METHOD AND SYSTEM FOR CONDENSING A GAS

Abstract

The invention relates to a method for condensing a gas, wherein the gas is subjected to cooling in indirect heat exchange with a refrigerant and at least part of the refrigerant is subjected, after the heat exchange with the gas, to compression by means of a drive (GT1) that produces waste heat and to a partial or complete condensing process. After the partial or complete condensing process, a first portion of the refrigerant is subjected to the heat exchange with the gas and a second portion of the refrigerant is subjected, in succession, to pressurization, heating by means of the waste heat of the drive (GT1) and work-performing expansion and thereafter is fed back to the partial or complete condensing process. The invention further relates to a corresponding system.

Claims

1. A method for condensing a gas, wherein the gas is subjected to cooling in indirect heat exchange with a refrigerant, and at least a part of the refrigerant is subjected, after the heat exchange with the gas, to compression using a drive that produces waste heat and to a partial or complete condensing process, wherein, after the partial or complete condensing process, a first portion of the refrigerant is subjected to the heat exchange with the gas, and that a second portion of the refrigerant is subjected, in succession, to pressurization, heating using the waste heat of the drive and to work-performing expansion, and thereafter is fed back to the partial or complete condensing process.

2. The method according to claim 1, with which a mixed refrigerant is used as the refrigerant in one or more mixed refrigerant circuits and/or with which natural gas or a gas mixture formed using natural gas is used as the gas and/or with which a gas turbine is used as the drive that produces waste heat.

3. The method according to claim 1, with which work performed during the work-performing expansion is used in addition to the drive in the compression of the same refrigerant.

4. The method according to claim 3, with which the compression of the refrigerant comprises a first compression step to a first pressure level and a second compression step to a second pressure level above the first pressure level, wherein the drive is used in the first compression step and the work performed during the work-performing expansion is used in the second compression step.

5. The method according to claim 1, with which the first and second portions are in each case portions of a first refrigerant, and with which work performed during the work-performing expansion is used in the compression of a second refrigerant, wherein the first refrigerant is a pure refrigerant and the second refrigerant is a mixed refrigerant, or wherein the first refrigerant is a mixed refrigerant and the second refrigerant is nitrogen.

6. The method according to claim 4, with which the refrigerant is at least partially subjected to the first compression step and subsequently at least partially subjected to a first partial condensing process to obtain a first liquid fraction and a first gas fraction, wherein the first gas fraction is at least partially subjected to the second compression step and subsequently at least partially subjected to a second partial condensing process to obtain a second liquid fraction and a second gas fraction.

7. The method according to claim 6, with which after its work-performing expansion, the second portion of the refrigerant is at least partially combined with the refrigerant or a part thereof before the latter is subjected to cooling for the first partial condensing process.

8. The method according to claim 6, with which before its work-performing expansion, the second portion of the refrigerant is at least partially subjected to indirect heat exchange with the second portion of the refrigerant or a part thereof, after the latter was subjected to the work-performing expansion and before the latter is combined with the first gas fraction.

9. The method according to claim 6, with which the second liquid fraction is at least partially expanded and combined with the refrigerant compressed in the first compression step.

10. The method according to claim 6, with which a heat exchanger having a plurality of sections or a plurality of heat exchangers is used for cooling the gas in indirect heat exchange with the refrigerant, wherein the first portion of the refrigerant and the second gas fraction or parts thereof are further cooled to different temperature levels and reheated after expansion.

11. The method according to claim 1, with which the work performed during the work-performing expansion is used in addition to the drive in the compression of a further refrigerant, with which the gas is subjected to cooling in indirect heat exchange.

12. A system for condensing a gas, wherein the system has means configured to subject the gas to cooling in indirect heat exchange with a refrigerant, and at least a part of the refrigerant is subjected, after the heat exchange with the gas, to compression using a drive that produces waste heat and to a partial or complete condensing process, wherein means configured to subject, after the partial or complete condensing process, a first portion of the refrigerant to the heat exchange with the gas, and a second portion of the refrigerant, in succession, to pressurization, heating using the waste heat of the drive and to work-performing expansion, and thereafter to feed it back to the partial or complete condensing process.

13. A system for condensing a gas, wherein the system has means configured to subject the gas to cooling in indirect heat exchange with a refrigerant, and at least a part of the refrigerant is subjected, after the heat exchange with the gas, to compression using a drive that produces waste heat and to a partial or complete condensing process, wherein means configured to subject, after the partial or complete condensing process, a first portion of the refrigerant to the heat exchange with the gas, and a second portion of the refrigerant, in succession, to pressurization, heating using the waste heat of the drive and to work-performing expansion, and thereafter to feed it back to the partial or complete condensing process, wherein the system is configured to carry out a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG. 1 illustrates a method in accordance with an embodiment of the invention.

[0057] FIG. 2 illustrates a method in accordance with an embodiment of the invention.

[0058] FIG. 3 illustrates a method in accordance with an embodiment of the invention.

[0059] FIG. 4 illustrates a method in accordance with an embodiment of the invention.

[0060] FIG. 5 illustrates a method in accordance with an embodiment of the invention.

[0061] FIG. 6 illustrates a method in accordance with an embodiment of the invention.

[0062] FIG. 7 illustrates a method in accordance with an embodiment of the invention.

[0063] FIG. 7A illustrates a variant of the method in accordance with FIG. 7.

[0064] FIG. 8 illustrates a method in accordance with an embodiment of the invention.

[0065] FIG. 9 illustrates a method in accordance with an embodiment of the invention.

[0066] In the figures, elements corresponding to one another are indicated by identical reference signs and are not explained repeatedly for the sake of clarity. Identical elements are not designated separately in all figures.

DETAILED DESCRIPTION OF THE DRAWINGS

[0067] FIG. 1 illustrates a method in accordance with an embodiment of the invention with reference to a schematic process flowchart.

[0068] The method serves to condense a gas that is supplied to the method in the gaseous state as substance flow 1 and is provided in condensed form as substance flow 2. An overall highly simplified heat exchanger or cryogenic part 10 is used here for the condensing process. In order to illustrate general applicability, the heat exchanger part 10 is shown in highly simplified form.

[0069] Refrigerant is discharged from the heat exchanger part 10 in the form of a heated (“warm”) refrigerant flow W. Remaining condensate is separated in a separator D1. The refrigerant of the substance flow W is compressed in a first compression step using a compressor C1, which is driven by a gas turbine GT1. In the gas turbine GT1, air of an air flow A is compressed in a compressor stage, which is not designated separately, and is combusted with fuel F in a combustion chamber (not shown). Hot gas is expanded in an expansion stage, which is likewise not designated separately, and is discharged via a heat exchanger E4 for heat recovery. Auxiliary firing using further fuel AF can also take place.

[0070] The refrigerant compressed in the compressor C1 is cooled in a heat exchanger E1, thereby partially condensed, and subjected to phase separation in a separator D2. The gas and liquid phases are supplied to the heat exchanger part 10 in the form of separate substance flows, wherein a part of the liquid phase is supplied to the heat exchanger part 10 as the “first portion” of the refrigerant, which was previously referred to correspondingly several times, and a further part as the “second portion” in the form of a substance flow R is increased in pressure by means of a pump P1, heated in a heat exchanger E3 and thereafter in the heat exchanger E4, then expanded in a work-performing manner in an expansion machine X1, passed through the heat exchanger E3, and subsequently combined with the refrigerant compressed in the compressor C1 before its cooling.

[0071] A compressor C2 is coupled to the expansion machine X1 via a transmission G. A mixed refrigerant in the form of a heated refrigerant flow W1 can be supplied to the compressor C2 from the heat exchanger part 10, so that utilization of the waste heat of the gas turbine GT1 is possible in this way. FIG. 1 uses a further mixed refrigerant with the refrigerant flow W1 in addition to the refrigerant of the refrigerant flow W and thus relates to a DMR circuit. The use of such a further mixed refrigerant is likewise possible in all embodiments of the invention explained below, even if in each case only one mixed refrigerant circuit, optionally with partial circuits, is illustrated there.

[0072] FIG. 2 illustrates a method in accordance with a further embodiment of the invention with reference to a schematic process flowchart. In particular, FIG. 2 illustrates the heat exchanger part 10 in more detail. The latter comprises in particular a coiled heat exchanger 11 and a separator 12, the function of which are explained below.

[0073] The refrigerant flow W1 in accordance with FIG. 1 or a comparable substance flow is not provided here, so that the specific embodiment is an SMR circuit. The refrigerant flow W is compressed here in a first compression step using a compressor C1 and in a second compression step using a compressor C2, wherein the first compressor C1 is driven by means of the gas turbine GT1 and the second compressor C2 is driven by means of the work performed in the expansion machine X1 during the work-performing expansion.

[0074] The substance flow W is compressed in the compressor C1 downstream of the separator D1 and subsequently, after cooling in a heat exchanger E1, is subjected to a partial condensing process in a separator D2 to obtain a first liquid fraction and a first gas fraction. The first gas fraction, which is not separately designated, from the separator D2 is compressed in the second compressor C2 and subsequently, after cooling in a heat exchanger E2, is subjected to a partial condensing process in a separator D3 to obtain a second liquid fraction and a second gas fraction.

[0075] The first liquid fraction from the separator D2 is partially treated in the form of the substance flow R as already explained above. The remainder, like the second gas fraction from the separator D2, is supplied to the coiled heat exchanger 11 in the form of a substance flow which is not separately designated. The specified refrigerant flows are passed through separate heat exchanger tubes and cooled.

[0076] The first liquid fraction from the separator D2 not used in the form of the substance flow R is extracted from the heat exchanger 11 at a first intermediate temperature level below the corresponding inlet temperature level, expanded and fed back to the heat exchanger 11 on the shell side. The second gas fraction can likewise be extracted from the heat exchanger at the first intermediate temperature level, expanded and thereby partially condensed, wherein, however, a phase separation into a liquid phase and a gas phase is carried out outside the heat exchanger 11 in the separator 12.

[0077] The liquid phase formed in the separator 12 and the gas phase are fed back separately from one another to the heat exchanger 11 at the first intermediate temperature level and further cooled by separate heat exchanger tubes. The liquid phase is extracted at a second intermediate temperature level below the first intermediate temperature level, expanded and fed back to the heat exchanger 11 on the shell side. The gas phase is extracted at a third intermediate temperature level below the second intermediate temperature level, expanded and likewise fed back to the heat exchanger 11 on the shell side. The fluids combined on the shell side in this way are fed back to the compression in the form of the substance flow W.

[0078] After its work-performing expansion, the substance flow R is combined with the refrigerant that was compressed in the compressor C1, before the latter is cooled for the first partial condensation. The second liquid fraction from the separator D3 is expanded via a valve V1 and returned to the separator D2.

[0079] FIG. 3 illustrates a further embodiment of the invention that in particular differs from the embodiment in accordance with FIG. 2 in that a soldered plate heat exchanger 13 is provided instead of the coiled shell-and-tube heat exchanger 11.

As illustrated here, the portion of the first liquid fraction from the separator D2 not used in the form of the substance flow R and the second gas fraction from the separator D3 can be supplied together to the heat exchanger 13 and cooled in common passages. A pump 14 boosts the portion of the first liquid fraction thus used to the pressure of the second gas fraction, so that both fractions can be fed together to the heat exchanger 13. After extraction at the cold end, expansion can be carried out via a valve 15 and the refrigerant further cooled in this way can be returned through separate passages and, after corresponding heating, can be fed into the separator D1 again.

[0080] FIG. 4 illustrates a further embodiment of the invention, in which the first compression step previously carried out in the compressor C1 is in particular designed differently and is carried out using two compressor stages (a first compressor stage C1A and a second compressor stage C1B). These stages are driven together by the gas turbine GT1.

[0081] Furthermore, three heat exchangers 16, 17, 18, each designed as a coiled heat exchanger, are used. In the language used herein, they are a first heat exchanger 16, a second heat exchanger 17 and a third heat exchanger 18 in the direction of decreasing temperature of the gas 1 to be condensed. The first heat exchanger 16 may be omitted, as explained in detail above.

[0082] Correspondingly evaporated refrigerant flows are supplied from the first and second heat exchangers 16, 17 to the first compressor stage C1A and compressed there. An evaporated refrigerant flow is supplied from the third heat exchanger 18 to the second compressor stage C1B and compressed there. Recooling takes place in each case downstream of the compressor stages. The first and second portions of the refrigerant previously mentioned several times are formed from the fluid that is compressed in the first compressor stage C1A and that, in addition to the specified refrigerant, can also comprise further refrigerant, which is extracted from the separator also designated here with D2.

[0083] The first portion is initially passed through the first heat exchanger 16 on the tube side and cooled there. A partial flow can be expanded downstream of the first heat exchanger 16 and fed on the shell side into the first heat exchanger 16. The non-expanded remainder of the first portion of the refrigerant can be used to form a further partial flow, which can be used in a separate further heat exchanger E5 to cool the fluid compressed in the second compressor stage C1B of the first compression step and can thereafter be fed to the first compressor stage C1A of the first compression step. A remainder of the first portion still remaining thereafter is initially passed through the second heat exchanger 17 on the tube side and cooled therein. This remainder can now be expanded downstream of the second heat exchanger 17 and fed on the shell side into the second heat exchanger 17.

[0084] The second portion of the refrigerant can be treated essentially as described above in the form of the substance flow R and can in particular be fed to the refrigerant compressed in the first compressor stage C1A of the first compression step, before the latter is further cooled and condensed. The second portion is circulated in this way.

[0085] The refrigerant compressed in the second compressor stage C1B of the first compression step can in particular be supplied to the second compression step with the compressor C2 and compressed there in principle as explained for the first embodiment. The correspondingly compressed refrigerant is cooled in a further heat exchanger E6 and initially passed through the first to third heat exchangers 16, 17, 18 on the tube side for further cooling. Downstream of the last one, this refrigerant portion is expanded and fed on the shell side into the third heat exchanger 18.

[0086] Yet another preferred embodiment of the present invention is illustrated in FIG. 5. This embodiment comprises the first compression step being carried out using two compressors, which are designated here for the sake of better comparability as previously with C1A and C1B but are now driven by two separate drives (gas turbines) GT1A and GT1B that supply waste heat. Accordingly, the heat exchangers E3 and E4 previously provided once are now provided twice in the form of the heat exchangers E3A, E3B and E4A, E4B. The second portion of the refrigerant, which is ultimately expanded in the form of the substance flow R, is heated in this embodiment beforehand with the waste heat of both drives GT1A and GT1B.

[0087] A further embodiment of the present invention is illustrated in FIG. 6 and is designed in the form of a mixed circuit (e.g., C3MR) process precooled with a pure refrigerant.

[0088] The compression of a pure refrigerant (illustrated here by way of example as propane C3H8) in a precooling circuit is carried out here in a first compressor C1A, and the compression of a mixed refrigerant in a mixed refrigerant circuit takes place using a second compressor C1B and a third compressor C2. The work performed during the work-performing expansion is used to drive the third compressor C2. The first and second compressors C1A, C1B are driven by two separate drives, wherein only the drive of the second compressor C1B is a drive, such as a gas turbine GT1, that supplies waste heat (at least to a considerable and usable extent). The first compressor C1A can, for example, be driven by means of a motor M, producing significantly lower (and not usable) quantities of waste heat.

[0089] In deviation from the previously explained embodiments, a soldered plate heat exchanger 19 in addition to a coiled heat exchanger 11 is used to cool the gas 1 to be condensed. The refrigerant of the pure substance circuit is supplied to the first compressor C1A in a plurality of partial flows, which are in particular heated and evaporated against the mixed refrigerant from the second compression step and thus precool the mixed refrigerant, and compressed there. After subsequent cooling and condensing, the first and second portions of the refrigerant are also formed here. The first portion is initially supercooled, subsequently heated and evaporated against the mixed refrigerant from the second compressor, and fed back to the first compressor C1A. The second portion R is treated as already mentioned above and thereby heated with the waste heat of the drive of the second compressor.

[0090] After its precooling, the mixed refrigerant is cooled further with the refrigerant of the pure refrigerant circuit on the tube side in the coiled heat exchanger 11. Downstream thereof, it is expanded and supplied on the shell side to the coiled heat exchanger 11. After extraction from the coiled heat exchanger 11 and corresponding heating, further heating is carried out in the soldered plate heat exchanger 19, and compression subsequently takes place in the second and third compressors C1B and C2.

[0091] A variant of the embodiment just explained is illustrated in FIG. 7, which comprises the first and second compressors C1A, C1B being driven via a common drive GT1 that produces waste heat.

[0092] FIG. 7A again shows a variant of the embodiment illustrated in FIG. 7, which can, however, also be readily realized as a variant of, for example, the embodiment shown in FIG. 6 or another embodiment of the invention. Here, a partial flow R′ of the refrigerant flow R is not passed through the heat exchanger E3 but through a heat exchanger E4′, which is arranged downstream of the heat exchanger E4 in the turbine waste gas flow of the gas turbine GT1. As shown in the form of dashed but not separately designated substance flows and heat exchangers, the precooling of the refrigerant can also be designed differently and can in particular comprise fewer heat exchanger stages than previously shown.

[0093] In all cases, work performed during the work-performing expansion can be used in the compression of a further refrigerant, with which the gas is subjected to cooling in indirect heat exchange. This may be the case, for example, when using a mixed refrigerant circuit precooled with a pure refrigerant, or in further variants of the invention illustrated in FIGS. 8 and 9. Further soldered plate heat exchangers 19A and 19B operated using a nitrogen circuit are used in these variants.

[0094] The treatment of the mixed refrigerant results directly from FIGS. 8 and 9 and the explanations above and essentially takes place analogously to, for example, FIG. 3, wherein, however, the compressors C1 and C2 are operated using the gas turbine GT1 here.

[0095] In the embodiment in accordance with FIG. 8, the nitrogen of the nitrogen circuit is subjected to an expansion machine X2 and to a compression in a compressor C3, wherein the compression of the nitrogen takes place in the expansion machine X1 using the work performed during the work-performing expansion of the second portion of the mixed refrigerant. The expansion of the nitrogen takes place in a work-performing manner in an expansion machine X2, wherein work performed during the work-performing expansion of the nitrogen is likewise used in the compression of the nitrogen. The expansion machines X1 and X2 along with the compressor C3 are mechanically coupled here.

[0096] The compressed nitrogen is, in succession, cooled, subjected to a first indirect heat exchange in the heat exchanger 19B and thereby cooled, subjected to the expansion, subjected to a second indirect heat exchange in the heat exchanger 19A and thereby heated, thereafter again subjected to the first indirect heat exchange in the heat exchanger 19B and thereby heated, and fed back to the compression. In the second indirect heat exchange in the heat exchanger 19A, the gas previously subjected to the partial or complete condensing process is supercooled. A heat exchanger E7 is provided for recooling the nitrogen in the nitrogen circuit downstream of the compressor C3.

[0097] In the embodiment in accordance with FIG. 9, which otherwise essentially corresponds to the embodiment in FIG. 8, the nitrogen is compressed in two stages in a first and thereafter a second compression step in compressors C3 and C4, wherein the first compression step takes place using the work performed during the work-performing expansion of the nitrogen in an expansion machine X1, and the second compression step takes place using the work performed during the work-performing expansion of the second portion of the mixed refrigerant in an expansion machine X2. In this embodiment, the expansion machine X1 and the compressor C4 are coupled on the one hand and the expansion machine X2 and the compressor C3 are coupled on the other hand.

[0098] The invention described above and its explained embodiments in particular shown in the figures are described again below in other words. The terms used below may be synonymous with the terms used above for the method steps, devices and media referred to in each case. The following explanations describe the same inventive concept with corresponding advantageous developments as the above explanations in at least partially deviating formulation.

[0099] The present invention relates to a method for collecting or recovering waste heat produced in a gas condensing process, comprising condensing a gas by a heat exchange process using a refrigerant fluid, compressing the spent refrigerant fluid from the condensing process by a method that produces excess heat, condensing at least a part of the compressed refrigerant fluid, pumping a part of the condensed compressed refrigerant fluid to a higher pressure, heating the part of the condensed compressed compressed refrigerant fluid at a higher pressure by absorbing the excess heat produced by the compression of the spent refrigerant fluid, whereby the part of the compressed refrigerant fluid is superheated at a higher pressure, and using the superheated compressed refrigerant fluid to supply a mechanical process.

[0100] One embodiment of the present invention applies to a natural gas condensing method with at least one compressor used in the refrigerant circuit for the cryogenic process of the natural gas condensing process. The present invention uses a compressor in the refrigerant circuit, wherein the compressor is driven by a gas turbine or a similar energy source that produces waste heat during the generation of power for operating the compressor. The present invention uses a work expander, wherein the fluid circuit for the work expander is used to absorb the waste heat of the gas turbine or a similar power source that drives the compressor in the refrigerant circuit. In one embodiment of the invention, the fluid circuit for the work expander is both pressurized and heated so that the fluid circuit can absorb the waste heat present in the waste gas flow of the gas turbine or other waste heat of the power source that drives the compressor in the refrigeration circuit. The resulting superheated fluid, which arises from the recovery process for the waste heat energy, is then used as an energy source for the drive of the work expander.

[0101] In a further embodiment of the present invention, the fluid used in the fluid circuit for the work expander is also used for the refrigerant circuit. In this embodiment of the invention, a second compressor is additionally used in the refrigerant circuit, wherein the second compressor is driven by the work expander. Accordingly, in this embodiment of the invention, the refrigerant fluid used in the cryogenic process for condensing natural gas is also used for absorbing waste heat, which is produced for driving the first compressor in order to provide power for driving the work expander, which in turn drives the second compressor in order to further compress the refrigerant fluid. Accordingly, this embodiment of the present invention offers advantages over other systems for collecting waste heat energy. This embodiment of the present invention thus requires neither the introduction of additional working liquids, such as water, nor the addition of other liquids (e.g., steam, ammonia, propane, etc.) in closed circuits.

[0102] In a natural gas condensing process (not illustrated) in accordance with the prior art, with which a single mixed refrigerant (SMR) with a two-stage SMR compression process is used, it can be provided that two compressors C1 and C2 are driven by a single gas turbine GT1. In this case, a cryogenic part of the process carries out the condensing process of the natural gas by a heat exchange process with a mixed refrigerant. In the natural gas condensing process, the mixed refrigerant is compressed, cooled and partially condensed before it is recycled in the cryogenic process. Mixed refrigerant discharged by the cryogenic part can be collected in a container D1 and is then conducted into the first compressor C1 and the heat exchanger E1. In a corresponding two-stage compression process, the liquid portion of the first compressor C1 and of a heat exchanger E1 is collected in a storage container D2, wherein the vapor portion of the first compressor C1 is fed into the second stage of the process via the second compressor C2 and a heat exchanger E2. The resulting portion is combined from the second compressor C2 and the heat exchanger E2 and collected in a container D3. The two fractions collected in the containers D2 and D3 may be fed into the cryogenic part, in order to carry out the condensing process of natural gas by a heat exchange process.

[0103] FIG. 2 shows an embodiment of the present invention in a natural gas condensing process in which a single mixed refrigerant (SMR) is used with a two-stage SMR compression process. In FIG. 2, the second compressor C2 is driven by a work expander X1 instead of a gas turbine. The work expander X1 is driven by superheated fluid supplied by a heat exchanger E4. The fluid discharged by the work expander X1 is cooled by an economizer or waste heat exchanger E3 and then combined with the refrigerant produced by the first compressor C1. The combined liquids are then further cooled by a heat exchanger E1 or the like and collected in a container D2. A part of the combined liquids collected in the container D2 is then conveyed by the pump P1 to the heat exchanger E3. The cooled fluid pumped into the waste heat exchanger E3 is heated and subsequently conducted into the heat exchanger E4. The heat exchanger E4 is fluidically connected to the warm waste gas of the gas turbine GT1, which drives the first compressor C1. In this case, the heat exchanger E4 utilizes the heat from the waste gas of the gas turbine GT1, in order to superheat the heated liquid supplied to the heat exchanger E4 from the heat exchanger E3. The superheated fluid from the heat exchanger E4 is then conducted into the work expander X1, in order to drive the second compressor C2.

[0104] In one embodiment of the present invention, the cryogenic part can be designed with coil-wound heat exchangers (CWHEs), soldered plate heat exchangers (PFHEs) or a combination thereof. FIG. 3 is, for example, an illustration of an embodiment of the present invention using a single mixed refrigerant (SMR) configuration using soldered plate heat exchangers (PFHEs) in the cryogenic part.

[0105] In one embodiment of the invention, which is shown in FIG. 1, a partial flow of 30 to 90% by volume of the exiting liquid container D2 is pumped by means of the pump P1 to at least three times the pressure in the reservoir D2. The high-pressure flow of the pump P1 is then heated by a waste heat exchanger E3 and supplied to the superheater E4. The superheater E4 recovers the waste heat from the waste gas flow of the gas turbine GT1 and heats the high-pressure flow from the waste heat exchanger E3 to at least 180° C., preferably at least 200° C. The hot gas from the superheater E4 is then fed into the work expander X1 and reduced to a pressure, which is slightly above the operating pressure of the reservoir D2. In one embodiment of the invention, the pressure of the flow leaving the work expander X1 is high enough to overcome the pressure drop in the heat exchangers E3 and E1, which still encounter the pressure in D2. The flow exiting the work expander X1 is then cooled and condensed at least partially by the economizer E3 and the heat exchanger E1 and subsequently returned to the reservoir D2. The shaft power generated by the work expander X1 is used to drive the compressor C2 to compress the refrigerant, which is then stored in the reservoir D3 and then fed into the cryogenic part of the process.

[0106] As explained with respect to the embodiment of the invention shown in FIG. 1, the pressure ratio of at least three times the suction pressure in the container D2 generated by the pump P1 leads to a similar, only slightly lower pressure ratio in the work-performing X1, which is a preferred working range for a work-performing expander. In addition, the inlet pressure of the work expander X1 can be kept below a pressure of 100 bar, which enables a cost-effective mechanical construction. In addition, the increased pressure generated by the pump P1 ensures that the work expander X1 receives an inlet pressure that is significantly above the critical pressure of the fluid, and thus avoids two-phase effects within the fluid. In embodiments of the invention shown in FIGS. 1 to 9, the refrigerant is used in the process for two processes, the natural gas condensing process in the cryogenic region and the process of recovering the waste heat produced by the gas turbine to drive the refrigerant compression process. Further improvements can be made in the present invention in order to improve the performance of the present invention. For example, the power of the work expander X1 could be increased by additionally firing an additional heat source into the flue gas channels of the gas turbine GT1. The work-performing expansion carried out by the work-performing expander X1 can be divided into successive steps, with or without the need to reheat the working fluid as desired.

[0107] In other embodiments of the invention, the shaft power generated by the work expander X1 could be used to drive other processes, such as a power generator, a feed gas compression, a terminal flash gas compression, any type of refrigerant compression or any other service that requires power.

[0108] The entire cooling system will have at least one refrigerant consisting of either a pure component or a mixture of components, wherein the refrigerant in one embodiment of the invention can be at least partially condensed at ambient temperature. In one embodiment of the invention, the permissible refrigerant components could include nitrogen and light paraffinic or olefinic hydrocarbons of C1 to C5 (such as CH4, C2H4, C2H6, C2H6, C3H6, C3H8, iC4H10, nC4H10, nC4H10, iC5H12, nC5H12, nC5H12, etc.). The cooling system can also include more than one circuit, wherein the additional circuits are pure refrigerant circuits and/or mixed refrigerant circuits and/or gas expansion circuits.

[0109] FIG. 4 is an embodiment of the present invention using a dual mixed refrigerant configuration (DMR) with three coil-wound heat exchangers (CWHEs) in the cryogenic region and a single gas turbine GT1 used for both mixed refrigerant circuits. As shown in FIG. 6, the configuration decouples a high-pressure compressor C2 from the low-pressure compressors C1A, C1B, which are driven by a common shaft, which is driven by the gas turbine GT1. This embodiment of the present invention also eliminates the need for a transmission that would be required to operate the compressor C2 at a higher pressure and at a higher operating speed if the compressor C2 has a capacity similar to that of the compressor C1A or C1B.

[0110] FIG. 5 is an embodiment of the present invention using a dual mixed refrigerant configuration (DMR) with three coil-wound heat exchangers (CWHEs) in the cryogenic part, wherein the compressors C1A and C1B are driven by independent gas turbines GT1A and GT1B, wherein the waste heat of the two gas turbines GT1A and GT1B is used in the heat exchangers E4A and E4B to superheat the liquid fed into the work machines X1. An advantage of the embodiment of the invention shown in FIG. 5 is the ability to achieve a higher power of the work expander X1 for driving the compressor C2.

[0111] FIG. 6 is an embodiment of the present invention using a C3MR configuration (propane-precooled mixed refrigerant) with a single coil-wound heat exchanger (CWHEs) in the cryogenic part. In FIG. 8, the compressors C1A and C1B are driven by independent power mechanisms, wherein the waste heat of the gas turbine GT1, which drives the compressor C1B, is used to superheat the fluid supplied to the work expander X1. The embodiment illustrated in FIG. 8 would use a suitable fluid, such as propane, propylene or other hydrocarbons, for the precooling process. Alternatively, as shown in FIG. 7, the compressors C1A and C1B can be driven by a common gas turbine GT1.

[0112] In other embodiments of the invention in which the cooling system includes more than one circuit, the additional circuits can be pure refrigerant circuits, mixed refrigerant circuits and/or gas expansion circuits. In addition, in other configurations, one or more gas turbines can be operated in parallel or in series. FIGS. 8 and 9 illustrate, for example, an alternative application of the present invention for a gas condensing process with a two-stage cryogenic method. In the embodiments shown in FIGS. 8 and 9, a mixed refrigerant circuit is used for precooling and condensing and a gas expansion process is used for supercooling the natural gas in separate stages of the cryogenic process.

[0113] In accordance with a first aspect, the present invention comprises a method for separating waste heat produced in a gas condensing process, comprising condensing a gas by a heat exchange process using a refrigerant fluid, compressing the spent refrigerant fluid from the condensing process by a method that produces excess heat, condensing at least a part of the compressed refrigerant fluid, pumping a part of the condensed compressed refrigerant fluid to a higher pressure, heating the part of the condensed compressed refrigerant fluid at a higher pressure by collecting the excess heat produced by the compression of the spent refrigerant fluid, whereby the part of the compressed refrigerant fluid is superheated at a higher pressure, and using the superheated compressed refrigerant fluid to carry out a mechanical process.

[0114] In accordance with a second aspect, a method for recovering waste heat produced in a gas condensing process, according to the first aspect is provided, furthermore comprising the mechanical process representing a further compression of the compressed refrigerant fluid.

[0115] In accordance with a third aspect, a method for recovering waste heat produced in a gas condensing process, according to the first aspect is provided, wherein the mechanical process is furthermore the operation of a work expander.

[0116] In accordance with a fourth aspect, a method for recovering waste heat produced in a gas condensing process, according to the third aspect is provided, furthermore comprising heating the part of the condensed compressed refrigerant fluid at a higher pressure by heat exchange with the fluid discharged by the work expander.

[0117] In accordance with a fifth aspect, a method for recovering waste heat produced in a gas condensing process, according to the fourth aspect is provided, wherein the fluid from the work expander used in heat exchange is furthermore combined with the condensed compressed refrigerant fluid.

[0118] In accordance with a sixth aspect, a method for recovering waste heat produced in a gas condensing process, according to the third aspect is provided, furthermore comprising the mechanical process representing a further compression of the compressed refrigerant fluid.

[0119] In accordance with a seventh aspect, a method for recovering waste heat produced in a gas condensing process, according to the sixth aspect is provided, furthermore comprising the further compression refrigerant fluid being the refrigerant fluid in the condensing step.

[0120] In accordance with an eighth aspect, a method for recovering waste heat produced in a gas condensing process, according to the first aspect is provided, furthermore comprising the mechanical method generating electrical energy.

[0121] In accordance with a ninth aspect, a method for recovering waste heat produced in a gas condensing process, according to the first aspect is provided, furthermore comprising heating the part of the condensed compressed refrigerant fluid at a higher pressure, auxiliary firing of an additional heat source into the collected excess heat produced by the compression of the spent refrigerant fluid.