Power plant with emergency fuel system

Abstract

A method for operating a power plant having a gas turbine and an emergency fuel system where in a normal operating state, gas is supplied from a supply line to the combustion process of the gas turbine, and in addition gas is supplied from the supply line to a gas liquefaction plant where it is liquefied, forming a liquid gas which is stored in a liquid gas store. In special operating state, liquefied gas is drawn from the liquid gas store and is evaporated in an evaporator, and is fed in the gaseous state into the combustion process of the gas turbine.

Claims

1. A method for operating a power plant comprising a gas turbine and an emergency fuel system, the method comprising: receiving into a supply line a supply gas from an external source, wherein the supply line is connected to a combustion process of the gas turbine, and wherein the supply line comprises a liquefaction process outlet, a liquefaction line connected to a gas liquefaction plant and comprising a liquefaction line inlet connected to the liquefaction process outlet, in a first operating state, feeding the supply gas from the supply line to the combustion process of the gas turbine, and, in addition, feeding the supply gas from the liquefaction process outlet to the liquefaction line to supply the gas liquefaction plant and liquefying the supply gas therein, wherein a composition of the supply gas is not changed, wherein a liquefied gas is formed and stored in a liquefied gas tank, in a second operating state, extracting the liquefied gas from the liquefied gas tank, and evaporating the liquefied gas in an evaporator to form an evaporated gas, and feeding the evaporated gas into the combustion process of the gas turbine, and in the second operating state, feeding the evaporated gas from the liquefied gas tank back into the supply line in order to compensate for pressure fluctuations in the supply line or, in the event of a complete loss of supply gas, to supply other consumers which are connected to the supply line with the evaporated gas.

2. The method as claimed in claim 1, wherein, in the gas liquefaction plant, less than 5% of electric power of the power plant is used for liquefaction of the supply gas.

3. The method as claimed in claim 1, wherein, in the second operating state, cold energy which becomes free during evaporation in the evaporator is used for cooling intake air of the gas turbine.

4. The method as claimed in claim 1, wherein the gas liquefaction plant is additionally used in the first operating state in order to utilize power control of the power plant by controlled start-up or shutdown of said gas liquefaction plant.

5. The method as claimed in claim 4, wherein the gas liquefaction plant is additionally used in the first operating state for frequency control or frequency back-up.

6. The method as claimed in claim 1, wherein the supply gas fed to the combustion process of the gas turbine comprises liquefied natural gas, and the supply gas fed to the gas liquefaction plant comprises the liquefied natural gas.

7. The method as claimed in claim 1, wherein the supply gas from the external source, the supply gas fed to the combustion process of the gas turbine, and the supply gas fed to the gas liquefaction plant comprise liquefied natural gas.

8. A method for operating a power plant comprising a gas turbine and an emergency fuel system, the method comprising: feeding supply gas from an external source to a combustion process of the gas turbine in a first operating state, feeding a flow of the supply gas from the external source to a gas liquefaction plant without changing a composition of the flow of the supply gas therebetween, liquefying the supply gas in the gas liquefaction plant to form a liquefied gas, and storing the liquefied gas in a liquefied gas tank in the first operating state, and extracting the liquefied gas from the liquefied gas tank, evaporating the liquefied gas in an evaporator to form an evaporated gas, and feeding the evaporated gas into the combustion process of the gas turbine in a second operating state, wherein in the first operating state the power plant is supplied with supply gas from the external source, and wherein in the second operating state the evaporated gas is fed back into a supply line that leads to the combustion process.

9. The method as claimed in claim 8, wherein the supply gas is fed from the external source to a supply line, and wherein the supply line branches into a combustion line that supplies the supply gas to the combustion process and into a liquefaction line that supplies the supply gas to the gas liquefaction plant.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Exemplary embodiments of the invention are described below based on figures. In the drawings:

(2) FIG. 1 shows a method for operating a power plant in the normal operating state,

(3) FIG. 2 shows a method for operating a power plant in the special operating state,

(4) FIG. 3 shows a particular further development of the method for operating a power plant in the special operating state,

(5) FIG. 4 shows a way how an existing power plant can be extended with an emergency fuel system.

DETAILED DESCRIPTION OF INVENTION

(6) FIG. 1 shows a method for operating a power plant 1 in the normal operating state. In this normal operating state, a gas 5 is fed from a supply line 3 to a combustion process 4 of a gas turbine 2. The gas turbine comprises a compressor unit 18, the combustion process 4, and an expansion unit 19. Gas 5 is fed from the supply line 3 to the combustion process 4.

(7) In addition to the combustion process 4, gas 5 is also fed from the supply line 3 to a gas liquefaction plant 6. The gas 5 is liquefied in the gas liquefaction plant 6, wherein a liquefied gas (LNG) is formed. The liquefied gas (LNG) is stored in a liquefied gas tank 7. The liquefied gas tank corresponds to a tank which is designed so that the liquefied gas (LNG) can be cryogenically stored in it. In the present exemplary embodiment, the tank has a storage volume of 30T m.sup.3.

(8) With this, in the special operating state an operation of the gas turbine 2 would be possible for up to 14 days even in the event of failure of the supply line 3. In the present example, the gas liquefaction plant 6 has a throughput volume of 1.7 kg/s. Therefore, it is in a position to fully fill up the liquefied gas tank 7 within a year in the normal operating state of the power plant 1.

(9) FIG. 2 shows a method for operating a power plant 1 in the special operating state in which no gas 5 is available from the supply line 3. In order to be able to continue to supply the combustion process 4 of the gas turbine 2 with gas, liquefied gas (LNG) is extracted from the liquefied gas tank 7 and fed to an evaporator 8. In the evaporator 8, the liquefied gas (LNG) is evaporated and in the vaporous state is fed to the combustion process 4 of the gas turbine 2. In the event of a complete loss of supply gas, the evaporated gas may also be supplied to other consumers 30 connected to the supply line 3.

(10) In the example of FIG. 2, the liquefied gas tank 7 is a pressurized tank. The pressure at which the liquefied gas (LNG) is stored is in this case set so that the pressure of the gas after evaporating in the evaporator 8 is at such a level that it corresponds to the required pressure for the gas turbine 2.

(11) Not shown in FIG. 2 is an alternative variant in which use is made of a liquefied gas tank 7 in which the liquefied gas (LNG) is stored under atmospheric pressure. In this case, it is necessary to increase the pressure of the gas before feeding it into the combustion process 4 of the gas turbine 2. This is achieved by means of a pump which is arranged between liquefied gas tank 7 and evaporator 8.

(12) FIG. 3 shows a particular further development of the method for operating a power plant in the special operating state. In the exemplary embodiment of FIG. 3, provision is also made for a heat exchanger 14 which has a primary side 16 and a secondary side 15. The primary side 16 is the side which releases heat and the secondary side 15 is the side which absorbs heat. The heat exchanger 14 is connected in a feeding manner by its secondary side 15 to the evaporator 8. On the secondary side, the heat exchanger is connected in a discharging manner to the supply line 3 via which the gas can be fed to the combustion process 4 of the gas turbine 2. On the primary side 16, the heat exchanger 14 is connected into the intake air line 17. As a result, cold energy which becomes free during evaporation of liquefied gas in the evaporator 8 can be used for cooling the intake air of the gas turbine 2.

(13) FIG. 4 on the other hand shows a way how an existing power plant 1 can be extended with an emergency fuel system 11, and also shows a power plant 1 which is retrofitted with an emergency fuel system 11. The emergency fuel system 11 comprises a gas liquefaction plant 6, a liquefied gas tank 7, an evaporator 8, and a heat exchanger 14. The emergency fuel system 11 is integrated in a power plant which has a gas turbine 2.

(14) The gas liquefaction plant 6 is connected in a feeding manner to the supply line 3, wherein a control valve can be integrated into the connecting line in order to control the proportion of gas for the gas liquefaction plant 6. The gas liquefaction plant 6 is connected to the liquefied gas tank 7 via a line for liquefied gas. The liquefied gas tank 7 is connected via a connecting line for liquefied gas to the evaporator 8, wherein a control valve is connected into the connecting line. The liquefied gas tank 7 which is shown here is a pressurized tank which is why no subsequent pressure increase of the re-evaporated gas is required.

(15) Not shown is an alternative variant of the liquefied gas tank 7 which is operated at atmospheric pressure and in which provision has to be made for an additional pump in order to bring the liquefied gas up to the pressure level of the gas supply line again. The pump in this case is advantageously provided between the liquefied gas tank 7 and the evaporator 8.

(16) The evaporator 8 is connected in a feeding manner to the secondary side 15 of the heat exchanger 14. The secondary side of the heat exchanger 14 is connected in a discharging manner to the supply line 3, wherein a control valve is connected into this connecting line. The heat exchanger 14 is connected on the primary side into the intake air line 17 of the compressor unit 18 of the gas turbine, wherein the feed and discharge lines to the heat exchanger are equipped in each case with control valves.

(17) A power plant 1, which according to this method is retrofitted with, or equipped with, an emergency fuel system 11, has the capability of selectively operating the gas turbine 2 with gas from the supply line 3 or with evaporated gas from the emergency fuel system.