METHOD FOR GENERATING ELECTRIC ENERGY

Description

[0001] 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 steam is expanded via a steam turbine, thereby driving an electrical generator.

[0002] A process for generating electrical energy is assumed to be known. It involves natural gas enriched with hydrogen and compressed, then fed into a combustion chamber into which compressed air is also fed. In the combustion chamber, the hydrogen is oxidized with atmospheric oxygen. The resulting exhaust gas is expanded via a gas turbine, generating 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 these processes is their limited efficiency.

[0003] Methods 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.

[0004] Based on this, the present invention is based on the object of at least partially overcoming the disadvantages known from the prior art.

[0005] This problem is solved by a method having the features of the independent claim. The dependent claims are directed to advantageous developments.

[0006] The method according to the invention for generating electrical energy comprises the following steps: a) Feeding hydrogen, oxygen, and liquid water into a combustion chamber, b) Oxidation of the hydrogen with the oxygen in the combustion chamber to form water vapor; c) Expansion of the water vapor via a steam turbine, which drives an electric generator.

[0007] Hydrogen and oxygen are each supplied to the combustion chamber in pure gaseous form, in particular with a purity of preferably more than 99 vol. Hydrogen and oxygen are each supplied in a compressed state, in particular at pressures of 30 to 200 bar, particularly preferably 30 to 40 bar. A stoichiometrically balanced ratio of hydrogen and oxygen is preferably supplied, i.e., in particular, a molar hydrogen to oxygen ratio of 1.9:1 to 2.1:1.

[0008] 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 through its heating but also, to a significant extent, through the enthalpy of vaporization released when the liquid water evaporates, which makes a significant 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 addition of liquid water reduces the temperature to 1,500°C and below, preferably 1,300°C and below. The water supplied is supplied as demineralized water.Demineralized water typically has an electrical conductivity of less than 0.2 µS / cm [microsiemens per centimeter].

[0009] By adding liquid water as a coolant, water vapor is created as exhaust gas, which is removed from the combustion chamber. This vapor is then expanded via the steam turbine. The steam turbine can contain nozzles in the turbine blades to supply water for further cooling. This means that a gas turbine that only expands to atmospheric pressure is no longer necessary; instead, a steam turbine, in particular a condensing turbine, can be used, which allows expansion down to much lower pressures. This increases efficiency compared to the use of a gas turbine. It is therefore also possible for the water vapor leaving the steam turbine to contain a proportion of liquid water. The steam turbine preferably has several stages (e.g. high-pressure and low-pressure stages).

[0010] According to an advantageous embodiment, the oxygen is supplied 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. Furthermore, the formation of by-products that could arise at the high temperatures present in the combustion chamber can be avoided. Alternatively or additionally, the hydrogen is supplied to the combustion chamber via a second compressor, possibly a pressure accumulator. This improves the process control options because the pressure in the combustion chamber is variable. In particular, a hydrogen pressure can then be achieved before supply to the combustion chamber that allows optimal flow into the combustion chamber. This increases the flexibility of the process control.

[0011] According to an advantageous embodiment, the steam, after flowing through the steam turbine, is fed to a heat exchanger to transfer heat to a heat transfer medium. This allows the heat content of the steam downstream of the steam turbine to be advantageously used to heat a heat transfer medium, for example, water 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, after flowing through the steam turbine, to an intermediate stage of the steam turbine for cooling.

[0012] According to an advantageous embodiment, the steam, after flowing through the steam turbine, is fed to a condenser, where it is completely condensed into 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. Preferably, the condensed water is fed to a storage tank via a first pump. This allows the water to be withdrawn from the storage tank as needed using a second pump.

[0013] Preferably, the liquid water is taken from the storage tank for supply to the combustion chamber. This allows for a liquid water cycle, advantageously avoiding the need for additional water.

[0014] Alternatively or additionally, the water from the storage facility is preferably subjected to water electrolysis. In water electrolysis, water is split into hydrogen and oxygen using electrical energy.

[0015] 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, water from the storage tank is used. This enables a further cycle in which the gases hydrogen and / or oxygen are generated from the water, which is formed by condensation of the water vapor extracted from the combustion chamber, before being fed to the combustion chamber.

[0016] 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 unit and taken from there for supply to the combustion chamber.

[0017] This enables a process for the alternate storage and release of 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, wherein the hydrogen and oxygen produced therein are stored for later supply to the combustion chamber.

[0018] This enables the alternating storage and release of electrical energy when it is provided irregularly, especially when significant electrical energy from renewable sources, particularly photovoltaics or wind power, is fed into an electrical grid, which are highly dependent on weather conditions. The necessary measures for frequency stabilization of the electrical grid can be implemented as described above. In particular, the conversion of hydrogen to electricity via the steam turbine allows for the rapid provision of large amounts of electrical power. Furthermore, the rotating masses of the steam turbine exert an additional stabilizing effect on the grid frequency.

[0019] As a precaution, it should be noted that the numerals used here ("first", "second", ...) primarily serve (only) to distinguish between several similar objects, quantities, or processes, and therefore do not necessarily specify any interdependence and / or sequence of these objects, quantities, or processes. Should a dependence and / or sequence be required, this is explicitly stated here or will be obvious to the person skilled in the art upon studying the specifically described embodiment.

[0020] 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 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 illustrated proportions are only schematic. The same reference numerals denote the same objects, so that explanations from other figures can be used as a supplement if necessary. They show: Fig. 1 is a flow diagram of a first example of a method for generating energy; and Fig. 2 is a flow diagram of a second example of a method for generating energy.

[0021] Fig. 1shows 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 during pure oxidation of the hydrogen 1 with the oxygen 2 in the combustion chamber 3 lead to very high temperatures in the combustion chamber 3, in particular 2,000 °C [degrees Celsius] and more, liquid water 4 is fed to the combustion chamber 3 at the same time. This leads to the cooling of the gases (hydrogen 1, oxygen 2 and water vapor) in the combustion chamber 3. In particular, the evaporation enthalpy 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.

[0022] The resulting steam 5 is fed to a steam turbine 6 for expansion, which drives an electric generator 7 to generate electricity. The electricity generated is preferably fed into an electrical power grid. At the same time, the steam turbine 6 at least temporarily drives a first compressor 8, which can compress the oxygen 2 before being fed to the combustion chamber 3.

[0023] After flowing through the steam turbine 6, the steam 5, which may carry water droplets (wet steam), is fed to a heat exchanger 9, in which heat from the steam 5 is transferred to a first heat transfer medium 10, which flows through the heat exchanger 9. The first heat transfer medium 10 may, for example, also be water, which is used in another process and which is heated and possibly even evaporated while flowing through the heat exchanger 9. Alternatively or optionally additionally, this first cooling stage can also be realized by intermediate cooling in an intermediate stage of the steam turbine (in Fig. 1 not shown).

[0024] Downstream of the heat exchanger 9, the water vapor 5 flows through a condenser 11, in which the water vapor 5 condenses into liquid water 12 and simultaneously 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.

[0025] The liquid water 4 is drawn from the reservoir 15, which may have a water supply (not shown) for refilling 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 provided to pump the water 4 into the combustion chamber 3 at an appropriate pressure. At the same time, at least when needed, liquid water 16 can be drawn 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 is stored in a second intermediate reservoir 21. When needed, the hydrogen 1 is then drawn from the first intermediate reservoir 20 and fed to the combustion chamber 3.Optionally, a second compressor 22 can be provided, which enables the pressure of the hydrogen 1 to be increased before it is fed to the combustion chamber 3. This compressor can be driven via the same shaft as the first compressor 8. An electric motor (not shown) can be used for this purpose. Oxygen 2 is drawn from the second intermediate storage 21 as needed and fed to the combustion chamber 3. Both the first intermediate storage 20 and the second intermediate storage 21 preferably include 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.

[0026] The combination of the combustion chamber 3 with the water electrolyzer 17 advantageously allows for the alternating storage and release of electrical energy. If there is an excess of electrical energy, for example in an electrical power grid, this excess supply can be used to operate the water electrolyzer 17, and the resulting hydrogen 18 and oxygen 19 can be stored in the intermediate storage devices 20, 21. In the event of an undersupply of electrical energy, hydrogen 1 and oxygen 2 can then be produced from the intermediate storage devices 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, driven by the electrical generator 7, and fed into the electrical power grid. In this way, electrical energy can be alternately stored and released.This is particularly advantageous for storing electrical energy from renewable sources such as photovoltaics or wind energy, as these are not available uniformly but depend on weather conditions.

[0027] Fig. 2 shows a second example of a method for generating energy. Only the differences from 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.

[0028] With regard to the flow direction of the hydrogen 1 and the oxygen 2, the first intermediate storage device 20 is arranged downstream of the second compressor 22, and the second intermediate storage device 21 is arranged downstream of the first compressor 8. This allows the pressure in the intermediate storage devices 20, 21 to be adjusted, so that the pressure at which hydrogen 1 and oxygen 2 are supplied to the combustion chamber 3 can be regulated via the pressure in the intermediate storage devices 20, 21. Such a configuration can also be implemented with the compressors 8, 22 and the intermediate storage devices 20, 21 of the first example. As shown, one or both intermediate storage devices 20, 21 can be bypassed via bypass lines 30, so that hydrogen 1 and / or oxygen 2 is conveyed directly from the respective compressor 22, 8 into the combustion chamber 3.

[0029] In the second example, the steam turbine 6 is designed as a two-stage turbine, 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.

[0030] Furthermore, the supply lines between the compressors 8, 22 and the intermediate storage tanks 20, 21 also have gas coolers 28, through which heat can be extracted from the compressed gas streams. A third pump 29 is arranged between the storage tank 15 and the water electrolyzer 17, through which the pressure of the water 16 can be increased as it is fed to the water electrolyzer 17. The first pump 14, the second pump 23, and the third pump 29 are preferably each driven by an electric motor 24. List of reference symbols

[0031] 1 Hydrogen 2 Oxygen 3 Combustion chamber 4 Liquid water 5 Steam 6 Steam turbine 7 Electric generator 8 First compressor 9 Heat exchanger 10 First heat transfer medium 11 Condenser 12 Liquid water 13 Second heat transfer medium 14 First pump 15 Storage tank 16 Water 17 Water electrolyzer 18 Hydrogen 19 Oxygen 20 First intermediate storage tank 21 Second intermediate storage tank 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

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).