JPH0260879B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a protection device for a blower (hereinafter referred to as a fan) provided in a blower of a thermal power plant or the like.

[Background of the invention]

Wind duct system in a power plant Figure 1 shows an outline of the wind duct system to the furnace in a power plant. Reference numeral 1 designates a fan, which supplies the required amount of combustion air to the furnace 4 via the air preheater 3. 2 indicates a fan outlet common duct. The furnace 4 is equipped with a wind box inlet damper 5 and an over air damper 5 for adjusting the ventilation flow rate.
A port (hereinafter referred to as OA port damper) 6 is provided. In the air passage 7, a suction flow rate detector 8 is provided on the suction side of the fan 1, and a discharge pressure detector 9 is provided on the discharge side.

Surging Phenomenon A problem in the above wind duct system is a pulsating phenomenon in the suction flow rate and discharge pressure caused by fluctuations in the operating point of the fan 1, that is, a surging phenomenon.

This surging phenomenon will be explained below.

In order to send the required amount of air into the furnace 4 using the fan 1, the discharge pressure must be higher than the furnace pressure on the discharge side of the fan 1 plus the system loss (curve δ in Figure 2) that increases as the air amount increases. Discharge pressure is required. System loss is the loss caused by air resistance in the system shown in Figure 1 Sl.

On the other hand, fan 1 has a surging region (curve α in Fig. 2) due to its pressure characteristics, and a region in which it does not enter the surging region α in terms of operation (curve α in Fig. 2).
and δ).

Here, FIG. 3 shows a pressure characteristic curve when the fan 1 is a movable blade axial flow fan. In FIG. 3, when the surging limit points when changing the movable blade are connected, a curve α shown by a broken line is obtained, which is called a surging curve. The fourth one is a predetermined pressure characteristic curve extracted from this pressure characteristic curve.
FIG. 4 shows the movement of the fan discharge pressure with respect to the fan suction flow rate. When the fan suction flow rate is zero, the fan discharge pressure is maximum, and as the fan suction flow rate increases, the fan discharge pressure decreases, forming a recess (point C). Furthermore, when the fan suction flow rate increases, the fan discharge pressure increases again to form a convex portion (point A), and thereafter the discharge pressure gradually decreases. Here, point A indicates the surging limit, and if we are currently operating under the conditions of discharge pressure and suction flow rate at point E, if the discharge pressure increases, the trajectory from point E to point F will change. The suction flow rate decreases, and the system loss decreases accordingly, resulting in a decrease in the discharge pressure. moreover,
When the discharge pressure changes greatly, the operating point changes from point E to F.
The pressure changes from point to point D, and when the surging limit point A is reached, the pressure characteristics become reversed, and as the suction flow rate decreases, the discharge pressure also decreases. As a result, from point A to B
The operating point changes all at once, and the suction flow rate decreases rapidly. When the suction flow rate decreases, the system loss decreases and the discharge pressure also decreases, the suction flow rate recovers, and the operating point moves rapidly to point C and further to point D.

Next, when the operating point reaches point D, the suction flow rate recovers, the system loss increases again, and the operating point moves to the surging limit point A. Thereafter, the operation points are repeatedly moved from point A to point B to point C to point D to point A in the same manner, and pulsations in the suction flow rate and discharge pressure occur. This pulsating phenomenon is called surging.

Conventional preventive measures for surging phenomenon and their problems In order to prevent this surging phenomenon, conventionally an alarm circuit as shown in Figure 5 has been installed, and when the surging area is approached, an alarm is generated and the operator is notified. It was announced. This alarm circuit includes a function generator 54 that calculates an alarm curve (curve β in FIG. 2) immediately before entering the surging region α from a signal from the fan suction flow rate detector 8, and a function generator 54 that calculates the alarm curve (curve β in FIG. 2) from the signal from the fan suction flow rate detector 8, and detects the calculated value and the fan discharge pressure. and a deviation monitor 55 that calculates the deviation from the discharge pressure detected value from the device 9, and is configured to generate an alarm 56 when the deviation of both signals is less than a certain value, that is, curve β - curve γ = 0. It's summery. In response to this alarm display, the operator responded by manually operating the alarm, but in some cases, the operator's response may be delayed, and in such cases, the operating point of the fan may enter the surging region. I had to put it away. In addition, for example, dust may adhere to the movable blades, the pressure characteristics of the fan may change, system loss may increase, and other changes over time may cause the fan to enter a surging region. sudden change (especially increase)
In this case, the operating point may enter the surging region.

On the other hand, when two fans are operated in parallel (P
point), if the fan suction flow rate on one side (A machine) is reduced for some reason, the control system tries to maintain the suction flow rate necessary for the Punto, and the fan suction flow rate on the other side (B machine
Increase the fan suction flow rate of the machine. As a result,
Although the suction flow rate of the fan whose suction flow rate has been reduced is reduced, the discharge pressure of the other side is applied to the fan through the fan outlet common duct 2 (Fig. 1), so the operation There is a possibility that the point P falls into the surging area α. That is, as shown in Fig. 6, when the suction flow rate of machine A decreases during parallel operation at point P, the control system moves to the operating point where machine B compensates for the lack of suction flow rate, and each Q , becomes point R.

When surging occurs in fan 1 due to the above reasons, the discharge pressure and suction flow rate of fan 1 pulsate, causing loud noise and vibration. If this condition continues for about 20 minutes or more, fan 1 and related There are problems such as damaging or destroying equipment, severely restricting plant operation, or making it impossible to operate. If operations are forced to stop, it will particularly disrupt the supply of electricity, which is highly public interest.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a fan protection device that can protect a fan by automatically shifting the operating point to a normal safe operation area when the fan approaches a surging area.

[Summary of the invention]

In order to achieve the above object, the protection device according to the first invention of the present application calculates the discharge pressure of the fan corresponding to the surging limit of the fan based on the detected value of the suction flow rate of the fan, and combines the calculated value with the discharge pressure of the fan. When the operating point of the fan approaches a warning area located on the safe side of at least the surging limit based on the deviation from the detected pressure value, the air flow control means of the wind duct system lowers the air resistance of the relevant wind duct system. The feature is that the operation signal is output from the controller.

According to this configuration, the current suction flow rate of the fan can be automatically adjusted to an appropriate operating point according to the discharge pressure, which enables safe operation and eliminates the occurrence of failures due to delays in response as in the past. It can be prevented.

Further, the protection device according to another invention of the present application calculates the discharge pressure of the fan corresponding to the surging limit of the fan based on the detected value of the suction flow rate of the fan, and combines the calculated value with the detected discharge pressure value. Based on the deviation, when the operating point of the fan approaches a warning area located at least on the safe side of the surging limit, the controller sends an operation signal to the air volume control means of the wind duct system to lower the air resistance of the relevant wind duct system. In addition to the point that the operating state of the blower exceeds the alarm range corresponding to the surging limit, the detection signal causes the load on the blower to be reduced by a ramp command circuit. It is characterized by points.

With this configuration, not only can the operating point be automatically adjusted to an appropriate operating point at all times according to the current suction flow rate and discharge pressure of the fan, but also the load can be quickly reduced even if the surging alarm range is exceeded. Therefore, entry into the final surging state can be reliably prevented and reliability can be improved.

[Embodiments of the invention]

Next, an embodiment of the protection device according to the first invention will be described based on the drawings.

First Embodiment First, FIG. 7 shows details of the furnace 4 and its peripheral equipment. In Fig. 7, the furnace 4 has a wind duct 7.
are continuous. A fan 1 is provided in the air passage 7, a suction flow rate detector 8 is provided on the suction side, and a discharge pressure detector 9 is provided on the discharge side. A plurality of wind box inlet dampers 5 and OA port dampers 6 are provided on the inlet side of the furnace 4 in the air passage 7. Furthermore, fuel nozzles 10 are arranged downstream of the wind box inlet damper 5, and fuel F is supplied from a fuel supply pump (not shown). The supply amount is detected by the combustion stage fuel flow rate detector 11. 12 is a fuel stage air flow rate detector, 1
3 is an O ₂ detector that detects the concentration of oxygen (O ₂ ) remaining in the exhaust gas.

Next, a first embodiment of the protection device according to the present invention is shown in FIG. The ventilation system to which the protection device shown in Fig. 8 is applied consists of two systems (A system and B system) as shown in Fig. 2, and therefore the suction flow rate detector is 8A and 8A. It is assumed that two discharge pressure detectors 9A and 9B are provided.

In FIG. 8, the higher value of the discharge pressure detection signals from the discharge pressure detectors 9A and 9B is selected by a high value selector 14, and a deviation calculator 15 to be described later
given to. On the other hand, each suction flow rate detector 8A and 8
The suction flow rate detection signal from B is given to a low value selector 18 via switching relays 16 and 17, respectively. Here, the switching relays 16 and 17 are controlled by a signal setting device 19 that excludes the suction flow rate detection signal of the stopped fan when either the A-system fan or the B-system fan 1 stops. This excludes the detection signal. Low value selector 1
8 selects the suction flow rate detection value of the fan 1 that is likely to approach the surging region of either the A system or the B system during normal operation of the fan, and always operates the fan on the safe side. The suction flow rate detection signal whose low value has been selected in this way is given to the function generator 20. This function generator calculates the discharge pressure in the alarm range (β in Figure 2) corresponding to the surging limit of fan 1 (α in Figure 2) at that time based on the input low value suction flow rate detection signal. It is. The calculated discharge pressure signal is given to the deviation calculator 15.

The deviation calculator 15 calculates the difference between the high value discharge pressure value from the high value selector 14 and the calculated discharge pressure value, and outputs the difference value to the proportional controller 21. The smaller this deviation value is, the closer the operating point of fan 1 is to the discharge pressure in the warning range (β in Figure 2), and therefore the closer it is to the surging limit (α in Figure 2). means.

The proportional controller 21 gives an opening command signal to the OA port damper 6 as an air volume adjustment means in response to the above deviation value, and when the fan 1 approaches the surging region (α in Figure 2), an override operation (emergency (operation). During normal operation when fan 1 is not close to the surging region, OA port damper 6 is used to reduce generator output 2, which is the load of the plant.
2, it is controlled by a program signal operated by a function generator 23. This OA
The port damper 6 is originally used to suppress nitrogen oxides generated when nitrogen contained in the combustion air is combusted in the furnace 4, but in the present invention, in order to prevent damage to the fan 1, Generally used to exclude nitrogen oxide suppression control and prioritize the fan's protective function. Therefore, the opening command signal is given to the OA port damper 6 via the high value selector 60. 61 is an override detection relay.

According to this configuration, when the fan 1 approaches the surging area (α in Figure 2), the OA port damper 6 is overridden in the safer alarm area (β in Figure 2) to reduce system loss. By reducing the pressure, the discharge pressure of the fan 1 is lowered and the operation can be continued at the normal operating point. By overriding the OA port damper 6, the residual O ₂ concentration in the exhaust gas increases during this override operation and the efficiency of the plant decreases, but the main auxiliary fan, which is damaged, may be damaged and the repair period will be shortened. Given the enormous costs involved, temporarily reducing plant efficiency has little effect.

In addition, in the case of a plant using a compartmentalized wind box, by using the inactive wind box entrance damper 5 in addition to the OA port damper 6, and performing the same operation as the OA port damper 6, It is possible to obtain the same effect. Further, the same effect can be obtained by using the fan movable blade opening degree instead of the fan suction flow rate and keeping the other things the same as described above.

Second Embodiment In the first embodiment (Fig. 8) described above, the opening degree of the OA port damper 6 is adjusted as an override operation. Fig. 9 shows an example that takes this into consideration.
The basic components of the protection device are those shown in FIG. 8, and since the example shown in FIG. 9 is also used, the previous explanation for FIG. 8 will be used instead and will not be repeated here.

That is, in FIG. 9, the function generator 24 creates a total air amount command value from the total fuel amount FS,
Deviation calculator 2 calculates the deviation from the actual total air flow rate AS.
5. A proportional integrator 26 creates a correction signal for the required air amount command value for each combustion stage. In each combustion stage, a multiplier 27 multiplies the air amount command signal commensurate with the amount of fuel used in each combustion stage by the correction signal to create a corrected air flow rate command value. The deviation between the command signal and the signal from the air flow rate detector 12 (FIG. 7) of each combustion stage is calculated by the calculator 28, and the opening command signal for the wind box inlet damper 5 is generated via the proportional integrator 29. create. However, if the amount of air is sent to the furnace from the OA port damper 6 by override operation, the amount of air required for the entire plant is secured, but the amount of air is insufficient for the amount of fuel in each combustion stage, resulting in combustion. It may become unstable. This is because the total air flow rate includes the air flow rate contributing to combustion and the amount of air sent from the OA port, and the air flow rate in each combustion stage is insufficient by the amount sent to the OA port. Therefore, in this embodiment, as a countermeasure against this problem, in order to secure an air amount commensurate with the fuel amount in each combustion stage, the minimum safe air flow rate is determined using the function generator 30, and the high selector 31, the deviation calculator 28, and the proportional This is handled by increasing the opening degree of the windbox inlet damper 5 via the integrator 29, thereby ensuring a stable combustion air flow rate for each combustion stage. By doing so, stable combustion can be achieved.

Second Embodiment of the Invention In all of the embodiments described above, a protective operation is performed when the operating point of the fan 1 approaches the warning range (β in FIG. 2). However, in view of the public interest and importance of a stable supply of electricity,
Furthermore, there is a need to ensure the reliability of the protection function.

Therefore, in order to compensate for the case where the normal operating range still cannot be restored even after performing an override operation using the protection device shown in the first and second embodiments, an example is provided in which the load of the power generation plant is reduced. will be explained below.

First, an outline will be explained using a sequence circuit shown in FIG. When reaching the surging limit (α in Figure 2), if the operating point does not leave the alarm area despite the above-mentioned override operation, the time-limited relay (T ₁ ) is activated by the sequence circuit shown in Figure 10. Auxiliary relay (X ₁ ) 33 via 32
is operated, and its _X1 contact is used to run back to the corresponding load to protect the fan.

Furthermore, in addition to the above-mentioned detection based on the time limit, the furnace draft is detected when entering the surging warning region, and the detector 34 detects that the draft of the boiler is higher than the specified value, or the detector 34 detects that the vibration value of the fan is higher than the specified value. 35 is detected, and the auxiliary relay (X ₂ ) 37 is activated via the malfunction prevention timer by the time relay (T ₂ ) 36 under the AND condition with the contact 57 which is turned ON in accordance with the protective operation of the first embodiment. Let it work,
Runback is caused by the contacts of the auxiliary relay (X ₂ ) 37.

By running back to the specified load in the event of an abnormality in this manner, damage to the fan and the subject matter can be prevented, stable operation of the power generation plant can be performed, and reliability can be improved.

Next, the control when the runback command signals X ₁ and X ₂ outputted by the auxiliary relays 33 and 37 are generated will be explained in detail with reference to FIG.

In normal control, unit load command 3
A frequency correction signal f is added to 8 and passed through a low value selector 39, and a main turbine control valve 41 is operated by a turbine mask control device 40 to control the load. On the other hand, this unit master signal is used for main steam pressure correction.
The MSP is added to the boiler master signal, and the water supply amount control 42 operates the electrically driven water supply pump or the turbine-driven water supply pump 58 to perform water supply control. Main steam temperature correction is based on this boiler master signal.
By adding MST and using the fuel quantity control command 43, the ratio of fuel and water supply is controlled to a certain ratio by operating the light oil, heavy oil regulating valve 59, etc.

During operation under such conditions, if one of the two forced draft fans (hereinafter abbreviated as FDF) 52 trips when two forced draft fans (hereinafter abbreviated as FDF) 52 are operated, runback may occur. Therefore, the load limiter rapidly throttles down the main turbine control valve, and at the same time, the runback command circuit 4
Issue a command to 5. In the runback command circuit 45, 46 indicates a trip for one FDF, 47 indicates an induced draft fan (hereinafter abbreviated as IDF) 53, and 48 indicates a signal generator for setting a runback target load when the water generation capacity is below. There is. Usually, IDF,
The target load for FDF, trip, etc. is 50%, and the target load below the generator waterless capacity is responsible for 30% of the load, and the target load is broadly divided into two for the runback mode.

For these runback target loads, the load change rate is set by the signal generator 49, and the switching devices 50 and 5
1, through the change rate limiter 52 and switch 53, compare with the low signal selector 39, select the signal of the runback switch 53, and rapidly reduce the amount of water, fuel, and air to stabilize the condition. control can be performed. Taking FDF52 as an example, FDF
Auxiliary relay (X ₁ ) in parallel with 521 trips
By connecting the contacts 33 and (X ₂ )37 in parallel, runback operation is possible.

〔Effect of the invention〕

As described above, according to the first invention, the protection device calculates the discharge pressure of the fan corresponding to the surging limit of the fan based on the detected value of the suction flow rate of the fan, and combines the calculated value with the detected discharge pressure. When the operating point of the fan approaches a warning area located on the safe side of at least the surging limit based on the deviation from the surging limit, an operation signal is sent that causes the air volume adjustment means of the wind system to lower the air resistance of the relevant wind system. By outputting from the controller, it is possible to automatically adjust to the appropriate operating point according to the current suction flow rate and discharge pressure of the fan, so the fan can be reliably protected, and as a result, Since safe driving becomes possible, it is possible to prevent the occurrence of problems caused by delays in response as in the past.

Further, according to the second invention, it is detected that the operating state of the blower exceeds a warning range corresponding to the surging limit, and the load on the blower is reduced by a runback command circuit based on the detection signal. In addition to automatically adjusting the operating point to the appropriate operating point according to the suction flow rate and discharge pressure of the fan, even if the surging alarm range is exceeded, the load is promptly run back, thereby preventing the final surging. It is possible to reliably stop entry into the state, and reliability can be improved.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the outline of the air passage system to the furnace in a power generation plant, Figure 2 is a characteristic diagram showing the relationship between the suction flow rate and discharge pressure of the fan, and Figure 3 is the same pressure of the movable blade axial flow fan. Characteristic diagram, Figure 4 is the 3rd
Figure 5 is a circuit diagram showing a conventional alarm circuit; Figure 6 is a pressure characteristic diagram when two fans are operated in parallel. , FIG. 7 is a system diagram showing a wind duct system and peripheral equipment of a furnace to which the present invention is applied, FIG. 8 is a block diagram showing a first embodiment of a fan protection device according to the first invention, and FIG. 9 10 is a block diagram showing the second embodiment of the first invention, FIG. 10 is a sequence circuit diagram of the embodiment of the second invention, and FIG. 11 is a block diagram of the runback command circuit in the embodiment of the second invention. be. 1...Blower (fan), 7...Air duct system, 8A,
8B...Suction flow rate detector, 9A, 9B...Discharge pressure detector, 15...Difference calculator, 20...Function generator, 2
1...Proportional controller.

Claims (1)

[Scope of Claims] 1. A suction flow rate detector that detects the air intake flow rate of a blower installed in a wind duct system, a discharge pressure detector that detects the discharge pressure of the blower, and a suction flow rate detector that detects the air intake flow rate of the blower provided in the air duct system, a discharge pressure detector that detects the discharge pressure of the blower, and a A discharge pressure in an alarm range corresponding to the surging limit is calculated, and based on a deviation between the calculated discharge pressure value and the detected discharge pressure value, the operating state of the blower approaches the alarm range corresponding to the surging limit. an alarm signal generator that outputs a signal instructing the above, and an operation that instructs the air volume adjustment means of the wind duct system to reduce the air resistance of the wind duct system when the operating point of the blower approaches the warning area. A blower protection device comprising: a controller that outputs a signal; 2. A suction flow rate detector that detects the air intake flow rate of the blower installed in the air duct system, a discharge pressure detector that detects the discharge pressure of the blower, and a surging limit of the blower that corresponds to the detected value of the suction flow rate. Calculates the discharge pressure in the alarm range, and generates a signal indicating that the operating state of the blower approaches the alarm range corresponding to the surging limit based on the deviation between the calculated discharge pressure value and the detected discharge pressure value. an alarm signal generator that outputs an alarm signal; and an adjustment that outputs an operation signal that instructs the air volume adjustment means of the wind duct system to reduce air resistance of the wind duct system when the operating point of the front blower approaches the warning area. a detector for detecting that the operating state of the blower exceeds an alarm range corresponding to the surging limit; and a runback command for reducing the load on the blower based on the detection signal. A blower protection device characterized by comprising a circuit.