JPH04116303A - Boiler gas recirculation controller - Google Patents

Abstract

PURPOSE:To prevent troubles such as burnout of a duct that is a part of furnace hopper, by controlling the outlet pressure of a gas recirculation fan within a specified range according to fluctuations in the outlet pressure of the furnace. CONSTITUTION:The furnace pressures are measured to seize the operating state of a boiler, however, they greatly fluctuates in a short length of time. Therefore, the furnace pressures are measured by a furnace pressure transmitter 16 and satisfactorily averaged by a primary delay relay 17 to examine a major trend of changes in operation state of the boiler. A target value of furnace outlet pressure is produced by a function converter 20 according to a load demand signal (MW demand) 12, and a proportional control signal is produced by a deviation arithmetic controller 18 according to the target value and the actual measured pressure signals, i.e., the output of the primary delay relay 17 which removes minor fluctuations from the outputs of the furnace outlet pressure transmitter 16, so that the delivery pressure set value of a recirculating fan (GRF) is corrected within an allowable correction range of an upper-lower limiter 19. Thereby, the delivery pressure of GRF is automatically controlled within a specified range corresponding to changes in the operating state of the boiler.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a boiler waste recirculation control device,
This invention relates to a device that automatically controls gas recirculation in response to changes in conditions due to aging, etc.

[Conventional technology]

The objectives of gas recirculation system control are broadly divided into the following two.

(1) The steam temperature at the reheater outlet is controlled by controlling the amount of gas recirculated from the furnace boiler.

(2) Control the NOX value by controlling the amount of gas recirculated to the primary gas duct and winbox, that is, the amount of gas recirculated to the burner combustion air.

In order to achieve the objective of "L", the following control is carried out. The dirt will be explained based on FIG.

Figure 1 is a system diagram of a waste circulation device in a boiler.
In the figure, 1 is a waste recirculation fan (hereinafter simply referred to as GRF)
, 2 is a gas mixing fan (hereinafter simply GMF),
3 is a furnace with hopper] damper, 4 is a rodan bar with GRE,
5 is a primary gas damper, 6 is a GMF outlet-] damper,
Reference numeral 7 indicates a GMF input rotor damper as a windhox, 9 indicates a primary castact, 10 indicates a G RF outlet pressure transmitter, and 11 indicates a pressure controller.

In such a device, the control of the reheater outlet steam temperature for the above purpose () is achieved by controlling the furnace hopper inlet damper 3 after exiting the gas recirculation fan 1, and also for the purpose (2). To control NOx, after leaving the gas recirculation fan 1, it passes through the wind box 8, and a gas mixing fan 2 is installed to obtain the pressure necessary to mix it with the burner combustion air. Next gas duct 9
Then, the gas amount is controlled by the GMF output locomotor 6 and the force damper 5.

As described above, in order to control the reheater outlet steam temperature and NOX value, the required amount of waste is taken from each system. At this time, in order to perform stable control at all times, it is necessary that the pressure at the outlet of the gas recirculation fan does not fluctuate from a certain predetermined value.

For this purpose, the JRF outlet is measured by the GR output rotary pressure transmitter 1°, and the GRF input rotary damper 4 is controlled by the pressure controller 11.

By the way, the furnace hopper artificial damper 3. -Next gas damper
, cMF output L'' In order to perform stable and effective control of the damper 6, it is necessary that the difference in sweat at the entrance and exit of this damper falls within a certain range.

In order to do so, the gas recirculation fan 1 must be
It is necessary to control the outlet pressure.

This method will be explained with reference to FIG. The figure shows a GRF outlet control circuit, where 12 is a load demand signal (MW demand) such as a power generation command, 13 is a function converter that converts the load demand signal into an outlet pressure value of the gas recirculation fan 1, and 15
G R by correcting the output of the RF outlet pressure transmitter 10
This is a controller that sends a control signal to the F person L1 Gaskumper 4.

That is, the MW demand 12 is converted to the pressure at the outlet of the gas recirculation fan 1 of each load by the function converter] 3, and this converted value is compared with the value measured by the GRF outlet transmitter 10 in the controller 15, Based on this, the controller 15 outputs a GRF input Rozoro damper control signal.

[Problem that the invention seeks to solve]

In the conventional device as described above, controlling the G RF outlet pressure,
The pressure value set by MW Temando 12 and the actually measured GRI? Since it is controlled only based on the output L1 pressure value, it cannot respond to changes in the condition due to aging of the boiler, for example. Immediately, due to dirt on A H, △
In cases such as when the P increase rate changes due to changes over time,
If the same calorific value is to be obtained, the GRF outlet pressure should be set differently, but in the conventional device described above, the actual situation is that the pressure at the GRF outlet is set depending on the operating situation.

In addition, with the above device, it is necessary to increase the α value by the increase in furnace pressure in view of aging, which also has the disadvantage of increasing the power loss of the GRF.

[Failure to solve the problem]

The present invention has been made in view of the above points, and includes a recirculation pressure setting means for setting the gas recirculation fan outlet pressure based on a load request signal, and a recirculation pressure setting means for setting the gas recirculation fan outlet pressure during operation. m circulating pressure detecting means for detecting, and the circulating pressure detecting means 1;
recirculation pressure correction means for correcting the gas recirculation fan outlet pressure set by the recirculation pressure setting means based on the output of the stage, the gas recirculation fan outlet pressure being adjusted by the output of the recirculation pressure correction means; A boiler gas recirculation control device configured to control the furnace gas recirculation within a predetermined range, comprising: a furnace pressure setting means for setting the furnace outlet pressure based on a load request signal; a furnace pressure detection means for detecting the furnace outlet pressure during operation; Furnace pressure correction means for correcting the furnace outlet pressure set by the furnace pressure setting means based on the output of the furnace pressure detection means; and an adder for applying the output of the furnace pressure correction means to the recirculation pressure correction means. It has a furnace exit I.
It is characterized by controlling the gas recirculation fan outlet pressure within a predetermined range based on pressure fluctuations.

[Effect]

In the above configuration, the furnace output pressure preset by the load request signal is corrected by the detected actual furnace pressure. This correction output is applied to a separately formed waste recirculation fan outlet pressure correction output 11 as a correction signal for controlling the gas recirculation fan outlet pressure. Therefore, the required waste recirculation fan outlet pressure can be appropriately controlled in response to changes in furnace pressure that are caused by aging of the boiler.

[Embodiments of the invention]

An embodiment of the present invention will be described based on FIGS. 1 and 2.

The system threshold shown in Fig. 1 is common to the conventional device, and the GRF output control path shown in Fig. 2 is obtained by adding some necessary circuits to the conventional control circuit already explained. There is.
In the adding circuit, 13 is a converter, 14 is an adder, 16 is a furnace output pressure transmitter, 17 is a second lag device, 18 is a controller 1-roller, 19 is an upper and lower limiter, and 20 is a function converter. It is. It is desirable that such a circuit be added to the control circuit of the conventional device in consideration of the stability of the entire control system.

A good way to detect changes in boiler conditions is to measure furnace pressure. However, furnace pressure is highly variable in the short term. The sag measured by the furnace pressure transmitter 16 is sufficiently leveled by the primary lag device 17 to grasp the tendency of large changes in the condition of the boiler. The controller 18 compares the dust with the furnace pressure set value created from the MW demand 12 of the conventional control circuit and converted by the function converter 20, and uses the comparison result as a correction signal via the -1-lower limit limiter]9. and is applied to the adder 14. The correction using the correction signal is performed by ratio sequence control in order to perform a long-term correction operation, and the :1 controller 18 is not provided with an integral element.

In addition, since the furnace pressure fluctuates greatly in a short period of time, there is a possibility that it will cause disturbance, so the upper and lower limiters 19
This will put a stop to it and prevent it from running out of control.

As explained above, in this embodiment, the target value of the furnace outlet pressure is created from the MW demand by the function converter 20, and small fluctuations in the actually measured furnace pressure signal, that is, the output of the furnace pressure transmitter 16, are removed. A proportional control signal is generated by the first-order delay relay 17 and the deviation calculation controller 18, and the RF outlet pressure set value is corrected by the correction width allowed by the lower limit limiter 19.

Therefore, by correcting the set value due to a large trend in the furnace pressure, the G R and F outlet pressures can be automatically controlled within a predetermined range in response to changes in the boiler condition. ffU can be done.

In the above embodiment, the MW demand 12 is the load request signal of the present invention, the function converter 13 is the gas recirculation pressure setting means, the controller 15 is the recirculation pressure correction means,
Furnace pressure transmitter 16 is furnace pressure detection means, function converter 2
0 corresponds to the furnace pressure setting means, the controller 18 corresponds to the furnace pressure correction means, and the GRF output pressure transmitter 10 corresponds to the recirculation pressure detection means, respectively.

In the embodiment shown in FIG. 2, the output of the MW demand 12 is sent to the controller 1-roller 18 via the function relay 20.
If a setting circuit for setting the number of GRF output pressure set values for the furnace pressure signal is provided between the primary delay relay 17 on the output side of the furnace pressure transmitter 16 and the deviation calculation controller 18, the function relay 20 is not required. The same effect can be obtained.

〔Effect of the invention〕

The present invention is as explained above, and the furnace pressure changes over time.
Since the GRF outlet pressure is always 1α higher than the temperature rise, recirculation gas does not flow due to a change in the furnace pressure, and troubles such as duct burnout in a part of the furnace hopper can be prevented. Additionally, fluctuations in the flow rate of recirculated gas supplied from the GRF to the furnace are reduced, and there are advantages such as stable control of NOx, which allows operation without fluctuations in RH steam temperature. -(α→α) can be set to a small value, which has the effect of reducing the power loss of the GRF compared to the current situation where the +α value is increased in anticipation of aging.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of a boiler gas recirculation control device used in the present invention, and FIG. 2 is an explanatory diagram of main parts of a conventional control circuit and a control circuit of the present invention. ]...Gas circulation fan, 10...GR
F output pressure oscillator 2...MW demand, 1
3...Function converter, 14...Adder,
15... Controller I roller, 16... Furnace pressure transmitter, 18... Controller. =20

Claims (1)

[Scope of Claims] Recirculation pressure setting means for setting a gas recirculation fan outlet pressure based on a load request signal; recirculation pressure detection means for detecting the gas recirculation fan outlet pressure during operation; recirculation pressure correction means for correcting the gas recirculation fan outlet pressure set by the recirculation pressure setting means based on the output of the pressure detection means; A boiler gas recirculation control device configured to control pressure within a predetermined range, comprising: a furnace pressure setting means for setting a furnace outlet pressure based on a load request signal; a furnace pressure detection means for detecting the furnace outlet pressure during operation; Furnace pressure correction means for correcting the furnace outlet pressure set by the furnace pressure setting means based on the output of the furnace pressure detection means; and an adder for applying the output of the furnace pressure correction means to the recirculation pressure correction means. and has
A boiler gas recirculation control device that controls gas recirculation fan outlet pressure within a predetermined range based on fluctuations in furnace outlet pressure.