JP4129818B2 - Boiler automatic control method and apparatus - Google Patents

Description

  The present invention relates to a boiler automatic control method and apparatus, and in particular, sets a ratio between a coal supply flow rate and a fuel oil supply flow rate for a co-fired coal fired boiler according to a load, and in accordance with this setting, coal powder and fuel for the boiler The present invention relates to a boiler automatic control method and apparatus suitable for controlling the supply flow rate of oil.

  When controlling a co-fired coal fired boiler installed in a thermal power plant or the like, conventionally, the ratio of the coal supply flow rate to the boiler and the fuel oil supply flow rate is set based on the generator output command, and the coal supply flow rate command is set according to this setting. The fuel oil supply flow rate command is generated, the coal powder is supplied from the mill to the boiler coal burner according to the coal supply flow rate command, and the fuel oil is supplied to the boiler fuel oil burner according to the fuel oil supply flow rate command. And supplying air to the mill. In this case, the boiler is supplied with air from the forced draft fan via the air heater, and the mill is mixed with the air from the primary ventilator and the air heated by the air heater from the primary ventilator. The supplied air is supplied. That is, air in which warm air and cold air are appropriately mixed is supplied to the mill, and coal powder is pumped to the boiler by the pressure of this air. Further, the exhaust gas in the boiler is exhausted to the outside air through an induction fan and a chimney.

  That is, the boiler is equipped with a primary ventilator, a forced ventilator, an induction ventilator, etc. as auxiliary equipment for air intake / exhaust, etc., and any of these auxiliary equipments has some cause. When the operation is stopped by the above-described control, so-called run-back control is performed to quickly and safely lower the boiler load up to a load that can be operated by the remaining auxiliary machines. Here, when blown to the mill is performed by two primary ventilators, if one primary ventilator fails, control is performed to reduce the load to 50%, which is half of the rated load. Yes.

  Further, as this type of technology, for example, in a co-fired coal fired boiler, when any one of a plurality of mills is stopped, the boiler load command is narrowed down by the amount of load loss corresponding to the stopped mill. Compared with the one that automatically performs the mill run back according to the boiler load command (see Patent Document 1) or the load setting signal and the power generation amount command, whether or not to continue the normal operation based on the comparison result An example is one that determines whether or not to enter the back operation (see Patent Document 2).

JP-A-10-122549 (2nd to 5th pages, FIG. 1 and FIG. 2) JP-A-11-294704 (pages 3 to 4, FIG. 1)

In the prior art, regarding the load setting at the time of runback, the operation at the time of mixed combustion is not considered, and after the runback operation when one of the two primary ventilators fails, the setting is uniformly 50% load. Therefore, even when the load operation at 50% or more is possible, the load is always reduced to 50%. For this reason, it was not possible to secure a large amount of power generation after the runback operation.
In Patent Documents 1 and 2, no consideration is given to securing a large amount of power generation during the run-back operation for lowering the boiler load. That is, in Patent Document 1, the boiler load command is narrowed down by the amount of load loss according to the trip of the mill, and the mill run back is automatically performed, but the reduction of the combustion energy of the boiler is suppressed during the mill run back. Control is not performed. On the other hand, in Patent Document 2, when a part of a plurality of auxiliary machines is stopped, a load setting signal commensurate with the capacity of the remaining auxiliary machines is compared with a power generation amount command value. When the power generation command value is smaller, normal operation is continued, and when the power generation command value is larger than the load setting signal, the runback operation is performed. No control is performed to suppress the decrease.
The subject of this invention is suppressing the fall of the fuel energy at the time of boiler load fall control, and suppressing that the electric power generation amount falls as a result.

In order to solve the above-described problems, the present invention is directed to conveying coal powder from a mill by air supplied from a plurality of auxiliary machines, supplying the coal powder to the coal burner, and supplying the fuel oil supplied from the fuel oil supply means to the fuel oil burner. When the generator is driven by the steam generated in the co-fired coal fired boiler and generated by the steam generated in the co-fired coal fired boiler, power generation is performed based on the total fuel supply flow rate corresponding to the generator output command. In a boiler automatic control method for a co-fired coal fired boiler that distributes and controls a coal supply flow rate to be supplied to a fuel oil and a fuel oil supply flow rate to be supplied to the fuel oil burner according to a predetermined mixed combustion rate, when one has failed, to hold the fuel oil supply flow rate at immediately before the failure of the auxiliary device, setting the fuel oil supply flow rate to the holding as a command value, based on the finger command value Controls the fuel oil supply flow rate, the coal supply flow rate in immediately before the failure of the auxiliary equipment, without runback control when the coal less than the supply flow rate can be supplied by the remaining auxiliary, the remainder of the accessory Runback control is performed when the coal supply flow rate is greater than or equal to the supplyable coal supply flow rate, and when the runback control is performed, the retained fuel oil supply flow rate and the coal supply flow rate that can be supplied by the remaining auxiliary machine of the added value as a generator output command runback control, while generating a total fuel flow rate command corresponding to the power generator output command of the runback control, a detected value of the fuel oil supply flow rate of the coal supply flow rate The fuel oil supply flow rate corresponding to the obtained ratio is obtained by dividing the value by the added value of the detected value of the fuel oil supply flow rate and determining the ratio of the fuel oil supply flow rate to the total fuel flow rate command. Said subtracted from the total fuel flow rate command to set the command value of the coal feed rate, and controlling the coal supply flow rate based on the finger command value.

According to the boiler automatic control method for a co-fired coal fired boiler of the present invention, when at least one of the auxiliary machines fails, the fuel oil supply flow rate is controlled so as to maintain the fuel oil supply flow rate immediately before the failure of the auxiliary machine. since you are, that is, since the holds the fuel oil supply flow rate regardless of the setting mixed combustion ratio is set to the generator output command by adding coal feed flow rate can be supplied by the remaining auxiliary, at least setting co-firing Regardless of the rate, a decrease in fuel energy can be suppressed by the amount that maintains the fuel oil supply flow rate, and a decrease in power generation amount can be suppressed. In particular, since the runback control is not performed when the coal supply flow rate immediately before the failure of the auxiliary machine is less than the coal supply flow rate that can be supplied by the remaining auxiliary machine, power generation is performed even if at least one of the auxiliary machine fails. A decrease in the amount can be suppressed. Furthermore, runback control is performed when the coal supply flow rate is greater than or equal to the coal supply flow rate that can be supplied by the remaining auxiliary machinery, and when runback control operation is performed, the retained fuel oil supply flow rate and the coal that can be supplied by the remaining auxiliary machinery operation. The sum value with the supply flow rate is set as the generator output command, and the total fuel flow rate command is generated based on this. Because the ratio of the fuel oil supply flow rate to the total fuel flow rate command is calculated and the command value of the coal supply flow rate is set based on that ratio, the value is maintained rather than the conventional runback control. The decrease in the amount of power generation can be suppressed by the amount of fuel oil supplied.

Further, the boiler automatic control device of the present invention includes a coal supply means for conveying coal powder from a mill by air supplied from a plurality of auxiliary machines and supplying the coal burner to the coal burner, and a fuel oil for supplying fuel oil to the fuel oil burner. Based on the total fuel supply flow rate corresponding to the generator output command, the predetermined mixed combustion rate is determined based on the supply means, the coal supply flow rate supplied to the coal burner, and the fuel oil supply flow rate supplied to the fuel oil burner. And control means for controlling distribution according to the above, and runback control means for controlling the coal supply flow rate and the fuel oil supply flow rate when at least one of the auxiliary machines fails, and supplies the coal burner and the fuel oil burner. In the automatic boiler control apparatus for generating power by driving a generator with steam generated by burning coal powder and fuel oil to be burned in a co-fired coal fired boiler, , When at least one of said auxiliary fails to hold the fuel oil supply flow rate at immediately before the failure of the auxiliary device, setting the fuel oil supply flow rate to the holding as a command value, based on the finger command value The fuel oil supply flow rate is controlled, and when the coal supply flow rate immediately before the failure of the auxiliary machine is less than the coal supply flow rate that can be supplied by the remaining auxiliary machine, the runback control is not performed, and the remaining auxiliary machine is not performed. The runback control is performed when the coal supply flow rate is equal to or higher than the coal supply flow rate that can be supplied by the above-described operation, and when the runback control is performed, the retained fuel oil supply flow rate and the coal supply flow rate that can be supplied by the remaining auxiliary machinery and a generator output command the sum of the run-back control with, while generating a total fuel flow rate command corresponding to the power generator output command of the runback control, the detection value of the fuel oil supply flow rate By dividing the detected value of the charcoal supply flow rate by the added value of the detected value of the fuel oil supply flow rate, a ratio of the fuel oil supply flow rate to the total fuel flow rate command is obtained, and the fuel oil supply corresponding to the obtained ratio A flow rate is subtracted from the total fuel flow rate command to set a command value for the coal supply flow rate, and the coal supply flow rate is controlled based on the command value.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the combustion energy at the time of boiler load fall control falls, As a result, it becomes possible to ensure as much power generation amount as the fuel oil supply flow rate.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an automatic boiler control apparatus showing an embodiment of the present invention, FIG. 2 is a block diagram of a runback determination circuit, FIG. 3 is a block diagram of a runback load setting circuit, and FIG. It is a block block diagram which shows the relationship with an auxiliary machine.

  In FIG. 4, the boiler 3 is configured as a mixed-fired coal fired boiler, and a coal burner (not shown) and a light oil burner (not shown) as a fuel oil burner are installed in the boiler 3. Light oil 1 as fuel oil is supplied to the light oil burner, and coal powder is supplied to the coal burner from a mill 2 that processes coal into powder. Around the boiler 3, air heaters 4, 5, primary ventilators 6, 7, push-in are used as auxiliary machines for supplying air to the boiler 3 or the mill 2 and discharging exhaust gas from the boiler 3. Ventilators 8 and 9 and induction fans 10 and 11 are provided, and each of the induction fans 10 and 11 is connected to a chimney 14. Air 12 is supplied to the primary ventilator 6 and the pusher ventilator 8, and air 13 is supplied to the primary ventilator 7 and the pusher ventilator 9, and the air 12 and 13 supplied to the primary ventilators 6 and 7. Is sent to the mill 2 side as it is, and the rest is heated by the air heaters 4 and 5 and sent to the mill 2 side as warmed air. That is, the mill 2 is introduced with air in which cold air and warm air are mixed. When warm air and cold air are mixed and introduced into the mill 2, the coal powder is pushed into the boiler 2 by the pressure of the air.

  On the other hand, the airs 12 and 13 taken into the forced air ventilators 8 and 9 are respectively warmed by the air heaters 4 and 5 and then taken into the boiler 3 and used as combustion air. When fuel air is taken into the boiler 3, coal powder is combusted by the coal burner, light oil is combusted by the light oil burner, steam is generated by this combustion, exhaust gas is generated, and the generated steam generates thermal power plant. The steam turbine (not shown) is driven to generate electric power. On the other hand, the exhaust gas passes through the induction fans 10 and 11 and the chimney 14 and is discharged to the outside air.

  Here, in the case of a coal-fired boiler, the capacity of one primary ventilator is usually 50% of the rated load because two primary ventilators are used to supply all the air to the mill. Therefore, if one of the two primary ventilators stops, the plant cannot operate at the rated capacity, and the boiler load drop control reduces the load to the capacity of the remaining auxiliaries, in this case, 50%. Control operation (hereinafter referred to as run-back operation).

  However, in the present invention, a mixed fired coal fired boiler is used as the boiler 3, and when any one of the two primary ventilators 6 and 7 is stopped, the load of the stopped primary ventilator is compensated. In addition, the aim is to continuously burn light oil and to make the target load value at the time of the run-back operation 50% or more, and the specific contents of the boiler automatic control device will be described below.

  As shown in FIG. 1, the main control system of the boiler automatic control device includes a NOT circuit 61, an AND circuit 62, a runback load setting circuit 64, a low value selector 65, a boiler master controller 66, a combustion rate setting device 67, a fuel. Program generator 68, signal switch 69, divider 71, subtractor 73, multiplier 74, subtractor 76, proportional integrator 77, holder 79, subtractor 82, proportional integrator 83, function generator 85, light oil A flow rate detector 87, an adder 90, and the like are provided. A signal related to the X% runback operation 33 is input to the NOT circuit 61, and a signal related to the mixed combustion rate setting permission 60 is input to the AND circuit 62. A generator output command (MWD) 63 is input to the low value selector 65 and the runback load setting circuit 64, and a signal related to the X% runback operation 33 is input to the retainer 79, and proportional integration is performed. 77 coal supply flow rate command 78 is output from the from the proportional integrator 83 is adapted to diesel fuel supply flow rate command 84 is output. The light oil supply flow rate command 84 is input to the light oil flow rate adjustment valve 89 as a fuel oil supply flow rate command. The light oil flow rate adjustment valve 89 controls the flow rate of light oil in the light oil pipe 88 and follows the light oil supply flow rate command 84. The fuel oil supply means is configured to supply light oil to the light oil burner of the boiler 3. The coal supply flow rate detector 75 is configured as a coal powder supply flow rate detection means for detecting an actual supply flow rate of the coal powder pushed into the boiler 3 from the mill 2, and the light oil flow rate detector 87 passes through the light oil pipe 88. It is configured as a fuel oil supply flow rate detecting means for detecting actual light oil supply flow rates 70 and 81 of light oil.

  The main control system of the boiler automatic control device shown in FIG. 1 sets the ratio of the coal supply flow rate to the boiler 3 and the light oil (fuel oil) supply flow rate based on the generator command (MWD) 63, and the coal It is configured as coal / fuel oil supply flow rate command generation means for generating a supply flow rate command 78 and a light oil supply flow rate command (fuel oil supply flow rate command) 84. This coal / fuel oil supply flow rate command generation means is used for primary ventilation other than the stopped primary ventilator during the run-back operation (during boiler load drop control) when any one of the primary ventilators 6 and 7 fails. Coal supply flow rate to the boiler 3 on the condition that the coal supply flow rate command is larger than the load commensurate with the capacity of the machine (healthy primary ventilator), before any one primary ventilator stops Change to a coal supply flow rate that is less than the flow rate, for example, a coal supply flow rate that corresponds to a load suitable for the capacity of a healthy primary ventilator, and a light oil supply flow rate for continuing the light oil supply to the boiler 3 As, the element which resets the ratio of the coal supply flow volume and light oil supply flow volume with respect to the boiler 3 is provided. Further, the coal / fuel oil supply flow rate command generating means indicates the ratio of the coal supply flow rate and the light oil supply flow rate to the boiler 3 during the run-back operation (boiler load drop control). The flow rate detecting means) is configured to include elements that are set based on the detected value of the 75 and the detected value of the light oil flow rate detector (fuel oil supply flow rate detecting means) 87.

  In order to determine whether or not to perform control by the runback operation (control at the time of boiler load drop control), a runback determination circuit is provided as shown in FIG. When the coal supply flow rate is larger than the load corresponding to the capacity of a healthy primary ventilator (auxiliary), the generator output command for the coal / fuel oil supply flow rate command generation means is run back on condition that the supply of light oil is continued. As shown in FIG. 3, a runback load setting circuit is provided as a generator output command changing means for changing to a generator output command at the time of operation.

  As shown in FIG. 2, the runback determination circuit includes an OR circuit 24, a signal switch (H / L) 25, AND circuits 26, 30, 31, 39, 42, signal delay units 38 and 41, an OR circuit 40, 43 and 46, and flip-flop circuits 48 and 49.

  A signal relating to the APAF stop 21 indicating that the primary ventilator 6 has failed and a signal relating to the BPAF stop 22 indicating that the primary ventilator 7 has failed are input to the OR circuit 24, and a coal flow command 23 is input to the signal switch 25. Is entered. A signal related to the turbine master automatic 28 and a signal related to the boiler master automatic 29 are input to the AND circuit 30, a signal related to the X% runback target reach 32 is input to the AND circuit 39, and an X% runback operation is performed to the signal delay unit 38. 33, a signal related to the 50% runback target reaching 34 is input to the AND circuit 42, a signal related to the 50% runback operation 35 is input to the signal delay unit 41, and the MFT is input to the OR circuit 44. A signal related to the operation 36 and a signal related to the disconnection 37 are input, and a signal related to the other runback operation 45 is input to one end of the OR circuit 46.

  In the runback determination circuit, when one of the primary ventilators 6 and 7 fails and stops, a signal from the OR circuit 24 is output to the AND circuit 26, and the signal switch 25 receives the coal flow command 23 as a coal flow command 23. When a command of 50% load or more is input, a signal from the signal switch 25 is output to the AND circuit 26. Further, when the turbine master automatic 28 and the boiler master automatic 29 are established, a signal from the AND circuit 30 to the AND 26 is output. That is, when one of the primary ventilators 6 and 7 fails, the coal flow command 23 at this time exceeds 50% load, and the conditions of the turbine master automatic 28 and the boiler master automatic 29 are satisfied, and the AND circuit 26, the flip-flop 48 is set, a signal related to the runback operation 47 is output from the OR circuit 46 to the runback load setting circuit 64, and a signal related to the X% runback operation 33 is output from the flip-flop 48. Is output to the runback load setting circuit 64.

  As shown in FIG. 3, the runback load setting circuit 64 includes a signal generator 101, an adder 102, a signal switch 103, a signal generator 104, signal switchers 105 and 106, a change rate limiter 107, and a subtractor 109. , 111, signal switchers 110 and 112, the change rate limiter 107 outputs a generator output command (MWD) 108 to the low value selector 65, and the signal switcher 110 receives 50%. A signal related to the runback target reach 34 is output, and a signal related to the X% runback target reach 32 is output from the signal switch 112. The signal switcher 103 receives a signal related to the X% runback operation 33, the signal switcher 105 receives a signal related to the 50% runback operation 35, and the signal switcher 106 and the change rate limiter 107 run. A signal related to the back operation 47 is input.

  In the runback load setting circuit 64 having the above configuration, during normal operation of the boiler, the signal (signal corresponding to 100% load) based on the generator output command (MWD) 63 is directly used as the signal switching units 103, 105, and 106, and the change rate limiter. A generator output command (MWD) 108 is output to the low value selector 65 via 107.

  On the other hand, during the runback operation in which one of the primary ventilators 6 and 7 has failed, a signal related to the X% runback operation 33 is input to the signal switch 103 and a signal related to the runback operation 47 is input to the signal switch 106. Since the signal is input to the change rate limiter 107, the signal switching units 103 and 106 perform signal switching. That is, at the time of the runback operation, for example, a command corresponding to a 20% load is input to the adder 102 as the light oil load command 86, and the signal generator 101 matches the sound primary ventilator (auxiliary) capacity. A command corresponding to a load, for example, a command corresponding to a 50% load is input, and a command corresponding to a 70% load is output from the adder 102. This command is output from the signal switchers 103, 105, and 106, and the change rate limiter 107. Is output as a generator output command (MWD) 108 during the run-back operation. The generator output command 108 at this time is changed from a command corresponding to 100% load during normal operation to a command corresponding to 70% load.

  Next, operation during normal operation of the boiler will be described. First, as a generator output command (MWD) 63, for example, when a command equivalent to 100% load is output, the generator output command 63 passes through the runback load setting circuit 64 as it is to the low value selector 65. At the same time, the generator output command 63 is directly input to the low value selector 65, and the generator output command 63 corresponding to 100% load is directly output from the low value selector 65 to the boiler master controller 66 and the co-firing ratio setting device. Is output to 67. In the boiler master controller 66, the input signal related to the generator output command 63 is corrected by deviation of the main steam pressure, and the corrected signal is converted into a boiler input command (BID) and output to the fuel program generator 68. To do. The fuel program generator 68 outputs, for example, a command equivalent to 100% load as a fuel flow rate command (FRD).

  On the other hand, when the generator output command 63 is input to the mixed combustion rate setting device 67, the mixed combustion rate setting device 67 sets the mixed combustion ratio of coal (coal powder) and light oil based on the generator output command 63, that is, The ratio between the coal supply flow rate and the light oil supply flow rate is set. For example, the coal powder supply flow rate is set to be equivalent to 80% load, the light oil supply flow rate is set to be equivalent to 20% load, and a signal relating to the value (2/10) indicating the ratio of light oil among the set values is sent to the signal switcher 69. Output to. Since the signal switcher 69 selects the signal from the mixed firing rate setting unit 67 during normal operation, the signal from the mixed firing rate setter 67 is output to the multiplier 74 via the signal switcher 69. It should be noted that the setting of the mixed firing rate in the mixed firing rate setting unit 67 can be automatically set in consideration of the operation state or manually by CRT operation.

  When a signal related to the co-firing ratio is input to the multiplier 74, a fuel flow rate command corresponding to 100% load and a value indicating the co-firing ratio, for example, 2/10, are multiplied. A command equivalent to% load is output. The fuel flow rate command corresponding to the 20% load is output as a light oil flow rate command 80 to the function generator 85 and the subtracter 82 via the retainer 79. When a fuel flow command equivalent to 20% load is input to the function generator 85, a light oil load command 86 equivalent to 20% load is output from the function generator 85. In addition to the light oil flow command 80, a light oil supply flow 81 detected by the light oil flow detector 87 is input to the subtractor 82. The subtractor 82 subtracts the light oil supply flow 81 from the light oil flow command 80. Is output to the proportional integrator 83. The proportional integrator 83 generates a light oil supply flow command 84 for suppressing a deviation that is a difference between the light oil flow command 80 and the actual light oil supply flow 81 to 0, and adjusts the generated light oil supply flow command 84 to the light oil flow control. Output to the valve 89. Thereby, the opening degree of the light oil flow rate adjusting valve 89 is adjusted according to the light oil supply flow rate command 84, and the light oil supply flow rate to the boiler 3 is controlled.

  On the other hand, when a fuel flow command (FRD) indicating 100% load is input to the subtractor 73 and a signal indicating a fuel flow command equivalent to 20% load is input from the multiplier 74 to the subtractor 73, the subtractor. The difference between the two is obtained at 73, and the coal flow rate command 23 corresponding to 80% load is output from the subtractor 73 to the subtractor 76. In addition to the coal flow command 23, the subtracter 76 is input with a signal indicating an actual coal supply flow rate 75 from a detector that detects the actual supply flow rate of the coal powder. A signal indicating the difference between the command 23 and the coal supply flow rate 75 is output to the proportional integrator 77. The proportional integrator 77 generates a coal supply flow command 78 for suppressing a deviation, which is a difference between the coal flow command 23 and the coal supply flow 75, and outputs the generated coal supply flow command 78 to the mill 2. . As a result, an amount of coal powder according to the coal supply flow rate command 78 is sent from the mill 2 to the boiler 3.

  That is, as shown in FIG. 5A, combustion in the boiler 3 can be performed smoothly by supplementing the flow rate of 80% load with coal powder and supplementing the 20% load with light oil flow rate.

  Next, at the time of a runback operation (at the time of boiler load drop control) in which one of the primary ventilators 6 and 7 fails, a signal related to the runback operation 47 and X% from the runback determination circuit shown in FIG. Signals relating to the runback operation 33 are output, and these signals are input to the runback load setting circuit 64 and also input to the NOT circuit 61 and the holder 79.

  When a signal related to the X% runback operation 33 is input to the retainer 79, the retainer 79 retains the value before the runback operation occurs, and the proportional integrator 83 continues to supply light oil. As a command to perform, a light oil supply flow command 84 corresponding to a 20% load remains output. Further, the light generator load command 86 corresponding to the 20% load is still output from the function generator 85.

  On the other hand, in the runback load setting circuit 64, signals are switched in the signal switchers 103 and 106 in response to the signal related to the runback operation 47 or the signal related to the X% runback operation 33, and the adder 102 generates a signal. A command equivalent to 50% load and a light oil load command 86 equivalent to 20% load output from the vessel 101 are added. Then, the command added by the adder 102 is input to the change rate limiter 107 via the signal switchers 103, 105, and 106, and a command corresponding to a 70% load is output from the change rate limiter 107 to the generator output. It is output as a command 108. Thereby, in the low value selector 65, the generator output command 108 indicating 70% load is selected instead of the generator output command 63 corresponding to 100% load, and the selected generator output command is controlled by the boiler master control. To the unit 66 and the mixed firing rate setting unit 67. When the generator output command 108 corresponding to the 70% load is corrected by the boiler master controller 66 and then input to the fuel program generator 68, the fuel flow rate command (FRD) corresponding to the 70% load is output from the fuel program generator 68. Is output to the multiplier 74 and the subtractor 73. In this case, since the signal related to the X% runback operation 33 is input to the NOT circuit 61, the output of the AND circuit 62 is lost, and the signal switch 69 selects the signal from the divider 71.

  A signal relating to the light oil supply flow rate 70 detected by the light oil flow rate detector 87 is input to the divider 71, and the sum of the light oil supply flow rate 70 detected by the light oil flow rate detector 87 and the actual coal supply flow rate 75 is calculated. The signal shown is input from the adder 90. At the start of the runback operation, a signal corresponding to 100% load is input from the adder 90 to the divider 71, and a signal corresponding to 20% load is input from the light oil flow rate detector 87 as the light oil supply flow rate 70. The divider 71 outputs a signal relating to 2/10 as the value of the ratio of light oil in the mixed combustion rate. When this signal is input to the multiplier 74 via the signal switch 69, a signal of 70 × 2/10 = 14% is output from the multiplier 74.

Here, since the divider 71 obtains the mixed combustion rate of light oil and coal based on the actual light oil supply flow rate 70 and the actual coal supply flow rate 75, the divider 71 obtains a mixed combustion rate of 2 / A signal for gradually decreasing the coal co-firing rate from 10 to 2/7 of the target value is output.

  That is, when the multiplier 74 multiplies the fuel flow rate command corresponding to 70% load and the mixed combustion rate 2/10 at the start of the runback operation, the multiplier 74 outputs a fuel flow rate command equivalent to 14% load. Is done. When this signal is subtracted by the subtracter 73 from the signal corresponding to the 70% load, the signal corresponding to the 14% load is subtracted from the subtractor 73, the coal flow rate command 23 corresponding to the 56% load is output. 78 is reduced to a command equivalent to 56% load. As a result, when the coal supply flow rate decreases, the actual coal supply flow rate 75 input to the adder 90 also decreases. When such control is repeated, the divider 71 outputs a signal that finally decreases to 2/7 of the target value as the mixed combustion rate.

  Thus, in the present embodiment, during the run-back operation, control is performed to maintain the light oil supply flow rate command 84 equivalent to 20% load, and the coal supply flow rate command 78 is gradually changed from the command equivalent to 80% load. Since the fuel oil flow rate command 84 is maintained at a value equivalent to 20% load, the combustion energy in the boiler 3 can be suppressed from being reduced, and a large amount of power can be secured. It becomes possible to do.

  Next, the effect when the control method according to the present invention is used and when the conventional control method is used will be described with reference to FIG. FIG. 5 is a load change diagram with time (T) on the horizontal axis and load (%) on the vertical axis, and one primary ventilator out of two primary ventilators is before a failure (trip). Two cases are shown with respect to the mixed firing rate.

  In the case of (a), when the diesel oil before the primary ventilator trip is equivalent to 20% load and the coal is larger than the load commensurate with the capacity per two primary ventilators, here it is the case equivalent to 80% load is there. In this case, in the conventional circuit, after the primary ventilator trip, the load run back operation becomes 50%, the light oil load 122 becomes 0%, the coal load 121 becomes 50%, and the combustion rate in the boiler decreases rapidly. It will not be possible to secure sufficient power generation.

  On the other hand, in the present invention, the runback operation is performed on the condition that the coal flow rate command 23 is 50% or more, but the light oil load 124 is maintained to be equivalent to the 20% load, and the coal load 123 is the primary load. It is 50% of the load of one ventilator. Therefore, by burning light oil in addition to burning coal, the amount of power generation can be secured by 20% more than the conventional one.

  In the case of (b), the light oil before the primary ventilator trip is 50% load and the coal is 50% load. Also in this case, in the conventional circuit, after the trip, the load run back operation becomes 50%, the light oil load 126 becomes 0%, the coal load 125 becomes 50%, and the power generation amount decreases as the combustion energy in the boiler decreases. Will do.

  On the other hand, in the present invention, since the coal flow rate command 23 is not 50% or more, the runback operation does not occur, and the light oil load 128 and the coal load 127 remain unchanged at 50%. Therefore, by burning light oil together with coal, it is possible to suppress a decrease in combustion energy and to secure a power generation amount that is 50% higher than that of the conventional one. Further, in this case, load runback does not occur, which can contribute to stabilizing the operation of the power plant.

  In the embodiment, when a signal related to the X% runback target reaching 32 is output from the signal switch 112, the logical product condition of the AND circuit 39 is satisfied, the signal from the OR circuit 40 is output, and the flip-flop The loop circuit 48 is reset, and the runback operation ends.

According to the present embodiment, in the boiler 3, when one of the primary ventilators 6 and 7 stops, the amount of power generated by light oil combustion is used, so that up to 50% of the rated load by the conventional runback is used. It does not lead to a descent, can suppress a decrease in combustion energy, and can secure a large amount of power generation. Further, since it is not necessary to extinguish the light oil burner, there is no influence on the boiler combustion state due to the burner extinguishing , and there is no sudden load reduction operation due to runback, so that a highly stable operation can be performed.

  In the present embodiment, the light oil is described as an example of co-firing with coal, but the present invention can be applied to other fuels such as heavy oil in addition to the light oil.

It is a block block diagram of the boiler automatic control apparatus which shows one Embodiment of this invention. It is a block block diagram of a runback determination circuit. It is a block block diagram of a runback load setting circuit. It is a block block diagram for demonstrating the relationship between a boiler and an auxiliary machine. It is a load change figure for contrasting the effect of the present invention and the conventional one, and (a) is a load change figure when light oil before the primary ventilator trip is equivalent to 20% load and coal is equivalent to 80% load. b) is a load change diagram when the diesel oil is 50% load and the coal is 50% load before the primary ventilator trip.

Explanation of symbols

2 Mil 3 Boiler 4, 5 Air heater 6, 7 Primary ventilator 8, 9 Pusher ventilator 10, 11 Induction ventilator 64 Runback load setting circuit 65 Low value selector 66 Boiler master controller 67 Mixed combustion rate setter 68 Fuel Program generator 69 Signal switch 71 Divider 73 Subtractor 74 Multiplier 76 Subtractor 77 Proportional integrator 79 Retainer 82 Subtractor 83 Proportional integrator 85 Function generator 87 Light oil flow detector 89 Light oil flow control valve

Claims (2)

The coal powder is conveyed from the mill by air supplied from a plurality of auxiliary machines and supplied to the coal burner, the fuel oil supplied from the fuel oil supply means is supplied to the fuel oil burner and burned in the co-fired coal fired boiler, In generating power by driving the generator with steam generated in the co-fired coal fired boiler, the coal supply flow rate supplied to the coal burner and the fuel oil burner based on the total fuel supply flow rate corresponding to the generator output command In a boiler automatic control method for a co-fired coal fired boiler that distributes and controls the fuel oil supply flow rate to be supplied according to a preset co-firing rate,
When at least one of said auxiliary fails to hold the fuel oil supply flow rate at immediately before the failure of the auxiliary device, setting the fuel oil supply flow rate to the holding as a command value, on the basis of the finger command value While controlling the fuel oil supply flow rate,
When the coal supply flow rate immediately before the failure of the auxiliary machine is less than the coal supply flow rate that can be supplied by the remaining auxiliary machine, run back control is not performed, Runback control shall be performed,
When performing run-back control, the sum of the said coal feed flow rate that can be supplied to the generator output command of the run-back control by the remaining auxiliary and the held the fuel oil supply flow rate, the run-back control While generating a total fuel flow rate command corresponding to the generator output command, and dividing the detected value of the fuel oil supply flow rate by the addition value of the detected value of the coal supply flow rate and the detected value of the fuel oil supply flow rate, A ratio of the fuel oil supply flow rate with respect to the total fuel flow rate command is determined, and a command value for the coal supply flow rate is set by subtracting the fuel oil supply flow rate corresponding to the determined ratio from the total fuel flow rate command. A boiler automatic control method, wherein the coal supply flow rate is controlled based on a value. Coal supply means for conveying coal powder from a mill by air supplied from a plurality of auxiliary machines and supplying the coal burner, fuel oil supply means for supplying fuel oil to the fuel oil burner, and coal supplied to the coal burner A control means for distributing and controlling the supply flow rate and the fuel oil supply flow rate supplied to the fuel oil burner according to a preset mixed combustion rate based on a total fuel supply flow rate corresponding to a generator output command; And a run-back control means for controlling the coal supply flow rate and the fuel oil supply flow rate when at least one of the above malfunctions, and the coal burner, the coal powder supplied to the fuel oil burner, and the fuel oil are co-fired coal In a boiler automatic control device that generates electricity by driving a generator with steam generated by burning with a firewood boiler,
The runback control means holds the fuel oil supply flow rate immediately before the failure of the auxiliary machine when at least one of the auxiliary machines fails , sets the held fuel oil supply flow rate as a command value, While controlling the fuel oil supply flow rate based on the command value,
When the coal supply flow rate immediately before the failure of the auxiliary machine is less than the coal supply flow rate that can be supplied by the remaining auxiliary machine, run back control is not performed, Runback control shall be performed,
When performing run-back control, the sum of the said coal feed flow rate that can be supplied to the generator output command of the run-back control by the remaining auxiliary and the held the fuel oil supply flow rate, the run-back control While generating a total fuel flow rate command corresponding to the generator output command, and dividing the detected value of the fuel oil supply flow rate by the addition value of the detected value of the coal supply flow rate and the detected value of the fuel oil supply flow rate, A ratio of the fuel oil supply flow rate with respect to the total fuel flow rate command is determined, and a command value for the coal supply flow rate is set by subtracting the fuel oil supply flow rate corresponding to the determined ratio from the total fuel flow rate command. An automatic boiler control apparatus that controls the coal supply flow rate based on a value.

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