JP2510588B2 - Gas turbine exhaust damper operating method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method of operating a damper installed in an exhaust portion of a gas turbine.

[Conventional technology]

The so-called combined plant, which recovers the exhaust heat of the gas turbine and drives the steam turbine, has a thermal efficiency of 43 to 45.
%, It can be expected to achieve high efficiency in the future, so it is occupying one of the major fields of power generation equipment. The gas turbine currently has a single-unit capacity of 100 MW class, and in order to configure a large power plant, it is unavoidable to arrange a plurality of gas turbines and a steam turbine side by side. Therefore, the gas turbine exhaust has a form in which multiple ducts run side by side and is discharged into the atmosphere from the chimney, but in order to make the plant compact and reduce the equipment cost, multiple ducts are combined and In the large chimney, the method of releasing into the atmosphere is often adopted. An example thereof is shown in FIGS. 3 and 4. Reference numeral 1 is a gas turbine, 2 is equipment such as an exhaust heat recovery boiler, a denitration device, 3 is an exhaust damper, 4 is a chimney, 5 is a gas turbine exhaust duct, and 6 is a collecting duct. Since the exhaust system after the damper 3 is particularly long due to the layout, it is desirable to make the size as small as possible from the viewpoints of compact layout and reduction of equipment cost, but the following problems occur. , Hinders miniaturization.

That is, when the size is reduced, the exhaust pressure loss increases, but as a result, the exhaust pressure in the collecting duct 6 increases, and, for example, if one unit is stopped (the damper 3 is closed), the damper 3 is started. At the same time as opening, the hot exhaust gas will flow back from the exhaust side. The backflow of high-temperature exhaust gas has a risk of seriously damaging the gas turbine due to the following points.

[Problems to be Solved by the Invention]

(1) Due to the reverse inflow of high-temperature exhaust gas, compressors, intake system parts, and other parts that do not plan to flow high-temperature gas may experience troubles such as sliding due to thermal expansion and damage due to high temperatures.

(2) Since the compressor has a very low surge value in the low rotation speed range at startup, there is a risk of surge operation if it is driven with a high back pressure (back pressure). .

For this reason, the exhaust gas duct 6 and subsequent parts should be large ducts with low pressure loss to prevent generation of positive back pressure as much as possible.
Moreover, the fuel stack is also large and long, and is designed to maximize the draft force and to offset the pressure loss generated in the duct section as much as possible.

[Means for solving the problem]

In the gas turbine exhaust damper operating method of the present invention, exhaust gas from a plurality of gas turbines flows through a plurality of exhaust heat recovery boilers, and the exhaust gas is discharged through a collecting duct where these flows are collected, and the exhaust gas The flow is controlled by the first exhaust gas damper installed in the duct on the downstream side of the exhaust heat recovery boiler and the second exhaust gas damper installed in the duct branched from the upstream side of the exhaust heat recovery boiler.

Then, among the plurality of gas turbines, one gas turbine is stopped, another gas turbine is driven, and when the stopped gas turbine is started, the pressure of air discharged from the gas turbine is The first exhaust gas damper of the stopped gas turbine is changed from the closed state to the open state and the second exhaust gas damper of the stopped gas turbine is changed from the open state when the pressure becomes higher than the pressure in the collecting duct. It is characterized by being in a closed state.

[Action]

According to the present invention, a ventilation duct is installed on the upstream side of the exhaust damper 3, and the damper and the exhaust damper 3 are provided inside the ventilation duct.
, And when starting, with the exhaust damper 3 closed and the blow-off damper open, and after the compressor discharge pressure exceeds the back pressure, open the exhaust damper 3 and open the blow-off damper. By closing, the gas turbine can be started and connected to the collecting duct 6 without entering the surge area.
After shutting off the fuel even when stopped, open the blow-off damper and set the exhaust damper 3
Can be safely disconnected from the collecting duct 6 and the gas turbine can be stopped.

Further, in the present invention, the gas released from the blow duct to the atmosphere is only the air discharged from the compressor, and the combustion products are not directly released to the atmosphere, so there is no problem in terms of environmental measures. .

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to FIG.

In FIG. 1, reference numeral 7 denotes an air blowing duct branched from the upstream duct of the exhaust damper 3 to the atmosphere, and 8 denotes an air blowing damper installed in the air blowing duct 7.

The method of operating the exhaust system according to the present invention will be described with reference to FIG.

When the gas turbine is started, the damper 3 is closed and the damper 8 is opened. Basically, the back pressure is 0. Therefore, the gas turbine is started by the power from the starter without any fear of surge. To start. The compressor discharge pressure gradually increases as the engine speed increases, and the exhaust pressure (air) can be discharged to the collecting duct 6 by overcoming the downstream pressure of the damper 3. After being established in this state, the damper 3 is moved while increasing speed or maintaining a certain speed state.
The exhaust (air) is switched so as to flow into the collecting duct 6 by opening and then closing the damper 8. After the switching is completed, the gas turbine is shifted to the ignition condition, and the ignition, the acceleration and the normal starting process are executed.

At the time of stopping, after shutting off the fuel, the damper 8
And then the damper 3 is closed to blow the gas turbine exhaust (air) to the atmosphere, and the gas turbine is stopped with a back pressure of virtually zero.

According to the present invention, starting of a gas turbine when a high back pressure occurs,
Since it is possible to stop and allow positive exhaust pressure to be applied to the exhaust system, it is possible to downsize the exhaust system and greatly contribute to equipment cost reduction.

Further, the air discharge duct according to the present invention is normally used only in the low speed range, and the air flow rate is 5 when the rated operation state is 5
%, It is much smaller than the main exhaust duct, and the increase in equipment cost is significantly smaller than the reduction due to the miniaturization of the exhaust duct.

〔The invention's effect〕

According to the present invention, by appropriately installing a small blower duct system, the exhaust duct and the downstream equipment can be downsized, and the plant space can be reduced and the equipment cost can be reduced. Make a big contribution.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a gas turbine exhaust system diagram of an embodiment of the present invention, FIG. 2 is a start / stop sequence diagram of a gas turbine having an exhaust system according to the present invention, and FIG. FIG. 4 is a system diagram of a collective exhaust gas duct of a plurality of gas turbine facilities, and FIG. 4 is a compressor characteristic diagram in a low rotation range. 1 ... Gas turbine, 2 ... Exhaust heat recovery boiler, denitration device, etc. 3 ... Exhaust gas damper.

Claims (1)

(57) [Claims] 1. Exhaust gas from a plurality of gas turbines flows through a plurality of exhaust heat recovery boilers, and the exhaust gas is discharged through a collecting duct where these flows are collected. In the gas turbine exhaust damper operating method controlled by the first exhaust gas damper installed in the duct on the downstream side of the boiler and the second exhaust gas damper installed in the duct branched from the upstream side of the exhaust heat recovery boiler, When one of the gas turbines is stopped and the other gas turbine is driven to start the stopped gas turbine, the pressure of the air discharged from the gas turbine is When the pressure becomes larger than the pressure, the first exhaust gas damper of the stopped gas turbine is changed from the closed state to the open state, and the first exhaust gas damper of the stopped gas turbine is changed to the second state. Gas turbine exhaust damper operation method which is characterized in that the closed state of the exhaust gas damper from the open state.