JP5086145B2 - Multi-can boiler - Google Patents

Description

  The present invention relates to a multi-can installation boiler in which combustion is performed in a required number of boilers in descending order of operation priority in accordance with the required amount of steam, and the operation priority is periodically changed.

  It consists of a plurality of steam boilers and a number control device that outputs an operation command to each boiler, and the required number of boilers are combusted according to the required amount of steam. In this multi-can installation system, the steam pressure value at the steam collecting part is measured, and a set number of boilers are burned corresponding to the steam pressure value. If boilers are prioritized for operation and the steam pressure value decreases and the number of boilers burned increases, combustion starts in order of higher operation priority boilers, and the steam pressure value increases. When the number of boilers to be burned is reduced, the combustion is stopped in order from the boiler with the lowest operation priority. In this case, the boilers with higher operating priority have more opportunities to burn, and if the combustion concentrates on a specific boiler, the life of the entire system will be shortened. The burning time is averaged.

  When changing the operation priority, combustion may be stopped by lowering the order of the boiler that was burning, and combustion may be started by raising the order of the boiler that was stopping combustion instead. . In this case, in the boiler whose combustion is to be stopped, the supply of steam is stopped as soon as the fuel supply is stopped and the combustion is stopped. However, in the boiler that has started combustion, it takes time to prepare for combustion, such as pre-purge, before starting combustion, and even if combustion is started, the can water is heated to start supplying steam. Since it takes time to do so, the steam supply cannot be started immediately even if a command to start combustion is received. Therefore, when the boiler that burns is changed by changing the operation priority, the steam supply amount is insufficient until the boiler that newly starts combustion starts supplying steam, and the supply pressure of steam cannot be maintained. There was a problem that there was something.

  Therefore, in the invention described in Japanese Patent Laid-Open No. 2003-302003, the operation priority is changed for the combustion start boiler ahead of the operation priority change of the other boiler by a preceding time T1. In this invention, for example, the number of boilers that output a combustion command is increased by temporarily setting a plurality of boilers that have the first operating priority, thereby reducing the amount of steam supply. It can be prevented.

  However, in the boiler, the time from the start of combustion to the start of steam supply differs when the combustion starts from a high temperature inside and when the combustion starts from a low temperature. If the inside of the boiler is at a low temperature, the heat generated by the combustion is first used to increase the temperature of the boiler. The steam is supplied from the boiler after the temperature of the can water has risen and the steam pressure in the boiler has increased. Therefore, if the preceding time T1 is short, the steam is insufficient when the operation priority is switched. Conversely, if the inside of the boiler is at a high temperature, the time from the start of combustion to the start of steam supply is short, so if the preceding time T1 is long, the steam supply becomes excessive. For this reason, when the combustion command is output in advance by a certain preceding time T1, the steam supply may become excessive or insufficient depending on the state of the boiler.

In the case of the invention described in Japanese Patent Application Laid-Open No. 2003-302003, the operation priority is changed first by changing the order of the boiler that becomes the first place, and after a certain period of time, the order is changed to the second place. Will change the order of boilers. In this case, the operation priority is changed in stages, and the predetermined time is maintained at each stage. Therefore, when the number of boilers installed increases, the time required for changing the operation priority becomes longer. During the operation priority changing process, the steam pressure value tends to become unstable, and hunting in which the boiler repeatedly starts and stops in a short time may occur.
JP 2003-302003 A

  The problem to be solved by the present invention is to prevent the steam supply amount from changing during the operation priority changing process and to reduce the time required for the operation priority changing process.

  The invention according to claim 1 is a multi-can installation boiler comprising a plurality of steam boilers and a number control device that outputs an operation command to each boiler, and the number control device has an operation priority order for each boiler. In the multi-can installation boiler, which selects the boiler that outputs the combustion command based on the operation priority order, and the operation priority order is changed periodically, each boiler has a steam in each boiler A pressure detection device for detecting the pressure value is provided, and the unit control device detects the steam pressure value in each boiler before changing the operation priority during the operation priority change process, and the steam pressure is determined from the set pressure P1. By performing combustion by outputting a combustion command to a low boiler, backup combustion is performed in which the steam pressure of the boiler is higher than the set pressure P1, and then the operation priority is changed. And wherein the door.

Invention of Claim 2 WHEREIN: In the said multi-can installation boiler, a unit control apparatus is at the time of the operation priority change process,
1. 1. Back-up combustion is performed in which the steam pressure of the boiler is made higher than the set pressure P1 by outputting a combustion command to the boiler whose steam pressure is lower than the set pressure P1 to cause combustion. Next, select one of the boilers that will raise the operating priority, and change the operating priority of the selected boiler to the next level.
3. In the case where the boiler is burned after the rank change, if the steam pressure of the boiler is lower than the set pressure P2, combustion is performed until the boiler becomes higher than the set pressure P2,
4). After detecting that the steam pressure value of the boiler has become higher than the set pressure P2, control is performed to shift to a step of changing the operation priority of the next boiler.

  The invention according to claim 3 is, in the multi-can installation boiler, selects a boiler that performs combustion after changing the operation priority from the number of boilers that are burning at the start of the operation priority change process, Control is performed to perform backup combustion only for a boiler that performs combustion after changing the priority order and has a steam pressure value lower than the set pressure P1.

As described above, the boiler that was in the cold can state is preheated before changing the operation priority order, so that the time from the output of the combustion command to the start of steam supply can be shortened. The time required for the step of changing the priority order can be shortened.

  By implementing the present invention, there is no shortage of steam supply when changing the operation priority of boilers installed in multiple cans, and the time required for the process of changing the operation priority can be shortened. . Therefore, even if hunting occurs in which the boiler repeatedly starts and stops in a short time, the hunting phenomenon can be immediately terminated.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a flow sheet showing the installation status of a boiler that implements the present invention, FIG. 2 is a flowchart of control in one embodiment, and FIG. 3 is a status showing a change status of operation priority of each boiler in one embodiment. It is explanatory drawing. In this embodiment, six boilers 1 are installed in parallel, and the boilers are named boiler A, boiler B, boiler C, boiler D, boiler E, and boiler F in order. Steam piping from each boiler is connected to the steam header 4, and the header pressure detection device 3 is provided on the steam header 4. The operation command for each boiler 1 is output from the number control device 2 connected to each boiler, and the number control device 2 is also connected to the header pressure detection device 3.

Each boiler 1 is provided with a boiler operation control device 5, and the boiler operation control device 5 is connected to the number control device 2 through a signal line. The operation of the boiler is performed based on a command output from the unit control device 2 to the boiler operation control device 5. In each boiler, the boiler operation is controlled by the boiler operation control device 5 controlling the operation of each device of the boiler 1. . When the boiler operation control device 5 receives a combustion command from the number control device 2, it starts combustion of the boiler. When starting combustion, first perform pre-purge to send only air into the combustion chamber and ventilate the combustion chamber, then start the combustion by performing the ignition process, and generate steam by heating the boiler water in the boiler I do. When the boiler operation control device 5 receives a stop command from the number control device 2, combustion of the boiler is stopped. When stopping the combustion of the boiler, the fuel supply is stopped to stop the combustion, and then the post-purge for ventilating the combustion chamber is performed to stop the operation. In addition, each boiler 1 is provided with a boiler pressure detection device 6 that detects the steam pressure in each boiler, and the boiler pressure detection device 6 and the boiler operation control device 5 are connected by a signal line. The boiler pressure value detected by the boiler pressure detection device 6 is sent to the unit control device 2 via the boiler operation control device 5.

  The number control device 2 calculates the required steam amount based on the steam pressure value detected by the header pressure detection device 3, and outputs a combustion command to the required number of boilers. Each boiler has an operating priority, and when the steam pressure value decreases and the required steam volume increases, the number of combustion units increases by outputting combustion commands in order from the boiler with the highest operating priority, and the steam pressure When the value rises and the required steam amount decreases, the number control according to the required steam amount is performed by outputting the combustion stop command in order from the boilers with the lowest operation priority to reduce the number of combustion. The operation priority is changed every 24 hours, the integrated value of the combustion time is calculated for each boiler, and the operation priority is changed so that the next operation priority becomes higher as the combustion time is shorter. .

  FIG. 3 is a time chart showing an example of the situation of steam pressure value change, operation priority, and combustion command output of each boiler when the operation priority is changed. The operation priorities in FIG. 3 are as follows: boiler A from 1st to 6th, boiler B from 2nd to 5th, boiler C from 3rd to 4th, boiler D 4th It is assumed that the boiler E is changed from the fifth place to the second place, and the boiler F is changed from the sixth place to the first place. Initially, combustion commands are output to two units, boiler A and boiler B, and combustion commands are not output to the other boilers. The boiler that is not performing combustion has a low temperature because the combustion stop time is long, and the boiler pressure detected by the boiler pressure detection device 6 is low.

  The control at the time of changing the operation priority will be described based on the flowchart of FIG. 2 and the time chart of FIG. When the change of the operation priority is started, the number control device 2 detects the number of boilers that are currently burning in S1 which is the first step of the operation priority change process, and applies it to L. In the embodiment, it is assumed that the number of boilers that are determined by the header pressure detected by the header pressure detection device 3 is two. Therefore, L = 2 here. The value of L is used in the next step S2. In step S2, a boiler for performing backup combustion is selected. In the backup combustion, in order to enable the boiler that has started combustion to supply steam in a short time, when the boiler is in the cold can state, the steam pressure in the boiler before changing the operation priority is set to a certain level (set pressure P1). The boiler is burned until it becomes. In step S2, the boiler that performs the backup combustion is determined. When L = 2, the boiler having the next operation priority of 2 or less is set as the backup combustion target boiler. In the number control device 2, the pressure of the boiler that performs backup combustion, here, the pressure of the boiler E and the boiler F is confirmed. If the pressure in the boiler is less than the pressure P1, backup combustion is performed in step S4. As described in FIG. 3, since the steam pressures of the boiler E and the boiler F are lower than the pressure P1, the combustion of the boiler E and the boiler F is started from time a. The pressure P1 is set to about the lower limit value of the pressure adjustment range, and backup combustion is performed until the pressure in the boiler detected by the boiler pressure detection device 6 becomes equal to or higher than the pressure P1. When the boiler internal pressure in the boiler E and boiler F becomes equal to or higher than the pressure P1, the process proceeds to step 5 to determine whether the backup preparation is completed. The backup preparation is performed in all the boilers whose new priority is L or less, and if there is a boiler that has not finished the backup combustion, the process returns to step S2 and loops until all the target boilers are completed.

  When the backup preparation is completed in all the boilers that were the targets of the backup combustion, the operation priority change is started. In step S6, N = 1 and M = the number of boilers + 1. In this embodiment, since the number of boilers is 6, M is 6 + 1 = 7. In the next steps S7 and S8, the operation priority is changed. The rank change is targeted for the boiler that will be Nth in the next term and the boiler that will be Mth in the next term. In the case of N = 1 and M = 7, it means that the boilers of the next and first 7th will be changed to the new rank, but since the 7th rank of the operational priority does not exist, only the 1st rank is the new rank And Here, the operation priority of the boiler F is changed from the sixth place to the first place.

  In FIG. 3, the steam pressure of the boiler E and the boiler F has reached pressure P1 at the time b. Therefore, the backup preparation is completed at time b, and the operation priority of the boiler F, which becomes the new highest after time b, is set first. In the next step S9, the process branches depending on whether or not the boiler F, which is the first place, is burning. In the embodiment, the first operation priority order is the order in which combustion is performed, so the process proceeds to step S10. In step S10, if the steam pressure value of the boiler F is lower than the set pressure P2, the process loops between step 9 and step 10 until the pressure P2 is reached. As shown in FIG. 3, since the steam pressure value of the boiler F at the time point b is lower than the pressure P2, the process waits until the steam pressure value becomes the pressure P2. The value of the pressure P2 may be set to a value at which steam is supplied from the boiler 1 to the steam header 4, that is, approximately the same as the steam header pressure at that time.

  At this time, the boilers whose operation priority ranks first are two boilers, boiler A and boiler B, and combustion is performed by three boilers together with the second rank boiler B. However, since the steam pressure value of the boiler F is smaller than the pressure P2, steam is not supplied from the boiler F to the steam header 4, and steam is actually supplied from two boilers A and B. It has become. If the steam pressure value of the boiler F is equal to or higher than the pressure P2, the process proceeds to step S11. In the next step S11, the process branches in the combustion state of the new M-th boiler. However, since M at the present time is 7, and there is no 7th boiler, it does not apply to the condition that the new 7th boiler is burning. Therefore, the process proceeds to step S13 as it is. In step S13, if all boilers have been changed to the next order, the operation priority order is changed. If there is a boiler that has not been changed, the values of N and M are set to N = N + 1 and M = M in step S14. Change to -1. At this time, since the change to the next rank of all the boilers has not been completed yet, the process proceeds to step S14 on the NO side, and N = 1 and M = 7. Thus, N = 2 and M = 6. Then, the process returns to step S7.

Boiler E, the new second-ranked boiler, is boiler A, and boiler A, the sixth-ranked boiler, is the boiler A operating priority from No. 5 to No. 2 at Steps S7 and S8. Change the operating priority from 1st to 6th. This is the position of time c in FIG.
In the embodiment, since the first and second boilers are burned, boiler E, which has been changed from the old 5th place to the new 2nd place, burns and changes from the old 1st place to the new 6th place. The boiler A in which the change has been made stops combustion. Since the new second-ranked boiler E is burning, a loop is performed until the steam pressure value of the boiler E reaches the pressure P2 in steps 9 and 10. If the steam pressure value of the boiler E becomes more than the pressure P2 at the time d of FIG. 3, it will transfer to the following step S11. In step S11, if the new 6th boiler A is burning, the process proceeds to step 12. However, since the new 6th boiler A has stopped combustion, the process jumps to step S13.

  Even at this stage, since the change to the next rank of all the boilers has not been completed, N = 2 + 1 = 3 and M = 6-1 = 5 are set in step S14, and the process returns to step S7. In the current step 7 and step 8, the operation priority of the boiler D is changed from the fourth place to the third place, and the operation priority of the boiler B is changed from the second place to the fifth place. This is the portion of time d in FIG. In the boiler B, the combustion priority is changed to the combustion stop by changing the operation priority. In the case of boiler D, there is no change in the combustion state before and after the operation priority change, and the combustion is still stopped.

  In this loop, the control is performed for the new third-ranked boiler D and the new fifth-ranked boiler B. However, since the third rank in the operation priority order is the rank in which combustion is stopped in this embodiment, In the determination, the answer is NO, and the process jumps to step S13 as it is. In the next step S14, since N = 3 + 1 = 4 and M = 5-1 = 4, the operation priority of the last remaining boiler C at time e in FIG. 3 is changed from third to fourth. To do. The fourth place is also the order in which the combustion stops, so at the branch of step S9, it becomes NO and jumps to step S13. This completes the change to the next rank for all the boilers, and the operation priority change process ends.

  As described above, by heating the boiler that was in the cold can state before the operation priority change process, when the operation priority is actually changed, the newly started boiler starts steam The time to wait until the supply is started can be shortened, and the time required for the operation priority changing process in which the steam pressure becomes unstable can be shortened.

  In this embodiment, the number of boilers that are burning is calculated at the start of the operation priority changing process, and the number of boilers that perform backup combustion is determined. Alternatively, the number of boilers that perform backup combustion may be input in advance as a set value, and the number of boilers that perform backup combustion may be a fixed value each time.

The flow sheet which showed the installation situation of the boiler in one example of the present invention Control flow chart in one embodiment of the present invention State explanatory drawing which showed the order change situation at the time of operation priority change in one example of the present invention

Explanation of symbols

1 boiler
2 Number control device
3 Header pressure detector
4 Steam header
5 Boiler operation control device
6 Boiler pressure detection device

Claims (3)

A multi-can installation boiler consisting of a plurality of steam boilers and a unit control device that outputs operation instructions to each boiler. The unit control device sets an operation priority for each boiler, and based on the operation priority In the multi-can installation boilers, which select boilers that output combustion commands and the operation priority is changed regularly, each boiler has a pressure detection device that detects the steam pressure value in each boiler. The unit control device detects the steam pressure value in each boiler before changing the operation priority during the operation priority change process, and outputs a combustion command to the boiler whose steam pressure is lower than the set pressure P1. Multiple-can installation characterized by performing backup combustion in which the steam pressure of the boiler is higher than the set pressure P1 by performing combustion and then changing the operation priority Ira. In the multi-can installation boiler according to claim 1, the unit control device is in the operation priority changing step,
1. 1. Back-up combustion is performed in which the steam pressure of the boiler is made higher than the set pressure P1 by outputting a combustion command to the boiler whose steam pressure is lower than the set pressure P1 to cause combustion. Next, select one of the boilers that will raise the operating priority, and change the operating priority of the selected boiler to the next level.
3. In the case where the boiler is burned after the rank change, if the steam pressure of the boiler is lower than the set pressure P2, combustion is performed until the boiler becomes higher than the set pressure P2,
4). A multi-can installation boiler, characterized in that after detecting that the steam pressure value of the boiler has become higher than the set pressure P2, the control is shifted to the step of changing the operation priority of the next boiler.   In the multi-can installation boiler according to claim 1 or 2, the operation priority is changed by selecting a boiler that performs combustion after changing the operation priority from the number of boilers that are burning at the start of the operation priority change process. A multi-can set-up boiler that performs backup combustion only for a boiler that performs combustion later and has a steam pressure value lower than a set pressure P1.

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