JP3497553B2 - Multi-can thermal power plant and operating method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a steam turbine having two or more boilers or an exhaust heat recovery boiler (hereinafter, referred to as a steam turbine).
In a thermal power plant having an HRSG), the pressure loss in the valve is reduced and the boiler / HR is reduced.
The present invention relates to a multi-can thermal power plant that controls the number of operating SGs to improve plant performance.

[0002]

2. Description of the Related Art In a multi-can thermal power plant of this type, it is common to operate multiple cans with the same output sharing during plant partial load operation. The efficiency of the boiler decreases as the load decreases. Therefore, in partial load operation, controlling the number of boilers is effective, and a flow rate adjusting valve may be arranged in series at the reheater inlet or the like. Further, the steam pressure generated in each boiler is always constant, and constant pressure operation in which the partial load operation and the rated load operation have the same pressure is used.

[0003]

However, the flow rate adjusting valve is not necessary during the rated load operation, and pressure loss occurs, which causes deterioration of boiler performance. That is, when the flow rate adjusting valve is installed at the boiler inlet for controlling the number of boilers, there is a problem that the plant performance in the rated load operation is deteriorated even though the plant performance improvement in the partial load operation is achieved.

Therefore, an object of the present invention is to prevent an increase in pressure loss in the boiler water supply system when load sharing is not required among a plurality of boilers or exhaust heat recovery boilers, and It is to provide the driving method.

[0005]

In order to achieve the above object, the present invention (Claim 1) comprises a stop valve installed in a water supply pipe or a reheat steam pipe leading to a superheater or reheater of a boiler, and It is provided with a bypass pipe that connects the water supply pipes between the stop valve and the inlet of the superheater or the reheater, and a flow rate adjusting valve provided in the path of the bypass pipe.

Particularly, in the present invention (claim 2), when the boiler or the exhaust heat recovery boiler is composed of three or more cans, water is supplied to the water supply pipe or the reheat steam pipe from the downstream side of the bypass pipe to the boiler or the exhaust heat recovery boiler. It is desirable to provide a stop valve.

Further, according to the present invention (claim 3), a part of the flow rate adjusting valve is constituted by a stop valve. Furthermore, the present invention (claim 4)
Preferably equip each boiler with a high pressure turbine bypass device and / or a low pressure turbine bypass device.

On the other hand, according to the present invention (Claim 5), when the load sharing of the boiler is changed by using the multi-can thermal power plant according to Claim 1, the stop valve of the boiler for reducing the load is closed and the boiler is closed. The flow control valve of the connected bypass pipe is throttled.

[0009]

In the invention according to claim 1, while the load sharing in the boiler is possible, the feed water does not pass through the flow rate adjusting valve when the load sharing is not required, so that the pressure loss can be reduced and the plant It is possible to improve the performance of. On the other hand, in a plant that employs variable pressure operation, it is possible to suppress throttling loss in the flow rate control valve and reduce pump power.

Further, in the invention according to claim 2, when the boiler or the exhaust heat recovery boiler is composed of three or more cans, all the boilers can arbitrarily share the load, and the minimum necessary flow rate adjusting valve. It becomes possible to aim at simplification of control.

Further, in the invention according to claim 3, a part of the flow rate adjusting valve is constituted by a stop valve, so that the control can be simplified. Further, in the invention according to claim 4, the number of boilers can be easily controlled by providing the turbine bypass device for each boiler.

Further, in the invention according to claim 5, in performing the boiler load sharing control, the stop valve of the boiler for reducing the load is closed and the flow rate adjusting valve related thereto is closed to reduce the load of one of the multiple cans. Only the can can be downloaded and stopped.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, the plant includes two superheaters 1a.
1b and two reheaters 2a and 2b, one high pressure turbine 3 and medium / low pressure turbine 3'are provided, and the superheater 1
a and a bypass pipe 4 connecting the water supply pipes 8 reaching the superheater 1b, a bypass pipe 4'connecting the reheat steam pipes 9 reaching the reheater 2a and the reheater 2b, and the bypass pipes 4 and 4 '. Flow rate adjusting valves 5, 5'provided and bypass pipes 4, 4 '
Stop valves 6a, 6 provided on the water supply pipe 8 on the upstream side of
b, and 6a 'and 6b' provided on the reheat steam pipe 9.

When the two boilers have the same load sharing, the boiler feed water from the boiler feed pump 7 passes from the feed pipe 8 through the stop valves 6a and 6b which are in the open state, and is supplied to the superheaters 1a and 1b at about 1/100% of the total amount. Two flows each. At this time, the flow rate adjusting valve 5 is closed and is not used. However, the two boilers may be opened without avoiding the uneven pressure of some of them.

Similarly, when the two boilers have the same load sharing, the steam leaving the high-pressure turbine 3 passes through the low-temperature reheat steam pipe 9 and the stop valves 6a ', 6b' which are in the open state, and is reheated. About half of the total amount flows into the vessels 2a and 2b. At this time, the flow rate adjusting valve 5'is not used by being closed, but it may be opened so as to avoid uneven pressures of the two boilers.

An operation in which the load sharing of the two boilers is different and one of the boilers (reference A) has a smaller load than the other boiler (reference B) will be described below. After the flow rate adjusting valve 5 is opened, the stop valve 6b is closed. At this time, the load on the boiler B can be reduced by gradually closing the flow rate adjusting valve 5. The flow rate to both boilers A and B is controlled by the power of the boiler feed water pump 7 and the opening degree of the flow rate adjusting valve 5 based on the values detected from the flowmeters 10a and 10b provided at the inlets thereof. Also, the pressure of the steam exiting the boilers A and B is detected by the pressure gauges 11a and 11b, and
The outlet pressures of both boilers A and B are controlled by controlling the amount of fuel input to 12a and 12b. At this time, as shown in FIG. 2, the bypass pipe 4 is connected to the stop valve 6a,
A pipe having a larger diameter than the main pipes 7a, 7b passing through 6b is used, and the flow rate adjusting valve 5 is located almost on the straight line of the steam flow passing through the main pipes 7a, 7b.
b'is connected to the bypass pipe 4 in a substantially vertical direction. As a result, the fluid that goes to the boiler A through the main pipe 7a ',
It is possible to reduce the pressure loss difference between the bypass pipe 4, the flow rate adjusting valve 5, and the fluid going to the main pipe 7b '(which corresponds to the total of the pressure loss of the flow rate adjusting valve 5 and the bypass pipe 4).

As for the reheaters 2a and 2b in the operation in which the load distribution of the boilers A and B is different and the load of the boiler B is smaller than that of the boiler A, the boilers are also passed through the low temperature reheat steam pipe 9 in the same manner as described above. A. B, and the reheat steam pressure is adjusted by the combustors 12a and 12b and the damper.

Also, in the operation of making the burden load of the boiler A smaller than that of the boiler B, the boiler A and the boiler B can be exchanged and the same operation as described above can be performed. Also,
In this embodiment, as shown in FIG. 1, the high-pressure turbine bypass device includes stop valves 13a, 13b, 13a ', 13b', high-pressure turbine bypass valves 14a, 14b, check valves 15a, 15b, 15a ', 15
It may be configured by b '.

In this embodiment, the low pressure turbine bypass device may be composed of stop valves 16a, 16b, 16a ', 16b' and low pressure turbine bypass valves 17a, 17b. Here, the high-pressure turbine bypass operation means that the stop valves 13a ', 13b' are closed and the stop valves 13a ', 13b' are opened, and the steam discharged from the superheaters 1a, 1b is not introduced into the high-pressure turbine 3 but directly. Superheaters 2a, 2
In the low pressure turbine bypass operation, the stop valves 16a 'and 16b' are closed, the stop valves 16a and 16b are opened, and the steam discharged from the reheaters 2a and 2b is discharged to the medium / low pressure turbine 3. It is introduced into a condenser (not shown) instead of being introduced into ′. By these turbine bypass operations, steam generated by the boiler is
It is possible to send the steam from the superheaters 1a and 1b to the reheaters 2a and 2b via the high-pressure turbine bypass device without passing through the bottles 3 and 3'and to the condenser to further condense the steam. That is, the boiler can be operated even after the steam turbine is stopped. This turbine bypass device is used when the steam turbine trips in an emergency, when the exhaust heat recovery boiler is started, or when the generated steam is unstable when it is stopped. As shown in FIG. 1, the boilers A and B are independently provided with a turbine bypass device, so that
Turbine bypass operation can be performed independently on B.

When there are three boilers and one steam turbine (hereinafter referred to as three cans), as shown in FIG. 3, the boilers A, B and C, the bypass pipes 4a and 4b, and the flow rates are set. Regulator valve 5
a, 5b, stop valves 6a, 6b, 6c, and water supply stop valve 18b, and by carrying out the same operation as in the above embodiment, the load sharing of the boilers A, B, C can be set arbitrarily.

Similarly, one 4-can consisting of four boilers is constructed as shown in FIG. 4 and the load sharing of the boilers A, B, C and D can be arbitrarily set. Moreover, the system configuration as shown in FIG. 5 may be applied to one of the three cans. However,
In this case, the load sharing is performed by the same method as described above in the boiler C.
With the same load, the load of the boiler A or B can be reduced by the flow rate adjusting valve 5 and the stop valve 6a or the stop valve 6b. The load sharing of the boiler C can be changed after the boiler A is stopped. When the load of the boiler A is reduced and stopped, the stop valve 6a is closed and the flow rate adjustment valve 5 is closed. At this time, after closing the water supply stop valve 18a, the stop valve 6a and the flow rate adjusting valve 5 are opened, and the stop valve 6b is closed. As a result, the load sharing of the boilers B and C can be set arbitrarily as described above. Further, as shown in FIG. 6, a part of the flow rate adjusting valve can be changed to a stop valve 19.

[0022]

As described above, according to the present invention, it is possible to reduce the pressure loss of the boiler feed water system when the load sharing of the boiler is not required, and it is possible to improve the performance of the plant. It is possible. Further, in a plant that adopts a variable pressure operation, it is possible to suppress throttling loss in the flow rate control valve and reduce pump power.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of a multi-can thermal power plant according to the present invention.

FIG. 2 is an explanatory diagram showing actual pipe dimensions of the bypass pipe and the main pipe shown in FIG.

FIG. 3 is a system diagram showing another embodiment of the present invention.

FIG. 4 is a system diagram showing another embodiment of the present invention.

FIG. 5 is a system diagram showing another embodiment of the present invention.

FIG. 6 is a system diagram showing another embodiment of the present invention.

Front page continued (58) Fields surveyed (Int.Cl. ⁷ , DB name) F22D 5/34-5/36 F22B 33/00 F22D 11/00

Claims (5)

(57) [Claims] 1. In a thermal power plant having a plurality of boilers or an exhaust heat recovery boiler and a steam turbine, a stop installed in a water supply pipe or a reheat steam pipe leading to a superheater or a reheater of the boiler. A multi-can comprising a valve, a bypass pipe connecting the water supply pipes between the stop valve and the inlet of the superheater or the reheater, and a flow rate adjusting valve provided in the path of the bypass pipe. Thermal power plant. 2. When the boiler or the exhaust heat recovery boiler is composed of three or more cans, a water supply stop valve is provided on a water supply pipe or a reheat steam pipe from the downstream side of the bypass pipe to the boiler or the exhaust heat recovery boiler. The multi-can thermal power plant according to claim 1, characterized in that. 3. The multi-can thermal power plant according to claim 1, wherein a part of the flow rate adjusting valve is a stop valve. 4. The multi-can thermal power plant according to claim 1, wherein each boiler is provided with a high-pressure turbine bypass device and / or a low-pressure turbine bypass device. 5. When the boiler load sharing is changed by using the multi-can thermal power plant according to claim 1, the stop valve of the boiler which is going to reduce the load is closed, and the bypass connected to the boiler. A method of operating a multi-can thermal power plant in which the flow control valve of a pipe is throttled.