JPS5817330B2 - High pressure turbine rotating shaft cooling method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention controls the amount of cooling steam and the salinity of the cooling steam by using the variation of the salinity of the high-pressure first stage and the main steam humidity with respect to time as control factors when starting up or when the load change is significant. According to
This invention relates to a cooling method in which the variation of humidity in a cooling chamber with respect to time is kept almost constant, thereby reducing thermal stress exerted on a high-pressure rotating shaft and life consumption.

In recent years, in power generation plants, there has been an increase in the number of daily start-stop operations and cycling operations in which the load is lower than the rated load to the minimum load even during one day.

The steam turbines used in such power plants are required to shorten the startup time and increase the rate of load change, but in response to these demands new problems arise regarding thermal stress and life consumption of the turbine rotating shaft. It has become difficult to operate steam turbines as required.

FIG. 1 shows changes in the main steam humidity Ts, the first stage layer temperature Ti, and the primary superheat inlet depth Tb when the steam turbine is started or when the load changes.

According to this, since the main steam humidity Ts and the initial layer temperature Ti change rapidly, the thermal stress and thermal fatigue applied to the high-pressure rotating shaft will be reduced during cycling operation.
It is understood that the life of the high-pressure rotating shaft is shortened.

In order to extend this lifespan, it is necessary to reduce the sudden temperature change to a gentler force, but this requires a lot of time to start up or change the load, which simply does not meet the above requirements. However, the fuel consumption associated with this cannot be ignored and the economic loss will also be large.

Therefore, if it is required to shorten the start-up time or load change rate time, consideration must be given to suppressing the thermal stress, thermal fatigue, and increasing life consumption rate that occur in the high-pressure rotating shaft. It is.

Conventionally, management of thermal stress and life consumption rate for high-pressure rotating shafts has depended on the temperature of the first stage layer, but in order to reduce life consumption, a method of operation with a constant load has been adopted.

However, although operation with a constant load is desirable, it does not meet actual conditions, and there is therefore a need for a steam turbine that is capable of cycling operation while reducing lifetime consumption.

An object of the present invention is to reduce the life consumption of a high-pressure rotating shaft in a steam turbine capable of cycling operation.

For this purpose, the present invention is designed to reduce the amount of change in the high pressure first stage layer temperature and main steam temperature to a constant value, since the temperature of the high pressure first stage and the main steam temperature increase over time at startup or when the load change is significant. or more, supply cooling steam whose salinity and amount are controlled to the cooling chamber of the high pressure time axis based on the variation,
It is characterized by reducing thermal stress and life consumption on the high-pressure rotating shaft.

The present invention will be explained below with reference to FIGS. 2 to 5.

First, FIG. 2 will be explained in order to explain the present invention in detail.

As already mentioned, at startup or when the load change rate is large, the magnitude of the change ΔT/Δt of the main steam temperature Ts and the high-pressure first stage temperature Ti with respect to time is small, so this magnitude is greater than a certain value. In this case, cooling steam whose temperature and amount are controlled is applied to the cooling chamber of the high-pressure rotating shaft to keep the temperature change in the cooling chamber almost constant over time and protect the high-pressure rotating shaft from sudden temperature changes. It is.

FIG. 3 shows a block diagram of a steam turbine system according to the present invention.

As shown in the diagram, the primary and secondary super heaters 2.1
Main steam is supplied to the high-pressure turbine 17 and then to the intermediate-pressure turbine 18 via the reheater 3. However, in the present invention, the high-pressure rotating shaft of the high-pressure turbine 17 is to be cooled. be.

According to the present invention, the cooling steam supplied from the steam mixing header 10 to the high-pressure rotating shaft of the high-pressure turbine 17 via the cooling steam on-off valve 16 is compared to the main steam system and the inlet system of the primary superheater 2 or the main steam. It is extracted from a high-pressure, low-temperature steam source.

The main steam from the main steam system passes through the flow control valve 9, and the steam from the primary superheater 2 population system passes through the valve 5, moisture separator 6, valve 7, or after passing through the valve 4. The steam is taken into the steam mixing header 10 via the flow rate regulating valve 8, but the moisture separator 6 is provided to remove moisture if the boiler is a drum type because it contains moisture.

By taking the cooling steam into the steam mixing header 10 through the flow rate regulating valves 8 and 9 in this manner, at least the salinity of the cooling steam becomes lower than that of the main steam, and the flow rate regulating valves 8 and 9
By controlling the opening and closing of the valve 16, cooling steam of a controlled amount and temperature is applied to the high-pressure rotating shaft.

The opening/closing control of the flow rate regulating valves 8 and 9 is controlled by a thermocouple 12 that measures the temperature inside the steam mixing header 10, a thermocouple 11 that measures the temperature of the cooling chamber after the high-pressure first stage, a thermocouple 19 that measures the steam temperature after the high-pressure first stage, etc. This is done based on the output of

The arithmetic circuit 13 is for that purpose.

Further, the opening/closing control of the valve 16 is performed by an arithmetic circuit 15 which receives as input the outputs of thermocouples 14 and 19 that measure the main steam temperature and the first-stage post-stage steam temperature, respectively.

As shown in Fig. 4, the cooling steam controlled in this way is led to the cooling chamber 22 through the cooling pipe 20, and then flows from the balance hole 21 of the first stage toward the intermediate packing, thereby causing the rotation near the first stage. This allows the surface of the shaft to be cooled.

Now, to explain in detail the control over the valve 16, as shown in FIG.
4.19, the main steam temperature Ts and the first stage steam temperature Ti are calculated by calculating the variation Δ with respect to time in the computing units 23 and 24.
After being converted into Ts/Δt and ΔTi/Δt, the comparator 25 compares it with a reference value (ΔT/Δt)D.

Compare the larger one of these variations with a standard value determined from the thermal stress of the steam turbine rotating shaft, the life consumption rate (force), and if the variation of (force) is greater than the reference value. ha valve 1
6 is opened, and if both are below the reference value, the valve 16 is closed.

First, the opening/closing control for the flow rate regulating valves 8 and 9 is controlled by a controlled amount! : Humidity is important in obtaining cooling steam.

In this control, as shown in FIG. The leakage steam q from the steam passage after the first stage to the cooling chamber is calculated.

After this, leaked steam q, cooling chamber temperature Tc from thermocouple 11,
Rotation detector 25) Rotation speed N of the steam turbine rotating shaft
From this, the surface heat transfer coefficient of the rotating shaft can be determined, and the required cooling heat amount Q
c is calculated by the calculator 29.

On the other hand, the opening degree of valves 8 and 9 is 11. /2, the steam flow rate G1. G
2 is calculated by the calculator 32.31, and the steam flow rate G0. The sum of G2 is inputted to the calculator 34 along with the temperature Tm inside the steam mixing header 10 and the specific heat α from the thermocouple 12, and is calculated as the amount of steam heat Q' flowing into the steam mixing header 10.
C is required.

The computing unit 30 controls the opening degrees 11 and 12 of the flow rate regulating valve 8.9 so that the steam heat quantity Q'C matches the above-mentioned required cooling heat quantity.

At this time, the opening degree of the valves 8 and 9 is controlled by holding the valve 9 in the main steam system to the minimum opening degree and opening the valve 8 in the primary superheater inlet system to adjust the cooling steam heat quantity Q'c. When the adjustment becomes impossible, the valve 9 is opened within a certain predetermined opening degree, and the cooling steam heat amount Q'C is adjusted by the valve 8.

By repeating this control, the required amount of cooling heat Qc and the amount of cooling steam heat Q'C are made to match.

Control is performed in such a way that steam from the main steam system is kept to a minimum and a reduction in plant efficiency is prevented.

If the cooling steam temperature, that is, the temperature inside the steam mixing header Tm is controlled as described above, the cooling chamber temperature Tc will be approximately constant as shown in FIG. It remains almost constant regardless of load changes, and the life consumption of the high-pressure rotating shaft can be reduced.

As explained in detail above, according to the present invention, at the time of startup, the load change rate and the temperature are controlled, and cooling steam is supplied to the cooling chamber to keep the temperature in the cooling chamber constant. This makes it possible to reduce the life consumption of the rotating shaft.

That is, according to the present invention, the startup time can be shortened and the load change rate can be increased.

[Brief explanation of the drawing]

Figure 1 is a characteristic diagram of each temperature at startup and during load changes, Figure 2 is an explanatory diagram of the magnitude of variation in main steam temperature or high-pressure first stage temperature with respect to time, and Figure 3 4 is a schematic configuration diagram of a high-pressure turbine centered on a cooling chamber to explain the cooling method, and FIGS. 5a and 5b are FIG. 4 is a control system diagram for each of the cooling steam opening/closing valve and the flow rate adjustment valve in FIG. 3; 2...Primary super heater, 6...Moisture separator, 8.9...Flow rate adjustment valve, 10...
・・Steam mixing header, 11.12, 14.19・・・・
...Thermocouple, 13.15... Arithmetic unit, 16...
...Cooling steam on-off valve, 17...High pressure turbine.

Claims (1)

[Claims] 1. Applying cooled and heated steam whose temperature and quantity are controlled to a high-pressure rotating shaft cooling chamber of a steam turbine when the rate of change in main steam humidity or initial stage temperature with respect to time is more than a reference value, A method for cooling a high-pressure turbine rotating shaft, characterized in that the rate of change in the temperature of the cooling chamber over time is made substantially constant. 2. Cooling steam is obtained by mixing main steam and steam from the primary superheater inlet or steam source 1 at a higher pressure and lower temperature than the main steam in a steam mixing header under flow control. A method for cooling a high-pressure turbine rotating shaft according to claim 1. 3. The high-pressure turbine rotating shaft cooling method according to claim 1, wherein the reference value is determined based on the lifetime consumption rate of the high-pressure rotating shaft. 4 The flow rate control of the main steam and the steam from the primary superheater inlet or the steam source at a higher pressure and lower temperature than the main steam is as follows:
Surface heat transfer coefficient of vertical rotating shaft, cooling room humidity and rotation speed,
The required amount of cooling heat determined from the steam temperature after the first stage and the pressure after the first stage, the internal temperature of the steam mixing header, and the amount of steam heat flowing into the header determined from the flow rate of steam flowing into the header via the flow rate control means. 3. The high-pressure turbine rotary shaft cooling method according to claim 2, wherein the cooling method is performed by comparing the amounts of heat and controlling the opening degree of the flow rate control means based on the result of the comparison so that the amounts of heat are equal.