JP3975127B2 - Multi-can installation boiler with unit control - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a multi-can installation boiler that controls the number of units.
[0002]
[Prior art]
A boiler multi-can installation system is known in which a plurality of boilers are installed and the amount of steam supplied to the entire boiler is controlled by adjusting the combustion state of each boiler. In the case of a multi-can installation system for steam boilers, the steam generated in each boiler is gathered in a steam header and supplied to the steam use section, and each steam pressure is detected based on the steam pressure value detected by the pressure detection device provided in the steam header. Perform unit control to determine the combustion state of the boiler. In unit control, the steam pressure control range is divided into multiple pressure categories, a combustion pattern that determines the combustion state of the boiler is set for each pressure category, and the steam pressure value detected by the steam header is assigned to which pressure category. The combustion state of each boiler is determined depending on whether it corresponds, and the amount of evaporation of the boiler is controlled. The pressure section is determined with a certain width, and the boiler combustion amount decreases as the steam pressure value shifts to the high pressure side pressure section, and conversely the boiler combustion amount increases as the steam pressure value shifts to the low pressure side pressure section.
[0003]
In the case of installing multiple cans, each boiler is generally controlled at three positions of high combustion, low combustion, and stop, and the low combustion generally uses a boiler whose evaporation amount is about half that of high combustion. Fig. 4 shows an example of conventional unit control, where six three-position combustion control boilers that control combustion with high combustion, low combustion, and stop are installed, and the steam pressure control range is 0.74 MPa to 0.85 MPa. The combustion pattern is shown. The value of the amount of evaporation per boiler is 1 for low combustion and 2 for high combustion. 11 pressure categories within the steam pressure control range of 0.74MPa to 0.85MPa, and two pressure categories above and below the steam pressure control range, a total of 13 pressure categories are defined, and the combustion state of the boiler in each pressure category Is stipulated. Prioritization of combustion is determined for the six boilers, and combustion is performed in order from the highest priority. The combustion state of the boiler is indicated by “H” in the case of high combustion, “L” in the case of low combustion, and “−” in the case of stop, and the value of the evaporation amount in the entire boiler in each combustion state is described. is doing.
[0004]
If the steam pressure value is higher than 0.85MPa, stop all boilers, if the evaporation value is 0 and the steam pressure value is 0.84MPa ~ 0.85MPa When the first boiler is low-burning and the other boilers are stopped, the evaporation value is 1, and the steam pressure value is in the pressure category of 0.83MPa to 0.84MPa, the priority is the 1st and 2nd The boiler has low combustion and the evaporation value is 2. Similarly, the steam pressure value is less than 0.74 MPa, all the boilers have high combustion, and the combustion state until the evaporation value becomes 12 is defined. .
[0005]
By changing the stopped boiler to low combustion or changing the low combustion boiler to high combustion, the evaporation amount increases, and conversely, the low combustion boiler is stopped or high combustion is performed. The amount of evaporation is reduced by changing the boiler to low combustion. When changing the combustion state of the boiler between low combustion and high combustion or when stopping the combustion, the evaporation amount can be changed in a short time, but when starting the combustion of the stopped boiler, pre-purge etc. Since time required for preparation is required, it takes a relatively long time from the start of combustion to the start of actual generation of steam. When the steam pressure value is 0.80 MPa or less and the amount of evaporation is increased by changing the low combustion boiler to high combustion, the amount of combustion can be changed in a very short time. However, when the steam pressure value is 0.80 MPa or more and the increase in the evaporation amount is performed by changing the stopped boiler to low combustion, it takes a long time to change the evaporation amount.
[0006]
In addition, when the number of pressure sections that divide the steam pressure control range increases, the pressure width of each pressure section becomes narrower, and if the steam pressure value changes, it will move to the next pressure section in a short time. . If it takes a long time from the start of combustion to the actual generation of steam and the pressure range has a narrow pressure range, the steam pressure value decreases while preparing for steam generation, and the pressure on the lower pressure side It becomes a category, and combustion may be started even for boilers that do not normally need to be combusted. For example, if the steam pressure should have stabilized only by increasing the number of combustion units by one, but the steam pressure has further decreased even if a combustion instruction is given, sending a combustion instruction to two or more boilers When the steam supply is started, the vapor pressure increases rapidly because the evaporation amount is too large. In this case, an output for reducing the number of combustion must be performed immediately after the start of combustion, which may cause hunting to repeatedly reduce the vapor pressure again by suddenly reducing the evaporation amount.
[0007]
If hunting occurs, the stability of the steam supply will deteriorate, and if the boiler starts and stops frequently, the efficiency of the boiler will decrease, and if the number of starts and stops increases, the life of the equipment will be shortened. There is a problem of becoming.
[0008]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to prevent the occurrence of hunting and stabilize the supply of steam in a boiler multi-can installation system.
[0009]
The invention described in claim 1 includes a plurality of boilers installed in parallel, a pressure detection device that detects the pressure of steam generated in the boiler, and a number control device that controls the number of boiler combustions based on the detected steam pressure value. In the multi-can boiler, the steam pressure control range is divided into a plurality of pressure sections, and a combustion pattern that determines the combustion state of the boiler is set for each pressure section. Based on the steam pressure value detected by the pressure detection device and the combustion pattern, in a multi-can installation boiler that performs unit control for controlling the combustion state of each boiler,
When the steam pressure control range is set to the number limit setting value and the number limit release setting value, and the steam pressure value is higher than the number limit setting value, the number of boilers and the number of pressure categories to be controlled Unit control based on the combustion pattern with fewer parts, and when the steam pressure value becomes lower than the set value for canceling the unit limit, the unit control is performed based on the combustion pattern with the number of boilers and the number of pressure categories to be controlled. And
In the above-mentioned combustion pattern, a plurality of pressure categories are set for each, and the pressure category in the combustion pattern in which the number of units to be controlled is reduced is the number of units to be controlled by the steam pressure value becoming higher than the set value for the number limit. If the pressure classification that is entered when the combustion pattern is changed to be reduced is used as a reference, at least one pressure classification is provided on the low pressure side of the reference pressure classification, and the set number for releasing the unit restriction is higher than the reference pressure classification. One value is lower than the value in the pressure section provided on the low pressure side .
[0010]
The invention according to claim 2 is such that in the multi-can installation boiler that performs the number control, the steam pressure control range after the number control target boiler is decreased is higher than the steam pressure control range before the number control target boiler is decreased. It is characterized by that.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an installation example of a multi-can installation boiler for carrying out the present invention, FIG. 2 is an explanatory diagram showing the relationship between the pressure classification and the combustion state of the boiler in the first embodiment, and FIG. 3 is a pressure in the second embodiment. It is explanatory drawing which showed the relationship between a division | segmentation and the combustion state of a boiler. A plurality of boilers that perform combustion control at three positions of high combustion, low combustion, and stop are installed, and a steam header 4 that collects steam generated in each boiler 1 is provided. The boiler 1 and the steam header 4 are connected by the steam pipe 5, and the generated steam is collected in the steam header 4 and then sent to the steam using unit 2. The steam header 4 is provided with a pressure detector 6 for detecting the steam pressure, and the steam pressure value detected by the pressure detector 6 is sent to the unit control device 3. Each boiler is provided with an operation control device 7, and the operation control device 7 receives a combustion request signal from the number control device 3 and performs combustion control of the boiler.
[0012]
The number control of the boiler performed by the number control device 3 is performed based on the combustion pattern set in the number control device 3, and the lower the steam pressure value detected by the pressure detector 6, the more the combustion amount is increased. The higher the value, the lower the combustion amount. If the amount of steam generated is greater than the amount of steam used, the steam pressure will increase.If the amount of steam generated is less than the amount of steam used, the steam pressure will decrease, and the steam pressure value will fall within the control pressure range. The combustion amount of the boiler is controlled so that
[0013]
First, a description will be given based on the first embodiment shown in FIG. In this example, six three-position combustion control boilers that control combustion with high combustion, low combustion, and stop are installed, the steam pressure control range is 0.74MPa to 0.85MPa, and the amount of evaporation per boiler is The value is set to 1 in the case of low combustion, and 2 in the case of high combustion. Also in FIG. 2, the high combustion state is represented by “H”, the low combustion state is represented by “L”, and the stop state is represented by “−”, and the total evaporation amount in each combustion state is represented numerically. .
[0014]
The number control device 3 has a combustion pattern in which the number control is performed using all the boilers, and a combustion pattern in which some boilers are excluded from the number control target and the number control is performed only with the remaining boilers. Pattern B is set. In pattern A, the number of boilers is controlled by six boilers, and the steam pressure value is divided into 13 pressure sections, and the combustion state of the boiler is determined for each section. The width of each pressure division within the steam pressure control range is 0.01 MPa, and the combustion amount is changed every time the steam pressure value changes by 0.01 MPa. Pattern B is a unit control to prevent hunting at low load. Of the six installed boilers, half of the boilers are separated from the unit control target, and the unit control is performed with the remaining three boilers. . The steam pressure value is divided into seven pressure sections, and the combustion state of the boiler is determined for each section. In this case, the pressure division width is 0.02 MPa, and the combustion amount is changed every time the steam pressure value changes by 0.02 MPa. Boilers that are not subject to unit control are indicated by “x”, and the boilers with the fourth or higher priority do not burn regardless of the steam pressure value.
[0015]
The number control is performed based on either the pattern A or the pattern B, and the pattern A and the pattern B are switched depending on the load situation. The number limit setting value for switching from pattern A to pattern B is set to 0.82 MPa. When the number control is performed in pattern A and the steam pressure value exceeds 0.82 MPa, the control is switched to the number control by pattern B. In addition, the setting value for canceling the restriction on the number of units to be switched from pattern B to pattern A is set to 0.77 MPa, and when the number control is performed in pattern B, if the steam pressure value falls below 0.77 MPa, the unit is switched to the number control by pattern A. . Therefore, the region where the vapor pressure value in the pattern A is 0.82 MPa or more and the region where the vapor pressure value in the pattern B is 0.77 MPa or less are not used. In the present embodiment, the combustion state is described even in the region of the pressure section that is not used for easy comparison with the conventional example, but the combustion state is set in the region that is not used in the actual number control device 3. do not have to.
[0016]
More specific description will be given below. When the number control is performed by the pattern A, if the steam pressure value is within the pressure range of 0.81 MPa to 0.82 MPa, the combustion state of the boiler is “LLLL”, and the four boilers perform low combustion. After that, when the steam pressure value rises and the pressure section exceeds 0.82 MPa, the process shifts to pattern B unit control. At the time of shifting to pattern B, it enters the pressure section from 0.81MPa to 0.83MPa, and the combustion state of the boiler in the pressure section is two low combustion, so the boiler with the third priority and the boiler with the fourth priority And the boilers with the first and second priority ranks continue low combustion. When the steam pressure value further rises and the steam pressure value enters the pressure category from 0.83MPa to 0.85MPa, the boiler with the second highest priority is stopped, and conversely the steam pressure value decreases and 0.79MPa to 0.81MPa The boiler with the third highest priority is set to low combustion.
[0017]
Thereafter, the number control by the pattern B is performed until the steam pressure value decreases to the set value for canceling the number limit. When the number control of the boiler is performed based on the pressure category of pattern B, when the steam pressure value becomes lower than 0.77 MPa, the control is switched to the number control by pattern A. The combustion state of the boiler in the pressure section from 0.77 MPa to 0.79 MPa in Pattern B is “HLL”, but the combustion state of the boiler in the pressure section from 0.76 MPa to 0.77 MPa in Pattern A is “HHHLLL”. Two boilers and one low combustion boiler will be added. After that, the number of units is controlled based on Pattern A, and when the steam pressure value further falls and the steam pressure value enters the pressure range from 0.75 MPa to 0.76 MPa, the boiler that has been performing low combustion is the fourth-ranked boiler. If the steam pressure value rises and falls within the pressure range of 0.77 MPa to 0.78 MPa, the boiler with the third highest priority is set to low combustion. Thereafter, the number of boilers is controlled based on the pattern A until the steam pressure value exceeds 0.82 MPa which is the set value for limiting the number of units.
[0018]
When performing unit control based on pattern A, the combustion amount can be increased by setting the low combustion boiler to high combustion at high load when all boilers are in a combustion state of low combustion or higher. Can be increased in a short time, and hunting will not occur even if the width of the pressure section is narrow. However, even in the case of unit control based on the same pattern A, a relatively long time is required to increase the evaporation amount by setting the stopped boiler to low combustion, so the width of the pressure section is narrowed. May cause hunting. In particular, when the number of combustion is low and the load is low, hunting is likely to occur because the steam pressure value is greatly affected even if one boiler is started or stopped.
[0019]
In the case of a low load, it is possible to prevent the occurrence of hunting by limiting the number of boilers subject to unit control and setting the pattern B with a wider pressure section. The width of each pressure section in pattern B is twice that of pattern A. If the pressure section is wide, the steam pressure value stays within one pressure section when the steam pressure value changes. Become. In other words, in the case of Pattern B, even if the change in the combustion amount is not performed with a slight pressure fluctuation, the time until entering the next pressure section becomes long even if the steam pressure value is uniformly reduced. Therefore, hunting that occurs by instructing the start of combustion to more than the required number of boilers in a short time is less likely to occur. However, since the steam supply amount should not be insufficient by restricting the number of boilers operated, when the steam pressure value drops to a certain level or less in the number control by pattern B, switch to the number control by pattern A, The steam pressure value can be increased.
[0020]
The number limit setting value and the number limit release setting value can be set to arbitrary values, but the number limit setting value is approximately 25% at the load of the boiler that is the number control target. is set to prospect for about 80 percent at a load of the boiler being the number controlled object, it is possible to stabilize the vapor pressure.
[0021]
Next, the second embodiment will be described with reference to FIG. In the case of the second embodiment, instead of the pattern B described in the first embodiment, combustion in which the steam pressure control range after the number control target boiler reduction is higher than the steam pressure control range before the number control target boiler reduction. Pattern C, which is a pattern, is set. The same as the first embodiment except that the steam pressure control range of pattern C is high and the set value for canceling the number of units to be switched from pattern C to pattern A is 0.79 MPa.
[0022]
When the number control is performed by the pattern A, if the steam pressure value is within the pressure range of 0.81 MPa to 0.82 MPa, the combustion state of the boiler is “LLLL”, and the four boilers are set to low combustion. When the steam pressure value rises and the pressure section exceeds 0.82 MPa, the process shifts to pattern C unit control. At the time of shifting to Pattern C, it enters the pressure section from 0.81 MPa to 0.83 MPa, and the combustion state of the boiler in the pressure section is three low combustion, so the boiler with the fourth priority is stopped, the priority order However, the 1st to 3rd boilers continue low combustion. Thereafter, based on the pattern C, control is performed such that when the steam pressure value increases, the number of boilers burned decreases, and when the steam pressure value decreases, the number of boilers burned increases.
[0023]
When the number control of the boiler is performed based on the pressure category of pattern C, when the steam pressure value becomes lower than 0.79 MPa, the control is switched to the number control by pattern A. The combustion state of the boiler in the pressure section of pattern C from 0.79 MPa to 0.81 MPa is “HLL”, but the combustion state of the boiler in the pressure section of pattern A from 0.78 MPa to 0.79 MPa is “HLLLLL”. Add three boilers. Thereafter, the number of boilers is controlled based on the pattern A until the steam pressure value exceeds 0.82 MPa, which is the number limit setting value. When switching between two combustion patterns, the combustion state of the boiler must be changed because the pressure classification is different, but it is necessary when switching the combustion pattern by increasing the pattern C steam pressure control range. The amount of boiler combustion state change can be reduced.
[0024]
【The invention's effect】
By implementing the present invention, it is possible to prevent the occurrence of hunting that repeatedly starts and stops combustion, and it is possible to obtain effects such as stable steam supply, improved boiler efficiency, and extended equipment life.
[Brief description of the drawings]
FIG. 1 is an example of installation of a boiler multi-can installation system for carrying out the present invention. FIG. 2 is an explanatory diagram of pressure classification and boiler combustion state in the first embodiment. FIG. 3 is an illustration of pressure classification and boiler in the second embodiment. Explanatory diagram of combustion state [Fig. 4] Explanatory diagram of pressure classification and boiler combustion state in conventional case [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Boiler 2 Steam use part 3 Number control device 4 Steam header 5 Steam piping 6 Pressure detector 7 Operation control device

Claims (2)

A multi-can installed boiler equipped with multiple boilers installed in parallel, a pressure detection device that detects the pressure of steam generated in the boiler, and a unit control device that controls the number of boiler combustions based on the detected steam pressure value In the number control device, the steam pressure control range is divided into a plurality of pressure categories, a combustion pattern that determines the combustion state of the boiler is set for each pressure category, and detected by the pressure detection device. Based on the steam pressure value and the combustion pattern, in a multi-can installation boiler that performs unit control for controlling the combustion state of each boiler,
When the steam pressure control range is set to the number limit setting value and the number limit release setting value, and the steam pressure value is higher than the number limit setting value, the number of boilers and the number of pressure categories to be controlled Unit control based on the combustion pattern with fewer parts, and when the steam pressure value becomes lower than the set value for canceling the unit limit, the unit control is performed based on the combustion pattern with the number of boilers and the number of pressure categories to be controlled. And
In the above-mentioned combustion pattern, a plurality of pressure categories are set for each, and the pressure category in the combustion pattern in which the number of units to be controlled is reduced is the number of units to be controlled by the steam pressure value becoming higher than the set value for the number limit. If the pressure classification that is entered when the combustion pattern is changed to be reduced is used as a reference, at least one pressure classification is provided on the low pressure side of the reference pressure classification, and the set number for releasing the unit restriction is higher than the reference pressure classification. A multi-can installation boiler for controlling the number of units, characterized in that the value is lower than the value in the pressure section provided on one low pressure side . The multi-can installation boiler for controlling the number of units according to claim 1, wherein the steam pressure control range after the number control target boiler is reduced is higher than the steam pressure control range before the number control target boiler is reduced. Multi-can boiler that controls the number of units.

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