provided in each space, and ejects the fire extinguishing agent from each 2 nd fire extinguishing agent ejection unit 60B appropriately provided in each space at an appropriate timing.

Specifically, the control unit performs the following control.

First, the control unit determines the operation state of the crusher 5. When the operation state is the normal operation state, the 1 st pressure sensor 61A detects the pressure inside the housing 41 (pressure detection step), and sends the detected pressure to the control section. The control unit determines whether or not the pressure detected by the 1 st pressure sensor 61A is equal to or greater than the 1 st threshold. When the value is equal to or higher than the 1 st threshold value, it is determined that the biomass fuel is ignited and rapidly burned in the pulverizer 5, and the fire extinguishing agent is injected from each 1 st fire extinguishing agent injection portion 60A (1 st fire extinguishing agent injection step). If the detected pressure is lower than the 1 st threshold value, the operation state is judged. After the fire extinguishing agent is sprayed, the operation state is judged by returning to the step of judging the operation state. When the fire extinguishing agent injected from each 1 st fire extinguishing agent injection portion 60A is purged, the operation is shifted to the operation of stopping the crusher 5.

On the other hand, when the operating state is the stop state, the 2 nd pressure sensor 61B detects the pressure inside the housing 41 (pressure detection step), and transmits the detected pressure to the control unit. The control unit determines whether or not the pressure detected by the 2 nd pressure sensor 61B is equal to or greater than the 2 nd threshold value. When the value is not less than the 2 nd threshold value, it is determined that the biomass fuel is ignited and rapidly burned in the pulverizer 5, and the fire extinguishing agent is injected from each 2 nd fire extinguishing agent injection portion 60B (2 nd fire extinguishing agent injection step). If the detected pressure is lower than the 2 nd threshold value, the operation state is judged. When the fire extinguishing agent sprayed from each 2 nd fire extinguishing agent spraying portion 60B is purged, the operation is shifted to an operation of completely stopping the crusher 5.

According to the present embodiment, the following operational effects are exhibited.

In the pulverizer 5, rapid combustion may occur in any one of the normal operation state and the stop operation state.

In the present embodiment, different threshold values are set in the normal operation state and the stop operation state. Specifically, the 1 st threshold is set based on the pressure in the casing 41 in the normal operation state of the crusher 5, and the 2 nd threshold is set based on the pressure in the casing 41 in the stop state of the crusher 5. Although the pressure values during normal operation are different between the normal operation state and the stop operation state, by setting the threshold values corresponding to the respective operation states in this manner, the occurrence of rapid combustion in the casing 41 can be determined in any operation state.

In the normal operation state and the stop operation state, different fire extinguishing agent ejecting portions are operated. Therefore, in any operating state, since the fire extinguishing agent is prepared for each operating state, when rapid combustion occurs in the housing 41, the fire extinguishing agent can be sprayed to suppress the rapid combustion.

Therefore, for example, in the normal operation state, the rapid combustion occurs in the crusher 5, and the crusher 5 is stopped after the 1 st fire extinguishing agent injection part 60A injects the fire extinguishing agent to suppress the rapid combustion, so that even when the rapid combustion occurs again in the crusher 5 during the operation in the stopped state, the rapid combustion can be detected by the 2 nd pressure sensor 61B and the control part, and the rapid combustion occurring in the crusher 5 can be suppressed by injecting the fire extinguishing agent from the 2 nd fire extinguishing agent injection part 60B.

The 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B are provided in pairs. Thus, when the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B are installed and maintained, the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B can be installed at the same time. Therefore, as compared with the case where the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B are independently provided, the workload at the time of installation can be reduced, and the workload at the time of maintenance can also be reduced.

The expansion/contraction portion 47 provided in a part of the hot air supply pipe 15 is ruptured by a predetermined pressure acting from the inside. Accordingly, when rapid combustion occurs in the pulverizer 5 and the pressure in the casing 41 rises and propagates to the inside of the hot air supply pipe 15, the expansion/contraction portion 47 ruptures when the pressure in the hot air supply pipe 15 reaches a predetermined pressure. When the expansion/contraction portion 47 ruptures, the pressure is released from the ruptured portion, and therefore, the increase in pressure in the hot air supply pipe 15 can be suppressed. This can keep the pressure in the hot air supply pipe 15 at a predetermined pressure or lower. Therefore, the hot air supply pipe 15 can be prevented from being damaged except for the portion of the expansion portion 47 while the pressure in the hot air supply pipe 15 is higher than the expected pressure. Further, it is possible to prevent various devices on the upstream side of the flow of the hot air supplied through the hot air supply pipe 15 from being damaged by propagation of pressure. Further, since the expansion/contraction portion 47 is formed so that the damaged portion of the hot air supply pipe 15 can be easily replaced, the damaged portion can be easily repaired.

Further, by keeping the pressure in the hot air supply pipe 15 at the predetermined pressure or less, a rapid increase in the pressure in the housing of the pulverizer 5 is suppressed, and a local rapid increase in the density of the biomass fuel in which the fine particles are present can be suppressed, and the progress of rapid combustion in the housing 41 when the fire extinguishing agent is sprayed can be further suppressed, and rapid combustion in the pulverizer 5 when the fire extinguishing agent is sprayed can be more effectively suppressed.

Further, since the expansion/contraction portion 47 provided in a part of the hot air supply pipe 15 is ruptured, it is not necessary to separately provide a device such as a rupture plate for suppressing a pressure increase in the hot air supply pipe 15, and the pressure in the hot air supply pipe 15 can be released. Further, in the case where another device is provided in the existing pulverizer 5, a new space for arranging the device needs to be secured, and thus there is a possibility that the layout of the piping must be changed. Therefore, space saving and cost reduction can be achieved as compared with the case where another device or the like is provided.

In the present embodiment, the biomass fuel is pulverized by the solid fuel pulverized by the pulverizer 5, but the pulverized solid fuel is not limited to the biomass fuel and may be coal or the like having high ignitability. The pulverizer 5 may be configured to pulverize only coal or may be configured to pulverize only biomass fuel. The biomass fuel may be pulverized together with coal, or the pulverized coal and the biomass fuel may be switched.

In the present embodiment, the example in which the 1 st pressure sensor 61A and the 2 nd pressure sensor 61B are provided independently and pressure sensors for detecting pressure are used separately according to the operation state of the crusher 5 has been described, but the number of pressure sensors may be set to 1 and pressure may be detected by 1 pressure sensor in all the operation states.

[ 2 nd embodiment ]

Hereinafter, embodiment 2 of the present invention will be described.

The present embodiment differs from embodiment 1 in that the pulverizer 5 switches the form of pulverizing coal and biomass fuel. The other structures are the same as those of embodiment 1, and therefore, descriptions thereof are omitted.

In the present embodiment, the pressure sensor 61 is stopped when coal, which is a solid fuel having low ignitability, is pulverized. On the other hand, when biomass fuel, which is a solid fuel having high ignitability, is pulverized, the fire extinguishing agent spraying device 60, the pressure sensor 61, and the like are used by the method described in embodiment 1. In this way, the following switching is performed according to the type of the solid fuel pulverized by the pulverizer 5: the fire extinguishing agent is not sprayed or is sprayed from the 1 st fire extinguishing agent spraying part 60A and the 2 nd fire extinguishing agent spraying part 60B.

The switching between the stop and the operation of the pressure sensor 61 may be performed manually by an operator or automatically by a control unit.

Since the control unit determines rapid combustion from the pressure rise in the pulverizer 5, if a pressure rise due to another factor occurs although rapid combustion does not occur, there is a possibility that rapid combustion is erroneously determined to have occurred although rapid combustion does not actually occur. If such erroneous determination is made, unnecessary ejection of the fire extinguishing agent is performed (malfunction). In the present embodiment, when coal, which is a solid fuel having low ignitability (i.e., having a low possibility of causing rapid combustion), is pulverized, the fire extinguishing agent is not injected from the 1 st fire extinguishing agent injection part 60A and the 2 nd fire extinguishing agent injection part 60B. Therefore, even when the pressure is increased due to a factor other than rapid combustion in a state where rapid combustion is not generated, it is possible to prevent a malfunction in which the fire extinguishing agent is sprayed into the pulverizer 5.

In the case of pulverizing coal, which is a solid fuel with low ignitability, the 1 st and 2 nd threshold values may be adjusted to values (for example, 2000Aq or more) higher than the 1 st and 2 nd threshold values set in the case of using biomass, which is a fuel with higher ignitability than coal, as a solid fuel. When a biomass fuel, which is a solid fuel having high ignitability, is pulverized, the 1 st threshold value and the 2 nd threshold value are set as described in embodiment 1. In this way, the 1 st threshold and the 2 nd threshold are adjusted according to the type of the solid fuel. The adjustment of the 1 st threshold and the 2 nd threshold may be performed manually by an operator or automatically by a control unit.

In this way, by setting the pressure that cannot be actually reached when the coal is pulverized as a threshold value, the fire extinguishing agent spraying device 60 can be easily put into an inoperative state. Therefore, even when the pressure is increased due to a factor other than rapid combustion in a state where rapid combustion is not generated, it is possible to prevent a malfunction in which the fire extinguishing agent is sprayed into the pulverizer 5.

The present invention is not limited to the inventions according to the above embodiments, and can be modified as appropriate without departing from the scope of the invention. For example, although the fire extinguishing agent spraying devices 60 are provided in the fuel supply pipe 43, the hot air supply pipe 15, and the fine powder fuel supply pipe 7 in each of the above embodiments, the fire extinguishing agent spraying devices 60 may be provided in any 1 or 2 of them.

Description of reference numerals:

1-boiler equipment, 3-boiler body, 5-pulverizer, 7-fine powder fuel supply pipe, 9-burner, 11-silo for biomass, 13-hopper, 15-hot air supply pipe (conveying gas supply pipe), 15 b-preheated air circulation pipe, 15 c-cooled air circulation pipe, 15 d-mixed air circulation pipe, 17-1 time ventilator, 19-air preheater, 21-gas recirculation ventilator, 23-electric dust collector, 25-denitration device, 27-induction ventilator, 29-desulfurization device, 31-chimney, 40-bottom surface portion, 41-shell (frame), 42-ceiling portion, 43-fuel supply pipe, 44-base, 45-pulverizing table, 46-pulverizing roller, 47-telescoping section, 48-scraper, 52-pyrite reservoir, 60-fire-suppression-agent-spraying device, 60A-1 st fire-suppression-agent-spraying section, 60B-2 nd fire-suppression-agent-spraying section, 61-pressure sensor, 61A-1 st pressure sensor, 61B-2 nd pressure sensor.

Claims

1. A pulverizer for pulverizing a solid fuel into a fine powder, the pulverizer comprising:

a frame constituting a housing of the pulverizer;

a pressure sensor that detects a pressure inside the frame;

a1 st fire extinguishing agent spraying unit configured to spray a fire extinguishing agent into the housing when the pressure detected by the pressure sensor is equal to or greater than a1 st predetermined threshold value in a1 st operation state of the pulverizer; and

and a2 nd fire extinguishing agent spraying unit configured to spray a fire extinguishing agent into the housing when the pressure detected by the pressure sensor is equal to or higher than a2 nd threshold value, which is a threshold value different from the 1 st threshold value, in a2 nd operation state, which is an operation state different from the 1 st operation state of the crusher.

2. The pulverizer of claim 1,

the 1 st operating state is that the pulverizer is in a normal operating state,

the 2 nd operation state includes a stop operation state when the crusher stops operating and when the crusher transits to a stop operation state,

the 1 st threshold is set according to the pressure in the frame in the normal operation state,

the 2 nd threshold is set according to the highest pressure in the frame in the stop operation state.

3. The pulverizer of claim 2,

the 2 nd threshold is set higher than the 1 st threshold.

4. The pulverizer of any one of claims 1 to 3,

the 1 st fire extinguishing agent spraying part and the 2 nd fire extinguishing agent spraying part are provided in pairs.

5. The pulverizer of any one of claims 1 to 4,

the fire extinguishing agent is not injected from the 1 st fire extinguishing agent injection part and/or the 2 nd fire extinguishing agent injection part according to the type of the solid fuel.

6. The pulverizer according to any one of claims 1 to 5, comprising a carrier gas supply pipe through which a carrier gas supplied into the housing flows,

a part of the carrier gas supply pipe is opened when the pressure inside the carrier gas supply pipe is equal to or higher than a predetermined pressure.

7. A method of operating a pulverizer that pulverizes a solid fuel supplied into a casing constituting a casing, the method comprising:

a pressure detection step of detecting a pressure inside the frame;

a1 st fire extinguishing agent spraying step of spraying the fire extinguishing agent from a1 st fire extinguishing agent spraying portion into the housing when the pressure detected in the pressure detecting step is equal to or higher than a predetermined 1 st threshold value in a1 st operation state of the pulverizer; and

and a2 nd fire extinguishing agent spraying step of spraying the fire extinguishing agent from the 2 nd fire extinguishing agent spraying portion into the housing in a2 nd operation state in which the crusher is in an operation state different from the 1 st operation state, when the pressure detected in the pressure detecting step is not less than a2 nd threshold value which is a threshold value different from the 1 st threshold value.