JPS63231105A - Boiler feedwater control system - 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 [Field of Industrial Application] The present invention relates to boiler feed water control, and particularly to water feed control suitable for automatic switching of a recirculation valve.

[Conventional technology]

As described in Japanese Patent Application Laid-Open No. 60-164106, the conventional device has a water supply pump suction flow rate of 120 mm, which is the minimum required flow rate.
% or less, the recirculation valve is closed, and when the opposite is true, it is opened to control the recirculation flow rate. Furthermore, FIG. 2 shows a system configuration of a water supply flow rate control system that utilizes the above. As shown in the figure, in the water supply flow rate control system, the signal generator 14 creates a correction amount for the recirculation valve operation, and the recirculation valve operation condition relays 15, 16.17 add it to the T-BFP bleed motor operation signal 20. 18 to pre-correct the water supply flow rate. However, when the recirculation valve operating point changes, the correction amount of water supply flow rate also changes, but no consideration was given to correction of the correction amount of water supply flow rate.

[Problem that the invention seeks to solve]

The above-mentioned conventional technology does not take into consideration the change in load of the operation correction amount of the recirculation valve, and there is a problem in that the water supply fluctuations are large when the recirculation valve is operated.

Fig. 4 is a conceptual diagram of the boiler steam system, and Fig. 5 shows the load versus pump discharge pressure and recirculation flow rate characteristics. As the figure shows, the difference between pump discharge pressure and boiler outlet pressure,
System losses increase with increasing load, pump discharge pressure, and recirculation flow rate. In the prior art, as shown in the water supply control chart for explaining the correction amount when the recirculation valve operates in FIG. 6, the correction amount when the recirculation valve operates is constant. Therefore, as shown in the conventional water supply control chart in FIG.

Water supply fluctuations were becoming large during high loads.

An object of the present invention is to determine the operation correction amount of the recirculation valve based on the water supply pump pressure, and to suppress water supply fluctuations.

[Means for solving problems]

The above object is achieved by replacing the recirculation valve closing operation correction signal generator with a function generator that varies depending on the feed water pump discharge pressure.

[Effect]

In the recirculation valve closing operation correction function generator, the correction amount changes depending on the water supply pump discharge pressure. This allows correction to be made in accordance with water supply fluctuations, thereby reducing disturbances in the water supply flow rate.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure shows the system configuration.

Water is supplied from the deaerator to the boiler using turbine-driven water pumps (hereinafter abbreviated as T-RFP) A and B, and motor 'yj.
The water is supplied by A dynamic water supply pump (hereinafter abbreviated as M-TBFP) C. The feed water pump drive turbine A 32 is controlled by the feed water flow rate control device 1.

The rotation speed is controlled by turbine bleed air controlled by the A-TBFP bleed motor 31, and water is supplied.

The same applies to the water supply pump driving turbine B.

The recirculation valve control system 2 for ensuring the minimum water supply flow rate of the water supply pump detects the discharge flow rate from the pump discharge flow rate detector 34, and transmits the signal from the pump discharge flow rate transmitter 21 to the recirculation valve closing operation monitor relay 22, 23 and 24, monitor the opening/closing operating points, and sequentially open/close the three recirculation valves 26, 27, and 28.

A multi-stage orifice 25 is provided on the valve outlet side to suppress sudden changes when the valve is opened and closed, and to return the recirculation flow rate to the deaerator.

The water supply flow rate control device 1 detects the total water supply flow rate from a water supply flow rate detector 35, and detects the total water supply flow rate using a water supply flow rate transmitter 11 and a deviation calculator 12.
, the signal connected to the proportional integrator 13 and the recirculation valve operation correction function transmitter 19 corresponding to the feed water pump discharge pressure transmitter 36 are sent to the adder 18 via the recirculation valve operation condition relays 15, 16, and 17. The operation signal 20 drives the extraction motor 31 to control the amount of water supplied.

FIG. 7 is a water supply control chart. As shown in the figure, up to a load of 25%, water is supplied by the C motor-driven water supply pump, and at higher loads, the system switches sequentially from A (B) to the A and B turbine-driven water supply pumps. In addition, when the pump discharge flow rate reaches the recirculation valve closing point, the recirculation valves close sequentially and the valve operation interlock closes the operation signal 20 only by the correction amount, but there is also a delay in the operation of the bleed motor 31, so the recirculation valve closes. Total water supply fluctuations occur due to sudden changes in the circulating flow rate.

In the present invention, the correction amount for suppressing this variation can be optimally set by the pump discharge pressure.

According to this embodiment, there is an effect of suppressing water supply fluctuations when the recirculation valve is automatically switched.

As another embodiment, the same effect can be obtained by using a load signal to determine the operation correction amount instead of using the discharge pressure transmitter.

〔Effect of the invention〕

According to the present invention, since the operation correction amount of the recirculation valve can be corrected based on the discharge pressure, it is possible to suppress fluctuations in water supply when the recirculation valve is operated.

[Brief explanation of drawings]

FIG. 1 is a system configuration diagram of an embodiment of the present invention. Figure 2 is a conventional system configuration diagram, Figure 3 is a conventional water supply control chart, Figure 4 is a boiler steam system diagram, Figure 5 is a load versus pump discharge pressure recirculation flow rate characteristic diagram, and Figure 6 is a recirculation flow rate characteristic diagram. FIG. 7 is a water supply control chart for explaining the amount of correction during operation of the circulation valve, and is a water supply control chart of the present invention. 14... Operation correction signal generator, 19... Operation correction function generator, 26, 27, 28... Recirculation valve, 31...
- Bleed motor, 32... Turbine-driven water supply pump, 3
6...Water pump discharge pressure transmitter.
,・'-Pa□≧Agent Patent Attorney Katsuma Ogawa -2'36'16ylV'/70 Engineering Z/F Power%1MλTet High School 2
-Figure

Claims (1)

[Claims] 1. A boiler feed water control system comprising a boiler feed water control system comprising a feed water flow rate control system and a recirculation valve control system, characterized in that the operation correction of the recirculation valve is performed by a function generator.