JPS5938507A - Controller for turbine driving feed pump - 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] [Technical Field of the Invention] The present invention relates to a main water supply control system for a thermal or nuclear power plant, and particularly relates to a water supply control equipment in which a boiler feed water pump (hereinafter abbreviated as BFP) is driven by a turbine. .

[Technical background of the invention]

In recent years, with the increase in the number of large-capacity nuclear power plants, nuclear power plants are being operated for paceload purposes, while thermal power plants are being increasingly used for middle-class operations. Middle operation means that thermal power plants have a load adjustment function that allows them to operate at high loads when there is high demand for electricity, such as during the day, and at low loads when demand for electricity is low, such as at night. The low-load operation of automobiles is becoming more and more of a problem.

Due to the characteristics of the equipment, it is unavoidable that the plant thermal efficiency of steam power generation equipment decreases to a certain extent during low-load operation, but in light of rising fuel costs, it is best to operate the plant with as good a thermal efficiency as possible. Above, it is becoming important.

Against this background, in contrast to so-called constant-pressure operating plants in which the main turbine main steam pressure was kept constant over the entire load range and the steam pressure at the main turbine inlet was controlled using a regulating valve, the main turbine Variable pressure plants have been adopted that lower the main turbine load by lowering the main steam pressure while keeping the regulator valve fully open. As a result, the throttling loss caused by the soil turbine regulating valve has been significantly reduced, and as will be explained next, the shaft power of the f2 BFF has also been significantly reduced, resulting in a marked improvement in plant thermal efficiency during low force loads ( There are 7.

Hereinafter, a conventional water supply control system in a constant pressure operation plant will be explained with reference to FIGS. 1 and 2. Note 1: N1 shows the water supply control characteristics, and FIG. 2 shows the water supply control system.

In Figure 1, the vertical axis indicates the boiler local water supply pressure.
The horizontal axis shows the water supply separation corresponding to the plant output. Curve 1. ．． Arbitrary rotation speed of BFP for 2, 3, 4.5 cylinders 1 each nl+ n2+ n8+ n4+ n5 (nl >
nz > n8 > n + > n5) B F P in l2
Ly:') Q, -Hl't! In addition, the straight line 6 shows the main turbine steam pressure, and the curve 7 shows the boiler required pressure, that is, the BFP outlet pressure.

In Fig. 2, the required feed water flow number (hereinafter referred to as water supply command) IO from the boiler feed water flow control system (not shown) in the conventional water supply control system is the feed water pump driving turbine (hereinafter referred to as BFP). -T) Subpart 1! The ir, p, yp input to the F system 1 is provided in the discharge system, and the gauze valve 2:
Actual water supply flow button from the water supply flow detection detector 12 on the output 1-1 side of 3 (compared with No. A 1; 3). And BFP-T
1 water supply command 10 and actual water supply flow rate 1 for control device i<7.11
To eliminate the deviation of No. 8 and 13 (2. BFP-Ti
tt control signal No. 14 is output.

BFP-T sub section 1 signal 14 BP'P-T low pressure regulator valve 1
5 and the opening degree of the BFP-T high pressure regulating valve 16, the rotation speed of the RFP-T 17 is controlled. BFP-T
17, the discharge f4 of BypJ8 also changes, which is detected by the detector 12 in the water supply flow, and the actual water flow 13 is fed back to the BFP-T control system fiV-13+-, as described above. , the water supply command 10 is controlled so that there is no deviation from the water supply command 10.

In addition, the BFP-T drive steam and [7] low pressure steam supplied during reverse normal operation, and pressure atrophy, which is supplied as backup if the amount of steam is insufficient with only low pressure steam. It is generally adopted to establish a system.

Low-pressure steam is supplied from the BFP-T low-pressure steam pipe 19 to the BFP-T low-pressure regulating valve ■5 in red, and high-pressure steam is supplied from the BFP-T high-pressure steam pipe 20 to the BFP-T high-pressure regulating valve 16, respectively, to the BFP. - supplied to T17. The steam worked by BFP-T17 is sent to the exhaust pipe 21. It is exhausted through the exhaust valve 22. In general, the main turbine extraction air is often used as the low-pressure steam source, and the main turbine main steam is often used as the high-pressure steam source. If sufficient steam is not available, high pressure steam is supplied.

PCB operation is also called isolated operation within the plant, thermal power generation tN,
However, if the power transmission becomes impossible due to an accident on the lees side, the plant will be stopped. The idea is to operate the power plant alone at an extremely low load, and then stand by so that the load can be quickly increased to a predetermined level and power transmission can be restarted after the fault on the grid side is restored. Thermal power plants (Hanno) have a problem with thermal power plants (Hanno), because once a plant is stopped, there is a large startup loss when it is restarted. Providing the so-called FOB operation function has become particularly difficult in terms of the thermo-economics of a single nibrant, along with the adoption of the variable voltage operation mentioned above.

Figure 3 shows the water supply control characteristics of a variable pressure operating plant. 1st
Parts that are the same as those in the figure (two parts will be described using the same numbers).

The vertical and horizontal axes are the same as in FIG.

Curves 1.2, 3, and 4.5 are similar to FIG.
Arbitrary rotation speed of FP nl+ n2+ n9+ n++
n5 (nl > n2 > n8 > n+ > n+
), curve 8 shows the main turbine main steam pressure brim curve 9 shows the boiler required pressure, that is, BFP
The water supply control system indicating the outlet pressure is almost the same in a variable pressure plant as shown in Fig. 2 and in a conventional constant pressure plant.

As is clear from FIGS. 1 and 3, compared to a constant pressure plant, in a variable pressure plant, the water pump discharge pressure is significantly lower at partial load, that is, when the feed water flow rate is low. As a result, as shown in FIG.
41), that of a variable voltage operation plant (curve 42)
It can be seen that the lower the load, the more f''L decreases.

[Problems with background technology]

As mentioned above, variable pressure operating plants have a large advantage in terms of thermal economy than constant pressure operating plans, but the following problems have arisen in variable pressure operating plants.

In other words, during low load and FOB operation, BFP-
Since the T output can be reduced, the EFP-T exhaust temperature rises, making it impossible to continue operation.

Due to its mechanical characteristics, the internal efficiency of RFP-T decreases as the output becomes a partial output of 1 for the rated output C, as shown in FIG. Furthermore, because of the partial output, the amount of steam required to drive the RFP-T is also reduced. As a result, the number of droplets decreases, the friction loss per revolution increases, and the exhaust temperature rises. Especially when the load is extremely low, there is a tendency that low-pressure main steam cannot be obtained, so high-pressure steam is supplied. Since high-pressure steam has a higher temperature than low-pressure raw steam, the exhaust temperature tends to be higher than that of low-pressure raw steam.

If the bleed air temperature rise exceeds the limit value, RFP-T
This will not only damage the exhaust valve, but also cause thermal expansion of the exhaust pipe.
As a result of changes in BFP-T alignment, a phenomenon of increased vibration of RFP-T was observed, and finally, BFP-T
- In this case, a separately provided electric motor-driven BFP is generally used to deal with the problem, but this results in a decrease in plant efficiency [-7, which results in loss of thermoeconomic gain. Moreover, the inability to operate the low-load special C2 RFP-T is a major restriction on plant operation, and the above-mentioned increase in exhaust gas temperature is a problem that must be resolved as soon as possible.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned problems, and is designed to prevent the exhaust temperature from exceeding the limit value at low loads, and to prevent T, -B
The purpose is to operate FP and BFP-T safely over a wide range of load bands and to maximize thermoeconomic gain.

[Summary of the invention]

According to the second aspect of the present invention, in the turbine body water supply pump, the throttle valve provided on the front 8 side water supply pump discharge side and the E3
When the FP-T exhaust temperature exceeds the value, the exhaust
A turbine-driven water pump control HIA waste is provided, characterized in that the throttle valve is controlled by the corpse detector output signal f2.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The same parts as in FIG. 2 (two parts are given the same numbers and will be described as 7).

FIG. 5 shows an exhaust temperature detector 51, an exhaust temperature signal 52, a controller 53. Exhaust temperature setting device 54. Water supply throttle valve 55
．． 2 shows a turbine-driven feedwater pump feedwater control system in accordance with the present invention with a controller output signal 56 added to FIG. 1;

When the BFP-T exhaust temperature is lower than the operating limit value, such as when the plant is under heavy load, the RFP is controlled using the same method as before.

At times of low load or FOB, etc., the boiler water requirement is reduced, so the number of water supply commands 10 is reduced. Therefore, in order to match the actual water supply flow rate with the water supply command value, RFP-T
By the BFP-T control signal 14 from the control device 11, B
F P =T low pressure (high pressure) regulating valve 15 (, 16) operates to reduce the rotation speed of BFII8, and as a result, B
The output of FP-T is reduced, and the actual water supply flow 14 is changed to the water supply command value (
- Controlled to a proportionate amount.

In such a state, the RFP-T exhaust temperature rises as described above.

The exhaust gas temperature signal 52 from the exhaust temperature detector 51 provided in the BFP-T exhaust pipe 21 is input to the controller 53. Controller 531d: The BFP-T is set to the extraction temperature for operation. Compare the exhaust temperature setting signal 57 from the exhaust temperature setting device 54 and the exhaust temperature signal 52,
When the RFP-T exhaust temperature exceeds the set temperature, the water supply throttle valve control signal 56 is outputted so that the temperature approaches the set temperature by -55.

The water supply throttle valve 55 receives the throttle valve control signal 56 and operates toward the closing side. Due to this operation, the BFP discharge flow rate is temporarily reduced by C, but the decreased flow rate is detected by the feed water bullet detector 12, and the actual feed water flow negative signal 13 (2) is output as the water supply command 10 by the BFP-T control device 11. After comparison, the BFP-T control unit 11 outputs the water supply amount corresponding to the water supply command value.
A B F'P-T output increase command is issued as the FP-T control signal 14.

With this command, the BFP-T output is increased, an appropriate amount of water is delivered, and the BFP-T exhaust temperature is
The reason why the exhaust gas temperature decreases by increasing the BFP-T output in this way will be explained with reference to FIG. 6.

In the 6th I, s PMS is RFP-T main steam pressure, PRX is BFP-T exhaust pressure, AFl! is the theoretical adiabatic thermal drop, UFi, UP' is the effective adiabatic thermal drop %TIT' when the expansion line is 61.62, respectively.
62 is shown.

Here, the following relationship exists between AFl, UEt, UEt:' and the BFP-T internal efficiency η, η'(η<η').

(η and η' indicate the internal efficiency at BFP-T output and L', respectively) UF! =AFiX'7 1
UB=AE × 1 In addition, according to Figure 7, %BFP-T
As already mentioned, the internal efficiency improves as the output increases due to the mechanical properties of BFP-T.

Therefore, increasing the output of RFP-T from L to L' will improve the internal efficiency from η to η',
This increases the effective adiabatic heat drop of RFP-T compared to the theoretical adiabatic heat drop (2,
Therefore, BF'P-'r exhaust temperature #L decreases from T to T'.

〔Effect of the invention〕

In this way, according to 'honshusu', from the foot of the foot, FOR
It is possible to operate the turbine-driven water supply valve over a wide range of load ranges, including extremely low loads such as operation, making it easy to succeed in FOR operation, and eliminating stoppages and startup losses due to plant stoppages. At the same time, it is possible to safely operate the plant with T-BFP even in low-load operation, and a large gain in terms of thermoeconomics can be obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the water supply control characteristics of a constant pressure operation plant, Figure 2 is a schematic system diagram showing a conventional water supply control system, and Figure 3 is a diagram showing the water supply control characteristics of a constant pressure operation plant.
Figure 4 shows the water supply control characteristics of a variable pressure operation plant, Figure 4 shows the BFP shaft power characteristics, Figure @5 is a schematic system diagram showing the water supply control system according to the present invention, and Figure 6 shows the BFP shaft power characteristics.
FIG. 7 is a diagram showing an FP-T expansion line bottle, and FIG. 7 is a diagram showing BFP-T internal efficiency characteristics. 10...Water supply command 11...BFP-T control device 12...Water supply bullet detector 17...BFP-T
■8...BFP 21...BFP-
T exhaust pipe 51...BFP-T exhaust temperature detector 53...Controller 54...BFP-T exhaust temperature setting device 55...Ship water throttle valve (7317) Agent Patent attorney Noriyuki Chika (Female 1) name) W42 Figure 5

Claims (1)

[Scope of Claims] In a device that compares a water supply command signal with an actual flow rate signal at a pump outlet and calculates a deviation signal to control the opening degree of a control valve provided at a turbine inlet, the exhaust temperature of the turbine is detected,
A controller is installed to match this actual temperature signal with a predetermined signal from the setting device and to play with the deviation signal.
The output of the controller is applied to a water supply throttle valve at the pump outlet to control the opening degree of the water supply throttle valve. Control device for turbine-driven water pumps,.