EP3517742A1 - Generation of electric power and vaporisation of a cryogenically liquefied gas - Google Patents

Abstract

The invention relates to a device (1) for generating electrical energy and for vaporizing a cryogenic liquefied gas, comprising a heat engine (2) and a waste heat utilization system (3) connected downstream of the heat engine (2), which is connected to a fluid circuit (4) the device (1) further comprises a line (5) for the cryogenic liquefied gas, into which a first heat exchanger (6) is connected, the first heat exchanger (6) also being connected to the fluid circuit (4), wherein into the line (5) a pump (7) is connected in the flow direction of the cryogenic liquefied gas upstream of the first heat exchanger (6) and downstream of the first heat exchanger (6) an expansion turbine (8) and a second heat exchanger (9) are connected in the line (5) are, wherein the second heat exchanger (9) is also connected to the fluid circuit (4). The invention also relates to a method for generating electrical energy and for evaporating a cryogenic liquefied gas.

Description

The invention relates to a device for generating electrical energy and for the evaporation of a cryogenic liquefied gas, for example natural gas (LNG = liquefied natural gas) and a corresponding method.

Normally, after its production, natural gas is transported via lines to corresponding terminals in a port. There it is stored, processed and finally liquefied for transport with appropriate special vessels over long distances by strong compression and cooling (down to -162 ° C). After transport, the liquefied natural gas is regasified before being discharged into a gas network. In this case, the liquid natural gas is typically evaporated with ambient heat (air / seawater) or chemical heat. Alternatively, concepts were developed that aimed to use low temperature cold energy via cascading ORC cycles.

The object of the invention is to provide an energetically and economically optimal evaporation process for a cryogenic liquefied gas. Furthermore, it is an object of the invention to provide a correspondingly improved device.

The invention solves the object directed to a device by providing that in such a device for generating electrical energy and for the evaporation of a cryogenic liquefied gas, comprising a heat engine and a heat engine downstream Abhitzenutzungungssystem, which is connected in a fluid circuit, said Device further comprises a conduit for the cryogenic liquefied gas, in which a first heat exchanger is connected, wherein the first heat exchanger is also connected in the fluid circuit, in the line, a pump in the flow direction of the cryogenic liquefied gas is connected in front of the first heat exchanger and behind the first heat exchanger, an expansion turbine and a second heat exchanger are connected in the line, the second heat exchanger also connected in the fluid circuit is.

By coupling the evaporation to other processes and in particular by optimizing heat integration of the overall system, it becomes possible to achieve maximum utilization of the low-temperature refrigeration for power generation with the highest levels of efficiency. This is combined according to the invention with a pressure increase on the side of the cryogenic liquefied gas (example for LNG: 100-300 bar). Refrigerated liquefied gas means that the gas was liquefied by cooling. The temperatures are in the relevant to the invention gases in the order of -140 ° C and below. As a heat engine is typically a gas turbine used. But even the use of a gas engine, for example, is conceivable.

It is expedient if, after the expansion turbine, a branch line branches off from the line and the branch line opens into the heat engine. In particular, in the evaporation of LNG, but also in other gases, such as hydrogen, resulting in such a constellation advantages due to the "short distances".

In an advantageous embodiment of the invention, the branch line branches off after the second heat exchanger from the line. The regasified gas is cooled down so far that it is expedient if a third heat exchanger is connected in the branch line and in the fluid circuit in order to preheat the fuel for combustion in the thermal power plant.

In a further advantageous embodiment of the invention, a compressor is arranged in the fluid circuit between the first and the second heat exchanger. The fluid circuit should be operated as a 1-pressure process to optimize the efficiency of the device. For this purpose, in addition to a certain temperature and a corresponding pressure is required.

It is advantageous if the waste heat recovery system follows the second heat exchanger in the fluid circuit. In waste heat recovery system residual heat from the process of the heat engine is utilized. It is expedient if a turbine with a coupled generator follows in the fluid circuit on the waste heat utilization system so that the fluid heated in the waste heat recovery system can be released to work in the turbine.

Furthermore, it may be expedient if the third heat exchanger for fuel preheating is arranged in the fluid circuit between the turbine and the first heat exchanger. With the fuel preheating the sensible heat of the fuel is increased and the required amount of fuel is reduced.

In an advantageous embodiment of the invention, a fourth heat exchanger in the fluid circuit between the compressor and the second heat exchanger is arranged. Further, a fifth heat exchanger is connected with both sides in the fluid circuit and on the one hand between the third heat exchanger and the first heat exchanger and on the other parallel to Abhitzenutzungssystem. About the fourth heat exchanger, the fluid that is after the first heat exchange in which the cryogenic liquefied gas is regasified and also after the compressor typically still temperatures well below the freezing point (of water) has been heated by ambient heat. One possible application is the gas turbine intake air cooling, which results in a power increase of the gas turbine. But also other heat sources can be used, such as heated cooling water, seawater, ambient air is also in question. The thus heated fluid is then further heated in the second heat exchanger, wherein the previously cryogenic liquefied gas, which has been pressurized, heated and thereby regasified and was expanded in a turbine, but still has a temperature above a common temperature in a gas network , is cooled further. According to the invention, a portion (approximately of the order of 10 to 30%) of the fluid can be diverted from the main stream to the waste heat recovery system and further heated in heat exchange with the fluid, which has been somewhat cooled after expansion in the turbine and fuel preheating. This portion of the fluid is mixed again with the main stream after it has been heated in the waste heat recovery system.

Leaks in the expansion turbine in the path of the cryogenic liquefied gas can not be avoided. If the regasified gas is flammable, it is therefore advantageous if a leakage current can be supplied to the expansion turbine of an additional firing in the waste heat utilization system.

The claimed device can be used for various cryogenic liquefied gases. However, it is advantageous if the cryogenic liquefied gas is natural gas, alone with regard to its usability in the heat engine and Abhitzenutzungungssystem, but also with regard to the choice of fluid in the fluid circuit and the efficiency of the entire system. An alternative to natural gas is, for example, hydrogen.

In this context, it is particularly advantageous if the fluid circuit is a nitrogen cycle. Not least because of its inert properties, the use of nitrogen is advantageous. However, it is essential that nitrogen with a critical point of -147 ° C / 34 bara is excellently suited for supercritical heat exchange with the LNG.

The supercritical state prevents the formation of an isothermal condensation plateau. This minimizes the exergetic heat transfer losses. Furthermore, the solidification temperature of -210 ° C is well below the LNG temperature of -162 ° C, so that a freezing of the fluid is not possible.

It is expedient in this case, in particular, if the fluid circuit is a supercritically operated circuit. In the supercritical state, the heat of vaporization no longer plays a role, which has a positive effect on efficient heat transfer. In addition, the single phase of the fluid should improve its transport in the lines.

Finally, it is particularly advantageous for smaller plants when compressor, turbine and generator are arranged on an axis. Thus, savings can be achieved on the material side, because, for example, for the compressor no separate drive is needed, or because only one generator must be provided in the system.

The object directed to a method is achieved by a method for generating electrical energy and for evaporating a cryogenic liquefied gas, in which a fluid flow is circulated and is heated at least partially in a heat exchange with exhaust gases of a heat engine and a cryogenic liquefied gas in a first heat exchange with the fluid flow is heated and evaporated, wherein the cryogenic liquefied gas is compressed before the first heat exchange with the fluid flow and is relaxed after the first heat exchange with the fluid flow in an expansion turbine and is further cooled in a second heat exchange with the fluid flow.

Also in the process, a gas turbine is typically used as the heat engine. Alternatively, however, for example, a gas engine can be used.

Advantageously, the previously cryogenic liquefied gas is supplied at least in part to a gas network and in part to a heat engine.

It is furthermore advantageous if the gas supplied to the heat engine, which has previously been supplied with cryogenic liquefied gas, is preheated by the fluid flow in a third heat exchange for combustion.

It is expedient if the fluid stream heated in the heat exchange with exhaust gases of the heat engine is expanded in a turbine before it is used for fuel preheating in the third heat exchange.

In a particularly advantageous embodiment of the invention, in which ambient heat is used, the fluid is heated before its heating in the second heat exchange in a fourth heat exchange (by ambient heat, for example Gasurbinenansaugluft, seawater) and after heating in the second heat exchange, a first partial flow of the fluid alternatively for heat exchange with exhaust gases of the gas turbine further heated in a fifth heat exchange with relaxed in the turbine fluid and then mixed with a heated in heat exchange with exhaust gases of the heat engine second partial stream before a from the first and second partial flow existing total flow of the fluid is expanded in the turbine ,

Advantageously, the fluid flow is compressed between the first heat exchange and the second heat exchange.

It is also advantageous if a stream of nitrogen is used as the fluid stream.

Furthermore, it is advantageous if liquefied natural gas is used as the cryogenic liquefied gas.

Finally, it is advantageous if a leakage current at the expansion turbine downstream of one of the heat engine Abhitzenutzungungssystem supplied and burned there in an additional firing.

According to the invention, the regasification (preferably LNG) as well as the recycle process (preferably nitrogen) are operated as a 1-pressure process for optimal heat exchange, each up to the supercritical pressure range. With this, it is possible to leave the complete heat introduced into the process by the exhaust gas of the heat engine into the system in a manner that optimizes the efficiency.

Furthermore, with the concept according to the invention, preferably the LNG at the terminal point to the gas network can be set to the desired pressure and temperature level.

In addition, the design of the fluid circuit is optimally tailored to the requirements of the subsystems (e.g., internal heat displacement allows both the final LNG temperature and a minimum nitrogen temperature at the entrance to the waste heat recovery system downstream of the heat engine).

The optimal combination of systems and optimal choice of process parameters make it possible, for example, to achieve LNG power conversion efficiencies of 63-67%. This achieves a level that will not be achievable with conventional GUD technology over the next 10 years.

• alle Prozessparameter sind mit bereits heute verfügbaren Komponenten darstellbar,
• das Kraftwerk benötigt für seinen Betrieb kein Wasser,
• eine einfache Prozessstruktur ermöglicht einfache Regelung (z.B. nur eine Druckstufe im Stickstoffprozess statt mehrere) und
• das Verfahren ist umweltfreundlich, da gegenüber bisherigen Wiedervergasungsansätzen potentiell umweltschädliche Medien wie Glykol nicht vorhanden sind.

Further advantages are:

• all process parameters can be displayed with already available components,
• the power plant does not need water for its operation,
• a simple process structure allows easy control (eg only one pressure step in the nitrogen process instead of several) and
• The process is environmentally friendly, as compared to previous Wiedervergasungsansätzen potentially environmentally harmful media such as glycol are not available.

Figur 1

eine Vorrichtung zur Erzeugung elektrischer Energie und zur Verdampfung von verflüssigtem Erdgas nach der Erfindung,

Figur 2

ein Ausschnitt der Vorrichtung nach der Erfindung mit alternativem Strangkonzept und

Figur 3

ein Ausschnitt der Vorrichtung nach der Erfindung mit einem weiteren alternativen Strangkonzept.

The invention will be explained in more detail by way of example with reference to the drawings. Shown schematically and not to scale:

FIG. 1

a device for generating electrical energy and for the evaporation of liquefied natural gas according to the invention,

FIG. 2

a section of the device according to the invention with an alternative strand concept and

FIG. 3

a section of the device according to the invention with a further alternative strand concept.

The FIG. 1 shows schematically and by way of example a device 1 according to the invention. It comprises a heat engine 2 (in the example of FIG. 1 a gas turbine 2) and a gas turbine 2 downstream Abhitzenutzungungssystem 3, similar to a heat recovery steam generator in gas and steam turbine plants. However, the invention does not provide a water vapor cycle. In the embodiment of FIG. 1 is the fluid circuit 4, which is connected in the Abhitzenutzungungssystem 3, a nitrogen cycle. The device 1 further comprises a line 5, in the present case a natural gas line, in which a first heat exchanger 6 is connected, wherein the first heat exchanger 6 is also connected in the fluid circuit 4. In the first heat exchanger 6 heat is transferred from the nitrogen to the liquefied natural gas, wherein the liquefied natural gas is heated and evaporated. So that the fluids involved can each be brought into the supercritical pressure range for optimum heat exchange, a pump 7 is connected in the natural gas line 5 in the flow direction of the natural gas in front of the first heat exchanger 6 and in the fluid circuit 4, a compressor 12.

Pressure and heat of the natural gas are advantageously used behind the first heat exchanger 6 in an expansion turbine 8 and in a second heat exchanger 9, which is also connected in the fluid circuit 4 (= nitrogen circuit). In the embodiment of FIG. 1 the expansion turbine 8 is coupled to a generator 23. The amount of heat in the regasified and expanded natural gas, which is above that which makes sense for the gas network 17, is returned to the nitrogen cycle 4 via the second heat exchanger 9.

Part of the expanded natural gas is in the embodiment of FIG. 1 supplied to the gas turbine 2. For this purpose, branched off after the expansion turbine 8 and the second heat exchanger 9, a branch line 10 from the line 5. The branch line 10 opens into the gas turbine 2. The embodiment of FIG. 1 shows both options for the branch of the branch line: once in front of the second heat exchanger 9 and once behind the second heat exchanger. 9

For fuel preheating, a third heat exchanger 11 is connected in the branch line 10 and in the fluid circuit 4 (= nitrogen cycle). Branched the branch line 10 before the second heat exchanger 9 from the line 5, can be dispensed with the third heat exchanger 11 for fuel preheat rather than a branch after the second heat exchanger 9. Basically, the concept works in both circuit variants without third heat exchanger 11 However, in both variants, the use of such a third heat exchanger 11.

In the fluid circuit 4 (= nitrogen cycle) is in the embodiment of the FIG. 1 between the first 6 and the second heat exchanger 9, a compressor 12 is arranged. Further follows on the second heat exchanger 9, the Abhitzenutzungssystem 3, and a turbine 13 with coupled generator 14th

The third heat exchanger 11 for the fuel preheating is arranged in the fluid circuit 4 between the turbine 13 and the first heat exchanger 6.

Finally, in FIG. 1 indicated that a necessarily incurred leakage current 15 of natural gas to the expansion turbine 8 an additional firing 16 in Abhitzenutzungssystem 3 can be fed. In the present case of the embodiment of FIG. 1 With a nitrogen cycle as a fluid circuit 4, the leakage can be sealed at the expansion turbine 8 via the shaft seal with nitrogen and fed, for example, as a natural gas-nitrogen mixture of supplementary firing 16 in Abhitzenutzungssystem 3.

Also, the turbine 13, in the embodiment of the FIG. 1 Nitrogen is released, has leaks. These can be sucked off at least in part 18 and then returned to the fluid circuit 4. In general, a feed 19 of nitrogen into the fluid circuit 4 is provided.

Finally, the shows FIG. 1 a not necessarily necessary but interesting use of so-called residual heat for the inventive device. It is provided that a fourth heat exchanger 20 is arranged in the fluid circuit 4 between the compressor 12 and the second heat exchanger 9. In the embodiment with natural gas and nitrogen, the nitrogen after the regasification of the natural gas in the first heat exchanger 6 and the compression in the compressor 12 has a temperature approximately between -50 and -60 ° C and is thus comparatively well below ambient temperature, so that a heating means offers free available ambient heat. Conceivable heat sources are ambient air, seawater, heated cooling water. It is particularly interesting if this heat exchange still another advantage is connected, such as in Gasurbinenansaugluftkühlung.

Further heating of the nitrogen takes place in the second heat exchanger 9 in heat exchange with the regasified natural gas before the nitrogen flow is divided and typically a larger part in the waste heat recovery system 3 is further heated and a smaller part is further heated in a fifth heat exchanger 21, wherein in the fifth heat exchanger 21 heat within the fluid circuit 4 is moved.

The fifth heat exchanger 21 is in fact connected with both sides in the fluid circuit 4 and on the one hand between the third heat exchanger 11 and the first heat exchanger 6 (heat-emitting side) and the other parallel to Abhitzenutzungssystem. 3

After heating in the waste heat utilization system 3 and in the fifth heat exchanger 21, the two parts of the nitrogen stream are again brought together and the turbine 13.

The FIGS. 2 and 3 show alternative string concepts. The compressor 12 requires a drive and the embodiment of the device 1 of FIG. 1 has two generators 14 and 23. By arranging the compressor 12 and a single generator 14 on a common axis 22 with the turbine 13 components can be saved.

Claims (23)

Device (1) for generating electrical energy and for evaporating a cryogenic liquefied gas, comprising a heat engine (2) and a heat engine (2) downstream Abhitzenutzungungssystem (3), which is connected in a fluid circuit (4), wherein the device (1 ) further comprises a line (5) for the cryogenic liquefied gas, in which a first heat exchanger (6) is connected, wherein the first heat exchanger (6) in the fluid circuit (4) is connected, characterized in that in the line ( 5) a pump (7) in the flow direction of the cryogenic liquefied gas in front of the first heat exchanger (6) is connected and behind the first heat exchanger (6) an expansion turbine (8) and a second heat exchanger (9) are connected in the conduit (5) , wherein the second heat exchanger (9) is also connected in the fluid circuit (4). Device (1) according to claim 1, wherein after the expansion turbine (8) a branch line (10) branches off from the line (5) and the branch line (10) opens into the heat engine (2). Device (1) according to claim 2, wherein the branch line (10) only after the second heat exchanger (9) branches off from the line (5). Device (1) according to one of claims 2 or 3, wherein a third heat exchanger (11) in the branch line (10) and in the fluid circuit (4) is connected. Device (1) according to one of the preceding claims, wherein in the fluid circuit (4) between the first (6) and the second heat exchanger (9) a compressor (12) is arranged. Device (1) according to one of the preceding claims, wherein in the fluid circuit (4) to the second heat exchanger (9) the Abhitzenutzungssystem (3) follows. Device (1) according to one of the preceding claims, wherein in the fluid circuit (4) the waste heat utilization system (3) is followed by a turbine (13) with a coupled generator (14). Device (1) according to one of the preceding claims, wherein in the fluid circuit (4) between the turbine (13) and the first heat exchanger (6) of the third heat exchanger (11) is arranged. Device (1) according to claims 4 and 5, wherein a fourth heat exchanger (20) in the fluid circuit (4) between the compressor (12) and the second heat exchanger (9) is arranged and wherein a fifth heat exchanger (21) with both sides in the fluid circuit (4) is connected on the one hand between the third heat exchanger (11) and the first heat exchanger (6) and on the other hand parallel to Abhitzenutzungssystem (3). Device (1) according to one of the preceding claims, wherein a leakage stream (15) can be supplied to the expansion turbine (8) of an additional firing (16) in the waste heat utilization system (3). Device according to one of the preceding claims, wherein the cryogenic liquefied gas is natural gas. Device (1) according to one of the preceding claims, wherein the fluid circuit (4) is a nitrogen cycle. Device (1) according to claim 12, wherein the nitrogen cycle is a supercritical operated fluid circuit (4). Device (1) according to one of the preceding claims, wherein compressor (12), turbine (13) and generator (14) are arranged on an axle (22). Method for generating electrical energy and for evaporating a cryogenic liquefied gas, in which a fluid flow is circulated and at least partially heated in a heat exchange with exhaust gases of a heat engine (2) and a cryogenic liquefied gas is heated in a first heat exchange with the fluid flow and is vaporized, characterized in that the cryogenic liquefied gas is compressed before the first heat exchange with the fluid flow and after the first heat exchange with the fluid flow in an expansion turbine (8) is relaxed and further cooled in a second heat exchange with the fluid flow. A method according to claim 15, wherein the previously cryogenic liquefied gas is supplied at least in part to a gas network (17) and partly to the heat engine (2). A method according to claim 16, wherein the previously cryogenic liquefied gas supplied to the heat engine (2) is preheated by the fluid flow in a third heat exchange for combustion. The method of claim 17, wherein the heat exchanged in the heat exchange with exhaust gases of the heat engine (2) fluid stream in a turbine (13) is relaxed before it is used for fuel preheating in the third heat exchange. Method according to one of claims 17 or 18, wherein the fluid is heated in a fourth heat exchange before being heated in the second heat exchange and after heating in the second heat exchange, a first partial flow of the fluid alternatively to heat exchange with exhaust gases of the thermal power plant (2) in a fifth Heat exchange with in the turbine (13) is further heated relaxed fluid and then mixed with a heat exchange with exhaust gases of the heat engine (2) heated second partial stream before a from the first and second partial flow existing total flow of the fluid in the turbine (13) is relaxed. Method according to one of claims 15 to 19, wherein the fluid flow between the first heat exchange and the second heat exchange is compressed. A method according to any one of claims 15 to 20, wherein a nitrogen stream is used as the fluid stream. A method according to any one of claims 15 to 21, wherein liquefied natural gas is used as the cryogenic liquefied gas. Method according to one of claims 15 to 22, wherein a leakage current to the expansion turbine (8) to a heat engine (2) downstream Abhitzenutzungungssystem (3) is fed and burned there in an additional firing.

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