JPS6399403A - Steam controller for boiler feed pump driving turbine - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention particularly aims to provide a stable supply of steam for driving a boiler feedwater pump drive turbine (hereinafter abbreviated as BFP-T). The present invention relates to a control device for a boiler feed water pump driving turbine.

(Conventional technology) In recent years, efficient operation of steam power plants has been called for from various viewpoints such as diversification of energy situations, effective use of fossil fuels, and energy conservation.As part of the countermeasures, P
CB (first cut back) driving function and B
The number of plants equipped with a plant start-up function using FP-T is increasing.

Needless to say, the PCB operation function shuts down the power plant (unit) in operation if it becomes impossible to transmit power from the power plant due to an unexpected accident on the power transmission system side. This refers to a rapid load narrowing function that quickly shifts to extremely low load operation equivalent to a predetermined load, continues operation or stands by, and quickly transmits the requested load after the power transmission system is restored.

Once a thermal power plant is stopped, it will unavoidably cause huge losses the next time it is restarted, so the above-mentioned PCB
This function is a must-have feature from the perspective of energy conservation.

Furthermore, during normal operation, the BFP-T generally has a system configuration in which it is driven by main turbine oil/steam.

Since turbine oil cannot be removed before the unit is started and during the start-up process when the load is low, boiler water is generally supplied to the boiler during that time by a motor-driven water pump (hereinafter abbreviated as M-BFP).

However, although the system configuration for starting a unit using M-BFP is simple, an increasing number of plants are equipped with a unit starting function using a turbine-driven water pump (hereinafter abbreviated as T-BFP) for the purpose of further energy saving. This will install an auxiliary steam system to supply steam when the main turbine oil cannot be used as RFP-T driving steam, and will help power plants start up and shut down due to the diversification of electricity demand in recent years. Considering the logical increase in the number of times, this is an important function/system from the standpoint of ensuring reliability at startup and saving energy.

Figure 2 shows a conventional boiler feed water pump drive turbine (RF
The drive steam system of P-T) is shown. BFP-T2, which drives T-BFPl, can use the main turbine extraction system 3 as its drive steam system during startup, extremely low load, Fe2, etc., in addition to the main turbine extraction system 3 used during normal operation. Some have an auxiliary steam system M4 that is used when the PCB is not available, and a high-pressure steam system 5 that is used transiently when transitioning from normal operation to PCB operation. A low pressure steam stop valve (hereinafter referred to as LP-MSV) and a low pressure steam control valve (hereinafter referred to as LP-CV) that control the BFP/T when using the main turbine extraction air 3 or auxiliary steam 4, and the high pressure main steam 5, the high pressure steam stop valve (hereinafter referred to as HP-MSV) and high pressure steam control valve (hereinafter referred to as H
P-CV).

Furthermore, since the source pressure of the auxiliary steam system is generally higher than the main turbine extraction pressure, an auxiliary steam pressure control valve 6 is provided.

The auxiliary steam pressure control valve 6 includes a pressure detector 7, a pressure transmitter 8,
The pressure regulator 9 and the like control the primary steam pressure of the LP-MSV to be constant.

However, the conventional BFP-T drive steam system has the following problems. In other words, when the unit starts up, the BF
Because there is a large difference between the required steam energy to drive the PT and that during PO2, it is difficult to select an auxiliary steam pressure control valve, and as a result, it is difficult to start the unit or control the BFP-T during Fe2. PCB operation may fail, resulting in unit shutdown or otherwise forcing selection of an irrational capacity valve.

Figure 3 shows that in recent years, with the aim of energy saving and highly efficient operation,
shows an example of the T-BFP system resistance curve of a transformer plant that is adopted in most new plants. In Figure 3, point "A'" is the T-BFP operating point at rated load, point "B" is a transient operating point when transitioning from rated load operation to PCB operation, and C++ is the unit startup process. indicates the operating point passed through. Also, point "B"' is FCB
Shows the operating point after settling. Then, as mentioned above, point ″′A
At point 1 (B711), high-pressure main steam and auxiliary steam system
and II C++, the BFP-T is driven by an auxiliary steam system.

Figure 4 shows the T-BFP at the operating point of points A-C in Figure 3.
The 0 point a '' c indicating the shaft power of corresponds to points A-C in Fig. 3. It can be seen that there is a large difference in the required power for T-BFP between points a and c.Especially, there is a large difference in the required power for T-BFP at points B, B', and C, which operate using the auxiliary steam system 4, that is, the auxiliary steam pressure control valve 6.・Zoresu, b'
It is very different from c.

The fact that the shaft power of the T-BFP is different means that the steam energy and amount of steam for driving it are different. Naturally, if the shaft power is large, a large amount of driving steam is also required, so the capacity of the auxiliary steam control valve 6 needs to be selected assuming a large amount. On the other hand, BFP-T is LP
-Since MSV, Lp-cv and nozzle area are constant, L
The maximum suctionable steam amount is uniquely determined within a certain range by the primary steam pressure of P-MSV and LP-CV, and if the secondary pressure is high, a large amount of steam can be sucked.

If it is low, the amount will be small.

Conventionally, the pressure on the secondary side of the auxiliary steam pressure control valve 6 has been set at a lower limit load at which main turbine extracted steam begins to be taken, in order to smoothly switch to the main turbine oil/air side at as low a load as possible for the purpose of efficient operation. The pressure is set to be equivalent to the nearby main turbine bleed pressure.

has been controlled.

(Problems to be Solved by the Invention) However, the conventional method has the following problems.

As already mentioned, the amount of auxiliary steam required varies depending on the operation. That is, during operation B in Fig. 3,
When B' is FCB, the amount is large, and when 1 point C is activated, it is small. Further, if the set pressure of the auxiliary steam pressure control valve 6 is high, the RFP-T can suck in a large amount of steam, and if the set pressure is low, the amount of steam can be sucked. Therefore, it becomes difficult to select a control valve, and in some cases, boiler feed water cannot be fed to a predetermined level due to insufficient amount of driving steam, which may result in failure of PCB operation.

PCB operation is an important function as mentioned above, and it is a problem that must be solved as soon as possible to ensure success.

The purpose of the present invention was made in view of the above problems.
Even at time B, the boiler feedwater pump drive turbine (
An object of the present invention is to provide a steam control device for a boiler feedwater pump-driven turbine that can supply sufficient driving steam to a boiler feedwater pump (T-BFP) and can sufficiently cope with the unit startup by a turbine-driven feedwater pump (T-BFP).

[Means for solving the problem] In the drive steam system of a boiler feed water pump which receives drive steam selectively from the main turbine extraction system and the auxiliary steam system, a system is provided in the auxiliary steam system. A boiler characterized in that an automatic valve is provided in parallel with the auxiliary steam pressure control valve, and the automatic valve is automatically opened when the low-pressure steam control valve of the boiler feed water pump driving turbine reaches a certain opening degree or more. Water pump drive turbine.

(Function) The steam control device for a boiler feedwater pump-driven turbine according to the present invention is applied to the auxiliary steam system in the drive steam system of the boiler feedwater pump-driven turbine that selectively receives drive steam from the main turbine extraction system and the auxiliary steam system. By bypassing the installed auxiliary steam pressure control valve and installing an automatic valve that automatically opens and closes according to certain conditions, the unit can be activated,
It can reliably support any type of PCB operation.

(Example) The present invention will be explained below based on the example shown in FIG. Also in the steam control device for a boiler feed water pump drive turbine according to the present invention, a boiler feed water pump drive turbine (BFP-T) 2 directly connected to a boiler feed water pump (RFP) 1 is provided.
is driven by driving steam from the main turbine oil and gas system 3 during normal operation, and by driving steam from the auxiliary steam system 4 when the unit is started by T-BFP. It is also configured to be driven by high-pressure main steam supplied from the high-pressure main steam system 5, which is used transiently when transitioning from normal operation to PCB operation.

Therefore, in the present invention, the auxiliary steam pressure control valve 6 provided in the auxiliary steam system 4 is controlled by the pressure detector 7, the pressure transmitter 8, and the pressure regulator 9 to keep the primary pressure of the LP-MSV constant. However, an automatic valve 10 is further provided to bypass the auxiliary steam pressure control valve 6, and the LP-M
It is configured to be able to supply steam to the SV. and,
An LP-CV opening transmitter 21 and an alarm setting device 22 are provided which output an automatic valve control signal 23 that automatically opens an automatic valve when the LP-CV opening exceeds a certain value.

Therefore, when a small amount of steam is required, such as when starting up a unit using T-RFP, driving steam is supplied by the auxiliary steam pressure control valve 6, and switching between main turbine oil and air is performed smoothly and at a low load, thereby increasing efficiency. Perform operations.

Also, when a large amount of steam is required, such as during FC/BJ conversion, use L.
The opening degree of the P-CV increases in order to allow a corresponding amount of steam to flow. However, the main characteristic of LP-CV is that when the opening exceeds a certain degree, the ratio of the increase in flow rate to the increase in opening decreases, making control difficult, and as a matter of course, once the opening is fully opened.

-As long as the next pressure is constant, more steam than can be sucked in when fully opened cannot be sucked in.

In order to prevent such problems, the automatic valve 10 is activated by bypassing the auxiliary steam pressure control valve, and the automatic valve 10 is activated when the LP-C opening degree transmitter 21 and the LP-CV opening degree exceeds a certain value. A notification setting device 22 is provided to output a valve opening signal.

When the LP-CV opening degree exceeds the upper limit opening degree of the control range, by opening the automatic valve 10, the LP-CV next-side pressure, which had been under pressure reduction control by the auxiliary steam pressure control valve 6, increases. do. Due to the characteristics of steam, as the pressure increases, the specific volume decreases, so when flowing the same weight flow rate,
If the LP-CV-next pressure is low, the LP-CV opening degree becomes large, and conversely, if it is high, the LP-CV opening degree becomes small.

Therefore, a large amount of steam is required during PCB operation, etc., and LP-
When the CV opening degree is close to the upper limit, the automatic valve 10 is opened and the LP
-CV- By increasing the next pressure, the LP-CV opening degree decreases, making it possible to control with a margin. 1. Although this embodiment has been explained using the opening transmitter and alarm setting device of the LP-CV, a position detector (limit switch, etc.) is used to know the opening of the LP-CV, and the It goes without saying that the same effect can be obtained by using a signal.

[Effects of the Invention] As described above, in the present invention, by providing an automatic valve by bypassing the auxiliary steam pressure control valve, and further providing an LP-C opening degree transmitter alarm setting device, unit startup by T-BFP is achieved. , PCB operation can be handled reliably.

[Brief explanation of the drawing]

FIG. 1 is a steam system diagram showing an embodiment of the steam control device for a boiler feedwater pump-driven turbine according to the present invention, FIG. 2 is a steam system diagram showing a conventional steam control device for a boiler feedwater pump-driven turbine, and FIG. 4 is a system resistance curve diagram of a boiler feed pump of a variable pressure plant, and FIG. 4 is a required power curve diagram of a boiler feed pump. 1... Boiler feed pump (BFP) 2... Boiler feed water pump drive turbine (BFP-T)
3... Main turbine extraction system 4... Auxiliary steam system 5
...High pressure steam system 6...Auxiliary steam pressure control valve 7...Pressure detector 8...Pressure transmitter 9.
...Pressure regulator 10...Automatic valve 21...
Low-pressure steam control valve opening transmitter 22...Alarm setting device 23...Automatic valve control signal agent Patent attorney Noriyuki Chika Yudo Hirofumi Mitsumata Figure 1 Figure 2

Claims (1)

[Claims] In the drive steam system of the boiler feed water pump, which receives drive steam selectively from the main turbine extraction system and the auxiliary steam system, an automatic valve is installed in parallel with the auxiliary steam pressure control valve installed in the auxiliary steam system to drive the boiler feed water pump. A steam control device for a boiler feed water pump driven turbine, characterized in that when a low pressure steam control valve of the turbine reaches a certain opening degree or more, the automatic valve is automatically opened.