JP2020098071A - Boiler and control method for the same - Google Patents

Abstract

To appropriately reduce NOx and CO.SOLUTION: A boiler 1 includes a can body 10 having water pipes 51, 52, 53, a burner 16 connected to the can body 10 for supplying primary fuel F1 and air into the can body 10, a secondary fuel supply part 24 for supplying secondary fuel F2 into the can body 10 on the further downstream side than the burner 16, an exhaust line 26 where combustion gas exhausted from the internal of the can body 10 is distributed, and a control part for controlling the connection state of the exhaust line 26 to the burner 16, the supply of the primary fuel F1, and the supply of the secondary fuel F2. The control part, in the case of a first combustion stage, supplies mixed gas produced by mixing the combustion gas G0 and the secondary fuel F2 into the can body 10 while allowing the burner 16 to supply the primary fuel F1 thereinto, and in the case of a second combustion stage where a combustion amount is larger, supplies the mixed gas produced by mixing the combustion gas G0 and the secondary fuel F2 into the can body 10 while supplying mixed gas produced by mixing the combustion gas G0 and the primary fuel F1 into the can body 10.SELECTED DRAWING: Figure 2

Description

The present invention relates to a boiler and a boiler control method.

As a boiler that generates steam by using heat generated by burning fuel gas, for example, as in Patent Documents 1 and 2, a fuel supply that further supplies fuel gas to a downstream side of a burner that supplies fuel gas into a can body. Some parts are equipped with a part to perform two-stage combustion. Patent Documents 1 and 2 describe that the above configurations can reduce NOx, CO, and oxygen concentrations contained in exhaust gas. Further, Patent Document 2 describes that exhaust gas from the can body is sucked by an ejector and recirculated to the can body.

JP, 2006-220373, A JP, 2011-133180, A

For example, in Patent Document 2, the position where the combustion gas is supplied is adjusted according to the amount of combustion, but for two-stage combustion as in Patent Documents 1 and 2, NOx and NOx There is room for further improvement in reducing CO.

The aspect of this invention aims at providing the boiler and the control method of a boiler which reduce NOx and CO appropriately.

According to the aspect of the present invention, a can body having a water pipe, a burner connected to the can body and capable of supplying primary fuel and air into the can body, and a downstream side of the burner in the flow direction of combustion gas. A secondary fuel supply unit capable of supplying a secondary fuel into the can body, a discharge line through which combustion gas discharged from the can body flows, a connection state between the discharge line and the burner, and the discharge line. A control unit for controlling the connection state with the secondary fuel supply unit, the supply of the primary fuel, and the supply of the secondary fuel, wherein the control unit is the first combustion stage, By connecting the exhaust line and the secondary fuel supply section while supplying the primary fuel to the burner, the combustion gas from the exhaust line and the secondary fuel from the secondary fuel supply section are connected. By supplying the mixed gas mixed in the can body, and when the combustion amount in the can body is the second combustion stage which is larger than the first combustion stage, by connecting the discharge line and the burner, While supplying the mixed gas obtained by mixing the combustion gas from the discharge line and the primary fuel from the burner into the can body, by connecting the discharge line and the secondary fuel supply unit, A boiler is provided which supplies a mixed gas, which is a mixture of the combustion gas from the discharge line and the secondary fuel from the secondary fuel supply unit, into the can body.

According to the aspect of the present invention, a can body having a water pipe, a burner connected to the can body and capable of supplying primary fuel and air into the can body, and a downstream side of the burner in the flow direction of combustion gas. A method of controlling a boiler, comprising: a secondary fuel supply unit capable of supplying a secondary fuel into the can body; and an exhaust line through which combustion gas discharged from the can body flows, the first combustion stage In this case, by connecting the discharge line and the secondary fuel supply section while supplying the primary fuel to the burner, the combustion gas from the discharge line and the secondary fuel supply section from the secondary fuel supply section are connected. When the mixed gas mixed with the secondary fuel is supplied into the can body and the combustion amount in the can body is the second combustion stage which is larger than the first combustion stage, the discharge line and the burner By connecting the combustion gas from the discharge line and the mixed gas obtained by mixing the primary fuel from the burner into the can, while connecting the discharge line and the secondary fuel supply unit. A boiler control method is provided in which a mixed gas, in which the combustion gas from the discharge line and the secondary fuel from the secondary fuel supply unit are mixed, is supplied to the can body by connecting the two. ..

According to the aspect of the present invention, a boiler and a boiler control method for appropriately reducing NOx and CO are provided.

FIG. 1 is a schematic sectional view of a boiler according to this embodiment. FIG. 2 is a schematic partial cross-sectional view of the boiler according to this embodiment. FIG. 3 is a schematic diagram illustrating fuel supply in the first combustion stage. FIG. 4 is a schematic diagram illustrating fuel supply in the second combustion stage. FIG. 5 is a schematic block diagram of the control device according to the present embodiment. FIG. 6 is a flowchart illustrating the control flow of the control unit according to this embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The constituent elements of the embodiments and modifications described below can be appropriately combined. In addition, some components may not be used.

In the following description, the combustion gas is a concept including at least one of the one in which the combustion reaction of the fuel gas is completed and the fuel gas in the combustion reaction, and the one in which the combustion reaction of the fuel gas is completed and the fuel in the combustion reaction. The concept includes both the case of having both of the gases, the case of having only the fuel gas in the combustion reaction, and the case of having only the one in which the combustion reaction of the fuel gas is completed.

(Overall structure of boiler)
FIG. 1 is a schematic sectional view of a boiler according to this embodiment. FIG. 2 is a schematic partial cross-sectional view of the boiler according to this embodiment. FIG. 2 is a schematic partial cross-sectional view when the boiler 1 according to the first embodiment is viewed from the Z direction side described later, that is, when the boiler 1 is looked down from above in the vertical direction. As shown in FIGS. 1 and 2, the boiler 1 according to the first embodiment includes a can body 10, a blower 12, a duct 14, a burner 16, an exhaust stack 18, and a fuel supply unit 20 (see FIG. 2 ). ), a primary fuel supply unit 22, a secondary fuel supply unit 24 (see FIG. 2 ), a discharge line 26 (see FIG. 2 ), and a control device 30.

As shown in FIG. 1, the can body 10 includes a main body portion 40, an upper header 42, a lower header 44, and a water pipe group 50. In the present embodiment, the X direction is the flow direction of the combustion gas flowing inside the main body 40. Further, a direction that is orthogonal to the X direction and is along the vertical direction and that is directed toward the upper side in the vertical direction is referred to as the Z direction. The Z direction is a direction overlapping with the vertical direction in the present embodiment, but is not limited to the vertical direction. The main body 40 is a housing whose longitudinal direction is along the X direction, and accommodates the water tube group 50 therein. The upper header 42 is a header connected to the end of the main body 40 on the Z direction side, here, the vertical direction side. The lower header 44 is a header connected to the end of the main body 40 on the side opposite to the Z direction, here, the lower side in the vertical direction.

The water pipe group 50 has a plurality of water pipes 51, 52, 53 through which water or steam flows. The water pipes 51, 52, 53 are provided in the main body 40, extend along the direction Z, and connect the upper header 42 and the lower header 44. As shown in FIG. 2, the plurality of water pipes 51 (outer water pipes) are located at both ends of the main body 40, and are arranged along the direction in which the combustion gas flows, that is, the direction X. The plurality of water pipes 53 (central water pipes) are located inside the water pipe 51 and are arranged along the direction X. The plurality of water pipes 52 (intermediate water pipes) are located between the water pipes 51 and 53 and are arranged along the direction X. In addition, a connection wall 54 that extends along the direction X and connects the plurality of water pipes 51 is provided in the main body 40. The space surrounded by the water pipe 51, the connecting wall 54, the upper header 42, and the lower header 44 forms a gas flow space. Further, the water pipes 52 are arranged such that the distance between the some water pipes 52 along the direction X is longer than the distance between the other water pipes 52 along the direction X. That is, a part of the water pipe 52 is removed. In the gas flow space, the space between the water pipes 52 having the long distance, that is, the space removed from the water pipes 52 is wider than the space between the other water pipes. Hereinafter, the space between the water pipes 52 having a long distance is referred to as a combustion promotion space S. Since the combustion promotion space S is kept wide, combustion, that is, oxidation of CO in the combustion gas is promoted. The combustion promoting space S is not limited to the space between the water pipes 52 as long as it is kept wider than the other space surrounded by the water pipes, and is a space surrounded by arbitrary water pipes. Good. For example, in the main body portion 40, by making the diameter of the water pipe in the upstream space in the combustion gas flow direction smaller than the diameter of the downstream space in the combustion gas flow direction, the upstream in the combustion gas flow direction The pitch of the water tubes in the side space may be larger than the pitch of the water tubes in the space on the downstream side in the flow direction of the combustion gas. However, the combustion promoting space S does not necessarily have to be provided.

The blower 12 supplies the air A for mixing with the primary fuel F1 described later. The duct 14 is a duct connected to the blower 12, and the air A supplied from the blower 12 flows. In addition, the duct 14 is connected to the primary fuel supply unit 22. Specifically, as shown in FIG. 2, the primary fuel supply unit 22 has a fuel supply line 60 and a primary fuel adjustment valve 62. The fuel supply line 60 has one end connected to the fuel supply unit 20 that supplies the fuel F, and the other end connected to the duct 14. Further, the fuel supply line 60 is provided with a primary fuel adjustment valve 62. The fuel F supplied from the fuel supply unit 20 flows through the fuel supply line 60, and at least a part of the flowing fuel F is supplied into the duct 14 as the primary fuel F1 via the primary fuel adjustment valve 62. The primary fuel F1 supplied from the fuel supply line 60 is mixed with the air A supplied from the blower 12 in the duct 14 to generate a mixed gas F1A. The fuel F (that is, the primary fuel F1 and the secondary fuel F2 described later) is a combustible fuel gas such as natural gas or propane gas, but may be any fuel. The opening/closing of the primary fuel adjusting valve 62 is controlled by the control device 30 to adjust the supply amount of the primary fuel F1 to the duct 14. Although described later in detail, in the second combustion stage, the duct 14 is supplied with the combustion gas G0 from the exhaust line 26. In this case, the mixed gas F1A is composed of the primary fuel F1, the air A, and the combustion gas G0. It becomes a mixed gas.

Further, as shown in FIG. 1, the duct 14 has a pressure reducing member 12A on the upstream side of the flow of the air A with respect to the location where the fuel supply line 60 is connected. The depressurizing member 12A is a member that lowers the pressure of the air A on the downstream side of the flow of the air A than itself by lowering the pressure of the air A on the upstream side of the flow of the air A, for example, by narrowing the flow path. Is. The pressure reducing member 12A is, for example, punching metal in the present embodiment. Further, the boiler 1 has an air differential pressure sensor 12B that detects a differential pressure between the pressure on the downstream side of the pressure reducing member 12A and the pressure on the downstream side of the pressure reducing member 12A. The air differential pressure sensor 12B detects the differential pressure between the pressure of the air A on the downstream side of the pressure reducing member 12A in the duct 14 and the pressure of the air A on the upstream side of the pressure reducing member 12A, and provides information on the detected differential pressure. Output to the control device 30.

Further, as shown in FIG. 2, the primary fuel supply unit 22 further includes a pressure reducing member 64 and a fuel differential pressure sensor 66. The pressure reducing member 64 is provided in the fuel supply line 60, and for example, by narrowing the flow path, the pressure reducing member 64 is more downstream than the pressure of the primary fuel F1 on the upstream side of the flow of the fuel F than itself and the downstream side of the flow of the fuel F on itself. It is a member that lowers the pressure of the primary fuel F1. More specifically, the pressure reducing member 64 is provided on the downstream side of the primary fuel regulating valve 62 and on the upstream side of the connection point of the fuel supply line 60 with the duct 14. In the present embodiment, the pressure reducing member 64 is, for example, an orifice. Further, the fuel differential pressure sensor 66 detects the differential pressure between the pressure on the downstream side of the pressure reducing member 64 and the pressure on the downstream side of the pressure reducing member 64. The fuel differential pressure sensor 66 detects the differential pressure between the pressure of the primary fuel F1 downstream of the pressure reducing member 64 and the pressure of the primary fuel F1 upstream of the pressure reducing member 64 in the fuel supply line 60, and the detected difference is detected. The pressure information is output to the control device 30.

The duct 14 is also connected to the main body portion 40 of the can body 10. The duct 14 is connected to a portion of the main body 40 opposite to the direction X, that is, an upstream portion in the flow direction of the combustion gas. Further, a burner 16 is provided at the connection point between the duct 14 and the main body 40. That is, it can be said that the burner 16 is connected to the can body 10 and is connected to a location on the opposite side of the main body portion 40 in the direction X. The mixed gas F1A flowing through the duct 14 is supplied to the burner 16. The burner 16 supplies the mixed gas F1A, that is, the primary fuel F1 and the air A into the main body portion 40 of the can body 10.

The exhaust pipe 18 is connected to the main body portion 40 of the can body 10, and more specifically, is connected to the portion on the direction X side of the main body portion 40 (the most downstream portion in the combustion gas flow direction). The combustion gas in the body 40 is discharged from the body 40 to the exhaust stack 18 as exhaust gas.

The secondary fuel supply unit 24 supplies the secondary fuel F2 into the can body 10 on the downstream side of the burner 16 in the flow direction of the combustion gas.

The secondary fuel supply unit 24 has secondary fuel supply lines 70 and 74 and a secondary fuel control valve 72, as shown in FIG. The secondary fuel supply line 70 is connected to the fuel supply line 60. More specifically, the secondary fuel supply line 70 is connected to the fuel supply line 60 at a location between the connection location of the fuel supply section 20 and the connection location of the primary fuel regulating valve 62. Therefore, in the fuel supply line 60, at least a part of the fuel F is supplied as the secondary fuel F2 from the fuel supply unit 20. The secondary fuel adjustment valve 72 is provided in the secondary fuel supply line 70. The opening/closing of the secondary fuel adjustment valve 72 is controlled by the control device 30 to adjust the supply amount of the secondary fuel F2 to the secondary fuel supply line 70.

The secondary fuel supply line 74 is connected to a position on the downstream side of the flow of the secondary fuel F2 with respect to the connection position of the secondary fuel supply line 70 with the secondary fuel adjustment valve 72. The secondary fuel supply line 74 is supplied with the secondary fuel F2 from the secondary fuel supply line 70 via the secondary fuel adjustment valve 72. The secondary fuel supply line 74 is also connected to the main body portion 40 of the can body 10. More specifically, the secondary fuel supply line 74 is connected to a portion of the main body 40 on the direction X side (downstream in the combustion gas flow direction) with respect to the connection portion with the burner 16. Therefore, the secondary fuel supply line 74 supplies the secondary fuel F2 from the secondary fuel supply line 70 into the can body 10 on the downstream side of the burner 16 in the flow direction of the combustion gas. Furthermore, the secondary fuel supply line 74 is connected to the downstream side of the location in the can body 10 where combustion with the primary fuel F1 starts, that is, the downstream side of the ignition means (not shown). Further, the secondary fuel supply line 74 should be connected to a position where the temperature of the combustion gas is 800° C. or higher, that is, a position where the secondary fuel F2 is appropriately self-combusted and the generation of CO can be suppressed. Is preferred. Further, the secondary fuel supply line 74 is preferably connected to a location on the opposite side of the combustion promoting space S to the direction X (upstream side in the combustion gas flow direction). In the present embodiment, two secondary fuel supply lines 74 are provided branching from the secondary fuel supply line 70, and each of them is connected to the main body 40. However, the number of the secondary fuel supply lines 74 is arbitrary and may be one, for example.

In the exhaust line 26, the combustion gas G0 exhausted from the inside of the can body 10, that is, the exhaust gas exhausted to the exhaust pipe 18, flows. As shown in FIG. 2, the discharge line 26 includes a discharge line 80, a flow rate adjusting unit 81, a primary discharge line 82, a secondary discharge line 84, a primary connection valve 86, and a secondary connection valve 88. .. The discharge line 80 is connected to the exhaust stack 18. The exhaust line 80 is supplied with the exhaust gas from the exhaust stack 18, that is, the combustion gas G0 exhausted from the can body 10.

The flow rate adjusting unit 81 is provided in the discharge line 80. The flow rate adjusting unit 81 adjusts the supply amount of the combustion gas G0 introduced into the can body 10 through the discharge line 80 under the control of the control device 30. In this embodiment, the flow rate adjusting unit 81 is a fan. The flow rate adjusting unit 81 sucks the combustion gas G0 from the exhaust stack 18 and supplies the combustion gas G0 into the exhaust line 80. The flow rate adjusting unit 81 adjusts the supply amount of the combustion gas G0 to be supplied to the can body 10 by controlling the number of rotations of the built-in blades (not shown) by the control device 30. However, the flow rate adjusting unit 81 is not limited to controlling the rotation speed as long as the supply amount of the combustion gas G0 supplied by the control of the control device 30 can be adjusted, and the supply amount of the combustion gas G0 can be set by any method. May be adjusted. For example, the flow rate adjusting unit 81 may adjust the supply amount of the combustion gas G0 by controlling the opening degree of the built-in vane.

One end of the primary discharge line 82 is connected to the discharge line 80 as shown in FIG. 2, and the other end is connected to the suction port 12a of the blower 12 as shown in FIG. The suction port 12a is an inlet through which the blower 12 takes in air (outside air). Note that the blower 12 is not actually visible in the cross-sectional view of FIG. 2, but for convenience of description, also in FIG. 2, the other end of the primary discharge line 82 is connected to the suction port 12 a of the blower 12. Is shown. The same applies to FIGS. 3 and 4 described later. More specifically, one end of the primary discharge line 82 is connected to the upstream side of the discharge line 80 where the flow rate adjusting unit 81 is provided in the flow direction of the combustion gas G0. Further, since the blower 12 is connected to the burner 16 via the duct 14, it can be said that the other end of the primary discharge line 82 is connected to the burner 16. A primary connection valve 86 is provided in the primary discharge line 82. The opening of the primary connection valve 86 is controlled by the control device 30, and the connection state between the discharge line 80 and the primary discharge line 82, in other words, the connection state between the discharge line 26 and the blower 12 (or the burner 16) is switched. That is, in the closed state, the primary connection valve 86 disconnects the discharge line 80 and the primary discharge line 82, that is, the discharge line 26 and the blower 12. In the open state, the primary connection valve 86 connects the discharge line 80 and the primary discharge line 82, that is, the discharge line 26 and the blower 12. Although the primary discharge line 82 is directly connected to the blower 12, it may be connected to the duct 14 or the fuel supply line 60, for example. Further, since the primary discharge line 82 is connected to the discharge line 80 on the upstream side of the flow rate adjusting unit 81, it becomes possible to supply the combustion gas G0 to the primary discharge line 82 by operating the blower 12, and the primary discharge line 82 is discharged. It is not necessary to operate the flow rate adjusting unit 81 when supplying the combustion gas G0 to the line 82. As a result, power such as electric power can be suppressed because the flow rate adjusting unit 81 is not operated. However, the primary discharge line 82 is not limited to being connected to the discharge line 80 on the upstream side of the flow rate adjusting unit 81, and may be connected to the downstream side of the flow rate adjusting unit 81, for example.

When the primary connection valve 86 is in the open state, the primary exhaust line 82 is connected to the exhaust line 80 to allow the combustion gas G0 to flow from the exhaust line 80, so the combustion supplied from the exhaust stack 18 to the exhaust line 80. Gas G0 is supplied. The primary exhaust line 82 supplies the supplied combustion gas G0 to the blower 12. Since the air A is supplied from the blower 12, the air A and the combustion gas G0 are supplied from the blower 12 to the duct 14. In the duct 14, the air and the combustion gas G0 are mixed with the primary fuel F1, and the mixed gas F1A in which the combustion gas G0, the air A, and the primary fuel F1 are mixed is supplied from the burner 16 into the can body 10. Further, in the primary discharge line 82, the supply amount of the combustion gas G0 supplied to the blower 12 changes according to the opening degree of the primary connection valve 86. That is, the larger the opening degree of the primary connection valve 86, the larger the supply amount of the combustion gas G0 supplied to the blower 12. On the other hand, when the primary connection valve 86 is closed, the primary discharge line 82 is disconnected from the discharge line 80 and the flow of the combustion gas G0 from the discharge line 80 is stopped, so that the combustion gas G0 to the blower 12 is discharged. Stop the supply. In this case, since the combustion gas G0 is not supplied to the blower 12, the mixed gas F1A in which the air A and the primary fuel F1 are mixed is supplied from the burner 16 into the can body 10.

The secondary discharge line 84 has one end connected to the discharge line 80 and the other end connected to the secondary fuel supply unit 24. Specifically, one end of the secondary discharge line 84 is connected to the downstream side of the discharge line 80 where the flow rate adjusting unit 81 in the flow direction of the combustion gas G0 is provided. That is, the discharge line 80 is branched into the primary discharge line 82 and the secondary discharge line 84. In addition, the other end of the secondary discharge line 84 is a portion of the secondary fuel supply line 70 on the downstream side of the flow of the secondary fuel F2 with respect to the connection portion of the secondary fuel adjustment valve 72. The secondary fuel supply line 74 is connected to a location upstream of the connection location of the secondary fuel F2.

A secondary connection valve 88 is provided in the secondary discharge line 84. The opening degree of the secondary connection valve 88 is controlled by the control device 30, so that the connection state between the discharge line 80 and the secondary discharge line 84, in other words, the connection between the discharge line 26 and the secondary fuel supply unit 24. Switch states. That is, in the closed state, the secondary connection valve 88 disconnects the exhaust line 80 and the secondary exhaust line 84, that is, the exhaust line 26 and the secondary fuel supply unit 24. In the open state, the secondary connection valve 88 connects the discharge line 80 and the secondary discharge line 84, that is, the discharge line 26 and the secondary fuel supply unit 24.

When the secondary connection valve 88 is open, the secondary exhaust line 84 is connected to the exhaust line 80, and the combustion gas G0 can flow from the exhaust line 80. Therefore, the secondary exhaust line 84 is supplied from the exhaust stack 18 to the exhaust line 80. Further, the combustion gas G0 is supplied, and the supplied combustion gas G0 is supplied into the secondary fuel supply line 70. Further, the secondary fuel F2 is supplied to the secondary fuel supply line 70. Therefore, in this case, in the secondary fuel supply lines 70 and 74, the combustion gas G0 is mixed with the secondary fuel F2, and the mixed gas F2A in which the combustion gas G0 and the secondary fuel F2 are mixed is the secondary fuel. It is supplied into the can 10 from the supply line 74. Further, in the secondary discharge line 84, the supply amount of the combustion gas G0 supplied to the secondary fuel supply line 70 changes according to the opening degree of the secondary connection valve 88. That is, the larger the opening degree of the secondary connection valve 88, the larger the supply amount of the combustion gas G0 supplied to the secondary fuel supply line 70. When the secondary connection valve 88 is closed, the secondary discharge line 84 is disconnected from the discharge line 80 and the flow of the combustion gas G0 from the discharge line 80 is stopped. The supply to the fuel supply line 70 is stopped.

In the present embodiment, the discharge line 80, the primary discharge line 82, the secondary discharge line 84, the secondary fuel supply line 70, and the secondary fuel supply line 74 are described as separate pipes. doing. However, since the discharge line 80, the primary discharge line 82, the secondary discharge line 84, the secondary fuel supply line 70, and the secondary fuel supply line 74 are connected, the discharge line 80 and the primary discharge line are connected. The line 82, the secondary discharge line 84, the secondary fuel supply line 70, and the secondary fuel supply line 74 can be rephrased as one pipe.

(Control by control device)
Next, the control device 30 will be described. The control device 30 controls the supply of the primary fuel F1, the air A, the secondary fuel F2, and the combustion gas G0 into the can body 10. Further, the control device 30 controls the connection state between the discharge line 26 and the blower 12 (or the burner 16) and the connection state between the discharge line 26 and the secondary fuel supply unit 24. The control device 30 executes different controls in the first combustion stage and the second combustion stage. The first combustion stage refers to a low combustion mode in which the amount of combustion in the can 10 is low, in other words, the case where the supply amount of the primary fuel F1 is low. The second combustion stage refers to a high combustion mode in which the amount of combustion in the can 10 is larger than that in the first combustion stage, in other words, the supply amount of the primary fuel F1 is larger than that in the first combustion stage. The control device 30 determines whether the first combustion stage is the first combustion stage or the second combustion stage in accordance with the combustion stage instructed to the boiler 1, that is, the combustion stage in which the boiler 1 is operated. Determine if there is. For example, in a boiler with three-position control of stop, low combustion, and high combustion, the first combustion stage is low combustion and the second combustion stage is high combustion. Further, for example, when the planned supply amount of the primary fuel F1 is within the predetermined range, the control device 30 determines that it is the first combustion stage, and the planned supply amount of the primary fuel F1 is larger than the upper limit value of the predetermined range. In this case, it may be determined that it is the second combustion stage. For example, in a 4-position control boiler of stop, low-combustion, medium-combustion, and high-combustion, the first combustion stage may be low-combustion, medium-combustion and high-combustion, and the first combustion stage may be low-combustion and medium-burn Combustion and the second combustion stage may be high combustion. The predetermined range here may be set arbitrarily.

FIG. 3 is a schematic diagram illustrating fuel supply in the first combustion stage. As shown in FIG. 3, in the first combustion stage, the control device 30 controls the opening of the primary fuel adjustment valve 62 to supply the primary fuel F1 to the blower 12, and controls the blower 12 to control the blower 12. To supply air A. Further, in the first combustion stage, the control device 30 controls the opening degree of the secondary fuel adjustment valve 72 to supply the secondary fuel F2 to the can body 10 via the secondary fuel supply line 74. Further, in the first combustion stage, the control device 30 closes the primary connection valve 86 to disconnect the exhaust line 26 and the blower 12 (or the burner 16) from each other, and the combustion gas to the blower 12 is discharged. Stop the G0 supply. On the other hand, in the case of the first combustion stage, the control device 30 opens the secondary connection valve 88 to connect the discharge line 26 and the secondary fuel supply line 74, and controls the flow rate adjustment unit 81. As a result, the combustion gas G0 is supplied to the can body 10 from the secondary fuel supply line 74. That is, in the first combustion stage, the control device 30 causes the burner 16 to supply the mixed gas F1A in which the air A and the primary fuel F1 are mixed into the can body 10, and the burner 16 into the can body 10. Supply of the combustion gas G0, that is, the mixing of the primary fuel F1 and the combustion gas G0 is stopped. Further, in the first combustion stage, the control device 30 supplies the mixed gas F2A, which is a mixture of the combustion gas G0 and the secondary fuel F2, to the can body 10 from the secondary fuel supply line 74. As described above, the boiler 1 performs the two-stage combustion by supplying the mixed gas F1A and F2A from the burner 16 and the secondary fuel supply line 74. That is, the mixed gas F1A supplied from the burner 16 into the can body 10 is ignited by an igniting means (not shown), and the burner 16 forms a combustion gas in a combustion reaction accompanied by a flame. The combustion gas flows in the direction X side while exchanging heat with the water pipes 51, 52, 53 in the main body 40. Then, the mixed gas F2A supplied to the can body 10 from the secondary fuel supply line 74 comes into contact with the combustion gas and burns. The combustion gas, which is supplied with the mixed gas F2A and has undergone two-stage combustion, further flows to the direction X side while exchanging heat with the water pipes 51, 52, and 53 in the main body 40, and is exhausted from the exhaust stack 18 as exhaust gas.

FIG. 4 is a schematic diagram illustrating fuel supply in the second combustion stage. As shown in FIG. 4, in the second combustion stage, the control device 30 controls the opening of the primary fuel adjustment valve 62 to supply the primary fuel F1 to the blower 12, and controls the blower 12 to control the duct 14. To supply air A. Further, in the second combustion stage, the control device 30 controls the opening degree of the secondary fuel adjustment valve 72 and supplies the secondary fuel F2 to the can body 10 via the secondary fuel supply line 74. Further, in the second combustion stage, the control device 30 controls the opening degree while maintaining the primary connection valve 86 and the secondary connection valve 88 in the open state, and controls the flow rate adjustment unit 81. Thus, the control device 30 connects the exhaust line 26 and the blower 12 (or the burner 16) and the exhaust line 26 and the secondary fuel supply line 74 to each other in the burner 16 in the second combustion stage. Also, the combustion gas G0 is supplied to the can body 10 from the secondary fuel supply line 74. That is, in the case of the second combustion stage, the control device 30 causes the burner 16 to supply the mixed gas F1A in which the primary fuel F1, the air A, and the combustion gas G0 are mixed, to the combustion gas G0 and the combustion gas G0. The mixed gas F2A mixed with the secondary fuel F2 is supplied to the can body 10 from the secondary fuel supply line 74. In the second combustion stage, the same two-stage combustion as in the first combustion stage occurs except that the combustion gas G0 is mixed with the primary fuel F1.

As described above, the control device 30 mixes the combustion gas G0 with the secondary fuel F2 in the first combustion stage, and mixes the combustion gas G0 with the primary fuel F1 and the secondary fuel F2 in the second combustion stage. The configuration of the control device 30 will be described below.

FIG. 5 is a schematic block diagram of the control device according to the present embodiment. As shown in FIG. 5, the control device 30 has a control unit 90 and a storage unit 92. The control device 30 is a computer that controls the boiler 1. The storage unit 92 is a memory that stores the calculation content of the control unit 90, the program information, and the like. The storage unit 92 includes at least one external storage device such as a RAM (Random Access Memory), a ROM (Read Only Memory), and a flash memory (Flash Memory).

The control unit 90 is an arithmetic device, that is, a CPU (Central Processing Unit). The control unit 90 includes an air control unit 94, a primary fuel control unit 96, a secondary fuel control unit 98, and a combustion gas control unit 99. The air control unit 94, the primary fuel control unit 96, the secondary fuel control unit 98, and the combustion gas control unit 99 execute the processing described below by reading the software (program) stored in the storage unit 92. To do. However, the air control unit 94, the primary fuel control unit 96, the secondary fuel control unit 98, and the combustion gas control unit 99 may be configured by dedicated hardware circuits.

The air control unit 94 calculates the supply amount of the air A supplied to the can body 10 and controls the supply amount of the air A supplied to the can body 10 so that the calculated supply amount is obtained. Specifically, the air control unit 94, for example, according to the combustion stage instructed to the boiler 1, that is, in accordance with the instruction of what combustion stage the boiler 1 is to be operated, the supply amount of the air A. To calculate. For example, in the present embodiment, information indicating the relationship between the combustion stage and the amount of air A is stored in the storage unit 92. The air control unit 94 reads out this information from the storage unit 92 and substitutes the instructed combustion stage into this relationship to calculate the supply amount of the air A. For example, the supply amount of the air A is set to increase as the instructed combustion stage increases, that is, as the combustion increases. The method of calculating the supply amount of the air A is not limited to this, and may be set arbitrarily.

The air control unit 94 controls the blower 12 so that the amount of air A calculated in this way is supplied. For example, the air control unit 94 supplies the calculated amount of air A to the duct 14 by adjusting the opening degree of a damper (not shown) provided on the upstream side of the pressure reducing member 12A shown in FIG. For example, the air control unit 94 acquires information on the differential pressure between the upstream side and the downstream side of the pressure reducing member 12A from the air differential pressure sensor 12B shown in FIG. The air control unit 94 acquires the amount of the air A actually supplied to the duct 14 from the information on the differential pressure detected by the air differential pressure sensor 12B, and calculates it based on the acquired actual supply amount of the air A. The opening degree of the damper is adjusted so that the amount of air A actually supplied is adjusted. The air control unit 94 is not limited to adjusting the opening degree of the damper when controlling the supply amount of the air A. For example, the air control unit 94 may control the supply amount of the air A by controlling the rotation speed of the blower 12 by an inverter, or may control the supply amount of the air A using both the inverter and the damper. You may.

The primary fuel control unit 96 calculates the supply amount of the primary fuel F1 supplied to the can body 10 and controls the supply amount of the primary fuel F1 supplied to the can body 10 so that the calculated supply amount is obtained. Specifically, the primary fuel control unit 96 calculates the target supply amount of the primary fuel F1 based on the information on the combustion stage and the supply amount of the air A to the duct 14. The primary fuel control unit 96 acquires the information on the combustion stage based on the information on the designated combustion stage. In addition, the primary fuel control unit 96 acquires information on the differential pressure between the upstream side and the downstream side of the pressure reducing member 12A from the air differential pressure sensor 12B shown in FIG. 1, and from the acquired differential pressure information to the duct 14. The information of the supply amount of the air A is acquired. Further, the primary fuel control unit 96 may acquire information on the supply amount of the air A from the air control unit 94. In the present embodiment, the storage unit 92 stores information indicating the relationship between the amount of air A, the amount of primary fuel F1, and the combustion stage. In the information indicating this relationship, since the relationship between the amount of air A and the amount of primary fuel F1 is different for each combustion stage, the relationship between the amount of air A and the amount of primary fuel F1 is changed for each combustion stage. It can be said that the information is set. The primary fuel control unit 96 reads information indicating the relationship between the amount of air A and the amount of primary fuel F1 at the acquired combustion stage from the storage unit 92, and substitutes the acquired supply amount of air A into this relationship. Thus, the target supply amount of the primary fuel F1 is calculated. The target supply amount of the primary fuel F1 in the first combustion stage is preferably about 8% so that the proportion of oxygen contained in the combustion gas after combustion of the primary fuel F1 is, for example, 6% or more and 10% or less. Is set to be. Further, the target supply amount of the primary fuel F1 in the second combustion stage is more specifically, for example, 4 so that the proportion of oxygen contained in the combustion gas after the combustion of the primary fuel F1 is lower than that in the first combustion stage. % To 8% or less, preferably about 6%. As described above, the boiler 1 controls the primary fuel control unit 96 to supply the target supply amount of the primary fuel F1 calculated based on the information indicating the relationship between the amount of the air A and the amount of the primary fuel F1. However, the method of supplying the target supply amount of the primary fuel F1 is not limited to this. For example, in the boiler 1, a mechanical governor is provided in the fuel supply line 60, and the governor operates according to the differential pressure between the upstream side and the downstream side of the pressure reducing member 12A (that is, the differential pressure detected by the air differential pressure sensor 12B). The amount of primary fuel F1 may be controlled to be supplied by changing the amount. That is, the operation amount of the governor is set in association with the supply amount (differential pressure) of the air A, and the governor is operated according to the supply amount of the air A to supply the primary fuel F1 of the target supply amount. May be. The proportion of oxygen contained in the combustion gas refers to the proportion of oxygen contained in the combustion gas with respect to the total quantity of the combustion gas. Further, the combustion gas after the combustion of the primary fuel F1 refers to the combustion gas in the state where the combustion reaction of the primary fuel F1 is completed, and the state where the combustion reaction of the primary fuel F1 is completed and the secondary fuel F2 is supplied. It can be said that it refers to the combustion gas in the state where it is not. It should be noted that the combustion reaction may continue even though it is extremely small in the above-mentioned "combustion gas in a state where the combustion reaction is completed". Therefore, "combustion reaction completion" means 100% of the combustion reaction. In some cases, that is, it does not mean that the combustion is completed. In addition, it can be said that the target supply amount of the primary fuel F1 is set so that the air ratio in the mixed gas F1A becomes a predetermined value. In this case, the air ratio in the first combustion stage is preferably 1.4 or more and 2.0 or less, and the air ratio in the second combustion stage is 1.2 or more and 1.7 or less. Is preferred. The target supply amount of the primary fuel F1 is not limited to the above description and may be calculated by any method.

The primary fuel control unit 96 controls the primary fuel supply unit 22 so that the target supply amount of the primary fuel F1 calculated in this way is supplied. Specifically, the primary fuel control unit 96 controls the opening degree of the primary fuel adjusting valve 62 to supply the calculated amount of the primary fuel F1 to the can body 10. In the present embodiment, the primary fuel control unit 96 acquires information on the differential pressure of the primary fuel F1 between the upstream side and the downstream side of the pressure reducing member 64 from the fuel differential pressure sensor 66, and based on this differential pressure information, actually Alternatively, the amount of the primary fuel F1 supplied to the can body 10 may be acquired. In this case, the primary fuel control unit 96 adjusts the opening degree of the primary fuel adjustment valve 62 so that the actually supplied amount of the primary fuel F1 becomes the target supply amount. The primary fuel control unit 96 is not limited to adjusting the opening degree of the primary fuel adjustment valve 62 when controlling the supply amount of the primary fuel F1. For example, the primary fuel control unit 96 may control the supply amount of the primary fuel F1 by a mechanical governor provided in the fuel supply line 60, or may use both the governor and the primary fuel regulating valve 62. The supply amount of the primary fuel F1 may be controlled.

The secondary fuel control unit 98 calculates the supply amount of the secondary fuel F2 supplied to the can body 10, and controls the supply amount of the secondary fuel F2 supplied to the can body 10 so that the calculated supply amount is obtained. Specifically, the secondary fuel control unit 98 acquires information on the differential pressure of the primary fuel F1 between the upstream side and the downstream side of the pressure reducing member 64 from the fuel differential pressure sensor 66, and based on the acquired differential pressure information. , The supply amount of the primary fuel F1 to the can body 10 is acquired. Further, the secondary fuel control unit 98 may acquire information on the supply amount of the primary fuel F1 from the primary fuel control unit 96. Then, in the present embodiment, information indicating the relationship between the amount of the primary fuel F1 and the amount of the secondary fuel F2 is stored in the storage unit 92. The secondary fuel control unit 98 reads the information indicating the relationship between the amount of the primary fuel F1 and the amount of the secondary fuel F2 from the storage unit 92 in the second combustion stage, and the acquired supply amount of the primary fuel F1 is related to this. The target supply amount of the secondary fuel F2 is calculated by substituting into The target supply amount of the secondary fuel F2 is set so that the proportion of oxygen contained in the combustion gas after combustion of the secondary fuel F2 is, for example, 2% or more and 6% or less, preferably about 4%. , Has been set. The combustion gas after combustion of the secondary fuel F2 refers to the combustion gas in a state where the combustion reaction of the secondary fuel F2 is completed. Furthermore, in other words, the combustion gas after the combustion of the secondary fuel F2 may be rephrased as the combustion gas in a state where the combustion reactions of both the primary fuel F1 and the secondary fuel F2 have been completed. It may be said that the combustion gas is exhaust gas (exhaust gas). It can also be said that the target supply amount of the secondary fuel F2 is set so that the air ratio when the mixed gas F1A and the mixed gas F2A are summed is a predetermined value. In this case, the air ratio is preferably 1.1 or more and 1.4 or less. The target supply amount of the secondary fuel F2 is not limited to the above description and may be calculated by any method.

In this way, the target supply amount of the secondary fuel F2 is set according to the supply amount of the primary fuel F1. When the supply amount of the primary fuel F1 is adjusted by the information on the pressure difference from the fuel pressure difference sensor 66, the supply of the secondary fuel F2 is also appropriately performed according to the supply amount of the primary fuel F1. However, the method of calculating the target supply amount of the secondary fuel F2 is not limited to this. For example, an oxygen concentration sensor is provided in the exhaust stack 18, and the secondary fuel control unit 98 detects the secondary fuel F2 according to the detection result of the oxygen concentration contained in the combustion gas in the exhaust stack 18 by the oxygen concentration sensor. The target supply amount of the secondary fuel F2 may be set so that the ratio of oxygen contained in the combustion gas after combustion becomes a predetermined ratio.

The secondary fuel control unit 98 controls the secondary fuel supply unit 24 so that the target supply amount of the secondary fuel F2 calculated in this way is supplied. Specifically, the secondary fuel control unit 98 controls the opening degree of the secondary fuel adjustment valve 72 to supply the calculated amount of the secondary fuel F2 to the can body 10. The secondary fuel control unit 98 is not limited to adjusting the opening degree of the secondary fuel adjustment valve 72 when controlling the supply amount of the secondary fuel F2. For example, the secondary fuel control unit 98 may control the supply amount of the secondary fuel F2 by a mechanical governor provided in the secondary fuel supply line 70, or the governor and the secondary fuel control valve 72. Both may be used to control the supply amount of the secondary fuel F2.

The supply amount of the secondary fuel F2 is proportional to the supply amount of the primary fuel F1. However, the supply amount of the secondary fuel F2 in the first combustion stage is an amount capable of consuming about 8% of oxygen contained in the combustion gas to about 4% by combustion, and the secondary fuel F2 in the second combustion stage is consumed. The supply amount of F2 is an amount at which oxygen contained in the combustion gas at about 6% can be consumed up to about 4% by combustion. Therefore, the ratio of the supply amount of the secondary fuel F2 to the supply amount of the primary fuel F1 in the second combustion stage is smaller than the ratio of the supply amount of the secondary fuel F2 to the supply amount of the primary fuel F1 in the first combustion stage. Become.

In the first combustion stage, the combustion gas control unit 99 connects the secondary exhaust line 84 and the secondary fuel supply line 74 and disconnects the primary exhaust line 82 and the blower 12 from each other, so that the secondary Combustion gas G0 is supplied from the fuel supply line 74 into the can 10. Further, the combustion gas control unit 99 controls the flow rate adjustment unit 81 to change the amount of the combustion gas G0 supplied into the can body 10 according to the supply amount of the secondary fuel F2. In the second combustion stage, the combustion gas control unit 99 connects the secondary exhaust line 84 and the secondary fuel supply line 74, and also connects the primary exhaust line 82 and the blower 12 to the burner 16. Also, the combustion gas G0 is supplied from the secondary fuel supply line 74 into the can body 10. Further, the combustion gas control unit 99 controls the opening degrees of the flow rate adjusting section 81, the primary fuel adjusting valve 62, and the secondary fuel adjusting valve 72 in the second combustion stage, so that the primary fuels F1 and The amount of the combustion gas G0 supplied from the burner 16 into the can body 10 and the amount of the combustion gas G0 supplied from the secondary fuel supply line 74 into the can body 10 are changed according to the supply amount of the next fuel F2. Let

Specifically, in the first combustion stage, the combustion gas control unit 99 controls the secondary fuel supply line so that the combustion temperature in the can body 10, that is, the maximum temperature due to combustion is equal to or less than a predetermined value, for example, 1200° C. or less. The amount of the combustion gas G0 supplied from 74 to the inside of the can body 10, that is, the amount of the combustion gas G0 mixed with the secondary fuel F2 is calculated. For example, in the present embodiment, the storage unit 92 stores information indicating the relationship between the amount of the secondary fuel F2 and the amount of the combustion gas G0 such that the combustion temperature in the can body 10 is equal to or lower than the predetermined value. There is. The combustion gas control unit 99 reads this information from the storage unit 92, and substitutes the supply amount of the secondary fuel F2 to the can body 10 into this relationship to calculate the supply amount of the combustion gas G0. The combustion gas control unit 99 supplies the calculated flow rate of the combustion gas G0 to the can body 10 from the secondary fuel supply line 74.

In the second combustion stage, the combustion gas control unit 99 controls the amount of the combustion gas G0 supplied from the burner 16 into the can body 10, that is, the primary fuel F1 of the combustion gas G0 so as to be proportional to the supply amount of the primary fuel F1. Calculate the mixing amount to The combustion gas control unit 99 increases the supply amount of the combustion gas G0 from the burner 16 as the supply amount of the primary fuel F1 increases. More specifically, the combustion gas control unit 99 linearly increases the supply amount of the combustion gas G0 from the burner 16 as the supply amount of the primary fuel F1 linearly increases. That is, the rate at which the flow rate of the combustion gas G0 from the burner 16 increases when the supply amount of the primary fuel F1 increases is substantially constant. For example, in the present embodiment, information indicating the relationship between the amount of primary fuel F1 and the amount of combustion gas G0 is stored in the storage unit 92. The combustion gas control unit 99 reads this information from the storage unit 92 and substitutes the supply amount of the primary fuel F1 into this relationship to calculate the supply amount of the combustion gas G0. The combustion gas control unit 99 causes the burner 16 to supply the calculated flow rate of the combustion gas G0 to the can body 10.

In addition, the combustion gas control unit 99 uses the secondary fuel supply line 74 so that the combustion temperature in the can body 10, that is, the maximum temperature due to combustion becomes equal to or less than a predetermined value, for example, 1200° C. or less in the second combustion stage. The amount of the combustion gas G0 supplied into the body 10, that is, the amount of the combustion gas G0 mixed with the secondary fuel F2 is calculated. For example, in the present embodiment, the storage unit 92 stores information indicating the relationship between the amount of the secondary fuel F2 and the amount of the combustion gas G0 such that the combustion temperature in the can body 10 is equal to or lower than the predetermined value. There is. The combustion gas control unit 99 reads this information from the storage unit 92, and substitutes the supply amount of the secondary fuel F2 to the can body 10 into this relationship to calculate the supply amount of the combustion gas G0. The combustion gas control unit 99 supplies the calculated flow rate of the combustion gas G0 to the can body 10 from the secondary fuel supply line 74.

Here, the combustion temperature in the can 10 depends on the combustion amount, that is, the supply amount of the primary fuel F1, the secondary fuel F2, and the air A, but the supply amount of the secondary fuel F2 is the supply amount of the primary fuel F1. The supply amount of the primary fuel F1 is calculated based on the supply amount of the air A. That is, the supply amounts of the primary fuel F1, the secondary fuel F2, and the air A are related to each other. Therefore, it may be said that the combustion gas control unit 99 calculates the amount of the combustion gas G0 supplied from the secondary fuel supply line 74 into the can body 10 based on the supply amount of the primary fuel F1.

Thus, the combustion gas control unit 99 calculates the supply amount of the combustion gas G0 from the burner 16 into the can body 10 based on the supply amount of the primary fuel F1 and the secondary fuel based on the supply amount of the secondary fuel F2. The supply amount of the combustion gas G0 from the supply line 74 into the can body 10 is calculated. However, the method of calculating the supply amount of the combustion gas G0 to the can body 10 is not limited to this. For example, the combustion gas control unit 99 may calculate the supply amount of the combustion gas G0 to the can body 10 based on the supply amount of either the primary fuel F1 or the secondary fuel F2, or the air to the duct 14. The supply amount of the combustion gas G0 to the can body 10 may be calculated based on the supply amount of A, or the supply amount of the combustion gas G0 to the can body 10 based on the combustion stage instructed to the boiler 1. May be calculated. In this case, for example, the combustion gas control unit 99 shows information indicating the relationship between the amount of the primary fuel F1 or the secondary fuel F2 and the amount of the combustion gas G0, and the relationship between the amount of the air A and the amount of the combustion gas G0. Information or information indicating the relationship between the combustion stage and the amount of combustion gas G0 is stored in the storage unit 92. The combustion gas control unit 99 reads this information from the storage unit 92, and substitutes the supply amount of the primary fuel F1 or the secondary fuel F2, the supply amount of the air A, or the combustion stage into this relationship, whereby the combustion gas G0 Calculate the supply. Further, the boiler 1 may be provided with a nitrogen oxide concentration sensor in the exhaust stack 18, and calculate the supply amount of the combustion gas G0 to the can body 10 based on the detection result of the nitrogen oxide concentration sensor. In this case, the combustion gas control unit 99 acquires information on the nitrogen oxide concentration of the combustion gas G0 inside the exhaust stack 18 detected by the nitrogen oxide concentration sensor. Then, the combustion gas control unit 99 calculates the flow rate of the combustion gas G0 from which the nitrogen oxide content falls within a predetermined range based on the acquired nitrogen oxide concentration. The combustion gas control unit 99 supplies the calculated amount of the combustion gas G0 to the can body 10.

The control device 30 is configured as described above. Next, a flow of a method for supplying fuel and the like by the control device 30 will be described based on a flowchart. FIG. 6 is a flowchart illustrating the control flow of the control unit according to this embodiment. As shown in FIG. 6, first, the control unit 90 determines whether or not it is the first combustion stage (step S10). The control unit 90 determines whether it is the first combustion stage, for example, according to the designated combustion stage. In the case of the first combustion stage (step S10; Yes), the control unit 90 calculates the supply amount of the air A by the air control unit 94, and adjusts the blowing amount so that the calculated amount of the air A is supplied. Control (step S12). Then, the control unit 90 calculates the supply amount of the primary fuel F1 based on the supply amount of the air A by the primary fuel control unit 96 and supplies the calculated amount of the primary fuel F1 to the primary fuel adjustment valve 62. Is controlled (step S14). Then, the control unit 90 causes the secondary fuel control unit 98 to calculate the supply amount of the secondary fuel F2 based on the supply amount of the primary fuel F1, and to supply the calculated amount of the secondary fuel F2. The next fuel adjustment valve 72 is controlled (step S16). Then, the control unit 90 causes the combustion gas control unit 99 to calculate the supply amount of the combustion gas G0 based on the supply amount of the secondary fuel F2, and opens the secondary connection valve 88 to control the flow rate adjustment unit 81. The calculated amount of combustion gas G0 is supplied to the secondary fuel supply unit 24 (secondary fuel supply line 74) (step S18). As a result, in the first combustion stage, the control device 30 supplies the mixed gas F1A of the primary fuel F1 and the air A from the burner 16 into the can body 10, and the mixed gas F2 of the secondary fuel F2 and the combustion gas G0. F2A is supplied into the can body 10 from the secondary fuel supply line 74.

When it is not the first combustion stage (step S10; No), that is, when it is the second combustion stage, the control unit 90 calculates the supply amount of the air A by the air control unit 94, and supplies the calculated amount of the air A. As described above, the air flow rate is controlled (step S20). Then, the control unit 90 calculates the supply amount of the primary fuel F1 based on the supply amount of the air A by the primary fuel control unit 96 and supplies the calculated amount of the primary fuel F1 to the primary fuel adjustment valve 62. Is controlled (step S22). Then, the control unit 90 causes the secondary fuel control unit 98 to calculate the supply amount of the secondary fuel F2 based on the supply amount of the primary fuel F1, and to supply the calculated amount of the secondary fuel F2. The next fuel adjustment valve 72 is controlled (step S24). Then, the control unit 90 causes the combustion gas control unit 99 to calculate the supply amount of the combustion gas G0 based on the supply amounts of the primary fuel F1 and the secondary fuel F2, and opens the primary connection valve 86 and the secondary connection valve 88. By controlling the flow rate adjusting unit 81, the calculated amount of the combustion gas G0 is supplied to the blower 12 and the secondary fuel supply unit 24 (secondary fuel supply line 74) (step S26). That is, the combustion gas control unit 99 calculates the amount of the combustion gas G0 to be supplied to the blower 12 based on the supply amount of the primary fuel F1 and supplies it to the secondary fuel supply line 74 based on the supply amount of the secondary fuel F2. The amount of combustion gas G0 is calculated. Then, the combustion gas control unit 99 controls the opening degree of the primary connection valve 86 and the secondary connection valve 88 and the flow rate adjustment unit 81 to calculate for the blower 12 and the secondary fuel supply line 74, respectively. A quantity of combustion gas G0 is supplied. Accordingly, the control device 30 supplies the mixed gas F1A of the primary fuel F1, the air A, and the combustion gas G0 from the burner 16 into the can body 10 in the second combustion stage. Then, the control device 30 supplies the mixed gas F2A of the secondary fuel F2 and the combustion gas G0 into the can body 10 from the secondary fuel supply line 74 in the second combustion stage.

In the description of FIG. 6, the detection of the combustion stage, the supply control of the air A based on the combustion stage, the supply control of the primary fuel F1 based on the supply amount of the air A, and the secondary fuel F2 based on the supply amount of the primary fuel F1. The supply control and the supply control of the combustion gas G0 based on the supply amounts of the primary fuel F1 and the secondary fuel F2 are performed in this order. However, each control is not limited to be performed in this order. For example, the control device 30 includes information (table) indicating the relationship between the combustion stage and the supply amount of the air A, information indicating the relationship between the combustion stage and the supply amount of the primary fuel F1, and the combustion stage and the supply of the secondary fuel F2. Information indicating the relationship between the amounts and the information indicating the relationship between the combustion stage and the supply amount of the combustion gas G0 may be stored in the storage unit 92 in advance. In this case, the control device 30 reads these pieces of information, and from the combustion stage instructed to the boiler 1, the supply amount of the air A, the supply amount of the primary fuel F1, the supply amount of the secondary fuel F2, and the combustion gas. The supply amount of G0 is calculated, and the air A, the primary fuel F1, the secondary fuel F2, and the combustion gas G0 are supplied so that the calculated supply amount is obtained. After performing the supply control in this way, the control device 30 controls the supply of the primary fuel F1 based on the supply amount of the air A and the supply control of the secondary fuel F2 based on the supply amount of the primary fuel F1 as described above. The supply amount of the combustion gas G0 may be controlled based on the supply amounts of the primary fuel F1 and the secondary fuel F2 to finely adjust the supply amount. Further, in the present embodiment, the combustion gas control unit 99 controls the flow rate adjustment unit 81 to control the supply amount of the combustion gas G0. However, the combustion gas control unit 99 is not limited to the control of the supply amount of the combustion gas G0 by the flow rate adjustment unit 81. For example, the combustion gas control unit 99 keeps the suction amount of the combustion gas G0 by the flow rate adjusting unit 81 constant and adjusts the opening amounts of the primary connection valve 86 and the secondary connection valve 88 to supply the combustion gas G0. May be controlled.

As described above, the boiler 1 according to the present embodiment includes the can body 10 having the water pipes 51, 52, 53, the burner 16, the secondary fuel supply unit 24, the discharge line 26, and the control unit 90. Have. The burner 16 is connected to the can body 10 and can supply the primary fuel F1 and the air A into the can body 10. The secondary fuel supply unit 24 can supply the secondary fuel F2 into the can body 10 on the downstream side of the burner 16 in the flow direction of the combustion gas. The combustion gas G0 discharged from the inside of the can 10 flows through the discharge line 26. The control unit 90 controls the connection state between the discharge line 26 and the burner 16, the connection state between the discharge line 26 and the secondary fuel supply unit 24, the supply of the primary fuel F1, and the supply of the secondary fuel F2. In the first combustion stage, the control unit 90 connects the exhaust line 26 and the secondary fuel supply unit 24 while supplying the primary fuel F1 to the burner 16, so that the combustion gas G0 from the exhaust line 26 is connected. The mixed gas F2A in which the secondary fuel F2 from the secondary fuel supply unit 24 is mixed is supplied into the can body 10. The control unit 90 connects the exhaust line 26 and the burner 16 in the second combustion stage in which the amount of combustion in the can 10 is larger than that in the first combustion stage, so that the combustion gas G0 from the exhaust line 26 becomes By supplying the mixed gas F1A mixed with the primary fuel F1 from the burner 16 into the can body 10 and connecting the discharge line 26 and the secondary fuel supply unit 24, the combustion gas G0 from the discharge line 26 is connected. And the mixed gas F2A in which the secondary fuel F2 from the secondary fuel supply unit 24 is mixed are supplied into the can body 10.

Here, in order to suppress the generation of CO by self-combusting the secondary fuel F2, it is preferable to keep the temperature at the supply position of the secondary fuel F2 high to some extent. However, if the temperature of the supply position of the secondary fuel F2 is made too high, the combustion temperature of the secondary fuel F2 (the maximum temperature reached by combustion) becomes too high, and the amount of NOx in the combustion gas may increase. .. Therefore, when performing the two-stage combustion, it is preferable to keep the temperature in the can 10 within a predetermined range. On the other hand, the boiler 1 according to the present embodiment mixes the combustion gas G0, that is, the exhaust gas with the secondary fuel F2 in the first combustion stage where the combustion is low, so that EGR (Exhaust Gas Recirculation) is generated from the secondary side. Is going. As a result, the combustion of the secondary fuel F2 can be controlled by the combustion gas G0, the temperature in the can body 10 at the time of low combustion can be maintained in a suitable range, and NOx and CO can be appropriately reduced. Further, the boiler 1 according to the present embodiment mixes the combustion gas G0 with the primary fuel F1 and the secondary fuel F2 in the second combustion stage where the combustion is high, so that the boiler 1 can be discharged from both the primary side and the secondary side. Perform EGR. By mixing the combustion gas G0 with both the primary fuel F1 and the secondary fuel F2, it is possible to supply a sufficient amount of the combustion gas G0 even when the combustion becomes high and the required amount of the combustion gas G0 is large. This makes it possible to maintain the temperature inside the can body 10 in a preferable range at the time of high combustion and appropriately reduce NOx and CO. For example, if the supply position of the secondary fuel F2 is set to the lower limit value of the combustion temperature that can oxidize CO, the amount of the combustion gas G0 that lowers the combustion temperature of the secondary fuel F2 can be reduced, and the flow rate adjustment unit When 81 is a fan, the fan can be downsized.

Further, in order to properly supply the mixed gas F2A of the secondary fuel F2 and the combustion gas G0 into the can body 10, the diameter of the supply port of the secondary fuel supply line 74, that is, the nozzle diameter, is reduced to reduce the mixed gas. It is preferable to secure a sufficient flow velocity of F2A. Therefore, it is necessary to set the nozzle diameter to a small value so as to form a spray even during low combustion when the supply amount of the mixed gas F2A is small. In this case, at the time of high combustion in which the supply amount of the mixed gas F2A is large, the nozzle diameter may be too small and the pressure loss may increase. On the other hand, the boiler 1 according to the present embodiment can suppress the increase in the combustion gas G0 supplied from the secondary side during high combustion by supplying the combustion gas G0 also to the primary fuel F1 during high combustion. .. This reduces the difference between the amount of combustion gas G0 supplied from the secondary side during high combustion and the amount of combustion gas G0 supplied from the secondary side during low combustion, and suppresses pressure loss during high combustion. It becomes possible.

Further, the control unit 90 disconnects the exhaust line 26 and the burner 16 from each other in the first combustion stage, so that the combustion gas G0 from the exhaust line 26 and the primary fuel F1 from the burner 16 are separated from each other. Stop mixing. The boiler 1 performs EGR from only the secondary side in the first combustion stage, and performs EGR from both the primary side and the secondary side in the second combustion stage. Therefore, the boiler 1 can appropriately reduce NOx and CO both during low combustion and during high combustion.

Further, in the second combustion stage, the control unit 90 increases the mixing amount of the combustion gas G0 into the primary fuel F1 as the supply amount of the primary fuel F1 increases. This boiler 1 suitably suppresses the combustion temperature of the primary fuel F1 from becoming too high by increasing the mixing amount of the combustion gas G0 into the primary fuel F1 as the supply amount of the primary fuel F1 increases. NOx and CO can be reduced appropriately.

DESCRIPTION OF SYMBOLS 1... Boiler, 10... Can body, 12... Blower, 12a... Suction port, 12A... Decompression member, 12B... Air differential pressure sensor, 14... Duct, 16... Burner, 18... Exhaust pipe, 20... Fuel supply section, 22 ... primary fuel supply part, 24... secondary fuel supply part, 26... discharge line, 30... control device, 40... body part, 42... upper header, 44... lower header, 50... water pipe group, 51, 52, 53... Water pipe, 54... Connection wall, 60... Fuel supply line, 62... Primary fuel adjustment valve, 64... Pressure reducing member, 66... Fuel differential pressure sensor, 70, 74... Secondary fuel supply line, 72... Secondary fuel adjustment valve, 80... Discharge line, 81... Flow rate adjusting part, 82... Primary discharge line, 84... Secondary discharge line, 86... Primary connection valve, 88... Secondary connection valve, 90... Control part, 92... Storage part, 94... Air Control unit, 96... Primary fuel control unit, 98... Secondary fuel control unit, 99... Combustion gas control unit, A... Air, F... Fuel, F1... Primary fuel, F1A, F2A... Mixed gas, F2... Secondary fuel , G0... Combustion gas, S... Combustion promotion space.

Claims (4)

A can body having a water pipe,
A burner connected to the can body and capable of supplying primary fuel and air into the can body,
A secondary fuel supply unit capable of supplying a secondary fuel into the can body on the downstream side of the burner in the flow direction of combustion gas,
An exhaust line through which the combustion gas exhausted from the can body flows,
A connection state between the discharge line and the burner, a connection state between the discharge line and the secondary fuel supply unit, a supply of the primary fuel, and a control unit for controlling the supply of the secondary fuel,
The control unit is
In the first combustion stage, the burner is supplied with the primary fuel and the exhaust line and the secondary fuel supply unit are connected to each other, whereby the combustion gas and the secondary fuel from the exhaust line are connected. Supplying a mixed gas obtained by mixing the secondary fuel from the supply unit into the can body,
When the combustion amount in the can is the second combustion stage which is larger than the first combustion stage, by connecting the discharge line and the burner, the combustion gas from the discharge line and the burner from the burner are connected. The combustion gas from the discharge line and the secondary fuel are connected by connecting the discharge line and the secondary fuel supply unit while supplying the mixed gas mixed with the primary fuel into the can. A mixed gas obtained by mixing the secondary fuel from the supply unit is supplied into the can body.
boiler. When the control unit is in the first combustion stage, the control unit disconnects the exhaust line and the burner to mix the combustion gas from the exhaust line with the primary fuel from the burner. To stop the
The boiler according to claim 1. In the second combustion stage, the control unit increases the mixing amount of the combustion gas with the primary fuel as the supply amount of the primary fuel increases.
The boiler according to claim 1 or 2. A can body having a water pipe, a burner connected to the can body and capable of supplying primary fuel and air into the can body, and a secondary body in the can body on the downstream side of the burner in the flow direction of combustion gas. A method for controlling a boiler having a secondary fuel supply unit capable of supplying fuel, and an exhaust line through which combustion gas exhausted from the inside of the can flows,
In the first combustion stage, the burner is supplied with the primary fuel and the exhaust line and the secondary fuel supply unit are connected to each other, whereby the combustion gas and the secondary fuel from the exhaust line are connected. Supplying a mixed gas obtained by mixing the secondary fuel from the supply unit into the can body,
When the combustion amount in the can is the second combustion stage which is larger than the first combustion stage, by connecting the discharge line and the burner, the combustion gas from the discharge line and the burner from the burner are connected. The combustion gas from the discharge line and the secondary fuel are connected by connecting the discharge line and the secondary fuel supply unit while supplying the mixed gas mixed with the primary fuel into the can. A mixed gas obtained by mixing the secondary fuel from the supply unit is supplied into the can body.
Boiler control method.

Images