JPS6213739A - Fuel feed device of gas turbine in combined cycle power generating equipment - Google Patents

Abstract

PURPOSE:To smoothly switch fuel gas, by a method wherein a bypass pipe, in which an auxiliary fuel compressor is located, is connected to a fuel feed pipe running from a fuel compressor to a combustor, and stop valves are respectively located in the fuel feed pipe and the bypass pipe. CONSTITUTION:A bypass pipe 39, in which an auxiliary fuel compressor 41 is located, is connected to a fuel feed pipe 27 running from a fuel compressor 29, placed down a line from a low calorie gas feed pipe 19 and a high calorie gas feed pipe 20, to a gas turbine combustor 8. Check valves 35 and 40 are located in the fuel feed pipe 27 and the bypass pipe 39, respectively. The fuel stop valves 44 and 40 are opened and closed depending upon a pressure in the fuel feed pipe 27. This enables fuel to be smoothly switched from high calorie fuel-air mixture to low calorie fuel-air mixture.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a combined cycle power generation facility that combines a gas turbine and a steam turbine that utilizes the exhaust heat of the gas turbine via an exhaust heat recovery boiler. ,especially,
The present invention relates to a gas turbine fuel supply device for supplying gas fuel to a gas turbine.

[Technical background of the invention and its problems]

In recent years, from the perspective of energy conservation, combined cycle power generation equipment that combines a gas turbine, an exhaust heat recovery boiler that generates steam using the exhaust heat of this gas turbine, and a steam turbine that is driven by the steam from this boiler has been developed. has been reviewed and is on the rise in each region. As fuel for the gas turbine in this combined cycle power generation equipment, 1 010·tT 'a @ e (7) ?
Ti 'k f/l= 11 'k 'I! MI-
-Recently, it is common to use gas fuels such as liquefied natural gas and liquefied propane gas.

This power generation method that combines a gas turbine and a steam turbine is often used for in-house power generation, and in the steel industry in particular, this combined cycle power generation equipment is used because gas that is used as fuel for gas turbines is generated in various processes. ing. By the way, the waste gas that is often emitted from blast furnaces during the steel production process in the steel industry has very low calories and has little utility value.On the other hand, in the process of producing coke, which is used as fuel for blast furnaces, hydrogen and methane are High calorie coke gas, which is the main component, can be obtained. Therefore,
These low-calorie gases and high-calorie gases are mixed and used as fuel for gas turbines to generate electricity in order to effectively utilize energy.

First, we will introduce an example of a combined cycle power generation facility that mixes such low calorie gas (hereinafter referred to as BFG fuel) and high calorie gas (hereinafter referred to as COG fuel) as fuel for a gas turbine. This will also be explained.

In FIG. 3, the main shaft 1 includes a steam turbine 2, a power generation I
13, an air compressor 4 and a gas turbine 5 are installed, and the air supplied through the air supply pipe 6 is compressed.
4 and compressed air in the air compressor 14 is introduced via a compressed air conduit 7 into a combustor 8 in which gaseous fuel is combusted.

Furthermore, this combustor 8 is connected to the gas turbine 5 via a gas supply pipe 9, and high temperature gas generated within the combustor 8 is supplied to the gas turbine 5.

The gas turbine 5 is connected to an exhaust heat recovery boiler 11 via an exhaust gas conduit 10, and the high-temperature exhaust gas leaving the gas turbine 5 exchanges heat with water in the exhaust heat recovery boiler 11 before being released into the atmosphere. .

This exhaust heat recovery boiler 11 and the steam turbine 2 are
The exhaust heat recovery boiler 1 is connected by a main steam pipe 12 provided with a steam stop valve 13 and a steam control valve 14.
Steam generated by heat exchange with high-temperature exhaust gas in the steam turbine 1 is supplied to the steam turbine 2 to do work, and then transferred to the condenser 15.
It condenses inside and becomes condensate. Note that since no steam is generated in the exhaust heat recovery boiler 11 at startup, the upper hot air pipe 12 between the steam stop valve 13 and the steam control valve 14 is used to supply steam generated in the steelworks to the steam turbine 2. A steam pipe 16 is connected thereto, and by opening a steam stop valve 17 installed in the steam pipe 16, the steam turbine 2 can be driven by hot air from the steelworks.

At startup, the steam turbine 2 is first driven by the steam from the steam pipe 16, and when steam starts to be generated in the exhaust heat recovery boiler 11, the steam stop valve 17 is closed and the steam from the exhaust heat recovery boiler 11 is driven. The steam turbine 2 is driven.

A fuel supply device 18 that supplies gas fuel to the combustor 8 to drive the gas turbine 5 includes one BFG supply pipe that supplies BFG fuel, which is a low-calorie gas, and one COG supply pipe that supplies COG fuel, which is a high-calorie gas. It has a tube 20. Both supply pipes 19.20 are equipped with flow detectors 21.22 and flow control valves 23.24, respectively.
are interposed, and each flow rate detector 21.22 and flow control valve 23.24 is electrically connected to a regulator 25.26, so that the signal of the gas fuel flow rate detected by the flow rate detector 21.22 is adjusted. regulator 25.26, and this regulator 25.2
The opening degrees of the flow rate control valves 23 and 24 are controlled by control signals from the flow rate control valves 23 and 24. The BFG supply pipe 19 and the COG supply pipe 20 join together to form a fuel supply pipe 27 leading to the combustor 8, and a fixed proportion of the mixed gas fuel can be supplied by adjusting the opening degrees of both flow rate control valves 23 and 24. The fuel is supplied to the combustor 8.

A collector B iso 2B is interposed in the fuel supply @27,
It is designed to remove dust contained in gas fuel. Further, a fuel compressor 29 for compressing gas fuel is installed downstream of this collection TfI 1128, and this fuel compressor 29 is connected to the main shaft 1 via a reduction gear-like mechanism 30, and is connected to the steam turbine 2. The drive compresses the gas fuel and raises the pressure. Furthermore, a fuel stop valve 31 and a fuel control valve 32 are interposed in the fuel supply pipe 27 downstream of the fuel compressor 29, and the fuel control valve 32 supplies gas fuel at the flow rate required for the gas turbine 5. is supplied to the combustor 8. On the other hand, in the fuel supply pipe 27 between the fuel compression 129 and the fuel stop valve 31, surplus gas fuel whose flow rate is controlled by the fuel control valve 32 is returned to the fuel supply pipe 27 upstream from the dust collector 28. A reflux pipe 33 is provided to prevent the fuel compressor 29 from causing problems such as surging. Note that this reflux pipe 33 is provided with a cooler 34 for cooling the gas fuel and a bypass control valve 35.

Therefore, the mixed gas fuel that is a mixture of BFG fuel and COG fuel can be compressed! The pressure is increased by fi29 and the combustor 8
The gas is injected from a nozzle (not shown), combusted, and supplied to the gas turbine 5 as a high-temperature gas. and,
The gas that has done work in the gas turbine 5 is transferred to the exhaust heat recovery boiler 1
1 to heat water, and this steam is supplied to steam turbine 2
They will be supplied to do the work. In this way, the main shaft 1 is rotated by the drive of the steam turbine 2 and the gas turbine 5, and the power generating shaft 3 connected to the main shaft 1 generates electricity. In addition. Air compressor 4 and fuel compressor 29 are also driven by this rotation of main @1.

By the way, in order for the low-calorie mixed gas fuel to be injected through the nozzle in the combustor 8, it must have a pressure that is sufficiently greater than the air pressure discharged from the air compressor 14.

In general, thermal power generation equipment is designed with consideration to the optimal heat balance and various flow balances for normal operation, so the discharge pressure of the fuel compressor 29 is determined by the amount of fuel mixed gas in the combustor 8 during normal operation. For best combustion, air compression I! It is designed to be larger than the discharge pressure of No. 14 by a certain pressure difference.

However, when starting up the gas turbine 5 and igniting the mixed gas fuel, gas fuel with a higher calorie than during normal operation is required. Therefore, it is conceivable to control the mixing ratio of BFG fuel and COG fuel using the flow rate control valve 23 and the flow rate control valve 24 to supply the high-calorie gas fuel required for ignition. However, high-calorie gas fuel generally has a low specific gravity because its main components are hydrogen and methane.On the other hand, the compression ratio of the gas fuel in the fuel compression tii29 is proportional to the specific gravity of the gas fuel, so when the specific gravity becomes small, The pressure increase by the fuel compressor 29 is also reduced compared to the high specific gravity and low calorie gas fuel during normal operation, and the main shaft 1
The problem is that the pressure necessary for nozzle injection of the mixed gas fuel in the combustor 8 cannot be obtained at the nozzle inlet compared to the discharge pressure of the air compressor 4 which is coaxially connected and rotates, and therefore ignition cannot be performed. A point occurs. Therefore, when starting up the gas turbine 5, in the process of operation from ignition to the initial load, in addition to the gas fuel generated in the steelworks mentioned above, the high-power O-ly and combustor 8 necessary for ignition are used. A starting gas fuel, such as liquefied natural gas (LNG) fuel, must be supplied to the combustor 8, having the necessary pressure for injection into the combustor 8. For this reason, it is necessary to separately provide a starting fuel supply pipe 36 shown in FIG. 3, and this starting fuel supply pipe 36 also needs to be provided with a fuel stop valve 37, a fuel control valve 38, and an injection nozzle. Therefore, there is a problem in that a large capital investment must be made for this purpose.

[Purpose of the invention]

The present invention was made in view of the above-mentioned circumstances, and it is possible to use BFG fuel and COG without using starting gas fuel.
It is an object of the present invention to provide a fuel supply device for a gas turbine in a combined cycle power generation facility, which allows the startup and normal operation of the gas turbine to be performed satisfactorily using only fuel.

[Summary of the invention]

The present invention connects a bypass pipe in which an auxiliary fuel compressor is interposed to the fuel supply pipe leading from the fuel compressor to the combustor, and installs a stop valve in each of the fuel supply pipe and the bypass pipe parallel to the bypass pipe. However, the mixture ratio of BFG fuel and COG fuel is changed depending on the operating state of the gas turbine, and during the startup process, a high-calorie mixed gas fuel necessary for ignition is formed, and this high-calorie The pressure of the mixed gas fuel is increased by a steam turbine-driven fuel compressor, and at the same time, the pressure is roughly increased by an auxiliary fuel compressor installed in the bypass pipe, and the mixture is supplied to the combustor at the pressure required for nozzle injection in the combustor. Also, during normal operation, a low-calorie mixed gas fuel that is optimal in terms of fuel efficiency is formed, pressurized only by a steam turbine-driven gas fuel compressor, and supplied to the combustor, as in the past.

[Embodiments of the Invention] The present invention will be described below with reference to embodiments shown in the drawings. Note that the same components as those of the conventional device described above are denoted by the same reference numerals in the drawings, and the explanation thereof will be omitted.

FIG. 1 shows an embodiment of the present invention, in which the mixed gas fuel in the fuel supply pipe 27 is supplied to the fuel supply pipe 27 downstream of the fuel compressor 29 in the fuel supply device 18, and the mixed gas fuel in the fuel supply pipe 27 is supplied upstream of the dust collector 28. Three bypass pipes are branched from the upstream side of the branch point with the reflux pipe 33 that recirculates the fuel to the side, and this bypass pipe 39 further merges with the fuel supply pipe 27 on the downstream side.

A fuel stop valve 40, an auxiliary fuel compressor 41, and a pressure control valve 42 are installed in this bypass pipe 39 from its upstream side to its downstream side, and this auxiliary fuel compressor 41 is driven by an electric IM. It has become. Further, this bypass pipe 39 includes a recirculation pipe 43 for recirculating gas fuel downstream from the auxiliary fuel compressor 41 to the upstream side of the auxiliary fuel compressor 41 to prevent surging of the auxiliary fuel compressor 41. The reflux pipe 43 is provided with a bypass control valve 44 . Furthermore, a fuel stop valve 45 is interposed in the fuel supply pipe 27 between the branch points and the merging points of the bypass pipe 39.

A pressure detector 46 for detecting the pressure of the mixed gas fuel in the fuel supply pipe 27 is connected to the fuel supply pipe 27 downstream from the junction with the bypass pipe 39. is connected to the regulator 47. and,
The regulator 47 outputs a control signal to the pressure control valve 42 of the bypass pipe 39 in accordance with the pressure of the mixed gas fuel in the fuel supply pipe 27 detected by the pressure detector 46. The pressure of the mixed gas fuel in the supply pipe 27 can be controlled to be constant. On the other hand, a fuel supply pipe 2 is also provided at the discharge port of the fuel compressor 29.
A pressure detector 48 that detects the pressure of the mixed gas fuel No. 7 is connected, and the detection signals of this pressure detector 48 and the pressure detector 46 are input to a pressure switch 49 that controls opening and closing of the fuel stop valve 45. It is now possible to do so.

Next, the operation of the above-described embodiment will be explained.

The gas turbine fuel supply device 18 in this embodiment is as follows:
A mixed gas fuel made by mixing BFG fuel and COG fuel generated in a steelworks is supplied.
．． 22 connects the BFG supply pipe 19 and the COG supply pipe 20
The flow rate of BFG fuel and COG fuel in the engine is detected, and each flow rate control valve 23, 24 is controlled by the υI III No. 9 issued from the regulator 25, 26 to change the mixture ratio depending on the operating condition. It has become. That is, when starting up the gas turbine 5, the proportion of COG fuel is increased in order to supply the combustor 8 with the high-calorie mixed gas fuel necessary for ignition, and during normal operation, the proportion of COG fuel is increased, which is optimal for fuel efficiency. The proportion of BFG fuel is controlled to be increased to make it a mixed gas fuel. This mixed gas fuel passes through the dust collector 128 and is boosted in pressure by the fuel compressor 29 which uses the steam turbine 2 as the driving force, but the compression ratio of the mixed gas fuel in this fuel compressor 29 is proportional to the specific gravity of the gas fuel. As mentioned above, the high-calorie mixed gas fuel required at startup has a lower specific gravity than the low-power mixed gas fuel during normal operation, and as a result, the discharge pressure of the fuel compressor 29 increases sufficiently. I will not do it. Therefore, the high-calorie mixed gas fuel cannot be ignited as it is because the pressure necessary for nozzle injection cannot be obtained at the nozzle inlet.

Therefore, the fuel stop valve 45 of the fuel supply pipe 27, which is the mixed gas fuel supply line during normal operation, is fully closed, and the fuel stop valve 40 of the bypass pipe 39 is fully closed.
By further increasing the pressure of the mixed gas fuel pressurized by the auxiliary fuel compressor 41, the pressure nozzle j necessary for nozzle injection in the combustor 8 is obtained at the nozzle inlet. The pressure of the high-calorie mixed gas fuel is detected by a pressure detector 46 connected to the fuel supply@27, and the opening degree of the pressure control valve 42 interposed in the bypass pipe 39 is controlled by a control signal output from the regulator 47. control, and the pressure of the mixed gas fuel is controlled to be constant.

With the high calories necessary for ignition, formed in this way,
Moreover, the mixed gas fuel having the pressure necessary for nozzle injection in the combustor 8 is transferred to the fuel stop valve 31 and the fuel control valve 3.
2 and is injected into the combustor 8 through a nozzle, ignited by the air supplied from the air compressor 4, combusted in the combustor 8 in an optimal state, and turned into a high-temperature gas that is supplied to the gas turbine 5. .

In this way, during the operation process from the ignition at startup of the gas turbine 5 to the first load when it is connected to the power system, high-calorie mixed gas fuel, which is a mixture of BFG fuel and COG fuel generated at the steelworks, is used in the combustor 8. By supplying the gas to the gas turbine, the gas turbine 5 can be operated stably.

Next, during normal operation from initial load to rated operation, the gas turbine 5 is operated with low-calorie mixed gas fuel that is optimal for fuel efficiency. It is necessary to smoothly switch the mixed gas fuel supplied to 8 from a high calorie fuel to a low calorie fuel.

Below, the switching method is shown in Figure 1 and Figure 2 A, B,
This will be explained using C.

The horizontal axis in FIG. 2B shows the time from startup to operation of the gas turbine 5, and the vertical axis shows the calorie and specific gravity of the mixed gas fuel. As shown by the solid line in Fig. 2B, during the startup process from the ignition of the gas turbine 5 to the initial load, high-calorie mixed gas fuel a is supplied, and from the initial load to the rated load operation. During normal operation, a low-calorie mixed gas fuel is supplied. However, in order to switch from a high-calorie mixed gas fuel a to a low-calorie mixed gas fuel, it is necessary to stabilize the initial load. During operation, the flow rates of the BFG fuel shown in broken lines and the COG fuel shown in solid lines in FIG. 2A are changed from a switching start point T to a switching end point T2.
Until then, the BFG flow control valve 23 and the COG flow control valve 24 may be controlled to change the mixing ratio of the BFG fuel and COG fuel. At this time, as shown by the broken line in FIG. 2B, the specific gravity of the mixed gas fuel changes from C, which has a small specific gravity, to d, which has a large specific gravity. When the specific gravity gradually increases during switching of the mixed gas fuel in this way, the compression ratio of the mixed gas fuel in the two fuel compressors also gradually increases because the specific gravity of the gas fuel is proportional to the compression ratio.

Therefore, as shown by the broken line in FIG. 2C, the pressure detector 48
The pressure e of the mixed gas fuel inside the fuel supply pipe 27 detected by is also increased. When the pressure e of this mixed gas fuel increases, the pressure of the mixed gas fuel on the downstream side of the auxiliary fuel compression v441 driven by the electric motor M increases, so the pressure control valve 42 installed in the bypass pipe 39 is opened and closed. The pressure f of the mixed gas fuel in the fuel supply pipe 27 detected by the pressure detector 46 (solid line in FIG. 2C) is controlled to be constant.

By the way, when the pressure e becomes larger than the pressure f of the mixed gas fuel in the fuel supply pipe 27 detected by the pressure detector 46 and a pressure difference ΔP shown in FIG. The pressure ΔP is detected and the fuel supply pipe 2 is
7, the fuel stop valve 45 is fully opened. Thereafter, the electric motor M (+3) and the auxiliary fuel compressor 41 are stopped, and the fuel stop valve 40 is also fully closed to stop the flow of the mixed gas fuel into the bypass pipe 39.

In this way, the switching from the high-calorie mixed gas fuel a to the low-calorie mixed gas fuel is completed, and smooth switching and operation can be performed.

In addition, in the embodiment described above, the auxiliary fuel pressure 1
Although the compressor 41 has been described as being driven by the electric motor M, since steam is available in sufficient quantities in steel works, etc., it is also possible to install a steam turbine in place of the electric motor M in order to utilize energy effectively. It will be done.

[Effects of the Invention] As explained above, the present invention connects a bypass pipe in which an auxiliary fuel 1-mo compressor is interposed to the fuel supply pipe that reaches the combustor from the fuel compressor, and connects the bypass pipe in parallel with this bypass pipe. Since a stop valve is installed in each of the fuel supply pipe and the bypass pipe, the mixing ratio of BFG fuel and COG fuel generated in steel plants etc. can be changed depending on the operating status of the gas turbine, thereby reducing high-calorie and high-pressure fuel during the startup process. It can supply a mixed gas fuel with a high peak, and can supply a low-calorie mixed gas fuel that is optimal for fuel efficiency during normal operation, and can also switch from a high-calorie mixed gas fuel to a low-calorie mixed gas fuel. It can also be done smoothly. As a result, even when starting up a gas turbine, there is no need to receive the high-calorie, high-pressure startup gas fuel needed for ignition, in addition to the gas fuel generated at steel plants, etc., and all operations of the gas turbine are completed. can be made possible using only BFG fuel and COG fuel, and a stable power supply can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a pipe diagram showing an embodiment of the fuel supply system for a gas turbine in a combined cycle power generation facility according to the present invention, and FIGS. 2A, B, and C are graphs showing the operation of the fuel supply system shown in FIG. 1, respectively. , FIG. 3 is a pipe diagram showing a fuel supply device for a gas turbine in a conventional combined cycle power generation facility. 2... Steam turbine, 3... Lightning generator, 4... Air compressor, 5... Gas turbine, 8... Combustor, 11
...Exhaust heat recovery boiler, 15...Condenser, 18...
Fuel supply device, 1...BFG supply pipe, 20...C
OG supply pipe, 29...Fuel compressor, 39...Bypass pipe, 41...Fuel compressor, 42...Pressure control valve,
45...Fuel stop valve, 46...Pressure/force detector, 47
...Adjuster, 48...Pressure detector, 49...Pressure switch. ” 12e%F, 1 (C) Male 2 figure

Claims (1)

[Claims] 1. A gas turbine that uses a mixed gas fuel made by mixing two types of high-calorie and low-calorie gas fuels, which is compressed by a fuel compressor and then combusted in a combustor, and this gas turbine. In a combined cycle power generation facility having an exhaust heat recovery boiler that generates steam using the exhaust heat of the turbine, and a steam turbine that uses the steam from the exhaust heat recovery boiler, the fuel reaches the combustor from the fuel compressor. Connect a bypass pipe equipped with an auxiliary fuel compressor to the supply pipe,
A fuel supply device for a gas turbine in a combined cycle power generation facility, characterized in that a stop valve is provided in each of the fuel supply pipe parallel to the bypass pipe and the bypass pipe. 2. Detecting the pressure of the mixed gas fuel in a fuel supply pipe upstream of the branch point with the bypass pipe and downstream of the fuel compressor, and in a fuel supply pipe downstream of the confluence with the bypass pipe. 2. The fuel supply system for a gas turbine in a combined cycle power generation facility according to claim 1, wherein pressure detectors are connected to each other, and the stop valve is controlled to open and close by signals from both pressure detectors. 3. The bypass pipe is provided with a recirculation pipe that recirculates the mixed gas fuel from the downstream side to the upstream side of the auxiliary fuel compressor, and the recirculation pipe is provided with a bypass control valve. A fuel supply device for a gas turbine in a combined cycle power generation facility according to item 1 or 2. 4. The fuel supply device for a gas turbine in a combined cycle power generation facility according to any one of claims 1 to 3, wherein the auxiliary fuel compressor is driven by an electric motor.