JP4554153B2 - Boiler combustion control system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control device for a boiler.
[0002]
[Prior art]
Normally, in the boiler combustion control method, combustion and stop of the main burner are controlled based on the vapor 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 it falls below the set value, combustion is performed. When the combustion of the main burner is started, pre-purge for scavenging the boiler is performed. Further, depending on the boiler, a post-purge for scavenging the inside of the boiler is also performed when the main burner is stopped.
[0003]
Therefore, after the main burner is temporarily stopped, it is necessary to perform at least a pre-purge to start combustion again, and the time required for the pre-purge or the pre-purge from the stop of the main burner to the combustion again. Time required for post-purging is required. Therefore, there is a problem that when a steam-consuming device consumes a larger amount of steam than usual, it becomes impossible to follow the load due to a time delay due to pre-purge or post-purge. Moreover, since heat in the boiler is discharged by performing pre-purge or post-purge, there is a problem that heat loss increases and efficiency of the boiler decreases.
[0004]
Therefore, the following combustion control method has been proposed in order to solve the problem that the followability (hereinafter referred to as “load followability”) of the boiler and the efficiency of the boiler are reduced. That is, after the main burner is stopped due to a load, the main burner is on standby while performing a post-purge with an air flow rate that is smaller than the air flow rate at the minimum combustion amount in the boiler. This is a combustion control method (for example, see Patent Document 1) in which combustion of the burner is started. However, in this combustion control method, when the post-purge is not continued for a predetermined time or more and the scavenging in 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 is a problem in improving the followability to the load request (hereinafter referred to as “load followability”).
[0005]
In order to solve the problems of load followability and efficiency reduction as described above, the following combustion control method has also been proposed. That is, after the main burner is stopped, a combustion with a small capacity burner for ignition to the main burner (hereinafter referred to as “ignition burner”) is continuously operated according to the load on the boiler. This is a control method (see, for example, 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 amount of air blown during the combustion of the main burner. Therefore, in this combustion control method, more combustion air than the ignition burner needs is supplied. As a result, heat in the boiler is discharged, so that heat loss increases and the boiler There is a problem that the efficiency of the system is lowered.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 10-169904 [Patent Document 2]
JP-A-5-231640 Publication
[Problems to be solved by the invention]
The problem to be solved by the present invention is to further improve the load followability of the boiler, to further reduce the heat loss during the stop of the main burner, and to achieve stabilization of combustion of the ignition burner.
[0008]
[Means for Solving the Problems]
This invention was made in order to solve the said subject, and the invention of Claim 1 is a main burner, the ignition burner of this main burner, and the air blower which supplies the combustion air to each said burner A can body having a large number of heat transfer tubes and having a gas passage for performing heat exchange with water in each heat transfer tube while burning fuel gas from the main burner; A first air flow path for supplying combustion air to the burner, a second air flow path for supplying combustion air from the blower to the ignition burner, and a throttle means provided in the first air flow path; While the air flow rate adjusting means of the air blower and the main burner are stopped, the air flow rate adjusting means operates the air blower with an air flow rate smaller than the air flow rate at the time of the minimum combustion amount of the main burner, and the ignition burner Actuating said throttling means Without closing the first air flow path, by operating to reduce the flow path cross-sectional area of the first air flow path, to reduce the air blowing amount to the first air flow path from said blower, Accordingly, there is provided control means for increasing the amount of air blown from the blower to the second air flow path .
[0009]
According to a second aspect of the present invention, in the first aspect, the main burner 4 is a burner that ejects premixed gas.
[0010]
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, an embodiment of the present invention will be described. The present invention is preferably implemented in a boiler that includes a main burner, an ignition burner for the main burner, and a blower that supplies combustion air to the burners, and adjusts the combustion amount of the main burner according to a load. it can. Moreover, this invention can be suitably implemented especially in a boiler having 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, in addition to boilers such as a steam boiler, a hot water boiler, and a waste heat boiler, the boiler includes a water heater, a reheater for an absorption chiller, 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. 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 stages, the main burner has two-position type combustion control that adjusts the combustion amount in two stages of combustion and stop, and high combustion, low combustion, and stop. Multi-position combustion control such as three-position combustion control that adjusts the combustion amount in stages is performed.
[0012]
First, according to a 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 sent less than the amount of air blown at the time of the minimum combustion amount of the main burner. This is a combustion control method that operates with air volume. 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 in an operating state. The air volume of the blower is adjusted to an air volume that is smaller than the air volume at the time of the minimum combustion amount of the main burner (hereinafter referred to as “standby air volume”), and this state is maintained.
[0013]
Here, the ignition burner may be ignited when the main burner is first burned at the start of operation of the boiler, and thereafter operated regardless of whether the main burner is burning or stopped. it can. The minimum combustion amount of the main burner is the smallest amount of combustion 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, it is not necessary to perform pre-purge or post-purge because the burners are not stopped at the same time. Therefore, when the main burner is burned again, it can be ignited immediately from the ignition burner without performing pre-purge or post-purge, and the load followability of the boiler can be improved.
[0015]
Further, according to the first embodiment, when the main burner is stopped, the heat in the boiler is discharged together with the combustion air from the boiler by operating the blower amount of the blower at the standby blow amount. Therefore, the heat loss is reduced and the efficiency of the boiler can be prevented from being lowered.
[0016]
Next, a second embodiment of the combustion control method of the present invention will be described. The combustion control method of the second embodiment is a combustion control suitable for the combustion control method of the first embodiment when a failure occurs in the combustion stability of the ignition burner. In the combustion control method of the second embodiment, while the main burner is stopped, the ignition burner is operated, and the blower is operated at the standby air flow rate so as to restrict the first air flow path. It 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 throttled while the main burner is stopped. Here, the restriction of the first air flow path means that the cross-sectional area of the first air flow path is reduced. Further, when the first air flow path is throttled, the second air flow path is not throttled.
[0018]
Now, in this second embodiment, during the stop of the main burner, by reducing the first air flow path, the amount of combustion air flowing from the blower to the first air flow path is reduced, Accordingly, the inflow amount of combustion air from the blower to the second air flow path can be increased. Therefore, even if the amount of air blown from the blower is reduced to the standby amount of air, the amount of combustion air necessary for combustion of the ignition burner can be supplied to the ignition burner. The burner can be burned stably. 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, thereby further reducing heat loss. Can be made.
[0019]
That is, in this second embodiment, while the main burner is stopped, the ignition burner can be stably burned, so that 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 includes the main burner, the ignition burner, the blower, the first air flow path, the second air flow path, the throttle means provided in the first air flow path, An air flow rate adjusting means and a control means are provided. Here, the throttle means is a means for reducing the cross-sectional area of the first air flow path, and specifically, a known means for reducing the cross-sectional area of the flow path such as a damper. Further, the air flow rate adjusting means is a means for adjusting the air flow rate from the blower by adjusting the rotational speed of the blower, and specifically, an inverter device, a voltage regulator or the like.
[0021]
The control means has a function of operating the blower at the standby air flow rate and operating the ignition burner while the main burner is stopped, and restricting the first air flow path by the throttle means. . This function is stored as software in the control means.
[0022]
In the combustion control device, by operating the ignition burner while the main burner is stopped, the burners 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 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 air flow rate adjusting means operates the blower with the standby air flow rate, thereby reducing heat loss and suppressing reduction in the efficiency of the boiler. can do. Further, in the combustion control device, the amount of combustion air flowing from the blower into the first air passage is reduced by restricting the first air passage by the restricting means while the main burner is stopped. The amount of combustion air flowing from the blower into the second air flow path can be increased accordingly. Therefore, even if the amount of air blown from the blower is reduced to the amount of airflow during standby, the amount of combustion air necessary for the ignition burner can be supplied to the ignition burner, so that the ignition burner can be stabilized. And can be 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, during the stop of the main burner, the inflow amount of the combustion air into the first air flow path becomes 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 the stop 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 a combustion control apparatus 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 the main burner is controlled at three positions of high combustion, low combustion and stop.
[0026]
First, the basic configuration of the 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 “ignition burner”). ) 5 and a blower 6 for supplying combustion air to the burners 4 and 5.
[0027]
A gas passage 7 is formed in the can 3 to exchange heat with water in each heat transfer tube 2 while burning the fuel gas from the main burner 4. 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 an exhaust gas. It is an exit 8.
[0028]
In this embodiment, the main burner 4 is a completely premixed burner having a planar combustion surface (premixed gas ejection surface). 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 cross-sectional area of the first air flow path 9. The damper 10 is controlled to a combustion position A indicated by a dotted line in FIG. 1 when the main burner 4 is combusted, and is controlled to an ignition position B indicated 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 passage cross-sectional area of the first air flow passage 9 is reduced as compared with the combustion position A. The main burner 4 is connected to a first fuel supply line (not shown) for supplying fuel gas to the main burner 4.
[0029]
The ignition burner 5 is provided in the vicinity of the main burner 4. In this embodiment, the main burner 4 is provided on the upper end side of the combustion surface. Between the ignition burner 5 and the blower 6, a second air flow path 11 for supplying combustion air from the blower 6 to the ignition burner 5 is provided. The ignition burner 5 is connected to a second fuel supply line (not shown) for supplying fuel gas 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 blowing amount adjusting means. The inverter device 12 can adjust the air flow rate by adjusting the frequency of power supplied to the blower 6 and adjusting the rotational speed of the blower 6.
[0031]
The blower 6, the damper 10 and the inverter device 12 are each 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 and 5. Is configured to control. These control contents are stored in the controller 14 as software.
[0032]
In the above configuration, the general operation of the boiler 1 by the controller 14 is as follows. First, when the boiler 1 is started, the blower 6 is started and pre-purge is performed. In this pre-purge, the blower 6 is operated with an air flow amount corresponding to a high combustion amount of the main burner 4 (hereinafter referred to as “air flow amount during high combustion”), and the damper 10 is in the combustion position A. Do.
[0033]
When the main burner 4 is ignited after the pre-purge is completed, the ignition burner 5 is first ignited. The ignition burner 5 is ignited by supplying fuel gas to the ignition burner 5 in a state where the blower 6 is at the high combustion air flow rate and the damper 10 is moved to the ignition position B. This is done by operating (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 the main burner 4 is ignited, after a lapse of a predetermined time, the blower 6 is operated with a blowing amount corresponding to a low combustion amount of the main burner 4 (hereinafter referred to as a “low combustion blowing amount”). At the same time, the position of the damper 10 is defined as the combustion position A. And after that, by adjusting the blowing amount of the blower 6 and the burning amount to the main burner 4 according to the load of the boiler 1 while keeping the damper 10 in the combustion position A, The main burner 4 is controlled at three positions of high combustion, low combustion and stop. Here, even if the main burner 4 is in a stopped state until the operation of the boiler 1 is stopped, combustion is resumed in accordance with the load of the boiler 1. That is, the main burner 4 is in a standby state for resuming combustion based on a load request.
[0035]
When the operation of the boiler 1 is terminated, the operation of an operation stop switch (not shown) first stops the supply of fuel gas to the burners 4 and 5, 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 for a post purge.
[0036]
Next, the features of this embodiment will be described together with the control contents of the controller 14 with reference to FIGS. The control content of this characteristic portion is also stored in the controller 14 as software. The contents of this control are such that when the main burner 4 is in a standby state, the blower 6 is operated with an air flow rate smaller than the low combustion air flow rate (hereinafter referred to as “standby air flow rate”) and the ignition burner. 5, and the first air flow path 9 is throttled by the damper 10. Details will be described below.
[0037]
First, in this embodiment, as shown in FIG. 2, the ignition burner 5 starts operation of the boiler 1, and after the ignition burner 5 is ignited, regardless of the operating state of the main burner 4. Instead, it is continuously operated until the operation of the boiler 1 is terminated. Further, as described above, the standby air volume is smaller than the low combustion air volume.
[0038]
Thus, by continuously operating the ignition burner 5 during the standby of the main burner 4, the burners 4 and 5 are not stopped at the same time, so there is no need to perform pre-purge or post-purge. . Therefore, when the main burner 4 is burned again, the main burner 4 can be immediately ignited by the ignition burner 5 and the load followability of the boiler 1 can be improved. Further, when the main burner 4 is on standby, by operating the blower 6 with the standby air flow, heat in the boiler 1 discharged from the boiler 1 together with combustion air is reduced, so heat loss is reduced. It can reduce and the fall of the efficiency of the said boiler 1 can be prevented.
[0039]
In this embodiment, the flow passage cross-sectional area of the first air flow passage 9 is narrowed by setting the damper 10 to the ignition position B while the main burner 4 is on standby. In this manner, when the flow passage cross-sectional area of the first air flow passage 9 is reduced during the standby of the main burner 4, the pressure loss on the first air flow passage 9 side increases. The amount of inflow of combustion air to the air flow path 9 decreases, and the amount of inflow of combustion air from the blower 6 to the second air flow path 11 increases by this decrease. Therefore, even if the amount of air blown by the blower 6 is reduced to the amount of airflow during standby, the amount of combustion air necessary for the combustion of the ignition burner 5 can be supplied to the ignition burner 5, The ignition burner 5 can be combusted stably.
[0040]
Therefore, in this embodiment, the main burner 4 can be reliably ignited by the ignition burner 5 when the main burner 4 is burned again according to the load of the boiler 1. The load followability can be improved with certainty. 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 flow rate, thereby further reducing heat loss. Can do.
[0041]
In this embodiment, the first air flow path 9 is narrowed by setting the damper 10 to the ignition position B when the main burner 4 is on standby. That is, the present invention is implemented using the existing configuration of the damper 10. Therefore, it is not necessary to separately provide a device for restricting the first air flow path 9 when the main burner 4 is on standby.
[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 on standby is set as follows. That is, when the first air flow path 9 is throttled by the damper 10, the standby air flow rate is such that the amount of combustion air flowing into the second flow path 11 stably burns the ignition burner 5. It is set to be equal to or slightly larger than the amount of combustion air that can be generated.
[0043]
Here, in this embodiment, when the first air flow path 9 is throttled by the damper 10 when the main burner 4 is on standby, the damper 10 is set to the ignition position B. It is not limited to examples.
[0044]
【The invention's effect】
According to this invention, while the main burner is stopped, the amount of inflow of combustion air from the blower to the first air flow path is reduced by restricting the first air flow path by the throttle means, and accordingly, from the blower. The amount of combustion air flowing into the second air flow path can be increased. Therefore, even if the blower air amount is reduced by the blower amount adjusting means to the blower amount during the combustion standby of the main burner, the necessary amount of combustion air for the ignition burner can be supplied to the ignition burner. The ignition burner can be combusted stably. Therefore, according to the load of the boiler, when the combustion of the main burner again, it is possible to reliably ignite the main burner by the ignition burner, it is possible to reliably improve the load following capability of the boiler. In addition , during the stop of the main burner , the amount of combustion air flowing into the first air flow path is smaller than the amount of air blown during combustion standby, so heat loss can be further reduced .
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an 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 Ignition burner 6 Blower 9 First air flow path 10 Damper (throttle means)
11 Second air flow path 12 Inverter device (air flow rate adjusting means)
14 Control device (control means)

Claims (2)

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, and a large number of heat transfer tubes 2, 2,. The combustion air is supplied to the main burner 4 from the blower 6 and the can body 3 in which the gas passages 7 for performing heat exchange with the water in the heat transfer tubes 2 are combusted. A first air passage 9 that performs combustion, a second air passage 11 that supplies combustion air from the blower 6 to the ignition burner 5, a throttle means 10 provided in the first air passage 9, While the air flow rate adjusting means 12 of the air blower 6 and the main burner 4 are stopped, the air flow rate adjusting means 12 operates the air blower 6 with an air flow rate smaller than the air flow rate at the time of the minimum combustion amount of the main burner 4, The ignition burner 5 is operated, and the throttle means 10 is Without closing the serial first air passage 9, by operating to reduce the flow path cross-sectional area of the first air passage 9, air blowing amount from the blower 6 into the first air passage 9 And a control means 14 for increasing the amount of air blown from the blower 6 to the second air flow path 11 by that amount .   The boiler combustion control apparatus according to claim 1, wherein the main burner 4 is a burner that ejects premixed gas.

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