JP4059728B2 - Multi-can boiler - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a multi-can installation boiler for preventing hunting.
[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 steam boiler multi-can installation system, the steam generated in the boiler is collected once, and then the steam is supplied to the steam using part, and the steam pressure value detected by the pressure detector installed in the steam collecting part is used. Based on the number control, the combustion state of each boiler is determined. In the number control device, the steam pressure control range is divided into a plurality of pressure categories, and a combustion pattern that determines the combustion state of the boiler is set for each pressure category, and the detected steam pressure value corresponds to which pressure category Thus, the combustion state of each boiler is determined, and the steam supply amount of the boiler is controlled. The pressure section should be set within a certain range.The more the steam pressure value moves to the pressure section on the high pressure side, the smaller the combustion amount in the entire boiler, and vice versa. Do more.
[0003]
As shown in FIG. 4, a differential is provided for each pressure category with the steam pressure value when the boiler combustion amount is increased and the steam pressure value when the boiler combustion amount is decreased. Is not repeated. Fig. 4 shows the relationship between the steam pressure value and the number of boiler combustions when four boilers are installed and the number of boiler combustions is controlled so that the steam pressure value is maintained within the range of 0.70 MPa to 0.81 MPa. . FIG. 5 is an example of a change in the steam pressure value, and describes the operation status of the boiler that is changed in response to the change in the steam pressure value.
[0004]
FIG. 5 starts from a state where only the first-ranked boiler is combusted, and the steam pressure value gradually increases due to the generation of steam due to combustion of the first-ranked boiler (a). When the steam pressure value becomes higher than 0.81 MPa, the unit control device stops the combustion of the first boiler. If the combustion of the boiler is stopped, the supply of steam is lost and the steam pressure value decreases (b). When the steam pressure value decreases to 0.79 MPa, the unit control device outputs a combustion request signal to the first boiler with the highest operation priority. The boiler is dangerous if it is ignited with the fuel leaking during combustion standby and the unburned portion is vaporized in the furnace. Pre-purge needs to be performed, and combustion is started after the completion of the combustion preparation step such as pre-purge. Even if the steam pressure value is stopped to 0.79 MPa and a combustion request signal is output, since the combustion actually starts after the combustion preparation step, the steam pressure value continues to decrease during that time (c) .
[0005]
When the steam pressure drops to 0.76 MPa, the unit control device outputs a combustion request signal to the boiler with the second highest operation priority. However, even if the combustion request signal is output to the first and second boilers in the operation priority order, steam is not generated while the two boilers are performing the combustion preparation process. The steam pressure value continues to decrease (d). When the first boiler finishes the combustion preparation process and starts combustion, the steam pressure value starts to rise (e). Furthermore, when the second boiler also starts to combust, the amount of steam generated increases, so the rate of increase in the steam pressure value increases (f). When the steam pressure rises to 0.78MPa due to steam supply by two boilers, the combustion request signal for the boiler with the second highest operating priority is stopped, the combustion of the second boiler is stopped, and the combustion standby state And By setting the second boiler to stand by, the number of boilers burned becomes one, so the steam pressure rises slowly, and when the steam pressure rises to 0.81 MPa, the first boiler also stops burning. Set to combustion standby (g).
[0006]
In the case of FIG. 5, since the amount of steam used is small, the steam pressure value rises even if only one boiler performs combustion, but the steam pressure has dropped between the output of the combustion request signal and the actual start of combustion. The combustion request signal is also output to the second-ranked boiler that normally does not require combustion. Therefore, when the 2nd boiler starts combustion, the steam pressure rises rapidly, the 2nd boiler stops combustion in a very short time, and the start and stop of the 2nd boiler is unnecessary. It is. Unnecessary boiler start / stop will cause a large increase / decrease in the steam pressure. Repeating the vicious cycle of increasing the number of start / stop of the boiler will shorten the life of the boiler and increase energy loss. There is a problem of doing.
[0007]
[Problems to be solved by the invention]
The problem to be solved by the present invention is to prevent boiler hunting at low load, and to extend life and reduce energy loss.
[0008]
[Means for Solving the Problems]
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 outputs a combustion request signal to a boiler that performs combustion. Each of the multi-can installed boiler systems, the number control device calculates the required number of combustion from the steam pressure value detected by the pressure detection device, the preset operation priority order In order from the highest to the lowest number of boilers that have been calculated, a combustion request signal is output to burn the required number of boilers, and the remaining boilers are placed on standby to adjust the amount of steam generated. In the boiler, the boiler with the highest operation priority is continuously purged while the combustion is waiting, and the boilers other than the boiler with the highest operation priority are continuously connected during the combustion standby. In line Cormorant multi cans installed boiler control to stop the operation of the boiler without purging, on a unit controller, the differential in vapor pressure value to reduce the combustion quantity of the vapor pressure values and the boiler to increase the combustion volume of the boiler The differential between the steam pressure value at which combustion of the boiler with the highest operational priority is started and the steam pressure value at which it stops is determined as the difference between the steam pressure value at which combustion is started and the steam pressure value at which it is stopped in other boilers. It is a multi-can installation boiler characterized by being larger than the differential .
[0010]
According to the second aspect of the present invention, in the multi-can installation boiler, when a plurality of boilers having the highest operation priority are set, the number of boilers that perform continuous purge is one or more. It is a multi-can installation boiler characterized in that it is set to an arbitrary number equal to or less than the number of boilers with the highest priority.
[0011]
According to the third aspect of the present invention, in the multi-can installation boiler, when the boiler having the highest operation priority cannot be operated, the boiler performing the continuous purge is temporarily assigned to the boiler having the next highest operation priority. When the boiler having the highest operation priority is able to be operated, the boiler can be set back to the control of continuously purging with the boiler having the highest operation priority.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram of a boiler installation state. FIG. 2 is an explanatory diagram of the boiler operation state showing the change of the steam pressure value and the operation state of the boiler, and FIG. 3 is an explanatory diagram showing the relationship between the steam pressure value and the number of boilers burned. First, the installation state of the boiler will be described with reference to FIG. Four boilers are installed in parallel, and the boiler 1 is connected to the steam header 4 through a steam pipe 5. The steam generated in each boiler 1 gathers in the steam header 4 and supplies steam from the steam header 4 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 detected by the pressure detector 6 is output to the unit control device 3. Each boiler 1 is provided with an operation control device 7, and each operation control device 7 is connected to the number control device 3. The operation of the boiler is performed based on a combustion request signal output from the number control device 3 to the operation control device 7 of each boiler.
[0013]
The number control device 3 is set with a combustion pattern that determines the number of boiler combustions according to the steam pressure value, and calculates the required number of combustion based on the steam pressure value detected by the pressure detector 6. A combustion request signal is output to the boilers corresponding to the number of burned units. The number control device 3 decreases the number of boilers that output the combustion request signal if the steam pressure value increases, and increases the number of boilers that output the combustion request signal if the steam pressure value decreases.
[0014]
When the steam pressure falls below 0.70MPa, the number of boilers burned is four. When the steam pressure rises to 0.72MPa, the number of burners becomes three. When the steam pressure rises to 0.75MPa, the number of burners becomes two. When the pressure value rises to 0.78 MPa, the number of combustion units is set to 1; when the steam pressure value rises to 0.81 MPa, the number of combustion units is set to 0. In the case of an increase in the number of combustion units, if the steam pressure value drops to 0.78 MPa, the number of combustion units will be one unit. If the steam pressure value decreases to 0.76 MPa, the number of combustion units will be two units. If the number of units drops to 3 and the steam pressure drops to 0.70 MPa, the number of burns will be 4 units.
[0015]
In the number control device 3, the operation priority is determined from the first to the fourth for the four boilers, and the combustion request signal is output for the number of combustion units in order from the boiler with the highest operation priority. To do. The unit control device 3 outputs a combustion request signal or a continuous purge signal to the boiler having the highest operation priority, and outputs a combustion request signal to the boilers other than the boiler having the highest operation priority. It is set so that the continuous purge signal is not output only as to whether or not.
[0016]
Next, the operation state of the boiler will be described based on the steam pressure value change shown in FIG. FIG. 2 starts from a state where the boiler with the first operating priority is burning. The number control device 3 outputs a combustion request signal to the first boiler, the first boiler is burning, and the steam pressure value gradually increases due to the generation of steam by the first boiler (A). . At this time, the unit control device 3 does not output a combustion request signal to the boilers whose operation priority is from second to fourth, and the second to fourth boilers are in a combustion standby state. is there. Only the boiler with the highest operation priority is subjected to continuous purge, and the unit control device 3 does not output a continuous purge signal, so the second to fourth boilers do not perform continuous purge.
[0017]
When the steam pressure value becomes higher than 0.81 MPa, the unit control device 3 stops the combustion request signal for the first boiler and outputs a continuous purge signal to the first boiler instead. In the first boiler that has received the continuous purge signal instead of the combustion request signal, the fuel supply is stopped to stop the combustion and perform the combustion stop process. A continuous purge (continuous P) in which only blowing is continued until the start of combustion is performed. In the case of a boiler that is continuously purged, the amount of air supplied to the furnace is set as the amount of air for boiler ignition, so that combustion can be started in a short time when the next combustion starts.
[0018]
If the combustion of the first boiler is stopped, the steam supply to the steam header 4 is also stopped, so that the steam pressure value decreases (B). When the steam pressure value decreases to 0.78 MPa, the unit control device 3 outputs a combustion request signal to the first boiler. The first boiler that has received the combustion request signal switches the operation from the continuous purge to the combustion process and starts supplying steam. Since the first boiler was continuously purged while not burning, pre-purge was already completed, and combustion can be started as soon as a combustion request signal is received. By eliminating the delay for the pre-purge time, the steam pressure value can be changed to an increase before the steam pressure value greatly decreases from 0.78 MPa, and the steam pressure value increases by supplying steam (C) . Since the steam pressure starts to rise before the steam pressure value greatly decreases from 0.78 MPa, it is possible to eliminate the wasteful combustion of the boiler whose operation priority is second or lower.
[0019]
The reason why only the boiler with the highest operation priority is continuously purged and the boilers with the other priority are not continuously purged is because the boiler that reliably shifts from combustion standby to combustion is only the boiler with the highest operation priority. . In the case of the boiler having the highest operation priority, even if the amount of steam used is small, the combustion restarts due to a decrease in steam pressure. However, in the case of boilers of other ranks, combustion is not performed if the amount of steam used is less than the amount of steam generated in one boiler as shown in FIG. Since the blower will continue to operate during continuous purging, if continuous purging is performed with a low operating priority boiler that may not resume combustion, the energy for operating the blower will be wasted if combustion is not performed. . Therefore, energy loss can be reduced by performing continuous purge only on the boiler having the highest operation priority.
[0020]
Also, a differential is provided for the steam pressure value that increases the number of boilers burned and the steam pressure value that decreases the number of boilers burned, but the differential between the steam pressure value at which combustion of the first boiler starts and the steam pressure value at which it stops is differential. Is set to be larger than the differential between the steam pressure value at which combustion is started and the steam pressure value at which it is stopped in the other operation priority boiler in order to prevent the first boiler from stopping combustion in a short time after starting combustion. is there.
[0021]
In the case of unit control without continuous purge, steam supply is started after pre-purge is performed after the combustion request signal is output, and the steam pressure decreases during that time. It is necessary to widen the interval between the combustion demand output start pressures in the boiler. In contrast, when continuous purge is performed, the time from the combustion request signal output to the start of steam supply is short, so the steam pressure value that decreases during that time is small, and the interval from the lower boiler to the combustion request output start pressure is wide. There is no need to do it. And if the time from the combustion request signal output to the start of steam supply is short, the steam pressure starts to increase at a stage where the steam pressure decreases little, so when the steam pressure is increased after the steam pressure value decreases Compared to the increase in the steam pressure, the width is reduced. Therefore, by lowering the combustion start pressure of the first boiler, the differential from the increase in the number of combustion to the decrease in the number of combustion is increased, and the interval from the start of combustion of the first boiler to the stop of the combustion is increased. ing.
[0022]
In this embodiment, only one boiler has the highest operation priority. However, the same operation priority is assigned to a plurality of boilers, and a plurality of boilers are started and stopped simultaneously. There is also a can installation system. In this case, the number of boilers that perform continuous purging is determined based on the normal amount of steam used in the steam using section 2, and the required number of boilers perform continuous purging. When the amount of steam used by the steam use unit 2 is small, select one boiler from the boilers with the highest operating priority, perform continuous purging of only one selected boiler, and operate when the amount of steam used is large Continuous purging is performed on all of the boilers with the highest priority, and if the steam usage is the above-mentioned intermediate value, a fixed number of boilers are selected from the boilers with the highest operating priority and are continuously selected. Set to purge.
[0023]
Also, if combustion cannot be performed due to an abnormality in the boiler with the highest operating priority, the boiler that performs continuous purge is temporarily changed to the boiler with the next highest operating priority, When the boiler with the highest priority is able to burn, the control is returned to the continuous purge with the boiler with the highest operation priority.
[0024]
【The invention's effect】
By implementing the present invention, it is possible to output a combustion request signal even to a boiler that does not require combustion at low load, and to prevent the occurrence of hunting that ends combustion in a short time, and the life due to the decrease in the number of start and stop And energy loss can be reduced.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a boiler installation state in one embodiment. FIG. 2 is an explanatory diagram of changes in steam pressure values and boiler operation states in one embodiment. FIG. 3 is a steam pressure value in one embodiment and the number of boilers burned. Fig. 4 is an explanatory diagram showing the relationship between the steam pressure value and the number of boilers burned in the prior art. Fig. 5 is an explanatory diagram showing changes in the steam pressure value and boiler operating state in the prior art. Explanation of]
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 (3)

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 outputs a combustion request signal to the boiler that performs combustion In the system, the number control device calculates a required number of combustion from the steam pressure value detected by the pressure detection device, and calculates the number of combustions calculated in descending order of operation priority set in advance. In the multi-can installation boiler that adjusts the amount of steam generated by outputting the combustion request signal to the boiler, burning the required number of boilers, and setting the remaining boilers to standby for combustion, the operation priority is the highest Boilers perform continuous purging that continues to blow into the furnace during combustion standby, and boilers other than those with the highest operating priority are not continuously purged during combustion standby. In line Cormorant multi cans installed boiler control to stop the operation, the unit count control device, may be set by providing a differential with steam pressure value for reducing the combustion volume of the vapor pressure values and the boiler to increase the combustion volume of the boiler, Make the differential between the steam pressure value at which the boiler with the highest priority of operation starts and the steam pressure value at which it stops is greater than the differential between the steam pressure value at which other boilers start and stop steam pressure. multi cans installed boiler, characterized in that there. In the multi-can installation boiler according to claim 1, when a plurality of boilers having the highest operation priority are set, the number of boilers that perform continuous purge is one or more and the highest operation priority. A multi-can installation boiler characterized by being set to an arbitrary number equal to or less than the number of boilers. In the multi-can installation boiler according to claim 1 or 2, when the boiler with the highest operation priority cannot be operated, the boiler for continuous purge is temporarily changed to the boiler with the next highest operation priority. When the boiler having the highest operation priority is able to operate, the multi-can installed boiler is returned to the control in which continuous purge is performed with the boiler having the highest operation priority.

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