JP7258635B2 - Boiler, boiler system and method of starting boiler - Google Patents

Description

The present invention relates to a boiler, a boiler system, and a method for starting a boiler.

A large-sized boiler such as a coal-fired boiler has a hollow, vertically installed furnace, and a plurality of combustion burners are circumferentially arranged on the wall of the furnace. In the coal-fired boiler, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is arranged in the flue. Then, using a forced draft fan for blowing the air necessary for combustion to the combustion burner, the combustion burner injects a mixture of fuel and air into the furnace to form a flame and generate combustion gas. be. In addition, an induced draft fan is provided on the downstream side of the flue, and by creating a negative pressure in the flue by the attractive force generated by the induced draft fan, the generated combustion gas flows through the flue and finally It is guided to the chimney and released into the atmosphere. A heat exchanger is installed in a region where the combustion gas flows, and superheated steam is generated by heating water or steam flowing inside the heat transfer tubes constituting the heat exchanger.

In such a boiler, when the boiler is started, the induced draft fan is started before the forced draft fan is started, so that the gas in the furnace is sucked out, so that the pressure in the furnace is lowered. At this time, if the pressure in the furnace becomes lower than the assumed pressure, the negative pressure may cause deformation of the furnace walls and the like forming the furnace. Further, when the lower end of the boiler is water-sealed, there is a possibility that the seal water inside the lower end of the boiler is excessively lifted up and the sealed state is released. In order to avoid such a problem, there is known a technique for keeping the pressure in the furnace within an appropriate range when starting the boiler (for example, Patent Document 1).

In Patent Document 1, a temperature detector that detects the gas temperature on the inlet side of the induced draft fan is provided, and in addition to the air flow rate command, the gas temperature on the inlet side of the induced draft fan detected by the temperature detector and the boiler load command By correcting the opening of the induced flow rate adjustment damper based on, and reducing the opening of the induced flow rate adjustment damper when starting a boiler with a low gas temperature, the induced force of the induced draft fan is prevented from becoming too large. A boiler is disclosed that is configured to.

JP-A-8-145338

In the boiler of Patent Literature 1, an excessive decrease in furnace internal pressure is suppressed by narrowing the opening of an induced draft flow rate adjusting damper that adjusts the induced draft flow rate of the induced draft fan. However, in recent years, the capacities of forced draft fans and induced draft fans have increased. Close the door and start booting. For this reason, when starting the induced draft fan before starting the forced draft fan, in order to suck out the gas in the furnace while temporarily not communicating with the atmosphere, an induced draft fan is used based on the pressure inside the furnace. The method of adjusting the induced force that adjusts the suction flow rate of the ventilator by adjusting the opening of the damper or rotor blade may not be able to control the damper or rotor blade opening in time, resulting in an excessive decrease in the pressure inside the furnace. There was a fear that it could not be suppressed quickly.

The present invention has been made in view of such circumstances, and a boiler, a boiler system, and a boiler that can suppress an excessive decrease in pressure in the furnace and maintain a sealed state when the boiler is started. The purpose is to provide a starting method.

In order to solve the above problems, the boiler, the boiler system, and the boiler start-up method of the present invention employ the following means.
A boiler according to an aspect of the present invention includes a furnace that generates combustion gas by burning fuel, a combustion gas flow path through which the combustion gas generated in the furnace flows, and a combustion gas from the furnace. a first ventilator for sucking out gas through a gas flow path and releasing it to the atmosphere, and when the gas in the furnace is sucked out by the first ventilator at the time of start-up, the inside of the furnace and the atmosphere are communicated. form an air supply path that

If the flow rate of the combustion gas sucked out of the furnace by the first ventilator increases, the pressure inside the furnace may drop excessively. In the above configuration, an air supply path is formed that communicates the furnace with the atmosphere when the gas in the furnace is sucked out by the first ventilator. As a result, when the pressure in the furnace drops when the first ventilator sucks gas out of the furnace, air flows into the furnace through the air supply path as the pressure drops. Therefore, an excessive decrease in the pressure inside the furnace can be suppressed, and a sealed state such as a water seal can be maintained.

Further, in the boiler according to one aspect of the present invention, the air supply path has an air duct that communicates the inside of the furnace with the atmosphere, and adjusting means that adjusts the flow rate of the air flowing through the air duct. and a control means for controlling the adjusting means so that a predetermined flow rate of air is supplied to the furnace when gas in the furnace is sucked out by the first ventilator at startup. good.

In the above configuration, the adjustment means is controlled so that a predetermined flow rate of air is supplied into the furnace when the gas in the furnace is sucked out by the first ventilator. As a result, when the first ventilator sucks gas out of the furnace, a predetermined flow rate of air flows into the furnace through the air duct. Therefore, an excessive decrease in the pressure inside the furnace can be suppressed, and a sealed state such as a water seal can be maintained.

Further, since a duct (air duct) is used as a route for supplying air into the furnace, air can be reliably supplied into the furnace.
The adjustment performed by the adjustment means includes a state in which almost no air flows through the air duct (that is, a state in which the air flow rate is approximately zero, or a state in which the air flow rate can be regarded as zero by closing the damper or rotor blades), and a state in which the air duct It also includes switching to and from a state in which air circulates inside.

Further, the boiler according to one aspect of the present invention includes a second ventilator provided in the air duct for supplying air into the furnace through the air duct, wherein the second ventilator includes a plurality of motors. A variable-pitch ventilator having an angle changing portion for changing angles of blades and a plurality of rotor blades, wherein the passage area of the air duct can be changed by changing the angles of the plurality of rotor blades. and the adjusting means may have the angle changing portion.

In the above configuration, the flow passage area of the air duct can be changed by changing the angles of the plurality of rotor blades of the second fan. That is, by changing the angles of the rotor blades of the second fan, the flow rate of the air flowing through the air duct can be adjusted. Therefore, when the first ventilator sucks gas out of the furnace, a predetermined flow rate of air can flow into the furnace through the air duct. Therefore, an excessive decrease in the pressure inside the furnace can be suppressed, and a sealed state such as a water seal can be maintained.

Further, in the boiler according to one aspect of the present invention, the second ventilator has a drive source for rotating a plurality of the rotor blades, and the control means controls the gas in the furnace by the first ventilator. The angle changer may be controlled so that the angles of the plurality of rotor blades do not exceed the upper limit torque of the drive source when the second fan starts to be driven.

When the second fan is rotationally driven, the torque required by the drive source varies depending on the angles of the plurality of rotor blades. In the above configuration, the angles of the plurality of rotor blades are made smaller in the closing direction than the angle that does not exceed the upper limit torque of the drive source when the second fan is started. As a result, it is possible to prevent the upper limit torque of the drive source from being exceeded when the second fan is started.

Further, the boiler according to an aspect of the present invention includes a valve portion provided in the air duct for adjusting the flow rate of air flowing through the air duct, and the adjusting means may include the valve portion. good.

In the above configuration, the flow rate of air flowing through the air duct can be adjusted by adjusting the opening degree of the valve portion. Therefore, when the first ventilator sucks gas out of the furnace and discharges it, a predetermined flow rate of air can flow into the furnace through the air duct. Therefore, an excessive decrease in the pressure inside the furnace can be suppressed, and a sealed state such as a water seal can be maintained.

Further, the boiler according to one aspect of the present invention includes a water tank that is provided vertically below the furnace and stores water so that the water surface is positioned at a predetermined height, and the air supply path is provided in the furnace and has an opening that communicates between the inside of the furnace and the outside of the furnace, and the opening is vertically above the water surface when fuel is not burned in the furnace, The furnace may be positioned vertically below the water surface by thermal expansion of the furnace when fuel is burned in the furnace.

In the above configuration, the opening formed in the lower part of the furnace is not positioned below, but above the water surface when fuel is not burned in the furnace. Therefore, air flows into the furnace through the opening when fuel is not burned in the furnace. As a result, when the first ventilator sucks gas out of the furnace when the boiler is started, a predetermined flow rate of air flows into the furnace through the opening. Therefore, an excessive decrease in the pressure inside the furnace can be suppressed, and a sealed state such as a water seal can be maintained while fuel is being burned in the furnace.

On the other hand, when fuel is burned in a furnace, heat generated by the combustion causes the furnace to thermally expand vertically. In the above configuration, the thermal expansion of the furnace causes the opening to be positioned underwater. When the openings are submerged in water, the furnace is sealed because no air can enter through the openings. That is, it is possible to prevent air from flowing into the furnace through the opening. Therefore, when the boiler finishes starting up and the temperature of the boiler starts to rise, the furnace is in a sealed state, so that the fuel is suitably burned in the furnace to generate fuel gas. be able to.

Further, in the above configuration, an air supply path that communicates the inside of the furnace with the atmosphere is formed by forming an opening in the furnace. As a result, the configuration can be simplified, for example, compared to a configuration in which an air supply path is formed by separately providing a duct or the like. In addition, thermal elongation switches between a state in which air is supplied to the furnace through the opening and a state in which air is not supplied. Therefore, for example, the configuration can be simplified compared to a configuration that switches between a state in which air is supplied and a state in which air is not supplied by special control.

A boiler system according to an aspect of the present invention includes any one of the boilers described above and a pulverizer that pulverizes solid fuel to be supplied to the boiler.

A method for starting a boiler according to an aspect of the present invention includes a furnace that generates combustion gas by burning fuel, a combustion gas flow path through which the combustion gas generated in the furnace flows, and a gas in the furnace. and a first ventilator for sucking out the combustion gas through the combustion gas flow path and discharging it into the atmosphere, wherein when the gas in the furnace is sucked out by the first ventilator, the furnace a step of forming an air supply path that communicates the inside of the device with the atmosphere.

Advantageous Effects of Invention According to the present invention, it is possible to suppress an excessive decrease in the pressure in the furnace when the boiler is started, and to maintain a sealed state.

1 is a schematic configuration diagram showing a coal-fired boiler according to an embodiment of the present invention; FIG. Fig. 2 is a schematic longitudinal sectional view showing the lower part of the furnace of Fig. 1 and a water ring conveyor; 2 is a graph showing changes in opening degrees of the IDF and FDF and pressure in the furnace when the boiler of FIG. 1 is started. FIG. 3 is a longitudinal sectional view showing a modification of FIG. 2; FIG. 3 is a longitudinal sectional view showing a modification of FIG. 2;

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a boiler, a boiler system, and a method for starting a boiler according to the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, the present invention includes a combination of each embodiment.

FIG. 1 is a schematic diagram showing the coal-fired boiler of this embodiment.

The boiler of the present embodiment uses, for example, pulverized coal pulverized coal as pulverized fuel (carbon-containing solid fuel), burns this pulverized coal with a combustion burner, recovers heat generated by this combustion, and supplies water or steam. It is a coal-fired (pulverized coal-fired) boiler capable of exchanging heat with and generating superheated steam. In the following description, "up" and "up" indicate the upper side in the vertical direction, and "down" and "lower side" indicate the lower side in the vertical direction.

A boiler system 1 according to the present embodiment includes a coal-fired boiler 10 and pulverizers 31, 32, 33, 34, 35, etc. for pulverizing coal to be supplied to the coal-fired boiler 10. FIG.

In this embodiment, as shown in FIG. 1 , a coal-fired boiler 10 has a furnace 11 , a combustion device 12 and a flue (combustion gas flow path) 13 . The furnace 11 has a hollow rectangular shape and is installed along the vertical direction. A furnace wall 11b (heat transfer tube) constituting the furnace 11 is composed of a plurality of evaporating tubes and fins connecting them, and suppresses temperature rise of the furnace wall 11b by exchanging heat with feed water and steam.

The combustion device 12 is provided on the lower side of the furnace wall 11 b that constitutes the furnace 11 . In this embodiment, the combustion device 12 has a plurality of combustion burners (eg 21, 22, 23, 24, 25) mounted on the furnace wall 11b. For example, the combustion burners 21, 22, 23, 24, and 25 are arranged in a plurality of stages along the vertical direction as one set, which are arranged at equal intervals along the circumferential direction. However, the shape of the furnace, the number of combustion burners in one stage, and the number of stages are not limited to this embodiment.

Each combustion burner 21 , 22 , 23 , 24 , 25 is connected to pulverizers (mills) 31 , 32 , 33 , 34 , 35 via pulverized coal supply pipes 26 , 27 , 28 , 29 , 30 . Although not shown, the crushers 31, 32, 33, 34, and 35 have, for example, a rotary table supported in a housing so as to be driven and rotatable, and a plurality of rollers 63 above the rotary table interlocking with the rotation of the rotary table. It is configured to be rotatably supported by the When the coal is fed between the plurality of rollers 63 and the rotary table, the coal is pulverized to a predetermined pulverized coal size, and classified by the carrier gas (primary air). , 27, 28, 29, 30 to the combustion burners 21, 22, 23, 24, 25.

Further, the furnace 11 is provided with a wind box 36 at the mounting position of each combustion burner 21, 22, 23, 24, 25, and one end of an air duct (air supply path) 37 is connected to the wind box 36. ing. The air duct 37 is provided with a forced draft fan (second fan) 38 at the other end. In the following description, the forced draft fan 38 is also called FDF (Forced Draft Fan). The forced draft fan 38 has a passage portion (not shown) through which gas passing through the forced draft fan 38 flows, a plurality of moving blades (not shown) arranged in the flow passage portion, and the plurality of moving blades are rotated. It is a so-called variable-pitch fan having a drive source (not shown) and an angle changing unit (not shown) for changing the angles of a plurality of rotor blades. The flow path part forms part of the air duct 37 . The forced draft fan 38 can change the angle of a plurality of moving blades so that the desired opening degree can be obtained from a fully closed state (opening degree of 0%) to a fully closed state (opening degree of 100%). can be done. In the forced draft fan 38, the larger the degree of opening, the larger the passage area of the passage portion, and the smaller the degree of opening, the smaller the passage area of the passage portion. The fully closed state means that each moving blade is arranged so as to be substantially perpendicular to the central axis of the flow channel, and substantially the entire cross section of the flow channel is closed by each moving blade. This is a state in which it can be assumed that air does not flow. The fully open state is a state in which each rotor blade is arranged so as to be substantially parallel to the central axis of the flow passage, and each rotor blade does not close the cross section of the flow passage. The angle of each rotor blade of the forced draft fan 38 is controlled by a controller 68 which will be described later.

Furthermore, the furnace 11 is provided with additional air nozzles 39 above the mounting positions of the combustion burners 21, 22, 23, 24 and 25. As shown in FIG. An end of a branch air duct 40 branched from the air duct 37 is connected to the additional air nozzle 39 . Therefore, the combustion air (fuel gas combustion air/secondary air) sent by the forced draft fan 38 is supplied from the air duct 37 to the wind box 36, and from this wind box 36 the combustion burners 21, 22, 23, . 24 , 25 , and additional air for combustion delivered by forced draft fan 38 can be supplied from branch air duct 40 to additional air nozzles 39 .

The flue 13 is connected to the upper part of the furnace 11 in the vertical direction. The flue 13 is provided with superheaters 41, 42, 43, reheaters 44, 45, and economizers 46, 47 as heat exchangers for recovering the heat of the combustion gas. Heat is exchanged between combustion gas generated by combustion and water or steam flowing through each heat exchanger.

A gas duct (combustion gas flow path) 48 through which combustion gas that has undergone heat exchange is discharged is connected to the downstream side of the flue 13 . An air heater (air preheater) 49 is provided between the gas duct 48 and the air duct 37 , and heat is exchanged between the air flowing through the air duct 37 and the combustion gas flowing through the gas duct 48 . , 23, 24, 25 can be heated.

A denitration catalyst 50 is provided in the flue 13 upstream of the air heater 49 . The denitrification catalyst 50 supplies a reducing agent such as ammonia or urea water, which has an action of reducing nitrogen oxides, into the flue 13, and causes the reaction between the nitrogen oxides and the reducing agent in the combustion gas to which the reducing agent is supplied. By promoting it, nitrogen oxides in the combustion gas are removed and reduced. A gas duct 48 connected to the flue 13 is provided with a dust processing device (electric dust collector, desulfurization device) 51, an induced draft fan (first fan) 52, etc. at a position downstream of the air heater 49. A chimney 53 is provided in the part. In the following description, the induced draft fan 52 is also referred to as an IDF (Induced Draft Fan). The induced draft fan 52 has a flow path (not shown) through which the gas passing through the induced draft fan 52 flows, a plurality of moving blades (not shown) arranged in the flow path, and a plurality of moving blades that rotate. It is a so-called variable pitch fan having a drive source (not shown) and an angle changing section (not shown) for changing the angles of a plurality of rotor blades. The flow path part constitutes a part of the gas duct 48 . The induced draft fan 52 changes the angle of a plurality of moving blades so that the degree of opening can be changed from a fully closed state (opening degree of 0%) to a fully closed state (opening degree of 100%) as desired. can be done. In the induced draft fan 52, the larger the degree of opening, the larger the flow passage area of the flow passage portion, and the smaller the degree of opening, the smaller the flow passage area of the flow passage portion. The fully closed state is a state in which each rotor blade is arranged so as to be substantially perpendicular to the central axis of the flow passage portion, and substantially the entire cross section of the flow passage portion is closed by each rotor blade. It is in a state where it can be considered that there is no circulation. The fully open state is a state in which each rotor blade is arranged so as to be substantially parallel to the central axis of the flow passage, and each rotor blade does not close the cross section of the flow passage. The angle of each rotor blade of the induced draft fan 52 is controlled by a control device 68 which will be described later.

On the other hand, when the pulverizers 31, 32, 33, 34, and 35 are driven, the pulverized coal fuel is fed through the pulverized coal supply pipes 26, 27, 28, 29, and 30 together with the carrier air to the combustion burners 21, 21, and 29. 22, 23, 24, 25. Also, heated combustion air is supplied from an air duct 37 to each combustion burner 21 , 22 , 23 , 24 , 25 via a wind box 36 . Then, the combustion burners 21, 22, 23, 24, and 25 blow into the furnace 11 a pulverized fuel mixture in which pulverized coal and a carrier gas (primary air) are mixed, and blow combustion air into the furnace 11. At this time, A flame can be formed by igniting the A flame is generated in the lower part of the furnace 11 , combustion gas rises in the furnace 11 and is discharged to the flue 13 .

In the lower area A of the furnace 11, the pulverized fuel mixture and the combustion air (secondary air) are combusted to generate a flame. The inside of the furnace 11 is maintained in a reducing atmosphere by setting the amount of air supplied to be less than the theoretical amount of air with respect to the amount of pulverized coal supplied. That is, in region B, NOx generated by combustion of pulverized coal is reduced in the furnace 11, and then additional air is additionally supplied from the additional air nozzle 39 to complete oxidative combustion of pulverized coal. The amount of NOx generated by combustion is reduced.

After that, the combustion gas undergoes heat exchange in the superheaters 41, 42, 43, the reheaters 44, 45, and the economizers 46, 47 arranged in the flue 13, and then the nitrogen oxides are reduced and removed by the denitration catalyst 50. After the particulate matter is removed and the sulfur content is removed by the dust processing device 51, the dust is discharged from the chimney 53 into the atmosphere.

Next, the bottom ash water seal conveyor 60 provided below the furnace 11 and below the furnace 11 according to the present embodiment will be described with reference to FIG.

As described above, since the furnace 11 has, for example, a hollow rectangular tube shape, a rectangular opening 11a is formed at the lower end of the furnace 11 . That is, the opening 11a communicates the interior of the furnace 11 with the exterior of the furnace 11 .
A bottom ash water seal conveyor 60 is provided below the furnace 11 . The bottom ash water-sealed conveyor 60 has a water tank 61 in which water is stored, and a conveyor 62 (DCC: Drag Chain Conveyer) arranged in the water tank 61 below the water surface 61a (that is, underwater). A water surface 61a of water stored in the water tank 61 is level-controlled and set to a predetermined height. Further, the lower part of the coal-fired boiler 10 is inserted into the upper part of the water tank 61 so that the predetermined height L1 from the lower end is positioned below the water surface 61a. That is, a predetermined height L1 (hereinafter referred to as "seal height L1") from the lower end of the coal-fired boiler 10 is located underwater. Since the lower end of the coal-fired boiler 10 is positioned in the water in this manner, air does not flow in from the lower end of the coal-fired boiler 10 . In other words, the lower end of the coal-fired boiler 10 is water-sealed by the water in the water tank 61 .

The seal height L1 is set to about 100 to 200 mm while the coal-fired boiler 10 is stopped (that is, the furnace 11 is not burning fuel). When the coal-fired boiler 10 is in operation (that is, when fuel is burned in the furnace 11), the furnace 11 thermally expands, so the seal height L1 is approximately 200 to 500 mm. Further, when the internal pressure of the furnace 11 becomes negative pressure, the water surface 61a positioned inside the furnace 11 rises due to the negative pressure (see arrow A1). On the other hand, along with this, the water surface 61a positioned outside the furnace 11 is lowered (see arrow A2). When the water surface 61a located outside the furnace 11 falls below the lower end of the coal-fired boiler 10, the sealed state of the furnace 11 is released. When the sealed state is released, the raised water surface 61 a rapidly descends, causing the water surface 61 a to become rippling and possibly causing water to spill out of the water tank 61 .
In the present embodiment, the internal pressure of the furnace 11 is set to, for example, about −4 kPa to −5 kPa or more as an internal pressure that does not deform the furnace wall and the like forming the furnace 11 due to the negative pressure, and the operating internal pressure of the furnace 11 is operated, for example, between -0.1 kPa and -0.3 kPa, and the predetermined minimum internal pressure at startup is set between -1 kPa and -3 kPa. In this case, since the seal height L1 is set as described above, even if the internal pressure of the furnace 11 becomes, for example, -2 kPa to -3 kPa at the time of start-up, the sealed state is not released and the water seal is maintained. A seal is maintained.

During operation of the coal-fired boiler 10 , combustion ash generated by burning solid fuel and combustion ash adhering to heat exchangers such as heat transfer tubes may fall to the bottom of the coal-fired boiler 10 . A conveyor 62 is provided to collect such fallen combustion ash and discharge it to the outside of the coal-fired boiler 10 .

The conveyor 62 is a so-called belt conveyor, and has a roller 63 that rotates by driving force from a conveyor driving device (not shown), and a belt 64 that moves in the direction of arrow A3 as the roller 63 rotates. . The belt 64 is endless and folded back at both ends in the longitudinal direction of the conveyor 62 . In addition, the conveyor 62 has a horizontal portion 65 positioned vertically below the coal-fired boiler 10 to receive the combustion ash dropped from the coal-fired boiler 10, and conveys the combustion ash received at the horizontal portion 65 to the outside of the coal-fired boiler 10. and an inclined portion 66 that The lower portions of the horizontal portion 65 and the inclined portion 66 are located inside the water tank 61 and below the water surface 61a (that is, underwater). The upper portion of the inclined portion 66 protrudes above the water surface 61a. Also, the upper end of the inclined portion 66 is located outside the water tank 61 .

Further, the coal-fired boiler 10 of this embodiment includes a control device (control means) 68 . The control device 68 controls the starting and stopping of the forced draft fan 38 and the induced draft fan 52 by controlling the driving sources provided in the forced draft fan 38 and the induced draft fan 52 . In addition, the control device 68 controls the angle changing units provided in the forced draft fan 38 and the induced draft fan 52, and changes the angles of the moving blades of the forced draft fan 38 and the induced draft fan 52, so that the forced draft fan 38 and the opening of the rotor blades of the induced draft fan 52 are controlled.

The control device 68 is composed of, 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. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program, for example, and the CPU reads out this program to a RAM or the like, and executes information processing and arithmetic processing. As a result, various functions are realized. The program may be pre-installed in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or delivered via wired or wireless communication means. etc. may be applied. Computer-readable storage media include magnetic disks, magneto-optical disks, CD-ROMs, DVD-ROMs, semiconductor memories, and the like.

Next, a method for starting the coal-fired boiler 10 according to this embodiment will be described with reference to FIG. The vertical axis in FIG. 3 indicates the internal pressure (kPa) of the furnace 11 and the degree of opening (%) of each fan, and the horizontal axis indicates time. In FIG. 3, the solid line indicates the internal pressure of the furnace 11, the dashed line indicates the opening of the rotor blade of the induced draft fan 52, and the dashed line indicates the opening of the forced draft fan 38 (FDF). . In the following, first, displacements such as the opening degrees of the moving blades of the induced draft fan 52 and the forced draft fan 38 will be described, and then changes in the internal pressure of the furnace 11 will be described.

First, as a premise, the rotor blades of the forced draft fan 38 and the induced draft fan 52 are fully opened while the coal-fired boiler 10 is stopped. Also, the moving blades of the forced draft fan 38 and the induced draft fan 52 are not rotating and are stopped. This is to keep the interior of the furnace 11 and the atmosphere in communication while the coal-fired boiler 10 is stopped. In this way, when starting up the coal-fired boiler 10 (timing T0 in FIG. 3), the rotor blades of the forced draft fan 38 and the induced draft fan 52 are fully opened (rotor blade opening 100%). ) and is in a stopped state.

The coal-fired boiler 10 is started, and after a predetermined time has passed (timing T1), the rotor blades of the forced draft fan 38 and the induced draft fan 52 are gradually closed to reduce the opening of the rotor blades. At this time, the speed at which the moving blades of the forced draft fan 38 are closed and the speed at which the moving blades of the induced draft fan 52 are closed are substantially the same. At this time, the forced draft fan 38 and the induced draft fan 52 have not yet started, and the rotor blades of each fan are not driven to rotate.
The reason why the opening of the moving blades of each fan is reduced before starting the forced draft fan 38 and the induced draft fan 52 is to reduce the torque required when starting each fan. . That is, the forced draft fan 38 and the induced draft fan 52 differ in the torque required by the drive source depending on the angle of the rotor blades. In principle, starting with a large blade opening tends to require more torque than starting with a small opening. For this reason, before starting the forced draft fan 38 and the induced draft fan 52, the opening of the rotor blades of each fan is reduced to reduce the required torque.

In this embodiment, the operation of closing the rotor blades of the forced draft fan 38 is stopped when the opening degree of the rotor blades of the forced draft fan 38 reaches, for example, 30% (timing T2). After the operation to close the rotor blades of the forced draft fan 38 is stopped, the opening of the rotor blades of the forced draft fan 38 is set to, for example, 30% until the activation of the forced draft fan 38 is completed (timing of T5 described later). maintain in condition. At this time, the operation of closing the moving blades of the induced draft fan 52 continues.
In this embodiment, the opening of the rotor blades of the forced draft fan 38 is set to 30%, for example. This opening is a moving blade opening that does not exceed the upper limit torque of the driving source of the forced draft fan 38 when the forced draft fan 38 is rotationally driven by the activation operation described later.

When the opening degree of the rotor blades of the induced draft fan 52 reaches 0% (fully closed state) (timing T3), the operation of closing the rotor blades of the induced draft fan 52 is stopped. At the same time, the rotor blades of the induced draft fan 52 are rotated to start the activation operation of the induced draft fan 52 . The induced draft fan 52 completes the starting operation by rotating the moving blades for a predetermined time (30 seconds as an example in this embodiment) while maintaining the fully closed state.

When the activation of the induced draft fan 52 is completed (timing T4), the rotor blades of the forced draft fan 38 are rotated to start the activation operation of the forced draft fan 38 . The forced draft fan 38 completes the starting operation by rotating the moving blades for a predetermined time (10 seconds as an example in this embodiment) while maintaining the opening degree of 30%.
In this way, the induced draft fan 52 and the forced draft fan 38 are not activated at the same time. This is because a large amount of power is required to start the induced draft fan 52 and the forced draft fan 38, and if the induced draft fan 52 and the forced draft fan 38 are simultaneously started, the current value exceeds the allowable value. This is because there is a risk of exceeding
Further, when the internal pressure of the furnace 11 becomes -2.0 kPa, for example, control of the opening degree of the rotor blades of the induced draft fan 52 is started. The opening of the rotor blades of the induced draft fan 52 is controlled based on the internal pressure of the furnace 11 and adjusted so that the internal pressure of the furnace 11 does not fall outside a predetermined range. In the present embodiment, since the internal pressure of the furnace 11 is −2.0 kPa at the timing of T4, control of the opening of the rotor blades of the induced draft fan 52 is started at the timing of T4. The timing for starting the control of the opening degree of the rotor blades of the fan 52 does not have to be T4 as long as the rotation of the induced draft fan 52 is stable.

At the timing (timing T5) after a predetermined time (10 seconds in this embodiment, for example) has elapsed from the start of the activation operation of the forced draft fan 38, activation of the forced draft fan 38 is completed. Further, when the air flow rate of the forced draft fan 38 reaches, for example, 30%, control of the opening degree of the rotor blade of the forced draft fan 38 is started. The opening of the rotor blades of the forced draft fan 38 is controlled based on the internal pressure of the furnace 11 and adjusted so that the internal pressure of the furnace 11 does not fall outside a predetermined range. 30% of the air flow rate of the forced draft fan 38 means 30% of the air flow rate when the moving blades of the forced draft fan 38 are fully opened and the air flow rate is 100%. The flow rate at 30% of the rotor blade opening when the machine 38 is started does not necessarily have to match.
In this embodiment, since the air flow rate of the forced draft fan 38 reaches 30% at the timing of T5, control of the opening of the moving blades of the forced draft fan 38 is started at the timing of T5. , the timing to start controlling the opening of the moving blades of the forced draft fan 38 may not be T5 if the rotation of the forced draft fan 38 is stable.

After timing T5, the state in which the opening degrees of the moving blades of the induced draft fan 52 and forced draft fan 38 are controlled based on the internal pressure of the furnace 11 is maintained. Thus, the coal-fired boiler 10 is started.

Next, changes in the internal pressure of the furnace 11 when the coal-fired boiler 10 is started will be described.
The internal pressure of the furnace 11 at the time of starting the coal-fired boiler 10 (timing of T0) is 0 kPa (atmospheric pressure). This is because, as described above, the interior of the furnace 11 and the atmosphere are in communication while the coal-fired boiler 10 is stopped. In addition, the internal pressure of the furnace 11 is maintained at 0 kPa (atmospheric pressure) until the start-up operation of the induced draft fan 52 is started at T3 (that is, until the rotor blades of the induced draft fan 52 are driven to rotate). There is almost no change from the start of the firing boiler 10.

From T3 to T4, the rotor blades of the induced draft fan 52 are rotating. Therefore, the gas inside the furnace 11 (combustion gas, etc. after combustion) is sucked out, so the internal pressure of the furnace 11 decreases. However, since the opening of the moving blades of the forced draft fan 38 is set to, for example, 30% in this embodiment, air flows into the furnace 11 through the air duct 37 as the internal pressure of the furnace 11 decreases. do. As a result, the decrease in the internal pressure of the furnace 11 is suppressed, so that the decrease in the internal pressure of the furnace 11 gradually slows down to about -2.0 kPa at timing T4, for example.

From T4 to T5, the rotor blades of forced draft fan 38 begin to rotate. Therefore, since air is supplied into the furnace 11, the internal pressure of the furnace 11 rises from about -0.1 kPa to about -0.3 kPa. After T5, the opening degrees of the rotor blades of the induced draft fan 52 and the forced draft fan 38 are controlled, so that it is controlled by the internal pressure of the furnace 11 and maintained at about -0.1 kPa to -0.3 kPa.

This embodiment has the following effects.

When the gas is sucked out of the furnace 11 by the induced draft fan 52, the pressure inside the furnace 11 may drop excessively. If the pressure inside the furnace 11 drops excessively, the water seal may be broken.
In this embodiment, at the time of starting the coal-fired boiler 10, when the gas in the furnace 11 (combustion gas after combustion) is sucked out by the induced draft fan 52 (after T3 in FIG. 3), a predetermined amount of gas is introduced into the furnace 11 The opening degree of the forced draft fan 38 is controlled so that the flow rate of air is supplied. Specifically, the opening degree of the forced draft fan 38 is set to 30%, for example. As a result, when the induced draft fan 52 sucks out gas from the furnace 11 , a predetermined flow rate of air flows into the furnace 11 via the air duct 37 . Therefore, an excessive decrease in the pressure inside the furnace 11 can be suppressed, and a sealed state such as a water seal can be maintained.

In addition, by suppressing a decrease in the pressure inside the furnace 11, it is possible to suppress the generation of large ripples on the water surface 61a and prevent the water from spilling out of the water tank 61. Therefore, it is possible to reduce the consumption of seal water and suppress the increase in operating costs.

Further, in order to prevent the sealing state of the water seal from being released due to an excessive decrease in the pressure inside the furnace 11, it is necessary to increase the capacity of the water tank 61 of the bottom ash water seal type conveyor 60 or reduce the seal height L1. A method such as making it longer is also conceivable. However, such a method requires modification or additional installation of equipment, which causes a problem of increased cost.
On the other hand, in the method according to the present embodiment, only by controlling the opening of the moving blades of the existing ventilator, it is possible to prevent the release of the sealed state such as the water seal due to an excessive decrease in the pressure inside the furnace 11. are doing. Therefore, there is no need to modify or add equipment. Therefore, an increase in cost can be suppressed compared to a method that requires remodeling or additional installation of equipment.

Further, since a duct (air duct 37) is used as a route for supplying air into the furnace 11, air can be supplied into the furnace 11 reliably.

Further, when the forced draft fan 38 is rotationally driven, the torque required by the drive source varies depending on the angles of the plurality of moving blades (that is, the opening degree of the moving blades). In this embodiment, the opening degree of the plurality of rotor blades is set to 30%, which is the rotor blade opening degree that does not exceed the upper limit torque of the drive source when the forced draft fan 38 is started.

The moving blade opening degree of the forced draft fan 38 is determined in consideration of the following points.
In the present embodiment, when the moving blade opening of the forced draft fan 38 is set to 25%, the amount of air supplied into the furnace 11 is insufficient for the amount of air sucked out by the induced draft fan 52. In some cases, the internal pressure drops below a predetermined value, and the sealed state such as a water seal may be released. From this point of view, it has been found that it is preferable for the moving blade opening of the forced draft fan 38 to be greater than 25%.

In the present embodiment, when the moving blade opening of the forced draft fan 38 is set to 40%, the amount of air supplied to the furnace 11 increases, so an excessive decrease in the internal pressure of the furnace 11 is sufficiently suppressed. Although it can be done, the problem arises that the torque load at start-up of forced draft fan 38 is increased.
Further, in the present embodiment, control of the opening of the moving blades of the forced draft fan 38 is started when the air flow rate of the forced draft fan 38 reaches 30%. Therefore, when the moving blade opening of the forced draft fan 38 is set to 40%, the air flow rate of the forced draft fan 38 reaches 30% before the startup of the forced draft fan 38 is completed. The opening of the rotor blades of the forced draft fan 38 is controlled without waiting for the start-up of the fan 38 to be completed.
From this point of view, it has been found that the rotor blade opening of the forced draft fan 38 is preferably less than 40%.

On the other hand, in the present embodiment, when the moving blade opening of the forced draft fan 38 is set to 30%, as described above, the internal pressure of the furnace 11 decreases at around the predetermined value (from -1 kPa to -3 kPa). Since it becomes possible to control the suction flow rate by adjusting the moving blade opening of the induced draft fan 52, it is possible to prevent the release of the sealed state such as the water seal. In addition, in the present embodiment, even when the rotor blade opening of the forced draft fan 38 is 30% compared to the state where the rotor blade of the forced draft fan 38 is fully closed (opening degree: 0%), the torque load when starting the forced draft fan 38 does not increase. Stable startup was possible. Since there is no increase in the torque load, it is possible to avoid exceeding the upper limit torque of the drive source when the forced draft fan 38 is started.
From the above, it is preferable that the opening degree of the rotor blades of the forced draft fan 38 at the start of the coal-fired boiler 10 in the present embodiment is larger than 25% and smaller than 40%. In particular, if the opening of the rotor blades of the forced draft fan 38 is set to 30%, an excessive decrease in the pressure inside the furnace 11 can be suppressed, and a sealed state such as a water seal can be maintained. It is possible not to exceed the upper limit torque of the drive source when the forced draft fan 38 is started.

[Modification 1]
Further, in the above-described embodiment, an example was described in which air is supplied into the furnace 11 by not fully closing the opening of the rotor blades of the forced draft fan 38 when the coal-fired boiler 10 is started. is not limited to this. For example, as indicated by the dashed line in FIG. 1, a branch duct 70 branching from the air duct 37 may be provided, and air may be supplied into the furnace 11 via this branch duct 70 . One end of the branch duct 70 communicates with the air duct 37 and the other end is open to the atmosphere. Further, the branch duct 70 is provided with a flow control valve 71 for adjusting the flow rate of the air flowing inside.

In this modification, when the coal-fired boiler 10 is started, the opening of the rotor blades of the forced draft fan 38 is not 30% but is fully closed from timing T3 to timing T5 in FIG. In addition, instead of setting the moving blade opening of the forced draft fan 38 to 30%, the flow control valve 71 is opened to allow a predetermined flow of air to pass through, and air is supplied into the furnace 11 through the branch duct 70. . When the coal-fired boiler 10 is completely started and the coal-fired boiler 10 is in a normal operating state, the flow control valve 71 is fully closed so that the air does not flow in or out through the branch duct 70. to

Even with this configuration, a predetermined flow rate of air can be supplied into the furnace 11 through the air duct 37 when the induced draft fan 52 sucks out gas from the furnace 11 . Therefore, an excessive decrease in the pressure inside the furnace 11 can be suppressed, and a sealed state such as a water seal can be maintained. On the other hand, during normal operation of the coal-fired boiler 10 , air can be prevented from flowing in or out through the branch duct 70 by fully closing the flow control valve 71 . Therefore, the coal-fired boiler 10 can be stably operated.

[Modification 2]
In the above embodiment, an example was described in which a predetermined flow rate of air is supplied into the furnace 11 through the air duct 37 when the induced draft draft fan 52 sucks out gas from the furnace 11, but the present invention is limited to this. not. For example, as shown in FIG. 4, when the coal-fired boiler 10 is stopped (that is, the furnace 11 is not burning fuel), the lower end of the furnace 11 on the vertically lower side is positioned above the water surface 61a. While the gap is formed, while the coal-fired boiler 10 is in operation (that is, in a state where fuel is being burned in the furnace 11), thermal elongation of the furnace 11 causes the lower end of the furnace 11 to rise as indicated by the dashed line in FIG. It is good also as a structure located in water.

By configuring in this way, when the coal-fired boiler 10 is started, in a state where the furnace 11 is not thermally expanded, the air inflow path (air supply A path 76 can be formed to position the water surface 61a so as to provide a gap that allows a predetermined flow rate of air to be supplied into the furnace 11 . Therefore, when the induced draft draft fan 52 sucks out gas from the furnace 11 , a predetermined flow rate of air can be supplied into the furnace 11 through the air inflow path 76 . Therefore, an excessive decrease in the pressure inside the furnace 11 can be suppressed, and a sealed state such as a water seal can be maintained. On the other hand, during normal operation of the coal-fired boiler 10, since the lower end of the coal-fired boiler 10 is located in the water, the air inflow path 76 disappears. can be prevented. Therefore, the coal-fired boiler 10 can be stably operated.

[Modification 3]
In the above embodiment, an example in which the bottom ash water-sealing conveyor 60 is used to seal the furnace 11 with a water-sealing seal has been described, but the present invention is not limited to this. For example, as shown in FIG. 5, a dry DCC 80 (Drag Chain Conveyer) may be provided in place of the bottom ash water-sealed conveyor 60 . In such a configuration, a seal structure 81 that seals the furnace 11 while permitting thermal expansion of the furnace 11 is provided between the furnace 11 and the dry DCC 80 .

The dry DCC 80 has a housing 82 forming an outer shell and a conveyor 83 housed inside the housing 82 . A space formed inside the housing 82 communicates with a space inside the furnace 11 . Also, the upper end of the housing 82 is fixed to the lower end of the furnace wall 11b via the seal structure 81 . Since the conveyor 83 is substantially the same as the conveyor 62 described in the first embodiment, detailed description thereof will be omitted.

The seal structure 81 is formed so as to be elastically deformed against loads applied from above and below. As a result, when the lower end of the furnace wall 11b moves downward due to thermal expansion of the furnace 11, the thermal expansion can be absorbed by elastic deformation of the seal structure 81 portion.

In the configuration provided with such a dry DCC 80, when the internal pressure of the furnace 11 becomes excessively lower than a predetermined range, the elastic deformation portion of the seal structure 81 of the dry DDC 80 may be damaged and the sealed state may not be maintained. have a nature. Moreover, if the internal pressure of the furnace 11 is further reduced, the furnace wall 11b, the housing 82 of the dry DCC 80, the flue, etc. may be deformed. Therefore, when the coal-fired boiler 10 is started, it is necessary to suppress excessive pressure drop in the furnace 11 .
Therefore, as in the above embodiment, when the coal-fired boiler 10 is started, when the gas in the furnace 11 (combustion gas after combustion) is sucked out by the induced draft fan 52 (after T3 in FIG. 3), the furnace 11 By controlling the opening of the forced draft fan 38 so that a predetermined flow rate of air is supplied to the inside of the furnace 11, an excessive decrease in the pressure inside the furnace 11 can be suppressed, and the sealed state can be maintained without damaging the seal structure. can be maintained. Moreover, deformation of the furnace wall 11b and the like can be suppressed.

It should be noted that the present invention is not limited to the inventions according to the above-described embodiments, and modifications can be made as appropriate without departing from the scope of the invention.

For example, in the above-described embodiment, the boiler of the present invention is a coal-fired boiler, but the boiler may use biomass, petroleum coke, petroleum residue, or the like as the solid fuel. Further, the fuel is not limited to solid fuel, and can be used in oil-fired boilers such as heavy oil, and gas (by-product gas) can also be used as fuel. For example, blast furnace gas (BFG: Blast Furnace Gas), which is a by-product gas generated in a large amount in the ironmaking process, can also be used. It can also be applied to co-firing of these fuels.
In particular, a boiler using BFG as fuel tends to have a larger capacity of the induced draft fan 52 than a boiler using coal as fuel. Therefore, when the boiler is started, the internal pressure of the furnace 11 is more likely to decrease than in a coal-fired boiler (for example, it may decrease to a maximum of -3 kPa). As a result, the water level of the sealing water of the water seal in the lower end portion of the boiler rises significantly, so there is a problem that the seal state of the water seal is likely to be released. Therefore, the boiler according to the present embodiment, which can suppress a decrease in the internal pressure of the furnace 11 when the boiler is started, is particularly effective for a boiler using BFG as fuel.

1: Boiler system 10: Coal-fired boiler (boiler)
11: Furnace 11a: Opening 11b: Furnace wall 12: Combustion device 13: Flue (combustion gas flow path)
21, 22, 23, 24, 25: combustion burners 26, 27, 28, 29, 30: pulverized coal supply pipes 31, 32, 33, 34, 35: pulverizer 36: wind box 37: air duct (air supply path )
38: Forced draft fan (second fan, FDF)
39: Additional air nozzle 40: Branch air ducts 41, 42, 43: Superheaters 44, 45: Reheaters 46, 47: Economizer 48: Gas duct (combustion gas flow path)
49: Air heater 50: Denitrification catalyst 51: Dust treatment device 52: Induced draft fan (first fan, IDF)
53: Chimney 60: Bottom ash water-sealed conveyor 61: Water tank 61a: Water surface 62: Conveyor 63: Roller 64: Belt 65: Horizontal part 66: Inclined part 68: Control device (control means)
70: Branch duct 71: Flow control valve (valve portion)
76: Air inflow path 80: Dry DCC
81: Seal structure 82: Housing 83: Conveyor

Claims (6)

a furnace for generating combustion gases by burning fuel;
a combustion gas flow path through which combustion gas generated in the furnace flows;
a first ventilator for sucking gas from the furnace through the combustion gas flow path and releasing it to the atmosphere;
an air supply path that has an air duct that communicates the interior of the furnace with the atmosphere, and communicates the interior of the furnace with the atmosphere when gas in the furnace is sucked out by the first ventilator at startup; ,
adjusting means for adjusting the flow rate of air flowing through the air duct;
a control means for controlling the adjusting means so that a predetermined flow rate of air is supplied to the furnace when gas in the furnace is sucked out by the first ventilator at startup;
a second ventilator provided in the air duct and supplying air into the furnace through the air duct;
The second fan is a variable-pitch fan having a plurality of moving blades and an angle changing unit for changing the angles of the plurality of moving blades, and by changing the angles of the plurality of moving blades, A flow area of the air duct can be changed,
The adjusting means has the angle changing portion,
When the gas in the furnace is sucked out by the first ventilator at startup, the control means controls that the angle of the plurality of rotor blades of the second ventilator is greater than 25% and greater than 40%. A boiler that controls the angle changer so that the angle changer is within a small range. The second fan has a drive source that rotates the plurality of rotor blades,
The control means is configured such that, when gas in the furnace is sucked out by the first fan, the angle of the plurality of rotor blades does not exceed the upper limit torque of the drive source when the second fan starts to be driven. The boiler according to claim 1, wherein the angle changer is controlled such that a furnace for generating combustion gases by burning fuel;
a combustion gas flow path through which combustion gas generated in the furnace flows;
a first ventilator that sucks gas from the furnace through the combustion gas flow path and releases it to the atmosphere;
forming an air supply path that communicates the inside of the furnace with the atmosphere when gas in the furnace is sucked out by the first ventilator at startup,
The air supply path has an air duct that communicates the interior of the furnace with the atmosphere,
adjusting means for adjusting the flow rate of air flowing through the air duct;
a control means for controlling the adjusting means so that a predetermined flow rate of air is supplied to the furnace when gas in the furnace is sucked out by the first ventilator at startup;
a valve unit provided in a branch duct branching from the air duct and adjusting the flow rate of air flowing through the air duct,
The adjusting means is a boiler having the valve portion. a furnace for generating combustion gases by burning fuel;
a combustion gas flow path through which combustion gas generated in the furnace flows;
a first ventilator that sucks gas from the furnace through the combustion gas flow path and releases it to the atmosphere;
forming an air supply path that communicates the inside of the furnace with the atmosphere when gas in the furnace is sucked out by the first ventilator at startup,
Further comprising a water tank provided vertically below the furnace, in which water is stored so that the water surface is positioned at a predetermined height,
The air supply path is formed in a vertical lower part of the furnace and has an opening that communicates the inside of the furnace with the outside of the furnace,
The opening is positioned vertically above the water surface when fuel is not burned in the furnace, and vertically below the water surface due to thermal elongation of the furnace when fuel is burned in the furnace. boiler located in a boiler according to any one of claims 1 to 4;
and a pulverizer for pulverizing the solid fuel supplied to the boiler. A method for starting a boiler,
The boiler is
a furnace for generating combustion gases by burning fuel;
a combustion gas flow path through which combustion gas generated in the furnace flows;
a first ventilator that sucks out gas in the furnace through the combustion gas flow path and releases it to the atmosphere;
an air supply path that has an air duct that communicates the interior of the furnace with the atmosphere, and communicates the interior of the furnace with the atmosphere when gas in the furnace is sucked out by the first ventilator at startup; ,
adjusting means for adjusting the flow rate of air flowing through the air duct;
a control means for controlling the adjusting means so that a predetermined flow rate of air is supplied to the furnace when gas in the furnace is sucked out by the first ventilator at startup;
a second ventilator provided in the air duct and supplying air into the furnace through the air duct;
The second fan is a variable-pitch fan having a plurality of moving blades and an angle changing unit for changing the angles of the plurality of moving blades, and by changing the angles of the plurality of moving blades, A flow area of the air duct can be changed,
The adjusting means has the angle changing portion,
At the start of the boiler, when the gas in the furnace is sucked out by the first fan, the angle of the plurality of rotor blades of the second fan is larger than 25% and smaller than 40%. A boiler start-up method comprising the step of controlling the angle changer so as to fall within the range.

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