JPS6237603A - Steam controller for boiler feed-pump driving turbine - 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 particularly relates to a boiler feed water pump drive that improves a steam pressure control method for driving a boiler feed water pump drive turbine (hereinafter abbreviated as BFP-T). The present invention relates to a steam control device for a turbine.

[Technical background of the invention and its problems]

In recent years, steam power plants have been required to operate efficiently from various perspectives such as diversification of energy situations, effective use of fossil fuels, and energy conservation. An increasing number of plants are equipped with startup functions.

Needless to say, the FCB 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 the in-plant 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 inevitably be accompanied by a huge startup loss when it is restarted the next time, so the FC8 function described above is a function that must be provided from the viewpoint of energy conservation. In addition, the BFP/T generally has a system configuration in which it is driven by main turbine extracted steam during normal operation. Since turbine bleed water cannot be removed until the load is low before and during startup of the unit, the boiler water supply during that time is generally supplied by an electric motor-driven water supply pump C (hereinafter referred to as M-BFP).

However, unit activation by M-RFP.

Although the system configuration is simple, it can be used as a backup in the event of a RFP failure, and with the aim of more efficient operation.
An increasing number of plants are equipped with a unit starting function using a turbine-driven water pump (hereinafter referred to as T-BFP). This system installs an auxiliary steam system that supplies steam as the BFP-T driving steam when main turbine extraction air cannot be used. Considering the dramatic increase in the number of stoppages, this is an important function and system from the standpoint of ensuring reliability during startup and saving energy.

Figure 2 shows a conventional boiler feed water pump drive turbine (BFP).
-T) shows the driving steam system of the turbine-driven feedwater pump (T-BFP) 1, which drives the boiler feedwater pump-driving turbine (BFP-T) 2, which is the driving steam system for the turbine T used during normal operation. In addition to the main turbine extraction system IJis of the generator G, there is an auxiliary steam system 4 that is used when the main turbine extraction system 3 cannot be used, such as during startup, extremely low load or Fe2, and Some have a high-pressure main steam system 5 that is used temporarily when transitioning to PCB operation.

When using the main turbine extraction air 3 or the auxiliary steam 4, a low pressure steam stop valve (hereinafter LP-
MSV), low pressure steam control valve (hereinafter referred to as LP-CV)
When using high-pressure main steam, it is equipped with a high-pressure steam stop valve (hereinafter referred to as 11P-MSV) and a high-pressure steam control valve (hereinafter referred to as HP-CV) that control the RFP-T.

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 is connected to a pressure detector 7. Pressure transmitter 8
．． However, the conventional BFP-T drive steam system has the following problems. Since there is a large difference between the required steam energy to drive BFP/T at unit startup and that at Fe8, it is difficult to select the auxiliary steam pressure control valve 6.
CP-T control is difficult, and in some cases, the operation may fail, and in other cases, it is necessary to select a valve with an irrational capacity.

Figure 3 shows that in recent years, with the aim of energy saving and highly efficient operation,
Figure 3 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 98' is the T-RFP operating point 2 at rated load, and point 1B' is rated load operation. A transitional operating point when transitioning from time to PCB operation.

Point ゛C' indicates the operating point passed during the unit startup process.
Also, B' indicates the turning point after PCB setting verification, and as mentioned above, at point #A', due to main turbine bleed air, point 3B'
At points B and C1, the RFP-T is driven by the high-pressure main steam system and the auxiliary steam system.

Figure 4 shows the T-BFP at the operating point of points A-C in Figure 2.
Points ac indicating the shaft power correspond to points A to C in FIG. As is clear from FIG. 4, there is a large difference in the T-BFP required power during operation between points A and C and between points a and Q. In particular, the auxiliary steam system 4, that is, the auxiliary steam control valve 6 is used to operate B, B', and C, which differ greatly from A, b', and C, respectively.

Different shaft power means different steam energy and amount of steam to drive it. Naturally, if the shaft power is large, a large amount of 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, RFP-T is LP-MSV,
Since the LP-CV and the nozzle area are manufactured with a constant area, the maximum amount of steam that can be sucked is uniquely determined within a certain range by the steam pressure on the primary side of the LP-MSV and LP-CV. You can inhale a large amount of steam,
The lower it gets, the less it gets.

Conventionally, the control pressure on the secondary side of the auxiliary steam pressure control valve 6 has been set at around the lower limit load where the main turbine bleed air starts to be removed, in order to smoothly switch to the main turbine bleed air side at as low a load as possible for the purpose of efficient operation. It was set and controlled.

However, the conventional method has the following problems. As already mentioned, the amount of auxiliary steam required varies depending on the operating point. In other words, operating point B in Figure 3
, B' is a large amount at the time of Fe2, and at the time of start-up at point C, only a small amount is required.Also, if the setting pressure of the auxiliary steam pressure control valve 6 is high, RFP-T can suck in a lot of steam, and if it is low, it will be less. . This makes selection and control of control valves difficult.
In some cases, due to insufficient amount of driving steam, boiler feed water cannot be fed to a predetermined amount, 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.

[Purpose of the invention]

The object of the present invention is to provide a boiler feed water pump that can reliably supply driving steam to the boiler feed water pump drive turbine (BFP-T) even in Fe2 conditions, and that can sufficiently cope with unit startup by the turbine drive water pump (T -BFP). An object of the present invention is to provide a steam control device for a driving turbine.

[Summary of the invention]

The steam control device for a boiler feedwater pump-driven turbine according to the present invention is a boiler feedwater pump-driven turbine drive steam system that receives drive steam selectively from the main turbine extraction system and the auxiliary steam system. The steam pressure control valve is characterized in that a control system for the steam pressure control valve is provided with a set pressure switch that switches the set pressure according to a certain condition.

[Embodiments of the invention]

The present invention will be explained below with reference to the embodiment shown in FIG.
-T) steam control system, the boiler feed water pump drive turbine (BFP-T) 2, which is directly connected to the boiler feed water pump (RFP) 1, is connected to the main power supply from the steam turbine T and generator G system during normal operation. Check valve V from turbine extraction system 3 Low pressure steam stop valve LP-M
It is driven by driving steam supplied through the SV and the low pressure steam control valve LP-eV.

Further, when the unit is started by the turbine-driven water pump (T-RFP), it is driven by auxiliary steam supplied from the auxiliary steam system 4 through the auxiliary steam pressure control valve 6 and the check valve v2. Furthermore, the high pressure main steam system 5, which is used transiently when transitioning from normal operation to PCB operation, has a high pressure steam stop valve HP-MSV and a high pressure steam control valve IP-C.
It is also configured to be driven by high pressure steam supplied through V.

Therefore, in the present invention, the auxiliary steam pressure control valve 6 provided in the auxiliary steam system 4 is connected to the low pressure steam stop valve LP-MSV by the pressure detector 7, the pressure transmitter 8, and the pressure regulator 9.
Although it is configured to control the primary side pressure to be constant, it is further provided with a set pressure switch 21 and configured to control the secondary side pressure of the auxiliary steam pressure control valve 6 to the set pressure. . This set pressure switching device 21 has a set value 1 and a set value 2, and the relationship between the two is set as set value 1 < set value 2.
The switching between these set values of 1.2 and 1.2 can be arbitrarily performed using a set pressure switching signal.

Therefore, if a small amount of steam is required, such as when the unit is started by T-BFP, control is performed by switching to the setting value 1 to smoothly switch to the main turbine bleed air in a low load range and perform high-efficiency operation. .

Further, when a large amount of steam is required, such as during PCB operation, the setting value is switched to 2 for control. As a result, t3F
Since the primary pressure of the low-pressure steam control valve LP-CV of the P-T increases, the RFP-T can draw in a large amount of steam utilization.

In this way, in the present invention, by adding the set pressure switch 21 to the control system of the auxiliary steam pressure control valve, the T-R
It can reliably support both unit startup by FP and PCB operation.

In the embodiment shown in FIG. 1, a set pressure switch 21 having a set value 1 and a set value 2 is provided,
Although the set pressure value corresponding to the pressure is switched, the present invention is not limited to this. For example, the same effect can be obtained even if separate controllers are provided and used by switching between them. be able to.

〔Effect of the invention〕

As described above, according to the present invention, the control system of the auxiliary steam pressure control valve provided in the auxiliary steam system is provided with a set pressure switch that switches the set pressure according to a certain condition.
During operation, a sufficient amount of steam is supplied to the boiler feed water pump driving turbine, and the turbine driven feed water pump (T
Efficient operation can be made possible even when the unit is started up by -RFP).

[Brief explanation of drawings]

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 (RFP) 2... Boiler feed water pump drive turbine (RFP-T)
3... Main turbine extraction system 4... Auxiliary steam system 5
...High pressure steam system 6...Auxiliary steam pressure control well 7.
...Pressure detection Ia 8...Pressure transmitter 9...Pressure regulator 21...Setting pressure switch 22...Setting pressure switching signal agent Patent attorney Yoshiaki Inomata (and one other person) - Meisui Rindo Figure 3 Figure 4

Claims (1)

[Claims] (1) In the drive steam system of the boiler feedwater pump drive turbine that receives drive steam selectively from the main turbine extraction system and the auxiliary steam system, certain conditions exist in the control system of the auxiliary steam pressure control valve installed in the auxiliary steam system. 1. A steam control device for a boiler feedwater pump-driven turbine, characterized in that a set pressure switch is provided to switch the set pressure according to the set pressure.