JPS6014961B2 - Boiler steam temperature control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a boiler automatic control system for a thermal power plant, and in particular to a boiler automatic control system for a thermal power plant, which is capable of controlling the boiler combustion amount in advance and minimizing changes in main steam temperature during startup/stop or load adjustment. Related to automatic control equipment.

Changes in the main steam temperature of the boiler have an adverse effect on the turbine, such as thermal stress, so it is desirable that the main steam temperature be controlled so that it always remains at a constant value and does not fluctuate.

However, in reality, the main steam temperature fluctuates greatly when starting and stopping or adjusting the load, so in order to suppress this, the boiler combustion amount is controlled in advance. In other words, Boira has
It has a heat storage capacity and its response time constant is quite long, so the combustion amount (air +
Advance control of the boiler combustion amount is performed in which the combustion amount is added to the input amount of the boiler, taking into account the boiler's responsiveness and heat storage capacity in addition to the fuel). By performing this advance control, changes in main steam temperature during load adjustment as described above can be suppressed to a minimum, and responsiveness during transient times can be further improved. FIG. 1 is an example of a conventional circuit showing such a method of advance control of the boiler combustion amount. To explain its operation in detail, first, the index cooling signal from the central power supply index cooling station that collectively controls multiple thermal power plants from a distance is set to the load change rate passed through the power plant. This signal serves as a basic signal for controlling the water supply amount and combustion amount as a general cooling signal to the boiler. The signal output from the load change rate setting is subjected to a main steam pressure correction in an adder 1, and the water supply to the boiler is controlled via a feed water control system 3. Furthermore, the output signal 1 is the advance signal obtained via the load change advance control system 5 in the adder 2, the advance correction signal obtained through the feedback advance correction system 6 based on the desuperheater outlet steam temperature, and the main steam The correction signals obtained via the temperature feedback final correction system 7 are added. That is, these preceding and modified signals are superimposed on the basic signal, which is the output of 1, and the combustion amount of the boiler is determined via the combustion amount control system. In FIG. 1, the result of combustion amount control appears as a change in the attemperator outlet steam temperature and the main steam temperature. That is, the fact that these steam temperatures deviate from the set values indicates that the combustion amount control is not being performed properly.

Therefore, feedback correction based on these steam temperatures, especially advance correction based on the steam temperature at the desuperheater outlet, plays an important role. According to the slave circuit shown in FIG. 1, it can be expected that main steam temperature changes due to load fluctuations, etc. can be suppressed to a minimum by performing advance control of the combustion amount.

However, because the time constant of the boiler, particularly the response time of the steam temperature, is long, the phosphorus return correction based on the steam temperature tends to be delayed, and the results of main steam temperature control during load fluctuations are not necessarily satisfactory. The present invention has been made with attention to the above points, and the boiler steam temperature is capable of suppressing changes in the main steam temperature by using the temperature change of the boiler evaporator tube, where the combustion amount control result appears far away, as a feedback advance correction signal. The purpose is to provide a control device. Fig. 2 is a circuit diagram showing one embodiment of the present invention. In the figure, the same reference numerals as in Fig. 1 represent the same or equivalent products, and the drawings will be referred to below. This will be explained in detail.

In the figure, 8 is a rate-of-change calculator (for example, a differential calculator) for detecting the temperature change of the evaporation tube, and 9 is for adding the signals of these rate-of-change calculators and sending them all together to the advance correction circuit 6. belongs to. In other words, the temperature change in the evaporator tube is
The magnitude of the output of the rate of change calculator 8 changes depending on the degree of the rate of change. In addition, this rate of change calculator 8
Since the magnitude (height and medium) of the output signal can be set arbitrarily, it is possible to differentiate the output signals of each rate-of-change calculator. For example, the rate of change calculator signal on the inlet side of the evaporation tube can be made larger than that on the outlet side for the same temperature change.
A similar effect can also be achieved by providing an addition/subtraction calculator in place of the rate of change calculator 8 and sending the deviation to the adder 9 when the temperature of each evaporator tube deviates from a preset value. As described above, according to the present invention, feedback correction of steam temperature in combustion amount control can be performed faster and more precisely than before, so changes in main steam temperature during boiler load fluctuations can be suppressed, and stable control can be performed. becomes possible.

[Brief explanation of drawings]

FIG. 1 is a drawing showing an example of a conventional control circuit, and FIG. 2 is a drawing showing a control circuit which is an embodiment of the present invention. 1...Adjustment valve, 2...Adjustment valve, 3...
・...Water supply control system, 4... Combustion control system, 5...
- Load fluctuation advance control system, 6... Feedback advance correction system, 7... Feedback final correction system, 8... Addition/subtraction unit. Figure 1 Figure 2

Claims (1)

[Claims] 1. In a boiler steam temperature control device, a means for detecting the temperature at multiple locations of the boiler evaporation pipe and detecting the rate of change thereof as the steam temperature feedback correction signal, and outputting the signals after calculating the multiple rate of change at once. A boiler steam temperature control device comprising: means.