JP2010216728A - Method of controlling switching of fuel in boiler and boiler device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of stably controlling the switching of fuel in a boiler, and a boiler device, in switching the supply of a part of fuel to a furnace of the boiler at work with a main fuel from the main fuel to a gas fuel. <P>SOLUTION: The plurality of burners have burner sections of prescribed stages to a boiler unit applying pulverized coal fuel as the main fuel, and the gas fuel accompanied by the generation of BOG (boil off gas) of LNG (liquefied natural gas) excluding the main fuel can be supplied to the burner of the first stage. Control is performed so that the influence of the supply of gas fuel is gradually increased according to the decrease of the supply of the main fuel at a P1 time point in the burner of the first stage, and the supply of the gas fuel reaches a prescribed amount at a switching point α taking air at the neighborhood of a main fuel stop time point P7 when the main fuel is not supplied. The ignition timing (P3 time point) of the prescribed burner in the burner of the first stage is shifted, and the switching point α is moved at the neighborhood P7 of the main fuel stop time point. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a power plant that uses BOG generated during LNG storage as part of boiler fuel, and more particularly to a boiler fuel switching control method and a boiler device.

  2. Description of the Related Art A power plant that drives a steam turbine by driving a gas turbine or burning it with a boiler using LNG (liquid natural gas) as a fuel is known. The LNG power generation plant has an LNG tank as an LNG base facility for storing and protecting LNG.

  LNG is obtained by cooling natural gas to a temperature capable of liquefying (approximately −162 ° C. to −160 ° C.). Therefore, at the LNG terminal, it is indispensable to take measures against BOG (boil off gas) that is generated in a large amount in the LNG tank due to natural heat input or the like. For example, the overfilled BOG is led out of the LNG tank, burned and released to the atmosphere. In addition, it is boosted by a BOG compressor and supplied to the power plant as gas fuel (natural gas) for use as power generation energy. Measures are taken.

  A power plant that can use BOG more effectively includes, for example, a coal-fired boiler unit in addition to a gas-fired boiler unit (multi-fuel fired boiler system). Thereby, even if the operation of the gas fired boiler unit is stopped, the gas fuel can be supplied to the coal gas fired boiler unit. Therefore, BOG generated from the LNG tank is efficiently consumed as energy for power generation (see, for example, Patent Document 1).

  In such a multiple fuel fired boiler system, the coal gas co-fired boiler unit has a supply port for pulverized coal fuel and a supply port for gas fuel as fuel supply ports. The gas fuel accompanying the BOG generation of LNG is supplied to the gas fuel supply port of the coal gas fired boiler unit according to the supply amount to the gas fired boiler unit. That is, when the consumption of gas fuel in the gas-fired boiler unit is less than or equal to the amount of gas fuel associated with BOG generation, gas fuel associated with BOG generation of LNG is supplied to the gas fuel supply port of the coal gas fired boiler unit. To be controlled.

JP 2007-17030 A

  In the multi-fuel-fired boiler system as described above, for example, a coal gas co-fired boiler unit that uses pulverized coal fuel as the main fuel can supply a part of the fuel from the normal pulverized coal fuel supply for an arbitrary period. It is controlled to operate by switching to the supply of gas fuel.

  In the boiler fuel switching control for switching the supply of a part of the fuel into the furnace, an excessive fuel condition occurs during the period in which the two types of fuel are mixed and supplied into the furnace, and the main steam temperature is regulated. There is a problem of exceeding the value. As a general countermeasure for suppressing the main steam temperature rise, there is a spray control of cooling water for suppressing the rise of the furnace outlet temperature, but in the end, it is nothing but wasting fuel.

  In view of the above circumstances, an object of the present invention is to provide a stable boiler fuel switching control method that does not result in an excessive fuel state when switching a part of fuel supply into a furnace of a boiler operating with main fuel from main fuel to gas fuel. And providing a boiler device.

  In the present invention, for example, for a boiler unit having a first fuel, which is a solid fuel such as pulverized coal fuel or a liquid fuel such as heavy oil, as a main fuel, a part of the fuel is supplied from the main fuel to the gas fuel (if necessary). Regarding the control to be switched to gaseous fuel (second fuel) such as natural gas associated with BOG generation of LNG, efficiency is improved while utilizing an existing mechanism. In this case, taking into account the tendency of combustion to change due to changes in the furnace environment, such as soot and clinker sticking to the furnace wall of the boiler, the following solutions are provided. To do.

(1) For a boiler unit using the first fuel as a main fuel, each of the plurality of burners that can supply the first fuel includes an n-stage burner portion configured in a predetermined number of stages, The m (<n) stage burner portion can supply a second fuel that is a gaseous fuel other than the first fuel,
In the m-th stage burner part during operation of the boiler unit,
Increasing the influence of the supply of the second fuel to the boiler unit in response to decreasing the supply of the first fuel;
Allowing the supply amount of the second fuel to reach a predetermined amount at a switching point that is aimed near the first fuel stop point at which the supply of the first fuel ceases;
With
Shifting the ignition timing of a predetermined burner in the m-th stage burner portion to move the switching point near the supply stop time;
A boiler fuel switching control method.

  According to the boiler fuel switching control method described above, when the main steam temperature in the boiler unit changes outside the set range, for example, the ignition timing of a predetermined burner in the m-th stage burner portion capable of fuel switching is delayed. Control. The predetermined burner may be selected from among the m-th stage burner portions that can move the ignition timing relatively freely.

  In the boiler fuel switching control method, smooth switching can be realized by gradually increasing the supply amount of the second fuel from the first fuel while considering the ease of control of each mechanism for supplying fuel. In addition, the following features (2) and (3) may be provided.

  (2) Concerning the control for reducing the supply of the first fuel, a first stage in which the first fuel is decreased at a constant rate of change until reaching the first flow rate value, and the first flow rate value is maintained substantially constant. A boiler fuel switching control method comprising: a second stage; and a third stage until the supply of the first fuel to all the burners of the m-th stage burner unit is stopped.

(3) With respect to the m-th stage burner unit, the control of the second fuel is performed according to the first stage of opening the second fuel when the supply of the first fuel starts to be reduced, and according to the flow rate adjustment. A second step of changing the fuel flow rate to a second flow rate value that is greater than the first flow rate value, and a third step of maintaining the second flow rate value substantially constant as the switching point. And comprising
In the first stage, the first burner that has reached the first pressure is ignited, and in the second stage, after the predetermined burner that has reached the second pressure is ignited, the flow rate of the second fuel is kept constant. The remaining burners are sequentially ignited in the predetermined order on the condition that the predetermined pressure is reached in the increasing period,
The boiler fuel switching control method, wherein the predetermined burner ignition timing is selected from a predetermined range time after the first burner ignition.

  In addition, by providing each of the following configurations as the boiler device, the objective of realizing stable boiler fuel switching that does not cause an excessive fuel state when switching the fuel of an operating boiler is achieved.

(4) a boiler unit including an n-stage burner portion in which each of a plurality of burners capable of supplying a first fuel as a main fuel is configured in a predetermined number of stages;
An m (<n) stage burner portion capable of supplying a second fuel that is a gaseous fuel other than the first fuel among the burner portions;
A first control mechanism that reduces the supply of the first fuel stepwise in the m-th stage burner during operation of the boiler unit;
A period in which the second fuel is opened when the control to reduce the first fuel is started in the m-th stage burner during operation of the boiler unit, the flow rate of the second fuel is adjusted, and the flow rate is constantly increased. A second control mechanism that causes the supply amount of the second fuel to reach a predetermined amount at a switching point that is aimed at the vicinity of the first fuel stop time when the supply of the first fuel is eliminated.
A third control mechanism for shifting the ignition timing of a predetermined burner in the m-th stage burner section to move the switching point near the supply stop time;
Boiler device equipped with.

  According to the boiler apparatus, it is possible to cope with the third control mechanism when the main steam temperature changes outside the set range due to a change in the furnace environment of the boiler unit or the like. For example, it is possible to delay the ignition timing of a predetermined burner in the m-th stage burner portion that is the target of fuel switching. The predetermined burner may be selected from the control mechanism so that the ignition timing can be moved relatively freely. Further, the m-th stage burner portion including the predetermined burner may be configured as follows.

  (5) The m-th stage burner portion includes a predetermined number of burners that are ignited in a predetermined order from the time when the second fuel is opened, and when the second fuel is opened and reaches the first pressure. An initial ignition burner to be ignited and an ignition timing as the predetermined burner that reaches the second pressure by adjusting the flow rate of the second fuel and can be ignited after an arbitrary time has elapsed after the ignition of the initial ignition burner set in advance A boiler device comprising: a control burner; and an ignition follower burner group that is sequentially ignited on the condition that a predetermined pressure is reached in a period in which the flow rate of the second fuel is constantly increased.

  According to the present invention, when switching a part of the fuel supply into the furnace of a boiler operating with the main fuel from the main fuel to the second fuel, for example, the gas fuel accompanying the BOG generation of the LNG, an excessive fuel state is not caused. A stable boiler fuel switching control method and boiler apparatus can be provided.

It is a block diagram which shows the structural example of the boiler apparatus which concerns on the boiler fuel switching control method of this invention. It is a figure which shows the time-fuel supply amount which shows an example of the boiler fuel switching control method of this invention. It is a figure showing the detail of the ignition conditions of the gas burner in FIG. It is a flowchart of the process which shows an example of the boiler fuel switching control method of this invention. It is a block diagram which shows the structural example of the boiler apparatus which concerns on the modification of FIG.

  FIG. 1 is a block diagram showing an example of the configuration of a boiler apparatus according to the boiler fuel switching control method of the present invention. The boiler device mainly relates to the boiler unit 10, the coal supply system 15, the LNG supply facility 20, the valve control system 14, and the control device 13.

  The boiler unit 10 whose main fuel is coal (pulverized coal) includes a burner unit 12 that can supply pulverized coal fuel to the furnace 11. In the burner unit 12, each of a plurality of burners is configured in four stages (n = 4) in the furnace length direction. Although not shown in the figure, a plurality of exceptional burners are arranged in four rows in the horizontal direction of the furnace. The number and arrangement of the burners are determined depending on the capacity of the burner alone (maximum pulverized coal combustion amount, boiler capacity, etc.) and the boiler structure, and vary.

  The coal supply system 15 has, for example, a mechanism for transporting coal stored in a coal storage (not shown) to a coal bunker using a conveyor. Furthermore, the coal supply system 15 sends coal to a pulverized coal machine (mill) 16 (16-1 to 16-4) via a coal feeder provided at the lower part of the coal bunker. Coal is made into pulverized coal by the mill 16, and the pulverized coal is supplied to the burner unit 12 by a fuel blower (PAF) 17 (17-1 to 17-4).

  Of the burner unit 12, the first-stage burner unit 121 is a burner unit that can supply LNG (liquefied natural gas) that is a gaseous fuel other than the pulverized coal as the main fuel (m-th burner unit (m = 1)). More specifically, each burner of the first stage burner section 121 has a structure of a coal / gas coaxial burner in which a pulverized coal burner and a gas burner are coaxially arranged. The 2nd stage burner part 122, the 3rd stage burner part 123, and the 4th stage burner part 124 are pulverized coal burners. The first-stage burner unit 121 allows the boiler unit 10 to switch part of the fuel supply to gas fuel supply. For example, BOG (boil-off gas) generated in the LNG tank can be consumed as power generation energy. It is.

  The LNG supply facility 20 includes an LNG tank 21, a boost pump 22, a vaporizer 23, and a BOG compressor 24. The flare stack 25 is represented as a facility that burns BOG and releases it to the atmosphere. Since the present invention is configured to use BOG effectively, the flare stack 25 is used in an emergency, and normal use is abolished.

  The LNG tank 21 is a facility for storing liquefied natural gas (LNG) landed from a tanker. The boost pump 22 is connected to a take-out pipe (not shown) at the bottom of the LNG tank, and is connected to the vaporizer 23 on the downstream side thereof. The vaporizer 23 vaporizes the liquid LNG pumped up by the boost pump 22 to generate natural gas (NG).

  The upper space in the LNG tank 21 is filled with BOG that has been vaporized by LNG due to natural heat input or the like. BOG is introduced into the BOG compressor 24 via the BOG sampling pipe in the upper part of the tank, and is compressed and pressurized to natural gas (NG).

  Natural gas (NG) from the LNG supply facility 20 is normally supplied to a gas-only fired boiler unit (or low-pressure consumer). However, when the gas-fired boiler is stopped, or when the consumption of gas fuel in the gas-fired boiler unit or low-pressure consumer becomes less than the amount of natural gas fuel associated with BOG generation, the first stage burner part of the boiler unit 10 121 is controlled so that surplus gas fuel (natural gas NG) accompanying the generation of BOG is supplied.

  The control device 13 exchanges information of the LNG supply facility 20 and information of the coal supply system 15, and controls the mill 16, the PAF 17, and the burner unit 12 in accordance with these pieces of information. In addition, the control device 13 controls the valve control system 14 responsible for shutting off the natural gas (NG) flow path and adjusting the flow rate of the LNG supply facility 20.

  When the boiler unit 10 is in operation, the control device 13 receives information on the generation of surplus gas fuel from the LNG supply facility 20, a predetermined coal feeder (not shown) of the coal supply system 15, a mill 16-1 and a PAF 17-. 1 is controlled. As a result, the supply of pulverized coal to the first-stage burner unit 121 is reduced, and finally it is guided to stop. Further, the natural gas NG is guided to the first stage burner unit 121 through the valve control system 14 in accordance with the decrease in the supply of pulverized coal to the first stage burner unit 121. At this time, boiler fuel switching control is performed from the pulverized coal fuel to the natural gas gas fuel in the first stage burner unit 121.

  As described above, when boiler fuel switching control is performed during operation of the boiler unit 10, the temperature of the main steam generated through the heat exchanger 18 may fluctuate greatly. In particular, due to changes in the furnace environment over time, there is a tendency for the combustion method to change and lead to a rise in the temperature of the main steam. There is sex. The temperature detector 19 detects the temperature of the main steam, and the control device 13 acquires temperature information of the temperature detector 19. The control device 13 can adjust the boiler fuel switching control in the first stage burner unit 121 according to the temperature information of the temperature detector 19.

  FIG. 2 is a diagram showing a time-fuel supply amount showing an example of the boiler fuel switching control method of the present invention, and relates to boiler fuel switching control in the first stage burner portion 121 of the boiler unit 10 of FIG. FIG. 3 is a diagram showing details of the ignition conditions of the gas burner in FIG. This will be described with reference to FIG.

  The first-stage burner unit 121 has a structure in which each burner is provided with a pulverized coal burner and a gas burner coaxially as described above as compared with the burner units of other stages. The first-stage burner unit 121 is arranged in four rows in the horizontal direction of the furnace (not shown) in the same manner as the other-stage burner units, and these are arranged in the order of arrangement 1-A, 1-B, 1-C, 1-D. And The order of ignition of the gas burners in FIG. 2 is the order of 1-B gas burner, 1-C gas burner, 1-A gas burner, and 1-D gas burner. Each of these gas burners has a specification that can be ignited after 5 seconds when gas fuel is supplied and reaches each specified pressure (gas burner pressure), but further ignition conditions are added (see FIG. 3).

  In FIG. 2, the control start time is 0 minute. That is, the control device 13 starts control related to boiler fuel switching control in the first stage burner unit 121. The gas master is activated, the gas flow control valve rises to 10% of the leak check opening, 38% of the ignition opening of the first gas burner after 4 minutes, and then the second gas burner passes after 4 minutes 30 seconds or more. To 46% of the ignition opening. Thereafter, the gas flow control valve automatically adjusts with the setting of the specified flow rate. Such control of the gas flow rate control valve involves at least control of the valve control system 14 by the control device 13.

  The supply control of the pulverized coal fuel in the first stage burner 121 is as follows. At P1 when 5 minutes have elapsed from the control start time (0 minutes), the minimum flow rate is set for a predetermined coal feeder in the coal supply system 15 related to pulverized coal supply to the first stage burner unit 121. Along with this, the amount of pulverized coal fuel supplied to the first stage burner unit 121 is reduced substantially uniformly until time P6 when the normal amount is controlled from 15 t / h to 5 t / h. The time from P1 time to P6 time is around 9 minutes 30 seconds. At that time, the supply of coal to a predetermined coal feeder is shut off at the time P4 when the pulverized coal fuel supply amount is controlled to 7 t / h. Further, at the time P6, the predetermined mill master related to the control of the predetermined mill 16-1 is stopped. About 5 minutes and 30 seconds from the time P6 to the time P7, the amount of pulverized coal fuel supplied to the first stage burner 121 is maintained at 5 t / h, and the inside of the predetermined coal feeder is emptied. The predetermined coal feeder is stopped at P7, and the predetermined mill is stopped at P8 after 5 minutes.

  On the other hand, the supply amount of the natural gas NG to the first stage burner unit 121 is controlled as follows in accordance with the control of the gas flow control valve. The influence of the supply of gas fuel to the boiler unit 10 is increased in response to starting to decrease the amount of pulverized coal fuel supplied from the point P1. Here, the gas cutoff valve is opened at time P1. The control of the valve control system 14 by at least the control device 13 is also involved in the control of the gas cutoff valve.

  At P1, the gas flow rate control valve opening is 38%. When the gas shut-off valve is opened, the first 1-B gas burner reaches a specified pressure and is ignited (see FIG. 3). After the 1-B gas burner is ignited, the 1-C gas burner is subsequently ignited. The ignition timing of the 1-C gas burner is set when the gas flow rate control valve opening becomes 46% by the second gas burner ignition command.

  In addition to being able to ignite the 1-C gas burner when the specified gas burner pressure is reached, the ignition timing is controlled in a longer range than the other gas burners. Thus, the gas fuel supply amount is adjusted to reach a predetermined amount (6.5 t / h in this case) at the switching point α that is aimed at the vicinity of the point P7 when the supply of the pulverized coal fuel ceases. After ignition of the 1-C gas burner, the gas flow control valve opening is increased at a constant rate. As a result, the 1-A and 1-D gas burners are ignited in sequence at the appropriate time when the prescribed gas burner pressure is obtained.

  More specifically, the 1-C gas burner is ignited after the 1-B gas burner is ignited after a predetermined time period of 150 seconds to 450 seconds, more preferably 200 seconds to 400 seconds. 1-C gas burner) is adjusted according to the timing of the gas burner ignition command. After the 1-C gas burner is ignited, the gas flow rate control valve opening is increased at a constant rate, so that the switching point α can be moved near the point P7 by shifting the ignition timing of the 1-C gas burner. Here, after the ignition of the 1-B gas burner, the 1-C gas burner is ignited at the point P3 of 300 seconds, and the arrival time of the switching point α is adjusted to be several tens of seconds after the point P7.

  For example, in the boiler unit 10, in a relatively clean in-furnace environment in which no soot and clinker adhere to the furnace wall, the 1-C gas burner is P2 210 seconds after the ignition of the 1-B gas burner. Ignition control is performed at the time. Thereby, the gas fuel supply amount takes a rising trajectory as shown by the broken line NG1, and the gas fuel supply amount reaches a predetermined amount (6.5 t / h) before the time point P7 when the supply of the pulverized coal fuel stops. It reaches the switching point.

  In the relatively clean in-furnace environment, even such fuel switching control is not affected by the excessive fuel state. For example, the main steam temperature is kept at the rated main steam temperature + 8 ° C. or lower. However, if soot and clinker adhere to the furnace wall with the passage of time, and the way of combustion changes due to changes in the furnace environment, there is a high possibility that an excessive fuel condition will affect. For example, the main steam temperature has a time exceeding the rated main steam temperature + 8 ° C. in the dashed elliptical region OVR indicating the excessive fuel state in FIG. That is, in the control of the switching point where the gas fuel supply amount reaches the predetermined amount (6.5 t / h) before the time point P7, it cannot be said that the driving is safe.

  Therefore, the ignition timing of the 1-C gas burner is shifted, and control is performed so that the arrival time of the switching point α is a time point P7 where the supply of the pulverized coal fuel stops, or a few tens of seconds after the time point P7. Thereby, in the boiler unit 10, for example, the main steam temperature that has been in an upward trend is stably maintained at a rated main steam temperature of + 8 ° C. or lower.

  Such control for shifting the ignition timing of the 1-C gas burner may be performed while the boiler unit 10 is in operation. It is also conceivable to perform while the boiler unit 10 is stopped.

  FIG. 4 is a process flowchart showing an example of the boiler fuel switching control method of the present invention. This will be described with reference to FIGS. For example, in this control process, the following steps are controlled by the control device at regular intervals during operation of the boiler unit 10.

  In the boiler unit 10, the temperature of the main steam is monitored using the temperature detector 19 (S301). An upper limit value when the main steam temperature rises and a lower limit value when the main steam temperature falls are set in advance.

  In process step S302, it is determined whether or not the main steam temperature detected by the temperature detector 19 is higher than the set upper limit value. If it is determined that the main steam temperature is higher than the set upper limit value, control is performed to delay the predetermined burner ignition timing (1-C gas burner ignition timing in FIG. 2) by P seconds in processing step S303. The value of P seconds may be determined according to the setting of the upper limit value when the main steam temperature rises.

  In process step S302, when it is not determined that the main steam temperature detected by the temperature detector 19 is higher than the set upper limit value, the process proceeds to process step S304. In processing step S304, it is determined whether or not the main steam temperature detected by the temperature detector 19 is lower than the set lower limit value. When it is determined that the main steam temperature is lower than the set lower limit value, a predetermined burner ignition timing (1-C gas burner ignition timing in FIG. 2) is controlled to be advanced by Q seconds in processing step S305. The value of Q seconds may be determined according to the setting of the lower limit value when the main steam temperature falls.

  If it is not determined in process step S304 that the main steam temperature detected by the temperature detector 19 is lower than the set lower limit value, the current control process is terminated. Thereby, for example, it is determined that the main steam temperature continues to be maintained at the rated main steam temperature + 8 ° C. or lower until the next control process through the current control process.

  According to the boiler fuel switching control method and the boiler device in which the boiler fuel switching control is performed, an increase in the main steam temperature can be suppressed, so that an effect of reducing thermal stress can be obtained. In addition, waste of fuel (fuel (coal + gas) in the first stage burner) is suppressed, and cooling water spray control for suppressing an increase in the furnace outlet temperature is not necessary. Furthermore, an effect of reducing anxiety and burden on the operator for safe driving management can be obtained.

  FIG. 5 is a block diagram illustrating a configuration example of a boiler apparatus according to the modification of FIG. The boiler unit 50 has a configuration in which a liquid fuel supply system 55 and a supply pump 56 are added as compared with the boiler unit 10 of FIG. 1, and the burner unit 52 is also added with a liquid fuel system burner. The liquid fuel is, for example, light oil or heavy oil.

  The first-stage burner unit 521 can also supply LNG (liquefied natural gas), which is a gaseous fuel, other than the pulverized coal or light oil as the main fuel, as compared with the burner units 522, 523, and 524 of the other stages. Part. That is, BOG (boil-off gas) generated in the LNG tank can be consumed as power generation energy. Other configurations are the same as those shown in FIG.

  That is, when the fuel switching control is performed on a part of the main fuel (pulverized coal or light oil) during operation of the boiler unit 50, the control device 13 determines the first-stage burner unit according to the temperature information of the temperature detector 19. Adjustment regarding boiler fuel switching control at 521 is possible.

  In the first stage burner section 521, the influence of the gas fuel (NG) supply is increased in accordance with the decrease in the supply of the main fuel (pulverized coal or light oil). Then, in controlling the gas fuel supply amount to reach a predetermined amount at a switching point aiming at the main fuel stop time point at which the supply of the main fuel (pulverized coal or light oil) disappears, in the first stage burner unit 521 It is possible to control to move the switching point in the vicinity of the main fuel stop time by shifting the ignition timing of a predetermined burner.

  As described above, according to the present invention, when a part of the fuel supply into the furnace of the boiler operating with the main fuel is switched from the main fuel to the second fuel, for example, the gas fuel accompanying the BOG generation of the LNG, an excessive fuel state It is possible to provide a stable boiler fuel switching control method and a boiler device that do not become a problem.

DESCRIPTION OF SYMBOLS 10, 50 Boiler unit 11 Furnace 12, 52 Burner part 13 Control apparatus 14 Valve control system 15 Coal supply system 16 Pulverized coal machine (mill)
17 Fuel blower (PAF)
18 Heat Exchanger 19 Temperature Detector 20 LNG Supply Equipment 21 LNG Tank 22 Boost Pump 23 Vaporizer 24 BOG Compressor 25 Flare Stack 55 Liquid Fuel Supply System 56 Pump

Claims (5)

Each of the plurality of burners capable of supplying the first fuel to a boiler unit using the first fuel as a main fuel includes an n-stage burner portion configured in a predetermined number of stages, and m (< n) The second stage burner can supply a second fuel that is a gaseous fuel other than the first fuel,
In the m-th stage burner part during operation of the boiler unit,
Increasing the influence of the supply of the second fuel to the boiler unit in response to decreasing the supply of the first fuel;
Allowing the supply amount of the second fuel to reach a predetermined amount at a switching point that is aimed near the first fuel stop point at which the supply of the first fuel ceases;
With
Shifting the ignition timing of a predetermined burner in the m-th stage burner portion to move the switching point near the supply stop time;
A boiler fuel switching control method. Regarding control for reducing the supply of the first fuel,
A first step of reducing the first fuel at a constant rate of change until reaching a first flow rate value;
A second stage for maintaining the first flow rate value substantially constant;
A third stage until the supply of the first fuel to all the burners of the m-th stage burner section is terminated;
A boiler fuel switching control method according to claim 1. Regarding the m-th stage burner part, the control of the second fuel is as follows:
A first stage of opening the second fuel when starting to reduce the supply of the first fuel;
A second step of changing the second fuel flow rate to a second flow rate value that is greater than the first flow rate value, including a period in which the flow rate of the second fuel is constantly increased according to the flow rate adjustment;
A third stage for maintaining the second flow rate value substantially constant as the switching point;
With
In the first stage, the first burner that has reached the first pressure is ignited, and in the second stage, after the predetermined burner that has reached the second pressure is ignited, the flow rate of the second fuel is kept constant. The remaining burners are sequentially ignited in the predetermined order on the condition that the predetermined pressure is reached in the increasing period,
The boiler fuel switching control method according to claim 2, wherein the ignition timing of the predetermined burner is selected from a predetermined range time after the ignition of the first burner. A boiler unit including an n-stage burner portion in which each of a plurality of burners capable of supplying a first fuel as a main fuel is configured in a predetermined number of stages;
An m (<n) stage burner portion capable of supplying a second fuel that is a gaseous fuel other than the first fuel among the burner portions;
A first control mechanism for gradually reducing the supply of the first fuel in the m-th stage burner during operation of the boiler unit;
A period in which the second fuel is opened when the control to reduce the first fuel is started in the m-th stage burner during operation of the boiler unit, the flow rate of the second fuel is adjusted, and the flow rate is constantly increased. A second control mechanism that causes the supply amount of the second fuel to reach a predetermined amount at a switching point that is aimed at the vicinity of the first fuel stop time when the supply of the first fuel is eliminated.
A third control mechanism for shifting the ignition timing of a predetermined burner in the m-th stage burner section to move the switching point near the supply stop time;
Boiler device equipped with. The m-th stage burner portion includes a predetermined number of burners that are ignited in a predetermined order from the time when the second fuel is opened.
An initial ignition burner that is ignited when the second fuel is opened and reaches a first pressure;
An ignition timing control burner as the predetermined burner that reaches the second pressure by adjusting the flow rate of the second fuel and can be ignited after a predetermined time after the initial ignition burner ignition;
An ignition follow-up burner group that is sequentially ignited on the condition that a predetermined pressure is reached in a period in which the flow rate of the second fuel is constantly increased;
The boiler apparatus of Claim 4 provided with these.

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