WO2008017470A1

WO2008017470A1 - Method and system for the vaporization of liquefied natural gas and expansion of natural gas

Info

Publication number: WO2008017470A1
Application number: PCT/EP2007/007018
Authority: WO
Inventors: Hartmut Griepentrog
Original assignee: Hartmut Griepentrog
Priority date: 2006-08-08
Filing date: 2007-08-08
Publication date: 2008-02-14
Also published as: DE102006046246A1

Abstract

The invention relates to a method and a system for the vaporization and/or the expansion of natural gas. The natural gas is vaporized in a heat exchanger at an increased pressure as opposed to the delivery pressure, and subsequently expanded by means of an expansion machine. This allows for a particularly effective heat exchange, and optimized energy utilization. As an alternative, or in addition, the natural gas is isochorically condensed by means of a heat supply to a pressure above the delivery pressure and is subsequently expanded for creating mechanical energy.

Description

Process and plant for vaporizing liquefied natural gas and

Relaxing natural gas

The present invention relates to a method for expanding gas, in particular natural gas, to a desired discharge pressure, in particular for a gas supply device and / or for evaporating liquid gas, in particular liquefied natural gas, and such systems.

Liquefied natural gas is supplied, for example, by tankers or in any other form. For feeding into a gas supply device, such as a storage or a pipeline, the liquid gas must be evaporated. For evaporation further energy expenditure is necessary.

From US Pat. No. 4,231,226 A, US Pat. No. 6,367,258 B1 and US 2006/0080963 A1 it is known in each case to supply the required energy or heat to the gas to be evaporated via a heat exchanger, usually called a heat exchanger, the required heat being supplied by a gas turbine plant is, whereby their efficiency is increased.

US 3,367,258 Bl describes that there are basically two options if the gas is to be compressed to a certain pressure. In low pressure evaporation, the liquid gas is first vaporized and then compressed to the desired pressure. In high pressure evaporation, the liquid gas is compressed to the desired pressure - for example, in two stages to about 3.5 MPa or more - and then vaporized and heated to about 4 ° C. This probably corresponds to the discharge pressure or required pressure for other applications.

US Pat. Nos. 6,739,140 B2, 6,813,893 B2, 6,848,502 B2, 6,880,348 B2, 6,945,055 B2, US Pat. No. 7,036,325 B2, US 2006/0150640 A1, WO 03/054440 A1 and WO 2004/081441 A1 are concerned with the storage of liquefied natural gas in salt caverns, wherein the liquid gas is first brought to the usual or required for storage in the salt caverns pressure of, for example, about 16 MPa and heated at least substantially to the prevailing temperature before being introduced into the salt caverns. In Germany, gas supply facilities, which store or provide the gas in gaseous form and in particular serve the general gas supply, usually operate with a supply or gas pressure of about 8 MPa. Typically, the discharge pressure at which the vaporized gas is delivered to a gas supply device corresponds to this supply pressure. Usually, a storage with more than

8 MPa. This storage pressure is then lowered for end users in several stages, in particular to a final discharge pressure of about 105 kPa.

Planning of the gas supply envisage storing the gas in caverns before discharge into a gas supply device in order to compensate for fluctuations in acceptance. For a significantly higher gas pressure of 27 MPa, for example, is provided.

The present invention has for its object to provide an improved method and an improved system for relaxing gas, especially natural gas, to a desired discharge pressure and / or evaporation of liquid gas, in particular liquefied natural gas, with a higher efficiency or energy utilization and / or an improved heat transfer is enabled or become.

The above object is achieved by a method according to claim 1, 3 or 23 or by a system according to claim 24, 25 or 28. Advantageous developments are the subject of the dependent claims.

A first aspect of the present invention is first to compress the gas to an elevated pressure which is well above the discharge pressure and / or at least 15 or 18 MPa. The compaction is carried out by at least substantially isochoric heat. In particular, the gas in the gaseous state - in particular after evaporation or after removal from a store o. The like. - Compressed starting from an initial pressure then present on the increased pressure. This compression is preferably isochoric by means of a corresponding heat exchanger. Subsequently, the relaxation takes place on the opposite to the initial pressure optionally higher or lower discharge pressure, in particular mechanical energy is generated by means of an expansion machine. This allows a very energy-efficient release of the gas.

Alternatively, compression to the increased pressure may also be accomplished by a compressor or the like.

Another aspect of the present invention is to first compress the (liquid) gas to the elevated pressure, which is well above the discharge pressure and / or at least 15 or 18 MPa, and then evaporate by supplying heat. Due to the increased pressure - at least in the relevant temperature range from about 110 K to room temperature or above - in contrast to the usual lower pressures - in the (gas to be liquefied) a quasi-ideal gas behavior or an at least substantially constant specific heat capacity c _p - specific heat capacity at constant pressure - reached. This allows a significant improvement in the supply of heat or the so-called heat exchange through a heat exchanger (heat exchanger) and accordingly allows a more effective use of energy.

Another aspect of the present invention is to relax the vaporized and heated gas from the increased pressure back to the desired delivery pressure. In particular, the relaxation by means of an expansion machine, z. Example, via a displacement machine, a turbine or a reciprocating engine, so that mechanical energy for operating a work machine, such as an electric generator, can be generated. This in turn allows optimized energy utilization.

Particularly noteworthy is that when relaxing on the lower discharge pressure of less than 10 MPa in particular, the behavior of the gas as a non-ideal - ie as a real - gas leads to a significant increase in the available or producible energy.

Particularly preferably, the (to be liquefied) gas is not only compressed to the increased pressure, but also heated to a relation to the desired discharge temperature of, for example, about 275 to 280 K significantly elevated temperature and then during or by the relaxation so-. - A -

probably brought to the desired discharge pressure as well as the desired discharge temperature.

Further aspects, advantages, properties and features of the present invention will become apparent from the claims and the following explanation of preferred embodiments with reference to the drawing. It shows:

Fig. 1 is a schematic view of a proposed system according to a first embodiment;

Fig. 2 is a schematic enthalpy diagram of natural gas;

3 shows a schematic T-s diagram of a first method sequence;

4 is a schematic view of a proposed plant according to a second embodiment;

5 shows a schematic T-s diagram of a second method sequence; and

6 is a schematic T-s diagram of a third method sequence.

The present invention is particularly concerned with the vaporization of liquid gas, in particular liquefied natural gas. The following is therefore always spoken of natural gas. However, it may also be any other liquid or liquefied gas, such as so-called liquid gas (propane, butane or a mixture thereof) or LPG (Liquified Petrolium Gas) or the like act. The present invention is alternatively or additionally concerned with the venting of gas, especially natural gas. However, this may also be other gas, in particular in the aforementioned sense or air act.

1 shows, in a merely schematic, block diagram-like representation, a proposed system 1 for the evaporation of liquid natural gas according to a first embodiment. The system 1 has a connection or inlet 2 or the like for receiving the liquid natural gas, not shown, for example, from a tanker, storage, or the like, not shown. The pressure at the inlet 2 is for example about 1.1 MPa, the temperature for example about 1 13 K.

Subsequently, the liquid natural gas is compressed to an elevated pressure. For this purpose, the system 1 preferably has at least one pump 3, optionally a further pump 4. The compression or pumping or pressurization of the liquid natural gas takes place in the illustration example in one stage or, if necessary, in several stages.

The increased pressure of the natural gas is preferably at least 18 MPa, in particular at least 20 MPa, more preferably substantially 24 MPa or more, in the illustrated embodiment about 27 MPa.

The increased pressure is preferably more than 5 MPa, in particular more than 10 MPa, above a discharge pressure of the system 1 to a gas supply device G only, which is connected via a connection or outlet 5 to the system 1 and, for example, a non-illustrated Memory or a pipeline, not shown, may have for the evaporated natural gas. However, also a delivery with the final pressure to a gas supply device G of an end user can take place.

The increased pressure is preferably chosen such that the natural gas at the elevated pressure has an at least substantially independent of the temperature specific heat capacity c _p . This applies at least for the relevant temperature range of, for example, 113 K to about 275 K or above.

The schematic diagram of Figure 2 illustrates schematically the dependence of the enthalpy H on the temperature T and the pressure p. Here, the x-axis shows the enthalpy increase H without a unit, since this is not about the absolute value, but only about relative values for illustration. The y-axis shows the temperature in Kelvin. The individual curves represent are different isobars whose values are given in the legend in MPa. The derivative or slope of the enthalpy curves corresponds to the specific heat capacity, more precisely the specific heat capacity at constant pressure. The curves represent the course at different pressures.

It can be seen from FIG. 2 that the enthalpy curve approaches a straight line only at the elevated pressure, that is, the specific heat capacity is at least substantially constant. Accordingly, the increased pressure should preferably be at least 15 MPa in order to achieve an at least substantially constant specific heat capacity of the natural gas.

The liquid natural gas is still liquid after compression or pressurization. Even if the temperature has slightly increased as a result and / or by other influences, for example, about 120 to 160 K.

Subsequently, the liquid natural gas is evaporated by supplying heat. In the system 1 shown in FIG. 1, this is preferably carried out in a heat exchanger 6 located downstream of the pump 3 or 4. The heat supply or the heat exchange and the evaporation preferably take place at substantially constant pressure (isobaric), ie at the elevated pressure of the initially still liquid natural gas. The evaporation takes place in particular within the heat exchanger 6.

It should be noted that due to flow resistance, turbulence, fluctuations or the like, certain pressure losses or pressure fluctuations may occur. Accordingly, the initially still liquid natural gas can be compressed, for example, by the pumps 3, 4 to a pressure somewhat above the elevated pressure and / or the pressure of the natural gas in the heat exchanger 6 can vary somewhat due to the evaporation process.

The heat supply for heating and evaporation of the natural gas can generally be done in any way. For example, as known in the art, marine heat or a so-called immersion flame evaporator, open-rack evaporator or the like may be employed. The "cold energy" may also be used, for example, in the chemical or food industry or the like.

Particularly preferably, the heat is supplied by a thermal power plant 7, for example with a turbine, as indicated in Figure 1. As a power plant 7 in the context of the present invention, in particular a gas turbine plant, steam turbine plant and / or combined gas and steam turbine plant or the like is to be understood. Such a turbine system is used in particular for the generation of electrical and / or mechanical energy. The turbine system can be operated with an open or closed circuit, wherein the medium for the heat transfer to the natural gas to be vaporized or to be heated can be liquid and / or gaseous.

The heat supply to evaporate the natural gas or the heat exchanger 6 leads particularly preferably to a cooling of said and / or other medium of the power plant 7, for example, intake air to a lowering of the condenser temperature of a combined cycle power plant or the like. In particular, the potential or actual efficiency of the power plant 7 can thus be increased.

With regard to the possible applications or coupling of the heat exchanger 6 or even more such heat exchangers at or with the power plant 7, in particular a gas turbine, reference is made to US 4,231,226 A, US 6,367,258 Bl and US 2006/0080963 Al, the hereby hereby as a supplementary disclosure be called and introduced.

In the first embodiment, only a single heat exchanger 6 is provided to evaporate the still liquid natural gas and heated to a desired, in particular elevated temperature. The evaporation and in particular also heating are thus preferably carried out in one stage. However, this does not rule out that several heat exchangers 6 are connected in parallel or work to achieve a desired throughput. Even if several heat exchangers 6 are connected in series, the evaporation of the natural gas preferably takes place only in one, in particular in the first heat exchanger 6.

In the illustrated embodiment, the vaporized natural gas - in particular directly in the heat exchanger 6 - to a relation to the discharge temperature at the terminal or outlet 5, for example, about 273 to 285 K increased temperature, preferably to more than 300 K, in particular more than 340 K, more preferably in substantial 360 K or more, heated.

As already mentioned, the increased pressure results in a specific heat capacity of the natural gas which is essentially independent of the temperature or constant. In order to achieve a particularly effective heat transfer, the heat is supplied by a warmer medium (in particular in the heat exchanger 6 and particularly preferably by the power plant 7), which preferably also has a substantially independent of the temperature or constant specific heat capacity and / or is preferably liquid.

Particularly preferably, the heat for evaporating the liquid natural gas is completely supplied or provided by the power plant 7. However, it is also possible in principle to supply or provide additional heat in addition or in addition or alternatively in another way.

The vaporized natural gas is then relieved of the increased pressure, in particular to the discharge pressure of preferably at most 22 or 10 MPa, in particular substantially 8 to 8.5 MPa or less, or even to the ultimate pressure of, for example, about 105 kPa. In particular, the delivery pressure may be at least substantially equal to the output pressure - here, the liquid natural gas - above (which is often the case), below, or even equal to the final delivery pressure.

Particularly preferably, the expansion takes place in a single-stage or multi-stage expansion machine 8. In the illustrated example, the expansion machine 8 has a displacement machine or reciprocating piston engine, preferably a turbine 9, in which the natural gas is supplied from the increased pressure. At least substantially relaxed to the discharge pressure. Particularly preferably, the expansion machine 8 or turbine 9 drives a working machine, in this case a generator 10, to generate electricity, as indicated in FIG. However, the expansion machine 8 or turbine 9 can alternatively or additionally also be used for other purposes, for example for generating mechanical energy. According to an embodiment variant, not shown, the turbine 9 may also form part of the power plant 7 or be coupled or combined in any other way with this.

When or by the expansion, the gas cools, preferably to about or below 300 K, more preferably at least substantially to the desired discharge temperature.

To control or regulate the delivery pressure, the system 1 can be provided on the delivery side with a pressure control or regulation, which is not shown, or the like. This can also be done by appropriate control of the expansion machine 8 or turbine 9.

Further, if required, cooling and / or heating of the natural gas after relaxing to the desired discharge temperature - for example by means of an optional (further) heat exchanger 11, as indicated in Figure 1 - take place. In this case, the natural gas is heated in the first heat exchanger 6, for example, only to a lower temperature and / or cooled in the expansion machine 8 below the discharge temperature.

If necessary, the additional heat exchanger 11 can in turn be coupled to the power plant 7 or receive its heat from it. However, other technical solutions are possible, as already generally addressed for the supply of heat for the evaporation of natural gas.

If required, the power plant 7 can form part of the plant 1 or be designed as a separate plant or separately therefrom.

The proposed Appendix 1 allows a particularly efficient evaporation and / or good energy utilization. Bills have shown that in Combined with a gas turbine plant or the like a high efficiency and energy yield can be achieved.

The schematic Ts diagram according to FIG. 3 explains a preferred first workflow or method sequence in the illustration example. The x-axis gives the specific entropy s in kJ ^• kg ^{'1 •} K ^{' 1} . The y-axis indicates the temperature in K. The lines represent isochores and isobars with different values according to the legend.

In the first method sequence, the liquid natural gas is initially compressed starting from point A (eg T = 113 K, p = 1.1 MPa) according to arrow Pl to the increased pressure of, for example, 27 MPa, that is to state B The compression can be effected in particular by means of the pump 3 and / or at least substantially adiabatically. The compression thus takes place in particular not along an Isochoren 12, even if this looks like in the illustration of FIG. 3, but z. B. along a polytropic. In state B, the temperature of the still liquid gas has already increased somewhat, for example to about 120 to 130 K.

Starting from the state B then takes place a heat supply by means of the heat exchanger 6. As a result, the first still liquid gas changes its state, in particular at least substantially along an isobaric 13 (ie while maintaining its pressure) until the state C is reached. During this heat supply, the initially still liquid gas is evaporated and is then in gaseous form with the increased pressure and the elevated temperature of, for example, about 360 K. The transition from the liquid to the gaseous phase preferably takes place in a single step or in a single heat exchanger 6. If desired, the heating from state B to state C can take place via other intermediate states and / or also in several stages. In state C, the natural gas is completely vaporized and in particular heated to the elevated temperature of, for example, about 360K.

Subsequently, the natural gas is expanded, as indicated by arrow P2. The natural gas then takes in particular the delivery state D with the desired discharge pressure and in particular the desired discharge temperature, here for example T = 300 K, p = 8 MPa.

Due to the deviation of the natural gas from an ideal gas or due to the real gas effect or the non-parallel isobars 13 and 14 or the pressure-dependent change in the heat capacity (decrease in heat capacity c _p with decreasing pressure) can relax when relaxing - So transition from the state C in the state D - additional or more energy are released, as would be the case with an ideal gas - ie in close-lying or parallel isobars 13 and 14.

The natural gas can also be expanded in multiple stages with multi-stage intermediate heating, which can take place along an isobar and / or isochores, in order to keep the temperature in front of the expansion machine and a given discharge temperature low.

Hereinafter, a second embodiment of the proposed Appendix 1 and in particular also a second method will be explained with reference to Figures 4 and 5, wherein in particular only significant differences compared to the first embodiment will be explained. The previous explanations and remarks apply in particular corresponding or supplementary.

The system 1 has only optionally a pump 3 o. The like. In the second embodiment.

In addition to the (first) heat exchanger 6, the plant 1 preferably has a second, downstream heat exchanger 6 'for supplying heat. This heat supply can in principle be done in any way. However, particularly preferably, the heat is again supplied by a thermal power plant T, in particular a turbine, as indicated in FIG. The relevant explanations in the first embodiment apply in particular supplementary. If necessary, the further power plant 7 * can also be coupled to the first power plant 7 or formed by it. In the second embodiment, the heating of the natural gas in the first heat exchanger 6 is preferably at least substantially at constant pressure, ie isobaric. The transition from the liquid to the gaseous phase of the natural gas is preferably carried out in the first heat exchanger 6.

The second heat exchanger 6 ¹ is preferably designed such that an at least substantially isochronous heating, in particular therefore at least substantially at constant volume, of the natural gas takes place. Thus, the compression is at least substantially isochoric for at least a portion of the pressure increase.

The T-s diagram according to FIG. 5 shows, by way of example, a second method sequence, which can be implemented, in particular, with the proposed system 1 according to the second embodiment.

Based on the pressure and the temperature at the inlet 2 (for example, T = 113 K and p = 9.5 MPa - state A in Figure 5), the liquid natural gas in the first heat exchanger 6 at least substantially at constant pressure - namely at least substantially along Isobaric 13 - heated and evaporated. However, at least also a compression to a desired pressure, for example 7 to 10 MPa or more, in particular by the optional pump 3, take place.

FIG. 5 then shows the transition from state A to state B according to arrow Pia. For example, in this first step of the heat supply, a heating to more than 200 K, in particular substantially 210 K. The heat can be at a pressure of for example about 7 to 10 MPa, in particular substantially 9 to 10 MPa.

Subsequently, a second heat supply takes place to further heat the already gaseous natural gas and to increase its pressure. This heat is at least substantially isochoric - that is, at least substantially at constant volume - in the second heat exchanger 6 '. Here, the state of the gas changes from B to C according to arrow PIb. The heating thus takes place at least substantially along the isochores 12 (line of constant density) in FIG. 5. The second or at least substantially isochoric working heat exchanger 6 'operates particularly preferably discontinuously so in so-called batch mode. Here, the natural gas to be heated is heated in batches at constant volume by supplying heat, whereby the pressure of the respective charge of the natural gas is increased accordingly. So can be done in a very efficient way at least substantially isochoric heating of the natural gas.

In the state C - ie in particular after the isochoric heat supply - the increased pressure and the elevated temperature of the natural gas are achieved, in the illustrated embodiment about 60 MPa and about 360 K. However, other increased values can be achieved here, in particular initially in connection with the first embodiment explained.

Subsequently, the relaxation of C in the delivery state D according to arrow P2 is carried out in particular according to the first embodiment.

In principle, the particular isochoric heat supply or heating of the natural gas can, if necessary, also take place in a plurality of steps or stages, if appropriate with a plurality of second heat exchangers 6 'or in any other suitable manner. Also, an alternating heating and relaxing can be done several times.

According to a further, not shown embodiment variant, the following procedure is possible. Starting from the initial state with, for example, about 113 K and a pressure of about 8.2 MPa, the liquid natural gas is first compressed, for example by means of the pump 3, to a pressure of, for example, about 9.54 MPa. In this case, the temperature may increase slightly, for example to about 113.8 K.

Subsequently, the liquid natural gas in the first heat exchanger 6 and under at least substantially isobaric conditions - ie at least at substantially constant pressure - heated to about 210 K and thereby evaporated. This is followed by a first at least substantially isochoric further heating - for example, in the second heat exchanger 6 '- on. In this case, the temperature can be raised, for example, to about 280 K and the pressure increased to about 33.2 MPa.

This is followed by a first relaxation, for example via a first expansion machine, such as the turbine 9. In this case, the pressure is lowered, for example, to 8 MPa, the temperature of the gaseous natural gas thereby falling to about 241 K.

Subsequently, a further or second, at least substantially isochoric preheating - for example, in a third heat exchanger, not shown - to eg 280 K and a pressure of about 1.15 MPa.

There is then another or second relaxation - preferably again by means of an expansion machine, such as another turbine 9 - to 8 MPa, for example, with the temperature of the natural gas thereby reduced to about 268, 1 K. For example, the desired discharge pressure of about 8 MPa can be achieved.

Finally, preferably another, now in particular isobaric heat supply takes place - for example, again by means of a further heat exchanger 6 - to finally heat the natural gas to the desired discharge temperature of, for example, about 275 K.

Fig. 6 shows in a very schematic Ts-diagram (the x-axis is to denote the specific entropy s, but units have been omitted) a third proposed procedure. Here, a relaxation of the already gaseous natural gas from an initial pressure to the lower discharge pressure in particular for the delivery of natural gas to a gas supply device G in the aforementioned sense. The proposed relaxation can be carried out in particular after a proposed liquefaction of the natural gas or after another liquefaction of the natural gas or independently. In particular, the proposed relaxation of natural gas, for example, can be used to the natural gas of the usual accumulator pressure of about 8.0 MPa as the initial pressure to the usual final discharge pressure of about 105 kPa as discharge pressure to relax.

The proposed relaxation can be carried out in particular with the system 1 (FIG. 4) without the first heat exchanger 6. The relevant explanations therefore apply in particular in addition or correspondingly.

FIG. 6 illustrates that the natural gas to be expanded is heated isochorally, starting from state B (for example about 8 MPa or more and for example 275 to 300 K or less) at least substantially along the isochores 12, ie according to arrow Pl. The heat supply to this preheating can in turn preferably be provided by the power plant 7 or 7 'or other means available. In the heated state C, the natural gas then preferably again has the increased pressure and the elevated temperature in the sense already mentioned.

Subsequently, the relaxation takes place in accordance with arrow P2 from state C to the discharge state D of the natural gas. In this case, mechanical energy can again preferably be obtained, for example by means of the expansion machine 8.

The proposed relaxation can also take place in several stages and / or with alternating preheating and relaxation.

The proposed relaxation can be used in particular with the required reduction of the usual gas supply pressure of, for example, about 8 MPa to the usual final discharge pressure of for example about 105 kPa. For example, a corresponding power plant or turbine plant can be combined with the proposed plant 1 for relaxing. Such a combination plant can then be used in particular locally or decentralized, for example, to relax natural gas from the usual storage or remote supply pressure to the final discharge pressure.

In general, it should be noted that the pressure of the liquefied natural gas is brought to a level prior to entering the evaporator or heat exchanger, which ensures the most constant specific heat capacity at constant pressure during preheating to give a favorable evaporator or heat exchanger design with the same temperature difference between the evaporating natural gas and the heat-bonded or heat-introducing medium at the inlet and outlet as possible.

The relaxation of the natural gas can, as already mentioned, multi-stage, possibly with an intermediate heating, take place.

To relax on the desired discharge pressure, if necessary, a throttle or control valve - especially in combination with the expansion machine before or after - be used.

In general, it should be noted that between the pressure increase and heating on the one hand and the relaxation on the other hand particularly preferably no (relevant) intermediate storage takes place, but that this is particularly preferably done immediately after one another or in succession.

In the present invention, the liquid natural gas is preferably vaporized at said high pressures. There is a possibility that at these high pressures no clear distinction between a liquid phase and a gas phase is possible. In this case, the term "evaporate" or "evaporate" is preferably to be understood in the present invention that at the lower pressure temperature the natural gas would be in gaseous form.

As already explained, the proposed plants 1 and / or processes can be used not only for natural gas but also for other gases or purposes. For example, the proposed relaxation of gas by initially at least substantially isochoric preheating and subsequent relaxation in particular for gas pressure or air pressure storage can be used. For example, the proposed relaxation can be used in an air pressure storage power plant. Such a power plant pumps in particular ambient air in underground caverns o. The like. For energy storage. When relaxing, the air, which is preferably under very high pressure, then drives in particular a generator or a sonic generator. stige work machine. The proposed relaxation can be used for better energy utilization just in connection with such an air storage power plant or for other purposes.

Individual features and aspects of the various embodiments and methods of operation may also be combined with one another as desired and / or used in other systems and methods for vaporizing and / or expanding natural gas or other gas.

Claims

claims:

Anspruch [en] A process for expanding gas, especially natural gas, from an initial pressure or elevated pressure to a discharge pressure and in particular for subsequent delivery to a gas supply device (G), wherein the gas is compressed by heat to an elevated pressure relative to the initial pressure, the heat input at least substantially isochoric, and wherein the gas after the heat supply from the increased pressure to the discharge pressure is released and in particular to the gas supply device (G) is discharged.

2. The method according to claim 1, characterized in that the increased pressure is selected such that the gas at the elevated pressure has an at least substantially independent of the temperature specific heat capacity.

3. A method for vaporizing liquid gas, in particular liquefied natural gas, and for subsequent delivery to a gas supply device (G) at a discharge pressure, in particular according to one of the preceding claims, wherein the liquid gas evaporates at a relative to the discharge pressure increased pressure by supplying heat or on is heated to at least 300 K, wherein the increased pressure is selected such that the gas at the elevated pressure has an at least substantially independent of the temperature specific heat capacity, wherein the vaporized or heated gas after the heat release to the discharge pressure and at the gas supply device (G) is discharged.

4. The method according to claim 3, characterized in that the liquid gas before the heat supply - preferably in several stages - is compressed to the increased pressure or above.

5. The method according to claim 3 or 4, characterized in that when a supply of heat in several steps, the supply is divided so that the transition from the liquid to the gaseous phase is completed within a single step.

6. The method according to any one of the preceding claims, characterized in that the heat - at least partially - at constant pressure (along an isobaric) is supplied.

7. The method according to any one of the preceding claims, characterized in that the heat - at least partially - at a constant volume

(along an isochore) is supplied.

8. The method according to any one of the preceding claims, characterized in that the gas is heated batchwise or batchwise at least substantially isochoric.

9. The method according to any one of the preceding claims, characterized in that the gas is released from the increased pressure without intermediate storage on the discharge pressure.

10. The method according to any one of the preceding claims, characterized in that the heat is supplied first isobaric and then isochoric or vice versa.

11. The method according to any one of the preceding claims, characterized in that the heat supply and / or relaxation in several steps, in particular alternately, takes place or take place, and / or that the heat is supplied in one or more heat exchangers (6, 6 ') ,

12. The method according to any one of the preceding claims, characterized in that the increased pressure is preferably more than 5 MPa, in particular more than 10 MPa, is above the discharge pressure and / or that the increased pressure is at least 18 MPa, preferably at least 20 MPa, in particular substantially 24 MPa or more.

13. The method according to any one of the preceding claims, characterized in that the gas is supplied at least substantially the amount of heat that the gas before the heat supply and after relaxing at least substantially the same temperature and / or after relaxing a temperature of 275 to 300 K has.

14. The method according to any one of the preceding claims, characterized in that the gas to more than 300 K, preferably more than 340 K, in particular substantially 360 K, is heated.

15. The method according to any one of the preceding claims, characterized in that the heat supply takes place by heat transfer from a warmer medium, which preferably has an at least substantially independent of the temperature specific heat capacity.

16. The method according to any one of the preceding claims, characterized in that the heat partially or completely from a power plant (7, 7 ') is supplied or provided, in particular to increase their efficiency.

17. The method according to any one of the preceding claims, characterized in that the gas generates mechanical energy when relaxing.

18. The method according to any one of the preceding claims, characterized in that the gas when relaxing an expansion machine (8) drives, preferably wherein the expansion machine (8) a working machine, in particular a generator (10), drives.

19. The method according to claim 18, characterized in that the expansion machine (8) comprises a turbine (9) or is designed as such, in particular wherein the turbine (9) with a power plant (7, 7 ') coupled - -

is, and / or that the expansion machine (8) comprises a displacement machine or reciprocating engine (9) or is designed as such.

20. The method according to any one of the preceding claims, characterized in that the gas is cooled during or by the relaxation under 300 K, in particular substantially to 273 to 285 K.

21. The method according to any one of the preceding claims, characterized in that the discharge pressure is at most 10 MPa, in particular substantially 8 to 8.5 MPa, 105 k Pa or the ambient pressure.

22. The method according to any one of the preceding claims, characterized in that the gas supply device (G) has a memory or a pipeline to which the expanded gas - optionally after a pressure control - is discharged.

23. A method for vaporizing liquefied natural gas, in particular according to one of the preceding claims, wherein liquefied natural gas is vaporized at a pressure of at least 15 or 20 MPa by supplying heat in a heat exchanger (6).

24. Plant (1) for the expansion of gas, in particular natural gas, from an initial pressure to a discharge pressure and preferably for subsequent delivery to a gas supply device (G), with a heat exchanger (6) for compressing the gas at least substantially constant volume to a compared to the initial pressure increased pressure by supplying heat preferably from a Kraftwerksanla- ge (7 ¹ ), in particular to increase their efficiency, and with an expansion machine (8) for relaxing the gas to the discharge pressure.

25. Plant (1) for the evaporation of liquid gas, in particular liquefied natural gas, and for subsequent delivery of the vaporized gas to a

Gas supply device (G) at a discharge pressure, with a first heat exchanger (6) for vaporizing the liquid gas preferably at at least substantially constant pressure by heat preferably from a power plant (7), in particular to increase their efficiency, with a second heat exchanger (6 ¹ ) for compressing the vaporized gas at least substantially constant volume to a relative to the discharge pressure increased pressure by heat preferably from a turbine plant (7 '), in particular to increase their efficiency, and with an expansion machine (8) for expanding the gas to the discharge pressure.

26. Plant according to claim 25, characterized in that the choice of pressure before entry into the first heat exchanger (6) and the temperature when entering the second heat exchanger (6 ¹ ) is selected such that the transition from the liquid to the gaseous state takes place in the first heat exchanger (6).

27. Plant according to one of claims 24 to 26, characterized in that the increased pressure is at least 18 MPa.

28. Plant (1) for the evaporation of liquid gas, in particular liquefied natural gas, with a pump (3, 4) for compressing the liquid gas to at least an elevated pressure and with a heat exchanger (6) for vaporizing the liquid gas in the increased pressure by the supply of heat preferably from a power plant (7), in particular to increase its efficiency, characterized in that the increased pressure is at least 18 MPa and / or the gas at the elevated pressure is at least substantially independent of the temperature specific Has heat capacity and / or - -

in that the heat can be supplied at constant pressure and / or constant volume and / or that the installation (1) has an expansion machine (8) arranged downstream of the heat exchanger (6) for depressurizing the gas to a discharge pressure which is lower than the elevated pressure.

29. Plant according to one of claims 24 to 28, characterized in that the increased pressure is preferably more than 5 MPa, in particular more than 10 MPa, above the discharge pressure.

30. Plant according to one of claims 24 to 29, characterized in that the increased pressure is at least 20 MPa, in particular substantially 24 MPa or more.

31. Plant according to one of claims 24 to 30, characterized in that the gas is heated to over 300 K, preferably more than 340 K, in particular substantially 360 K, by the supply of heat.

32. Installation according to one of claims 24 to 31, characterized in that the expansion machine (8) comprises a displacement machine, a reciprocating piston engine or a turbine (9) or is designed as such, in particular wherein the turbine (9) with the power plant (7 ¹ ) is coupled.

33. Plant according to one of claims 24 to 32, characterized in that the expansion machine (8) drives a working machine, in particular a generator (10).

34. Plant according to one of claims 24 to 33, characterized in that the gas during or by the relaxation below 300 K, in particular substantially to 273 to 285 K, is cooled.