JP3986485B2 - Boiler control device and boiler control method - Google Patents

Description

  The present invention relates to a boiler control device and a boiler control method, and more particularly to a boiler control device and a boiler control method that can maintain an oxygen concentration at the outlet of a economizer at a set value.

For example, Patent Document 1 includes two ventilators each having a commercial AC power source and an inverter power source. When the inverter power source becomes inoperable, the power source is switched from the inverter power source to the commercial power source. A boiler control device that can continue operation is shown. Further, it is shown that an open bias command is supplied to a damper for limiting the ventilation amount in order to compensate for a decrease in the ventilation amount accompanying a decrease in the driving speed of the ventilator that occurs at the time of switching and to maintain the stability of combustion. Has been.
JP 2002-267105 A

  In the above-described conventional technology, for example, when an inverter power source that constitutes one system out of power sources that respectively drive two systems of ventilators, the failed inverter power source is switched to a commercial power source. If the inverter power supply is switched to the commercial power source and the switching to the commercial power source fails for some reason, the boiler load must be safely and promptly reduced to an amount that can be operated by the remaining system. That is, a runback operation must be performed.

  During this runback operation, there is a high possibility that the amount of air supplied to the boiler will be insufficient or the amount of fuel supplied will be excessive, and the possibility that the oxygen saver outlet oxygen concentration will decrease.

  This invention is made | formed in view of these problems, and provides the boiler control apparatus which can hold | maintain an economizer exit oxygen concentration to a setting value.

  In order to solve the above problems, the present invention employs the following means.

A ventilator provided with a plurality of forced air ventilators for supplying combustion air to the boiler, a vane for adjusting the flow rate of the combustion air, and a plurality of air flow rate detectors for detecting the flow rate of the combustion air;
An inverter for supplying an AC power supply voltage by converting the AC power supply voltage to an AC voltage having a predetermined frequency, and a circuit breaker for supplying the output of the inverter or the AC power supply voltage to the motor;
Based on the air flow command supplied from the outside and the detection output of the air flow detector, equipped with an automatic boiler control device that adjusts the opening degree of the vane and the rotational speed of the motor,
The boiler automatic control device, when the motor driving source by to switch the breaker fails to operate to switch to the AC power supply voltage side from the inverter side, a predetermined time adds compensation instruction the the opening command of each vane Do

  Since this invention is provided with the above structure, it can provide the boiler control apparatus which can hold | maintain an economizer exit oxygen concentration to a setting value.

  Hereinafter, the best embodiment will be described with reference to the accompanying drawings. FIG. 1 is a diagram illustrating a boiler control device. In the figure, 51 is a boiler, 52a and 52b are pushing ventilators that blow combustion air to the boiler 51, 53a and 53b are driving motors that drive the pushing ventilators 52a and 52b, and 54a and 54b are pushing ventilators. This is a vane for the push-in ventilators 52a and 52b for adjusting the flow rate of air to be pushed in (ventilation amount), and is provided near the outlet of the push-in ventilator. Reference numerals 55a and 55b denote air flow rate detectors for detecting the air flow rate pushed by the push-in ventilators 52a and 52b.

  56a and 56b attract the combustion gas from the boiler 51 and exhaust air from the chimney 68, 57a and 57b drive motors for driving the induction fans 56a and 56b, and 58a and 58b attract the air ventilator. This is a damper for adjusting the air flow rate (ventilation amount) to be provided, and is provided in the vicinity of the inlet of the induction fan.

  59 is a boiler automatic control device that comprehensively controls the process amount of the boiler 51, and 60 is an inverter control device that performs output control of the inverters 64a and 64b. 61 is a main power source composed of an AC power source of commercial frequency, 64a and 64b are inverters for driving motors 53a and 53b, 62a, 62b, 63a, 63b, 65a, 65b, and 66a, 66b are circuit breakers, respectively. The drive motor 53a drive system ((A) system) and the drive motor 53b drive system ((B) system) are respectively configured.

  Here, when the drive motor 53a is driven by the inverter 64a, the circuit breakers 62a, 63a, and 65a are turned on to interrupt the circuit breaker 66a. Further, when the driving motor 53a is driven by the main power supply 61, the circuit breakers 63a and 65a are disconnected and the circuit breakers 62a and 66a are turned on. Similarly, when the drive motor 53b is driven by the inverter 64b, the circuit breakers 62b, 63b and 65b are turned on to shut off the circuit breaker 66b. Further, when the driving motor 53b is driven by the main power supply 61, the circuit breakers 63b and 65b are disconnected and the circuit breakers 62b and 66b are turned on.

  In addition, for example, the drive motor 53a drive system (system (A)) can be applied to a system that drives a motor that drives an induction fan in addition to a system that drives a push-in fan.

  During the operation of the boiler, the motors 53 a and 53 b for driving the push-in ventilator are driven, and the combustion air is blown to the boiler 51. The air sent from the push-in ventilators 52a and 52b is combusted in the boiler 51, becomes combustion gas, is sucked in through the induction ventilators 56a and 56b, and is discharged into the atmosphere through the chimney 68.

  The pressure in the boiler 51 (boiler pressure) must be controlled within a specified value for reasons of boiler safety or performance. The boiler pressure is controlled by adjusting the opening degree of the dampers 58a and 58b attached in the vicinity of the induction fans 56a and 56b. In addition, the flow rate of air flowing through the forced air blower must be controlled within a set value for balance with the flow rate of fuel supplied to the boiler, for boiler safety, or for performance reasons. The flow rate of air flowing through the pusher ventilator adjusts the opening degree of the vanes 54a, 54b attached in the vicinity of the pusher ventilators 52a, 52b or the rotational speed of the drive motors 53a, 53b that drives the pusher ventilators 52a, 52b. To do.

  FIG. 2 is a view for explaining the mounting position of the oxygen concentration detector. As shown in the figure, an oxygen concentration detector 101 is disposed near the outlet of the economizer 511 of the boiler 51. Thereby, the oxygen concentration detection signal 102 can be obtained from the oxygen concentration detector 101 in real time. By referring to the oxygen concentration detection signal 102, it is possible to determine whether the balance between the fuel flow rate supplied to the boiler and the air flow rate is good or bad.

  In FIG. 1, the boiler automatic control device 59 includes an arithmetic circuit, and opening commands 71a and 71b for the vanes 54a and 54b based on the air flow command 24 and the air flow signals 67a and 67b from the air flow detectors 55a and 55b. Is calculated and output, and the vane opening degree is controlled based on the output value. Further, based on the air flow rate command 24 and the air flow rate signals 67a and 67b from the air flow rate detectors 55a and 55b, the rotational speed commands 69a and 69b of the driving fan drive motor are calculated, and the calculation result is inverter controlled. Output to the device 60. In addition to the above, the boiler automatic control device 59 controls, for example, a generator output, steam temperature, pressure, and the like.

  The inverter control device 60 outputs inverter output commands 70a and 70b based on the rotational speed commands 69a and 69b of the push-in ventilator driving motors 53a and 53b from the boiler automatic control device 59, and controls the inverters 64a and 64b. As a result, the rotational speeds of the push-in ventilator drive motors 53a and 53b are controlled to coincide with the rotational speed command signals 69a and 69b from the boiler automatic control device 59.

  FIG. 3 is a diagram illustrating details of the boiler automatic control device. First, during normal operation (the push ventilators 52a and 52b are both operated by an inverter and the vanes 54a and 54b are provided in the vicinity of the push ventilators 52a and 52b, and the pusher ventilator driving motor 53a, (When the rotational speed of 53b is automatically controlled).

  In this case, the air flow rate 1 and the air flow rate command 24, which are the average values of the air flow rate signals 67a and 67b output from the air flow rate detectors 55a and 55b, are processed by the subtractor 2 to calculate the air flow rate deviation signal 201. . Next, a proportional-integral calculation is performed on the air flow rate deviation signal 201 by the proportional integrator 3 to generate an air flow rate control signal 202. The air flow rate control signal is used to control the A system and the B system, but the subsequent processing is the same for both the A system and the B system, and therefore, only the control circuit for the A system will be described in FIG.

  The air flow rate control signal 202 and the vane opening compensation signal 203 for compensating the opening of the vane 54a are added by an adder to become a final vane opening command 71a, and the opening of the vane 54a is adjusted by this signal.

  On the other hand, the rotational speed command signal 204 of the push-in ventilator 52a generated by the function generator 25 based on the air flow rate command 24 is pushed through the signal ventilator 27, the signal switcher 28, and the change rate limiter 29. The rotation number command signal 69a of the machine 52a is output to the inverter control device 60. Next, after the control operation is performed by the inverter control device 60, the output of the inverter 64a is controlled as the inverter output command 70a. Thus, the rotational speed of the driving motor 53a of the push-in ventilator 52a is controlled so as to coincide with the rotational speed command 69a from the boiler automatic control device 59.

  The signal switch 27 is a function generator used when the drive motors 53a and 53b for driving the push-in ventilators 52a and 52b are both operated, that is, when both the A system and the B system are operating. 25, in the case of one-system operation, for example, the output of the generator 26 used when only the A-system is operated is switched and used. The signal switching unit 28 selects the signal 206 when the driving motor is operated by the inverter, and switches to the signal 207 side when the driving motor is operated by the main power supply 61. Thereby, when operating with the main power supply, the rotation speed is set to 100%.

  Next, the vane opening compensation signal 203 of the push-in ventilator 52a will be described. The vane opening compensation signal 203 of the push-in ventilator 52a is an opening program signal based on the boiler static characteristics. The signal switch 15 is driven by the output signal of the adder 14 when the drive motor 53a of the push-in ventilator 52a is driven using the inverter 64a using a commercial power supply, and by the main power supply 61 which is a commercial power supply. When the motor 53a is being driven, the output signal of the signal switcher 10 is switched and output.

  The adder 14 receives the output signal from the signal switch 13 and the output signal from the signal switch 23. The signal switching unit 13 outputs the output signal of the function generator 12 when the driving motors 53a and 53b of the push-in ventilators 52a and 52b are operated by the inverters 64a and 64b. When the driving motor 53a of the push-in ventilator 52a is operated, the output signal of the function generator 19 is switched and output.

  The function generator 20 is a function for compensating for a decrease in the amount of air pushed in due to a natural speed drop due to a non-voltage period when the driving power source of the driving fan for driving the pushing fan is switched from the inverter side to the main power source that is a commercial power source. Is generated. When the output signal 212 of the function generator 20 is selected by the signal switch 23, the vanes 54a and 54b can be opened in advance by the output (open bias signal) of the function generator. The bias signal is supplied to the vane 54b of the system that does not switch the drive source, in addition to the vane 54a of the system in which the rotational speed of the driving motor is naturally reduced by switching the drive source. Thereby, the fall of an air flow rate can be suppressed effectively.

  The signal switcher 10 is configured such that the output signal of the function generator 9 used when the driving motors 53a and 53b are directly operated by the main power supply 61 and the driving motor 53a are directly operated by the power supply 61 in the case of single system operation. The output signal of the function generator 11 used when driving is switched.

  The signal 217 selected by the signal switch 15 is added to the air flow rate control signal 202 via the signal switch 17, the change rate limiter 18 and the adder 4, and becomes the final vane opening command 71 a.

  When the push-in ventilator 52a is stopped, the signal switcher 17 selects a 0% vane opening compensation signal. The change rate limiter 18 limits a sudden change in signal.

  The control gain that is a parameter of the proportional-plus-integral calculator 3 is selected by the signal switcher 8. For example, the output signal of the signal generator 6 is selected when both the A system and the B system are operated by the commercial frequency power supply or when one is operated by the commercial frequency power supply and the other is stopped. When both the A system and the B system are operated by an inverter, or when one is operated by an inverter and the other is stopped, the output signal of the signal generator 7 is selected. When one is operated by the inverter and the other is operated by the main power supply 61, the output signal of the signal generator 7 is selected.

  FIG. 4 is a diagram for explaining the characteristics (successful switching from the inverter operation to the main power supply operation) at the time of switching the drive power supply of the driving fan driving motor. First, at time points t0 to t1, both the A system and the B system are in inverter operation, that is, the driving power for the driving motors 53a and 53b of the forced draft fans 52a and 52b is changed from the main power supply 61 to the circuit breakers 62a and 62b, It is supplied through circuit breakers 63a and 63b, inverters 64a and 64b, and circuit breakers 65a and 65b.

When the B-system inverter 64b fails at time t1, the circuit breakers 63b and 65b are disconnected, and the circuit breaker 66b is turned on at time t2. As a result, the power supply line is switched from the inverter side to the main power supply 61 of the commercial power supply. At this time, the relationship among the rotational speed of the driving motor 53b of the push-in ventilator 52b, the opening degree of the vane 54b, and the economizer outlet oxygen (O ₂ ) concentration detection signal 102 is shown in FIG. In addition, although there are an upper limit and a lower limit in the specified value of the oxygen concentration, only the oxygen concentration lower limit (O ₂ lower limit) which is particularly problematic is shown in the figure.

  As shown in the figure, from the time when the B-system inverter 64b breaks down until the switching operation to the commercial power supply, the rotational speed naturally decreases, so the air flow rate decreases. In order to suppress this decrease, an open bias is applied to the vanes of both systems in this embodiment. After switching to the main power supply 61 (after t2), the rotational speed is increased to 100%. At this time, by appropriately narrowing the vane opening degree, it is possible to reduce the change in the air flow rate flowing through the forced air blower. Thereby, the economizer outlet oxygen concentration 102 can be controlled within a specified value.

  FIG. 5 is a diagram for explaining the characteristics (switching failure from the inverter operation to the main power supply operation) at the time of switching the driving power of the pushing fan driving motor. First, at time t0 to t1, both the A system and the B system are operating as an inverter, that is, the driving power for the driving motors 53a and 53b of the forced draft fans 52a and 52b is cut from the main power supply 61 to the circuit breakers 62a and 62b. Are supplied via devices 63a and 63b, inverters 64a and 64b, and circuit breakers 65a and 65b.

  When the B-system inverter 64b fails at time t1, the circuit breakers 63b and 65b are disconnected, and the circuit breaker 66b is turned on at time t2. If switching of the driving power source fails at time t2, the runback operation is started.

  At this time, the drive motor 53b of the push-in ventilator 52b is gradually decelerated because no drive power is supplied. On the other hand, the flow rate of the fuel supplied to the boiler is constant until the runback operation start time (t2) because the flow rate command is determined according to the generator output command, and gradually decreases after the runback operation start time. It will be. For this reason, the oxygen concentration detection signal 102 at the outlet of the economizer is lowered below the lower limit value, and the stability of combustion is lowered.

  FIG. 6 is a diagram illustrating a process for adding a debiasing to the fuel supply command. For example, when a B-system inverter fails, a B-system inverter failure signal 151 is output, and this failure signal is input to the time limit operation timer 154. The operation time limit of the time limit operation timer 154 is set to the time from when the B-system inverter breaks down until the main power supply 61 is switched. As a result, after failing to switch to the main power supply, the output of the time limit operation timer 154 is input to the AND circuit 155. Further, since the push ventilator 52b trips, the push ventilator 52b trip signal 152 is output and input to the AND circuit 155. In the runback state, a runback operation signal 162 is output and input to the AND circuit 155. As a result, the AND circuit 155 outputs a signal, and the output signal enters the flip-flop circuit 156, and the flip-flop circuit 156 is set.

  The analog switch 159 is turned on by the set state signal of the flip-flop circuit 156. At this time, the fuel flow command 157 is debiased by the function generator 158 and output from the analog switch 159. As a result, a compensated fuel flow rate command (FRD) 163 in which the fuel flow rate command (FRD) 157 is compensated, that is, a debiased value can be obtained.

  FIG. 7 is a diagram for explaining characteristics at the time of switching the drive power source of the driving fan driving motor (failure of switching from inverter operation to main power source operation, with fuel flow command compensation). First, at time points t0 to t1, both the A system and the B system are in inverter operation, that is, the driving power for the driving motors 53a and 53b of the forced draft fans 52a and 52b is changed from the main power supply 61 to the circuit breakers 62a and 62b, It is supplied through circuit breakers 63a and 63b, inverters 64a and 64b, and circuit breakers 65a and 65b.

  When the B-system inverter 64b fails at time t1, the circuit breakers 63b and 65b are disconnected, and the circuit breaker 66b is turned on at time t2. If switching of the driving power source fails at time t2, the runback operation is started.

  At this time, the drive motor 53b of the push-in ventilator 52b is gradually decelerated because no drive power is supplied. On the other hand, the fuel flow rate command FRD supplied to the boiler is subjected to the above-described compensation to become a compensated fuel flow rate command (FRD '). As a result, the fuel command (FRD ') is rapidly reduced. For this reason, the decrease in the economizer outlet oxygen concentration 102 is suppressed, and the decrease in the oxygen concentration (O2) is compensated to become the oxygen concentration (O2 '). That is, it is possible to prevent the stability of combustion from being lowered due to the oxygen concentration being lowered to the lower limit value or less.

  When the runback operation is completed, the runback completion signal 153 in FIG. 6 is output to reset the flip-flop circuit 156. As a result, the analog switch 159 selects and outputs the fuel flow rate command 157.

  As described above, according to this embodiment, the power supply system (driving) that supplies either the inverter that converts the main power supply voltage to an alternating voltage of a predetermined frequency or the motor that drives the ventilator by pushing in either of the main power supply voltages. When a plurality of systems (A system and B system) are provided and both systems are operating an inverter, if one system inverter fails and further switching to the main power source fails, other than the failed system An open bias can be applied to a vane provided in the vicinity of the push-in ventilator of this system for a predetermined time. That is, the open bias is supplied to the vane 54b of the system where the drive source is not switched, in addition to the vane 54a of the system where the rotational speed of the driving motor is naturally lowered by switching the drive source. Thereby, the fall of an air flow rate can be suppressed effectively.

  Further, a decrementing bias can be applied to the fuel flow rate command for a predetermined time. Thereby, the economizer outlet oxygen concentration which is important for combustion stability can be controlled within a specified value.

It is a figure explaining a boiler control apparatus. It is a figure explaining the attachment position of an oxygen concentration detector. It is a figure explaining the detail of a boiler automatic control apparatus. It is a figure explaining the characteristic (successful switching from an inverter driving | operation to a main power supply driving | operation) at the time of drive power supply switching of the motor for driving a draft fan. It is a figure explaining the characteristic at the time of drive power supply switching of the motor for pushing-in ventilator drive (switching failure from inverter operation to main power supply operation). It is a figure explaining the process which adds a decrement bias to a fuel supply command. It is a figure explaining the characteristic at the time of the drive power supply switching of the motor for pushing-in ventilator drive (switching failure from inverter operation to main power supply operation, with fuel flow command compensation).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air flow rate 2 Subtractor 3 Proportional integrator 4 Adder 6 Signal transmitter 8 Signal switcher 9 Function generator 18 Change rate limiter 24 Air flow rate command 52a, 52b Pushing ventilator 53a, 53b Drive motor 54a, 54b Vane 55a, 55b Air flow detector 56a, 56b Induction fan 57a, 57b Drive motor 58a, 58b Damper 59 Boiler automatic controller 60 Inverter controller 61 Main power supply 62a, 62b Breaker 64a, 64b Inverter 67a, 67b Air flow signal 68 Chimney 69a, 69b Speed command signal 70a, 70b Inverter output command 71a, 71b Vane opening command 101 Oxygen concentration detector 102 Oxygen concentration detection signal 154 Time limit operation timer 156 Flip-flop circuit 157 Fuel flow rate command 159 Analog switch

Claims (4)

A ventilator provided with a plurality of forced air ventilators for supplying combustion air to the boiler, a vane for adjusting the flow rate of the combustion air, and a plurality of air flow rate detectors for detecting the flow rate of the combustion air;
An inverter for supplying an AC power supply voltage by converting the AC power supply voltage to an AC voltage having a predetermined frequency, and a circuit breaker for supplying the output of the inverter or the AC power supply voltage to the motor;
Based on the air flow command supplied from the outside and the detection output of the air flow detector, equipped with an automatic boiler control device that adjusts the opening degree of the vane and the rotational speed of the motor,
When the operation of switching the motor drive source from the inverter side to the AC power supply voltage side fails by switching the circuit breaker, the boiler automatic control device adds a compensation command to each vane opening command for a predetermined time. A boiler control device characterized by that. In the boiler control device according to claim 1,
The boiler automatic control device includes fuel control means for controlling fuel supplied to the boiler, and when the operation for switching the circuit breaker to switch the motor drive source from the inverter side to the AC power supply voltage side fails, the fuel control means A boiler control device, wherein a decompensation command is added to the fuel supply command for a predetermined time. A ventilator provided with a plurality of forced air ventilators for supplying combustion air to the boiler, a vane for adjusting the flow rate of the combustion air, and a plurality of air flow rate detectors for detecting the flow rate of the combustion air;
An inverter that converts an alternating current power supply voltage into an alternating current voltage having a predetermined frequency and supplies the motor that drives the push-in ventilator;
A boiler control method comprising a boiler automatic control device, wherein the boiler automatic control device adjusts the opening degree of the vane and the rotational speed of the motor in accordance with an air flow command supplied from the outside and a detection output of the air flow detector. Because
When the operation of switching the motor drive source from the inverter side to the AC power supply voltage side fails by switching the circuit breaker, the boiler automatic control device adds a compensation command to each vane opening command for a predetermined time. The boiler control method characterized by the above-mentioned. In the boiler control method according to claim 3,
The boiler automatic control device includes fuel control means for controlling fuel supplied to the boiler, and when the operation for switching the circuit breaker to switch the motor input from the inverter side to the AC power supply voltage side fails, A boiler control method comprising adding a decompensation command to a fuel supply command for a predetermined time.

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