EP4105551B1 - Method for supply of electrical energy - Google Patents

Description

The present invention relates to a method for generating electrical energy, in which hydrogen is oxidized with oxygen in a combustion chamber with the addition of liquid water for cooling and the resulting water vapor is expanded via a steam turbine, thereby driving an electrical generator.

A process for generating electrical energy is assumed to be known, in which natural gas enriched with hydrogen and compressed is fed into a combustion chamber into which compressed air is also fed. In the combustion chamber, the hydrogen is oxidized with the oxygen in the air. The resulting exhaust gas is expanded via a gas turbine to generate electrical energy. Furthermore, corresponding systems are assumed to be known in which pure hydrogen is converted and the resulting exhaust gas is then fed into a gas turbine to generate electrical energy. The disadvantage of the processes assumed to be known is the limited efficiency.

Processes for generating electrical or mechanical energy in which hydrogen is oxidized with oxygen in a combustion chamber and the resulting steam is expanded via a steam turbine are known from US 3,459,953 A , US 2005/223711 A1 , EP 3 643 886 A2 , DE 10 2019 216242 A1 , WO 2019/032755 A1 and US 3 101 592 A .

Proceeding from this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art.

This problem is solved by a method with the features of the independent claim. The dependent claims are directed to advantageous further developments.

1. a) Zuführen von Wasserstoff, Sauerstoff und flüssigem Wasser in eine Brennkammer,
2. b) Oxidation des Wasserstoffs mit dem Sauerstoff in der Brennkammer unter Bildung eines Wasserdampfes;
3. c) Entspannen des Wasserdampfes über eine Dampfturbine, die einen elektrischen Generator antreibt.

The method according to the invention for generating electrical energy comprises the following steps:

1. a) supplying hydrogen, oxygen and liquid water into a combustion chamber,
2. b) Oxidation of hydrogen with oxygen in the combustion chamber to form water vapor;
3. c) Expanding the steam through a steam turbine, which drives an electric generator.

Hydrogen and oxygen are each supplied to the combustion chamber in a gaseous state in a pure state, in particular each with a purity of preferably more than 99 vol.%. The supply of hydrogen and oxygen is carried out in a compressed manner, in particular with pressures of 30 to 200 bar, particularly preferably 30 to 40 bar. Preferably, a stoichiometrically balanced ratio of hydrogen and oxygen is supplied, in particular a molar ratio of hydrogen to oxygen of 1.9:1 to 2.1:1.

The liquid water is preferably fed into the combustion chamber in droplet form, in particular via one or more nozzles, in particular one or more atomizing nozzles, in order to achieve the largest possible surface area for the liquid water. The liquid water cools the gases in the combustion chamber on the one hand by heating it up, but also very significantly by the enthalpy of vaporization released when the liquid water evaporates, which makes a major contribution to cooling the gases. This can significantly reduce the temperature in the combustion chamber. If, without cooling by liquid water, temperatures of 2,000°C [degrees Celsius] and more exist in the combustion chamber, the temperature can be reduced to 1,500 °C and less, preferably 1,300 °C and less, by adding liquid water. The water supplied is supplied as demineralized water. Demineralized water usually has an electrical conductivity of less than 0.2 µS/cm [microsiemens per centimeter].

By adding liquid water as a coolant, water vapor is produced as exhaust gas, which is discharged from the combustion chamber. This is then expanded via the steam turbine. The steam turbine can contain nozzles in the blades of the turbine for the supply of water for further cooling. A gas turbine that only expands to atmospheric pressure is therefore no longer necessary; instead, a steam turbine, in particular a condensing turbine, can be used, which allows expansion to much lower pressures. This enables an increase in efficiency compared to the use of a gas turbine. It is therefore also possible for the water vapor that leaves the steam turbine to contain a proportion of of liquid water. The steam turbine preferably has several stages (e.g. high-pressure and low-pressure stages).

According to an advantageous embodiment, the oxygen is fed to the combustion chamber via a compressor, possibly a pressure accumulator. This enables a further increase in efficiency through the use of pure oxygen instead of air, which requires the compression of a significantly smaller mass flow. In addition, the formation of by-products that could arise at the high temperatures in the combustion chamber can be avoided. Alternatively or additionally, the hydrogen is fed to the combustion chamber via a second compressor, possibly a pressure accumulator. This improves the possibilities for process control, since the pressure in the combustion chamber is variable. In particular, a pressure of the hydrogen can then be achieved before feeding to the combustion chamber that allows optimal flow into the combustion chamber. This increases the flexibility of the process control.

According to an advantageous embodiment, the steam is fed to a heat exchanger after flowing through the steam turbine to release heat to a heat transfer medium. This allows the heat content of the steam downstream of the steam turbine to be used advantageously to heat a heat transfer medium, for example water that is used as process water or process steam in other processes. This further increases the overall efficiency. Alternatively or additionally, this can also be achieved by feeding the steam to an intermediate stage of the steam turbine for cooling after flowing through the steam turbine.

According to an advantageous embodiment, the water vapor is fed to a condenser after flowing through the steam turbine and is completely condensed there to form liquid water. This allows the resulting condensate to be advantageously reused, for example for feeding into the combustion chamber as a cooling medium or as a reactant in water electrolysis. The condensed water is preferably fed to a storage tank via a first pump. This If necessary, the water can be extracted from the storage tank using another pump.

Preferably, the liquid water is taken from the storage tank for supply to the combustion chamber. This allows a circular process of the liquid water, which advantageously avoids the supply of additional water.

Alternatively or additionally, the water from the storage tank is preferably subjected to water electrolysis. In water electrolysis, water is split into hydrogen and oxygen using electrical energy.

Preferably, at least one of the following gases: hydrogen and oxygen is generated by water electrolysis before being fed to the combustion chamber, in particular using water from the storage tank. This enables a further cycle in which the gases hydrogen and/or oxygen are generated from the water before being fed to the combustion chamber, which has been created by condensation from the water vapor that is taken from the combustion chamber.

According to an advantageous embodiment, at least one of the following gases produced in water electrolysis: hydrogen and oxygen is stored in an intermediate storage facility and removed from there for supply to the combustion chamber.

This enables a method for alternately storing and releasing electrical energy, in which, in the event of an energy demand, electrical energy is generated as described above and, in the event of an energy surplus, electrical energy is used to operate a water electrolyzer, whereby the hydrogen and oxygen produced therein are stored for later supply to the combustion chamber.

This enables alternating storage and release of electrical energy when it is provided irregularly, especially when significant electrical energy from renewable sources, in particular photovoltaics or wind energy, which are heavily dependent on weather conditions, is fed into an electrical energy network. The necessary measures for frequency stabilisation of the electrical energy network can be implemented as described above. In particular, the conversion of hydrogen into electricity via the steam turbine allows a large amount of electrical power to be made available quickly. Furthermore, the rotating masses of the steam turbine have an additional stabilizing effect on the grid frequency.

As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, sizes or processes, and in particular do not necessarily specify any dependency and/or sequence of these objects, sizes or processes in relation to one another. Should a dependency and/or sequence be required, this is explicitly stated here or it is obvious to the expert when studying the specifically described design.

Fig. 1

ein Fließbild eines ersten Beispiels eine Verfahrens zur Erzeugung von Energie; und

Fig. 2

ein Fließbild eines zweiten Beispiels eine Verfahrens zur Erzeugung von Energie.

The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and to combine them with other components and findings from the present description and/or figures. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic. The same reference symbols denote the same objects, so that explanations from other figures can be used in addition if necessary. They show:

Fig. 1

a flow diagram of a first example of a process for generating energy; and

Fig. 2

a flow diagram of a second example of a process for generating energy.

Fig. 1 shows a flow diagram of a first example of a process for generating energy, in which pure hydrogen 1 and pure oxygen 2 are fed to a combustion chamber 3. In the combustion chamber 3, the hydrogen 1 oxidizes with the oxygen 2 to form water. Since the temperatures in a pure oxidation of the hydrogen 1 with the oxygen 2 in the combustion chamber 3 can lead to very high temperatures in the combustion chamber 3, in particular of 2,000 °C [degrees Celsius] and more, liquid water 4 is simultaneously supplied to the combustion chamber 3. This leads to the cooling of the gases (hydrogen 1, oxygen 2 and water vapor) in the combustion chamber 3. In particular, the enthalpy of vaporization of the supplied water 4 is also available for cooling. The water 4 is preferably sprayed into the combustion chamber 3 via one or more spray nozzles. Water vapor 5 is discharged from the combustion chamber 3, which is composed on the one hand of the water formed from the reaction of the hydrogen 1 with the oxygen 2 and on the other hand of the evaporated and heated liquid water 4 supplied.

The resulting water vapor 5 is fed to a steam turbine 6 for expansion, which drives an electric generator 7 to generate electricity. The electricity generated in this way is preferably fed to an electrical power network. At the same time, the steam turbine 6 drives, at least temporarily, a first compressor 8, by means of which the oxygen 2 can be compressed before being fed to the combustion chamber 3.

After flowing through the steam turbine 6, the water vapor 5, which may carry water in the form of drops (wet water vapor), is fed to a heat exchanger 9, in which heat from the water vapor 5 is transferred to a first heat transfer medium 10, which flows through the heat exchanger 9. The first heat transfer medium 10 can also be water, for example, which is used in another process and which is heated and possibly even evaporated while flowing through the heat exchanger 9. Alternatively or optionally in addition, this first cooling stage can also be implemented by intermediate cooling in an intermediate stage of the steam turbine (in Fig. 1 not shown).

Downstream of the heat exchanger 9, the water vapor 5 flows through a condenser 11, in which the water vapor 5 condenses to liquid water 12 and at the same time releases heat to a second heat transfer medium 13. The liquid water 12 is fed to a storage tank 15 via a first pump 14.

The liquid water 4 is taken from the reservoir 15, which can have a water supply (not shown) for filling up with water from outside the system, before being fed to the combustion chamber 3. If the pressure level in the reservoir 15 is not high enough, a second pump 23 can optionally be designed, which pumps the water 4 into the combustion chamber 3 at an appropriate pressure. At the same time, at least when required, liquid water 16 can be taken from the reservoir 15 and fed to a water electrolyzer 17, in which hydrogen 18 and oxygen 19 are generated from the supplied water 16 using electrical energy. The hydrogen 18 is stored under pressure in a first intermediate reservoir 20 and the oxygen 19 in a second intermediate reservoir 21. The hydrogen 1 is then taken from the first intermediate reservoir 20 when required and fed to the combustion chamber 3. Optionally, a second compressor 22 can be formed, which enables a pressure increase of the hydrogen 1 before it is fed to the combustion chamber 3. This can be driven via the same shaft as the first compressor 8. An electric motor (not shown) can be used as a drive for this. If required, the oxygen 2 is taken from the second intermediate storage 21 and fed to the combustion chamber 3. Both the first intermediate storage 20 and the second intermediate storage 21 preferably comprise external feeds (not shown here), via which the intermediate storages 20, 21 can be filled with hydrogen or oxygen independently of the operation of the water electrolyzer 17.

The combination of the combustion chamber 3 with the water electrolyzer 17 advantageously allows the alternating storage and release of electrical energy. If there is an excess supply of electrical energy, for example in an electrical energy network, this excess supply can be used to operate the water electrolyzer 17 and the hydrogen 18 and oxygen 19 produced thereby can be stored in the intermediate storage units 20, 21. If there is an insufficient supply of electrical energy, hydrogen 1 and oxygen 2 can then be produced from the intermediate storage units 20, 21 to generate electrical energy by combustion in the combustion chamber 3 with expansion of the resulting water vapor 5 in the steam turbine 6 under the drive of the electrical generator 7 and fed to the electrical This allows electrical energy to be stored and released alternately. This is particularly advantageous for storing electrical energy from renewable sources such as photovoltaics or wind energy, as these are not available evenly but depend on the weather conditions.

Fig. 2 shows a second example of a method for generating energy. Only the differences to the first example will be discussed here; otherwise, to avoid repetition, reference is made to the description of the first example. In the second example, the second compressor 22 and/or the first compressor 8 are driven by an electric motor 24.

With regard to the flow direction of the hydrogen 1 and the oxygen 2, the first intermediate storage 20 is formed downstream of the second compressor 22 and the second intermediate storage 21 downstream of the first compressor 8. This allows the pressure in the intermediate storages 20, 21 to be adjusted so that the pressure at which hydrogen 1 and oxygen 2 are provided for the combustion chamber 3 can be regulated via the pressure in the intermediate storages 20, 21. Such a design can also be implemented with the compressors 8, 22 and the intermediate storages 20, 21 of the first example. As shown, one or both intermediate storages 20, 21 can be bypassed via bypass lines 30 so that hydrogen 1 and/or oxygen 2 is fed directly from the respective compressor 22, 8 into the combustion chamber 3.

In the second example, the steam turbine 6 is designed in two stages, i.e. it has a first stage 25 and a second stage 26, through which steam 5 flows one after the other. An intercooler 27 is formed between the first stage 25 and the second stage 26, via which the steam 5 can be intercooled between the first stage 25 and the second stage 26.

Furthermore, the supply lines between the compressors 8, 22 and the intermediate storage tanks 20, 21 also have gas coolers 28, via which heat can be extracted from the compressed gas streams. A third pump 29 is formed between the storage tank 15 and the water electrolyzer 17, via which the pressure of the water 16 at supply to the water electrolyzer 17 can be increased. First pump 14, second pump 23 and third pump 29 are preferably each driven by an electric motor 24.

list of reference symbols

1

hydrogen

2

oxygen

3

combustion chamber

4

liquid water

5

water vapor

6

steam turbine

7

electric generator

8

first compressor

9

heat exchanger

10

first heat transfer medium

11

capacitor

12

liquid water

13

second heat transfer medium

14

first pump

15

memory

16

Water

17

water electrolyzer

18

hydrogen

19

oxygen

20

first cache

21

second buffer

22

second compressor

23

second pump

24

electric motor

25

first stage of the steam turbine

26

second stage of the steam turbine

27

intercooler

28

gas cooler

29

third pump

30

bypass line

Claims (9)

1. Method for generating electrical energy, comprising the following steps:

   a) feeding hydrogen (1), oxygen (2) and liquid water (4) into a combustion chamber (3),

   b) oxidizing the hydrogen (1) with the oxygen (2) in the combustion chamber (3) with formation of steam (5);

   c) expanding the steam (5) by means of a steam turbine (6), which drives an electrical generator (7),

   in which method the steam (5), after flowing through the steam turbine (6), is fed to a heat exchanger (9) for discharging heat to a heat transfer medium (10),

   in which method the steam (5), after flowing through the steam turbine (6), is fed to a condenser (11) and there is fully condensed to produce liquid water (12).
2. Method according to Claim 1, in which the oxygen (2) is fed to the combustion chamber (3) via a first compressor (8).
3. Method according to either of the preceding claims, in which the hydrogen (1) is fed to the combustion chamber (3) via a second compressor (22).
4. Method according to any of the preceding claims, in which the condensed water (12) is fed to a reservoir (15) via a first pump (14).
5. Method according to Claim 4, in which the liquid water (4) is taken from the reservoir (15) in order to be fed to the combustion chamber (3).
6. Method according to Claim 4 or 5, in which water (16) from the reservoir (15) is subjected to water electrolysis.
7. Method according to any of the preceding claims, in which at least one of the following gases: hydrogen (1) and oxygen (2) is produced by water electrolysis before being fed to the combustion chamber (3).
8. Method according to Claim 7, in which at least one of the following gases produced in the water electrolysis: hydrogen (18) and oxygen (19) is stored in a buffer reservoir (20, 21) and taken from this buffer reservoir in order to be fed to the combustion chamber (3).
9. Method for alternately storing and discharging electrical energy, in which method, in the case of an energy requirement, electrical energy is generated in accordance with the method according to one of the preceding claims and, in the case of an energy surplus, electrical energy is used to operate a water electrolyser (17), the hydrogen (18) and oxygen (19) produced in the water electrolyser being stored in order to be subsequently fed to the combustion chamber (3).

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