METHOD FOR OPERATION OF AN INDUSTRIAL PLANT AND AN INDUSTRIAL PLANT

Abstract

A method for operation of an industrial plant having an energy accumulator unit for production of synthetic natural gas, a power plant unit for production of electricity, an oxygen tank, a carbon dioxide tank and a water tank. In a first operation mode the energy accumulator unit is supplied with excessed electricity from the public grid to produce synthetic natural gas, wherein the produced synthetic natural gas is discharged in a gas network, while oxygen and water which are produced together with the synthetic natural gas are stored in the oxygen tank and the water tank correspondingly. In a second operation mode gas from the gas network together with oxygen from the oxygen tank and water from the water tank are used in the power plant unit to produce electricity, which is supplied to the public grid. This way electricity production excess is efficiently accumulated for industrial or municipal use.

Claims

1. A method for operation of an industrial plant, comprising an energy accumulator unit for production of synthetic natural gas, a power plant unit for production of electricity, an oxygen tank, a carbon dioxide tank, and a water tank, the method comprising: in a first operation mode, supplying the energy accumulator unit with excessed electricity from a public grid in order to produce synthetic natural gas, wherein the produced synthetic natural gas is discharged in a gas network, while oxygen and water which are produced together with the synthetic natural gas are stored in the oxygen tank and the water tank correspondingly, and in a second operation mode, using gas from the gas network together with oxygen from the oxygen tank and water from the water tank in the power plant unit to produce electricity, which is supplied to the public grid.

2. The method according to claim 1, wherein in the first operation mode the SNG is produced in a Sabatier reaction.

3. The method according to claim 2, wherein water from the water tank is used in an electrolysis reaction to produce oxygen and hydrogen, which hydrogen is used for the Sabatier reaction.

4. The method according to claim 1, wherein in the second operation mode the gas supplied from the gas network is burned together with oxygen from the oxygen tank in a combustor and a resulting combustion mixture is used to drive a turbine.

5. The method according to claim 4, wherein water from the water tank is used to regulate the temperature in the combustor.

6. The method according to claim 4, wherein a steam-gas-mixture from the turbine is at least partially condensed in a heat exchanger producing water and steam and carbon dioxide mixture, where water and carbon dioxide are stored in the water tank and the carbon dioxide tank correspondingly.

7. The method according to claim 6, wherein heat from the heat exchanger is used for district heating.

8. The method according to claim 1, wherein the energy accumulator unit and the power plant unit are operated alternatingly.

9. An industrial plant adapted for carrying out the method according to claim 1, comprising: an energy accumulator unit for production of synthetic natural gas, a power plant unit for production of electricity, an oxygen tank, a carbon dioxide tank and a water tank.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Embodiments of the invention are now described, by way of example only, with reference to the accompanying drawing, of which the only FIGURE shows schematically an industrial plant 1.

DETAILED DESCRIPTION OF INVENTION

[0032] The industrial plant 1 comprises an energy accumulator unit 3 for production of synthetic natural gas and a power plant unit 5 for production of electricity. In the power plant unit 5 additionally heat is produced. The industrial plant further comprises an oxygen tank 7, a water tank 9 and a carbon dioxide tank 11.

[0033] In the embodiment shown in the FIGURE the energy accumulator unit 3 consists of a hydrogen electrolysis system 13 and a Sabatier reactor 15. The hydrogen electrolysis system 13 is supplied with electricity from the public grid 17 by means of a power cable 19. The Sabatier reactor 15 is connected to a gas network via a gas discharge line 31.

[0034] The power plant unit 5 consists of a combustor 21, a turbine 23, a generator 25 and a heat exchanger 27. The combustor 21 is operated with gas from the gas network 29 provided by a gas supply line 33.

[0035] In a first operation mode of the industrial plant 1, in case of renewable electricity surplus in the public grid 17, this excessed energy is accumulated or stored in the energy accumulator unit 3 in form of oxygen stored in the oxygen tank 7 and SNG produced in the Sabatier reactor 15 and supplied to the gas network via the gas discharge line 31.

[0036] Water taken from the water tank 9 via a first water feed line 34 is provided to the hydrogen electrolysis system 13, in which the water molecules are split into hydrogen and oxygen using electrical current from the public grid 17. The oxygen stream is fed via an oxygen discharge line 35 into the oxygen tank 7 for storage purposes. The hydrogen stream is provided via a hydrogen feed line 37 into the Sabatier reactor 15, in which it reacts together with carbon dioxide provided by a feed line 39 from the carbon dioxide tank 11 to produce SNG (methane). The SNG produced in the energy accumulator unit 3 is fed into the gas network 29 by means of outflow gas pipe 31 and can be potentially transported to far distant underground gas storage facilities. Another product of the Sabatier reaction is water, which is discharged in a first water discharge line 41 and stored in the water tank 9.

[0037] Hence, in the first operation mode excessed energy from the public grid is stored locally by converting it into oxygen and water and the remaining part of the excessed energy is stored in form of synthetic natural gas in the gas network or stored in distant gas storage facilities connected to the gas network.

[0038] Normally, the power plant unit 5 is shutdown during the first operation mode.

[0039] In a second operation mode gas from the gas network 29 together with oxygen from the oxygen tank 7 and water from the water tank 9 are used in the power plant unit 5 to produce electricity. Natural gas or accumulated SNG is supplied from the gas network 29 via the gas supply line 33 into the combustor 21 to generate a steam-gas-mixture. The fuel is burned there with oxygen fed from the local oxygen tank 7 via an oxygen supply line 43. The flue gas of the combustion process is a mixture of water steam and carbon dioxide and its temperature is adjusted by the amount of water from the water tank 9 via a second water feed line 45 and injected into the combustor 21. The combustion mixture is fed into a turbine 23 where it expands.

[0040] The mechanical energy from the turbine 23 is transferred to the electrical generator 25, thus generating electricity. This electrical energy is conveyed to the public electricity grid 17.

[0041] The steam-gas-mixture is discharged from the turbine 23 into a heat exchanger 27. In the heat exchanger 27 the remaining thermal energy is transferred to a coolant 47 cycle. The steam-gas-mixture is cooled down there. The water steam from the mixture condenses and is discharged through a second water discharge line 49 into the water tank 9. The incondensable, clean carbon dioxide is discharged through a discharge line 51 into the local carbon dioxide tank 11.

[0042] This process, in which the locally stored energy (oxygen and water) together with SNG from the gas network are converted into electricity and heat, can be considered discharging of the energy accumulator unit 3. In this cycle, the total energy of methane, i.e. the upper heating value is employed compared with standard devices. This value is about 10% higher than the lower heating value.

[0043] Although the present invention has been described in detail with reference to the preferred embodiment, it is to be understood that the present invention is not limited by the disclosed examples, and that numerous additional modifications and variations could be made thereto by a person skilled in the art without departing from the scope of the invention.