JPS6091111A - Controller for temperature of steam of boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a steam temperature control device for a boiler in a coal-fired power plant.

Steam temperature control in conventional thermal power plants generally uses the desuperheater outlet temperature and the Nupre valve opening determined by each load (determined by static characteristics) as preliminary control elements, but in coal-fired plants However, depending on the type of coal, the degree of adhesion of the slab to the boiler tube, or the operation of the suit blower, the Nuple flow rate (i.e. Nuple valve opening) at each load changes. Opening cannot be used as a leading signal.

However, advance signals are essential for steam temperature control in coal-fired plants, where the boiler response is slower than in heavy oil-fired plants. It is no exaggeration to say that improving temperature controllability depends on what kind of advance signal is used.

The present invention has been made in view of the above circumstances, and is a power generation plant that uses fossil fuel as fuel and controls steam temperature by obtaining a control output according to the desuperheater outlet temperature and the superheater outlet temperature. means for generating an output signal corresponding to the amount of fuel that changes depending on the load of the power plant; and a detection means for detecting the amount of fuel actually supplied and outputting a signal corresponding to the detected amount. , means for subtracting this surface output signal to obtain a difference signal, and the control output is provided with a means for subtracting the surface output signal, that is, a signal of the difference between the fuel amount determined by static characteristics and the actual fuel amount. By adding a component and using it to control the steam temperature, in addition to controlling the spray valve opening according to the conventionally used desuperheater outlet temperature detection output and superheater outlet temperature detection output, static characteristics The spray valve opening can be controlled to reflect the difference between the amount of fuel and the actual amount of fuel.As a result, unlike conventional methods, the spray flow rate can be applied depending on the load regardless of the boiler condition, or the spray amount can be adjusted according to the load as required. This eliminates the problem of 7G entering or not entering when it is not available, and dramatically improves the controllability of steam temperature in power generation glands that use fossil fuels such as coal, heavy oil, and gas. An object of the present invention is to provide a steam temperature control device for a boiler.

That is, the present invention utilizes the difference between the amount of fuel determined by static characteristics and the actual fuel, instead of the prior signal of valve opening determined by static characteristics, which has been commonly used in the past. In other words, “fuel amount determined by static characteristics”
This is because it hardly changes depending on the boiler condition and can be used in all operating conditions. The present invention can be applied not only to coal-fired power plants but also to a wide range of heavy oil or Ganu-fired power plants.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a control system diagram of the device of the present invention. In the figure 1
2 is a desuperheater outlet temperature detector that detects the desuperheater outlet temperature;
is a superheater outlet temperature detector that detects the superheater outlet temperature, 3
is a fuel detector that measures the amount of fuel. Further, 4 is a differentiator, which differentiates the temperature detection signal measured by the desuperheater outlet temperature detector 1.

5 is the superheater outlet temperature detector 2 for a set value S corresponding to the optimal value of the superheater outlet temperature set in advance by a subtracter.
Calculate the difference el between the detected temperatures.

A controller 6 receives the difference signal output from the subtracter 5 and outputs a control signal to make it zero. A seven-digit adder adds the control signal from the controller 6 and the differential output from the differentiator 4 and outputs the result.

8 is a subtracter, 9 is an adder, 10.12 is an upper/lower limiter, 1
1 is a function generator. Of these, the function generator 11 receives information on the load and generates an output indicating the amount of fuel determined based on the correspondence with the load according to the static characteristics of the boiler. 8 obtains the difference between the fuel amount measured by the fuel amount detector 3 and the output of the function generator 11. Further, when the level of the difference signal (deviation e2) outputted from the subtracter 8 exceeds a predetermined range, the upper and lower limit limiter 12 cuts and outputs the exceeded level. The output of the limiter 12 and the output of the subtracter 8 are added and output. Further, the upper/lower limit limiter 10 outputs the output of the adder 9 by limiting it to within the upper/lower limits so that the output of the adder 9 does not exceed the specified level. 10, the output of the controller 6, and the output of the differentiator 4 are added and output.

Reference numeral 13 denotes a main steam temperature spray control valve which receives the output of the adder 7 and controls the valve opening according to the output level.

Next, the operation of this device having the above configuration will be explained.

The temperature measured by the superheater outlet temperature detector 2 is compared with the set value S by a subtractor 5, and its deviation e is calculated.

The controller 6 sends a control signal to make the value zero.

Furthermore, in order to compensate for the delay in temperature response, the temperature measured by the desuperheater outlet temperature detector 1 is differentiated by a differentiator 4 and sent to an adder 7, where it is used as a preceding signal. On the other hand, the fuel amount determined by the boiler static characteristics is determined by the load and function generator 11, and is compared with the fuel amount measured by the fuel amount detector 3 by the subtractor 8, and a signal corresponding to the deviation e2 is sent to the adder. 9 and the upper and lower limit limiters 12.

Then, the upper/lower limit limiter 12 applies a limit to the input signal e2 that exceeds a predetermined level range, and supplies it to the adder 9. Then, the two inputs are added by the adder 9, and after being limited by the upper and lower limit limiter 10 so that the level does not exceed predetermined upper and lower limits, the signal is sent to the adder 7.

The adder 7 adds the output of the upper and lower limit limiter 10, the output of the controller 6, and the output of the differentiator 4, and then provides the added output to the main steam temperature null control valve 13. As a result, the main steam temperature spray control valve 13 is controlled by a control amount corresponding to the output.
is activated and the valve opening is controlled to perform temperature control. Here, the purpose of the upper/lower limit limiter 12 is to double the e2 signal in order to use the deviation e2 more effectively, and the purpose of the upper/lower limit limiter 100 is to suppress excessive movement of the null control valve. It has been established.

If we use the conventional static characteristics of the Nuple valve opening determined by the static characteristics of the load, the Nuple flow rate will be input depending on the load regardless of the boiler condition, and the Nuple flow may enter when it is not needed or may not enter. However, in the case of the present invention, as shown in the time chart of FIG. 2, in order to reduce the effect on temperature when excessive fuel is input,
A similar effect can be expected by introducing Suru in advance and vice versa.

Here, FIG. 2 will be briefly explained. FIG. 2 shows a case where the load increases at a constant rate; as the load increases, the output from the function generator 11 also increases in response.

On the other hand, since the amount of fuel also increases as the load increases, the output of the fuel amount detector 3 also increases accordingly. The output of the fuel detector 3 and the output of the function generator 11 are calculated by a subtracter 8.
As a result of subtraction, an output (deviation) e2 as shown in FIG. 2(d) is obtained. This deviation e2 is given to an adder 9 and an upper/lower limit limiter 12, and the upper/lower limit limiter 12 cuts off a portion of the deviation e2 that exceeds a predetermined level range as shown in FIG. 2(e). Give to 9.

Therefore, the adder 9 adds the output of the upper/lower limit limiter 12 and the output of the subtracter 8. As a result, the output of the adder 9 is such that the output e2 of the subtracter 8 is within the limit range of the upper/lower limit limiter 12. For the portion within , the change @ is doubled, and for the portion exceeding the limit range, the amount of change is the limit level plus the level 02.

This provides an output that effectively reflects the difference between the fuel amount determined by the static characteristics and the actual fuel amount.

Then, this output is transmitted to the upper and lower limit limiter 10 to suppress excessive movement of the main steam temperature null control valve 13, and to control the controller 6,
In order to sufficiently reflect the output of the differentiator 4, the output exceeding a predetermined limit range is cut and sent to the adder 7.

As a result, the output of the adder 7 is determined by the difference between the fuel amount and the actual fuel amount due to static characteristics in addition to the spray valve opening control according to the conventionally used desuperheater outlet temperature detection output and superheater outlet temperature detection output. It is now possible to control the opening of the spray valve to reflect the current flow rate, which prevents the flow rate from being applied depending on the load regardless of the condition of the boiler, or leakage when it is not necessary, or from not entering when it is not necessary. This eliminates the problem of sagging, and dramatically improves the steam temperature controllability of power plants that use fossil fuels such as coal, heavy oil, and GANU. In addition, it can sufficiently cope with changes in characteristics due to contamination of the boiler in a power generation plant, and it does not require complicated calculations and can be configured with an ordinary analog control device, making it possible to easily and inexpensively implement the synutem.

As detailed above, the present invention provides a power generation plant that uses fossil fuel as fuel and controls the steam temperature by obtaining a control output according to the temperature at the outlet of the desuperheater and the temperature at the outlet of the superheater. A means for generating an output signal corresponding to the amount of fuel determined according to the load of the plant, a detection means for detecting the amount of fuel actually supplied and outputting a signal corresponding to the detector, and a means for generating the output signal corresponding to the amount of fuel determined according to the load of the plant, means for subtracting the signal to obtain a signal of the difference, and adding the component of the signal of the difference, that is, the signal of the difference between the fuel amount determined by the static characteristics and the actual fuel amount, to the control output and converting it into steam. Since it is used for temperature control, in addition to the spray valve opening control according to the conventionally used desuperheater outlet temperature detection output and superheater outlet temperature detection output, it also controls the fuel amount and actual fuel % based on static characteristics. It is now possible to control the spray valve opening to reflect the difference in p1. Therefore, unlike conventional methods, the spray flow rate is applied depending on the load regardless of the boiler condition. Steam temperature control for boilers has the characteristics of eliminating the problem of water leakage and being able to dramatically improve steam temperature control in power plants that use fossil fuels such as coal, heavy oil, and gas. equipment can be provided.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram showing one embodiment of the present invention, and FIG. 2 is a time chart showing an example of the operation of its main parts. 1... Desuperheater outlet temperature detector, 2... Superheater outlet temperature detector, 3... Fuel amount detector, 4... Differentiator, 5
．． 8... Subtractor, 6... Controller, 7,9... Adder, 10.12... Upper and lower limit limiter, 11... Function generator, 13... Main steam temperature spray control valve. Applicant Sub-Attorney Patent Attorney Takehiko Suzue No. 11 No. 20

Claims (1)

[Claims] In a power generation plant that uses fossil fuel as fuel and controls steam temperature by obtaining a control output according to the temperature at the outlet of the desuperheater and the temperature at the outlet of the superheater, the amount of fuel determined according to the load of the power generation plant is controlled. means for generating a corresponding output signal; detection means for detecting the amount of fuel actually supplied and outputting a signal corresponding to the detected amount; and means for subtracting this Okayama force signal to obtain a signal of the difference. A steam temperature control device for a boiler, characterized in that a component of the difference signal is added to the control output and used for controlling steam temperature.