Boiler system, power generation equipment and operation method of boiler system

Abstract

The purpose of the present invention is to cool and protect burner equipment by supplying a sufficient air flow to an unused burner in a high-load zone, and to set an appropriate air flow in accordance with a decrease in the thermal load of a furnace in a low-load zone, thereby being in an appropriate operating state in all load zones. A boiler system (2) is provided with: a boiler (10) having a plurality of burners (21); an air supply unit for supplying air to the burner (21); a cold air damper (30d) that adjusts the amount of air supplied to the combustor (21) by the air supply unit; and a control unit that controls the cold air damper (30d) so as to supply cooling air in an amount corresponding to the load of the boiler (10) when the cooling air is supplied by the air supply unit to the burner (21) in which no flame is formed.

Description

Technical Field

[0001] This invention relates to a boiler system, a power generation device, and a method for operating the boiler system. Background Technology

[0002] Large boilers, such as those used for power generation, have a hollow furnace arranged vertically, with multiple burners arranged circumferentially within the furnace wall. Furthermore, a flue is connected vertically above the furnace, and a heat exchanger for generating steam is installed within this flue. The burners generate flames by injecting a mixture of fuel and air (an oxidizing gas) into the furnace, producing combustion gases that flow into the flue. A heat exchanger is installed in the area where the combustion gases flow, heating water or steam flowing within the heat transfer tubes that constitute the heat exchanger to generate superheated steam.

[0003] This type of boiler is equipped with multiple burners (e.g., Patent Document 1). Furthermore, the number of burners that generate a flame varies depending on the load. In this case, burners that do not generate a flame may become short-lived or damaged due to radiant heat from the furnace. In particular, burners equipped with flame-insulating mechanisms facing the interior of the furnace are prone to metal temperature rise due to radiant heat received by the flame-insulating mechanism surface, which may also lead to short lifespan or easy damage. Therefore, by supplying cooling air to the burners that do not generate a flame to cool them, the short lifespan or damage of the burners is suppressed.

[0004] Previous technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2023-76868 Summary of the Invention

[0007] The technical problem to be solved by the invention

[0008] The cooling air supplied to burners without flames differs from the combustion air supplied to burners with flames, making it difficult to directly contribute to combustion in the boiler. Therefore, depending on the boiler load, increasing the ratio of cooling air to the total amount of air supplied to the boiler (total air volume) causes the air ratio near the flame to deviate from the specified range. This leads to an increase in the concentration of nitrogen oxides (NOx) in the combustion exhaust and a rise in the exhaust temperature at the air preheater outlet due to the increased amount of air bypassing the air preheater, which may affect the boiler's performance and usability.

[0009] The present invention was made in view of this situation, and its object is to provide a boiler system and power generation equipment, as well as a method of operating the boiler system, that provides sufficient airflow to cool and protect the burner equipment under high load conditions, and sets an appropriate airflow according to the reduction of the furnace heat load under low load conditions, thereby being in an appropriate operating state under all load conditions.

[0010] means for solving technical problems

[0011] To address the aforementioned issues, the boiler system, power generation equipment, and boiler system operation method of the present invention employ the following means.

[0012] One aspect of the present invention relates to a boiler system comprising: a boiler having a plurality of burners; an air supply unit for supplying air to the burners; an adjustment unit for adjusting the amount of air supplied to the burners via the air supply unit; and a control unit for controlling the adjustment unit to supply an amount of cooling air corresponding to the load of the boiler when cooling air is supplied to the burners (which are not forming a flame) via the air supply unit.

[0013] In one aspect of the present invention, a method for operating a boiler system includes: a boiler having a plurality of burners; an air supply unit for supplying air to the burners; and a regulating unit for regulating the amount of air supplied to the burners through the air supply unit. The method for operating the boiler system includes: a control step in which, when supplying cooling air to the burners (which are not forming flames) through the air supply unit, the regulating unit is controlled to supply an amount of cooling air corresponding to the load of the boiler.

[0014] Invention Effects

[0015] According to the present invention, under high load conditions, sufficient airflow is supplied to unused burners for cooling to protect the burner equipment, and under low load conditions, appropriate airflow is set according to the reduction of the furnace heat load, thereby enabling the formation of appropriate combustion state flames under each load, thus achieving overall boiler optimization. Attached Figure Description

[0016] Figure 1 This is a schematic structural diagram of the boiler system involved in the embodiments of the present invention.

[0017] Figure 2 This is a schematic structural diagram of the boiler system involved in the embodiments of the present invention.

[0018] Figure 3 This is a block diagram illustrating the control unit involved in an embodiment of the present invention.

[0019] Figure 4 It is a graph showing the relationship between the boiler load and the opening of the cold air damper in the boiler system according to the embodiments of the present invention.

[0020] Figure 5 It is a graph showing the relationship between boiler load and cold air damper opening in a boiler system according to a variation of the embodiments of the present invention for each solid fuel. Detailed Implementation

[0021] Hereinafter, with reference to the accompanying drawings, one embodiment of the boiler system, power generation equipment, and boiler system operation method according to the present invention will be described. Furthermore, the present invention is not limited to this embodiment, and when multiple embodiments are available, combinations of these embodiments are also included. In the following description, "upper" or "above" refers to the upper side in the vertical direction, and "lower" or "below" refers to the lower side in the vertical direction. The vertical direction is not strictly vertical but includes tolerances.

[0022] The power generation device 1 according to this embodiment includes a boiler system 2 that generates steam, a steam turbine (not shown) driven by the steam generated in the boiler system 2, and a power generation unit (not shown) that generates electricity by the driving force of the steam turbine.

[0023] Figure 1 This is a schematic structural diagram showing the boiler system 2, which uses solid fuel as the main fuel according to this embodiment. The boiler system 2 includes a boiler 10 and a mill 31, etc. Detailed information about the boiler system 2 will be described later.

[0024] The boiler 10 of this embodiment is a boiler capable of burning finely powdered fuel, which is made by pulverizing solid fuel, through a burner, and exchanging the heat generated by the combustion with feedwater or steam to generate superheated steam. Biomass fuel or coal, etc., are used as the solid fuel.

[0025] The boiler 10 includes a furnace 11, a combustion device, and a combustion gas passage 12. The furnace 11 is a hollow, square tube arranged vertically. The furnace wall 101, which forms the inner wall of the furnace 11, is composed of multiple heat transfer tubes and fins connecting the heat transfer tubes. It recovers heat generated by burning pulverized fuel by exchanging heat with water or steam flowing inside the heat transfer tubes and suppresses the temperature rise of the furnace wall 101.

[0026] The combustion device is located in the lower region of the furnace 11. In this embodiment, the combustion device has multiple burners 21A, 21B, 21C, 21D, 21E, and 21F (hereinafter, sometimes collectively referred to as "burners 21") mounted on the furnace wall 101. The burners 21 are arranged in multiple stages along the vertical direction, with burners (for example, four at each corner of the quadrilateral furnace 11) arranged at equal intervals along the circumference of the furnace 11. Furthermore, in... Figure 1 For ease of illustration, only two burners from one group are shown, and each group is labeled with the symbols 21A, 21B, 21C, 21D, 21E, and 21F. The shape of the furnace 11, the number of burner stages, the number of burners in one stage, and the arrangement of the burners are not limited to this embodiment.

[0027] Burners 21A, 21B, 21C, 21D, 21E, and 21F are connected to multiple mills (pulverizers) 31A, 31B, 31C, 30D, 31E, and 31F (hereinafter sometimes collectively referred to as "pulverized fuel supply pipes 22") via multiple micro-powder fuel supply pipes 22A, 22B, 22C, 22D, 22E, and 22F, respectively. The mill 31 is, for example, a vertical roller mill, configured to have a rotatably driven crushing table (not shown) internally, and multiple crushing rollers (not shown) supported above the crushing table so as to rotate in conjunction with the rotation of the crushing table. The solid fuel co-crushed by the crushing rollers and the crushing table is conveyed to a classifier (not shown) provided in the mill 31 via primary air (conveying gas, oxidizing gas) supplied to the mill 31. In the classifier, the fuel is classified into fine fuel with a particle size smaller than that suitable for combustion in the burner 21 and coarse fuel with a particle size larger than that. The fine fuel is supplied to the burner 21 along with primary air via the fine fuel supply pipe 22 after passing through the classifier. The coarse fuel that has not passed through the classifier falls onto the crushing table inside the mill 31 due to its own weight and is crushed again. Furthermore, the burner 21 has a flame-keeping mechanism (not shown) at its front end that faces the inside of the furnace 11.

[0028] An air box (air conditioner) 23 is installed on the outside of the furnace 11 at the installation position of the burner 21. One end of an air duct (air conduit) 24 is connected to the air box 23. A forced draft fan (FDF) 32 is connected to the other end of the air duct 24. The air supplied from the forced draft fan 32 is heated by an air preheater 42 installed in the air duct 24 (details will be described later), and is supplied to the burner 21 as secondary air (combustion air, oxidizing gas) via the air box 23, and then introduced into the interior of the furnace 11.

[0029] The combustion gas passage 12 is vertically connected to the upper part of the furnace 11. Within the combustion gas passage 12, superheaters 102A, 102B, and 102C (hereinafter, sometimes collectively referred to as "superheater 102"), reheaters 103A and 103B (hereinafter, sometimes collectively referred to as "reheater 103"), and an economizer 104 are provided as heat exchangers for recovering heat from the combustion gases. Heat exchange occurs between the combustion gases generated in the furnace 11 and the feedwater or steam flowing inside each heat exchanger. Furthermore, the arrangement and shape of each heat exchanger are not limited to... Figure 1 The way it is recorded.

[0030] Downstream of the combustion gas passage 12 is a flue 13 that discharges combustion gases that have recovered heat through a heat exchanger. In the flue 13, an air preheater (air heater) 42 is installed between the flue 13 and the air duct 24 to exchange heat between the air flowing in the air duct 24 and the combustion gases flowing in the flue 13. By heating the primary air supplied to the mill 31 or the secondary air supplied to the burner 21, further heat recovery is achieved from the combustion gases after heat exchange with water or steam.

[0031] Furthermore, a denitrification device 43 can be installed in the flue 13, located upstream of the air preheater 42. The denitrification device 43 supplies a reducing agent that reduces nitrogen oxides such as ammonia and urea water to the combustion gas flowing in the flue 13. The denitrification catalyst installed in the denitrification device 43 promotes the reaction between the nitrogen oxides (NOx) in the combustion gas and the reducing agent, thereby removing and reducing the nitrogen oxides in the combustion gas.

[0032] A gas duct 41 is connected to the flue 13 downstream of the air preheater 42. The gas duct 41 is equipped with environmental devices such as an electrostatic precipitator 44 for removing dust and other pollutants from the combustion gases, or a desulfurization device 46 for removing sulfur oxides. An induced draft fan 45 is also installed to guide exhaust gas to these environmental devices. The downstream end of the gas duct 41 is connected to the chimney 47, and the combustion gases treated by the environmental devices are discharged outside the system as exhaust gas.

[0033] In boiler 10, if multiple mills 31 are driven, the pulverized and graded micro-powdered fuel, along with primary air, is supplied to burner 21 via micro-powdered fuel supply pipe 22. Secondary air heated by air preheater 42 is supplied to burner 21 via air duct 24 and air box 23. Burner 21 blows the micro-powdered fuel mixture (formed by mixing micro-powdered fuel and primary air) into furnace 11, and also blows secondary air into furnace 11. The micro-powdered fuel mixture blown into furnace 11 is ignited, forming a flame through reaction with secondary air. A flame forms in the lower region of furnace 11, and the high-temperature combustion gases rise within furnace 11 and flow into combustion gas passage 12. Furthermore, in this embodiment, air is used as the oxidizing gas (primary air, secondary air), but gases with a higher or lower oxygen content compared to air can also be used. By adjusting the ratio of oxygen content to the supplied fuel amount to an appropriate range, stable combustion is achieved in furnace 11.

[0034] Combustion gases flowing into combustion gas passage 12 exchange heat with water or steam in superheater 102, reheater 103, and economizer 104 located inside combustion gas passage 12, and are then discharged into flue 13. Nitrogen oxides are removed by denitrification device 43. After heat exchange with primary and secondary air in air preheater 42, they are further discharged into gas duct 41, where dust and other pollutants are removed by dust collection device 44. Sulfur oxides are removed by desulfurization device 46, and finally, the gases are discharged outside the system through chimney 47. Furthermore, the arrangement of the heat exchangers in combustion gas passage 12 and the devices in flue 13 to gas duct 41 does not necessarily need to follow the combustion gas flow sequence described above.

[0035] Next, using Figure 2 and Figure 3 The details of boiler system 2 are explained below.

[0036] The boiler system 2 includes the aforementioned boiler 10 and multiple mills 31 for grinding solid fuel supplied to the burner 21 of the boiler 10.

[0037] The mill 31 internally pulverizes the solid fuel supplied from the fuel supply unit 31a and discharges the pulverized solid fuel, along with the primary air (transportation gas, oxidizing gas) supplied to the mill 31, to the outside. The primary air and pulverized fuel discharged to the outside are guided to the burner 21 of the boiler 10 via the pulverized fuel supply pipe 22.

[0038] The boiler system 2 is equipped with an air supply section 30 that guides primary air to the mill 31.

[0039] The air supply unit 30 is a device that supplies primary air, used for drying and conveying pulverized fuel, into the mill 31.

[0040] In order to properly adjust the flow rate and temperature of the primary air supplied to the interior of the mill 31, in this embodiment, the air supply unit 30 includes a primary air fan (PAF) 33, a hot air flow path 30a, a cold air flow path (air piping) 30b, a hot air damper 30c, and a cold air damper (adjustment unit) 30d.

[0041] Hot air flow path 30a branches off from cold air flow path 30b. Hot air flow path 30a supplies a portion of the air delivered from the primary air fan 33 as hot air, which is then heated by the air preheater 42. On hot air flow path 30a, downstream of the air preheater 42, a hot air gate valve 30e and a hot air damper 30c are provided. The hot air gate valve 30e is an on / off valve, switched between open and closed states by the control unit 50. The opening degree of the hot air damper 30c is controlled by the control unit 50. The flow rate of the hot air supplied from hot air flow path 30a is determined based on the opening degree of the hot air damper 30c. The hot air heated by the air preheater 42 is also guided to other mills 31 via hot air flow path 30a.

[0042] The cold air flow path 30b supplies a portion of the air delivered from the primary air fan 33 as ambient temperature cold air. A cold air gate valve 30f and a cold air damper 30d are installed on the cold air flow path 30b. The cold air gate valve 30f is an on / off valve, switched between open and closed states by the control unit 50. The opening degree of the cold air damper 30d is controlled by the control unit 50. The flow rate of the cold air supplied from the cold air flow path 30b is determined based on the opening degree of the cold air damper 30d. The cold air delivered from the primary air fan 33 is also guided to other mills 31 via the cold air flow path 30b.

[0043] The hot airflow path 30a and the cold airflow path 30b merge at the downstream end to form a primary airflow path 35.

[0044] The primary air flow rate (i.e., the amount of air flowing in the primary air flow path 35) is the sum of the flow rate of hot air supplied from the hot air flow path 30a and the flow rate of cold air supplied from the cold air flow path 30b. The temperature of the primary air depends on the mixing ratio of the hot air supplied from the hot air flow path 30a and the cold air supplied from the cold air flow path 30b, and is controlled by the control unit 50.

[0045] A flow meter (air volume detection unit) 35a is installed on the primary air flow path 35 to measure the flow rate of the primary air flowing through it.

[0046] In this embodiment, the air supply section 30, the primary air flow path 35, the mill 31, and the micro fuel supply pipe 22 include an air supply section that supplies air (including primary air for combustion and air for cooling) to the burner 21 of the boiler 10.

[0047] In this embodiment, the boiler system 2 does not always have flames generated by all burners 21 (burners 21A, 21B, 21C, 21D, 21E, 21F). Instead, the number of burners 21 generating flames varies depending on the load of the boiler 10. Specifically, the higher the load of the boiler 10, the more burners 21 generate flames. Thus, the boiler 10 contains burners 21 that generate flames and burners 21 that do not generate flames.

[0048] The mill 31, connected to the burner 21 with a flame via the micron fuel supply pipe 22, is in operation. On the other hand, the mill 31, connected to the burner 21 without a flame via the micron fuel supply pipe 22, is in a stopped state.

[0049] Furthermore, a mixture of pulverized fuel and primary combustion air is supplied to the burner 21 where a flame is formed via the air supply unit. On the other hand, cooling air is supplied to the burner 21 where a flame is not formed via the air supply unit.

[0050] And, as Figure 3 As shown, boiler system 2 includes a control unit 50. The control unit 50 controls hot gas gate valve 30e, hot gas damper 30c, cold gas gate valve 30f, and cold gas damper 30d, etc. Furthermore, the control unit 50 receives information detected by flow meter 35a.

[0051] When supplying cooling air to the burner 21 where no flame is formed, the control unit 50 controls the opening of the cooling air damper 30d to supply an amount of cooling air corresponding to the load of the boiler 10. Specifically, the control unit 50 controls the opening of the cooling air damper 30d so that the lower the load of the boiler 10, the less cooling air is supplied to the burner 21 where no flame is formed.

[0052] In addition, the control unit 50 can determine the cooling air volume based on a chart or similar document that specifies the relationship between the load of the boiler 10 and the cooling air volume stored in advance, and control the opening of the cooling air damper 30d to obtain the cooling air volume.

[0053] At this time, the method for controlling the opening of the air conditioning damper 30d to achieve the determined cooling air volume is not particularly limited. For example, the control unit 50 can control the opening of the air conditioning damper 30d based on a chart or similar data that specifies the relationship between the pre-stored cooling air volume and the opening of the air conditioning damper 30d. Furthermore, the control unit 50 can control the opening of the air conditioning damper 30d based on the cooling air volume detected by the flow meter 35a.

[0054] Furthermore, the method by which the control unit 50 obtains the load of the boiler 10 is not limited. For example, the load command value of the boiler 10 can be set as the load of the boiler 10. Moreover, the control unit 50 can derive the load of the boiler 10 based on the amount of solid fuel supplied to all mills 31, that is, the total amount of fuel supplied to the boiler 10.

[0055] The control unit 50 may include, for example, a CPU (Central Processing Unit), main memory, and secondary storage. Furthermore, the control unit 50 may include a communication unit for transmitting and receiving information with other devices.

[0056] The main storage device consists of a write-capable memory such as a cache memory or RAM (Random Access Memory), and serves as a working area for reading the CPU's executable program and writing data based on the executable program.

[0057] Secondary storage devices are non-transitory computer-readable storage media. Examples of secondary storage devices include hard disks, optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0058] As an example, a series of processes used to implement various functions are stored as programs in secondary storage. The CPU reads these programs into main storage and performs information processing / analysis to achieve these functions. Alternatively, programs can be provided pre-installed in secondary storage, stored in a computer-readable storage medium, or transmitted via wired or wireless communication. Computer-readable storage media include hard disks, optical disks, CD-ROMs, DVD-ROMs, and semiconductor memories.

[0059] Next, the flow of air supplied to the burner 21 with flame and the burner 21 without flame will be explained.

[0060] [A burner that produces a flame (ignition burner)]

[0061] As described above, the mill 31 corresponding to the burner 21 in which the flame is formed is in operation.

[0062] As primary air, the air formed by the mixture of hot air flowing through the hot air flow path 30a and cold air flowing through the cold air flow path 30b from the air supply unit 30 is supplied to the mill 31 in operation via the primary air flow path 35. At this time, the opening degree of the hot air damper 30c and the cold air damper 30d is controlled by the control unit 50 to ensure that the primary air reaches a specified temperature (temperature at the outlet or inlet of the mill 31) and flow rate. Furthermore, the hot air gate valve 30e and the cold air gate valve 30f are kept in the open state by the control unit 50.

[0063] Furthermore, the mill 31, which is in operation, is supplied with solid fuel through the fuel supply section 31a and internally pulverizes the solid fuel. The mill 31, while in operation, discharges the pulverized solid fuel (fine fuel powder) along with the supplied primary air to the outside. The mixture of fine fuel powder discharged to the outside of the mill 31 and the primary air is guided to the burner 21 of the boiler 10 via the fine fuel powder supply pipe 22.

[0064] Secondary air preheated by air preheater 42 is supplied to the air box 23 of boiler 10 via air duct 24. Air box dampers (not shown) are provided in the air box 23 corresponding to each burner 21 to adjust the flow rate of secondary air supplied to each burner 21. The opening degree of the air box dampers is adjusted by control unit 50 according to the operating status of each burner 21 (ignition / extinguishing, boiler 10 load, fuel supply, etc.).

[0065] The burner 21, which forms the flame, uses the supplied primary and secondary air as combustion air and forms a flame by burning the supplied powdered fuel. At this time, the amount of secondary air is adjusted according to the opening of the bellows damper so that the air ratio near the flame is within a specified range.

[0066] [Burners that do not produce a flame (flame-out burners)]

[0067] As described above, the mill 31 corresponding to the burner 21 that does not form a flame is in a stopped state.

[0068] As cooling air, only the cold air flowing from the air supply section 30 through the cold air flow path 30b is supplied to the mill 31, which is in a stopped state, via the primary air flow path 35. At this time, the opening of the cold air damper 30d is controlled by the control unit 50 so that the lower the load on the boiler 10, the less cooling air is supplied.

[0069] use Figure 4 An example of the control performed by the control unit 50 will be explained. For example... Figure 4As shown, when the boiler 10 is under low load, the control unit 50 gradually reduces the opening of the cold air damper 30d. Specifically, compared to the case where the opening of the cold air damper 30d is kept constant when the boiler 10 is under high load (refer to the dotted line), the opening of the cold air damper 30d is reduced when the boiler 10 is under low load. However, the control performed by the control unit 50 is not limited to this. For example, the control unit 50 may control the cold air damper 30d in a manner that the opening gradually decreases as the load on the boiler 10 decreases.

[0070] And, as Figure 2 As shown, the hot air gate valve 30e is closed via the control unit 50, resulting in no airflow in the hot air path 30a. On the other hand, the cold air gate valve 30f is open via the control unit 50.

[0071] Furthermore, the mill 31, which is in a stopped state, is not supplied with solid fuel by the fuel supply unit 31a. The cooling air supplied to the mill 31, which is in a stopped state, is discharged to the outside through the inside of the mill 31. The cooling air discharged to the outside of the mill 31 is guided to the burner 21 of the boiler 10 via the fine fuel supply pipe 22.

[0072] Secondary air preheated by air preheater 42 is supplied to the air box 23 of boiler 10 via air duct 24.

[0073] The burner 21, which does not form a flame, is cooled by the supplied cooling air, thereby suppressing damage caused by radiant heat. The cooling air that has cooled the burner 21 is discharged into the furnace 11 of the boiler 10.

[0074] According to this embodiment, the following effects are achieved.

[0075] In boiler system 2, combustion air is supplied to the burner 21 where a flame is formed via an air supply section, and cooling air is supplied to the burner 21 where a flame is not formed via an air supply section to suppress damage to the burner 21 caused by radiation. Therefore, the total amount of air supplied to boiler 10 (total air volume) includes combustion air supplied to the burner 21 where a flame is formed and cooling air supplied to the burner 21 where a flame is not formed.

[0076] In this embodiment, a control unit 50 is provided, which controls the cooling air damper 30d to supply a cooling air quantity corresponding to the load of the boiler 10 to the burner 21 where no flame is formed. Therefore, the amount of cooling air supplied to the burner 21 where no flame is formed can be set to a quantity corresponding to the load of the boiler 10. Thus, the ratio of the cooling air quantity to the total air quantity can be set to a ratio corresponding to the load of the boiler 10. In other words, the ratio of the combustion air quantity to the total air quantity can be set to a ratio corresponding to the load of the boiler 10, thereby enabling the formation of a suitable combustion state in the boiler 10 and ensuring a stable state for the boiler system. Therefore, the performance and usability of the boiler 10 can be improved.

[0077] Furthermore, the burner 21 can be cooled by an appropriate amount of cooling air, thus suppressing damage caused by the heat of the burner 21 and extending its service life.

[0078] Furthermore, the lower the load on the boiler 10, the fewer the number of burners 21 that form a flame, and thus the number of burners 21 supplied with cooling air increases. Therefore, with a constant amount of cooling air supplied to the burners 21, the lower the load on the boiler 10, the greater the proportion of cooling air to total air.

[0079] On the other hand, in this embodiment, the control unit 50 controls the cooling air damper 30d so that the lower the load on the boiler 10, the less air is supplied to the burner 21 where no flame is formed. As a result, even when the boiler 10 is operating in a low-load region, it is possible to suppress an increase in the ratio of cooling air to total air volume.

[0080] Specifically, there are concerns (1) to (3) regarding the increased proportion of cooling air to total air volume.

[0081] (1) Since the cooling air and primary air are supplied to the burner 21 in the same system, an increase in the proportion of cooling air is equivalent to an increase in the primary air volume. If the proportion of primary air to total air increases, the proportion of secondary air to total air decreases. As a result, the amount of secondary air supplied to the bellows 23 decreases, and the pressure inside the bellows 23 decreases. This leads to a decrease in the pressure difference between the furnace 11 of the boiler 10 and the bellows 23. Even if the opening of the bellows damper is adjusted, secondary air may not be properly introduced from the bellows 23 to the furnace 11 of the boiler 10. Therefore, the air ratio near the flame may deviate from the specified range, and the concentration of nitrogen oxides (NOx) in the combustion exhaust may increase, which may affect the performance of the boiler 10.

[0082] On the other hand, in this embodiment, even when the boiler 10 is operating in a low-load region, the increase in the ratio of cooling air volume to total air volume can be suppressed, thus allowing secondary air to be appropriately introduced from the bellows 23 into the furnace 11 of the boiler 10. Therefore, a flame can be appropriately formed in the boiler 10.

[0083] (2) Furthermore, if the amount of cooling air increases, the amount of air bypassing the air preheater 42 (i.e., flowing in the cold air flow path 30b) also increases. As a result, the exhaust gas in the air preheater 42 is not sufficiently cooled, and the temperature of the exhaust gas discharged from the air preheater 42 to the gas duct 41 rises. Consequently, high-temperature exhaust gas is introduced into equipment (dust collection device 44, induced draft fan 45, desulfurization device 46, etc.) located downstream of the exhaust gas flow from the air preheater 42, which may result in a conflict with the upper limit of the gas temperature of the equipment or a decrease in the efficiency of the boiler 10.

[0084] On the other hand, in this embodiment, when the boiler 10 is operating in a low-load region, the amount of cooling air is reduced, thus suppressing the increase in the amount of air bypassing the air preheater 42. Therefore, it is possible to suppress the temperature rise of the exhaust gas discharged from the air preheater 42 to the gas duct 41.

[0085] (3) Furthermore, when the forced ventilation fan 32 and the primary air ventilation fan 33 are arranged side by side, the proportion of the air volume discharged by the primary air ventilation fan 33 increases and the proportion of the air volume discharged by the forced ventilation fan 32 decreases. Therefore, the opening of the rotating blades of the forced ventilation fan 32 is close to the fully closed state, which may result in poor controllability.

[0086] On the other hand, in this embodiment, when the boiler 10 is operating in a low-load region, the amount of cooling air is reduced, thus making it difficult to increase the proportion of air discharged by the primary air fan 33. Therefore, the opening of the rotating blades of the forced ventilation fan 32 is unlikely to be near full closure, thereby suppressing the deterioration of the controllability of the forced ventilation fan 32.

[0087] Furthermore, in this embodiment, the control unit 50 controls the opening degree of the cooling air damper 30d to supply the burner 21, which does not form a flame, with an amount of cooling air corresponding to the load of the boiler 10. Thus, the amount of cooling air supplied can be adjusted simply by controlling the opening degree of the cooling air damper 30d. Therefore, the amount of cooling air can be easily adjusted.

[0088] Furthermore, when the control unit 50 controls the cooling air damper 30d based on the amount of air detected by the flow meter 35a, it can more accurately set the amount of cooling air supplied to the burner 21 where no flame has formed to a quantity corresponding to the load of the boiler 10. Therefore, it is possible to more accurately set the ratio of the cooling air quantity to the total air quantity to a ratio corresponding to the load of the boiler 10.

[0089] Furthermore, in this embodiment, the control unit 50 controls the cooling air damper 30d to stop supplying solid fuel from the mill 31 to the burner 21 that does not form a flame, and supplies an amount of air from the mill 31 corresponding to the load of the boiler 10. Thus, in the boiler 10 where solid fuel is supplied from the mill 31, an appropriate amount of cooling air is supplied to the burner 21 that does not form a flame, thereby suppressing damage to the burner 21 caused by radiant heat. Furthermore, the amount of cooling air supplied to the burner 21 that does not form a flame can be set to an amount corresponding to the load of the boiler 10. Therefore, the ratio of the cooling air amount to the total air amount can be set more accurately to a ratio corresponding to the load of the boiler 10.

[0090] [Variation Example]

[0091] Next, using Figure 5 A variation of this embodiment will be described. In this variation, the control performed by the control unit 50 is different.

[0092] In the above embodiment, an example of control performed by the control unit 50 is described, namely, when supplying cooling air to the burner 21 where no flame has formed, the opening of the cooling air damper 30d is adjusted to supply an amount of cooling air corresponding to the load of the boiler 10. In this modified example, in addition to this control, the control unit 50 also performs the following control: when supplying cooling air to the burner 21 where no flame has formed, the opening of the cooling air damper 30d is adjusted to supply an amount of cooling air corresponding to the type of solid fuel supplied to the mill 31.

[0093] An example of the control performed by the control unit 50 in this modified example will be described.

[0094] First, in boiler 10, control unit 50 determines the type of solid fuel used as fuel in boiler 10 based on the heat absorption index (HAI), which is calculated by the ratio of heat exchange in the convective heat transfer section (superheater 102, reheater 103, economizer 104) to the heat exchange in the radiative heat transfer section (furnace 11). Specifically, a calculated value of 0.9 indicates a low fuel ratio solid fuel, a calculated value of 1.0 indicates a medium fuel ratio solid fuel, and a calculated value of 1.1 indicates a high fuel ratio solid fuel. Furthermore, the fuel ratio is calculated from the fixed carbon / volatile content ratio. A lower fuel ratio indicates more volatile content, resulting in higher combustibility and earlier combustion. Consequently, the radiative heat transfer in furnace 11 is relatively larger, and the HAI tends to decrease.

[0095] Next, the control unit 50 performs the following control: adjusting the opening of the cooling air damper 30d to supply a cooling air quantity corresponding to the determined fuel ratio of the solid fuel. Specifically, as follows... Figure 5 As shown, when the solid fuel is determined to have a low fuel ratio, the temperature in the furnace 11 increases, therefore the opening of the cold air damper 30d is increased compared to the case of solid fuel with other fuel ratios. Furthermore, when the solid fuel is determined to have a medium fuel ratio, the opening of the cold air damper 30d is increased compared to the case of solid fuel with a high fuel ratio. Thus, the control unit 50 controls the cold air damper 30d to open as much as possible when the fuel ratio of solid fuel is low.

[0096] Additionally, for solid fuels with calculated values ​​greater than 0.9 and less than 1.0, or greater than 1.0 and less than 1.1, parameters are used that proportionally allocate the set values ​​for each calculated value. Specifically, for example, if the calculated value is 0.95, the intermediate value between the parameter when the calculated value is 0.9 and the parameter when the calculated value is 1.0 is reflected as the parameter.

[0097] And, as Figure 4 As shown, even when solid fuel is determined to be of any fuel ratio, the control unit 50 can control the cold air damper 30d in such a way that the opening gradually decreases as the load of the boiler 10 decreases.

[0098] In addition, Figure 4 In the example, the opening degree of the air conditioning damper 30d is not less than the minimum opening degree m.

[0099] In this variation, it performs the following functions and effects.

[0100] Solid fuels have different fuel ratios (ease of combustion) depending on their type, therefore the temperature of the furnace 11 of the boiler 10 varies depending on the type of solid fuel supplied to the boiler 10. Consequently, the radiant heat to the burner 21 also varies depending on the type of solid fuel. Therefore, the amount of cooling air required to cool the burner 21, which does not form a flame, also varies depending on the type of solid fuel.

[0101] In this embodiment, the control unit 50 controls the opening of the cooling air damper 30d to supply an amount of cooling air corresponding to the type of solid fuel supplied to the mill 31. Therefore, the amount of cooling air supplied to the burner 21 (where no flame is formed) can be set to an amount corresponding to the type of solid fuel. Thus, the ratio of the cooling air amount to the total air amount can be set to a ratio corresponding to the type of solid fuel. Therefore, a suitable combustion state can be established in the boiler 10, and the amount of cooling air corresponding to the type of solid fuel can be ensured.

[0102] Furthermore, the present invention is not limited to the above-described embodiments, and appropriate modifications can be made without departing from its spirit.

[0103] For example, in the above embodiment, an example of arranging the forced ventilation fan 32 and the primary air ventilation fan 33 side by side has been described, but the present invention is not limited thereto. For example, the forced ventilation fan 32 and the primary air ventilation fan 33 may also be arranged so that a portion of the air pressurized by the forced ventilation fan 32 is guided to the primary air ventilation fan 33.

[0104] The boiler system, power generation equipment, and boiler system operation method described in the above-described embodiments can be understood as follows.

[0105] The boiler system according to the first aspect of the present invention includes: a boiler 10 having a plurality of burners 21; an air supply unit for supplying air to the burners 21; an adjustment unit 30d for adjusting the amount of air supplied to the burners 21 through the air supply unit; and a control unit 50 for controlling the adjustment unit 30d to supply an amount of cooling air corresponding to the load of the boiler 10 when cooling air is supplied to the burners 21, which are not forming a flame, through the air supply unit.

[0106] In a boiler system, combustion air is supplied to burners that produce flames via an air supply section, and cooling air is supplied to burners that do not produce flames via the same air supply section to suppress burner damage caused by radiation. Therefore, the total amount of air supplied to the boiler (total air volume) includes combustion air supplied to burners that produce flames and cooling air supplied to burners that do not produce flames.

[0107] In the above structure, a control unit is included, whose control and adjustment unit supplies cooling air to the burners that do not form a flame in an amount corresponding to the boiler load. Therefore, the amount of cooling air supplied to the burners that do not form a flame can be set to an amount corresponding to the boiler load. Thus, the ratio of the cooling air amount to the total air amount can be set to a ratio corresponding to the boiler load. In other words, the ratio of the combustion air amount to the total air amount can be set to a ratio corresponding to the boiler load, thereby ensuring an appropriate combustion state in the boiler and achieving overall optimization of the boiler system.

[0108] Furthermore, in the boiler system according to the second aspect of the present invention, in the first aspect described above, the control unit 50 controls the adjustment unit 30d so that the lower the load on the boiler 10, the less cooling air is supplied to the burner 21 that does not form a flame.

[0109] The lower the boiler load, the fewer burners that produce flame, and therefore the more burners are supplied with cooling air. Thus, with a constant amount of cooling air supplied to the burners, the lower the boiler load, the greater the proportion of cooling air to total air volume.

[0110] On the other hand, in the above structure, the control unit controls the regulating unit so that the lower the boiler load, the less air is supplied to the burners that do not form a flame. Therefore, even when the boiler is operating in a low-load region, it is possible to suppress an increase in the ratio of cooling air to total air volume.

[0111] Furthermore, in the boiler system according to the third aspect of the present invention, in the first or second aspect described above, the air supply unit has an air pipe 30b for supplying air to the burner 21, the regulating unit 30d has a damper 30d provided in the air pipe 30b and adjusting the amount of air flowing in the air pipe 30b by changing its opening, and the control unit 50 controls the opening of the damper 30d to supply the burner 21, which does not form a flame, with an amount of cooling air corresponding to the load of the boiler 10.

[0112] In the above structure, the control unit controls the opening of the damper to supply the burners, which are not yet flamed, with a cooling air quantity corresponding to the boiler load. Thus, the amount of cooling air supplied can be adjusted simply by controlling the damper opening. Therefore, the amount of cooling air can be easily adjusted.

[0113] Furthermore, the boiler system according to the fourth aspect of the present invention includes, in any one of the first to third aspects described above: an air quantity detection unit 35a that detects the amount of air supplied to the burner 21, and a control unit 50 that controls the adjustment unit 30d based on the amount of air detected by the air quantity detection unit 35a.

[0114] In the above structure, the control unit controls the regulating unit based on the amount of air detected by the air quantity detection unit. This allows for a more accurate setting of the cooling air quantity supplied to the burners where no flame has formed, corresponding to the boiler load. Consequently, it allows for a more accurate setting of the ratio of cooling air quantity to total air quantity, corresponding to the boiler load.

[0115] Furthermore, the boiler system according to the fifth aspect of the present invention, in any of the first to fourth aspects described above, includes: a plurality of mills 31 capable of supplying air or a mixture of pulverized solid fuel and air to the burner 21 via the air supply unit; the control unit 50 controls the regulating unit 30d to stop the supply of solid fuel from the mills 31 to the burner 21 where no flame is formed; and supplies cooling air from the mills 31 in an amount corresponding to the load of the boiler 10.

[0116] In the above structure, the control unit controls the regulating unit to stop the supply of solid fuel from the mill to the burners that do not form a flame, and supplies an amount of air from the mill corresponding to the boiler load. Thus, in a boiler that supplies solid fuel from the mill, cooling air can be supplied to the burners that do not form a flame, thereby suppressing burner damage caused by radiant heat. Furthermore, the amount of cooling air supplied to the burners that do not form a flame can be set to an amount corresponding to the boiler load. Therefore, the ratio of cooling air to total air volume can be set more accurately to a ratio corresponding to the boiler load.

[0117] Furthermore, in the boiler system according to the sixth aspect of the present invention, in the fifth aspect described above, the load of the boiler 10 is the amount of solid fuel supplied to the boiler 10.

[0118] In the above structure, the boiler load is the amount of solid fuel supplied to the mill. Therefore, an amount of cooling air corresponding to the amount of solid fuel supplied to the mill can be supplied to the burner where no flame is formed.

[0119] Furthermore, in the boiler system according to the seventh aspect of the present invention, in the fifth or sixth aspect described above, when the control unit 50 supplies cooling air to the burner 21 where no flame has formed, it controls the regulating unit 30d to supply an amount of cooling air corresponding to the type of solid fuel supplied to the boiler 10.

[0120] Solid fuels have different fuel ratios (ease of combustion) depending on their type, thus the boiler furnace temperature varies depending on the type of solid fuel supplied to it. Consequently, the radiant heat to the burner also varies depending on the type of solid fuel. Therefore, the amount of cooling air required to cool burners that have not yet formed a flame also varies depending on the type of solid fuel.

[0121] In the above structure, the control unit controls the regulating unit to supply cooling air in an amount corresponding to the type of solid fuel supplied to the boiler. Therefore, the amount of cooling air supplied to the burner where no flame is formed can be set to an amount corresponding to the type of solid fuel. Consequently, the ratio of the cooling air amount to the total air amount can be set to a ratio corresponding to the type of solid fuel.

[0122] The power generation equipment according to the first aspect of the present invention includes: a boiler system 2 as described in any one of the first to seventh aspects; and a power generation unit that generates electricity using steam generated in the boiler system 2.

[0123] In the boiler system operation method according to the first aspect of the present invention, the boiler system 2 includes: a boiler 10 having a plurality of burners 21; an air supply unit for supplying air to the burners 21; and an adjustment unit 30d for adjusting the amount of air supplied to the burners 21 through the air supply unit. The boiler system operation method includes: a control step in which, when supplying cooling air to the burners 21 where no flame is formed, the adjustment unit 30d is controlled to supply an amount of cooling air corresponding to the load of the boiler 10.

[0124] Symbol Explanation

[0125] 1-Power generation equipment, 2-Boiler system, 10-Boiler, 11-Furnace, 12-Combustion gas passage, 13-Flue, 21-Burner, 21A-Burner, 21B-Burner, 21C-Burner, 21D-Burner, 21E-Burner, 21F-Burner, 22-Powdered fuel supply pipe, 22A-Powdered fuel supply pipe, 22B-Powdered fuel supply pipe, 22C-Powdered fuel supply pipe, 22D-Powdered fuel supply pipe, 22E-Powdered fuel supply pipe, 22F-Powdered fuel supply pipe, 23-Wind box, 24-Air duct, 30-Air supply section, 30a-Hot airflow path, 30b-Cold airflow path (air piping), 30c-Hot air damper 30d-Cold air damper (regulating unit), 30e-Hot air gate valve, 30f-Cold air gate valve, 31-Grinding mill, 31a-Fuel supply unit, 32-Forced ventilation fan, 33-Primary air ventilation fan, 35-Primary air flow path, 35a-Flow meter (air volume detection unit), 41-Gas duct, 42-Air preheater, 43-Denitrification device, 44-Equipment, 45-Induced draft fan, 46-Desulfurization device, 47-Chimney, 50-Control unit, 101-Furnace wall, 102-Superheater, 102A-Superheater, 102B-Superheater, 102C-Superheater, 103-Reheater, 103A-Reheater, 103B-Reheater, 104-Economizer.

Claims

1. A boiler system comprising: A boiler with multiple burners; The air supply unit supplies air to the burner; and The regulating unit adjusts the amount of air supplied to the burner via the air supply unit; and The control unit controls the regulating unit to supply cooling air to the burner (which has not formed a flame) via the air supply unit, so as to supply an amount of cooling air corresponding to the load of the boiler.

2. The boiler system according to claim 1, wherein, The control unit controls the regulating unit so that the lower the load on the boiler, the less cooling air is supplied to the burner that has not formed a flame.

3. The boiler system according to claim 1, wherein, The air supply unit has air piping that supplies air to the burner. The regulating unit has a damper installed in the air piping and the amount of air flowing in the air piping is adjusted by changing its opening degree. The control unit controls the opening of the damper to supply the burner, which does not produce a flame, with an amount of cooling air corresponding to the load of the boiler.

4. The boiler system according to claim 1, comprising: The air volume detection unit detects the amount of air supplied to the burner. The control unit controls the adjustment unit based on the amount of air detected by the air quantity detection unit.

5. The boiler system according to claim 1, comprising: Multiple mills are capable of supplying air or a mixture of pulverized solid fuel and air to a specific burner via the air supply unit. The control unit controls the regulating unit to stop the supply of solid fuel from the mill to the burner that does not form a flame, and to supply cooling air from the mill in an amount corresponding to the load of the boiler.

6. The boiler system according to claim 5, wherein, The load of the boiler is the amount of solid fuel supplied to the boiler.

7. The boiler system according to claim 5, wherein, When the control unit supplies cooling air to the burner where no flame has formed, it controls the regulating unit to supply an amount of cooling air corresponding to the type of solid fuel supplied to the boiler.

8. A power generation device, comprising: The boiler system according to any one of claims 1 to 7; and The power generation unit uses the steam generated in the boiler system to generate electricity.

9. A method for operating a boiler system, the boiler system comprising: A boiler with multiple burners; The air supply unit supplies air to the burner; and The regulating unit regulates the amount of air supplied to the burner through the air supply unit. The operation method of the boiler system includes: The control process involves supplying cooling air to the burner (which has not yet formed a flame) via the air supply unit, and controlling the regulating unit to supply an amount of cooling air corresponding to the load of the boiler.

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