JP2010261660A - Combustion control method and control system for boiler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use a flowmeter with relatively low detection accuracy without using a steam accumulator, and preventing increase in steam pressure due to an error of the flowmeter. <P>SOLUTION: This boiler control system includes: one or a plurality of boilers 1 of which combustion amount is adjustable; a flow rate detector 6 for detecting a steam flow rate; and a pressure detector 7 for detecting steam pressure. In this combustion control method for the boiler 1, based on the detected flow rate by the flow rate detector 6, the base combustion amount of the boiler 1 is set, and the base combustion amount is corrected based on the detection pressure by the pressure detector 7. In setting the base combustion amount, based on a detected flow rate obtained by subtracting a set error from the detected flow rate, the base combustion amount is set. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a boiler combustion control method and a control system for controlling the combustion amount of one or more boilers that generate steam.

  This type of general boiler unit control method is provided with steam headers in the steam lines of multiple boilers, and the required number of units according to the load by the pressure detector that can grasp the steam load state provided in this steam header. The boiler is burned.

  However, these conventional number control methods do not detect the absolute amount of necessary steam, but only know the steam pressure, which is a relative value obtained from the difference between the amount of steam generated and the amount of steam consumed, and therefore, there is a rapid fluctuation in steam load. However, there is a problem that smooth follow-up control cannot be performed. In addition, when the number of boilers increases, fine pressure detection is required.

  A number control method that solves this drawback is proposed in Patent Document 1. In this number control method, the number of boilers to be burned is determined by a signal from the steam flow detector, and the amount of combustion by the signal from the pressure detector, that is, the number of boilers that perform high combustion within the determined number of boiler burns, The problem is solved by determining the number of boilers that perform low combustion.

  As is apparent from the description of the embodiment of the specification of Patent Document 1, this number control method is provided with a steam accumulator in the middle of the steam line connecting the steam header and the boiler, that is, a boiler, a flow rate detector and a pressure detector. By installing a steam accumulator in between, it is the first method to be established by detecting the steam flow rate and steam pressure after absorbing rapid fluctuations in steam load and using a flow meter with high detection accuracy. Conceivable. However, since the steam accumulator and the flowmeter with high detection accuracy are very expensive, it is difficult to put the number control method disclosed in Patent Document 1 into practical use.

Japanese Patent No. 2671246

  The inventor of this application has studied the improvement of the number control method of Patent Document 1, that is, the number control method capable of using a flowmeter having a relatively low detection accuracy without using a steam accumulator. I found that there was a problem.

  That is, in a system that does not use a steam accumulator, a large error occurs in the flow rate detected by the flow meter. This error includes a flow meter error, a minute load, a drain amount, and the like. Without considering these errors, if the base combustion amount is set based on the detected flow rate, the steam pressure increases, and the inconvenience caused by the increased steam pressure, that is, the safety valve is activated or abnormal pressure rise is detected. This may cause the system to stop, damage to the steam line, and damage to the equipment that uses steam connected to the steam line.

  The problem to be solved by the present invention is to make it possible to use a flow meter having a relatively low detection accuracy without using a steam accumulator, and to prevent an increase in vapor pressure due to an error in the flow meter. .

  This invention was made in order to solve the said subject, and the invention of Claim 1 is the steam provided in the steam line from the 1 unit | set or several boilers which can adjust combustion quantity, and the said boiler. It is performed in a boiler control system including a flow rate detector for detecting a flow rate and a pressure detector for detecting a steam pressure of the steam line, and sets a base combustion amount of the boiler based on a detected flow rate by the flow rate detector. A boiler combustion control method for correcting the base combustion amount based on the pressure detected by the pressure detector, based on a detected flow rate obtained by subtracting a setting error from the detected flow rate when setting the base combustion amount. The base combustion amount is set.

  According to the first aspect of the present invention, when the base combustion amount is set, the base combustion amount is set based on a detected flow rate obtained by subtracting a setting error from the detected flow rate. Therefore, a steam accumulator is used in the combustion control system. Even if a flowmeter with relatively low detection accuracy is used, the steam pressure can be prevented from increasing due to errors in the flowmeter, and smooth follow-up control can be performed against fluctuations in the steam load. It is possible to provide a boiler combustion control method.

  According to the second aspect of the present invention, one or a plurality of boilers whose combustion amount can be adjusted, a flow rate detector for detecting a steam flow rate provided in a steam line from the boiler, and a steam pressure of the steam line are set. A boiler comprising: a pressure detector to detect; and a controller for setting a base combustion amount of the boiler based on a flow rate detected by the flow rate detector and correcting the base combustion amount based on a pressure detected by the pressure detector. In the control system, when setting the base combustion amount, the controller sets the base combustion amount based on a detected flow rate obtained by subtracting a setting error from the detected flow rate.

  According to the second aspect of the present invention, the controller sets the base combustion amount based on a detected flow rate obtained by subtracting a setting error from the detected flow rate when setting the base combustion amount. Even if a flowmeter with relatively low detection accuracy is used, the steam pressure can be prevented from increasing due to errors in the flowmeter, and smooth follow-up control can be performed against fluctuations in the steam load. Can provide a boiler control system.

  A third aspect of the present invention is characterized in that in the second aspect, a steam accumulator is not provided between the flow rate detector and the pressure detector from the boiler.

  According to the invention described in claim 3, in addition to the effect of the invention described in claim 2, there is an effect that the configuration of the boiler control system can be simplified and can be provided at low cost.

  According to the present invention, it is possible to use a flow meter that does not use a steam accumulator and has a relatively low detection accuracy, and it is possible to prevent an increase in vapor pressure due to an error in the flow meter.

It is a schematic block diagram of Example 1 of the number control system which implemented this invention. It is a figure explaining the base combustion number setting with respect to the detected steam flow rate of the Example 1. FIG. It is a flowchart figure which shows the number control method of the Example 1. FIG. It is a schematic block diagram of other Example 2 of this invention. It is a schematic block diagram of other Example 3 of this invention.

  Next, an embodiment of the system of the present invention will be described. This embodiment is applied to a boiler control system that controls combustion of a steam boiler.

  The boiler control system of this embodiment includes one or a plurality of boilers whose combustion amount can be adjusted, a flow rate detector for detecting a steam flow rate provided in a steam line from the boiler, and a steam pressure of the steam line. And a controller for controlling combustion of the boiler. The controller has a function of setting the base combustion amount of the boiler based on the flow rate detected by the flow rate detector and correcting the base combustion amount based on the pressure detected by the pressure detector. The above configuration is a configuration known in Patent Document 1. Here, the said steam line means not only a mere pipe line but the flow path through which a vapor | steam distribute | circulates.

  The embodiment of the present invention is characterized in that, when the controller sets the base combustion amount, the controller sets the base combustion amount based on a detected flow rate obtained by subtracting a setting error from the detected flow rate. In the configuration.

  The setting error includes at least the following two. The first error is not due to the flow rate detector, but is an error inherent in the system. This first error is caused when the steam from the boiler condenses in the course of flowing through the steam line, or when the steam from the boiler is low in dryness, the steam actually supplied compared to the detected flow rate. This is because the amount is reduced. This first error occurs remarkably in a system that does not include the steam accumulator described in Patent Document 1. The second error is an error inherent to the flow rate detector due to low detection accuracy of the flow rate detector.

  The setting error preferably includes both the first error and the second error. However, when the detection accuracy of the flow rate detector is very high, only the first error can be set. Moreover, although it cannot be considered in a system that normally exists, in the case of a system in which the degree of dryness of steam from the boiler is high and there is almost no condensation of steam in the middle of the steam line, only the second error can be made.

  In the first embodiment, when the operation of the system is started, the controller performs correction using a value obtained by subtracting the setting error from the detection signal of the flow rate detector as a detected flow rate signal. Then, based on the corrected detected flow rate signal, a base combustion amount is set, and unit control is performed so that the boilers are burned so as to be the set combustion amount. That is, since the corrected detected flow rate signal is set to the lower limit side of the assumed error, the steam pressure supplied from the boiler is controlled to the lower side. As a result, the inconvenience due to the high steam pressure can be eliminated. The number control system of this embodiment is preferably implemented in a system that does not include the steam accumulator.

Here, the components of this embodiment will be described. As long as the boiler generates steam and the combustion amount is adjustable (variable), the type, type, and evaporation amount are not limited. That is, the boiler is not limited to a three-position boiler for stop, low combustion, and high combustion, but includes a boiler whose combustion amount can be adjusted stepwise at four or more positions, and a boiler whose combustion amount can be continuously adjusted. Including. The boilers may have different evaporation amounts. Further, the number of boilers to be controlled is two or more, but may be one as long as the combustion amount can be adjusted to multiple positions or the combustion amount can be continuously adjusted. Thus, when using one boiler, the boiler inner body is contained in the steam line which detects steam pressure.

  As the flow rate detector, a known detector is used. In this embodiment, a relatively inexpensive detector with a detection accuracy of plus or minus about 10% is preferably used. At present, steam flow meters with high detection accuracy are expensive. This flow rate detector is provided in a steam line connected to the boiler body of each boiler, and preferably, steam is supplied from a steam collecting part (steam header) that collects steam generated in each boiler to steam using equipment. Provide in the supply steam line. In addition, the flow rate detector detects the flow rate of steam with a single flow rate detector when there is a single steam line to the steam-using facility, but when there are multiple steam lines, a plurality of flow rates are detected. The detector can be configured to detect the total steam flow used. Furthermore, for steam using equipment with a small amount of steam used, the use steam flow setting error of other main steam using equipment can be made without providing a flow rate detector. That is, the steam flow rate of the steam-using facility without the flow rate detector can be included as the third error of the setting error.

  The pressure detector is provided to detect the pressure of the steam line from the boiler, and is preferably provided in the steam collecting portion. Since the pressure of the steam collecting portion corresponds to the temperature of the steam on a one-to-one basis, in this embodiment, the pressure is indirectly detected by temperature detection. However, in the case of temperature detection, air is sometimes included in the steam and does not correspond to pressure, so pressure detection is desirable.

  The controller controls the combustion amount of each boiler based on the detected flow rate by the flow rate detector and the detected pressure by the pressure detector in accordance with a control procedure stored in advance in the storage means. The control procedure sets a base combustion amount of the boiler based on the detected flow rate, and controls the combustion of each boiler so as to be a set combustion amount (main combustion number control), And a second procedure for controlling the combustion of each boiler by controlling the base combustion amount based on the pressure detected by the pressure detector (controlling the number of auxiliary combustion units). Since the time delay occurs in the change of the steam pressure after the combustion control by the first procedure is performed, the second procedure is configured to be executed after the predetermined delay time in consideration of the time delay. In many cases, this time delay is not taken into account, and no particular problem occurs.

  In the first procedure, when the base combustion amount is set, the base combustion amount is set based on a detected flow rate obtained by subtracting an error set for the flow rate detector from the detected flow rate. The correspondence between the detected flow rate signal and the base combustion amount of the boiler is obtained in advance by experiments, and the obtained correspondence relationship is stored in the storage means.

  The second procedure is performed by adjusting the combustion amount of a boiler other than the base boiler that covers the base combustion amount so that the detection pressure of the pressure detector becomes a set pressure. When the combustion amount can be adjusted, the combustion amount can be adjusted by the second procedure using the boiler.

  The correction of the combustion amount is performed by adjusting the number of stages of combustion when each of the boilers increases or decreases the combustion amount in stages, and the combustion amount is corrected when the boiler continuously increases or decreases the combustion amount. This is done by continuously adjusting the amount.

  Further, the method of correcting the combustion amount is not limited to the method of adjusting the ratio between the number of low combustion units and the number of high combustion units as described in Patent Document 1, and for example, the following second method is used. Can be adopted.

This second method monitors the fluctuation of the steam flow rate (the fluctuation amount per unit time or the gradient of the fluctuation), and if the fluctuation is smaller than a predetermined value, the detected pressure is adjusted to reduce the heat dissipation loss. Based on the detected pressure, the combustion amount is adjusted so as to reduce the number of combustions set based on the detected flow rate, and when the fluctuation is larger than a predetermined value, low combustion or combustion standby based on the detected pressure This is a method of adjusting the combustion amount so as to increase the number of units. According to this second method, the efficiency of the system can be improved.

  Furthermore, the correction method of the combustion amount is based on the absolute value (pressure value) of the pressure of the supplied steam in a predetermined control pressure zone, which can be performed by step value control or target value control. This is control for increasing or decreasing the number of boiler combustions. For example, the control pressure band is set by a step value control pressure that is an upper limit value of the pressure band and a step value control width that is a width of the pressure band. This step value control is performed by controlling the number of burned units of the plurality of boilers based on the pressure value of the supplied steam in the control pressure zone and the priority of activation (hereinafter simply referred to as priority). Here, the control of the number of burned boilers includes not only control with one boiler as one unit, but also includes, for example, number control in which low combustion is regarded as one and high combustion is regarded as two. .

The target value control is a method for controlling the combustion state of the boiler based on a determination condition for increasing or decreasing the number of boiler combustions so that a preset target pressure is obtained. The determination conditions include the following.
(1) Deviation from target pressure (displacement)
(2) Deviation from target pressure and duration of the state
(3) Pressure change situation (gradient of pressure change and whether the slope is increasing or decreasing)
(4) Pressure change status and duration
(5) Displacement integrated value obtained from the amount of displacement from the target pressure and time

  The determination conditions are not limited to the above (1) to (5), but may be configured to determine a combination of the above (1) to (5) and control the number of burned boilers. it can.

  The present invention includes the following method embodiments. An embodiment of this method includes a plurality of boilers whose combustion amounts can be adjusted, a flow rate detector for detecting a steam flow rate provided in a steam line from the boiler, and a pressure detection for detecting a steam pressure in the steam line. Of a boiler that sets the base combustion amount of the boiler based on the flow rate detected by the flow rate detector and corrects the base combustion amount based on the pressure detected by the pressure detector. A combustion control method, wherein when setting the base combustion amount, the base combustion amount is set based on a detected flow rate obtained by subtracting an error set for the flow rate detector from the detected flow rate. To do.

  Embodiment 1 of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram of the first embodiment, FIG. 2 is a diagram for explaining setting of the number of base combustions with respect to the detected steam flow rate of the first embodiment, and FIG. 3 is the number of the first embodiment. It is a flowchart figure which shows a control method.

  As shown in FIG. 1, the boiler system of the one embodiment includes a plurality of (12 in this embodiment) steam boilers 1, 1,... (Hereinafter, the steam boiler is simply referred to as a boiler) and the above. The first steam lines 2, 2,... Connected to each boiler 1, the steam header 3 connected to the first steam line and constituting a part of the steam line, and the steam header 3 and steam using facilities 4A, 4B. The second steam lines 5A and 5B connected between the first steam lines 5A and 5B, the flow rate detections 6A and 6B for detecting the steam flow rates in the second steam lines 5A and 5B, and the pressure detection for detecting the pressure of the steam header 3. And a number controller 8 (hereinafter simply referred to as a controller).

  Each of the boilers 1 is a three-position boiler having an evaporation amount of 2000 kg / h and adjustable in three stages of a combustion amount stop, low combustion, and high combustion. Each of the flow rate detectors 6A and 6B uses the same known detector which is relatively inexpensive and has a detection accuracy of about + and −10%. In the first embodiment, a steam accumulator as in Patent Document 1 is not provided between each boiler 1 and the steam header 3.

  In the controller 8, the flow rate detectors 6A and 6B, the pressure detector 7 and the boilers 1 are connected to each other by lines (reference numerals omitted) indicated by broken lines in FIG. The controller 8 follows the control procedure stored in advance in the storage means (not shown), and based on the detected flow rate by the flow rate detectors 6A and 6B and the detected pressure by the pressure detector 7, each boiler 1 It is comprised so that the amount of combustion of may be controlled.

  The control procedure includes a first procedure and a second procedure, and is configured as shown in FIG. In the first procedure, the base combustion amount of the boiler 1 is set based on the flow rate R detected by the flow rate detectors 6A and 6B, and the combustion of each boiler 1 is controlled so as to become the set combustion amount. Configured. When the detected pressure at the beginning of operation of the system is outside the set range (for example, 5 MPa to 8 MPa), the combustion amount is controlled so that the detected pressure is within the set range only by the detected pressure of the pressure detector 7. Normal pressure control is performed before the first procedure. The second procedure includes a second procedure for correcting the base combustion amount based on the pressure detected by the pressure detector 7. When the detected pressure falls within a set range by the normal pressure control, the first procedure is performed.

  In the first procedure, the base combustion amount is set based on a detected flow rate R1 obtained by subtracting an error (hereinafter referred to as a setting error) R0 set for the flow rate detectors 6A and 6B from the detected flow rate R. . The correspondence relationship between the detected flow rate signal R1 and the base combustion amount of the boiler is obtained in advance by experiments, and the obtained correspondence relationship is stored in storage means (not shown).

  Here, the setting error R0 will be described. The error of the detected flow rate by each of the flow rate detectors 6A and 6B includes the following two. The first error is not caused by the flow rate detectors 6A and 6B. This first error occurs when the steam from each boiler 1 condenses in the middle of flowing through each steam line 2 and the steam header 3, or when the dryness of the steam from each boiler 1 is low. This is because the amount of steam actually supplied from the detected flow rate R is reduced. The second error is an error caused by the low detection accuracy of the flow rate detectors 6A and 6B.

  The setting error R0 is set for the actual detection signal R by the flow rate detectors 6A and 6B in consideration of both the first error and the second error. This setting error R0 is set in advance by experiments. The second error exists on the + (plus) side with respect to the detection signal R, but the first error does not exist on the + (plus) side with respect to the detection signal R. That is, the setting error R0 is larger than the error on the + side existing with respect to the detection signal R.

  In the first embodiment, the second procedure is performed by adjusting the combustion amount of the boilers other than the base boiler 1 that covers the base combustion amount so that the detected pressure of the pressure detector 7 becomes the set pressure. It is configured. In the adjustment of the combustion amount by the second procedure, a time delay occurs in the change in the pressure of the steam header 3 after the combustion control by the first procedure is performed. It is configured to be executed after (for example, about 3 to 20 seconds).

Below, the number control method by the said controller 8 is demonstrated according to FIG. 2 and FIG. In FIG. 3, it is determined in step S1 (hereinafter, step SN is simply referred to as SN) whether or not the operation of the system is started. The operation start is determined by operating a system operation start switch (not shown). If YES is determined in S <b> 1, the process proceeds to S <b> 2 and it is determined whether or not the detected pressure signal is within the set range. Since the detected pressure of the pressure detector 7 is outside the setting range and below at the beginning of operation, the process proceeds to S8, and the detected pressure is determined to be within the set range only by the detected pressure of the pressure detector 7. The amount of combustion is controlled so that This combustion amount control is performed by full power operation in which all the boilers 1 are burned at high speed by well-known step value control, and is performed until the detected pressure falls within the set range.

  If YES is determined in S2, the process proceeds to S3, and the detected flow rate is corrected. In this correction process, a corrected detected flow rate R1 is set by subtracting a setting error R0 set for the flow rate detectors 6A and 6B from the total value R of the detected flow rates of the flow rate detectors 6A and 6B. In S4, a base combustion amount (the number of burned units) is set based on the corrected detected flow rate R1. In FIG. 2, the number of combustion of the boilers 1 is set to 7 on the basis of the corrected detected flow rate R1 at time t1. These seven units are all set to high combustion. Based on the set number of combustions, the main combustion number control for causing the boilers 1 to perform high combustion is performed in accordance with a predetermined priority order. The processes of S3 and S4 correspond to the first procedure.

  When the main combustion number control is delayed for a predetermined time, that is, when the fluctuation at the start of the steam flow rate falls within a predetermined range, the auxiliary combustion number control in S5 is performed. In this auxiliary combustion number control, the combustion amount of the boilers 1 other than the boilers 1 (seven units at time t1) that cover the base combustion amount is adjusted so that the detection pressure of the pressure detector 8 becomes the set pressure. To do. In the first embodiment, the number of boilers 1 corresponding to the auxiliary combustion number control is set to two. However, the present invention is not limited to this. The adjustment of the combustion amount is performed by step value control. This auxiliary combustion number control is continued for a time T0. The process of S5 corresponds to the second procedure.

  While the process of S5 is performed, the elapse of the set time T0 is monitored in S6. If NO is determined, the process proceeds to S7, where it is determined that the system is stopped. If NO, the process returns to S6. When the elapse of time T0 is determined in S6, the process returns to S2 and the processes of S2 to S5 are repeated. In the example of FIG. 2, the number of base combustion boilers is set to 6 based on the corrected detected flow rate R1 at time t2, and after performing the main combustion number control, the auxiliary combustion number control is performed.

  Thus, the combination of the main combustion number control based on the detected flow rate of the steam of each of the flow rate detectors 6A and 6B and the auxiliary combustion number control based on the detected pressure of the pressure detector 8 makes smooth the fluctuation of the steam load. Follow-up control is possible. Further, since the base combustion amount is set based on the detected flow rate R1 obtained by subtracting the setting error R0 of the flow rate detectors 6A and 6B from the detected flow rate R, the steam pressure is increased due to the detection error of the flow rate detector. To prevent inconvenience caused by an increase in steam pressure. And a flowmeter with comparatively low detection accuracy can be used, without using a steam accumulator like patent documents 1.

  The present invention is not limited to the first embodiment, but includes the second embodiment shown in FIG. Hereinafter, in the second embodiment, description will be made mainly on the configuration different from that of the first embodiment.

  The second embodiment includes a second steam line 5C for supplying steam to the steam using facility 4C in addition to the two second steam lines 5A and 5B, and a flow rate detector is provided in the second steam line 5C. This is different from the first embodiment in that it is not provided.

In the second embodiment, the average steam flow rate of the second steam line 5C is smaller (for example, about 10%) than that of the second steam lines 5A and 5B. Are included in the setting error.

  The present invention is not limited to the first and second embodiments, and a single flow rate detector 6 can be provided in a common steam line as in the third embodiment shown in FIG.

  In addition, the present invention is not limited to the first to third embodiments, and the boilers 1, 1,... Can include boilers having different evaporation amounts and continuously control the combustion amount. A boiler can be included. Further, as disclosed in JP-A-2002-213702, it is possible to perform the number control without using a common number controller.

1 Steam boiler (boiler)
2 First steam line (steam line)
3 Steam header (steam line)
5A Second steam line (steam line)
5B Second steam line (steam line)
5B Second steam line (steam line)
6 Flow detector 6A Flow detector 6B Flow detector 7 Pressure detector

Claims (3)

A boiler comprising one or more boilers capable of adjusting the combustion amount, a flow rate detector for detecting a steam flow rate provided in a steam line from the boiler, and a pressure detector for detecting a steam pressure of the steam line. A boiler combustion control method that is performed in a control system, sets a base combustion amount of the boiler based on a flow rate detected by the flow rate detector, and corrects the base combustion amount based on a pressure detected by the pressure detector. And
A boiler combustion control method comprising: setting the base combustion amount based on a detected flow rate obtained by subtracting a setting error from the detected flow rate when setting the base combustion amount. One or more boilers capable of adjusting the combustion amount, a flow rate detector for detecting a steam flow rate provided in a steam line from the boiler, a pressure detector for detecting a steam pressure in the steam line, and the flow rate In a boiler control system comprising a controller for setting a base combustion amount of the boiler based on a detection flow rate by a detector and correcting the base combustion amount based on a detection pressure by the pressure detector,
The controller, when setting the base combustion amount, sets the base combustion amount based on a detected flow rate obtained by subtracting a setting error from the detected flow rate.   The boiler control system according to claim 2, wherein a steam accumulator is not provided between the boiler and the flow rate detector and the pressure detector.

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