JP2585328B2 - Operating method of combined plant and apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a plurality of gas turbines and a gas turbine driven by steam generated using exhaust gas of the gas turbine as a heat source.
TECHNICAL FIELD The present invention relates to an operation method and an operation device of a combined plant provided with two steam turbines.

[Conventional technology]

Conventionally, in general, in a steam turbine of a multi-shaft combined plant, the pre-pressure control is performed by squeezing a steam turbine control valve at a partial load, and a decrease in plant efficiency at a partial load has been observed.

In particular, when switching the number of gas turbines, when the number of operating gas turbines is small, the amount of evaporation of the exhaust heat recovery boiler is small. Regarding this kind of technology, Section V “Total Control” of the introductory course on thermal and nuclear power “combined power generation” is known.

[Problems to be solved by the invention]

The multi-shaft combined plant is composed of multiple gas turbines, the same number of exhaust heat recovery boilers and one steam turbine. In base load operation, all gas turbines are operated and all exhaust heat recovery is performed. Steam generated by the boiler is introduced into a steam turbine.

Here, in the partial load operation of the multi-shaft combined, the gas turbine number switching operation is generally adopted rather than the gas turbine equal partial load operation in view of the gas turbine efficiency and the steam cycle efficiency related to the gas turbine exhaust gas temperature. It is.

That is, for example, in a combined plant including two gas turbines and one steam turbine, the operation (a) in which one gas turbine is stopped (the gas turbine number switching operation) is performed while (b) the gas turbine Priority is given to operation with two units at 50% load (gas turbine equal load operation).

In this case, since the number of gas turbines is reduced from two to one, only one exhaust heat recovery boiler is generating steam. This means that the steam flow into the steam turbine is 1/2 of the rated value, so the steam pressure is also 1/2.

In other words, the operating waste heat recovery boiler
100% flow rate and steam pressure are 50% pressure, so the amount of evaporation of the exhaust heat recovery boiler or the flow rate in the main steam pipe is almost double (the steam pressure is halved, so the steam specific volume is about twice) Become.)
Then, there was a fear that piping erosion might occur.

On the other hand, to prevent such inconveniences, the steam turbine control valve is throttled to secure steam pressure.However, the number of steam turbine control valves is set irrespective of the number of gas turbines. Therefore, the number is generally determined based on the size of the control valve and constraints on the arrangement, and is set to be smaller than the number of gas turbines.

In this way, when a smaller number of control valves than the number of installed gas turbines is provided, the steam turbine control valve throttle operation is performed during the partial load operation of the plant, so that the control valve throttle loss increases and the internal efficiency of the steam turbine increases. There was a problem that the plant efficiency also decreased with the decrease.

An object of the present invention, in view of the above-described problems of the related art, is to prevent a decrease in steam pressure during a partial load operation of a plant, and to prevent a pipe erosion or the like from occurring,
Another object of the present invention is to provide a combined plant operating method that reduces the throttle loss of a steam turbine control valve and prevents a decrease in plant efficiency. To provide.

[Means for solving the problem]

In order to improve the plant efficiency under partial load of a multi-shaft combined plant, it is important to reduce the throttle loss of the steam turbine control valve. In consideration of the fact that the number of steam turbine control valves is adjusted, the number of steam turbine control valves is adjusted to the number of gas turbines, and the number of steam turbine control valves corresponding to the number of operating gas turbines is operated.

That is, in the present invention, the steam turbine is provided in advance with N number of control valves having the same number as the number of gas turbines, and these are set to N when operating n gas turbines among the gas turbines. The n control valves are fully opened and the remaining control valves are fully closed.

[Action]

When the multi-shaft combined plant performs the gas turbine number switching operation during the partial load operation, as described above, the same number of steam turbine control valves as the number of gas turbines are provided, and the number of steam turbine control valves equal to the number of operating gas turbines is provided. Since the operation is fully opened, a decrease in steam pressure can be prevented, and the occurrence of erosion or a vibrator due to a high flow rate in an evaporator or a steam pipe caused by a decrease in steam pressure as in the prior art can be prevented. Moreover, it is not necessary to throttle the control valve, and it is possible to reduce an increase in the control valve throttle loss.

Therefore, the plant efficiency during the partial load operation can be kept high.

[Embodiment] Fig. 1 is a system diagram of an embodiment of an operating device according to the present invention configured to carry out an operating method according to the present invention.

In this example, two gas turbines 1a and 1b are provided, and drive the generators 4a and 4b, respectively. Two exhaust heat recovery boilers 2a and 2b using the high temperature exhaust gases 5a and 5b of the respective gas turbines 1a and 1b as heat sources are provided.

The steam pipes 6a, 6a, of the two waste heat recovery boilers 2a, 2b, respectively.
The high-temperature and high-pressure steam generated in 6b merges in the main steam pipe 7.

The combined steam is supplied to two control valves 8a, 8 provided in parallel.
Via b, it is supplied to the steam turbine 3 as working steam, and the steam turbine 3 drives the generator 4c. 9 is a condenser and 10 is a condensate pump.

In this embodiment, the number of installed gas turbines is two,
The number of setting valves is also two. When implementing the present invention, if N gas turbines (N is an integer of 2 or more),
The number of setting valves is also N.

FIG. 2 is an explanatory diagram in which the opening and closing operation of the control valve in the present embodiment is drawn by a solid line, and the opening and closing operation of the control valve in the conventional example is drawn by a broken line.

In this embodiment, two control valves 8a and 8b are provided as described with reference to FIG. 1, but only one control valve is provided in the conventional example (broken line).

When one gas turbine is operated, the conventional example
Each of the control valves was set to an intermediate opening (point A in the figure). In this example, one of the two control valves 8a is fully opened (point B in the drawing). Therefore, in this embodiment, when one gas turbine is operated, one control valve 8a is fully opened, and the other control valve 8b is fully closed.

Start the second gas turbine at point C shown in the figure,
In the case of increasing the output so as to achieve the rated operation at the point D shown in the figure, in the conventional example (broken line), the opening of one control valve, which was set to the intermediate opening (A), is increased as shown by the arrow E. Go on.

In the present example, another control valve 8b starts to be opened at the point C, and the opening is increased as indicated by an arrow F.

When the two gas turbines are performing rated operation, in both the conventional example and the embodiment, all valves are fully opened as shown at point G in the drawing.

FIG. 3 is a table showing the main steam pressure in the above-mentioned operation. As understood from FIG. 3, when the control valve is gradually opened in accordance with the output rise of the second gas turbine in FIG. 2, the control valve is opened so that the main steam pressure is kept constant (rated pressure). Control the degree. Therefore, in this embodiment, when the control valve 8a is fully opened, another control valve 8b is gradually opened and fully opened in accordance with the operation of the second gas turbine.

FIG. 4 shows a change in the internal efficiency of the steam turbine due to the above-mentioned operation. The solid line represents the embodiment, and the broken line represents the conventional example.

The hatched portions indicate the improvement of the internal efficiency by applying the present invention.

〔The invention's effect〕

According to the operation method of the present invention, it is possible to improve plant efficiency at the time of partial load in a combined plant. For example, at 50% load, the gas turbine 1
According to the present invention, the steam control valve is fully opened while the steam turbine control valve is throttled in the prior art when the table is operated. Therefore, the internal efficiency of the steam turbine is expected to be improved by 2 to 3%.

Assuming that the output ratio between the gas turbine and the steam turbine in the combined plant is 2: 1, the effect of the improvement in the internal efficiency of the steam turbine on the improvement of the whole plant is (2-3) × 1/3 = 0.7. １1% equivalent.
Further, according to the operating device of the present invention, at the time of partial load, the same number of steam turbine control valves as the operating gas turbine are fully opened, so that the above-described operating method can be accurately performed.

[Brief description of the drawings]

FIG. 1 is a system diagram of a combined plant provided with one embodiment of an operating device according to the present invention. FIGS. 2 to 4 are tables comparing the embodiment of the method of the present invention with the conventional example, and the horizontal axis indicates the number of operating gas turbines in common. FIG. 2 is a table in which the vertical axis indicates the degree of opening and closing of the control valve, FIG. 3 indicates the main steam pressure on the vertical axis, and FIG. 4 indicates the internal efficiency of the steam turbine on the vertical axis. 1a, 1b: gas turbine, 2a, 2b: waste heat recovery boiler, 3
... steam turbine, 4a, 4b, 4c ... generator, 7 ... main steam pipe, 8a, 8b ... steam turbine control valve.

Claims (4)

(57) [Claims] An exhaust heat recovery boiler having N gas turbines, N exhaust heat recovery boilers using exhaust gas from each of the N gas turbines as heat sources, and a heating valve, wherein the N exhaust heat recovery boilers are provided. In a multi-shaft combined plant provided with one steam turbine that uses generated steam as working steam,
The steam turbine is provided with N number of control valves having the same number as the number of gas turbines, and when the number of the N gas turbines is n, the number of the N control valves is n. , And the remaining control valve is fully closed. Here, N is an integer of 2 or more, and n is an integer of 1 or more. 2. When the operation of switching from n gas turbines out of the N gas turbines to N gas turbines is performed, n of the N control valves are fully opened and the remaining control valves are operated. 2. The operating method for a combined plant according to claim 1, wherein the remaining control valve is gradually opened from the fully closed operation state. 3. An N exhaust gas recovery boiler having N gas turbines, N exhaust heat recovery boilers using exhaust gas from each of the N gas turbines as heat sources, and a heating valve. In a multi-shaft combined plant provided with one steam turbine that uses generated steam as working steam,
A main steam pipe for joining working steam from the non-heat recovery boilers is connected, and working steam from the main steam pipe can be supplied to the steam turbine between the main steam pipe and one steam turbine. N
Are provided in parallel, and when n gas turbines out of N gas turbines are operated, n of the N control valves are fully opened and the remaining control valves are fully closed. An operating device for a combined plant, comprising: an adjusting valve control unit that performs the control. 4. The controller according to claim 1, wherein the controller controls the number of the N gas turbines when switching from the operation of the n gas turbines to the operation of the N gas turbines.
From the state of the fully open operation of the individual and the fully closed operation of the remaining control valve,
The operating device for a combined plant according to claim 3, wherein the remaining control valve is gradually opened.