JP2000297930A - Device and method for controlling primary draft fan for pulverized coal combustion boiler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continue safe operation without damaging a primary draft fan by preventing the rapid draft increase of a primary draft fan outlet pressure during trip or stop action of a coal pulverizer under operation. SOLUTION: A primary draft fan control device for a pulverized coal combustion boiler is formed such that a pulverized coal combustion boiler has a plurality of coal pulverizers and a primary draft fan control device has a primary blower 42 for the coal pulverizer provided in common to a plurality of the coal pulverizers. The opening of a moving blade 41 of the primary draft fan is regulated based on a detecting signal for the outlet pressure of the primary draft fan 42 and a coal flow rate signal and a primary draft fan outlet pressure is controlled to a specified pressure. During a trip or a stop of the coal pulverizer, a primary draft fan moving blade is throttled at a high speed based on a variation value of a coal flow rate signal occasioned by the trip or the stop and a rate of change limiter 11 is provided to release the moving blade 41 from throttling at a timing matched with restoration of the primary draft fan outlet pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coal-fired boiler and a system in which a primary ventilator for a plurality of pulverized coal machines is a common facility. The present invention relates to a control device and a control method.

[0002]

2. Description of the Related Art FIG. 3 shows a primary blower moving blade command circuit of a conventional coal-fired boiler. The primary ventilator blade 41 adjusts the opening degree of the primary ventilator blade 41 using the coal flow signal 4 as a leading signal, and adjusts the opening degree of the primary ventilator blade 41 so that the primary draft outlet draft (pressure) becomes a specified value. Control is performed. In such a configuration, when the pulverized coal machine trips due to an accident or the like of the pulverized coal machine or a stop signal to the pulverized coal machine is issued, the pulverized coal machine air flow rate is, for example,
When the damper 39 shown in FIG. 2 is closed, the draft rapidly decreases but the outlet draft of the primary ventilator rapidly fluctuates greatly.

[0003] The primary ventilator rotor blade 41 detects the draft of the primary ventilator outlet and is operated so as to have a specified value. However, the inertia of the primary ventilator 42 causes a control delay, and due to this effect, the primary ventilator 42 operates normally. When it goes out of the operating area and enters the danger area of the fan (fan surging area), there is a problem with the strength of the primary ventilator. If the pressure of the primary ventilator becomes too high, the fan may be damaged. Become.

FIG. 5 shows the operating characteristics of the primary ventilator. The primary air flow rate increases and decreases at a substantially constant rate according to the number of operating pulverized coal machines (two to five in this example). In terms of static characteristics, as indicated by the two-dot chain line, the discharge pressure is about 1000 mmH ₂ O for any number of operating units, and the operating point of the primary ventilator (points A, C, E, and G in FIG. 5) is primary. Although it does not fall within the danger area (surging area) of the ventilator, the behavior of the operating point of the primary ventilator when the pulverized coal machine trips or stops is dynamic. Enter the danger zone. For example, when five pulverized coal machines are operating and one trips, the dynamic characteristic of the discharge pressure of the primary ventilator becomes A → B → C due to the inertia of the primary ventilator. In the dynamic characteristics, there is a characteristic region that enters the illustrated fan surging region. This may damage the primary ventilator. The fan characteristics shown in FIG. 5 show an example of a large-capacity boiler.

FIG. 2 shows a system diagram of combustion air of a coal-fired boiler. In a system in which a primary ventilator is a common facility in a coal-fired boiler, that is, a system in which a single primary ventilator supplies air to a plurality of pulverized coal generators 36, a primary ventilator outlet draft is provided by a primary ventilator blade 41. Since (pressure) needs to be a specified pressure, the primary ventilator 42 is installed and controlled by the primary ventilator blade 41.

In FIG. 2, coal in a coal bunker 34 is supplied to a coal feeder 3.
5, supply to the pulverized coal machine 36 according to the boiler load,
The coal is pulverized by the pulverized coal machine 36 and is burned from the coal feed pipe 100 to the burner 101
To be burned in a boiler furnace. On the other hand, in order to dry the fine powder pulverized by the pulverized coal machine 36, the hot air and the cool air which does not pass through the pulverized coal machine are respectively supplied from the primary ventilator 42 via the air preheater 26 to the hot air damper. The distribution is adjusted by the 37 and the cold air damper 38, and the air temperature to the pulverized coal machine is adjusted to a specified value.

Further, the amount of air to the pulverized coal machine is
6 is controlled by the pulverized coal machine inlet damper 39 so as to have a specified ratio with respect to the amount of coal from the coal feeder 35 to the coal feeder 6.

[0008]

In the prior art as shown in FIG. 3, in the prior art, a draft (pressure) detection value 1 of a primary ventilator outlet and a coal flow signal 4 (for example, from a coal feeder 35 to a pulverized coal Is the detected value of the coal flow supplied to
If the coal feeder and the pulverizer are one set in a one-to-one correspondence, there are a plurality of sets, so that the total amount of the detected values is obtained. In addition, a signal value for commanding the total fuel amount to the boiler can be used.)
The difference between the draft setting value obtained by the function generator 5 based on the above and the draft setting value is obtained by the subtractor 2, and the deviation signal is obtained by the controller 3.
The proportional integral control is performed by the
, And the draft setting value obtained by the function generator 7 on the basis of is added by the adder 6, and the primary ventilation blade 41 is controlled by the output signal.

In this case, the detected value of the primary draft outlet draft is fed back to the coal flow signal changed by a trip or the like, and the primary draft rotor blade 4 is used.
1 indicates that the primary ventilator blade 41 operates after the primary draft outlet draft (pressure) changes, so that the primary ventilator blade 41
It takes about 30 seconds to operate to the predetermined opening.

In the conventional control as described above, a trip due to, for example, an accident of the pulverized coal machine 36 or an intentional stop command issued by the command operator is issued during the load operation, and a large rise in the primary draft outlet draft is caused. When this occurs, the primary ventilator may enter the fan surging area and damage the primary ventilator.

An object of the present invention is to focus on the above-mentioned problems of the prior art, and to prevent the primary ventilator 42 from entering the fan surging area when a trip or stop signal of the pulverized coal generator 36 is transmitted. Another object of the present invention is to provide a primary ventilator control circuit for a coal-fired boiler. The rapid reduction operation of the air flow rate to the pulverized coal machine 36 includes the fully closed operation of the pulverized coal machine outlet damper 40 in addition to the fully closed operation of the pulverized coal machine inlet damper 39 when the pulverized coal machine 36 stops tripping or the like. It is.

[0012]

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

A pulverized coal combustion boiler having a plurality of pulverized coal machines, wherein a primary ventilator for the pulverized coal machines is a primary ventilator control device provided commonly to the plurality of pulverized coal machines, Adjusting the opening degree of the rotor blades of the primary ventilator based on the detection signal of the outlet pressure of the unit and the coal flow signal, controlling the outlet pressure of the primary ventilator to a specified pressure, and tripping the pulverized coal machine. Or at the time of stop, the primary ventilator rotor blades are throttled at high speed based on the change value of the coal flow signal accompanying the trip or stop, and the rotor blades are throttled at the same timing as the recovery of the primary ventilator outlet pressure. Primary blower control unit for the pulverized coal combustion boiler to be pulled out.

[0014] In a control method, a primary ventilator for a pulverized coal machine in a pulverized coal combustion boiler having a plurality of pulverized coal machines controls an outlet pressure of a primary ventilator commonly provided to the plurality of pulverized coal machines. Adjusting the opening degree of the rotor blades of the primary ventilator based on the detection signal of the outlet pressure of the primary ventilator and the coal flow signal, controlling the outlet pressure of the primary ventilator to a specified pressure, the pulverized coal machine When the primary ventilator blades are squeezed at high speed based on a change value of the coal flow signal accompanying the trip or stop at the time of the trip or stop, the dynamic pressure is adjusted in synchronization with the recovery of the primary ventilator outlet pressure. Primary ventilation control method for pulverized coal combustion boiler that pulls out blades.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and FIG. 2 shows a combustion air system of a coal-fired boiler according to the embodiment of the present invention. Here, 1 is the primary air vent outlet draft (pressure) detection value, 2 is a subtractor, 3 is a controller (proportional integration), 4 is a coal flow signal, 5 is a function generator, 6 is an adder, and 7 is Function generator, 8 is an adder, 9 is a function generator, 1
0 is a switch, 11 is a change rate limiter, 25 is a push-in ventilator (FDF), 26 is an air preheater, 27 is a wind box, 29 is a denitration device, 31 is an induction ventilator (IDF), and 34 is a coal bunker , 36 is a pulverized coal machine, 39 is a pulverized coal machine inlet damper, 41
Represents a primary ventilation blade, and 42 represents a primary ventilation (PAF).

In FIG. 2, air from a forced draft fan 25 is heated by an air preheater 26 and used as pulverized coal combustion air. The air from the primary ventilator 42 is heated by the air preheater 26 and used as hot air to the pulverized coal machine 36. The air that has bypassed the air preheater 26 is used as cold air for the pulverized coal machine 36. A hot air damper 37 and a cold air damper 38 control the pulverized coal machine inlet temperature to the pulverized coal machine 36. The air flow rate is adjusted by the pulverized coal machine inlet damper 39 so that the air flow rate becomes a constant ratio with respect to the amount of coal supplied to the pulverized coal machine 36. Air from one primary ventilator 42 is supplied to a plurality of pulverized coal machines 36.

As shown in FIG. 1, in the embodiment of the present invention, the coal flow signal 4 described in the conventional example is guided to a function generator 9 to generate a bias signal, and a pulverized coal machine trip (accident or the like) is performed. At the time of stop by the operator) or at the time of stop (intentional stop by the operator), the bias signal is added to the signal from the function generator 7 by the adder 8. Here, the coal flow signal 4 is a detected value of the coal flow, and when one pulverized coal machine trips, the value of the coal flow signal is also reduced in response to a command to reduce the load corresponding to one unit.

In comparison with the conventional example shown in FIG. 3, according to the embodiment of the present invention, as shown in FIG. 1, an adder 8, a function generator 9, a switch 10, and a change rate limiter (change rate changer) It is characterized by providing a speed converter 11 for converting the speed.

When a pulverized coal machine trip or stop signal is input to the switch 10, the switch 10 is operated to output the output signal of the function generator 9 via the rate-of-change limiter 11 and the leading bias by the adder 8. It is added as a (minus) signal to the primary ventilation blade opening command which is the output signal of the function generator 7.

That is, the switch 10 is 0% during normal operation.
A signal is output, and when a pulverized coal machine trip or stop occurs, the pulverized coal machine trip or stop signal automatically switches the switch 10 to the function generator 9 side. Further, the change rate limiter 11 controls to gradually return to 0% after holding the required time after inputting the negative bias signal from the function generator 9.

As described above, the leading bias (minus) signal is rapidly supplied to the primary ventilation blade 41 controlled by the primary ventilation blade opening degree command (function generator 7) based on the coal flow signal 4. The primary ventilation rotor blades 41 are throttled at full speed. The change rate limiter 11 holds this state for a required time, detects the recovery of the draft (pressure) at the outlet of the primary ventilator, and adjusts the timing to remove the bias signal. It is possible to prevent the primary ventilator outlet pressure from suddenly stopping rising. Thus, the primary ventilator 42 can be safely operated in any operation state.

As described above, the feature of the present invention is that the components 8, 9, 10, and 11 of FIG. 1 are added. Functionally, when the pulverized coal machine is tripped or stopped (for example, 1 In the conventional example of FIG. 3, the amount of coal supplied (TCF) in spite of the failure of the unit and the operation of four units from five units to four units) and the stop of the air supply to one stopped pulverized coal machine. Since the air supply is continued in accordance with the above, the pressure of the primary ventilator will be excessively increased, but in order to prevent this, in the present invention, the rotor blades are quickly squeezed once to prevent the pressure from increasing, and The signal of the rotor blade throttle is canceled at the timing when the outlet pressure is recovered.

FIG. 4 shows the operating characteristics of the primary ventilator when the embodiment of the present invention is implemented. By implementing the present embodiment, the rotor blade behavior of the primary ventilator can be operated with a margin in the danger area (fan surging area) of the primary ventilator as shown by the solid line.

As described above, the embodiments of the present invention include those having the following configuration examples and functions.

In the state where the primary draft outlet draft is controlled by the primary draft blade 41 during the load operation,
A trip signal or a stop signal of the pulverized coal machine feeds a minus bias signal in advance to a leading command (output signal of the function generator 7) of the coal flow signal 4 for controlling the primary blade moving blade control, which is a leading signal, so that the primary ventilation movement is performed. The wing 41 is rapidly throttled, and control is performed so as to remove the negative bias signal in synchronization with the recovery of the draft (pressure) at the outlet of the primary ventilator.

As described above, when the pulverized coal machine trips or stops during the load operation, the rapid rise of the primary draft fan outlet draft is suppressed by the rapid reduction of the primary blower rotor blade by the pulverized coal machine trip or stop signal. In addition, the operating point of the primary ventilator is prevented from entering the fan surging region, and stable operation of the primary ventilator is achieved.

[0027]

According to the present invention, it is possible to prevent a drastic rise in the outlet pressure of the primary ventilator at the time of tripping or stopping the pulverized coal machine during operation, and to safely continue the operation without damaging the primary ventilator. And can achieve excellent effects.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control system of a primary fan rotor blade according to an embodiment of the present invention.

FIG. 2 is a diagram showing a combustion air system of a coal-fired boiler according to an embodiment of the present invention.

FIG. 3 is a diagram showing a conventional primary ventilator control.

FIG. 4 is a diagram showing characteristics of a primary ventilator during a pulverized coal machine trip stop operation in the embodiment of the present invention.

FIG. 5 is a diagram showing characteristics of a primary ventilator during a pulverized coal machine trip stop operation in a conventional example.

[Explanation of symbols]

 Reference Signs List 1 Draft (pressure) detection value of primary air ventilator outlet 2 Subtractor 3 Controller (proportional and integral control) 4 Coal flow signal 5 Function generator 6 Adder 7 Function generator 8 Adder 9 Function generator 10 Switch 11 Change Rate limiter (speed converter) 25 Press-in ventilator (FDF) 26 Air preheater 27 Wind box 29 Denitration device 31 Induction ventilator (IDF) 34 Coal bunker 36 Pulverized coal machine 39 Pulverized coal machine inlet damper 41 Primary ventilation blade 42 Primary ventilator (PAF)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K003 AA01 AA08 AC05 BB04 BC03 BC09 CA05 CC01 DA05 RA03 RA07 3K023 BA05 BA07

Claims (2)

[Claims] 1. A pulverized coal combustion boiler having a plurality of pulverized coal machines, wherein a primary ventilator for the pulverized coal machines is provided in common with the plurality of pulverized coal machines. Adjusting the opening degree of the rotor blades of the primary ventilator based on the detection signal of the outlet pressure of the primary ventilator and the coal flow signal to control the primary ventilator outlet pressure to a specified pressure, At the time of trip or stop, the primary ventilator blade is throttled at high speed based on the changed value of the coal flow signal accompanying the trip or stop, and the timing of recovery of the primary ventilator outlet pressure and the timing of the rotor blade are adjusted. A primary ventilator control device for a pulverized coal combustion boiler, characterized in that the throttle is removed. 2. A control method in which a primary ventilator for a pulverized coal machine in a pulverized coal combustion boiler having a plurality of pulverized coal machines controls an outlet pressure of a primary ventilator commonly provided to the plurality of pulverized coal machines. Adjusting the opening degree of the moving blades of the primary ventilator based on the detection signal of the outlet pressure of the primary ventilator and the coal flow signal, controlling the primary ventilator outlet pressure to a specified pressure, When the primary ventilator blades are squeezed at high speed based on a change value of the coal flow signal accompanying the trip or stop at the time of the trip or stop, the dynamic pressure is adjusted in synchronization with the recovery of the primary ventilator outlet pressure. A method for controlling a primary ventilator of a pulverized coal-fired boiler, comprising extracting a blade of a blade.