EP4230937A1 - Method and system for generating a liquefied hydrocarbon product - Google Patents

Abstract

A method for producing a liquid hydrocarbon product (LNG) is proposed, in which a pure substance refrigerant circuit (10) operated with a pure substance refrigerant and having a first heat exchanger arrangement (E1, E2), and a mixed refrigerant circuit (20) operated with a mixed refrigerant and having a second heat exchanger arrangement (E3, E4) are provided, at least part of the hydrocarbon charge (NG) is first pre-cooled using the pure substance refrigerant circuit (10) and then liquefied using the mixed refrigerant circuit (20) to form the liquid hydrocarbon product (LNG), into the first Heat exchanger arrangement (E1, E2) several pure substance refrigerant part streams (16, 22, 32, 44) of the pure substance refrigerant are fed in at different feed pressure levels and at different feed temperature levels, the pure substance refrigerant part streams (16, 22, 32, 44) by expanding starting from a common pre-expansion pressure level and different pre-expansion temperature levels are brought to the feed pressure levels and feed temperature levels, and the pre-expansion temperature levels are selected in such a way that the pure component refrigerant flows (16, 22, 32, 44) are in the supercooled state at the feed temperature levels. A corresponding system is also the subject of the invention.

Description

The present invention relates to a process and a plant for producing a liquefied hydrocarbon product according to the respective preambles of the independent patent claims.

background

Processes and systems for the liquefaction of natural gas are known and extensively described in the specialist literature, for example in the article " Natural Gas" in Ullmann's Encyclopedia of Industrial Chemistry, online publication July 15, 2006, DOI: 10.1002/14356007.a17_073.pub2 , especially Section 3, "Liquefaction", or in Wang and Economides, " Advanced Natural Gas Engineering", Gulf Publishing Company 2010, DOI: 10.1016/C2013-0-15532-8, especially Chapter 6, "Liquefied Natural Gas (LNG) ".

From the U.S. 3,763,658 B2 discloses a process for liquefying a hydrocarbon feedstock which can be used in particular in natural gas liquefaction processes. In this method, a mixed refrigerant circuit is used for the liquefaction and supercooling of the hydrocarbon feed, while a pure substance refrigerant circuit is also provided, by means of which both the hydrocarbon feed to be liquefied is pre-cooled and the mixed refrigerant of the mixed refrigerant circuit is pre-cooled and partially liquefied. Such a method is particularly suitable for natural gas liquefaction processes with an annual capacity of between 1 and 6 million tons of liquefied natural gas.

From the DE 10 2009 018 248 A1 there is also known a method for liquefying a hydrocarbon feed using a mixed refrigerant cycle. The mixed refrigerant is liquefied therein after compression by means of a pure substance refrigerant circuit. The liquefied blended refrigerant is used to liquefy the hydrocarbon feedstock and is vaporized in the process. The vaporized mixed refrigerant is used to cool the hydrocarbon charge before it is actually liquefied and then returned to the compression stage. The hydrocarbon charge is therefore not pre-cooled here by means of the pure substance refrigerant circuit, but rather by means of the mixed refrigerant circuit.

Corresponding liquefaction processes require a comparatively large amount of equipment and space. The object of the present invention is therefore to provide improvements over the prior art in this sense.

Disclosure of Invention

Against this background, the invention proposes a method and a plant for producing a liquefied hydrocarbon product with the respective features of the independent patent claims. Refinements of the invention are the subject matter of the dependent claims and the following description.

The present invention can be used in particular in connection with the liquefaction of natural gas after suitable processing, but is also suitable for the liquefaction of other hydrocarbon mixtures, in particular methane-rich hydrocarbon mixtures with a methane content of more than 80%, or possibly corresponding pure substances. These are referred to generically herein as "hydrocarbon feeds". A hydrocarbon feed is therefore in particular processed natural gas, which does not have to consist exclusively of hydrocarbons, but can also contain nitrogen and other gas components such as noble gases (especially helium).

In general, mixed refrigerants made of different hydrocarbon components and nitrogen can be used in natural gas liquefaction. For example, one, two or three mixed refrigerant circuits can be used (single mixed refrigerant, SMR; dual mixed refrigerant, DMR; mixed fluid cascade, MFC). Mixed refrigerant circuits with propane pre-cooling (C3MR) are also known. The present application can relate in particular to the latter case, in which case propane is used as the pure refrigerant.

The present application uses the terms “pressure level” and “temperature level” to characterize pressures and temperatures, which is intended to express that corresponding pressures and temperatures in a corresponding system do not have to be used in the form of exact pressure or temperature values. However, such pressures and temperatures typically range within certain ranges, for example ±10% around an average value. Corresponding pressure levels and temperature levels can be in disjoint areas or in areas that overlap one another. In particular, for example, pressure levels include unavoidable or expected pressure losses. The same applies to temperature levels.

A "heat exchanger" for use in the context of the present invention can be of any type which is conventional in the art. It is used for the indirect transfer of heat between at least two fluid flows, e.g. in counterflow to one another. In the latter case, it is a "counterflow heat exchanger". A corresponding heat exchanger can be formed from a single or several heat exchanger sections connected in parallel and/or in series, e.g. from one or more coiled heat exchangers or corresponding sections.

In addition to a counterflow heat exchanger, which can be designed in particular as a (brazed) fin-plate heat exchanger made of aluminum (Brazed Aluminum Plate-Fin Heat Exchanger, PFHE; designations according to the German and English edition of ISO 15547-2:3005), In the present invention, in particular, heat exchangers are also used, in which a fluid to be cooled is guided in corresponding lines (for example a tube bundle) through a jacket space into which a fluid used for cooling is expanded.

If a “pure substance refrigerant” is mentioned below, this is to be understood in particular as meaning a refrigerant that has more than 90 mole percent, in particular more than 95 mole percent or more than 99 mole percent, of a single component. The component can in particular be ethylene, ethane, propylene or propane. In contrast, a “mixed refrigerant” is characterized in particular by the fact that it has a number of components, none of which is contained in a content of more than 80 mole percent, in particular more than 70 mole percent or more than 60 mole percent. The components can be, in particular, nitrogen, methane, ethane, propane, butane and pentane and unsaturated equivalents of these compounds. In particular, however, such a mixed refrigerant can be propane-free or have propane in a content of at most 10 mole percent, in particular at most 5 mole percent or at most 1 mole percent.

Overall, the present invention proposes a method for producing a liquid hydrocarbon product using a gaseous hydrocarbon feed, in which a pure substance refrigerant circuit operated with a pure substance refrigerant, which has a first heat exchanger arrangement, and a mixed refrigerant cycle operated with a mixed refrigerant, which has a second heat exchanger arrangement, are provided and wherein at least a portion of the hydrocarbon feed is first pre-cooled using the pure refrigerant cycle and then liquefied to the liquid hydrocarbon product using the mixed refrigerant cycle.

In the first heat exchanger arrangement, several pure substance refrigerant partial flows of the pure substance refrigerant at different feed pressure levels and at different Feed-in temperature levels are fed in, with the pure substance partial refrigerant flows being brought to the feed-in pressure levels and feed-in temperature levels by expansion starting from a common pre-expansion pressure level and different pre-expansion temperature levels (these terms are used in particular to refer to the pressure or temperature levels immediately upstream of the expansion, which can take place in particular by means of suitable valves). The pre-expansion temperature levels are selected in such a way that the pure substance partial refrigerant flows are still in the supercooled state at the feed temperature levels. At least part of the mixed refrigerant of the mixed refrigerant circuit is also cooled by means of the pure substance refrigerant circuit.

The pre-cooling of the hydrocarbon charge and the refrigerant mixture is carried out in particular by means of two series-connected heat exchangers of the first heat exchanger arrangement in the pure refrigerant circuit. As already expressed in other words, these are cooled by feeding in supercooled pure refrigerant fractions or partial flows at different evaporation pressure levels, the different feed temperature levels. Up to the lowest pressure level, all pure refrigerant fractions or partial flows are supercooled, in particular by the evaporation of the next lower pure refrigerant pressure level or the corresponding pure refrigerant partial flow, to such an extent that the pure refrigerant fractions are still supercooled after their expansion in corresponding valves, with an extent of supercooling being advantageous configurations given below.

In one embodiment, a partial flow taken from the cold side of the first heat exchanger arrangement can also be further cooled, as explained below, using the mixed refrigerant circuit, so that it is also supercooled after corresponding expansion. The pre-cooling of the hydrocarbon charge and the mixed refrigerant using the first heat exchanger arrangement or the pure substance refrigerant can be carried out within the scope of the present invention, in particular in the supercritical state, in order to avoid the need for a separator between the two heat exchanger arrangements.

In the case of the one mentioned above DE 10 2009 018 248 A1 described liquefaction process, whose reference numbers are used in this paragraph, the cooling (in heat exchanger E7) and the liquefaction (in heat exchanger E8) take place in indirect heat exchange against the refrigerant mixture of a mixed refrigerant circuit. More precisely, the cooling (in heat exchanger E7) takes place in the heat exchange against the fully evaporated mixed refrigerant of the mixed refrigerant circuit. condensed Mixed refrigerant of the mixed refrigerant circuit is pre-cooled by means of a pure substance refrigerant circuit (comprising heat exchangers E1 to E4) and the composition of the mixed refrigerant and/or the compressor discharge pressure of the mixed refrigerant circuit are selected such that the refrigerant mixture is completely liquefied by the pure substance refrigerant circuit. As an alternative to this, a cooling of the mixture refrigerant in the heat exchangers E1 to E4 above its critical pressure also leads to a single-phase state downstream of the heat exchanger E4. The pure refrigerant circuit includes, among other things, the containers D1 to D5 and the jacket spaces of the heat exchangers E1 to E4. The inventory of pure liquid refrigerant contained therein (typically a flammable hydrocarbon from the group of ethylene, ethane, propylene or propane) may represent a safety risk for the entire system. The large devices D1 to D4 and E1 to E4 are usually brought individually to the construction site and cause high installation costs due to the time-consuming assembly.

With the present invention, the pure substance refrigerant circuit can be redesigned in such a way that a high degree of prefabrication can be achieved and the liquid inventory of refrigerant is significantly reduced.

By using supercooled pure refrigerant flows when feeding into the first heat exchanger arrangement, compact heat exchangers such as plate heat exchangers without phase separators can be used to feed the individual pure refrigerant flows in the pure refrigerant circuit according to one embodiment of the present invention.

The footprint of a plate heat exchanger solution for the pure refrigerant circuit decreases significantly compared to traditional solutions using kettle-type heat exchangers. In the same way, the hydrocarbon inventory in the pure substance refrigerant circuit decreases in the process described. Due to the lower hydrocarbon inventory and due to the fact that plate heat exchangers are usually built in cold boxes with welded flange connections, which significantly reduces the potential for leakage, the entire process can be implemented with less safety-related effort.

1. a) Verwendung von kompakten Plattenwärmetauschern als Mehrstromwärmetauscher im Reinstoffkältemittelkreislauf ist möglich.
2. b) Keine Phasentrenner an den Plattenwärmetauschern notwendig.
3. c) Geringere Anzahl an Wärmetauschern im Reinstoffkältemittelkreislauf.
4. d) Geringerer Platzbedarf für den Reinstoffkältemittelkreislauf.
5. e) Kein Abscheider für Kältemittelstrom oder Kohlenwasserstoffeinsatz notwendig.
6. f) Deutlich geringeres Kohlenwasserstoffinventar im Gesamtprozess.
7. g) Geringerer Sicherheitsaufwand, da weniger brennbare und explosive Kohlenwasserstoffe in flüssiger Form in der Anlage vorhanden.

The advantages that can be achieved in embodiments of the present invention can be summarized as follows:

1. a) It is possible to use compact plate heat exchangers as multi-flow heat exchangers in the pure refrigerant circuit.
2. b) No phase separators required on the plate heat exchangers.
3. c) Less number of heat exchangers in the pure refrigerant circuit.
4. d) Less space required for the pure refrigerant circuit.
5. e) No separator required for refrigerant stream or hydrocarbon feed.
6. f) Significantly lower hydrocarbon inventory in the overall process.
7. g) Lower safety requirements, as there are fewer combustible and explosive hydrocarbons in liquid form in the system.

All of the advantages mentioned lead to better economics of the overall process compared to known methods, for example according to U.S. 3,763,658 B2 . The total energy expenditure increases only slightly (less than 5%).

In one embodiment of the invention, at least part of the pure refrigerant is cooled in the first heat exchanger arrangement, with part of the pure refrigerant substreams being removed from the first heat exchanger arrangement at their pre-expansion temperature levels. In this case, the pure component refrigerant flows can be branched off in particular from a common flow of the pure component refrigerant, which is fed to the first heat exchanger arrangement on the warm side, in particular via intermediate removals from the plate heat exchangers used here and between them.

In one embodiment of the invention, part of the pure substance refrigerant cooled in the first heat exchanger arrangement is further cooled in the second heat exchanger arrangement, with the at least one of the pure substance refrigerant partial flows being formed at its pre-expansion temperature level using the pure substance refrigerant further cooled in the second heat exchanger arrangement. A bypass can be used for better controllability of the temperature, as in figure 1 explained.

In an alternative embodiment of the invention, part of the pure refrigerant cooled in the first heat exchanger arrangement can be expanded to obtain a two-phase flow, the two-phase flow being subjected to phase separation to obtain a gas phase and a liquid phase, and the gas phase and the liquid phase then being fed to the first heat exchanger arrangement become. This represents an alternative to cooling in the second heat exchanger arrangement, so that the latter can be used in a modified manner. The decoupling of the pure substance refrigerant circuit from the mixed refrigerant circuit and the simpler design of the heat exchanger arrangement used in the latter is also advantageous here.

In one embodiment of the invention, the pure component refrigerant flows are each heated in the first heat exchanger arrangement from the feed temperature level to an extraction temperature level and to the extraction temperature level of the first Removed heat exchanger assembly. In particular, they are vaporized during this heating. In particular, the feed-in temperature levels and the removal temperature levels of the pure component refrigerant flows each enclose temperature intervals, with the temperature intervals for the pure component refrigerant flows not overlapping one another. This corresponds in particular to the subcooling already mentioned above due to the evaporation of the respectively next lower pure substance refrigerant pressure level or the corresponding pure substance refrigerant partial flow.

In refinements of the invention, the pure component refrigerant streams are jointly fed to compression and condensation after removal from the first heat exchanger arrangement before they are supercooled in the first heat exchanger arrangement, as is known per se in a corresponding pure substance refrigerant circuit.

Advantageously, the pure substance refrigerant partial streams are present at the infeed temperature levels in a state that is at least 3 K supercooled, in particular in a state that is at least 5 K, 7 K or 10 K supercooled.

As mentioned several times, plate (fin) heat exchangers can be used in the first heat exchanger arrangement.

With regard to the system provided according to the invention and its features, reference is expressly made to the corresponding independent device claim and the above explanations with regard to the method according to the invention, since these relate to a corresponding device in the same way. The same applies in particular to a configuration of a corresponding device which is advantageously set up to carry out a corresponding method in any configuration.

The invention is explained further below with reference to the figures, which illustrate embodiments of the present invention.

• Figur 1 veranschaulicht ein Verfahren gemäß einer Ausgestaltung der Erfindung.
• Figur 2 veranschaulicht ein Verfahren gemäß einer Ausgestaltung der Erfindung.

Brief description of the figures

• figure 1 illustrates a method according to an embodiment of the invention.
• figure 2 illustrates a method according to an embodiment of the invention.

In the following further description, methods according to embodiments of the invention are described with corresponding method steps. For the sake of simplicity and to avoid unnecessary repetition, Process steps and system components (for example a cooling step and a heat exchanger used for this purpose) use the same reference numbers and explanations.

Detailed description of the figures

In figure 1 and 2 Methods according to embodiments of the present invention are illustrated, with the same reference numbers being used for the same or comparable components or method steps and not being explained repeatedly. The methods as a whole are each denoted by 100.

In each case, a pure substance refrigerant circuit, denoted overall by 10, with a heat exchanger arrangement ("first" heat exchanger arrangement) having a first heat exchanger E1 and a second heat exchanger E2, and a mixed refrigerant circuit, denoted overall by 20, with a third heat exchanger E3 and a fourth heat exchanger E4 (or corresponding Sections of a tube bundle heat exchanger) having a heat exchanger arrangement ("second" heat exchanger arrangement) shown.

A hydrocarbon charge, in the example shown natural gas NG, is fed via a line 1, if necessary, to a compressor C3 and, in particular, compressed to a supercritical state (see flow point 2). After cooling in a heat exchanger E9, the hydrocarbon charge (see stream point 3) is pre-cooled in the heat exchangers E1 and E2 of the first heat exchanger arrangement (see stream point 4 and 5) and, following this pre-cooling, it is heavily supercooled in the heat exchangers E3 and E4 of the second heat exchanger arrangement (see stream point 6).

After compression in a compressor C1 (see current point 10), the pure substance refrigerant of the pure substance refrigerant circuit 10 is liquefied in a condenser E5 and fed to a buffer tank D1 (see current point 11). The liquid pure refrigerant (see current point 12) is then supercooled in a heat exchanger E6 and fed to a heat exchanger E1 (see current point 13).

In the example shown, the complete pure substance refrigerant of the pure substance refrigerant circuit 10 is supercooled in the heat exchanger E1 at the highest pressure level (pressure level 1) in the pure substance refrigerant circuit (see current point 14). The first part of stream 14 is expanded via a line 15 and a valve V1 to the second highest pressure in the pure substance refrigerant circuit 10 (pressure level 2, see stream point 16) and then completely evaporated in heat exchanger E1 (see stream point 17). The supercooling of the pure refrigerant flow 16 takes place through the evaporation of the pure refrigerant flow 22 at the next lower pressure level, pressure level 3.

The second part of stream 14 (see stream point 20) is further supercooled in heat exchanger E2. In the example shown, a partial flow thereof is withdrawn from the heat exchanger E2 via a line 21 (see flow point 21) and expanded to the third-highest pressure level in a valve V2. The supercooled pure refrigerant 22 is then completely evaporated in the heat exchanger E1, see flow point 23. The pure refrigerant 22 is supercooled by evaporating the pure refrigerant flow 32 at the next lower pressure level, pressure level 4.

The remaining portion of the pure refrigerant stream 20 is in turn further supercooled in the heat exchanger E2, see stream point 30. A first partial stream thereof (see stream point 31) is expanded to the fourth pressure level in a valve V3 and fed supercooled into the heat exchanger E2, see stream point 32. Also This pure refrigerant flow is completely evaporated in the heat exchanger E2, see flow point 33. The pure refrigerant 32 is in turn supercooled by the evaporation of the pure refrigerant flow 44 at the next lower pressure level, pressure level 5.

The pure refrigerant flow 40 is further supercooled in the heat exchanger E3, which is located in the mixed refrigerant circuit, see flow point 41, 42 and 43. A bypass around the heat exchanger E3 can be provided for better controllability of the temperature, see flow points 46 and 47 and valves V5A and V5B . After expansion in valve V4, the pure refrigerant flow 44 is fed subcooled into the heat exchanger E2 and then completely evaporated in the example shown at the lowest pressure level (pressure level 5), see flow point 45.

After complete evaporation at the individual pressure stages, all pure refrigerant flows are fed to the compressor C1 and compressed to the highest pressure level. Due to the use of supercooled pure refrigerant flows when feeding into the heat exchangers E1 and E2 (see flow point 16, 22, 32 and 44), compact heat exchangers, such as plate heat exchangers without phase separators, can be used in the pure refrigerant cycle to feed in the individual pure refrigerant flows, as already mentioned. It should be noted that in processes other than those described here, refrigerant flows are very often fed into the plate heat exchanger in two phases with the aid of phase separators. The use of phase separators allows a targeted and controllable distribution of the liquid and gas phase to the heat exchanger and thus prevents maldistribution and the associated thermal and mechanical stress. However, these phase separators require a lot of space and usually store a large proportion of the liquid hydrocarbon inventory of the entire refrigerant circuit. The use of phase separators can be used with the one presented here procedures are dispensed with. The space required for a plate exchanger solution designed in this way as a pure substance refrigerant circuit is correspondingly significantly reduced in comparison to conventional kettle-type solutions. In the same way, the hydrocarbon inventory in the pure substance refrigerant circuit decreases considerably in the process described. Due to the lower hydrocarbon inventory and the fact that plate heat exchangers are typically built in cold boxes with welded flange connections, thus significantly reducing the potential for leakage, the entire process can be built with less safety engineering effort, as discussed above.

The entire mixed refrigerant flow 50 is compressed and after-cooled to a supercritical state in the two compressors C2A and C2B and the corresponding aftercoolers E7 and E8, see flow point 51, 52, 53 and 54. The mixed refrigerant flow in the heat exchangers is similar to the hydrocarbon-rich fraction E1 and E2 pre-cooled and then fed into the heat exchanger E3. A separator before the mixed refrigerant flow 56 is fed into the heat exchanger E3 is not required, since the mixed refrigerant flow 56 is supercritical.

Maldistributions due to a two-phase feed of the mixed refrigerant flow 56 or a separate feed of a gas phase or liquid do not have to be taken into account. Thus, the hydrocarbon inventory and the space requirement of the mixed refrigerant cycle can be reduced similarly to the pure substance refrigerant cycle. The mixed refrigerant flow 56 is greatly cooled in the heat exchangers E3 and E4, see flow point 57. After expansion in valve V6, the two-phase mixed refrigerant is used as refrigerant in the heat exchangers E4 and E3. After complete vaporization, the entire mixed refrigerant stream 50 is superheated and returned to the mixed refrigerant compressors C2A and C2B.

In the figure 2 The process control illustrated has things in common with the method just described. Therefore, only the differences are described below.

in the in figure 2 In the illustrated alternative, the pure substance refrigerant stream 40 is not supercooled in the heat exchanger E3 in the mixed refrigerant circuit, but instead is fed into the heat exchanger E2 as a two-phase stream after direct expansion in the valve V4. However, when plate heat exchangers are used, the pure refrigerant stream 44 must first be separated into a gas phase and a liquid phase in the phase separator D2. It can thus be ensured that the two-phase stream 44 is fed into the heat exchanger E2 in a controlled manner by being divided into the streams 44A and 44B. Incorrect distributions and thermal stresses on the heat exchanger E2 can thus be minimized.

The disadvantage of this alternative is the increased liquid hydrocarbon inventory in the pure refrigerant circuit. However, the decoupling of the pure refrigerant circuit from the mixed refrigerant circuit and the simpler design of the heat exchanger E3, as already mentioned above, are advantageous.

Claims (11)

A method (100) for producing a liquid hydrocarbon (LNG) product using a gaseous hydrocarbon (NG) feedstock, wherein - a pure substance refrigerant circuit (10) operated with a pure substance refrigerant, which has a first heat exchanger arrangement (E1, E2), and a mixed refrigerant circuit (20) operated with a mixed refrigerant, which has a second heat exchanger arrangement (E3, E4), are provided, - at least part of the hydrocarbon charge (NG) is first pre-cooled using the pure refrigerant circuit (10) and then liquefied using the mixed refrigerant circuit (20) to form the liquid hydrocarbon product (LNG), - several pure substance refrigerant partial streams (16, 22, 32, 44) of the pure substance refrigerant are fed into the first heat exchanger arrangement (E1, E2) at different feed pressure levels and at different feed temperature levels, - the pure substance refrigerant substreams (16, 22, 32, 44) are brought to the feed pressure levels and feed temperature levels by expansion starting from a common pre-expansion pressure level and different pre-expansion temperature levels, and - The pre-expansion temperature levels are selected in such a way that the pure substance partial refrigerant flows (16, 22, 32, 44) are present at the feed temperature levels in the supercooled state. Method (100) according to Claim 1, in which at least part of the pure substance refrigerant is cooled in the first heat exchanger arrangement (E1, E2), and in which part of the pure substance refrigerant partial flows (16, 22, 32) are cooled to their pre-expansion temperature levels of the first heat exchanger arrangement (E1, E2) is removed. Method (100) according to Claim 2, in which part of the pure substance refrigerant cooled in the first heat exchanger arrangement (E1, E2) is further cooled in the second heat exchanger arrangement (E3, E4), and in which at least one of the pure substance refrigerant part streams (44) is in the second Heat exchanger arrangement (E3, E4) further cooled pure substance refrigerant is formed on its pre-expansion temperature level. Method (100) according to Claim 2, in which part of the pure substance refrigerant cooled in the first heat exchanger arrangement (E1, E2) is expanded to obtain a two-phase stream, the two-phase stream being subjected to a phase separation (D2) to obtain a gas phase and a liquid phase, and the gas phase and the liquid phase then being fed to the first heat exchanger arrangement (E1, E2). Method (100) according to one of the preceding claims, in which the pure substance refrigerant partial flows (16, 22, 32, 44) are each heated in the first heat exchanger arrangement (E1, E2) from the feed temperature level to an extraction temperature level and at the extraction temperature level of the first heat exchanger arrangement (E1, E2) can be removed. Method (100) according to Claim 5, in which the feed temperature levels and the removal temperature levels of the pure substance refrigerant part streams (16, 22, 32, 44) each include temperature intervals, the temperature intervals for the pure substance refrigerant part streams (16, 22, 32, 44) not overlapping one another. Method (100) according to Claim 5 or 6, in which the pure substance refrigerant partial flows (16, 22, 32, 44) are fed together to compression (C1) and condensation after removal from the first heat exchanger arrangement (E1, E2) before they are first heat exchanger arrangement (E1, E2) are supercooled. Method (100) according to one of the preceding claims, in which the pure substance refrigerant part streams (16, 22, 32, 44) are present at the feed temperature levels in a state which is supercooled by at least 3 K. Method (100) according to one of the preceding claims, in which plate heat exchangers are used in the first heat exchanger arrangement (E1, E2). Plant for producing a liquid hydrocarbon (LNG) product using a gaseous hydrocarbon (NG) feedstock, which - a pure substance refrigerant circuit (10) set up for operation with a pure substance refrigerant, which has a first heat exchanger arrangement (E1, E2), and a mixed refrigerant circuit (20) set up for operation with a mixed refrigerant, which has a second heat exchanger arrangement (E3, E4), includes, the installation having means adapted to - to first pre-cool at least part of the hydrocarbon charge (NG) using the pure substance refrigerant circuit (10) and then to liquefy it to form the liquid hydrocarbon product (LNG) using the mixed refrigerant circuit (20), - to feed several pure substance refrigerant partial streams (16, 22, 32, 44) of the pure substance refrigerant at different feed pressure levels and at different feed temperature levels into the first heat exchanger arrangement (E1, E2), - to bring the pure refrigerant partial streams (16, 22, 32, 44) to the feed pressure levels and feed temperature levels by expanding them, starting from a common pre-expansion pressure level and different pre-expansion temperature levels, and where - The pre-expansion temperature levels are selected in such a way that the pure substance partial refrigerant flows (16, 22, 32, 44) are present at the feed temperature levels in the supercooled state. Plant according to Claim 10, which is set up for carrying out a method according to one of Claims 1 to 9.

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