JPS624541B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine plant, and more particularly to a gas turbine plant that uses a low calorific value gas as a main fuel and uses a high calorific value fuel as an auxiliary fuel.

In recent years, coal liquefaction and gasification have been under development as energy alternatives to oil, and steelworks are considering the effective use of low-calorific value blast furnace gas as an energy-saving measure, and top-pressure gas turbines are already being developed. Gas turbines that use blast furnace gas as fuel, which were popular until about 10 years ago, are now being put into practical use, but people are starting to consider them again.

That is, FIG. 1 is a cycle diagram of a conventional gas turbine plant using gas with a low calorific value.
An air compressor 3 and a gas compressor 4 are connected to the output shaft 2 of the gas turbine 1, and the output shaft 2
A load 5, such as a generator, for example, and a starting device 6 are connected to.

Thus, the air a introduced into the air compressor 3 is compressed by the air compressor 3, and the compressed air is supplied to the combustor 7. Further, the low calorific value gas b is guided to the gas compressor 4 via the mixer 8 and the suction valve 9, and is compressed there.
The combustion gas C is further controlled in flow rate by a control valve 12 and supplied to the combustor 7, where it is combusted together with the compressed air.The combustion gas C, which has become high temperature and high pressure in the combustor 7, flows into the gas turbine 1. , expands in the gas turbine 1 to perform work and load 5
After that, it becomes exhaust gas d and is released into the atmosphere.

The combustor 7 may be used when the calorific value of the low calorific value gas b is extremely low and cannot be ignited when starting the gas turbine, or when the flow rate is insufficient due to the blast furnace or gasifier being stopped or operating at partial load. When the combustion engine is in use, high calorific value fuel e can also be supplied for auxiliary or mixed combustion. That is, the combustor 7 includes a main stop valve 13 and a check valve 1.
4, the high calorific value fuel e whose flow rate is controlled by the control valve 15 is also supplied as required.

Further, the low calorific value gas discharged from the gas compressor 4 has a flow rate f controlled by the control valve 12.
The remaining gas is branched out via the bypass valve 16, and the bypassed low calorific value gas g is cooled in the bypass cooler 17, and mixed with the intake gas b in the mixer 8. The mixture is mixed and guided to the gas compressor 4 again.

By the way, the suction valve 9, bypass valve 16 and control valve 12 for the low calorific value gas, and the control valve 15 for the high calorific value fuel system are controlled by the respective control oils p and i as shown in FIGS. 2 and 3. controlled by.

That is, FIG. 2 is a diagram explaining the operation of each valve in the low calorific value gas system.
The vertical axis shows the opening degree α. Thus, the control valve 12 begins to open at the control oil pressure _p1 and fully opens at the control oil pressure _p3 . Conversely, the bypass valve 16 begins to close at _p1 and is fully closed at control oil pressure _p2 . On the other hand, the suction valve 9 maintains the minimum opening degree until p ₂ and gradually increases the opening degree from p ₂ until it is fully opened at p ₃ .

Further, the control valve 15 of the high calorific value combustion system has a third
As shown in the figure, the pressure of control oil i starts to open at _i1 and fully opens at _i2 .

The above-mentioned control oils p and i are in a ratio to the control oil m, which is controlled by a governor 23 driven by a load setting device 21 and an auxiliary drive gear device 22 from a hydraulic line h through a throttle 20. The set oil pressure signal n is used to distribute the oil in the distributor 24 as shown in FIG. 4, thereby determining the flow rate distribution of the low calorific value gas f and the high calorific value fuel e.

In FIG. 4, the horizontal axis represents the pressure of the ratio setting oil pressure signal n, and the vertical axis represents the pressure of the control oils p and i. Therefore, with respect to the pressure of the ratio setting oil pressure signal n, the pressure of the control oil p in the low calorific value fuel system gradually increases, and the pressure of the control oil i in the high calorific value heating system gradually decreases, so that p + i = m. By the way, the ratio setting oil pressure signal n is controlled by the ratio setting valve 26 from the oil pressure line h through the throttle 25, and the hydraulic system for the control oil m includes a governor 23 because the speed of the gas turbine is low. A starting valve 27 is provided in order to control the control oil m when it is not yet functioning (for example, at startup).

Therefore, when the ratio setting oil pressure signal n is 0%, P=0, i=m, and only the high calorific value fuel is supplied to the combustor 7, resulting in exclusive combustion of the high calorific value fuel.
When n is 100%, i = 0, p = m, and only low calorific value gas is supplied to the combustor 7, resulting in low calorific value gas exclusive combustion operation, and when 0<n<100, mixed combustion operation becomes.

In addition, in the control system of the suction valve 9, main stop valve 10, control valve 12, and bypass valve 16 of the low calorific value gas system, there is also a relief valve 2 for supplying and discharging control hydraulic pressure.
Similarly, the control system for the main stop valve 13 and control valve 15 of the high calorific value fuel system is also provided with a relief valve 29 for supplying and discharging control hydraulic pressure.

Therefore, during exclusive combustion of low calorific value gas, when the relief valve 28 is closed and the relief valve 29 is opened, the hydraulic oil j is established from the hydraulic line h through the throttle 30, the main stop valve 10 is fully opened, and the suction valve is closed. 9, control valve 12
And the bypass valve 16 is brought into a controlled state by the control oil p. On the other hand, the main stop valve 1 of the high calorific value fuel system
3 and control valve 15 are fully closed, and the supply of high calorific value fuel is stopped.

In addition, when burning high calorific value fuel, the relief valve 28
is opened, the relief valve 29 is closed, and the hydraulic oil j becomes 0.
On the other hand, the hydraulic oil k passing through the throttle 31 from the hydraulic line h is established, and the main stop valve 10 and the control valve 12
is fully closed, the suction valve 9 is at its minimum opening, the bypass valve 16 is fully open, and the supply of low calorific value gas to the combustor 7 is stopped, while the main stop valve 13 is fully open and the control valve 1 is fully closed.
5 comes under the control of the control oil i, and high calorific value fuel is supplied to the combustor 7 under the control of the control valve 15.

Further, during mixed combustion, both relief valves 28 and 29 are opened and hydraulic oils j and k are established. Thus, the main stop valves 10 and 13 are fully opened, and each valve in both systems is controlled by the control oils p and i distributed to the control oil m by the ratio setting oil pressure signal n.

By the way, in such a device, if the blast furnace or gasifier fails and the gas turbine plant cannot be stopped, the relief valve 28 of the low calorific value gas system is opened as described above, and the hydraulic oil j is reduced to zero.
It is said that Further, the ratio setting oil pressure signal n also becomes 0%, the control oil becomes p=0, i=m, and high calorific value fuel is exclusively burned.

In addition, since the gas compressor 4 is directly connected to the gas turbine 1 or is driven via a speed reduction device, the gas compressor 4 cannot be stopped and is operated at the minimum load. The gas flow rate is only g, and b and f are 0. That is, the gas is passed through the bypass valve 16 and the bypass cooler 1.
7. The mixer 8 and gas compressor 4 are operated in a circular manner.

Therefore, the minimum power required to drive the gas compressor 4 (40 to 50% of the total load) must be subtracted from the plant output during exclusive combustion operation of high calorific value fuel.
There are problems such as the output being lower than when operating exclusively with low calorific value gas.

Moreover, since the combustion gas passing through the turbine also decreases by the gas amount f, the output of the entire plant further decreases.

In addition, burners are installed in the combustor 7 for low calorific value gas and high calorific value fuel, and as the respective fuels pass through the burners, the fuel acts as a coolant, causing the inside of the combustor to cool. Protected from hot combustion gases.

However, when one fuel is exclusively burned or when the ratio of that fuel is high, the amount of fuel passing through the burner for the other fuel is zero or extremely small, and the burner loses its cooling effect due to the fuel. If the burner is operated for a long time in this state, there is a risk that the burner may burn out due to the high temperature combustion gas. In particular, the combustion gas temperature of high calorific value fuels is about 300 to 500°C higher than that of low calorific value gases, so when high calorific value fuels are exclusively burned or the ratio is high, there is a high possibility that the burner for low calorific value gases will burn out. There are other problems.

In view of these points, the present invention provides a gas turbine plant that effectively cools the other burner and reliably prevents its burnout even when one burner is being burned exclusively or when the ratio of that fuel is high. The purpose is to provide.

An embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

Reference numerals 40 and 41 in the figure are branch conduits that can supply part of the discharged air from the air compressor 3 to the low calorific value gas supply conduit 42 and the high calorific value fuel supply conduit 43 to the combustor 7, respectively. Both branch conduits 40 and 41 are provided with main stop valves 44, 45, check valves 46, 47, and control valves 48, 49, respectively.

The main stop valve 44 is fully opened by a signal from a hydraulic relay 50 that is activated when the pressure of the control oil p in the low calorific value gas system drops below a certain specified value, while the main stop valve 45 has a high calorific value. It is designed to be fully opened by a signal from a hydraulic relay 51 which is activated when the pressure of control oil i in the fuel system drops below a certain specified value.

Further, the opening degrees of the control valves 48 and 49 are controlled by output signals from the computing unit 52, respectively.
The arithmetic unit 52 includes a hydraulic signal from a hydraulic relay 53 that detects the hydraulic pressure of the control oil m, and a hydraulic signal from the gas turbine 1.
A temperature signal from a temperature relay 54 that detects the temperature of exhaust gas from the air compressor 3 and an air pressure signal from a pneumatic relay 55 that detects the air pressure discharged from the air compressor 3 are applied, and furthermore, the arithmetic unit 52
An output signal from a switching device 56 that detects the fuel system being used based on signals from hydraulic relays 50 and 51 is input to the switch. Therefore, in the computing unit 52, the load of the relevant operation is calculated based on the signal of the control oil m, and the inlet temperature of the turbine is calculated based on the signals from the hydraulic relay 53 and the hydraulic relay 54.
A control signal suitable for the operation is sent to the control valve 4 in response to a signal from the control valve 6, corresponding to the fuel system being used.
8 or 49.

When the pressure of the control oil p in the low calorific value gas system drops below a certain specified value, the hydraulic relay 50 is activated and the main stop valve 44 is fully opened. It will be done. On the other hand, the switching device 56 is actuated by the output signal from the hydraulic relay 50, whereby a control signal corresponding to the combustion operation of the high calorific value fuel is sent to the control valve 48, and the opening degree of the control valve 48 is changed. controlled. Therefore, part of the air discharged from the air compressor 3 is transferred to the branch conduit 40.
The gas flows into the low calorific value gas system while being controlled by the control valve 48, and is supplied from the burner to the combustor 7. The burner is therefore cooled down.

Similarly, when the pressure of the control oil i in the high calorific value fuel system drops below a certain specified value, the main stop valve 45 is fully opened by the operation of the hydraulic relay 51, and the discharge from the air compressor 3 is stopped. A portion of the air flows into the high calorific value fuel system to cool the burner.

In addition, in the above embodiment, the air discharged from the air compressor was used as the coolant, but the sixth embodiment
As shown in the figure, for example, a supply conduit such as steam or water may be connected to the low calorific value gas supply conduit 42 and the high calorific value fuel supply conduit 43 to supply steam, water or the like as a coolant.

In this case, it is particularly effective when high calorific value fuel is exclusively burned or the ratio thereof is high. In other words, due to the characteristics of this gas turbine plant during the operation, the flow rate of combustion gas passing through the turbine 1 decreases, and if an attempt is made to operate the turbine 1 at an inlet or outlet temperature within a certain specified value, the air compressor 3's temperature decreases. The discharge pressure is lower than when operating exclusively with low calorific value gas or when the ratio thereof is high. As a result, although the required power of the air compressor 3 is reduced, the reduction in the output of the turbine 1 is more affected, and the overall plant output is reduced. In this case, the operating point of the air compressor 3 moves to a point farther away from the surging limit than when operating exclusively with low calorific value gas or when its ratio is high. In addition, the combustion temperature when high calorific value fuel is exclusively fired or its ratio is high is 300 to 500% higher than when low calorific value gas is exclusively fired or its ratio is high.
℃, the amount of nitrogen oxide NOx generated increases, and the furnace wall temperature also increases.

If steam or water is used as a coolant during this type of operation, the air compressor has a margin of surging limit, so it will be necessary to use more coolant than when operating exclusively with low calorific value gas or with a high ratio. can be mixed in. Therefore, the output of the turbine 1 increases by the amount of steam or water mixed in, and the plant output also increases. Furthermore, the combustion temperature is lowered, nitrogen oxides are reduced, and the furnace wall temperature is also lowered, so the effects are synergistically improved.

As explained above, in the present invention, in a gas turbine plant using low calorific value gas and high calorific value fuel, when one fuel is exclusively fired or the ratio thereof is high, compressed air etc. are used in the burner of the other fuel. As a result, the burner can be cooled and the burner can be prevented from burning out due to high temperature combustion gas
The plant can continue to operate safely. In addition, when steam, water, etc. are used as a coolant, it is possible to increase the turbine output and, in turn, increase the plant output, especially when high calorific value fuel is exclusively burned or its ratio is high. This has the effect of reducing the temperature of the wall surface of the combustor furnace and extending its life.

[Brief explanation of the drawing]

Figure 1 is a schematic system diagram of a conventional gas turbine plant using low calorific value gas, Figure 2 is an explanatory diagram of the operation of each valve in the low calorific value gas system, and Figure 3 is a diagram of the control valve for high calorific value fuel. FIG. 4 is an explanatory diagram of the operation of the distributor, and FIGS. 5 and 6 are schematic system diagrams of an embodiment of the gas turbine plant of the present invention. 1...Gas turbine, 3...Air compressor, 4...
... Gas compressor, 7 ... Combustor, 40, 41 ... Branch conduit, 44, 45 ... Main stop valve, 48, 49 ... Control valve, 52 ... Arithmetic unit, 56 ... Switch.

Claims (1)

[Scope of Claims] 1. In a gas turbine plant having a combustor provided with burners for low calorific value gas and high calorific value fuel, cooling that selectively supplies a coolant to the fuel supply pipes of both burners. By connecting the refrigerant supply pipe, the refrigerant can be supplied to the burner for the other fuel when only one of the fuels is burning exclusively or when the proportion of that fuel is high. A gas turbine plant characterized in that a coolant is supplied to one fuel burner during exclusive combustion or during a combustion state in which the ratio of fuel is high. 2. Gas turbine plant according to claim 1, characterized in that the coolant is part of the discharge air of the air compressor. 3. Gas turbine plan according to claim 1, characterized in that the coolant is steam or water.