Method and system for producing energy from a high-pressure, moist gas

Abstract

The invention relates to a method for producing energy from a high-pressure, moist gas which is drawn from a reservoir (1) and is expanded for delivery to a consuming device (2). The method is characterized in that at least two hydropneumatic tanks (5), which can be connected, on one side, to the reservoir (1) and, on the other side, to the consuming device (2), are charged one after the other with high-pressure gas from the reservoir (1), in that a water turbine (4), which is provided in a gas-filled turbine pressure chamber (3) which can be connected to the hydropneumatic tanks (5) on the water side, is acted upon in a cyclical sequence, via a supply line, by the water from the water-filled hydropneumatic tank (5) currently charged with high-pressure gas, and in that the gas which, after blocking of the hydropneumatic tank (5) on the gas side, has expanded and thus displaced the water is conveyed out of the hydropneumatic tank (5) to the consuming device (2) as the water collected in the turbine pressure chamber (3) as a result of the action upon the turbine flows back into the hydropneumatic tank (5).

Description

[0001] Method and plant for generating energy from a high-pressure, moist gas

[0002] Technical field

[0003] The invention relates to a method for generating energy from a high-pressure, moist gas which is taken from a storage facility and depressurized for delivery to a consumer, and to a system for carrying out the method.

[0004] State of the art

[0005] When gas is stored in reservoirs, such as underground caverns or porous rock storage facilities, water vapor contamination of the gas is unavoidable. This means that the gas, stored under high pressure, must not only be depressurized to the pressure level of the gas network before being distributed to a consumer, usually for injection into a gas network, but also undergo a complex drying process. Furthermore, due to the corrosive nature of the water vapor-laden gas, its use in turbines for energy generation during depressurization to the gas network pressure is only possible to a limited extent. This applies not only to natural gas, but also to all gases stored under high pressure in reservoirs that have a high moisture content as a result of this storage.

[0006] To operate a heat engine efficiently even with small temperature differences between a heat source and a heat sink, it is known (WO 2010 / 057237 A2) to circulate a working fluid, after evaporating it at a higher pressure level, then expand it to a lower pressure level and condense it again. However, the evaporated working fluid is not used to drive a steam turbine, but rather to pressurize water in a pressure vessel. The water is displaced from the pressure vessel by the steam and used to drive a water turbine.The water turbine is housed in a turbine pressure chamber connected to the pressure vessel on both the liquid and steam sides. This allows the water turbine to be driven by water from the pressure vessel, which is then connected to the turbine pressure chamber on the steam side for steam expansion. The water collected in the turbine pressure chamber is then returned to the pressure vessel before the expanded steam from the turbine pressure chamber condenses and is re-evaporated for refilling the pressure vessel. However, this method, designed for energy generation from a relatively small temperature difference between a heat source and a heat sink, is not suitable for expanding and drying moist gas.

[0007] For energy storage and recovery, it is also known (DE 102020112724 A1) to provide a compressed air storage system with which pressure vessels connected to each other by a water turbine can be pressurized sequentially. Since one of the vessels is filled with water, when this pressure vessel is pressurized, the water turbine is supplied with the water from this pressure vessel. The water flows from the water turbine into the subsequent pressure vessel, displacing the air from this vessel. This pressurized air is then compressed by a compressor and fed back into the compressed air storage system. The pressure vessels are thus cyclically filled with water and pressurized with compressed air to operate the water turbine.

[0008] In another known energy storage and recovery system (EP 3321501 A1), a compressed air storage unit connected to a compressor is again used for energy storage. This unit pressurizes a water tank with compressed air so that the water from the water tank can drive a water turbine. The turbine water is collected in a water reservoir and pumped back into the water tanks for energy storage, displacing the air from the water tanks back into the compressed air storage unit.

[0009] In these known systems, a compressed air storage unit is charged to store energy, and this stored energy can then be released again under largely constant pressure conditions. Therefore, these known systems cannot be used to generate energy by expanding moist compressed gas.

[0010] Description of the invention

[0011] The invention is therefore based on the objective of designing a method for energy recovery from a high-pressure, moist gas, which is depressurized to supply a consumer, in such a way that sufficient drying of the moist gas can be ensured using simple means and at the same time advantageous energy recovery during the depressurization of the gas can be guaranteed.

[0012] Starting from a method of the type described above, the invention solves the stated problem by providing that at least two pressure water tanks, which can be connected to the storage tank on one side and to the consumer on the other, are successively pressurized with high-pressure gas from the storage tank, that a water turbine, which is provided in a gas-filled turbine pressure chamber that can be connected to the pressure water tanks on the water side, is cyclically pressurized with water from the water-filled pressure water tank pressurized with high-pressure gas via a supply line, and that the gas, which is depressurized after a gas-side closure of the pressure water tank during the displacement of the water, is conveyed from the pressure water tank to the consumer when the water accumulated in the turbine pressure chamber by the turbine pressurization flows back into the pressure water tank.As a result of these measures, it is initially possible to utilize the advantages of a water turbine for energy generation and to drive a generator for electricity production using the water turbine, usually a Pelton turbine. Since the water turbine is supplied with a pressurized water tank containing high-pressure gas, the gas displacing the water from the pressure tank is expanded, causing it to cool and the water vapor to largely condense. This expansion-induced cooling of the gas thus achieves drying without additional effort, so that the expanded and dried gas can be displaced from the pressure tank by the water that is pumped into the turbine pressure chamber and then flows back from the turbine pressure chamber into the pressure tank, and is then supplied to a consumer.The pressure difference between the operating pressure in the turbine pressure chamber and the pressure in the pressure tank determines the backflow of water from the turbine pressure chamber into the pressure tank. By using two or more pressure tanks that cyclically supply the water turbine with pressurized water in succession, not only can the turbine operation be made more consistent, but a largely continuous gas supply to the gas network can also be ensured.

[0013] To limit pressure fluctuations in the turbine pressure chamber and thus enable more consistent operation, the pressure in the turbine pressure chamber can be maintained within a predetermined range above the pressure of the expanded gas in the feed line to the consumer. This pressure limitation allows, in the event of overpressure, some of the gas to be expelled from the turbine pressure chamber into the feed line due to the gas pressure exceeding the consumer pressure level. Conversely, in the event of underpressure, it necessitates the refilling of pressurized gas into the turbine pressure chamber. The resulting largely constant operating pressure in the turbine pressure chamber ensures the cyclical discharge of turbine water from the pressure chamber into the respective pressure vessel and the associated removal of the expanded gas from the pressure vessel, without requiring any additional resources.

[0014] Since heat is generated during turbine operation, a continuous increase in water temperature is to be expected. Because the temperature conditions in the pressure vessels affect the drying of the gas through expansion, cooling the water can counteract the water heating and thus create consistent conditions for gas drying.

[0015] A plant for generating energy by expanding moist gas between a storage facility receiving the high-pressure gas and a consumer for the expanded gas is characterized by the fact that at least two pressure water tanks, which can be connected by control valves on one side to the storage facility and on the other side to a feed line for the consumer, and a gas-filled turbine pressure chamber accommodating a water turbine are provided, which can be connected to the pressure water tanks on the water side by return lines equipped with control valves and has at least one supply line for the water turbine that can be connected to the water side of the pressure water tanks by control valves.

[0016] After a water-filled pressure vessel has been pressurized with high-pressure gas from the storage tank, the control valve to the storage tank is closed and the control valve to the water turbine supply line is opened. This displaces the water from the pressure vessel, causing the gas to expand and cool. The expanding gas cools in the pressure vessel, and the water vapor contained in the gas condenses. At the end of the water turbine's pressurization cycle, the control valve to the water turbine supply line is closed. Then, after the control valves to the return line and the feed line are opened, the water flowing back from the turbine pressure chamber into the pressure vessel forces the expanded gas out of the pressure vessel and into the feed line.After the pressure vessel is filled with water and the associated discharge of the gas that dried during its expansion, the control valves to the return line and the feed line are closed. This allows the control valve to the storage tank to be opened, allowing the pressure vessel to be pressurized with high-pressure gas from the storage tank for a new cycle. Depending on the number of pressure vessels, the next one is opened either after or during the return of the turbine water from the turbine pressure chamber.

[0017] Pressure water tanks are controlled for turbine operation, so that the water turbine is cyclically supplied by the individual pressure water tanks one after the other, and accordingly the injection of the expanded gas into the gas network takes place in a cyclical sequence via the individual pressure water tanks.

[0018] To maintain the pressure in the turbine pressure chamber within a specific range above the pressure level in the gas network, the turbine pressure chamber can be connected to the storage tank via a pressure reducing valve and have an overpressure line connected to the feed line, equipped with a pressure relief valve. If the pressure in the turbine pressure chamber drops below a predetermined value, gas from the storage tank is pumped into the turbine pressure chamber via the pressure reducing valve to increase the chamber pressure. Conversely, in the event of overpressure, the pressure relief valve in the overpressure line opens, allowing gas to flow from the turbine pressure chamber into the feed line. The operating pressure in the turbine pressure chamber can thus be kept largely constant.

[0019] To remove residual water mist and any water crystals that may form from the expanded gas, a water separator can be provided in the feed line, ensuring that the consumer receives sufficiently dry gas expanded to the required pressure. As previously mentioned, it is advantageous to cool the water in the pressure tanks. At least one cooling device can be provided for this purpose, preferably in the return line, although this is not mandatory, as only water cooling is required, which can also be achieved by heat exchangers in the pressure tanks and / or the turbine pressure chamber.

[0020] Brief description of the invention

[0021] The method according to the invention is explained in more detail with reference to the drawing, which shows a system according to the invention in a schematic block diagram.

[0022] Ways to implement the invention

[0023] An inventive system for generating energy by expanding moist gas between a storage tank 1, which receives the pressurized gas, and a consumer 2 for the expanded gas comprises a water turbine 4 arranged in a turbine pressure chamber 3 and several pressure water tanks 5, which are connected to the turbine pressure chamber 3 by supply lines 6 for supplying the water turbine 4. The supply lines 6, which can be controlled by means of control valves 7, each have supply nozzles 8, although this is not mandatory. For example, the supply lines 6 could terminate in a common supply line which is provided with at least one supply nozzle.By arranging several individually controllable spray nozzles 8 of a common spray line 6, it is possible to control the water turbine 4 for power adjustment via a different number of spray nozzles 8.

[0024] The pressure water tanks 5 are connected on the gas side to the storage tank 1 via connecting lines 10 equipped with control valves 9, and via control valves 11 to a feed line 12 for the consumer 2. On the water side, the pressure water tanks 5 are connected via control valves 13 to a return line 14 of the turbine pressure chamber 3. The turbine pressure chamber 3 itself is filled with gas, and to maintain a predefinable pressure range, the turbine pressure chamber 3 is connected on the gas side to the storage tank 1 via a pressure reducing valve 15 and to the feed line 12 via a pressure relief valve 16.

[0025] The water turbine 4 is cyclically supplied with pressurized water from the individual pressure tanks 5. Different operating states are indicated in the drawing for the depicted pressure tanks 5. The pressure tank 5 on the left in the drawing, filled with water, represents the initial state in which, after this pressure tank 5 has been supplied with pressurized water, both the gas-side control valves 9, 11 and the water-side control valves 7, 13 are closed. If the control valve 7 for the supply line 6 is now opened, the water, under the pressure of the high-pressure gas, flows from the pressure tank 5 through the supply nozzle 8 into the turbine pressure chamber 3 to supply the water turbine 4. The pressurized water drives a generator 17, which feeds electrical energy into a power grid 19 via a frequency converter 18.

[0026] To utilize the outlet pressure of the high-pressure gas from storage tank 1 for a longer period of time for turbine operation, the control valve 9 in the connecting line 10 to storage tank 1 can be kept open longer. This ensures that the gas expansion after closing the connecting line 10 only occurs after some of the water has been expelled from the pressure tank 5. This can lead to the next pressure tank 5 in the supply cycle being used before the gas in the preceding pressure tank 5 has fully expanded to the intended pressure level. However, this is irrelevant because, due to the prevailing pressure differential, water can also flow from the pressure tanks 5 into the turbine chamber 3 via the return line 14.With the displacement of the water from the pressure tank 5 after the closing of the control valve 9 in the connecting line 10 to the storage tank 1, the gas introduced into the pressure tank 5 at a pressure of, for example, 100 bar, expands to, for example, 45 bar, i.e., to a pressure level slightly higher than the pressure level of the consumer 2, usually a gas network, of, for example, 40 bar, and is thereby cooled, so that the water vapor contained in the gas condenses and possibly crystallizes.

[0027] The water introduced into the turbine pressure chamber 3 to drive the water turbine 4 causes a pressure increase in the turbine pressure chamber 3. This pressure increase should preferably be limited, which is achieved by means of the pressure relief valve 16. If the predetermined upper limit of the operating pressure, for example 50 bar, is exceeded, the pressure relief valve 16 opens and excess gas flows into the feed line 12. The operating pressure in the turbine pressure chamber 3 is determined by the pressure reducing valve 15.

[0028] At the end of the supply of water to the water turbine 4 from a pressure tank 5, an operating state is reached as indicated in the right-hand pressure tank 5 of the drawing. By closing the control valve 7 in the supply line 6 and opening the control valve 13 to the return line 14 as well as the control valve 11 to the feed line 12, the water flows back from the turbine pressure chamber 3 into the pressure tank 5, at an approximately constant operating pressure in the turbine pressure chamber 3. The water flowing back into the pressure tank 5 displaces the expanded, dried gas from the pressure tank 5 into the feed line 12. To separate any residual water mist, the feed line 12 passes through a water separator 20.

[0029] While two pressure water tanks 5 are used in a cyclical sequence, overlapping cyclical operation can be achieved with three or more pressure water tanks 5. Since the water in the turbine pressure chamber 3 heats up, water cooling can be advantageous to avoid impairing the cooling required for gas drying through gas expansion. For this reason, a cooling device 21 in the form of a heat exchanger is indicated in the return line 14.

[0030] A method and a system according to the invention are particularly suitable for the depressurization of gases stored under pressure in underground reservoirs, such as natural gas or hydrogen. However, the invention is not limited to these areas of application and can be advantageously used wherever moist, high-pressure gas needs to be depressurized to the pressure level of a consumer for energy recovery purposes. Consumers can include a gas supply network, a gas processing plant, or even a pressure storage facility in which the depressurized, dried gas is temporarily stored for further use.

Claims

Patent claims 1. A method for generating energy from a high-pressure, moist gas, which is taken from a storage tank (1) and depressurized for delivery to a consumer (2), characterized in that at least two pressure water tanks (5) connectable on the one hand to the storage tank (1) and on the other hand to the consumer (2) are successively pressurized with high-pressure gas from the storage tank (1), and that a water turbine (4), which is provided in a gas-filled turbine pressure chamber (3) connectable to the pressure water tanks (5) on the water side, is cyclically driven by the water from the pressure water tank (5) pressurized with high-pressure gas.a pressure water tank (5) filled with water is pressurized via a supply line and that, after a gas-side blockage of the pressure water tank (5) during the displacement of the water, the gas released during the return flow of the water accumulated in the turbine pressure chamber (3) through the turbine pressurization into the pressure water tank (5) is conveyed from the pressure water tank (5) to the consumer (2).

2. Method according to claim 1, characterized in that the pressure in the turbine pressure chamber (3) is maintained within a predetermined range above the pressure of the gas released for the consumer (2).

3. Method according to claim 1 or 2, characterized in that the water in the pressure water tanks (5) is cooled.

4. Plant for energy generation by expanding moist gas between a storage tank (1) receiving the high-pressure gas and a consumer (2) for the expanded gas, characterized in that at least two pressure water tanks (5) connectable by control valves (1 1) on the one hand to the storage tank (1) and on the other hand to a feed line (12) for the consumer (2) and a water turbine (4) containing gas filled turbine pressure chamber (3) are provided, which can be connected to the pressure water tanks (5) on the water side by return lines (14) equipped with control valves (13) and has at least one supply line (6) for the water turbine (4) which can be connected to the water side of the pressure water tanks (5) by means of control valves (7).

5. System according to claim 4, characterized in that the turbine pressure chamber (3) is connected to the storage tank (1) by a pressure reducing valve (15) and has an overpressure line connected to the feed line (12) and equipped with a pressure relief valve (16).

6. System according to claim 4 or 5, characterized in that in the A water separator (20) is provided in the feed line (12).

7. System according to one of claims 4 to 6, characterized in that at least one cooling device (21) is provided for the water of the pressure water tank (5).

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