JPH0357363B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for controlling the degree of superheating at the furnace outlet of a once-through boiler.

FIG. 1 shows a system diagram of a monotube boiler with multistage sprays. In FIG. 1, reference numeral 1 is a feed water pump, 2 is a furnace wall, 3 is a brackish water separator, 4 is a first attenuator, 5 is a first superheater, and 6
is the second superheat reducer, 7 is the second superheater, 8 is the third superheat reducer, 9 is the third superheater, 10 is the first spray control valve, 11 is the second spray control valve, 12 is the third
Showing spray control valve.

The spray control valve is a means of control to maintain the steam temperature at the superheater outlet. Therefore, the outlet temperature of each superheater is generally transiently controlled by the amount of spray injected into the attemperator at the inlet of the superheater.

By the way, in a monotube boiler, at startup, the furnace outlet is in a wet region, and the steam separator 3
There is a drain (this area is called the wet area and can be considered a drum boiler). However, as the load increases, the steam water separator 3 runs out of drain, and the point of separation of water and steam shifts to the furnace outlet, resulting in so-called monotube operation. What is important here is that the steam at the furnace exit must be superheated steam. In order to maintain this degree of superheating, there are methods such as increasing the amount of fuel, but in a monotube boiler, the fuel basically controls the main steam temperature, that is, the temperature at the outlet of the third superheater 9 in the final stage. , does not contribute to superheat degree control.

However, in the system shown in Figure 1, if we focus on the spray mentioned earlier, if we manipulate this spray amount, the flow rate of feed water passing through the furnace will increase or decrease, so the ratio of fuel to feed water at that time will change. , the heat absorption in the furnace changes.

The present invention focuses on this characteristic, and in a once-through boiler with multi-stage spray, by adding a function to the relatively first-stage spray control system to control the degree of superheating at the furnace outlet by the spray amount, the furnace outlet is always kept in the superheating range. The purpose is to keep it.

A preferred embodiment of the present invention illustrated in FIG. 2 will be described in detail below.

In FIG. 2, reference numerals 1 to 12 indicate the same elements as in FIG. Reference numeral 13 is a first superheater outlet temperature setter, 14 is a second superheater outlet temperature setter, and 15 is a third superheater outlet temperature (main steam temperature).
Setting device, 16, first superheater outlet temperature detector, 17
is the second superheater outlet temperature detector, 18 is the third superheater outlet temperature detector, 19, 20, 21 are subtractors, 2
2, 23, and 24 indicate regulators. The following elements are included in the apparatus of the present invention, and include a furnace outlet temperature detector A, a furnace outlet pressure detector B, a superheat temperature calculator C, a subtractor D, a controller E, and a high signal selector F.

Each spray control valve 10, 11, 12 has an actual outlet temperature (16,
17, 18) and is controlled by operating regulators 22, 23, 24 in order to eliminate the deviation (19, 20, 21).

Normally, the spray control system as described above is sufficient, but in the monotube operating range, consideration must be given to maintaining the superheated region in the low load range so that the steam at the furnace outlet does not become wet. Therefore, according to the present invention, in this embodiment, the superheat degree control signal is added to the first stage spray control system.

That is, the superheating temperature with respect to the furnace outlet pressure detected by the furnace outlet pressure detector B is calculated by the calculator C, and this is used as the set value. Subtractor D determines the deviation from the actual furnace outlet temperature from detector A, and controller E generates a control signal to eliminate this deviation.

A high signal selector F provided at the output of the regulator 22 of the first stage spray control system operates the spray control valve 10 based on the signal from the regulator 22 when the furnace outlet temperature is in a sufficiently overheated region. On the other hand, when the degree of superheat at the furnace outlet temperature is insufficient, the signal from the controller E is selected, and the spray control valve 10 controls the degree of superheat at the furnace outlet.

Note that if this superheat degree control is applied to the final stage spray even when there is only one spray stage or many spray stages, it will affect the exit temperature of the final superheater, that is, the main steam temperature. Good to apply to control systems.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing a once-through boiler having a multi-stage spray system to which the apparatus of the present invention is applied, and FIG. 2 is a system diagram showing a state in which the apparatus of the present invention is applied to the system of FIG. 1... Water supply pump, 2... Furnace wall, 3... Brackish water separator, 4, 6, 8... Superheat reducer, 5, 7, 9
...Superheater, 10,11,12...Spray control valve, 13,14,15...Superheater outlet temperature setter, 16,17,18...Temperature detector, 19,2
0,21...Subtractor, 22,23,24...Adjuster, A...Temperature detector, B...Pressure detector, C...
...Arithmetic unit, D...Subtractor, E...Controller, F...
High signal selector.

Claims (1)

[Claims] 1. In a spray control device for a once-through boiler having a multi-stage spray, a regulator is provided which detects the temperature and pressure at the furnace outlet and outputs a furnace outlet superheat degree control degree signal, and the output of the regulator is transmitted through a high signal selector. A spray control device for a once-through boiler, characterized in that the device is connected to an upstream spray control system.