EP3746725B1 - Production of liquefied natural gas in a gas accumulator - Google Patents

Description

Area

Exemplary embodiments of the invention relate to the production of liquid gas in a gas storage facility.

background

In Europe, an increase in liquid gas is expected in the coming years. In the media, liquid gas is traded as a bridging technology for decarbonization. Liquid gas is mentioned as a possible replacement for diesel fuel, especially in long-distance transport. If liquid gas gains acceptance as an alternative fuel to diesel, for heavy goods traffic or for shipping (especially inland shipping), a technical supply concept would be desirable.

Flexible supply of various customer groups (e.g. inland shipping, filling stations for heavy goods vehicles, to name just a few non-limiting examples) with liquid gas as a fuel would be desirable, with the loss of natural gas volumes in gas networks and trading in particular being able to be reduced.

The conventional production of liquid gas is very energy-intensive. Operating costs are the main cost driver. Due to the costs, liquid gas as an energy source has so far only been used in selected niches.

Furthermore, it is known that when natural gas is stored in a gas storage facility, the cold produced is destroyed in a cost-intensive and unused manner.

In the article of Authors Rathmann et al. entitled "Which Liquefaction process suits best for LNG-Peakshaving "It is stated, among other things, that in the area of Gas supply networks, so-called peak-shaving power plants, can play a legitimate role in absorbing peak loads and supporting the availability of the supply of gas. The benefit depends on a large number of parameters, the correct selection of which has an impact on the gas liquefaction process. D1 discloses a superimposed cycle gas expansion process that balances the cycle gas not available as natural gas by compressing it with a compressor. The compressor compresses the gas to the same pressure as the gas supplied to the power plant. the U.S. 3,182,461 A discloses the distribution of natural gas and in particular the recovery of a portion of the gas as a liquid by appropriate conversion of the inherent energy of the gas in the pipeline.

the U.S. 6,085,547 A discloses a method according to the preamble of claim 1.

The natural gas is converted into liquid natural gas under high pressure and free from impurities.

It would be desirable to be able to provide a solution in order to be able to produce liquefied gas in a cost-optimized manner.

Summary of some exemplary embodiments of the invention

Against the background of this prior art, the object of the present subject matter is to provide a solution for being able to produce liquid gas as cost-effectively as possible.

This object is achieved by a method having the features of claim 1.

• Reduzierung eines Drucks von in einem Gasspeicher gespeicherten Erdgas, wobei nach der Reduzierung das Erdgas einen vorbestimmten konstanten Druck aufweist;
• Reinigung von in dem Gasspeicher gespeicherten und entspannten Erdgas; und
• Erzeugung von Flüssiggas basierend auf dem gereinigten Erdgas, wobei die Erzeugung des Flüssiggases im Rahmen der Ausspeicherung von in dem Gasspeicher gespeicherten Erdgas in ein mit dem Gasspeicher verbundenes Gasnetz durchgeführt wird, und
• der Gasspeicher ein Untergrundgasspeicher ist
• wobei
  • die eine oder mehreren Vorrichtungen zur Ausführung und/oder Steuerung des Verfahrens eingerichtet sind oder jeweilige Mittel zur Ausführung und/oder Steuerung der Schritte des Verfahrens umfassen,
  • dadurch gekennzeichnet, dass die eine oder mehreren Vorrichtungen
  • die das Verfahren durchführen und/oder steuern innerhalb des Untergrundgasspeichers angeordnet sind.

According to a first aspect of the invention, a method for producing liquid gas, carried out by one or more devices, is described, the method comprising:

• reducing a pressure of natural gas stored in a gas storage tank, after the reduction the natural gas is at a predetermined constant pressure;
• Purification of natural gas stored and expanded in the gas storage facility; and
• Production of liquefied gas based on the cleaned natural gas, the production of the liquefied gas being carried out as part of the withdrawal of natural gas stored in the gas storage facility into a gas network connected to the gas storage facility, and
• the gas storage facility is an underground gas storage facility
• whereby
  • the one or more devices are set up for executing and/or controlling the method or comprise respective means for executing and/or controlling the steps of the method,
  • characterized in that the one or more devices
  • which carry out and/or control the method are arranged within the underground gas storage facility.

A differential pressure of about 55 bar is required to convert natural gas as a feedstock into liquid gas by means of an expansion. This differential pressure is regularly already known as the difference between the natural gas stored in the gas reservoir and a pipeline of a transport network for transporting the natural gas, e.g. B. to consumers present. In order to be able to generate liquefied gas in a cost-optimized manner, the existing pressure difference in a gas storage facility is used.

According to the invention, the method according to the first aspect can be carried out by a device (for example a device for generating liquid gas). The method according to the first aspect may alternatively be performed by multiple devices, e.g. B. a device for cleaning natural gas and another device for generating liquid gas are carried out together. The one or more Devices are set up according to the invention for executing and/or controlling the method according to the first aspect of the invention or comprise respective means for executing and/or controlling the steps of the method according to the first aspect of the invention.

In the event that the method according to the first aspect of the invention is carried out together by one or more devices (e.g. device for cleaning natural gas and another device for generating liquid gas), the respective devices can correspondingly have respective means for execution and/or control of the steps carried out by the respective device (e.g. device for cleaning natural gas or another device for generating liquid gas). For example, not all steps of the method according to the first aspect of the invention are carried out by one of the devices.

According to a second exemplary aspect of the invention, which is not the subject of the present claims, an apparatus arranged to carry out and/or control the method according to the first aspect of the invention or respective means for carrying out and/or controlling the steps of the method is disclosed according to the first aspect of the invention. In this case, either all steps of the method can be controlled, or all steps of the method can be carried out, or one or more steps can be controlled and one or more steps can be carried out. One or more of the means can also be executed and/or controlled by the same entity. For example, one or more of the means can be formed by one or more processors.

According to a third exemplary aspect of the invention, which is not the subject of the present claims, a system is disclosed which comprises one or more devices which are set up for executing and/or controlling the method according to the first aspect of the invention or means for executing and /or control the steps of the method according to the first aspect of the invention. Either all steps of the Method are controlled, or all steps of the method are executed, or one or more steps are controlled and one or more steps are executed.

These three aspects of the present invention include i.a. the properties described below, some of which are examples.

The term "expansion" is understood to mean a relaxation of natural gas, with the natural gas being at least under less pressure after the expansion than before the expansion.

The term "liquefied gas" is understood to mean in particular liquefied natural gas, also referred to as liquid natural gas (LNG). In particular, this does not include the so-called liquefied petroleum gas (LPG), which is often used by cars, for example. B. can be used as fuel by a corresponding conversion of the vehicle.

A “gas storage facility” is understood to mean a natural gas storage facility.

Such natural gas reservoirs are in particular large and, according to the invention, underground storage systems with which, for example, seasonal fluctuations in demand are possible by withdrawing natural gas previously stored in the reservoir.

The gas network is, for example, a transport network in which natural gas with a predefined pressure of z. B. is transported about 30 bar.

In a gas storage facility, there is in particular a sufficient pressure difference (differential pressure Δp; also referred to as delta p) between the natural gas that is stored in the gas storage facility and the gas network, into which the stored natural gas can be withdrawn from the gas storage facility, in order to generate liquid gas (LNG) in such gas storage facilities as part of the withdrawal.

In this way it is possible to produce liquid gas by means of gas expansion in a gas storage facility. Liquid gas produced can also be stored at least temporarily.

The amount of energy that was used to increase the pressure before storing natural gas in the gas storage facility (e.g. an underground storage facility designed as a cavern) is not completely lost when the gas is withdrawn into the gas network (e.g. transport network), since at carrying out the method according to the first aspect of the invention, this amount of energy is used or utilized for the production of liquid gas (LNG).

The generation of liquid gas, in particular by expanding natural gas that is stored in a gas storage facility, is based on the knowledge that the pressure difference, e.g. B. in caverns of large gas storage facilities or when outsourced to the transport network for the production of liquefied natural gas. A gas storage facility with, for example, two caverns with different pressures (e.g. 50 bar and 200 bar) or a cavern or storage facility in porous rock (e.g. 200 bar) with a connection to the natural gas transport network (e.g. 30-50 bar) can be used objectively, for example. During the expansion (ie relaxation) from one cavern to another or into the natural gas transport network, the Joule-Thompson effect can be used to generate cold and thus reduce the temperature of the natural gas. This resulting expansion energy is objectively at least partially used in the rearrangement or outsourcing of natural gas to produce liquefied natural gas (LNG). Since such a rearrangement and/or expansion into the transport network is carried out during regular operation of the gas storage facility, the liquefied gas can consequently be produced particularly cost-effectively.

The pressure reduction takes place in order to have a so-called constant system within the framework of the production of liquid gas, so that the method in which liquid gas is produced as a result can always be carried out with the one or more devices. The pressure reduction may be necessary, for example, because the prevailing pressure in the gas storage facility (e.g. cavern pressure) changes over the course of the year. This can happen, for example, as a result of external and naturally occurring environmental influences. In particular, gas reservoirs designed as cavern reservoirs are subject to such pressure fluctuations. The pressure reduction can be carried out, for example, by means of a pressure control valve, an expander, or a vortex tube, to name just a few non-limiting examples. The purification of the natural gas can include drying of the natural gas. Such drying of the natural gas changes the natural gas in such a way that water contained in the natural gas is sometimes removed from the natural gas. The natural gas can be cleaned and dried in a single step, for example. Alternatively, the cleaning and the drying of the natural gas can each be separate steps of the method according to the first aspect of the invention. Correspondingly, the cleaning and the drying of the natural gas can be carried out by a single device, or alternatively by two separate devices. In the event that the cleaning and the drying of the natural gas are carried out as separate steps, the order of the steps can be changed, for example. Accordingly, for example, the natural gas can be cleaned first and then dried. Alternatively, for example, the natural gas can be dried first and then cleaned.

The cleaning and/or drying of the natural gas stored in the gas reservoir includes or is carried out, for example, by systems that have components such as As water and carbon dioxide, which complicate the production of liquid gas, withdraw the natural gas. This enables stable subsequent production of the liquefied gas.

• Kühlen des gereinigten Erdgases zur Erzeugung des Flüssiggases, wobei das Kühlen des gereinigten Erdgases mittels eines ersten Wärmetauschers erfolgt und dabei kondensiert, und wobei ein erster Teil des gekühlten und kondensierten

According to a further embodiment according to the first aspect, the method also includes:

• Cooling of the cleaned natural gas to produce the liquid gas, the cooling of the cleaned natural gas taking place by means of a first heat exchanger and being condensed in the process, and a first part of the cooled and condensed

natural gas is passed to a second heat exchanger for cooling by heat exchanging a second portion of the cooled and condensed natural gas, the second portion being made into liquefied gas by subcooling in the second heat exchanger and subsequent expansion; and
wherein the cooling of the cleaned natural gas takes place in the first heat exchanger with an expanded part of the cleaned natural gas, the expansion taking place by means of a differential pressure which is applied when the natural gas stored in the gas reservoir is stored.

The cold is generated, for example, by means of pre-cooling and natural gas expansion. To produce the liquid gas, a differential pressure of at least 50 to 55, 51 to 54, 52 to 53, preferably at least 55 bar is required in order to be able to produce liquid gas particularly inexpensively with this method according to the first aspect of the invention. This differential pressure can be found in underground storage - as explained above.

The generation of the liquefied gas takes place, for example, in such a way that there is no negative impact on normal storage operation.

Apart from the footprint for the device or devices to be retrofitted (e.g.

systems and/or components), in contrast to conventional liquid gas production, there is no further landscape consumption.

With liquid gas generation in underground storage, an existing gas storage facility can take on new tasks in liquid gas generation in addition to its previous tasks in the gas network.

The expansion through which the liquefied gas is generated is such, for example, that the natural gas is cooled after the expansion in such a way that it is in its State of aggregation changes and accordingly changes from a gaseous state to a liquid state. This change of physical state, which is necessary for the production of liquid gas, takes place at a temperature of around -160°C. The cooling of the natural gas to reach this temperature takes place at least partially by means of the expansion. It is envisaged that this differential pressure will already arise when storing natural gas in the gas storage facility. By shifting the production of liquefied gas to a process of withdrawing natural gas from the gas storage facility, the energy already expended in order to be able to store natural gas compressed (i.e. reduced in volume) in the gas storage facility at a pressure that is higher than in the gas network can be used to produce liquefied gas be used. Otherwise, this energy would be wasted unused when natural gas is withdrawn from the gas storage facility as a result of the expansion of the natural gas to adjust the pressure that the natural gas has in the gas storage facility to the pressure of the gas network.

An embodiment according to the first aspect provides that the production of the liquefied gas is carried out essentially simultaneously with a withdrawal of natural gas stored in the gas storage facility.

The liquid gas is generated, for example, based on natural gas stored in the gas storage facility, which is intended to be released into the gas network, for example, to compensate for fluctuations in consumption in the gas network. The usual operation of the gas storage used to generate the liquid gas is consequently not disturbed.

A further configuration according to the first aspect provides that the liquefied gas is generated after passing through at least two heat exchangers, with a Joule-Thompson expansion of the natural gas being carried out in particular.

In particular, the liquid gas is generated by a total of two heat exchangers.

In Joule-Thompson expansion, the temperature of the natural gas used to produce liquefied petroleum gas changes as the pressure decreases. As a result, when the temperature falls below a predetermined level (about -160°C), the natural gas remains liquefied, which produces the liquid gas (LNG).

In one configuration according to all aspects, the liquid gas that is generated is stored at least temporarily in a liquid gas storage facility.

Liquid gas that is generated can in particular be stored at least temporarily. After this temporary storage, at least the boil-off gas (BOG) produced during storage must be removed from the storage facility. The BOG can be used to refuel CNG (Compressed Natural Gas) vehicles or fed back into the gas grid. Accordingly, liquid gas produced should be consumed continuously, since this same boil-off gas is produced during storage.

In a further embodiment according to the first aspect, the cold required to generate the liquefied gas is generated at least partially based on the natural gas that is to be stored on the one hand and is to be generated from the liquefied gas on the other.

Correspondingly, the cold required is at least partially also obtained based on the natural gas that is to be stored on the one hand and is to be generated from the liquid gas on the other (by a corresponding conversion of at least part of the second part of the cooled natural gas). Accordingly, the energy required for generation, which is required in particular for cooling the natural gas, is such that the natural gas changes its physical state from gaseous to liquid, as a result of which liquid gas is generated.

An embodiment according to the first aspect provides that the first part of the cooled natural gas can be discharged into a gas network after a pressure reduction. The reduction in pressure ensures in particular that cold occurs. This cold is used, for example, to produce liquid gas. A pressure reduction is also required in order to be able to withdraw natural gas that is stored in the gas storage facility into a pipeline of the gas network. The natural gas stored in the gas reservoir is brought to the pressure that is present in a gas network into which the natural gas is to be withdrawn, for example by the pressure reduction.

In one embodiment according to the first aspect, the storage of the liquefied gas produced causes a quantity of natural gas to escape (e.g. escape), the quantity of natural gas that emerges from the liquefied gas reservoir due to the heating of the stored liquefied gas being usable for further use.

When storing LPG, the temperature of the stored LPG increases. This increase in temperature of the stored liquefied gas leads to an escape of at least part of the stored liquefied gas, which is also referred to as so-called boil-off gas (BOG).

Instead of leaving this boil-off gas unused, for example by the boil-off gas deflagrating, it can be used for further use, for example.

This amount of natural gas that escapes (or evaporates) from a storage facility in which the generated liquid gas is stored can, for example, be subject to further use. For example, this vaporized natural gas can be discharged into the gas network after a pressure adjustment that is sometimes required (e.g. by compression). In this case, natural gas vaporized from a liquid gas storage facility generally has a lower pressure than the pressure that prevails in the gas network connected to the gas storage facility, which includes the liquid gas storage facility. Accordingly, it may be necessary to compress the natural gas in order to be able to withdraw this natural gas into the gas network.

Correspondingly, a further embodiment according to the first aspect provides that the quantity of natural gas can be fed (or is fed) to a third heat exchanger for heating natural gas for further use.

The third heat exchanger heats natural gas, for example, before the natural gas stored in the gas reservoir is withdrawn into the gas network or into a pipeline of the gas network. According to the third heat exchanger, for example, z. B. connected via an interface to the gas network or the pipeline of the gas network.

An embodiment according to the first aspect provides that a quantity of liquid gas can be used as fuel for further use.

For this purpose, for example, the amount of liquid gas in a corresponding (z. B. mobile) storage, z. B. in the manner of a tank, so that the amount of gasified liquid gas from this mobile tank can be fed to an engine as fuel to be needed. This amount can be used for vehicles (e.g. trucks, locomotives, ships, just to name a few non-limiting examples).

The boil-off gas can also be used, for example, as a fuel for transport.

Underground storage facilities, also referred to as underground gas storage (UGS], are gas storage facilities, whereby natural gas can be stored in natural or artificial cavities under the earth's surface using such underground storage facilities. Such gas storage facilities are, for example, aquifer and pore storage facilities, cavern storage facilities or tube storage facilities. Tubular storage facilities are medium-sized Natural gas storage to compensate for fluctuations in demand. Tube storage systems are used, for example, to cover daily consumption peaks, as they have high feed-in and feed-out capacities.

There is a sufficient pressure difference in the underground storage facility (between the natural gas that is stored in the underground storage facility and the gas network into which stored natural gas can be stored from the underground storage facility) in order to produce liquefied natural gas (LNG) in such gas storage facilities be able.

The one device or the multiple devices that carry out and/or control the method according to the first aspect are arranged within the gas storage facility, which is designed as an underground storage facility. The one device or the multiple devices are arranged, for example, between the interface via which the gas storage facility can withdraw stored natural gas (e.g. into a pipeline) and the interface via which natural gas stored in the gas storage facility can be withdrawn from the supply . Further details on this can be found in the "Detailed description of some exemplary embodiments of the invention" section.

A further configuration according to the first aspect provides that the cooling is carried out at least partially by cooling the natural gas using a refrigeration system.

In an embodiment according to the first aspect, the first part of the cooled natural gas is subjected to a pressure increase by means of a compressor.

In the event that a quantity of natural gas, at least partially based on which the production of liquid gas is carried out, has insufficient pressure to be discharged from the gas storage facility into the gas storage facility, the pressure of the natural gas can be increased by means of the compressor. A pressure that is too low can arise, for example, from the fact that during the evaporation of the liquid gas, during which the natural gas is heated (its temperature is increased by storage), it expands too much. This can be the case, for example, if the cold required to generate the liquid gas for cooling the natural gas could not yet be fully generated by expansion of the natural gas. Accordingly, in this case, a further expansion of the natural gas can take place in order to generate the cold required to produce the liquefied gas.

In a further configuration according to the first aspect, a fourth heat exchanger heats the first part of the cooled natural gas for compression by the compressor and/or for discharging the first part of the cooled natural gas into the gas network.

In particular, the pressure of the natural gas to the gas network or to a pipeline connected to the gas storage facility into which the natural gas is withdrawn can be increased, for example, by means of the fourth heat exchanger, the temperature of the natural gas to be withdrawn. This also indirectly causes a change in the pressure under which the natural gas is, so that the pressure of the natural gas to be withdrawn is or is subsequently adjusted to the pressure of the gas network or pipeline by heating.

One device is, for example, a single device. Alternatively, the method according to the first aspect of the invention is carried out and/or controlled by a plurality of devices (i.e. at least two devices, e.g. each designed as plant parts). One of the multiple devices is designed and/or includes such means, for example, to clean natural gas (e.g. natural gas cleaning system), and another device of the multiple devices is designed and/or includes such means, for example, to produce liquid gas (e.g B. a liquid gas production plant).

1. i) Einen oder mehrere Wärmetauscher;
2. ii) Einen oder mehrere Druckminderer;
3. iii) Einen oder mehrere Druckerhöher (z. B. Kompressor, oder ein Druckerhöher mit Kühler);
4. iv) Eine oder mehrere Kälteanlagen;
5. v) Eine oder mehrere Speicher zur Speicherung (z. B. Lagerung) von erzeugtem Flüssiggas;
6. vi) Eine oder mehrere Schnittstelle zur Ausspeicherung von während der Erzeugung des Flüssiggases verwendetem Erdgas in ein Gasnetz (z. B. Verteilnetz, und/oder Transportnetz);
7. vii) Einen oder mehrere Reinigungsanlagen; und
8. viii) eine oder mehrere Trocknungsanlagen

The device for generating liquid gas can include, for example, one or more of the following components i) to viii):

1. i) One or more heat exchangers;
2. ii) One or more pressure reducers;
3. iii) One or more boosters (e.g. compressor, or a booster with chiller);
4. iv) One or more refrigeration systems;
5. v) One or more reservoirs for storage (e.g. storage) of LPG produced;
6. vi) One or more interfaces for withdrawing natural gas used during the production of the liquid gas into a gas network (e.g. distribution network and/or transport network);
7. vii) One or more purification plants; and
8. viii) one or more drying plants

• Eine erste Druckreduzierung ist zu errichten oder eine vorhandene zu nutzen
• Eine Erdgasreinigungs- und eine optionale Trocknungsanlage, die z. B. von der Erdgasreinigungsanlage umfasst ist,] ist zu errichten;
• Eine Verflüssigungsanlage ist zu errichten;
• Ein Behälter für die Lagerung von LNG ist aufzustellen;
• Eine Abfüllanlage ist aufzubauen (der Einsatz einer mobilen LNG Tankstelle und/ oder CNG-Tankstelle ist optional möglich); und
• Schließlich sind Verrohrungen und Steuerung, auch der bestehenden Komponenten anzupassen.

A possible basic structure of a device for generating liquid gas in a gas storage facility designed as an underground storage facility can be designed as follows, for example:
To e.g. B. to fully upgrade the underground storage facility for the production of liquid gas, the following systems and components should be installed:

• A first pressure reduction is to be built or an existing one is to be used
• A natural gas cleaning and an optional drying system, which e.g. B. is covered by the natural gas cleaning plant,] is to be built;
• A liquefaction plant is to be built;
• A container for the storage of LNG is to be set up;
• A filling station is to be set up (the use of a mobile LNG filling station and/or CNG filling station is optionally possible); and
• Finally, the piping and controls must also be adapted to the existing components.

Accordingly, today's underground storage facilities, for example, already have at least part of the necessary infrastructure.

The exemplary configurations described above in this description should also be understood as disclosed in all combinations with one another. In particular, exemplary configurations are to be understood in relation to the different aspects disclosed.

In particular, the previous or following description of method steps according to preferred embodiments of a method should also disclose corresponding means for carrying out the method steps by preferred embodiments of a device. Likewise, the corresponding method step should also be disclosed through the disclosure of means of a device for carrying out a method step. Further advantageous exemplary configurations can be found in the following detailed description of some exemplary embodiments, in particular in connection with the figures. However, the figures are only intended to serve the purpose of clarification and not to determine the scope of protection. The figures are not to scale and are intended only to exemplify general concept. In particular, features included in the figures should by no means be considered a necessary part.

Brief description of the figures

Fig. 1

eine schematische Darstellung eines Ausführungsbeispiels eines Systems Z zur Durchführung des Verfahrens gemäß der Erfindung;

Fig. 2a,

b jeweils eine schematische Darstellung eines ersten Teils des gemäß Fig. 6 gezeigten Ausführungsbeispiels eines Systems zur Durchführung des Verfahrens gemäß der Erfindung;

Fig. 3

eine schematische Darstellung eines zweiten Teils des gemäß Fig. 6 gezeigten Ausführungsbeispiels eines Systems zur Durchführung des Verfahrens gemäß der Erfindung, welches basierend auf dem in Fig. 2 gezeigten Teils erweitert wurde;

Fig. 4

eine schematische Darstellung eines dritten Teils des gemäß Fig. 6 gezeigten Ausführungsbeispiels eines Systems zur Durchführung des Verfahrens gemäß der Erfindung, welches basierend auf dem in Fig. 3 gezeigten Teils erweitert wurde;

Fig. 5

eine schematische Darstellung eines vierten Teils des gemäß Fig. 6 gezeigten Ausführungsbeispiels eines Systems zur Durchführung des Verfahrens gemäß der Erfindung, welches basierend auf dem in Fig. 4 gezeigten Teils erweitert wurde;

Fig. 6

eine schematische Darstellung eines weiteren Ausführungsbeispiels eines Systems zur Durchführung des Verfahrens gemäß der Erfindung; und

Fig. 7

ein Flussdiagramm eines Ausführungsbeispiels eines Verfahrens gemäß der Erfindung.

In the drawing shows

1

a schematic representation of an embodiment of a system Z for carrying out the method according to the invention;

2a,

b in each case a schematic representation of a first part of according to 6 shown embodiment of a system for carrying out the method according to the invention;

3

a schematic representation of a second part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 2 part shown has been expanded;

4

a schematic representation of a third part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 3 part shown has been expanded;

figure 5

a schematic representation of a fourth part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 4 part shown has been expanded;

6

a schematic representation of a further embodiment of a system for carrying out the method according to the invention; and

7

a flowchart of an embodiment of a method according to the invention.

Detailed description of some exemplary embodiments of the invention

1 shows a schematic representation of an embodiment of a system for carrying out the method according to the invention.

The system 100 comprises a gas reservoir 110, a device for natural gas purification 120, a device for generating liquid gas 130, and an optional device for storing or storing the generated liquid gas 140.

The devices 120 and 130 comprised by the system 100 are in particular devices according to the second aspect of the present invention.

In exemplary embodiments of the invention, natural gas is withdrawn from gas storage 110 . The natural gas to be withdrawn is cleaned by the natural gas cleaning system 120 . On the basis of the cleaned natural gas, liquid gas is then generated by the device 130, the cleaned natural gas being cooled by supplying cold (cooling the cleaned natural gas), whereby the cleaned natural gas changes the aggregate state from gaseous to liquid, thereby producing liquid gas (LNG). will. The liquid gas produced can then optionally be stored or stored in a corresponding liquid gas storage facility. Natural gas, that was not used to produce LPG is fed into a gas network (in 1 not shown) with which the gas storage device 110 is connected. Alternatively, in an embodiment not according to the invention, the natural gas not used to generate liquid gas can be stored again in the gas reservoir 110 . For this purpose it may be necessary for the natural gas to be compressed for storage in the gas reservoir 110 .

6 shows a schematic representation of a further embodiment of a system for carrying out the method according to the invention.

The system 600 includes - analogous to the system 100 according to 1 - A gas storage 610 (here an underground storage, which is designed as a cavern with a pressure of about 85 to 200 bar), a device for natural gas purification and natural gas drying 620, and a device for generating liquid gas 630. The system 600 also includes a device for preheating natural gas and pressure reduction 615, a memory 640 for storing or storing the liquid gas produced, and a connection to a pipeline 650 of a gas network (z. B. a transport network). Before natural gas is withdrawn into the pipeline 650, a natural gas measurement can optionally be carried out by a corresponding device for natural gas measurement 660.

The device for generating liquid gas is encompassed by the gas reservoir 610 in such a way that liquid gas can be generated in particular as part of the withdrawal of natural gas stored in the gas reservoir 610 . For this purpose, the existing differential pressure between the natural gas stored in the gas storage facility 610 and the required pressure of the natural gas for withdrawal into the gas network or into the pipeline 650 of the gas network is used to supply cold to the natural gas via an expansion of the natural gas, so that as a result, liquefied natural gas (LNG) is produced.

The device 630 for generating liquid gas comprises five heat exchangers 630-1 to 630-5, a first Joule-Thompson expansion 630-8, a second Joule-Thompson expansion 630-9, a third Joule-Thompson expansion 630-10, a Refrigeration system 630-6, as well as a compressor 630-7.

The device for preheating 615 includes a heat exchanger by means of which the natural gas taken from the gas reservoir 610 is preheated. After preheating, a first Joule-Thompson expansion takes place, during which the pressure of the natural gas is reduced, e.g. B. from 200 bar in the stored state in the gas storage 610 to about 85 bar after performing the Joule-Thompson expansion.

The natural gas can then be cleaned in the device 620 for cleaning natural gas.

• Erdgasreinigung/Erdgastrocknung u. a. Wasserstoff und Kohlendioxid werden adsorbiert,

The following is carried out as part of the natural gas cleaning process:

• Natural gas purification/natural gas drying, including hydrogen and carbon dioxide, are adsorbed,

After the natural gas has been cleaned and dried 620, the natural gas (or the volume or mass flow of the natural gas) is divided, with a first part of the natural gas being routed to a heat exchanger 630-2 and a second part of the natural gas being routed to a heat exchanger 630-1 will. In this case, a larger proportion of the mass flow (e.g. 75%) of the natural gas is sent as the first part (to the heat exchanger 630-2), and a smaller proportion (e.g. 25%) as the second part (to the heat exchanger 630-1 ) divided The second part of the natural gas is cooled by means of the heat exchanger 630-1, the natural gas condensing a temperature after cooling. The refrigeration used by heat exchanger 630-1 to cool the second portion of the split natural gas is based at least in part on the first portion of the split natural gas.

The first portion of the split natural gas is pre-cooled by heat exchanger 630-2 and 630-4. That part of the natural gas from which the energy for cooling is obtained by the heat exchanger 630-2 or 630-4 can be routed via the natural gas measurement 660, for example, into the pipeline 650, since the energy required for cooling is generated by an expansion of the in the heat exchanger 630-2, as well as 630-4 introduced natural gas is related. The expansion means that the natural gas has a pressure of around 30 bar, for example, so that it can be fed into the pipeline.

In the 6 In addition, the mass flow m passing through the system 600 is indicated, which is initially generated by a pressure quantity control 615-3. The result is a mass flow m with constant pressure.

The mass flow m then runs through the natural gas cleaning system 620, which in the present case also performs natural gas drying.

This mass flow m is divided into the mass flows m1 (about 25% of the total mass flow m) and m2 (about 75% of the total mass flow m). The mass flow m2 serves as the first cooling for m1. The mass flow m2 is pre-cooled by the heat exchangers 630-2 and 630-4 and brought to a low temperature by a refrigeration system. Due to the subsequent natural gas expansion 630-9, the cooled natural gas is used to cool the mass flow m1 in the heat exchanger 630-1. Thereafter, the mass flow m2 is further heated via the heat exchanger 630 - 2 and conducted to the gas cleaning system in order to serve as regeneration in the natural gas cleaning system 620 . From there, the mass flow m2 is supplied to the gas network 650 via a natural gas measurement 660 .

The mass flow m1 cooled in the heat exchanger 630-1 condenses and is divided into the mass flows m3 (about 15% of the total mass flow m) and m4 (about 10% of the total mass flow m). The mass flow m4 continues to decrease cooled by expansion 630-10 and is used for the second cooling of the mass flow m3.

After being heated in the heat exchanger 630-3, the mass flow m4 is admixed with the BOG and heated via the heat exchanger 630-4 and brought to the required pipeline pressure by means of a compressor. From there, the mass flow m4 is fed to the gas network 650 via a natural gas measurement.

After cooling in the heat exchanger 630-3, the mass flow m3 is cooled down to the required liquid gas (LNG) temperature by the expansion 630-8 and then stored. The LNG can e.g. B. for LNG refueling, the BOG can be used for CNG refueling.

After passing through the heat exchanger 630-4, that part of the natural gas is further cooled by means of the refrigeration system 630-6, which obtains its energy for cooling, for example, from an external energy source (eg propylene). In the present case, this is carried out by means of the heat exchanger 630-5, which is connected to the refrigeration system 630-6. After expansion, this natural gas cooled in this way is introduced into the heat exchanger 630-1, as a result of which, as already explained above, the second part of the divided natural gas can be cooled.

In order to be able to reach the temperature of about -160°C required for the production of liquid gas (LNG) by cooling the natural gas, a Joule-Thompson expansion 630-10 takes place based on another part of the natural gas that has already passed through the heat exchanger 630-1 Has. The energy generated by this Joule-Thompson expansion 630-10 is used by the heat exchanger 630-3 to further cool the natural gas introduced into the heat exchanger 630-3. After passing through the heat exchanger 630-3, the natural gas usually does not yet have the temperature required for generating liquid gas (LNG), so that a further Joule-Thompson expansion 630-8 of the natural gas increases its temperature reduced in such a way that liquid gas is then generated. This generated liquid gas can be stored in the liquid gas store 640, for example.

Boil-off gas is produced during storage or storage of the liquid gas produced in the liquid gas storage facility 640 6 denoted by the abbreviation BOG. Once again 6 can be seen, this BOG can continue to be used; in the present case, for example, it can be introduced or fed into the pipeline 650 of the gas network after passing through the compressor 630-7.

• Nach der Erzeugung des Flüssiggases, wird das erzeugte Flüssiggas (LNG) gelagert. Diese Lagerung kann beispielsweise derart erfolgen, dass ein LKW bzw. ein entsprechend ausgebildeter und von dem LKW transportierter Behälter als Speicher genutzt wird. Derart kann das erzeugte Flüssiggas (LNG) transportiert werden, z. B. zur weiteren Verwendung. Der zum Transport verwendete Behälter muss dicht und isoliert sein. Der Behälter ist beispielsweise ein passiver Behälter, der also insbesondere keine aktive Kühlung des gespeicherten Flüssiggases durchführt. Dies ermöglicht insbesondere eine flexible Versorgung von diversen Kundengruppen.

The following is carried out as part of the production of the liquid gas:

• After the production of the liquid gas, the produced liquid gas (LNG) is stored. This storage can, for example, take place in such a way that a truck or a correspondingly designed container transported by the truck is used as storage. In this way, the liquid gas (LNG) produced can be transported, e.g. B. for further use. The container used for transport must be tight and insulated. The container is, for example, a passive container, which in particular does not carry out any active cooling of the stored liquid gas. In particular, this enables a flexible supply of various customer groups.

For the production of liquefied gas (LNG production), refrigeration is required in particular, with around 85% of the natural gas, for example, on which the production of liquefied gas is based, being used for the production of refrigeration. The remaining approximately 15% (25% divided into 10% and 15%) of the natural gas is converted into liquefied gas. It is particularly advantageous that the natural gas quantities used for cold production (e.g. the approximately 85%) are not lost, but are used further because these are stored in the gas network after the cold production, for example. From there, the natural gas can, for example, be stored again in the gas storage facility from which the natural gas used to generate the liquid gas was originally stored.

The prevailing temperatures and pressures of the natural gas that it has after passing through a device (610 to 660) included in the system can 6 in each case by a corresponding indication attached to the respective device in 6 is shown, can be removed. These details of temperatures and pressures are also to be understood as disclosed in connection with all aspects of the present invention.

The in the Figures 2a to 5 Reference numbers used correspond to those in FIG 6 used reference symbols. It is understood that this is not limiting to the subject matter Figures 2a to 5 shown and by the respective systems according to the Figures 2a to 5 Entities used (z. B. preheating 615, natural gas cleaning and drying 620, liquefied gas production 630) can each both with each other according to the Figures 2a to 5 as well as from the entities of 6 be independent. The in the 2a to 6 Schematically represented entities can be the same, for example, and accordingly not be the same.

Figure 2a shows a schematic representation of a first part of the 6 shown embodiment of a system according to the invention. Figure 2b shows the according Figure 2a shown part of the system, being opposite Figure 2a after the pressure reduction, a heat exchanger is arranged, which uses at least part of the gas before the pressure reduction for the corresponding heat exchange.

Two pressure reductions are provided in the withdrawal line. The first serves to generate a constant mass flow. After the natural gas has been cleaned and dried, the pressure is reduced a second time, during which cold is produced as a result of relaxation (expansion).

Opposite to Figure 2a is in Figure 2b a second mass flow is available, which is derived after cleaning and cooled and condensed via a heat exchanger.

3 shows a schematic representation of a second part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 2 part shown has been expanded.

After cooling and condensation (cf. Figure 2b ) divided again, whereby the derived mass flow is further cooled by a third pressure reduction.

This in turn creates cold, which is exchanged via a heat exchanger that is intended to generate the liquid gas (LNG). The mass flow is then routed through another heat exchanger, which serves as pre-cooling for the mass flow in the withdrawal line. This mass flow is brought back to pipeline pressure via a compressor

4 shows a schematic representation of a third part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 3 part shown has been expanded.

The mass flow condensed by the second derived mass flow is then expanded via a fourth pressure reduction. The resulting cold of -160 °C is reached and liquid gas (LNG) can then be stored.

The BOG can e.g. B. be used for CNG refueling or stored back in the gas storage.

figure 5 shows a schematic representation of a fourth part of the 6 shown embodiment of a system for performing the method according to the invention, which is based on in 4 part shown has been expanded.

In order to be able to start up liquid gas production and keep it stable, a refrigeration system is provided in the withdrawal line. This refrigeration system can also Application of energy sometimes necessary to start the method according to the first aspect of the invention, which is carried out by the system 600.

7 shows a flow chart of an embodiment of a part of the method according to the invention. Flowchart 700 is performed by devices 120 and 130, for example 1 carried out and/or controlled.

In a first step 701, cleaning takes place in a gas storage facility (e.g. a gas storage facility designed as an underground storage facility, e.g. gas storage facility 110 according to 1 , stored natural gas.

In a second step 702, liquid gas is generated based on the cleaned natural gas. Liquid gas can be generated, for example, by means of the device for generating liquid gas 130 1 carried out and/or controlled. The liquid gas is generated as part of the withdrawal of natural gas stored in the gas storage facility into a gas network connected to the gas storage facility, with the withdrawal covering, for example, a corresponding requirement of the gas network. An expansion of the natural gas stored in the gas reservoir is required for withdrawal, the pressure of the natural gas stored in the gas reservoir being reduced. In the present case, this is used to use at least part of the natural gas stored in the gas reservoir to produce liquid gas.

In an optional third step 703, the liquid gas produced is stored, e.g. B. a storage of the liquid gas in a separate memory, which is for example included in the gas storage. Alternatively or additionally, the generated liquid gas or at least part of the generated liquid gas can be stored or stored in a container that is transportable. The transportable container can be transported, for example, by means of a truck or a train.

The exemplary embodiments of the present invention described in this specification and the optional features and properties listed in each case in this regard should also be understood to be disclosed in all combinations with one another. In particular, the description of a feature included in an exemplary embodiment - unless explicitly stated to the contrary - should not be understood in the present case in such a way that the feature is essential or essential for the function of the exemplary embodiment. The procedural steps can be implemented in different ways, so an implementation in software (by program instructions), hardware or a combination of both for the implementation of the procedural steps is conceivable.

Terms used in the claims such as "comprise", "have", "include", "contain" and the like do not exclude further elements or steps. The phrase "at least partially" includes both the case "partly" and the case "completely". The phrase "and/or" should be understood to mean that both the alternative and the combination should be disclosed, i.e. "A and/or B" means "(A) or (B) or (A and B)". The use of the indefinite article does not exclude a plural. A single device can perform the functions of several units or devices mentioned in the claims. Reference signs given in the patent claims are not to be regarded as limitations on the means and steps used.

Claims (11)

1. Method for a production of liquefied gas, performed by one or more apparatuses (110, 120, 130, 610, 620, 630), comprising:

   - reducing a pressure of natural gas stored in a gas storage (110, 610), , wherein after the reduction the natural gas has a predetermined constant pressure;

   - purifying natural gas stored and expanded in the gas storage (110, 610); and

   - producing liquefied gas based on the purified natural gas, wherein the producing of the liquefied gas is performed during the outputting of the natural gas out of the gas storage (110, 610) into a gas network (650) connected to the gas storage (110, 610), and

   the gas storage (110, 610) is an underground gas storage,

   wherein the one or more apparatuses (110, 120, 130, 610, 620, 630) for performing and/or controlling the method are configured or comprise respective means for performing and/or controlling the steps of the method,

   characterized in that the one or more apparautses performing and/or controlling the method are located within the underground gas storage tank (110, 610).
2. The method of claim 1, further comprising:

   - cooling the purified natural gas to produce the liquefied gas, wherein the cooling of the purified natural gas (m1) is effected by means of a first heat exchanger (630-1) and thereby condenses, and wherein a first part of the cooled and condensed natural gas is passed to a second heat exchanger (630-3)for cooling by means of a heat exchange of a second part of the cooled and condensed natural gas, wherein from the second part by supercooling in the second heat exchanger (630-3) and subsequent expansion the liquidized gas is produced; and
   wherein the cooling of the purified natural gas (m1) in the first heat exchanger (6301) is performed with an expanded part of the purified natural gas, wherein the expansion (630-8) is performed by means of a differential pressure applied when the natural gas stored in the gas storage (110, 610) is injected.
3. The method according to claim 2, wherein the producing of the liquefied gas is substantially simultaneous with an outputting of liquefied gas stored in the gas storage (110, 610) performed.
4. The method according to any one of claims 2 to 3, wherein the liquefied gas is produced after passing through at least two heat exchangers (630-1, 630-3), wherein in particular a Joule-Thompson expansion (630-10) of the natural gas is performed.
5. The method according to any one of claims 2 to 4, wherein the generated liquified gas is at least temporarily stored in a liquefied gas storage (140,640).
6. The method according to any one of claims 2 to 5, wherein for producing the The coldness required for the producing of the liquefied gas is based at least in part on the one hand on the natural gas to be outputted and on the other hand on which the liquefied gas it to be produced.
7. The method according to any one of claims 3 to 6, wherein the first part (m1) of the cooled natural gas is withdrawable into a gas network (650) after a pressure reduction (630-8).
8. The method according to any one of claims 5 to 7, wherein the storing of the generated liquefied gas causes a leakage of a quantity of natural gas, whereby the amount of natural gas that leaks from the liquefied gas storage (140, 640) due to heating of the stored liquefied gas is usable for further purposes.
9. The method according to claim 8, wherein the amount of natural gas for further use is fedable to a third heat exchanger (630-4) for heating natural gas.
10. The method according to any one of claims 2 to 9, wherein the cooling is performed at least in part by cooling the natural gas by a cooling system (630-6).
11. The method according to any one of claims 3 to 10, wherein the first part (m1) of the cooled natural gas is subjected to a pressure increase by means of a compressor (630-7).

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