JPS6156402B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides for the
The present invention relates to a turbine bypass device that directs high-temperature, high-pressure steam from a steam generator to a condenser bypassing a turbine, and particularly relates to a turbine bypass device that can realize safe and reliable operation.

In thermal power plants, nuclear power plants, etc., steam is generated using heat generated in boilers, nuclear reactors, etc., and this steam is sent to a steam turbine to rotate the turbine.
The steam turbine then generates electricity by rotating a directly connected generator. The steam flowing into the steam turbine expands and performs work within the steam turbine, consuming its internal energy, becoming lower temperature and lower pressure, and is discharged to a low heat source such as a condenser.

In such thermal power and nuclear power plants, high thermal efficiency is basically obtained by configuring the Rankine cycle. To achieve this, it is necessary for the condenser to release the latent heat of the incoming steam to the outside of the system, and the condenser makes this possible by using natural low-temperature cooling water such as ocean river water. .

By the way, power plants are normally operated with independent power loads, but these loads are connected to many power plants through power transmission cables. Then, synchronous operation is performed with a load corresponding to the capacity of the power plant in the wide range of power loads. Therefore, an abnormality in the power transmission system may cause an accident that cuts off the power transmission system from the required power plant, or an accident may occur in the turbine system within the power plant, or even a sudden stoppage of another power plant due to an accident may result in power generation being interrupted. In any case where an excessive load exceeding the machine's capacity is applied, the power plant's load shedding interlock is activated and the power plant enters an emergency operating state.

Since the load shedding occurs instantaneously, the steam turbine is placed in a state of rapid load fluctuation, and the residual steam in the turbine casing operates to accelerate the steam turbine whose load has been drastically reduced. Therefore,
It is necessary to release residual steam outside the vehicle compartment as quickly as possible to prevent accidents caused by impeller overspeed.

On the other hand, boilers and nuclear reactors themselves have a large heat capacity, so even if a burner is suddenly extinguished or a fuel control rod is inserted, the amount of steam generated will respond with a first-order lag and will not follow sudden changes. It is impossible to do so. Particularly in nuclear reactors, the amount of evaporation may even temporarily increase. In addition, in turbine plants, once the turbine, boiler, or reactor is stopped, it takes a considerable amount of time to restart the plant, which not only reduces the operating efficiency of the plant but also causes economic problems in some cases. It will also be a loss.

For this reason, turbine bypass devices have traditionally been installed to discharge steam to the condenser without passing through the turbine in such cases, without shutting down the boiler or reactor, until the system can be restored. It is being

FIG. 1 shows a turbine plant including a conventional turbine bypass device. Note that, since there is no change in the gist of both thermal power plants and nuclear power plants, for the sake of simplicity, a system diagram of a thermal power plant is shown in the figure, and the following explanation will be based on this diagram.

For example, in a supercritical pressure plant, the steam generated in the boiler 1 is 246 kg/cm ² g, high temperature and high pressure steam of 538°C, and this steam is sent to the main steam system 2.
and flows into the high pressure turbine 4 via the main stop valve 3. The steam leaving the high-pressure turbine 4 returns to the boiler 1 again through the low-temperature reheat steam pipe 5, is reheated by the reheater 6 of the boiler 1, and passes through the high-temperature reheat steam pipe 7 to the intermediate-pressure turbine 8. Inflow. Medium pressure turbine 8
The steam that exits is further guided to the low pressure turbine 9 and finally flows into the condenser 10. Condenser 1
The low-temperature, low-pressure steam that has flowed into the boiler 1 is cooled and becomes condensed water, and this condensed water is returned to the boiler 1 via the condensate pump 11 and the boiler water supply system 12.
The whole constitutes a closed cycle.

On the other hand, the turbine bypass device
A system that branches off from the boiler 1 and is connected to the desuperheater 15 via the high-pressure bypass valve 13 and the low-pressure bypass valve 14, and sends the steam from the boiler 1 to the desuperheater 15, which further reduces the pressure and temperature of the steam and sends it to the condenser 10. , branched from the outlet piping of the condensate pump 11, connected to the water chamber 18 of the attemperator 15 via the quick-open valve 16 and piping 17, and a system for supplying cooling water to the attemperator 15. .

In the above configuration, during normal operation, the high-pressure bypass valve 13, the low-pressure bypass valve 14, and the quick-open valve 16 are all closed, and no fluid flows into the bypass device.

When the load cutoff interlock is activated, the main stop valve 3 is instantaneously closed by the turbine trip signal, and the high pressure bypass valve 13 and the low pressure bypass valve 14 are suddenly opened. In addition, in order to prevent high-temperature steam from flowing into the condenser 10, the quick-opening valve 16 is designed to be opened with priority over both bypass valves 13 and 14, and its operating time is 0.2
It is a very short time, about 0.4 seconds.

The conventional device described above has the following problems.

That is, the quick-open valve 16 is installed close to the attemperator 15 because it is necessary to quickly supply cooling water to the attemperator 15 after the quick-open valve 16 and the attemperator 15 are opened.
There is no cooling water in the pipe 17 connecting the water chamber 18 and the water chamber 18 before the quick-open valve 16 is opened. Therefore, after the trip, the quick-opening valve 16 opens suddenly, and the cooling water flows into the pipe 17 at a high speed, causing the wall surface and the water to collide with each other in the water chamber 18.

The discharge pressure of the condensate pump 11 is 16 to 18 Kg/cm ² g
Immediately after the quick-opening valve 16 suddenly opens inside the pipe 17, the cooling water flows into the water chamber 18 as a high-speed flow of, for example, about 18 m/s or more. Therefore, the pressure of the water in the water chamber 18 generated by the collision of this water is as high as 230 kg/cm ² g. The occurrence of such an impulsive pressure is called a water hammer phenomenon, but the pressure generated by water hammer causes many strength problems for structures, so the occurrence of an impulsive pressure is called a water hammer phenomenon. need to be suppressed.

Note that opening the quick-opening valve 16 slowly can prevent the generation of shocking pressure, but high-temperature steam will flow into the condenser 10, which will seriously affect the structural strength of the condenser 10. This is not desirable.

The present invention was devised to solve these conventional problems, and its purpose is to provide a turbine bypass device that can be expected to operate reliably and safely.

The present invention focuses on the fact that the conventional difficulty lies in the fact that there is no cooling water in the piping connecting the quick-opening valve and the water chamber of the desuperheater before the quick-opening valve suddenly opens. The interior is kept filled with cooling water even when the quick-open valve is closed.

The present invention will be explained below based on an embodiment shown in FIG.

In the figure, 14 is a low-pressure bypass valve installed at the same location as the conventional example shown in FIG. It is connected to the water dispenser 10. In the water chamber 18 of the desuperheater 15,
Cooling water is supplied through the quick-open valve 16 and piping 17, respectively, to lower the temperature and pressure of the steam passing through the attemperator 15. The configuration described above is the same as the conventional example shown in FIG. 1, and the following configuration is further added in this embodiment.

That is, the primary side and the secondary side of the quick-open valve 16 are connected to each other by a bypass pipe 19 having an orifice 20 as shown in the figure, and even when the quick-open valve 16 is in the closed state, the bypass pipe 19 can be connected to the bypass pipe 19. Cooling water is always supplied to the pipe 17 through the pipe. The orifice 20 is designed so that enough water is always supplied to fill the water chamber 18 of the desuperheater 15 with water.

Next, the effect will be explained.

During turbine operation, cooling water (condensate) is constantly supplied into the pipe 17 via the bypass pipe 19,
The inside of the water chamber 18 and the inside of the pipe 17 are filled with water.

When the turbine bypass system interlock is activated, the low pressure bypass valve 14 is momentarily opened and high temperature steam flows into the attemperator 15. At the same time, the quick-opening valve 16 opens, and the temperature and pressure of the steam passing through the desuperheater 15 is lowered by the cooling water. On this occasion,
Since the inside of the pipe 17 and the inside of the water chamber 18 are already filled with cooling water before the quick-open valve 16 is opened, the cooling water does not collide with the wall surface of the water chamber 18 or the water collides with each other. There is no generation of high pressure due to water hammer phenomenon.

As explained above, according to this embodiment, generation of high pressure due to water hammer phenomenon can be effectively prevented, and safe operation is guaranteed. In addition, since the piping and water chamber are always filled with water, a predetermined amount of cooling water is supplied to the desuperheater without delay at the same time as the quick-open valve is opened, allowing the desuperheater to fully perform its function. I can do it.

In the above embodiment, a case has been described in which the quick-open valve 16 is provided with a bypass pipe 19 having an orifice 20, but the quick-open valve 16 is equipped with a sub-valve so that the sub-valve can be operated even when the main valve is closed. It may be left open. Even with this configuration, it is possible to obtain the same effects as in the above embodiment.

In addition, the present invention can achieve its purpose by constantly supplying cooling water into the piping 17 and the water chamber 18 so that they are fully filled with water, so for example, as shown in FIG. Piping 1 through 21
7 and the water chamber 18 may be supplied with cooling water from a water supply source. At this time, if the pressure in the system 21 is higher than the pressure on the primary side of the quick-open valve 16, it is sufficient to simply insert a flow regulating device such as an orifice, but if the pressure is low, As shown, it is preferable to provide a check valve 22 on the primary side or secondary side of the flow rate regulating device. This results in
After the quick-open valve 16 is opened, it is prevented from adversely affecting other systems.

The present invention has been described above based on preferred embodiments, and according to the present invention, reliable and safe driving can be expected.

[Brief explanation of the drawing]

FIG. 1 is a system diagram of a steam turbine cycle including a conventional device, FIG. 2 is a sectional view showing one embodiment of the present invention, and FIG. 3 is a system diagram showing another embodiment of the present invention. 1...Boiler, 4...High pressure turbine, 8...Intermediate pressure turbine, 9...Low pressure turbine, 10...Condenser, 15...Desuperheater, 16...Quick opening valve, 18...
Water chamber, 19... Bypass piping, 20... Orifice, 22... Check valve.

Claims (1)

[Scope of Claims] 1. A system that leads high-temperature, high-pressure steam generated in a steam generator directly to a low-temperature source via a desuperheater without passing through a turbine, and a system that quickly opens the water chamber of the desuperheater. In a turbine bypass device equipped with a system that supplies cooling water via a valve to cool and depressurize steam passing through a desuperheater, the cooling water is supplied into the piping connecting the quick-open valve and the water chamber and the water chamber. A turbine bypass device equipped with water supply piping to maintain a full water state at all times. 2. The turbine bypass device according to claim 1, wherein the water supply pipe is a bypass pipe that bypasses the quick-open valve. 3. The turbine according to claim 1, wherein the water supply pipe is a pipe that supplies water from a water supply source different from both systems into the pipe that communicates between the attemperator and the quick-open valve. Bypass device.