JPS6021292B2 - Burner control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a burner control device that uses a computer to select fuel for starting a boiler and fuel for steady operation (hereinafter referred to as main fuel) when starting up a power generation plant.

During operation of a thermal power plant, if some abnormality occurs in the main machinery or auxiliary machinery such as a boiler or turbine and the operation cannot continue, a plant trip is performed for the purpose of safety and equipment protection.

Currently, this plant trip is almost automatically performed because the system of a thermal power plant is complex and a degree of urgency is required. When such a trip occurs, the operator is required to quickly determine the cause of the abnormality and restore power supply as quickly as possible, which places a heavy burden on the operator.
In order to restore power quickly, it is essential to quickly raise the temperature of the boiler-generated steam supplied to the turbine. To do this, control of the fuel that serves as the heat source, especially the fuel combustion burner (
The ignition control of the burners (hereinafter referred to as burners) plays an important role. Figure 1 shows an example of a fuel system diagram in a thermal power plant.

The amount of fuel (hereinafter referred to as flow rate) of the starting fuel 1 or the main fuel 2 is generally controlled by an AP (automatic load control device). That is, when a command for "starting fuel control pressure side" is given to the APC using the starting fuel valve 3, the APC maintains the inlet pressure of the starting fuel burners) to 10 at a predetermined pressure. The supply flow rate of the starting fuel 1 is adjusted by the starting fuel valve 3 in the same way, and when a command for "starting fuel control flow rate side" is given, the flow rate is supplied to match the predetermined rise in boiler generated steam temperature. Control quantity. These control sequences are executed as a program in APC.
The fuel flow rate is controlled by opening and closing the startup fuel valve 3 according to the program. The former is called "pressure control" and the latter is called "flow control", and the same applies to the main fuel. Note that since the APC has a programmed flow rate supply amount, the flow rate supply amount cannot be varied within the APC as the plant environment changes. For this reason, the amount of V supplied can be adjusted externally.
Starting fuel burner 7 installed in the boiler furnace 15
10 and main fuel burner 1 1 to 14 are all two 1
It is common practice to ignite and extinguish fires in groups (1 bear).

Furthermore, when these burners are ignited and extinguished, the inside of the boiler furnace must be uniformly warmed, so it is necessary to carefully control which burners are to be ignited and extinguished. For example, when the startup fuel burner 7 is in the combustion state, the following two
It is desirable to ignite the burner 10 in order to ignite the bare eye. When burner 9 or burner 8 is ignited, only one side of the furnace is heated, causing a problem that the temperature inside the furnace is not uniform. In this way, a type of table called a burner pattern is created to determine which burners are to be ignited or extinguished based on the burner combustion state, and ignition or extinguishment operations are performed based on the burner pattern. In addition, in large-capacity thermal power plants, the number of burner patterns consisting of dozens of bare burner combinations becomes enormous, and the starting fuel 1 is switched to the main fuel 2 (hereinafter referred to as fuel switching). )
If additional patterns are added, the burden on the operator during manual operation becomes extremely heavy. Next, the procedure for ignition operation will be explained using FIG. 2.

Figure 2 shows the relationship between the burner inlet fuel oil pressure P and the change in the fuel flow rate Q. When the opening degree of the fuel valve 3 is constant, that is, the flow rate is constant, as the number of burners increases, the burner inlet fuel oil pressure This shows that the amount decreases.
This characteristic is roughly the same for both the starting fuel and the main fuel. Characteristic curve 16 is 1 bear, characteristic curve 17 is 2
Similarly, 18 and 19 are characteristic curves of 3 and 4 bears. When igniting the burner, unless the fuel oil pressure at the burner inlet exceeds a specified value, it will not be possible to ignite the burner due to combustion effects. This pressure value is called ignition pressure, and in the initial ignition of the first bear, ignition is performed at a pressure that exceeds this ignition pressure to some extent.
This is because the fuel flow rate in the first burner is low, so when the first burner is ignited, the fuel oil pressure at the burner inlet suddenly drops.
This is because there is a risk of plant tripping. In other words, in general, the flow rate is set relatively high when igniting the first bear, and this ignition pressure is high. Therefore,
If the flow rate is controlled at the time of the first ignition, the flow rate flowing into the first ignition burner bear (discharged to the furnace) will be very large, and the burner may burn out due to the heat, so the ignition of the first bear is pressure controlled. It is carried out in This pressure control is 2
It is normal to carry out bare ignition. Incidentally, for the sake of explanation, a case will be described below in which flow rate control is performed from the first bear. When the flow rate is controlled, the flow rate naturally increases gradually, and as a result, the burner inlet fuel oil pressure increases as shown by the characteristic curve 16. And the ignition pressure is PH
When it reaches , ignite the second bear. When ignited, the pressure is P
It decreases from H to P. This will also be done on the aircraft after the 2 bear ignition.

Next, when the boiler generated steam temperature rises abnormally, the APC adjusts the fuel flow rate by setting the fuel reduction externally. Then, as shown by curve 18, the fuel oil pressure at the burner inlet decreases, and when it finally reaches PL, one bear is extinguished.

This increases the pressure from PL to P3. The number of fuel oil pressure burners is controlled by the combustion effect due to low oil pressure,
This is to protect the burner from overheating due to high oil pressure (excessive fuel flow rate). As described above, temperature increase control of boiler-generated steam is fuel control, which is essentially burner control, and ignition control plays an important role in temperature increase. In the fuel control system described above, startup after a plant trip (hereinafter referred to as rapid startup) is performed using exactly the same procedure as startup after a long stop without an accident (hereinafter referred to as normal shutdown). There is.

That is, the procedure for general burner control is as follows. (i) Fully close the main fuel valve 4 and cut off the main fuel 2.

Set the startup fuel control to the pressure side, set the pressure control, and open the startup fuel valve 3. As a result, the fuel oil pressure for starting the burner inlet finally reaches the ignition pressure, ignites the first burner, and similarly ignites the second burner according to the burner pattern. (ii)
The starting fuel control is set to the flow rate side, and the number of burners is controlled by igniting and extinguishing the burners based on changes in the programmed starting fuel flow rate, that is, changes in pressure.

(iii) As the temperature in the boiler can rises and the load of boiler-generated steam increases, the starting fuel becomes insufficient, so a fuel switch is performed.

That is, the main fuel control is set to pressure control and the main fuel valve 4 is opened. As a result, the main fuel oil pressure at the burner inlet reaches the ignition pressure, and one bear among the main fuel burners 11 to 14 is ignited based on the burner pattern. Next, extinguish the starting fuel burner (for example, 8 when igniting 12) at the point where it was ignited. In such a process, since APC fuel control controls the flow rate based on the sum of the starting fuel 1 and the main fuel 2, the starting fuel naturally decreases when the main fuel burner is ignited. Therefore, the number of starting fuel burners for extinguishing operation is controlled by reducing the starting fuel oil pressure. After igniting the second main fuel burner, the flow rate control of the main fuel 2 is performed, all starting fuel burners are extinguished, and the fuel switching is completed. Only after this fuel switching is completed is burner control based on main fuel competition. The above is a part of the burner operation procedure up to the main fuel vehicle dawn control, and if you include the operations of other devices related to this, it is only a part of the operation.

FIG. 3 shows a conventional general burner control block diagram.
That is, the input data collection section 31 inputs data related to burner control, converts it into a signal that can be calculated by the input data collection section 31, and outputs it to the starting fuel burner judgment element 39 (hereinafter referred to as the first judgment element 39) and the main fuel. Burner judgment element 40 (
Hereinafter, it will be referred to as the second judgment element 40. ) to transmit the data signal. The first judgment element 39 selects only the data signals necessary for the starting fuel burner, and has logic that only handles ignition and extinguishing of the starting fuel burner among the above steps, and detects the ignition and extinguishing timing. An ignition and extinguishing command is given to the startup fuel burner operation section 34, and this operation section 34 converts the automatic burner control device 36 (hereinafter referred to as ABNC 36) into a signal that can be operated, and outputs an operation signal to the ABNC 36 to start the burner. ignite and extinguish the fire. Similarly to the first determining element 39, the second determining element 40 inputs only data signals necessary for the main fuel burner, and operates exclusively for igniting and extinguishing the main fuel burner. As mentioned above, when starting up a plant, the inside of the boiler must be heated uniformly, so it is necessary to ignite and extinguish the burners using various predetermined burner patterns, and the fuel switching operation is particularly complicated. , together with the post-plant trip, significantly increases the operational burden on the operator and inevitably lengthens the recovery time (start-up time). Fuel switching involves repeating the operation of igniting the main fuel burner and extinguishing the starting fuel burner, and due to the difference in calorific value between the starting fuel and the main fuel, this ignition and extinguishing appear as step-like energy changes, causing the boiler to burn. This results in the disadvantage that the temperature rise characteristics of the steam and steam are not stable. Therefore, although it has been desired to start the boiler using phosphorous as the main fuel from the start of the plant without any fuel switching, this has been difficult to realize due to safety concerns. That is,
Due to defects in the environmental conditions inside and outside the boiler can, gases such as NOx may be generated due to incomplete combustion of fuel, which requires a large amount of cost for safety measures. Moreover, the main fuel has poor fuel efficiency and high ignition failure rate compared to the starting fuel, so incomplete combustion is redundant. Therefore, at startup,
Good quality startup fuel is supposed to be used, which increases fuel costs. In addition, during normal operation, the load on the boiler is naturally large, and since it requires so much fuel that it is not a problem compared to when starting up, the main fuel burner tip is designed to be larger than the starting fuel burner, so it is absolutely necessary to This consumes a large amount of energy, and when the inside of the can is cold, it heats up rapidly, creating transient thermal stress that may cause cracks in the steam pipes, etc. The present invention has been made in view of the above-mentioned circumstances, and determines from the vertical state (conditions) of the Y power plant whether or not the main fuel can compete exclusively from the initial fuel injection for plant startup, and starts the plant using startup fuel. The present invention provides a burner control device that enables pre-combustion of the main fuel depending on the state of the plant by determining whether it is necessary to start exclusive combustion of the main fuel or whether it is possible to start exclusive combustion of the main fuel. The configuration of the present invention is shown in FIG.

In FIG. 4, 37 is a group of fuel combustion burners, and 36 is an automatic burner control device ABNC that constantly monitors the combustion status of these burners and controls ignition and extinguishing of the burners based on instructions from a computer 38. Further, 31 to 35 are each element in the computer 38 for giving ignition and extinguishing commands to the ABNC 36,
It is divided into blocks by function. The input data collection unit 31 is a computer that receives multiple inputs 41 indicating the plant status and the status of equipment other than the ABNC 36, and multiple inputs 42 indicating the status of the ABNC 36 itself and the combustion status of the burner in digital and analog quantities, and constantly monitors them. The converted signal 43 is exchanged into a signal (information) that can be processed within the processing element 32, and the converted signal 43 is transmitted to the judgment element 32.

The judgment element 32 is composed of a kind of logic, and constantly monitors the conversion signal 43 from the input data collection section 31, checks the burner ignition and extinguishing timing, and makes a predetermined decision when the appropriate timing is detected. An ignition permission signal or extinguishing permission signal for igniting or extinguishing is calculated based on the burner pattern. It also calculates a logic signal 44 necessary for determining which of the startup combustion burner and the main fuel burner to ignite. Then, the signal 44 is transmitted to the fuel selection determining section 33. The fuel selection determining unit 33 selects the starting fuel burner and the main fuel burner based on a plurality of fuel selection conditions, and based on the selection, ignites the starting fuel burner operating unit 34 or the main fuel burner operating unit 35. A command signal 45 or 46 for extinguishing the fire is given. 34 and 35 convert the command signals 45 and 46 to ABNC 36 to enable assist operation, and output 45 or 46 directly as starting fuel burner operation signal 47 or main fuel burner operation signal 48 to ABNC 36. do.

The ABNC 36 controls the startup fuel burner or main fuel burner operation for the burner group 37 based on the operation signal 47 or 48, and feeds back the combustion state of the burner group 37 to the input data collection section 31 in the computer 38. The computer 38 confirms the burner operation results. FIG. 5 is a logic circuit for explaining the function corresponding to the fuel selection determination section 33 in FIG. 4. Signals 61 to 63 are fuel selection condition signals for determining the propriety of main fuel purification, and these are connected to an AND gate 51, and the output x of this AND gate is sent to the main fuel burner ignition gate 53, and x is inverted. A signal is input to the starting fuel burner ignition gate 52.
Among the fuel selection condition signals, signal 61 indicates that the temperature inside the boiler can is above the specified value, signal 62 indicates that the temperature on the turbine side is above the specified value, and signal 63 indicates that the main fuel shunt device (hereinafter referred to as MFT) has tripped. These are signals that are established within a specified time. Further, the signal 63 continues to count time with the time point at which the MFT trips as zero. Next, the signal 64 is a plurality of interlock conditions for ABNC, such as ABNC computer operation enabled, MFT reset, etc. When all of these interlock conditions are satisfied, the signal 64
The signal is established. A signal 65 indicates a plurality of ignition conditions for igniting the starting fuel burner, such as permission to ignite the starting fuel burner, and a signal 66 similarly indicates a plurality of ignition conditions for igniting the starting fuel burner, such as permission to ignite the main fuel. 2 shows a plurality of ignition conditions at , and all of them are composed of signals such that all of the plurality of ignition conditions are satisfied, similar to the signal 64. signal 6
4 and 65 are input to the starting fuel burner ignition gate 52 together with a signal obtained by inverting the main fuel input signal x, and from these conditions, the starting fuel burner ignition command signal 45 is obtained. The signals 64 and 66 are also input to the main fuel burner ignition gate 53 to obtain the main fuel burner ignition command signal 46. By the way, as to what fuel selection conditions should be selected to determine whether or not the main fuel poisonous moth is allowed to be used, we are currently studying burner control using a computer. It was found that there is no problem even if the boiler is started with the fuel level.

In other words, incomplete combustion of the main fuel, including ignition failure, is due to the poor combustion effect caused by the cold temperature inside the boiler can, and even during normal startup, the temperature inside the boiler can rise to some extent. At that point, the fuel is switched and the main fuel becomes pure phosphorus. FIG. 6 shows how the temperature rise at various parts inside and outside the boiler can changes with time when the fuel is changed stepwise.

Curve 72 indicates that the absolute amount of fuel is larger than curve 71. Generally, when the amount of fuel is changed in steps, the absolute value of the temperature rise will settle down to a certain temperature T, assuming that the ambient temperature is constant. Therefore, if the fuel amount is changed stepwise when the temperature of each part inside and outside the boiler can is constant, △t
When the time has elapsed, the temperature becomes T2. If you change the fuel when the aircraft is at L, it will be at L after Δt has elapsed. It is clear that the difference between T2 and T, and the difference between T4 and L appear as a temperature increase, and T2-T,>T4-.
The larger the temperature increase, that is, the rate of temperature change, the more adverse thermal effects will be exerted on various parts inside and outside the boiler can as heat W6. In other words, in a constant fuel change, the higher the temperature of each part inside and outside the boiler can, the smaller the temperature change P rate, so the thermal stress value caused by the cracking of each part inside and outside the boiler can, such as a steam tube furnace, is small. In other words, it is possible to safely start up with less life consumption. Therefore, signal 61 has multiple inputs representing the temperature inside the boiler can, signal 62 has multiple inputs representing the temperature inside the turbine, and regarding signal 63, it is impossible to input all main fuel vehicle bran judgment conditions into the computer. Also, in the case of a trip during operation, the heat generation source disappears and the temperature inside and outside the boiler can gradually decreases, and the rate is not constant. Therefore, a signal indicating that the MFT trip is within the specified time is given.

Now, when a trip accident occurs during operation of a power generation plant, the MFT generally trips and all burner groups 37 are automatically extinguished.

Then, the ABNC 36 detects this and feeds back a signal 42 to the input data collection section 31. In addition, the status of each related equipment associated with a trip is also expressed as a plant status input signal 41.
The data is input to the input data collection section 31 as a. As described above, these input signals are transmitted to the fuel selection determining section 33 via the input data collecting section 31 and the determining element 32 to create the signals 61 to 66. That is, if the temperature inside the boiler can is above the specified value and the temperature on the turbine side is also above the specified value, the signals 61 and 62 are established at the time of tripping, and the condition signal 6 is established within the specified time after the MFT trips.
3 starts counting at the judgment element 32 with the trip as the starting point, so the signal 63 is also established, and the output x of the AND gate
In other words, the main fuel vehicle dawn condition is satisfied. However, since the MFT is in the trip state, the interlock condition 64 of the ABNC 36 is not satisfied, and the starting fuel burner ignition command 45 of the starting fuel burner ignition gate 52 is also not the main fuel burner ignition command 46 of the main fuel burner ignition gate 53. is also not established, the computer 38 does not issue an ignition command to the ABNC 36. Next, when performing a rapid start-up based on the operator's will, M
``T reset, select ABNC computer operation, and then AB
By canceling the interlock condition for NC 36, signal 64 is established.

The determination element 32 determines the ignition timing based on the ABNC 36 and the state of equipment other than the ABNC 36 and the plant state, and when the ignition timing is established, a fuel selection determination section sends a signal that the starting fuel burner ignition condition 65 or the main fuel burner ignition condition 66 is established. 33. If the signal 63 is valid within the specified time after the trip, and the temperature inside the boiler can and the turbine side are both maintained above the specified temperature, all main fuel competitive conditions are satisfied, and the AND gate is activated. The output x holds true. Therefore, the output of the main fuel burner ignition gate 53, that is, the main fuel burner ignition command 46 is established, and by giving the main fuel/burner ignition operation signal 48 to the ABNC 36 via the main fuel burner operation section 35, the ABNC 36 Light the burner. On the other hand, the output of the starting fuel ignition gate 52, that is, the starting fuel burner' ignition command 45 is not satisfied because it is the inversion of x, and the starting fuel burner ignition operation signal 47 is not provided. Next, if a specified time has elapsed after the trip, or if the temperature inside the boiler falls below the specified value, or if the temperature on the turbine side falls below the specified value, one of the signals 61, 62, and 63 will fail. Therefore, the output x of the AND gate 51 to which they are connected is not satisfied. Therefore, the output of the main fuel burner ignition gate 53, that is, the main fuel burner ignition command signal 46 is not established, and the main fuel burner ignition operation signal 48 is not provided. Further, the output of the starting fuel burner ignition gate 52, that is, the starting fuel burner ignition command 45 is established if 64 and 65 are satisfied, and a starting fuel burner ignition operation signal 47 is sent to the ABNC 36 via the starting fuel burner operating section 34. By giving ABN
C36 ignites the starting fuel burner. In the case of normal startup, since the power generation plant has been stopped for a long time, the signals 61 to 63 will naturally fail, so the startup fuel burner must be ignited. As described above, according to the present invention, since fuel is selected according to the plant state, normal startup is easily possible.

During quick startup after a trip, operations from the startup fuel burner to fuel switching can be omitted, which reduces startup operations and improves reliability, shortens the time required for startup, and enables early power restoration. possible. Moreover, it is economical because no expensive starting fuel is used.

[Brief explanation of drawings]

Fig. 1 is a diagram of a boiler startup system, Fig. 2 is a characteristic diagram of a general burner control method, Fig. 3 is a block diagram of a conventional burner control device using a computer, and Fig. 4 is a diagram of a burner control device of the present invention. The block diagram, FIG. 5 is a logic circuit diagram for explaining the fuel selection determining section which is the main part of the present invention, and FIG. 6 is a characteristic diagram of the burner control device of the present invention. 1...Fuel system for startup, 2...Main fuel system, 3...Fuel valve for startup, 4...Main fuel valve,
5... Fuel pump for starting, 6... Main fuel pump, 7-10... Fuel burner for starting, 11-
16... Main fuel burner, 15... Boiler furnace, 16-19... Fuel burner inlet fuel oil pressure change curve, 31... Input Data collection section, 32... Judgment element, 33... Fuel selection judgment section, 34... Starting fuel burner operating section, 35... Main fuel burner operating section , 36...
...Automatic burner control device (ABNC), 37...
・Burner group, 38... Calculator, 39...
・Start-up fuel burner determination element, 40...Main fuel burner determination element, 41...Plant status and ABN
Input indicating the status of equipment other than C, 42...ABNC
Input indicating the state and burner combustion state, 43... Signal that can be processed in the computer, 44... Burner selection signal, 45.
...Start-up fuel burner operation command signal, 46...
...Main fuel burner operation command signal, 47...Fuel burner operation signal for starting, 48...Main fuel burner operation signal, 51...AND gate, 52...Fuel burner for starting Ignition gate, 53... Main fuel burner ignition gate, {61. ．． ...・The temperature inside the boiler can is higher than the specified value,
62... Turbine temperature specified value or higher, 63...
・Within specified time after MFT trip} Main fuel observance condition, 64
...Interlock condition, 65...Start-up fuel burner ignition condition, 66...Main fuel burner ignition condition, 71, 72... Fuel in steps Temperature rise curve when changing. Key 1 Figure 2 Figure 3 Figure 4 Figure 5 Leopard Figure 6

Claims (1)

[Claims] 1. When starting the boiler, the starting combustion burners are ignited in a predetermined order, and when the number of ignited starting combustion burners reaches the predetermined number and the temperature inside the boiler can exceeds a predetermined specified value, In a burner control device that controls the main fuel burners to be ignited in a predetermined order and the startup combustion burners to be extinguished in a predetermined order, a status signal necessary for starting the boiler can be input and processed within a computer. an input data collection unit that converts into a signal, and calculates a logical signal necessary for determining at least which of the startup combustion burner and the main fuel burner to ignite based on the converted status signal, and ignites the same; a determination element that determines the timing of ignition and calculates an ignition permission signal; and a determination element that selects the main fuel burner when the temperature inside the boiler can is equal to or higher than a specified value based on the logic signal obtained by this determination element; is less than a specified value, a fuel selection determining unit that selects the startup combustion burner; and an operating unit that issues an ignition command to the selected burner based on a selection signal from the fuel selection determining unit and the ignition permission signal. and an automatic burner control device that ignites the burner selected based on the ignition command.