JP2004205129A - Combustion control method for boiler and its device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize the combustion of an igniting burner by further improving the load follow-up performance of a boiler and further reducing the heat loss during stopping a main burner. <P>SOLUTION: This combustion control method for the boiler 1 having the main burner 4, the igniting burner 5 for the main burner 4 and a blower 6 for supplying combustion air to the burners 4, 5 for regulating the combustion amount of the main burner 4 depending on a load comprises operating the igniting burner 5 during stopping the main burner 4 and operating the blower 6 in a blowing amount less than a blowing amount corresponding to the minimum combustion amount of the main burner 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a boiler combustion control method and apparatus.
[0002]
[Prior art]
Usually, in the boiler combustion control method, the combustion and stop of the main burner are controlled based on the steam pressure in the boiler can. That is, when the vapor pressure in the can exceeds a set value, the main burner is stopped, and when the steam pressure falls below the set value, combustion is performed. When starting the combustion of the main burner, a pre-purge for purging the inside of the boiler is performed. Also, depending on the boiler, post-purge for purging the inside of the boiler is performed even when the main burner is stopped.
[0003]
Therefore, in order to restart the combustion after the main burner is once stopped, it is necessary to perform at least a pre-purge. The time required for post-purging is required. Therefore, in a state where the steam-consuming device consumes a larger amount of steam than usual, there is a problem that the load cannot follow the load due to a time delay caused by performing the pre-purge or the post-purge. In addition, since the heat in the boiler is discharged by performing the pre-purge and the post-purge, there is a problem that the heat loss increases and the efficiency of the boiler decreases.
[0004]
Therefore, the following combustion control method has been proposed in order to solve the problem that the boiler is capable of following the load (hereinafter referred to as “load following”) and the problem that the efficiency of the boiler is reduced. That is, after the main burner is stopped by the load, the boiler stands by while performing the post-purge with the blowing amount smaller than the blowing amount at the time of the minimum combustion amount. This is a combustion control method for starting combustion of a burner (for example, see Patent Document 1). However, in this combustion control method, if the post-purge is not continued for a predetermined time or more and the scavenging of the inside of the boiler is not completed, it is necessary to start the combustion of the main burner after performing the pre-purge. Therefore, in this combustion control method, there has been a problem in improving the ability to follow a load request (hereinafter, referred to as “load following ability”).
[0005]
In addition, the following combustion control method has been proposed to solve the problems of load following and efficiency reduction as described above. That is, after the main burner is stopped, a small-volume burner for ignition to the main burner (hereinafter, referred to as “ignition burner”) is continuously operated in accordance with the load on the boiler. This is a control method (for example, see Patent Document 2). However, in this combustion control method, since the combustion air is supplied to the ignition burner even when the main burner is stopped, it is necessary to operate the blower with the air volume at the time of combustion of the main burner. Therefore, in this combustion control method, more combustion air than is required by the ignition burner is supplied, and as a result, heat in the boiler is discharged, so that heat loss increases and the boiler However, there is a problem that the efficiency of the method is reduced.
[0006]
[Patent Document 1]
JP 10-169904 A [Patent Document 2]
JP-A-5-231640
[Problems to be solved by the invention]
The problem to be solved by the present invention is to further improve the load following capability of the boiler, further reduce the heat loss when the main burner is stopped, and achieve stable combustion of the ignition burner.
[0008]
[Means for Solving the Problems]
The present invention has been made to solve the above-mentioned problem, and the invention according to claim 1 includes a main burner, an ignition burner for the main burner, and a blower for supplying combustion air to each of the burners, In the boiler combustion control method for adjusting a combustion amount of the main burner in accordance with a load, the ignition burner is operated while the main burner is stopped, and the blower is operated at a minimum combustion amount of the main burner. It is characterized in that it is operated with a smaller air flow than that.
[0009]
According to a second aspect of the present invention, there is provided a main burner, an ignition burner for the main burner, a blower for supplying combustion air to each of the burners, a first air flow path from the blower to the main burner and the blower from the blower. A combustion control method for a boiler comprising a second air flow path to an ignition burner and adjusting a combustion amount of the main burner according to a load, wherein the ignition burner is operated while the main burner is stopped. It is characterized in that the blower is operated with a blowing amount smaller than the blowing amount of the main burner at the time of the minimum burning amount, thereby narrowing the first air flow path.
[0010]
Furthermore, the invention according to claim 3 provides a main burner, an ignition burner for the main burner, a blower for supplying combustion air to each of the burners, and a supply of combustion air from the blower to the main burner. A first air flow path, a second air flow path for supplying combustion air from the blower to the ignition burner, a throttling means provided in the first air flow path, and a blower amount adjusting means for the blower; When the main burner is stopped, the blower is operated by the blower amount adjusting means at a blower amount smaller than the blown amount of the main burner at the time of the minimum combustion amount, and the ignition burner is operated, and the throttle means is moved. Control means for operating the first air flow path so as to restrict the first air flow path.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described. The present invention can be suitably implemented in a boiler including a main burner, an ignition burner for the main burner, and a blower for supplying combustion air to each of the burners, and adjusting a combustion amount of the main burner according to a load. it can. Further, the present invention can be suitably implemented particularly in a boiler provided with a first air flow path from the blower to the main burner and a second air flow path from the blower to the ignition burner. Here, the boiler includes a boiler such as a steam boiler, a hot water boiler, and a waste heat boiler, as well as a water heater, a reheater of an absorption refrigerator, and the like. In the boiler to which the present invention is applied, the minimum combustion amount of the main burner is larger than the ignition burner combustion amount. Further, the adjustment of the combustion amount of the main burner may be performed continuously between the maximum combustion amount and the minimum combustion amount, or may be performed stepwise. When the adjustment of the combustion amount of the main burner is performed in a stepwise manner, the main burner is provided with a two-position type combustion control for adjusting the combustion amount in two stages of combustion and stop, and a three-stage control of high combustion, low combustion and stop. Multi-position combustion control such as three-position combustion control for adjusting the combustion amount in stages is performed.
[0012]
First, in the first embodiment of the combustion control method of the present invention, while the main burner is stopped, the ignition burner is operated, and the blower is supplied with a smaller amount of air than the minimum burn amount of the main burner. This is a combustion control method operated by the air flow. That is, after the operation of the boiler is started, when the main burner is stopped according to the load of the boiler (that is, when the main burner is in a standby state), the ignition burner is set to an operating state, and Then, the air flow rate of the blower is adjusted to an air flow rate smaller than the air flow rate of the main burner at the time of the minimum combustion amount (hereinafter, referred to as "standby air flow rate"), and this state is maintained.
[0013]
Here, the ignition burner may be ignited when the boiler is started to operate, when the main burner is first burned, and thereafter, may be operated regardless of whether the main burner is burning or stopped. it can. In addition, the term "minimum combustion amount of the main burner" means the minimum combustion amount in terms of combustion control of the main burner. For example, when the main burner is a three-position control type combustion control, the minimum combustion amount is the combustion amount at the time of the low combustion.
[0014]
According to the first embodiment, by operating the ignition burner while the main burner is stopped, the state in which the respective burners are not stopped at the same time is eliminated, so that it is not necessary to perform a pre-purge or a post-purge. Therefore, when the main burner is burned again, it is possible to immediately ignite from the ignition burner without performing pre-purge or post-purge, and it is possible to improve the load followability of the boiler.
[0015]
Further, according to the first embodiment, while the main burner is stopped, by operating the blower of the blower at the standby blower, heat in the boiler discharged together with combustion air from the boiler is discharged. , The heat loss is reduced, and a decrease in the efficiency of the boiler can be prevented.
[0016]
Next, a second embodiment of the combustion control method of the present invention will be described. The combustion control method according to the second embodiment is suitable for the combustion control method according to the first embodiment when the stability of combustion of the ignition burner is impaired. In the combustion control method according to the second embodiment, while the main burner is stopped, the ignition burner is operated, and the blower is operated at the standby flow rate to narrow the first air flow path. This is a combustion control method.
[0017]
That is, in the second embodiment, in addition to the control contents in the first embodiment, the first air flow path is restricted while the main burner is stopped. Here, narrowing the first air flow path means reducing the flow path cross-sectional area of the first air flow path, and includes closing the first air flow path. Further, when the first air flow path is restricted, the second air flow path is not restricted.
[0018]
Now, in the second embodiment, while the main burner is stopped, the first air flow path is throttled to reduce the amount of combustion air flowing into the first air flow path from the blower, Accordingly, the amount of combustion air flowing from the blower into the second air flow path can be increased. Therefore, even if the blowing amount from the blower is reduced to the standby blowing amount, combustion air of an amount necessary for combustion of the ignition burner can be supplied to the ignition burner. The burner can be stably burned. Therefore, when the main burner is burned again according to the load of the boiler, the main burner can be reliably ignited by the ignition burner, so that the load followability of the boiler can be reliably improved. it can. Further, according to the second embodiment, while the main burner is stopped, the amount of combustion air flowing into the first air flow path is smaller than the standby air flow rate, so that heat loss is further reduced. Can be done.
[0019]
That is, in the second embodiment, by stably burning the ignition burner while the main burner is stopped, the load followability of the boiler can be reliably improved, and the boiler A decrease in thermal efficiency can be reliably suppressed.
[0020]
Next, the combustion control device of the present invention will be described. The combustion control device according to the present invention is characterized in that the main burner, the ignition burner, the blower, the first air flow path, the second air flow path, throttle means provided in the first air flow path, It is provided with a blowing amount adjusting means and a control means. Here, the throttle means is a means for reducing the cross-sectional area of the first air flow path, and specifically, is a known means for reducing the cross-sectional area of the flow path such as a damper. The throttling means can be configured to close the first air flow path depending on the implementation. Further, the blower amount adjusting means is a means for adjusting the number of rotations of the blower to adjust the blower amount from the blower, and specifically includes an inverter device, a voltage regulator and the like.
[0021]
The control unit has a function of operating the blower at the standby air volume while the main burner is stopped, operating the ignition burner, and narrowing the first air flow path by the throttle unit. . This function is stored in the control means as software.
[0022]
In the combustion control device, by operating the ignition burner while the main burner is stopped, the state in which the burners are not stopped at the same time is eliminated, so that it is not necessary to perform a pre-purge or a post-purge. Therefore, when the main burner is burned again, the main burner can be immediately ignited by the ignition burner, and the load followability of the boiler can be improved.
[0023]
Further, in the combustion control device, while the main burner is stopped, the blower is operated at the standby blower by the blower blower, thereby reducing heat loss and suppressing a decrease in efficiency of the boiler. can do. Further, in the combustion control device, while the main burner is stopped, the throttle means narrows the first air flow path, thereby reducing an inflow amount of combustion air from the blower into the first air flow path. The amount of combustion air flowing from the blower into the second air passage can be increased accordingly. Therefore, even if the blowing amount of the blower is reduced to the standby blowing amount, a necessary amount of combustion air for the ignition burner can be supplied to the ignition burner, so that the ignition burner is stabilized. Can be burned. Therefore, when the main burner is burned again in accordance with the load of the boiler, the main burner can be reliably ignited by the ignition burner, so that the load followability of the boiler can be reliably improved. it can. Further, while the main burner is stopped, the amount of combustion air flowing into the first air flow path is smaller than the standby air flow rate, so that heat loss can be further reduced.
[0024]
As described above, according to the combustion control method and apparatus of the present invention, the load followability of the boiler can be further improved, and the heat loss during stoppage of the main burner can be further reduced. Moreover, according to the combustion control method and apparatus of the present invention, the combustion of the ignition burner can be stabilized, so that the load followability of the boiler can be reliably improved.
[0025]
【Example】
Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of an embodiment of the combustion control device of the present invention, and FIG. 2 is a timing chart of the combustion control method of the present invention. Here, the boiler of this embodiment is a steam boiler, and employs a so-called three-position control type combustion control in which the combustion amount of a main burner is controlled at three positions of high combustion, low combustion, and stop.
[0026]
First, the basic configuration of a boiler will be described with reference to FIG. 1, a boiler 1 includes a can body 3 having a large number of heat transfer tubes 2, 2,..., A main burner 4, and a small-capacity burner for igniting the main burner 4 (hereinafter referred to as an "ignition burner"). And a blower 6 for supplying combustion air to each of the burners 4,5.
[0027]
A gas passage 7 for exchanging heat with water in each of the heat transfer tubes 2 while burning fuel gas from the main burner 4 is formed in the can body 3. Therefore, the main burner 4 is provided at one end (the left end in FIG. 1) of the gas passage 7, and the other end (the left end in FIG. 1) of the gas passage 7 is provided with the exhaust gas. Exit 8
[0028]
In this embodiment, the main burner 4 is a completely premixed burner having a planar combustion surface (a surface for ejecting premixed gas). Between the main burner 4 and the blower 6, a first air flow path 9 for supplying combustion air from the blower 6 to the main burner 4 is provided. The first air flow path 9 is provided with a damper 10 as a throttle means for adjusting the flow path cross-sectional area of the first air flow path 9. The damper 10 is controlled to a combustion position A shown by a dotted line in FIG. 1 when the main burner 4 is burning, and is controlled to an ignition position B shown by a solid line in FIG. 1 when the main burner 4 is ignited. Here, when the damper 10 is at the ignition position B, the flow path cross-sectional area of the first air flow path 9 is narrowed as compared with the combustion position A. Further, a first fuel supply line (not shown) for supplying a fuel gas to the main burner 4 is connected to the main burner 4.
[0029]
The ignition burner 5 is provided near the main burner 4. In this embodiment, the main burner 4 is provided on the upper end side of the combustion surface. A second air flow path 11 for supplying combustion air from the blower 6 to the ignition burner 5 is provided between the ignition burner 5 and the blower 6. Further, a second fuel supply line (not shown) for supplying a fuel gas to the ignition burner 5 is connected to the ignition burner 5. Here, the combustion amount of the ignition burner 5 is about 1% to 5% of the combustion amount of the main burner 4.
[0030]
The blower 6 is connected to an inverter device 12 as a blower amount adjusting means. The inverter device 12 is capable of adjusting the frequency of power supplied to the blower 6 and adjusting the number of revolutions of the blower 6 to adjust the amount of blown air.
[0031]
The blower 6, the damper 10, and the inverter device 12 are connected to a controller 14 via a line 13. The controller 14 controls the blower 6, the damper 10, and the inverter device 12 based on the load of the boiler 1, and supplies gas fuel from the fuel supply lines to the burners 4, 5. Is configured to be controlled. These control contents are stored in the controller 14 as software.
[0032]
In the above configuration, the schematic operation of the boiler 1 by the controller 14 is as follows. First, when the boiler 1 is started, the blower 6 is started to perform pre-purge. In this pre-purge operation, the blower 6 is operated at a blow rate corresponding to the high burn rate of the main burner 4 (hereinafter, referred to as “high burn rate”), and the damper 10 is set to the combustion position A. Do.
[0033]
When the main burner 4 is ignited after the end of the prepurge, first, the ignition burner 5 is ignited. The ignition of the ignition burner 5 is performed by supplying the fuel gas to the ignition burner 5 while the damper 10 is moved to the ignition position B while the blower 6 is set to the high combustion air volume. (Not shown). Next, after the ignition burner 5 is ignited, the main burner 4 is ignited by supplying fuel gas to the main burner 4.
[0034]
Then, after a predetermined time has elapsed since the main burner 4 was ignited, the blower 6 is operated at an air flow rate corresponding to the low combustion amount of the main burner 4 (hereinafter, referred to as “low combustion air flow rate”). At the same time, the position of the damper 10 is defined as the combustion position A. Thereafter, while the damper 10 is kept at the combustion position A, the amount of air blown by the blower 6 and the amount of combustion to the main burner 4 are adjusted in accordance with the load of the boiler 1, whereby The main burner 4 is controlled at three positions: high combustion, low combustion, and stop. Here, the main burner 4 restarts combustion in accordance with the load on the boiler 1 even if the main burner 4 is stopped until the operation of the boiler 1 is stopped. That is, the main burner 4 is in a standby state for restarting combustion based on a load request.
[0035]
When the operation of the boiler 1 is terminated, the supply of fuel gas to the burners 4 and 5 is first stopped by operating a stop switch (not shown), and the damper 10 is moved to the combustion position A. In this state, the blower 6 is operated for a predetermined time at the high-combustion air flow rate to perform post-purge.
[0036]
Next, the characteristic portion of this embodiment will be described with reference to FIGS. 1 and 2 together with the control contents of the controller 14. The control content of this characteristic portion is also stored in the controller 14 as software. The contents of this control are as follows: when the main burner 4 is in the standby state, the blower 6 is operated with a smaller air flow than the low combustion air flow (hereinafter referred to as “standby air flow”), and the ignition burner is operated. 5 is operated, and the first air flow path 9 is throttled by the damper 10. The details will be described below.
[0037]
First, in this embodiment, as shown in FIG. 2, after starting the operation of the boiler 1 and igniting the ignition burner 5, the ignition burner 5 is operated regardless of the operation state of the main burner 4 as shown in FIG. Instead, the operation is continued until the operation of the boiler 1 is terminated. Further, as described above, the standby air flow rate is an air flow rate smaller than the low combustion air flow rate.
[0038]
As described above, while the main burner 4 is on standby, the ignition burner 5 is continuously operated, so that the respective burners 4 and 5 are not stopped at the same time, so that it is not necessary to perform pre-purge or post-purge. . Therefore, when the main burner 4 is burned again, the main burner 4 can be ignited immediately by the ignition burner 5, and the load following ability of the boiler 1 can be improved. Also, while the main burner 4 is on standby, by operating the blower 6 at the standby air volume, the heat in the boiler 1 discharged together with the combustion air from the boiler 1 is reduced, so that heat loss is reduced. And the efficiency of the boiler 1 can be prevented from lowering.
[0039]
Further, in this embodiment, while the main burner 4 is on standby, the damper 10 is set at the ignition position B so that the cross-sectional area of the first air flow path 9 is reduced. As described above, if the cross-sectional area of the first air flow path 9 is reduced while the main burner 4 is on standby, the pressure loss on the first air flow path 9 side increases. The amount of combustion air flowing into the air passage 9 decreases, and the amount of combustion air flowing from the blower 6 into the second air passage 11 increases by the amount of the decrease. Therefore, even if the blowing amount of the blower 6 is reduced to the standby blowing amount, the amount of combustion air required for combustion of the ignition burner 5 can be supplied to the ignition burner 5. The ignition burner 5 can be stably burned.
[0040]
Therefore, in this embodiment, when the main burner 4 is burned again in accordance with the load of the boiler 1, the main burner 4 can be reliably ignited by the ignition burner 5, so that the boiler 1 Can reliably improve the load followability. Further, in this embodiment, while the main burner 4 is stopped, the amount of combustion air flowing into the first air flow path 9 is smaller than the standby air volume, so that the heat loss is further reduced. Can be.
[0041]
In this embodiment, when the main burner 4 is on standby, the damper 10 is set to the ignition position B, thereby narrowing the first air passage 9. That is, the present invention is implemented by utilizing the existing configuration of the damper 10. Therefore, when the main burner 4 is on standby, it is not necessary to separately provide a device for restricting the first air passage 9.
[0042]
Here, the amount of air blown from the blower 6 when the main burner 4 is on standby, that is, the amount of air during standby is set as follows. That is, when the first air passage 9 is throttled by the damper 10, the amount of combustion air flowing into the second passage 11 stably burns the ignition burner 5. The amount is set so as to be equal to or slightly larger than the amount of combustion air that can be caused.
[0043]
Here, in this embodiment, when the main air burner 4 is on standby and the first air flow path 9 is throttled by the damper 10, the damper 10 is set to the ignition position B. It is not limited to the example. That is, according to the embodiment, as shown in FIGS. 1 and 2, the first air flow path 9 can be configured to be closed to a closed position (indicated by a two-dot chain line in FIG. 1) C for closing the first air flow path 9. In this case, since the first air flow path 9 is closed, all the combustion air from the blower 6 is supplied to the second air flow path 11, and is discharged from the boiler 1 together with the combustion air. Since the heat in the boiler 1 is further reduced, a decrease in the efficiency of the boiler 1 can be further suppressed. Here, the amount of air blown from the blower 6, that is, the amount of air in standby mode, is set to be equal to or slightly larger than the amount of combustion air that can stably burn the ignition burner 5. I do.
[0044]
【The invention's effect】
According to the present invention, the load following capability of the boiler can be further improved, and the heat loss during stoppage of the burner can be further reduced. Moreover, according to the present invention, the combustion of the ignition burner can be stabilized, so that the load following ability can be surely improved.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of one embodiment of a combustion control device of the present invention.
FIG. 2 is a timing chart of the combustion control method of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Boiler 4 Main burner 5 Burner for ignition 6 Blower 9 First air flow path 10 Damper (throttling means)
11 Second air flow path 12 Inverter device (blowing volume adjusting means)
14 control device (control means)

Claims (3)

A main burner 4, an ignition burner 5 for the main burner 4, and a blower 6 for supplying combustion air to each of the burners 4, 5, the combustion of the boiler 1 for adjusting the amount of combustion of the main burner 4 according to the load. In the control method, while the main burner 4 is stopped, the ignition burner 5 is operated, and the blower 6 is operated with a blowing amount smaller than a blowing amount of the main burner 4 at a minimum combustion amount. Boiler combustion control method. A main burner 4, an ignition burner 5 for the main burner 4, a blower 6 for supplying combustion air to the burners 4, 5, a first air flow path 9 from the blower 6 to the main burner 4, and the blower 6 A combustion control method for the boiler 1 which includes a second air flow path 11 to the ignition burner 5 and adjusts a combustion amount of the main burner 4 according to a load. A combustion control method for the boiler, characterized in that the burner 5 is operated and the blower 6 is operated at a flow rate smaller than the minimum flow rate of the main burner 4 to reduce the first air flow path 9. . A main burner 4, an ignition burner 5 for the main burner 4, a blower 6 for supplying combustion air to each of the burners 4, 5, and a first for supplying combustion air from the blower 6 to the main burner 4. An air flow path 9; a second air flow path 11 for supplying combustion air from the blower 6 to the ignition burner 5; a throttle means 10 provided in the first air flow path 9; While the main burner 4 is stopped, the blower 6 is operated by the blower amount controller 12 with a blower amount smaller than the minimum burner amount of the main burner 4 while the main burner 4 is stopped. Control means for operating the burner 5 and operating the throttle means 10 to throttle the first air flow path 9.

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