JPS59510A - Combined cycle electric generation plant - Google Patents

Abstract

PURPOSE:To reduce the time required for the starting or the load rising operation of the titled plant by a method wherein the combustion gas extracted from the intermediate stage of a gas turbine is introduced to a waste heat recovery boiler by a waste gas bypass device, the waste heat recovery boiler is rapidly warmed up at the starting or the load rising operation. CONSTITUTION:At the warming up operation, the combustion gas is extracted from the intermediate stage of a gas turbine 11 by opening a flow rate regulating valve 29, said extracted gas is mixed into the waste gas inside of a duct 19. Thereby, the output power of the gas turbine 11 is decreased, and number of axis revolutions is also decreased, the amount of fuel supplying can be increased in proportional to the amount of decreased output power by opening a fuel control valve 18. Because of the extracted waste gas containes more energy than the waste gas flowing through inside of the duct 19, the waste gas mixed with the combustion gas containes more enthalpy than before mixing, accordingly, the warming up time can be shortened by increasing the quantity of heat of the waste gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a combined cycle power plant in which an exhaust gas bypass device is provided between a gas turbine and an exhaust heat recovery boiler.

[Technical background of the invention and its problems]

A gas turbine, generator, and steam turbine are arranged on a single shaft, and this is combined with an exhaust heat recovery boiler to form a combined cycle power generation plant, which is operated as a plant that can handle power system peak loads and middle loads. has been done. Therefore, compared to large thermal power plants for base load, this expanding plant requires more stops and starts.
There is a strong demand for shortening startup time. Startup of a combined cycle power plant (2) Especially in the case of a cold start; 1. Warming up of the exhaust heat recovery boiler; 2. It takes a lot of time. For example, in the case of a 140,000 KW class single-shaft combined cycle power plant , it takes about 140 minutes from startup to rated load state with a cold start, and within that time (
1 It takes about 70 minutes to warm up the exhaust heat recovery boiler, which is half of the total startup time.

Generally, at startup, in order to quickly warm up the exhaust heat recovery boiler 2, it is sufficient to warm up the exhaust heat recovery boiler 2 by heating the exhaust gas of the gas turbine. The more fuel you put in, the better. However, if you put in a lot of fuel, the shaft rotation speed will increase. Therefore, at startup, it is necessary to reduce the fuel flow rate and warm up the exhaust heat recovery boiler over a long period of time. Also, when the load increases, gas turbines can increase the load rapidly, but steam turbines cannot increase the load rapidly.This is because gas turbines rapidly increase output as the amount of fuel input increases. Although the load on the steam turbine increases, even if the exhaust gas temperature of the gas turbine increases,
This is because the amount of steam generated in the exhaust heat recovery boiler does not increase rapidly, so the load increase is delayed. Therefore, it can be said that the load increase of the entire combined cycle is delayed.

[Purpose of the invention]

An object of the present invention is to provide a combined cycle power generation plant that can quickly warm up an exhaust heat recovery boiler at startup and when the load increases to shorten the time required for startup and the time required for load increase.

[Summary of the invention]

The present invention provides an exhaust gas bypass device that guides the combustion gas extracted from the middle stage of the gas turbine to the exhaust heat recovery boiler, so that the exhaust heat recovery boiler can be quickly warmed up at startup and when the load increases. This is related to the Exploration Plant.

[Embodiments of the invention]

The present invention will be described below using two embodiments shown in FIG.

In FIG. 1, a combined cycle power plant 10 according to the present invention is constructed by arranging a gas turbine 11[deg.] 2 and a natural gas turbine 13 on one axis, and combining them with an exhaust heat recovery boiler 14. The gas turbine 11 is equipped with an air compressor 15 and a combustor 17, and the fuel led from the pipe 16 to the combustor 17 via the fuel control valve 18 becomes combustion gas, and the gas turbine 11 (
= Work while being guided. Exhaust gas discharged from the gas turbine 11 is led to the exhaust heat recovery boiler 14 via the duct 19, and after exchanging heat with the heater, evaporator 21, and economizer 22 inside the boiler, it is released into the atmosphere. released.

The exhaust heat recovery boiler 1442 is equipped with a drum, and the heated steam generated in the heater by the boiler function including the drum is guided to the steam turbine 13 through the steam pipe to drive it. do. The steam discharged from the steam turbine 13 is led to a bale water tank 254 (254) to be converted into water, and is then led to the economizer 22 (2) of the exhaust heat recovery boiler 14 (254). An exhaust gas bypass device 27 is provided to extract combustion gas from the gas turbine 11 and guide it to the exhaust heat recovery boiler 14 by bypassing the duct 19.This exhaust gas bypass device !27 extracts combustion gas from an intermediate stage of the gas turbine 11. It has an air bleed line, and this air bleed line is communicated with the exhaust heat recovery boiler 140 inlet via a flow rate regulating valve 29 so as to form a bypass path for the duct 19.

Next, a method for starting the combined cycle power plant of the present invention will be explained using FIG. In FIG. 2, the solid line L2 indicates the fuel flow rate, the dotted line L2 indicates the rotational speed, and the dotted line L1 indicates the combustion gas bleed flow rate. Time A after startup
As time passes, the rotational speed increases, and when it increases to b, fuel 62 is ignited. Immediately thereafter, the opening degree of the fuel control valve 18 is kept constant, the fuel flow rate L1 is kept constant at a, and the opening degree of the flow rate adjustment valve 290 is controlled to suppress the rotation speed L2 to C. is set to a constant value e and the warm-up operation begins. When time B has elapsed and the warm-up is sufficient, the flow rate adjustment valve 29 is closed, the shaft rotation speed L2 is increased, and then accelerated operation (two means shaft rotation speed (two responsive fuel control valve 18
opens and accelerates the rotational speed to the rated rotational speed d.

During this start-up process (2), combustion gas is extracted from the middle stage of the gas turbine 11 by the extraction flow rate e during warm-up. The output of the engine decreases, and the shaft rotational speed decreases.To compensate for this, a large amount of fuel a' is injected to supplement the extracted combustion gas to maintain the shaft rotation 15c. This fuel flow i a' is the combustion gas extraction flow rate e
and the set shaft rotation speed C. Further, the warm-up times A to B can be shortened accordingly if the amount of fuel input a is large.

In addition, the operation of the power generation plant of the present invention is explained by the system shown in Fig. 1 (
- To begin with, at startup, during warm-up operation of the exhaust heat recovery boiler 14 after fuel ignition, the generator 1
2 is not connected to the system, and when the fuel control valve 18 is opened to increase the amount of fuel input, the output of the gas turbine 11 increases and the shaft rotation speed increases. If the shaft rotation speed increases during startup, disadvantages such as heating the inside of the steam turbine 13 will occur, so the shaft rotation speed must be kept low. However, in order to shorten the startup time, it is necessary to shorten the warm-up time by increasing the amount of heat of the exhaust gas supplied to the exhaust heat recovery boiler 141. To achieve this, it is necessary to increase the amount of fuel input by increasing the opening degree of the fuel control valve 18, thereby increasing the amount of heat that the exhaust gas of the gas turbine 11 has.

Therefore, in order to solve this contradiction, during warm-up operation (opening the two-flow regulating valve 29, the combustion gas is evacuated from the middle stage of the gas turbine 11, and the combustion gas is mixed with the exhaust gas (two) in the duct 19). Do this.
1 output decreases and the shaft rotation speed becomes low. Therefore, the amount of fuel input can be increased by opening the fuel control valve 18 by the amount of decrease in the output of the gas turbine 11. In addition, the combustion gas extracted from the middle stage of the gas turbine 11 is transferred to the duct 19.
Because the exhaust gas flowing inside has a lot of energy, the exhaust gas mixed with combustion gas flowing inside the bleed pipe has a higher enthalpy than the conventional case before mixing, and the calorific value of the exhaust gas is also increased. By increasing it, the warm-up time can be shortened.

Also, when the load increases, the gas turbine 11 can increase the load rapidly (2), but the steam turbine 13 takes time. do it.

After receiving a load increase command, the fuel control valve 18 is opened to increase the fuel flow rate, and at the same time, the flow rate adjustment valve 29 is opened to bleed combustion gas from an intermediate stage of the gas turbine 11. Because of this (2), the gas turbine 11 can bear a load without increasing its output.Also, the extracted combustion gas is guided to the duct 1 and mixed into the exhaust gas. By supplying exhaust gas with a high calorific value to the recovery boiler 14, steam can be started up quickly, the load rise time of the steam turbine 13 can be shortened, and as a result, the load on the ζNikon combined cycle power plant can be reduced. It can speed up the rise.

Figure 3 shows the starting method shown in Figure 2 (nilling), further increasing the combustion gas extraction amount e' during warm-up operation, and further increasing the fuel flow rate (1).
This shows that the shaft rotational speed can be increased to the rated rotational speed by performing an accelerated operation of the warm-up operation using the flow rate regulating valve array. That is, the fuel is ignited when time A has elapsed after startup.

Thereafter, the opening of the fuel control valve 18 and the flow rate adjustment external measurement are made constant, and the fuel flow rate is kept constant at the value a', and the combustion scum oil amount e' is controlled so as to keep the shaft rotation speed at C. Warm-up operation (two people). After time B (two people have passed), when warm-up has been sufficiently performed and the steam pressure inside the drum has increased, throttle the flow control valve 29 and start accelerated operation (-). At this time, the opening degree of the υ flow control IA external measurement is controlled according to the shaft rotation speed, and the shaft rotation speed is accelerated to the rated rotation speed d and synchronized. 29 is closed and the fuel is increased to take the load.

In this embodiment, after the ignition starts, the opening degree of the fuel control valve 18 is kept constant and the fuel flow rate a is constant until the time when the load is started, and the flow rate adjustment external measurement is restricted to υ and the combustion gas extraction amount. (2) increase the shaft rotation speed, and at the time of synchronization (-, the flow rate adjustment valve 29 controls the shaft rotation speed 1-
I try to do that. As a result, the fuel flow rate is kept constant during acceleration and rise, and during synchronization, so that the flame within the gas turbine combustor 17 is stabilized. As a result, this can improve the reliability of the gas turbine 11 at the time of startup (second stage), and since the fuel does not increase rapidly, it reduces the amount of NOX I-carbon oxides and unburned gas generated at startup. To suppress the generation of harmful combustion products such as hydrocarbons to a low value (Second).

〔Effect of the invention〕

As described above, according to the present invention, the combustion gas extracted from the middle stage of the gas turbine is configured to be mixed into the exhaust heat recovery boiler via the flow rate regulating valve, and thereby the combustion gas is supplied to the exhaust heat recovery boiler. It is possible to increase the amount of heat contained in the exhaust gas and shorten the plant start-up time and load rise time.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the combined cycle power plant of the present invention, and FIGS. 2 and 3 are curve diagrams for explaining a method of starting up the power plant of the present invention. 10... Combined cycle power generation plant, ]1.
... Cast turbine, 12... Generator, 13... Steam turbine, 14... Exhaust heat recovery boiler, J5... Air compressor, 16... Piping, 17... Combustor,
18...Fuel control valve 19...Exhaust duct,
27...Exhaust gas bypass device, ah...bleeding pipe, 29...bleeding flow rate - valve regulation. (8733) Agent Patent attorney Yoshiaki Inomata (and 1 other person) Figure 1 Figure 2 Figure 3

Claims (3)

[Claims] (1) In a combined cycle system consisting of a combination of a gas turbine, a generator, a steam turbine, and an exhaust heat recovery boiler, combustion extracted from an intermediate stage of the gas turbine is connected to an exhaust gas duct from the gas turbine to the exhaust heat recovery boiler. II! An exhaust gas bypass device that mixes gas through a flow rate adjustment valve is installed! , a combined cycle power plant with characteristics. (2) The combined cycle power generation plant according to claim 1, wherein the flow rate regulating valve is opened during warm-up operation to mix the extracted combustion gas from the exhaust gas bypass device. (3) The combined cycle power plant according to claim 2, wherein the extracted combustion gas is mixed in from the exhaust gas bypass device by adjusting the flow rate of the flow rate regulating valve during acceleration operation.