A process for gasifying LNG to generate electricity at low temperatures

Abstract

The present invention describes a process for gasifying liquefied natural gas (LNG) to generate electricity, a process that operates efficiently at low temperatures.

Description

[Technical Field]

[0001] (Technical field of the invention) The present invention finds application in the fields of liquefied natural gas (LNG) regasification and energy recovery. [Background technology]

[0002] (Background technology) Organic Rankine Cycle Organic fluid Rankine cycles (ORCs) are widely used in geothermal fields and in applications using biomass and waste heat recovery from industrial processes. The possibility of selecting the working fluid from among dozens of candidate fluids allows for efficient thermodynamic cycles to be achieved even at low source temperatures and low heat availability.

[0003] Also, by selecting a fluid with a low boiling point, it is possible to reach temperatures lower than room temperature, and it is possible to achieve a concentration cycle (or condensation cycle) at extremely low temperatures, without the problem of freezing or excessively high vacuum pressure.

[0004] Between 1965 and 2013, many patents were issued on ORCs adapted for LNG regasification (ORMAT, RG JACKSON, Reickichi Nozawa, Fluor, Exxon Mobil).

[0005] Also recently, Saipem has published its own patent for an ORC cycle that operates on a single fluid produced (or formed or manufactured) starting from LNG and LPG (WO2020 / 075112A1).

[0006] Based on a high-boiling working fluid (IMR), it requires the use of a high-temperature heat source and is designed to maximize mechanical power. Waste heat can be extracted from the source to vaporize the LNG stream (and simultaneously cool the fluid).

[0007] This idea is advantageous because it uses fuel gently without direct thermal impact on the environment. It ensures continuous power generation independent of environmental conditions. Furthermore, the IMR formulation is designed to take full advantage of the fumes involved in vaporizing the LNG stream. Meanwhile, a simple cycle is used, i.e., a cycle consisting of a single machine (expander) for expanding the working fluid. Summary of the Invention [Problem to be solved by the invention]

[0008] However, the use of fuel has the drawback of using a non-renewable source and also involves the release of carbon dioxide into the atmosphere (unless the ORC cycle is combined with an expensive CO2 fixation system).

[0009] The ever-increasing sensitivity to environmental pollution associated with greenhouse gas emissions has led to a market that is interested in solutions that do not involve the use of fuel.

[0010] Inverse Mixed Refrigerants (IMR) are readily available, inexpensive fluids with thermodynamic properties similar to those of LNG, which are fully concentrated at LNG storage temperatures only at relatively high pressures, but which cannot be fully vaporized at room temperature (except at pressures slightly higher than the concentration pressure).

[0011] Between these two constraints, the expansion ratio available for generating electricity is significantly reduced to the point where it is only slightly adapted for use in the presence of room temperature sources alone.

[0012] Prior art document (US Pat. No. 3,479,832) discloses a process for vaporizing liquefied natural gas, which separates the liquid (28, 44) and gas (26, 4, 42) mono-component-rich fractions, and generates energy by using working fluids with various compositions. [Means for solving the problem]

[0013] (Summary of the Invention) The inventors of this patent application have developed a process for gasifying liquefied natural gas (LNG) to generate electricity. The process uses a working fluid obtained by mixing liquefied natural gas (LNG) with liquefied petroleum gas (LPG). In particular, the working fluid is adapted to operate at low temperatures.

[0014] (Object of the invention) As a first object, the present invention describes a process (or treatment or method) for gasifying liquefied natural gas (LNG) to generate electricity (or generate power). [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a process (or treatment or method) for gasifying liquefied natural gas (LNG) to generate electricity (or for generating electricity) (as described in prior art document (WO2020 / 075112A1)). [Figure 2] FIG. 2 is a diagram illustrating a process (or procedure or method) according to a first embodiment of the present invention. [Figure 3] FIG. 3 is a diagram illustrating a process (or procedure or method) according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] (Detailed Description of the Invention) IMR - Inverse Mixed Refrigerant (or Inverse Mixed Refrigerant or Inverse Mixed Refrigerant or Inverse Mixed Refrigerant) The IMR working fluid is a mixture (or liquid mixture) of liquids. In particular, such fluids are obtained by blending commercial liquefied petroleum gas (LPG) and commercial liquefied natural gas (LNG).

[0017] The term "commercial liquefied petroleum gas (LPG)" means a fuel whose characteristics are well defined due to its common use in civil and industrial sectors and which has the following properties: Vapor pressure at 100°F The minimum temperature (atmospheric pressure) at which a hypothetical sample (or specimen) of 95 vol% (volume % or volume % or volume %) evaporates (or vaporizes), preferably by heating according to a precise method. Mole % content of molecules with a number of carbon atoms greater than 4 (which for the purposes of this invention actually also includes hydrocarbons with 7 or >7 carbon atoms)

[0018] It is known that liquefied petroleum gas (LPG) is blended with crude oil and separated from the crude oil by refining in a topping column.

[0019] Liquefied petroleum gas (LPG) is produced in various refining processes, for example, cracking (or decomposition) produces LPG as a by-product.

[0020] For the purposes of the present invention, liquefied petroleum gas (LPG) is preferably defined as a flammable fluid (or fluid) whose characteristics fall within the limits defined in the table below.

[0021] [Table 1]

[0022] (1) Maximum temperature (temperature at atmospheric pressure at which 95% of the volume of the sample under test evaporates)

[0023] (2) Content of molecules with at least 5 carbon atoms

[0024] The term "commercial liquefied natural gas (LNG)" means a hydrocarbon fluid, primarily in the liquid phase, obtained by concentrating (or condensing) natural gas at a temperature low enough to maintain its liquid form even at atmospheric pressure.

[0025] Natural gas is known to be composed primarily of methane and light hydrocarbons (rarely hydrocarbons having a number of carbon atoms greater than 5 (>5)), and may also contain nitrogen in varying proportions.

[0026] For purposes of this invention, "IMR" is defined as any mixture of liquefied natural gas (LNG) and liquefied petroleum gas (LPG) obtained by mixing 1 volume of liquefied natural gas (LNG) with a quantity of LPG (0.25 to 1.2 volumes of liquefied natural gas (LNG)).

[0027] A process (or treatment or method) for preparing IMR hydraulic fluids (or hydraulic fluids or working fluids) is described in detail in patent application WO2020 / 075112A1 (Saipem SpA), the contents of which are incorporated by reference in their entirety.

[0028] Liquefied Natural Gas (LNG) gasification line For the purposes of this invention, a liquefied natural gas (LNG) gasification line starts from a storage tank (or storage tank) for liquefied natural gas (LNG in Figures 2 and 3), where it is gasified and supplied to the network (NG in Figure 2).

[0029] In particular, gasification is carried out in several heating processes (or heating steps), which increases the complexity of the system proportionately, although this is due to the increased efficiency of the process.

[0030] According to a preferred embodiment of the present invention, three heating processes (or heating steps) of liquefied natural gas are provided: In the heating processes, a flow (or stream) of liquefied natural gas exchanges heat by obtaining heat from one or more flows (or streams).

[0031] More specifically, according to the embodiment shown in Figures 2 and 3, a liquefied natural gas flow (40) leaves a dedicated tank (LNG) and is subjected to a first heating step, thus obtaining a partially regasified flow (41). The flow (41) is further heated during a second heating step, thus obtaining a further regasified flow (42). The flow (42) is then subjected to a third heating step, resulting in a fully regasified flow (43).

[0032] LIMR Cycle - Low Temperature Inversed Mixed Refrigerant The LIMR cycle is implemented using a first working fluid (1MF or LIMR) and includes an expander (EX in Figure 2). One or more low-temperature heat sources (H1, H2 in Figure 2) and tanks (V1, V2, and V3 in Figure 2) contain the second or third working fluid, respectively.

[0033] In particular, the first tank (V1) contains a quantity of a second working fluid (2MF), which in a preferred embodiment of the present invention is an inverse mixed refrigerant (IMR).

[0034] The second tank (V2) and the third tank (V3) contain a certain amount of a third working fluid (or third hydraulic fluid or third working fluid), which in a preferred embodiment of the present invention is liquefied natural gas (LNG).

[0035] With regard to the expander (or expander) (EX), the expander (EX) is preferably a turbine for generating electricity (or for generating electricity).

[0036] In accordance with a first object of the present invention, a process (or treatment or method) for generating electricity (or generating power) by gasifying liquefied natural gas (LNG) is described, which includes the following steps (or processes) 1 to 15:

[0037] 1) subjecting a flow (1) of a first working fluid (1MF) in gas phase to a first cooling step (or first cooling step), thereby obtaining a cooled flow (2) of said first working fluid (1MF);

[0038] 2) sending the cooled flow (2) of the first working fluid (1MF) to a first tank (V1), the first tank (V1) containing a quantity of a second working fluid (2MF);

[0039] 3) Separating the first enriched fraction (3) and the first gas portion (6).

[0040] 4) subjecting said first gas portion (6) to a second cooling step (or second cooling step), thereby obtaining a first concentrated portion (7).

[0041] 5) sending said first concentrated portion (7) to a second tank (V2), said second tank (V2) containing a quantity of a third working fluid (3MF);

[0042] 6) Separating the second enriched fraction (8) and the second gas portion (12).

[0043] 7) subjecting said second gas portion (12) to a third cooling step, thereby obtaining a final concentrated portion (13).

[0044] 8) sending said final concentrated portion (13) to a third tank (V3), said third tank (V3) containing a quantity of said third working fluid (3MF), thereby obtaining a third concentrated fraction (14);

[0045] 9) subjecting the first concentrated fraction (3) to a pumping step (or pumping step), thereby obtaining a pumped first concentrated fraction (4), and subjecting the pumped first concentrated fraction (4) to a heat exchange step (or heat exchange step), thereby obtaining the first concentrated fraction (4). No. 1 working fluid 1MF obtaining a first portion (5) for mixing with

[0046] 10) subjecting the second concentrated fraction (8) to a pumping step (or pumping step), thereby obtaining a pumped second concentrated fraction (9), and 2 Heat exchange process (or 2a heat exchange step) to obtain a pumped second concentrated fraction (10) at a higher temperature, and 3 Heat exchange process (or Third a heat exchange step), thereby No. 1 working fluid 1MF obtaining a second portion (11) for mixing with

[0047] 11) subjecting said third concentrated fraction (14) to pumping (or pumping process or pumping step), thereby obtaining a pumped third concentrated fraction (15), and 2 subjecting the pumped third concentrated fraction (16) to heat exchange, thereby obtaining a higher temperature pumped third concentrated fraction (16) and 3 a step of subjecting the mixture to heat exchange, thereby No. 1 working fluid 1MF obtaining a third portion (17) for mixing with

[0048] 12) In the mixer M, the first working fluid 1MF mixing the first portion (5), the second portion (11) and the third portion (17) to mix the first working fluid 1MF Obtain the initial flow (or initial flow) (18), step

[0049] 13) The first working fluid 1MF heating the initial flow (18) of the first working fluid (H) with a low temperature second heat source (H2), thereby 1MF obtaining a heated flow (19) of

[0050] 14) The first working fluid 1MFand expanding the heated flow (19) in a power expander (or power expander) (EX), thereby generating an expanded and cooled first working fluid (19). 1MF The flow (20) is obtained.

[0051] 15) the expanded and cooled first working fluid 1MF a step of heating the flow (20) of the first working fluid (20) of step 1) above by a low temperature first heat source (H1), thereby generating the first working fluid (20) of step 1) in gas phase. 1MF To obtain the flow (1),

[0052] According to an embodiment of the present invention, during step 1) the flow (1) of the first working fluid is mainly in the gas phase.

[0053] According to a particular embodiment of the invention, during step 3) (or step 3), a first concentrated fraction (3) is obtained by mixing the cooled flow (2) (liquid fraction) with the second working fluid 2MF (contained in the first tank (V1)) as described above.

[0054] According to an embodiment of the present invention, during step 4) the first concentrated portion (7) obtained above is not fully concentrated, but only partially concentrated.

[0055] According to another aspect of the invention, during step 6) (or step 6), the liquid fraction (or liquid fraction) of said partially concentrated (or condensed) first concentrated portion (or first partially concentrated portion) (7) is mixed with said third working fluid (3MF) contained in a second tank (V2), thereby obtaining a second concentrated fraction (8).

[0056] According to an embodiment of the present invention, the third concentrated fraction (16) that is concentrated (or condensed) at high temperature and pumped during step 11) (or step 11) may not be concentrated (or condensed).

[0057] For purposes of the present invention, step 13) (or step 13) and step 15) (or step 15) are carried out using a low temperature heat source (or heat source).

[0058] In particular, low-temperature heat sources may be the atmosphere, seawater, low-temperature solar heat, waste heat from low-temperature thermodynamic cycles, recovered heat from processes and / or recovered heat from low-temperature machinery. Here, "seawater" refers to pumped seawater (suitably treated to remove sediments) or, more generally, to environmental waters obtained from rivers, canals, wells, natural basins (e.g., lakes), and artificial basins.

[0059] Generally, a low temperature source is one having a temperature of about 0°C to about 55°C.

[0060] When reference is made to a flow having a "higher" temperature or "higher" pressure, it means that such flow has been subjected to a heating or pumping step in which the temperature or pressure has been increased compared to before.

[0061] With particular reference to the drawing shown in FIG. 2, a first working fluid flow (1) is cooled during a heat exchange process (step).

[0062] The cooling determines the degree of compression (or concentration or condensation) of the heavy fraction (3) of the first working fluid, which is separated inside the first tank (V1) containing the second working fluid (2MF).

[0063] Heavy fraction means a liquid fraction that has a chemical composition similar to that of the IMR, where "similar" means a variation in molecular weight of about 40% or so.

[0064] The heavy fraction (3) is pumped by a first pump (P1), thus obtaining a pumped heavy fraction (4), which, after a heating step, forms a first portion (5) to be mixed with a first working fluid.

[0065] The same cooling also determines the separation of a first gas portion (6), which is subjected to a further heat exchange step, from which in particular a further cooled first gas portion (7) is obtained.

[0066] Cooling determines the degree of further compression (or concentration or condensation) of the heavy fraction (8), which is separated inside a second tank (V2) containing liquefied natural gas (LNG) as a third working fluid (3MF).

[0067] The heavy fraction (8) is pumped by a second pump (P2), thus obtaining a pumped heavy fraction (9). The heavy fraction (9) is subjected to a first heating process or heating step to provide a preheated flow (10), which is then subjected to a second heating process or heating step to form a second portion (11) for mixing with the first working fluid.

[0068] The same cooling also determines the separation of a second gas portion (12), which is then subjected to a further cooling step, thus obtaining a final concentrated portion (13).

[0069] The final concentrated portion (13) is sent to a third tank (V3) containing liquefied natural gas (LNG) as a third working fluid (3MF).

[0070] The outflow (or effluent) from the third tank (V3) is then subjected to a first heat exchange process (or step) and a subsequent second heat exchange process (or step), thus obtaining a third portion (or third mixed portion or third mixed part) (17) for mixing with the first working fluid.

[0071] Regarding the third portion (or third mixed portion or third mixed part) (17) for mixing with the first working fluid, the third portion (17) is then mixed with the first portion (or first mixed portion or first mixed part) and second portion (or second mixed portion or second mixed part) (corresponding to flows 5 and 11 in FIG. 2, respectively) inside a mixer (M in FIG. 2).

[0072] The working fluid (18) (LIMR) obtained after mixing inside the mixer (M) is then subjected to a heating process (or heating step) using a second heat source (H2 in FIG. 2) of lower temperature, thus obtaining a heated flow (19). The flow (19) is then expanded inside an expander (EX in FIG. 2) to generate (or form or generate) energy.

[0073] After expansion, the expanded flow (20) is subjected to a heating step using a low-temperature first heat source (H1 in FIG. 2), resulting in an expanded and heated flow (1).

[0074] The flow (1) thus expanded and heated can then re-enter the cycle described above as the first working fluid (1MF).

[0075] For purposes of the present invention, a flow (or stream) of liquefied natural gas (40) is gasified in heat exchange with one or more of the flows (or streams) described above.

[0076] More specifically, the flow (40) of liquefied natural gas is subjected to the following first, second and third heat exchanges. ·1st heat exchange The first heat exchange corresponds to step 7) described above, which results in a flow (41) of partially regasified liquefied natural gas. ·Second heat exchange The second heat exchange corresponds to step 4) and step 10) and step 11) described above. The second heat exchange results in a further regasified liquefied natural gas flow (42). ·Third heat exchange The third heat exchange corresponds to steps 1), 9), 10), and 11), described above. The third heat exchange results in a flow (43) of fully regasified natural gas.

[0077] For example, the embodiment of the present invention shown in Figure 3 may further include a third low-temperature heat source (H3) during the first heat exchange process (or step), which heats the following by means of an intermediate carrier fluid: A flow of further heated natural gas (42) (after the second heating step) The pumped first concentrated fraction (or first concentrated fraction) (4) A hot pumped second concentrated fraction (or second concentrated fraction) (10) The hot pumped third concentrated fraction (or third concentrated fraction) (16)

[0078] As shown in the diagram of Figure 3, in practice, the carrier fluid flow (50) is pumped by a fourth pump (P4) to obtain a higher pressure flow (51).

[0079] This high pressure flow (51) releases heat (or calories) during the first heat exchange step, thus obtaining a cooled carrier fluid flow (52).

[0080] From the above description, the benefits (or advantages) provided by the process (or treatment or method) of the present invention will be immediately apparent to those skilled in the art.

[0081] In particular, such processes (or treatments or methods) utilize a low-temperature heat source, thereby meaning a room temperature source (such as seawater or a natural or artificial reservoir).

[0082] With respect to the process (or treatment or method) and power cycle (or power cycle) described in patent application WO2020 / 075112, the power cycle (or power cycle) of the present invention has the same effect (or efficacy or efficiency) and the same simplicity of the system.

[0083] Advantageously, the cycle of the present invention can also be operated (or run or operated) at low temperatures.

[0084] The cycle of the present invention does not require fuel, and therefore the process does not rely on non-renewable energy sources and does not involve the generation of carbon dioxide (CO2). The disclosure of this specification may include the following aspects. (Aspect 1) 1. A process for gasifying liquefied natural gas (LNG) to generate electricity, the process comprising: 1) subjecting a flow (1) of a first working fluid 1MF in gas phase to a first cooling step, thereby obtaining a cooled flow (2) of said first working fluid 1MF; 2) sending the cooled flow (2) of the first working fluid 1MF to a first tank V1, the first tank V1 containing a quantity of a second working fluid 2MF; 3) separating a first concentrated fraction (3) and a first gas portion (6) from said first tank V1; 4) subjecting said first gas portion (6) to a second cooling step, thereby obtaining a first concentrated portion (7); 5) sending the first concentrated portion (7) to a second tank V2, the second tank V2 containing a quantity of a third working fluid 3MF; 6) separating a second concentrated fraction (8) and a second gas portion (12) from said second tank V2; 7) subjecting said second gas portion (12) to a third cooling step, thereby obtaining a final concentrated portion (13); 8) sending said final concentrated portion (13) to a third tank V3, said third tank V3 containing a quantity of said third working fluid 3MF, thereby obtaining a third concentrated fraction (14); 9) subjecting said first concentrated fraction (3) to a pumping step, thereby obtaining a pumped first concentrated fraction (4), and subjecting said first concentrated fraction (3) to a heat exchange step, thereby obtaining a first portion (5) for mixing with said working fluid; 10) subjecting said second concentrated fraction (8) to a pumping step, thereby obtaining a pumped second concentrated fraction (9), and subjecting it to a first heat exchange step, thereby obtaining a second concentrated fraction (10) at a higher temperature and pressure, and subjecting it to a second heat exchange step, thereby obtaining a second portion (11) for mixing with said working fluid; 11) subjecting the third concentrated fraction (14) to pumping, thereby obtaining a pumped third concentrated fraction (15), and subjecting it to a first heat exchange, thereby obtaining a higher temperature pumped third concentrated fraction (16), and subjecting it to a second heat exchange, thereby obtaining a third portion (17) for mixing with the working fluid; 12) mixing the first portion (5), the second portion (11) and the third portion (17) in a mixer M to mix the first working fluid, thereby obtaining an initial flow (18) of the first working fluid; 13) heating the initial flow (18) of the first working fluid by a low temperature second heat source H2, thereby obtaining a heated flow (19) of the first working fluid; 14) expanding the heated flow (19) of first working fluid in a power expander EX, thereby obtaining an expanded and cooled flow (20) of first working fluid; 15) heating the expanded and cooled first working fluid flow (20) by a first heat source H1 at low temperature, thereby obtaining the first working fluid flow (1) in gas phase of step 1); In the process, During step 7), heat is exchanged with the liquefied natural gas flow (40), thereby obtaining a partially regasified natural gas flow (41), Between steps 4), 10) and 11), heat exchange b) is carried out with said partially regasified natural gas flow (41), thereby obtaining a further regasified natural gas flow (42), Between steps 1), 9), 10) and 11), a third heat exchange is carried out with said further regasified natural gas flow (42), thereby obtaining a fully regasified flow (43); The second working fluid 2MF is a fluid obtained by adding a certain amount of liquefied petroleum gas (LPG) to a certain amount of liquefied natural gas (LNG), and the amount is such that 0.25 to 1.2 volumes of liquefied petroleum gas (LPG) are added to 1 volume of the liquefied natural gas (LNG); The third working fluid 3MF is liquefied natural gas (LNG); process. (Aspect 2) 2. The process of embodiment 1, wherein a low temperature heat source is used during steps 13) and 15). (Aspect 3) 3. The process of any one of the preceding claims, further comprising a third heat source (H3) of low temperature during the heat exchange step of step 1). (Aspect 4) Aspect 4. The process of any of aspects 1 to 3, wherein the heat exchange with the lower temperature third heat source (H3) is bypassed by a carrier fluid.

Claims

1. 1. A process for gasifying liquefied natural gas (LNG) to generate electricity, the process comprising: １） subjecting a flow (1) of a first working fluid 1MF in gas phase to a first cooling step, thereby obtaining a cooled flow (2) of said first working fluid 1MF; ２） sending the cooled flow (2) of the first working fluid 1MF to a first tank V1, the first tank V1 containing a quantity of a second working fluid 2MF; ３） separating a first concentrated fraction (3) and a first gas portion (6) from said first tank V1; ４） subjecting said first gas portion (6) to a second cooling step, thereby obtaining a first concentrated portion (7); ５） sending said first concentrated portion (7) to a second tank V2, said second tank V2 containing a quantity of a third working fluid 3MF; ６） separating a second concentrated fraction (8) and a second gas portion (12) from said second tank V2; ７） subjecting said second gas portion (12) to a third cooling step, thereby obtaining a final concentrated portion (13); ８） sending said final concentrated portion (13) to a third tank V3, said third tank V3 containing a quantity of said third working fluid 3MF, thereby obtaining a third concentrated fraction (14); ９） subjecting said first concentrated fraction (3) to a pumping step, thereby obtaining a pumped first concentrated fraction (4), and subjecting said first concentrated fraction (3) to a heat exchange step, thereby obtaining a first portion (5) for mixing with said first working fluid 1MF; １０） subjecting said second concentrated fraction (8) to a pumping step, thereby obtaining a pumped second concentrated fraction (9), and subjecting it to a second heat exchange step, thereby obtaining a second concentrated fraction (10) at a higher temperature and pressure, and subjecting it to a third heat exchange step, thereby obtaining a second portion (11) for mixing with said first working fluid 1MF; １１） subjecting said third concentrated fraction (14) to pumping, thereby obtaining a pumped third concentrated fraction (15), and subjecting it to a second heat exchange, thereby obtaining a pumped third concentrated fraction (16) of higher temperature, and subjecting it to a third heat exchange, thereby obtaining a third portion (17) for mixing with said first working fluid 1MF; １２） mixing the first portion (5), the second portion (11) and the third portion (17) in a mixer M to mix the first working fluid 1MF, thereby obtaining an initial flow (18) of the first working fluid 1MF; １３） heating the initial flow (18) of the first working fluid 1MF by a second heat source H2 between 0°C and 55°C, thereby obtaining a heated flow (19) of the first working fluid 1MF; １４） Expanding said heated flow of first working fluid 1MF (19) in a power expander EX, thereby obtaining an expanded and cooled flow of first working fluid 1MF (20); １５） Heating the expanded and cooled flow (20) of first working fluid 1 MF by a first heat source H1 at 0°C to 55°C, thereby obtaining a flow (1) of first working fluid 1 MF in the gas phase of step 1). In the process, During step 7), heat is exchanged with a flow of liquefied natural gas (40), thereby obtaining a flow of partially regasified natural gas (41), Between steps 4), 10) and 11), heat exchange b) is carried out with said partially regasified natural gas flow (41), thereby obtaining a further regasified natural gas flow (42), Between steps 1), 9), 10) and 11), a third heat exchange is carried out with said further regasified natural gas flow (42), thereby obtaining a fully regasified flow (43), The second working fluid 2MF is a fluid obtained by adding a certain amount of liquefied petroleum gas (LPG) to a certain amount of liquefied natural gas (LNG), the amount being such that 0.25 to 1.2 volumes of liquefied petroleum gas (LPG) are added to 1 volume of the liquefied natural gas (LNG); The third working fluid 3MF is liquefied natural gas (LNG), process.

2. 10. The process of claim 1, wherein a heat source of 0°C to 55°C is used during steps 13) and 15).

3. 3. The process according to claim 1 or 2, further comprising using a third heat source (H3) at 0°C to 55°C during the heat exchange step of step 1).

4. The process according to any one of claims 1 to 3, wherein the heat exchange with the third heat source (H3) between 0°C and 55°C is bypassed by a carrier fluid.

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