JPS649533B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a furnace pressure control device for balanced draft boiler equipment, and particularly to a furnace pressure control device for boiler equipment having two or more suction draft fans (hereinafter abbreviated as IDF). More specifically, the present invention provides a forced draft fan (hereinafter referred to as
This invention relates to a furnace pressure control device for boiler equipment that has a circuit that rapidly narrows down the inlet vane (or damper) of a FDF (abbreviated as FDF).

Figure 1 shows an example of a flue duct system diagram in a balanced draft boiler facility. As is well known, the smoke duct system includes FDF5B for sending combustion air into the furnace 19, and IDF13B for sucking out combustion gas from the furnace 19 and discharging it from the chimney 20.
and blowing boiler exhaust gas into the furnace 19,
It consists of gas recirculation fan (GRF) 18 etc. to control the reheat steam temperature.

In addition, 1 is an air flow rate transmitter that generates a signal according to the air flow rate sent by the FDF5B,
5A is an FDF inlet vane that controls the air flow rate;
6 is a furnace internal pressure transmitter that generates a signal according to the furnace internal pressure; 13A is an IDF inlet vane that controls the suction air volume by IDF so as to maintain the furnace internal pressure at a predetermined value; 14 is a steam-type air preheater; 17 is an air preheater.

In the balanced draft boiler equipment having the above configuration, the air flow rate sent by the FDF 5B is adjusted by adjusting the opening degree of the FDF inlet vane 5A according to the load (for example, the power generation command in the case of thermal power generation equipment). The furnace pressure is controlled by IDF to keep it within the specified value.
This is done by adjusting the opening degree of the inlet vane 13A.

An example of a conventional furnace internal pressure control device as described above is shown in FIG. In the figure, the same reference numerals as in FIG. 1 represent the same parts. 2 and 11 are function generators,
3 and 7 are subtractors, 4 and 9 are proportional/integral calculators, 5
8 is the FDF inlet vane drive device, 8 is the furnace pressure setting device,
10 and 12 are adders, and 13 is an IDF inlet vane drive device.

As is clear from the figure, the power generation command is converted into an air flow command by the function generator 2, and this value and the signal from the air flow transmitter 1 are supplied to the subtractor 3 to output a difference signal. . FDF inlet vane 5A obtained by proportional integral calculation of this difference signal
The opening command signal is supplied to the FDF inlet vane drive device 5 to adjust the opening of the FDF inlet vane 5A.

On the other hand, in order to control the pressure inside the furnace 19, FDF
The opening command signal of the inlet vane 5A is sent to the function generator 11.
is supplied to the adder 12 to obtain a preliminary control signal, which is then sent to the adder 12.
Enter. Furthermore, the deviation between the furnace pressure signal obtained from the furnace pressure transmitter 6 and the set value generated by the furnace pressure setting device 8 is calculated through a proportional/integral calculator 9.
The IDF inlet vane driving device 13 is controlled by the sum signal added to the adder 12 as an opening command correction signal for the IDF inlet vane. This allows the IDF inlet vane 13 to maintain the furnace pressure equal to the set value.
The opening degree of A is adjusted.

If one or more IDFs trip (due to overload or overvoltage, etc.) using this conventional control method, the inlet vanes (or dampers) of the tripped IDFs are rapidly throttled, and at the same time the power generation command is sent to the boiler. It is being lowered at a rate of change determined by the characteristics. As the power generation command decreases, the air flow rate command and the FDF inlet vane opening command also decrease, and the FDF inlet vane closes and the amount of air sent into the furnace 19 also decreases, so an increase in the pressure inside the furnace 19 is temporarily prevented. be done. However, the rate of decrease in the FDF inlet vane opening command due to the power generation command is generally small, and after the IDF trips,
Since it takes time for the FDF inlet vane to reduce the forced air flow rate, the furnace pressure rises abnormally and often exceeds the boiler's alarm (upper limit) value.

The object of the present invention is to prevent the FDF from tripping when one or more of the IDFs installed is tripped.
the inlet vane without waiting for the air flow command to decrease.
By rapidly narrowing down, the increase in pressure inside the furnace is suppressed,
An object of the present invention is to provide a furnace internal pressure control device that can improve the safety of a boiler in an emergency.

The present invention is capable of suppressing the pressure inside the furnace to below the allowable value when a part of the IDF, which is installed in multiple units, trips for some reason. This was done based on the fact that it was confirmed through simulation analysis that the pressure inside the furnace would rise abnormally. In order to achieve the above purpose,
The present invention adds circuitry to rapidly throttle the FDF inlet vanes if one or more IDFs trip.

FIG. 3 shows one embodiment of the present invention. The furnace pressure is
Similar to the conventional example shown in FIG. 2, the IDF inlet vane (or damper) 13A controls the furnace internal pressure using the proportional/integral calculator 9 so that it becomes equal to the set value. The difference from the conventional example shown in Fig. 2 is that a rapid narrowing circuit consisting of an FDF inlet vane opening setting device 16 and a changeover switch 15 is added after the proportional/integral calculator 4 for controlling the FDF inlet vane (or damper) opening. That's what I did. When it is detected by appropriate means that a part of the IDFs installed in the plurality of IDFs has tripped, the changeover switch 15 switches to the a contact side, and the opening degree set by the opening setting device 16 is set in advance. Rapidly narrow down the FDF inlet vane (or damper) 5A to the opening degree.

The FDF inlet vane opening set by the opening setting device 16 is, of course, determined by the number N of installed IDFs and the number m of trips. Usually N IDF1
Since 3B bears 100% of the load, when m units trip, the inlet vane opening degree is set to be equivalent to (N-m)/N% load.

For example, when the number of installed units is 2 and the number of trips is 1, the FDF inlet vane opening corresponding to approximately 50% load is set by the setting device 16, and this is set by the setting device 16.
Supplied to the FDF inlet vane drive 5. As a result, the FDF inlet vane 5A is rapidly narrowed down to the opening equivalent to 50% load without waiting for the opening command to decrease based on the decrease in the power generation command and the air flow command.

On the other hand, as the power generation command decreases at a predetermined rate as mentioned above, the air flow command and FDF
The inlet vane opening command also decreases. Then, in response to the air flow rate command, the FDF inlet vane opening command is
When the load has settled down to a value equivalent to (N-m)/N% load, the changeover switch 5 is returned to the b contact side and normal proportional/integral control is performed.

In this case, the timing of switching from the a contact to the b contact can be determined by measuring the elapsed time from the trip of the IDF13B, for example, since the rate of decrease in the boiler load (in this example, the amount of power generation) command during an emergency is known in advance. can be determined.

As explained in detail above, according to the present invention,
When a part of the IDF trips, the pressure inside the furnace cannot be controlled and rises abnormally, causing a dangerous situation when combustion gas blows out from the viewing window for observing the combustion state inside the furnace or the hole into which the soot blower is inserted. can be prevented.

Furthermore, since the target value of the FDF inlet vane opening after tripping is fixedly set, control can be stabilized without causing vibration, undershoot, or overshoot. Further, since the opening setting device has a simple structure, high reliability, and low price, even if a plurality of opening setting devices are installed, the cost does not increase and maintenance is easy.

[Brief explanation of the drawing]

Figure 1 is a system diagram of balanced draft boiler equipment, Figure 2 is a block diagram of a conventional furnace pressure control system, and Figure 3 is a diagram of a conventional furnace pressure control system.
The figure is a block diagram of one embodiment of the invention. 1... Air flow rate transmitter, 5... FDF inlet vane drive device, 6... Furnace pressure transmitter, 13... IDF
Inlet vane drive device, 16...FDF inlet vane opening setting device.

Claims (1)

[Scope of Claims] 1. A forced draft fan forces an amount of air based on the air flow rate command into the furnace, and a plurality of suction draft fans sucks air from inside the furnace to bring the pressure inside the furnace to a set value. This is a furnace pressure control method for balanced draft boiler equipment in which the air pressure is maintained, and the suction draft inlet vane opening degree is controlled according to the difference between the air flow rate signal and the air flow rate command, and multiple suction draft fans are controlled. When a part of the boiler is tripped, in response to the detection of the trip, the boiler load is reduced to a load band corresponding to the number of remaining suction fans, and during the scheduled time thereafter, the air flow command is A boiler equipment characterized by independently setting a fixed forced draft inlet vane opening corresponding to a load according to the number of remaining suction draft fans, and controlling a forced draft draft inlet vane drive device based on this. Furnace pressure control method. 2. The furnace internal pressure control method for boiler equipment according to claim 1, wherein after the scheduled time has elapsed, the forced draft fan inlet vane drive control during normal operation is automatically returned to.