JP2016008803A - Boiler equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide boiler equipment in which a combustion state of a boiler can be reflected on a flow rate adjustment valve with high accuracy even if an air ratio undergoes a change due to variation in mass flow rate and heat quantity of fuel gas.SOLUTION: Boiler equipment 1 comprises: a flow rate control part 95 for controlling a flow rate adjusting valve 56 on the basis of a value of opening corresponding to a flow rate of combustion air detected by an air differential pressure sensor 33; and an oxygen concentration correcting part 94 for correcting the opening value in such a way that the oxygen concentration of exhaust gas detected by an Osensor 81 arranged at the exhausting cylinder 80 may become a prescribed value. Correction by the oxygen concentration correction part 94 is started under a condition that its operation is carried out after starting of combustion of fuel gas at a boiler 2 and the oxygen concentration detected by the Osensor 81 falls within a range of the prescribed concentration.

Description

  The present invention relates to a boiler device. More specifically, the present invention relates to a boiler device that controls a flow rate adjustment valve of a fuel supply line so that fuel gas corresponding to the supply amount of combustion air is supplied.

  2. Description of the Related Art Conventionally, there has been known a boiler apparatus that generates steam by burning water-fuel mixture obtained by mixing fuel gas and combustion air at a predetermined ratio to heat water. In this type of boiler device, the flow rate of the fuel gas is adjusted by a flow rate adjustment valve in accordance with the supply amount of combustion air so that the air ratio, which is the ratio between the theoretical air amount and the air amount supplied to the boiler, is constant. It is adjusted. For example, Japanese Patent Application Laid-Open No. H10-228707 discloses such control that keeps the air ratio constant. Patent Document 1 discloses a fuel gas amount control device for a premixed gas burner that adjusts a fuel gas control valve in accordance with fluctuations in the amount of combustion air supplied to make the air ratio constant.

JP-A-11-108352

  By the way, LNG (Liquid Natural Gas) is widely spread as a fuel gas due to the increase in environmental awareness. One method of supplying LNG is so-called LNG satellite supply in which LNG is transported in a liquid state and vaporized at a supply destination that uses LNG. Although LNG satellite supply can reduce the introduction cost and is used in various fields, the fuel gas tends to be more susceptible to the external environment than the method of transporting the fuel gas through the pipeline. .

  When the flow rate of the fuel gas supplied to the boiler device fluctuates due to the external environment or the like, the air ratio may deviate from a predetermined range. For example, if the mass flow rate fluctuates due to temperature fluctuations or pressure fluctuations, or the amount of heat of the fuel gas changes due to component fluctuations that occur in the process of vaporizing LNG, the amount of air required for combustion (theoretical air amount) Changes, the air ratio fluctuates, which may cause a reduction in combustion efficiency and incomplete combustion. However, since the conventional boiler device controls the flow rate adjustment valve based on the opening set according to the flow rate of the combustion air, the boiler ratio of the boiler whose air ratio has fluctuated due to the influence of the external environment, etc. The combustion state cannot be accurately reflected in the control of the flow rate adjusting valve, and there is room for improvement from the viewpoint of improving combustion efficiency.

  The present invention provides a boiler device capable of accurately reflecting the combustion state of a boiler on a flow rate adjustment valve even when the air ratio varies due to a variation in the mass flow rate of fuel gas or a variation in heat quantity. Objective.

  The present invention includes a boiler, a fuel supply line that supplies fuel gas to the boiler, a flow rate adjustment valve that is disposed in the fuel supply line and that can adjust the flow rate of the fuel gas, and the boiler is mixed with the fuel gas An air supply line for supplying combustion air, an air flow rate detection unit for detecting a flow rate of the combustion air flowing through the air supply line, and an exhaust gas discharge unit for discharging exhaust gas generated by combustion of the fuel gas from the boiler The flow rate adjustment based on the control value corresponding to the flow rate of the combustion air detected by the air flow rate detection unit and the oxygen concentration detection unit that is disposed in the exhaust gas discharge unit and detects the oxygen concentration of the exhaust gas The control value is corrected so that the oxygen concentration of the exhaust gas detected by the flow rate control unit that controls the valve and the oxygen concentration detection unit becomes a predetermined value. And oxygen concentration correcting section relates to a boiler apparatus comprising: a.

  The correction by the oxygen concentration correction unit is started on the condition that the oxygen concentration detected by the oxygen concentration detection unit is within a predetermined concentration range after the start of combustion of the fuel gas in the boiler. Is preferred.

  The control value is preferably an opening value indicating an opening of the flow rate adjusting valve corresponding to the flow rate of the combustion air.

  The boiler device further includes a fuel gas flow rate detection unit that is disposed in the fuel supply line and detects the flow rate of the fuel gas, and the control value is a target flow rate of the fuel gas corresponding to the flow rate of the combustion air. And it is preferable that the said flow control part controls the opening degree of the said flow regulating valve so that the flow volume of the said fuel gas detected by the said fuel gas flow volume detection part may turn into the said target flow volume.

  ADVANTAGE OF THE INVENTION According to this invention, even when fluctuation | variation arises in air ratio by the fluctuation | variation of the mass flow rate of fuel gas, the fluctuation | variation of calorie | heat amount, etc., the boiler apparatus which can reflect the combustion condition of a boiler on a flow regulating valve accurately can be provided. .

It is a figure showing typically one embodiment of the boiler device of the present invention. It is a graph which shows the relationship between the mass flow rate of fuel gas, and the oxygen concentration of waste gas. It is a block diagram which shows the structure of the control part of 1st Embodiment. It is a block diagram which shows the structure of the control part of 2nd Embodiment.

  Hereinafter, preferred embodiments of the boiler device of the present invention will be described with reference to the drawings. The boiler apparatus 1 of 1st Embodiment is a steam boiler which heats water and produces | generates a vapor | steam, and supplies a vapor | steam to load equipment (illustration omitted). The “line” in the present specification is a general term for lines capable of flowing a fluid such as a flow path, a path, and a pipeline.

  As shown in FIG. 1, a boiler apparatus 1 includes a boiler 2, a fuel supply unit 50 that supplies fuel gas to the boiler 2, a water supply path (not shown) that supplies water to the boiler 2, fuel gas and combustion And a control device 70 for controlling the supply amount of air and the like.

  The boiler 2 includes a can body 10, a blower 20 that sends combustion air to the can body 10, an air supply duct 30 that connects the can body 10 and the blower 20, and serves as an air supply line through which combustion air flows. A damper 31 disposed in the air duct 30, a punching metal 32 as a combustion air decompression member, an air differential pressure sensor 33 as an air flow rate detector, and a combustion gas (exhaust gas) discharged from the can body 10 circulates. And an exhaust pipe 80 as an exhaust gas discharge section.

  The can 10 includes a boiler housing 11, a plurality of water pipes 12, a lower header 13, an upper header 14, and a burner 15.

  The boiler housing | casing 11 comprises the external shape of the can 10, and is formed in the rectangular parallelepiped shape of planar view. An air supply port 16 is formed in the first side surface 11a located on one end side in the longitudinal direction of the boiler casing 11, and a second side surface 11b located on the other end side in the longitudinal direction of the boiler casing 11 is An exhaust port 17 is formed.

  The plurality of water pipes 12 are disposed so as to extend in the vertical direction inside the boiler housing 11 and are disposed at predetermined intervals in the longitudinal direction and the width direction of the boiler housing 11.

  The lower header 13 is disposed at the lower part of the boiler casing 11. The lower header 13 is connected to the lower ends of the plurality of water pipes 12. The upper header 14 is disposed on the upper portion of the boiler casing 11. The upper header 14 is connected to the upper ends of the plurality of water pipes 12.

  The burner 15 is disposed in the air supply port 16. The mixture of fuel gas and combustion air is burned by the burner 15, and the water in the water pipe 12 is heated to generate steam.

  The blower 20 includes a blower body 21 having a fan and a motor that rotates the fan, and an inverter 22 that increases or decreases the number of rotations of the fan (motor). The blower 20 feeds combustion air into the can body 10 when the fan rotates at a predetermined rotation speed in accordance with the frequency input to the inverter 22.

  In the present embodiment, the flow rate of the combustion air is set according to a required load required from a load device (not shown). The blower 20 is controlled by the control device 70 via the inverter 22 so that the flow rate of the fuel air is set.

  The air supply duct 30 is an air supply line that supplies combustion air to be mixed with fuel gas into the boiler 2. The air supply duct 30 has an upstream end connected to the blower 20 and a downstream end connected to the air supply port 16. The air supply duct 30 supplies the combustion air sent from the blower 20 to the can body 10.

  The damper 31 is in a closed state in which the combustion air flow path inside the air supply duct 30 is closed and rotated 90 degrees from this closed state to open the combustion air flow path in the air supply duct 30. It is arranged to be rotatable between states.

  The punching metal 32 is a metal plate in which a plurality of through holes are formed, and is a combustion air pressure-reducing member that depressurizes the combustion air that circulates. The punching metal 32 is disposed on the downstream side of the damper 31 inside the air supply duct 30. The punching metal 32 decompresses the combustion air flowing through the damper 31 to the air supply duct 30.

  The air differential pressure sensor 33 is an air flow rate detection unit for detecting the flow rate of combustion air. The air differential pressure sensor 33 detects a differential pressure between the upstream pressure and the downstream pressure of the punching metal 32. The flow rate of the fuel air is calculated based on this differential pressure information. Further, the air differential pressure sensor 33 is electrically connected to the control device 70, and the control device 70 acquires air differential pressure information detected by the air differential pressure sensor 33.

  The exhaust cylinder 80 is connected to the can body 10 (exhaust port 17 formed in the boiler casing 11) on the base end side, and is formed in a cylindrical shape. Combustion gas (exhaust gas) generated in the can body 10 is discharged to the outside of the can body 10 through the exhaust cylinder 80.

An O ₂ sensor 81 as an oxygen concentration detector is disposed inside the exhaust pipe 80 of the present embodiment. The oxygen concentration of the exhaust gas is acquired by the O ₂ sensor 81. The O ₂ sensor 81 is electrically connected to the control device 70, and the control device 70 acquires the oxygen concentration of the exhaust gas based on the measurement value of the O ₂ sensor 81.

  Next, the fuel supply unit 50 that supplies fuel to the boiler 2 will be described. The fuel supply unit 50 includes a fuel supply line 51, a fuel gas flow meter 52, an on-off valve 54, a governor 55, a flow rate adjustment valve 56, a fuel gas temperature sensor 57, a fuel gas pressure sensor 58, and an orifice 59. And a fuel gas differential pressure sensor 60 and a nozzle 61.

  The fuel supply line 51 has an upstream side connected to a fuel supply source (not shown) and a downstream side connected to the air supply duct 30. The downstream end of the fuel supply line 51 is connected to the downstream side of the supply duct 30 from the position where the damper 31 is disposed. In the present embodiment, the fuel gas flowing through the fuel supply line 51 is LNG. LNG vaporized from the LNG storage facility supplied by the LNG satellite is supplied to the fuel supply line 51.

  The fuel gas flow meter 52 measures the flow rate of the fuel gas flowing through the fuel supply line 51. The fuel gas flow meter 52 of the present embodiment is disposed on the most upstream side of the fuel supply line 51. The fuel gas flow meter 52 is electrically connected to the control device 70. The control device 70 acquires the flow rate of the fuel gas based on the measurement value of the fuel gas flow meter 52.

  The on-off valve 54 opens or closes the fuel supply line 51 to supply and stop the fuel gas. The on-off valve 54 of the present embodiment is disposed on the fuel supply line 51 downstream of the fuel gas flow meter 52.

  The governor 55 is pressure adjusting means for suppressing a rapid pressure fluctuation such as when the pressure of the fuel gas flowing through the fuel supply line 51 increases momentarily. The governor 55 of the present embodiment is disposed on the downstream side of the on-off valve 54 in the fuel supply line 51.

  The flow rate adjustment valve 56 adjusts the flow rate of the fuel gas flowing through the fuel supply line 51. The flow rate adjustment valve 56 is configured to be able to adjust the opening degree. The flow rate adjustment valve 56 of the present embodiment is disposed on the downstream side of the governor 55 in the fuel supply line 51. The flow rate adjustment valve 56 is electrically connected to the control device 70, and the control device 70 can adjust the opening degree of the flow rate adjustment valve 56.

  The fuel gas temperature sensor 57 measures the temperature of the fuel gas flowing through the fuel supply line 51 on the downstream side of the flow rate adjustment valve 56. The fuel gas temperature sensor 57 of the present embodiment is disposed downstream of the flow rate adjustment valve 56 in the fuel supply line 51. The fuel gas temperature sensor 57 is electrically connected to the control device 70, and the control device 70 acquires temperature information of the fuel gas temperature sensor 57.

  The fuel gas pressure sensor 58 measures the pressure of the fuel gas flowing through the fuel supply line 51 on the downstream side of the flow rate adjustment valve 56. The fuel gas pressure sensor 58 of the present embodiment is disposed downstream of the fuel gas temperature sensor 57 in the fuel supply line 51. The fuel gas pressure sensor 58 is electrically connected to the control device 70, and the control device 70 acquires pressure information of the fuel gas pressure sensor 58.

  The orifice 59 is a fuel gas decompression member that decompresses the fuel gas flowing through the fuel supply line 51. The orifice 59 of the present embodiment is disposed on the downstream side of the fuel gas pressure sensor 58 in the fuel supply line 51.

  The fuel gas differential pressure sensor 60 is a fuel gas flow rate detector for detecting the flow rate of the fuel gas. The pressure difference between the upstream side and the downstream side of the orifice 59 is detected. The flow rate of the fuel gas on the downstream side of the flow rate adjusting valve 56 is calculated based on the fuel gas differential pressure information. The fuel gas differential pressure sensor 60 is electrically connected to the control device 70, and the control device 70 acquires fuel gas differential pressure information.

  The nozzle 61 is disposed at the downstream end of the fuel supply line 51 and ejects fuel gas to the air supply duct 30. The fuel gas ejected from the nozzle 61 is mixed with the combustion air sent by the blower 20, and the mixed gas is burned by the burner 15.

  As described above, the fuel supply unit 50 can supply the fuel gas to the boiler 2 (can 10) through the fuel supply line 51 at an appropriate flow rate.

  The control device 70 will be described. The control device 70 controls the flow rate adjustment valve 56 and the blower 20 based on signals from each electrically connected sensor. The control device 70 includes a control unit 71 that performs various controls for adjusting the flow rate of combustion air and the flow rate of fuel gas, and a storage unit 72 that stores various types of information.

  The control device 70 of the first embodiment controls the flow rate adjustment valve 56 with reference to the oxygen concentration of the exhaust gas in order to keep the air ratio constant. First, the relationship between the change in the mass flow rate of the fuel gas and the combustion rate will be described with reference to FIG. FIG. 2 is a graph showing the relationship between the mass flow rate of the fuel gas and the oxygen concentration of the exhaust gas. In FIG. 2, trial calculation conditions are set, and a change in mass flow rate due to a change in fuel gas temperature and a ratio of oxygen concentration of exhaust gas indicating a combustion rate are calculated. The fuel gas pressure is assumed to be constant.

As shown in FIG. 2, when a temperature change occurs in the fuel gas, the volume of the fuel gas changes and the mass flow rate changes. When the temperature of the fuel gas increases, the volume of the fuel gas increases, so the mass flow rate of the fuel gas decreases. When the temperature of the fuel gas decreases, the volume decreases, so the mass flow rate of the fuel gas increases. When such a change in mass flow rate occurs, even if the volume flow rate is constant, the theoretical amount of combustion air necessary for combustion of the fuel gas changes, and the air ratio changes. As shown in FIG. 2, the air ratio increases and the O ₂ concentration in the exhaust gas increases as the mass flow rate of the fuel gas decreases, while the air ratio decreases as the mass flow rate of the fuel gas increases. The O ₂ concentration in the exhaust gas becomes low. The air ratio is a value that is set in the boiler device 1 in order to appropriately perform combustion. If the air ratio cannot be controlled to a constant value, heat loss due to excess air occurs and combustion efficiency decreases. There is a risk of energy loss due to incomplete combustion.

  Therefore, the control device 70 of the present embodiment is configured to reflect the oxygen concentration of the exhaust gas detected by the exhaust cylinder 80 in the control of the flow rate adjustment valve 56 in order to keep the air ratio set in the boiler device 1 constant. It was. Next, the detailed structure of the control part 71 with which the boiler apparatus 1 of 1st Embodiment is provided is demonstrated. FIG. 3 is a block diagram illustrating a configuration of the control unit 71. As shown in FIG. 3, the control unit 71 of the first embodiment includes an opening degree setting unit 91, an oxygen concentration correction unit 94, and a flow rate control unit 95.

  The opening setting unit 91 sets an opening value indicating the opening of the flow rate adjustment valve 56. The opening value is a control value of the flow rate adjusting valve 56 for determining the flow rate of the fuel gas with respect to the flow rate of the combustion air under a predetermined condition. Here, the predetermined conditions are various conditions set in advance such as a reference heat amount and an air ratio based on the composition of the fuel gas, and the opening value is set assuming that the fuel gas is in the predetermined conditions. The storage unit 72 stores a functional expression or a data table for setting an opening value corresponding to the flow rate of combustion air under a predetermined condition.

The oxygen concentration correction unit 94 corrects the opening value according to the oxygen concentration of the exhaust gas in order to make the air ratio (combustion rate) of the boiler 2 constant. A target oxygen concentration is set in the oxygen concentration correction unit 94 based on a preset air ratio. The oxygen concentration correction unit 94 corrects the opening value based on the target oxygen concentration and the oxygen concentration acquired by the O ₂ sensor 81. The storage unit 72 stores a functional formula or a data table for correcting the opening value based on the concentration difference between the target oxygen concentration and the oxygen concentration acquired by the O ₂ sensor 81. ing.

The oxygen concentration correction unit 94 reads information necessary for calculation from the storage unit 72 when performing the correction process, and corrects the opening value. For example, when the oxygen concentration of the exhaust gas is lower than the target oxygen concentration, the opening degree value is corrected so that the flow rate of the fuel gas is reduced. Similarly, when the oxygen concentration of the exhaust gas is higher than the target oxygen concentration, the opening value is corrected so that the flow rate of the fuel gas is increased. As described above, the flow rate adjustment valve 56 is feedback-controlled based on the measured value of the O ₂ sensor 81 so that the oxygen concentration of the exhaust gas becomes a predetermined value (target oxygen concentration), so that the air ratio is kept constant. The The target oxygen concentration may be set as a concentration range having a width or may be set as one target value.

The start condition is set so that the correction of the opening value by the oxygen concentration correction unit 94 is started after the combustion by the burner 15 is stabilized. In this embodiment, the correction start condition by the oxygen concentration correction unit 94 is that the oxygen concentration acquired by the O ₂ sensor 81 falls within a predetermined concentration range.

  The flow control unit 95 will be described. The flow rate control unit 95 controls the flow rate adjustment valve 56 based on the opening degree value. After the correction process by the oxygen concentration correction unit 94 is started, the opening of the flow rate adjustment valve 56 is adjusted based on the opening value corrected by the oxygen concentration correction unit 94.

  Next, a series of flow of control of the flow rate adjustment valve 56 in the first embodiment will be described. When the control of the flow rate adjustment valve 56 is started, the opening degree setting unit 91 acquires the flow rate of the combustion air calculated based on the detection signal of the air differential pressure sensor 33. The opening setting unit 91 sets an opening value corresponding to the obtained flow rate of combustion air from the storage unit 72. At the beginning of the control of the flow rate adjusting valve 56, the flow rate adjusting valve 56 is controlled based on the opening value.

The oxygen concentration correction unit 94 monitors the measurement value of the O ₂ sensor 81 and determines whether or not the correction start condition is satisfied. When it is determined that the oxygen concentration of the exhaust gas has entered a predetermined concentration range, the opening degree correction process is started. In the correction process, the opening value set by the opening setting unit 91 is corrected based on the concentration difference between the target oxygen concentration set in advance and the oxygen concentration acquired by the O ₂ sensor 81. The flow control unit 95 controls the flow control valve 56 based on the corrected opening value. Then, the oxygen concentration correction unit 94 continues to monitor the fluctuation of the oxygen concentration acquired by the O ₂ sensor 81 and corrects the opening value as needed according to the fluctuation of the oxygen concentration. Thereby, the actual combustion state of the boiler 2 is reflected in the control of the flow rate control unit 95. Thus, after the start of the correction process, the opening degree of the flow rate adjustment valve 56 is controlled based on the oxygen concentration. The correction process by the oxygen concentration correction unit 94 may be performed constantly, or may be performed based on the measurement value of the O ₂ sensor 81 extracted at a predetermined interval and detected at that timing.

  The fuel gas is sent to the air supply duct 30 through the fuel supply line 51 in a state adjusted according to the combustion state of the boiler 2. The fuel gas supplied into the air supply duct 30 via the nozzle 61 is mixed with the combustion air sent into the air supply duct 30 by the blower 20. A mixed gas of fuel gas and combustion air is ejected from the burner 15 into the can 10 and burned. In the present embodiment, the flow rate of the fuel gas supplied to the boiler 2 is appropriately adjusted based on the combustion rate of the boiler 2 (oxygen concentration of the exhaust gas), thereby realizing stable and efficient constant control of the air ratio. . Accordingly, the combustion rate can be kept constant even when mass fluctuations due to temperature fluctuations and pressure fluctuations, such as those occurring upstream of the fuel supply unit 50, and heat fluctuations due to component fluctuations, etc., can be maintained. Even when it is easily affected by the environment, the combustion control of the boiler 2 can be stably performed.

  And the water supplied with the combustion of the mixed gas by the burner 15 heats the water supplied from the lower header 13 to the inside of the plurality of water pipes 12, and generates steam. The steam generated in the plurality of water pipes 12 is collected in the upper header 14 and then led out to the outside through a steam lead pipe (not shown) and supplied to a load device (not shown). Further, the combustion gas generated by the combustion of the mixed gas is discharged from the exhaust cylinder 80 to the outside. When a variation in the combustion air flow rate is newly detected by the air differential pressure sensor 33, the opening degree setting unit 91 newly sets an opening degree value corresponding to the combustion air flow rate, and the above-described processing. The opening degree of the flow rate adjusting valve 56 is determined by performing the same correction process as described above and the flow rate control unit 95 reflecting the actual combustion rate (oxygen concentration).

  According to the boiler device 1 of 1st Embodiment demonstrated above, there exist the following effects.

The boiler apparatus 1 of the first embodiment includes a flow rate control unit 95 that controls the flow rate adjustment valve 56 based on an opening value (control value) corresponding to the flow rate of combustion air detected by the air differential pressure sensor 33; An oxygen concentration correction unit 94 that corrects the opening value so that the oxygen concentration of the exhaust gas detected by the O ₂ sensor 81 disposed in the exhaust cylinder 80 becomes a predetermined value.

  As a result, the opening degree of the flow rate adjustment valve 56 is controlled based on the oxygen concentration of the exhaust gas, so that the fuel gas is supplied to the boiler 2 at an appropriate flow rate according to the actual combustion state in the boiler 2. Can do. Therefore, it is effective for the situation in which the combustion ratio of the boiler 2 is lowered due to the influence of the external environment such as mass fluctuations due to temperature fluctuations and pressure fluctuations and the influence of the external environment such as fluctuations in heat quantity based on component fluctuations. Can be prevented.

The correction by the oxygen concentration correction unit 94 is started after the start of combustion of the fuel gas in the boiler 2 and on the condition that the oxygen concentration detected by the O ₂ sensor 81 is in a predetermined concentration range.

  Thereby, after the combustion of the boiler 2 is stabilized, the correction by the oxygen concentration correction unit 94 can be started, so that the combustion control of the boiler 2 can be made more stable.

  Moreover, the control value used for control of the flow control valve 56 in the boiler apparatus 1 of this embodiment is an opening degree value which shows the opening degree of the flow control valve 56 corresponding to the flow volume of combustion air.

  Thereby, by correcting the opening degree value set in advance, the combustion state of the boiler 2 can be accurately reflected in the control of the flow rate adjusting valve 56 without performing complicated processing.

  Next, the boiler apparatus of 2nd Embodiment is demonstrated. It is a block diagram which shows the structure of the control part 271 of 2nd Embodiment. In addition, about the structure similar to 1st Embodiment, the same code | symbol may be attached | subjected and the description may be abbreviate | omitted.

  The boiler apparatus of 2nd Embodiment differs in the method of controlling the flow regulating valve 56 from the structure of the boiler apparatus 1 of 1st Embodiment. The control of the flow rate adjustment valve 56 by the control unit 271 of the second embodiment will be described. As shown in FIG. 4, the control unit 271 includes a target flow rate setting unit 291, an oxygen concentration correction unit 94, and a flow rate control unit 95.

  The target flow rate setting unit 291 sets a target flow rate corresponding to the flow rate of combustion air. The target flow rate is a control value of the flow rate adjustment valve 56 that indicates the flow rate of the fuel gas relative to the flow rate of the combustion air under a predetermined condition. The predetermined conditions here are various conditions set in advance such as a reference heat amount and an air ratio based on the composition of the fuel gas, and the target flow rate is set assuming that the fuel gas is in the predetermined conditions. The storage unit 72 stores a functional expression or a data table for setting a target flow rate corresponding to the flow rate of combustion air under a predetermined condition. The target flow rate may be set as a predetermined flow rate range, or may be set as a predetermined flow rate value.

The oxygen concentration correction unit 94 of the second embodiment corrects the target flow rate according to the oxygen concentration of the exhaust gas in order to make the air ratio (combustion rate) of the boiler 2 constant. The oxygen concentration correction unit 94 corrects the target flow rate based on the target oxygen concentration set in advance based on the air ratio and the oxygen concentration acquired by the O ₂ sensor 81. The storage unit 72 stores a functional formula or a data table for correcting the target flow rate based on the concentration difference between the target oxygen concentration and the oxygen concentration acquired by the O ₂ sensor 81. When the oxygen concentration of the exhaust gas is lower than the target oxygen concentration, the oxygen concentration correction unit 94 corrects the target flow rate so that the flow rate of the fuel gas becomes small. Similarly, when the oxygen concentration of the exhaust gas is higher than the target oxygen concentration, the target flow rate is corrected so that the flow rate of the fuel gas is increased.

  The flow rate control unit 95 controls the opening degree of the flow rate adjustment valve 56 based on the flow rate of the fuel gas detected by the fuel gas differential pressure sensor 60 and the target flow rate corrected by the oxygen concentration correction unit 94. For example, when the flow rate detected by the fuel gas differential pressure sensor 60 is larger than the target flow rate, the opening degree of the flow rate adjustment valve 56 is controlled so that the flow rate of the fuel gas becomes smaller, and the flow rate becomes smaller than the target flow rate. When the flow rate is small, the opening degree of the flow rate adjustment valve 56 is controlled so that the flow rate of the fuel gas is increased. In this manner, the flow rate control unit 95 can stabilize the flow rate of the fuel gas supplied to the boiler 2 at the target flow rate by performing feedback control based on the flow rate on the downstream side of the flow rate adjustment valve 56. It has become. Since the target flow rate is corrected so as to reflect the combustion state by the oxygen concentration correction unit 94, the actual combustion state is accurately reflected even in this feedback control.

  The boiler device 201 according to the second embodiment described above has the following effects.

The boiler device 201 of the second embodiment is further provided with a fuel gas differential pressure sensor 60 that is disposed in the fuel supply line 51 and detects the flow rate of the fuel gas, and the flow rate control unit 95 is detected by the fuel gas differential pressure sensor 60. The degree of opening of the flow rate adjustment valve 56 is controlled so that the flow rate of the fuel gas becomes the target flow rate (control value) stored in association with the flow rate of the combustion air. The target flow rate is corrected by the oxygen concentration correction unit 94 so that the oxygen concentration of the exhaust gas detected by the O ₂ sensor 81 disposed in the exhaust pipe 80 becomes a predetermined value.

  As a result, feedback control is performed based on the flow rate of the fuel gas detected on the downstream side of the flow rate adjustment valve 56, so that the actual combustion state can be accurately reflected in the supply amount of the fuel gas, and the combustion control can be performed. It can be performed even more efficiently.

  As mentioned above, although each preferred embodiment of the boiler apparatus of the present invention was described, the present invention is not limited to the above-mentioned embodiment, and can be changed suitably.

  In the above embodiment, the start condition for starting the correction by the oxygen concentration correction unit 94 is that the oxygen concentration of the exhaust gas falls within a predetermined concentration range, but the start condition of the correction process can be changed as appropriate. For example, after the oxygen concentration reaches a predetermined concentration range, the elapsed time is counted by a timer or the like, and if the oxygen concentration is within the concentration range even after the predetermined time has elapsed, correction by the oxygen concentration correction unit 94 is started. You can also set a start condition. The start condition can also be set so that the correction by the oxygen concentration correction unit 94 is started after a predetermined time has elapsed after the ignition of the burner 15 is started. Further, the correction by the oxygen concentration correction unit 94 may be started at the same time when the control of the opening degree of the flow rate adjusting valve 56 is started. Alternatively, a temperature sensor that measures the temperature of the exhaust gas may be disposed in the exhaust cylinder 80, and the start condition may be that the measured value of the temperature sensor falls within a predetermined temperature range. Thus, the start conditions for starting correction by the oxygen concentration correction unit 94 can be changed as appropriate according to the circumstances.

  In the above embodiment, the opening degree or the target flow rate is stored in the storage unit 72 with the reference heat amount and the air ratio as predetermined conditions, but the configuration can be changed as appropriate. For example, the reference heat amount can be set based on a value detected further upstream than the fuel supply unit 50, and the opening degree or the target flow rate can be set based on the set condition. Moreover, it can also be set as the structure which changes the predetermined condition preset according to the use condition or environment change of the boiler apparatus 1 at an appropriate timing.

  In the above embodiment, a configuration in which the fuel gas is supplied by LNG satellite supply is adopted, but the fuel gas and the fuel gas supply source can be changed as appropriate. For example, the present invention can be applied to a configuration in which fuel gas is directly supplied from a fuel supplier through a pipeline.

1 Boiler device 2 Boiler 30 Air supply duct (Air supply line)
33 Air differential pressure sensor (Air flow rate detector)
51 Fuel Supply Line 56 Flow Control Valve 60 Fuel Gas Differential Pressure Sensor (Fuel Gas Flow Detection Unit)
80 Exhaust pipe (exhaust gas discharge part)
81 O ₂ sensor (oxygen concentration detector)
94 Oxygen concentration correction unit 95 Flow rate control unit 291 Target flow rate setting unit

Claims (4)

With a boiler,
A fuel supply line for supplying fuel gas to the boiler;
A flow rate adjusting valve disposed in the fuel supply line and capable of adjusting a flow rate of the fuel gas;
An air supply line for supplying combustion air to be mixed with the fuel gas in the boiler;
An air flow rate detector for detecting the flow rate of the combustion air flowing through the air supply line;
An exhaust gas discharge part for discharging exhaust gas generated by the combustion of the fuel gas from the boiler;
An oxygen concentration detector disposed in the exhaust gas discharge unit for detecting the oxygen concentration of the exhaust gas;
A flow rate control unit that controls the flow rate adjustment valve based on a control value corresponding to the flow rate of the combustion air detected by the air flow rate detection unit;
An oxygen concentration correction unit that corrects the control value so that the oxygen concentration of the exhaust gas detected by the oxygen concentration detection unit becomes a predetermined value;
A boiler device comprising: Correction by the oxygen concentration correction unit is
The boiler apparatus according to claim 1, wherein the boiler apparatus is started on the condition that the oxygen concentration detected by the oxygen concentration detector is in a predetermined concentration range after the start of combustion of the fuel gas in the boiler.   The boiler apparatus according to claim 1 or 2, wherein the control value is an opening value indicating an opening degree of the flow rate adjusting valve corresponding to a flow rate of the combustion air. A fuel gas flow rate detection unit that is disposed in the fuel supply line and detects the flow rate of the fuel gas;
The control value is a target flow rate of the fuel gas corresponding to the flow rate of the combustion air,
The boiler apparatus according to claim 1 or 2, wherein the flow rate control unit controls an opening degree of the flow rate adjustment valve so that a flow rate of the fuel gas detected by the fuel gas flow rate detection unit becomes the target flow rate.

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