RU2463535C2 - Method for liquefaction of hydrocarbon flows and device for its realisation - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: method for liquefaction of at least two hydrocarbon flows, such as natural gas, including at least the following stages: a) supply of at least first and second hydrocarbon flows (20, 20a); (b) sending the first hydrocarbon flow (20) via one or more first heat exchangers (12, 14) to form the first cooled hydrocarbon flow (30); and (c) sending the second hydrocarbon flow (20a) via one or more second heat exchangers (12a, 14a) to form the second cooled hydrocarbon flow (30a); where the coolant flow (100) provides for cooling of the first heat exchanger (heat exchangers) (12, 14) and the second heat exchanger (heat exchangers) (12a, 14a).

EFFECT: using the invention will make it possible to increase plant efficiency and to reduce power consumption.

19 cl, 2 dwg

Description

The present invention relates to a method and apparatus for liquefying at least two hydrocarbon streams, such as, for example, at least two natural gas streams.

Several methods are known for liquefying a natural gas stream to produce liquefied natural gas (LNG). Liquefaction of a natural gas stream is desirable for several reasons. For example, natural gas is easier to store and transport over long distances in liquid form than in gaseous form, since it occupies a smaller volume and does not need to be stored under high pressure.

As a rule, natural gas containing predominantly methane is fed to the LNG plant at elevated pressures and pretreated in order to obtain purified raw materials suitable for liquefaction at cryogenic temperatures. The purified gas is treated in several stages of cooling using heat exchangers to gradually lower the gas temperature until liquefaction is achieved. The liquid natural gas is then cooled and expanded at one or more expansion stages to a final atmospheric pressure suitable for storage and transportation. The steam generated during flash evaporation at each stage can be used as a source of fuel gas in the installation.

The costs of creating and operating an installation or system for liquefying natural gas are naturally high and a significant part of them are associated with cooling schemes. Any reduction in energy requirements in a plant or system will save significant costs. Especially beneficial is any cost reduction for any of the cooling schemes.

US 6272882 B1 is devoted to a method for liquefying a gaseous methane-rich feed, resulting in a liquefied product. The liquefaction process involves several stages, one of which is the separation of the partially condensed refrigerant for the main heat exchanger into a liquid heavy fraction of a refrigerant and a gaseous light fraction of a refrigerant. At least a portion of the liquid fraction of the refrigerant is cooled, liquefied and further cooled with the help of exhaust gas discharged from the flash unit installed after the main heat exchanger. The method in US 6272882 B1 has one liquefaction chain.

US 6389844 B1 is devoted to a plant for liquefying natural gas. More specifically, a pre-cooled dual heat exchanger and dual refrigeration system. The installation in US 6389844 B1 has a fluidizing capacity that is 40-60% larger than the fluidizing capacity in the case of a single liquefaction chain and includes a pre-cooling heat exchanger and at least two main heat exchangers. In each of the main heat exchangers, a main refrigerant is used, which is separated into a heavy liquid fraction of a refrigerant and a light gaseous fraction, which are in the main heat exchanger only being cooled before expansion.

An object of the present invention is to improve the efficiency of a treatment plant or a treatment process, in particular a plant or liquefaction process.

An additional objective of the present invention is to reduce the energy requirements of a processing plant or processing method, in particular a liquefaction plant or method.

Another objective of the present invention is to provide an alternative method and device for processing a hydrocarbon stream, in particular for liquefying a hydrocarbon stream.

The present invention provides a method for liquefying at least two hydrocarbon streams, such as at least two natural gas streams, and the method includes at least the following steps:

(a) supplying at least a first and a second hydrocarbon stream;

(b) passing the first hydrocarbon stream through one or more first heat exchangers to form a first cooled hydrocarbon stream;

(c) passing a second hydrocarbon stream through one or more second heat exchangers to form a second cooled hydrocarbon stream; and

(d) subsequent liquefaction of said first and second hydrocarbon streams.

The refrigerant circuit provides cooling of one or more first heat exchangers and one or more second heat exchangers by passing separate flows of refrigerant through one or more first heat exchangers in step (b) and through one or more second heat exchangers in step (c).

The individual refrigerant streams after passing through the first heat exchanger (s) and the second heat exchanger (s), respectively, and / or after exchanging heat with the respective hydrocarbon streams, can be compressed, jointly or separately.

The compressed refrigerant streams may then be co-cooled in one or more common coolers. This way you can reduce the number of coolers needed, which will lower capital and operating costs.

In yet another aspect, the present invention provides an apparatus for liquefying at least two hydrocarbon streams, such as at least two natural gas streams, which includes:

one or more first heat exchangers for cooling the first hydrocarbon stream and creating a first cooled hydrocarbon stream;

- one or more second heat exchangers for cooling the second hydrocarbon stream and creating a second cooled hydrocarbon stream;

at least one liquefaction system arranged in such a way as to liquefy said first and second hydrocarbon streams; and

- a refrigerant circuit comprising at least two separate refrigerant streams, one of which provides cooling for one or more of the first heat exchangers, and the other provides cooling of one or more second heat exchangers.

The refrigerant circuit may also include at least one compressor for compressing the refrigerant streams, together or separately, after they have cooled in the first and second heat exchangers (e).

The refrigerant circuit may further include one or more common coolers for co-cooling the compressed refrigerant streams.

Further, embodiments of the present invention are described only by way of example and with reference to the accompanying, non-limiting, schematic drawings, in which:

figure 1 is a generalized diagram of part of a liquefaction plant according to one embodiment of the present invention; and

figure 2 is a detailed diagram of the installation of the liquefaction shown in figure 1.

In the proposed description, one reference number refers to both the line and the stream carried on this line. The same reference numbers refer to the same components, streams or lines.

The application describes methods and devices in which two hydrocarbon streams are cooled by a refrigerant in a refrigerant circuit by passing a refrigerant stream through one or more first heat exchangers and passing a separate refrigerant stream through one or more second heat exchangers, followed by compressing individual refrigerant streams using at least one compressor.

By using a (preferably one) refrigerant circuit to provide cooling for the first heat exchanger (s) and the second heat exchanger (s), capital and operating costs can be reduced due to the commonality of the elements in a single refrigerant circuit serving different heat exchangers for two hydrocarbon streams.

The refrigerant circuit may include any number of separate lines or flows of refrigerant for cooling various hydrocarbon streams and any number of common elements and parts, including compressors, coolers, etc. Some refrigerant flows may be common and some separate.

The first and second heat exchangers can be separate and without any changes in the existing layout of the first and second heat exchangers, which is an advantage of the invention.

Embodiments of the invention include co-cooling two or more compressed refrigerant streams.

Compressed refrigerant streams can be combined to co-cool them using one or more common coolers. As a rule, refrigerant in the condensed state should be involved in joint or combined cooling. Co-cooling is equivalent to total heat removal from individual refrigerant streams after they are compressed. As is known in the art, one or more other chillers may also be used, either separate, or integrated, or associated with compressors.

When using partial, preferably for the most part, general cooling in the refrigerant circuit, the present invention can reduce the overall energy requirements of a process and installation or device for processing, in particular liquefaction, a hydrocarbon stream and / or make the method and installation or device more efficient and thus more economical.

The refrigerant in the refrigerant circuit may be the only component, such as propane. Preferably, the refrigerant is mixed based on two or more components, which are preferably selected from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane and pentane.

In step (b) of the methods described herein, a first hydrocarbon stream is passed through one or more first heat exchangers to form a first cooled hydrocarbon stream, and in step (c) a second hydrocarbon stream is passed through one or more second heat exchangers to form a second cooled hydrocarbon stream.

In embodiments of the present invention, each of steps (b) and (c) includes passing a hydrocarbon stream through 2, 3, 4 or 5 of the first and second heat exchangers, preferably through the first two heat exchangers and two second heat exchangers.

The first and second cooled hydrocarbon streams can then be processed, for example, liquefied.

Preferably, the first and second hydrocarbon streams are feed streams, mainly derived from a single feed stream. In the case where the first and second hydrocarbon streams are formed in this way, they can be divided equally or not equally, but it is preferable that they be the same. The feed stream can be separated using any suitable separator, flow divider, or some similar means known to the prior art.

In general, the feed stream or streams can be liquefied by passing them through at least two cooling stages. Any number of cooling stages may be used, and each cooling stage may include two or more heat exchangers, as well as one or more operations, levels or sections. Each cooling stage may include two or more heat exchangers arranged in series, in parallel or in a combined manner.

Arrangements of suitable heat exchangers capable of cooling and liquefying a feed stream, such as a hydrocarbon stream such as natural gas, are known in the art.

One of the layouts includes two cooling stages, including the first cooling stage and the second cooling stage, of which the first cooling stage is mainly a pre-cooling stage for cooling below 0 ° C, and the second stage is mainly a main cryogenic stage for liquefaction at a temperature below - 100 ° C.

In one special embodiment of the present invention, a method for treating hydrocarbon streams is part of a method for liquefying a hydrocarbon stream, such as natural gas, from a feed stream, and the processing method includes a first cooling step followed by a second cooling step to liquefy the first and second chilled hydrocarbon streams.

The hydrocarbon streams may be any suitable hydrocarbon-containing streams for liquefaction, but they are typically a natural gas stream obtained from a natural gas source or oil reservoirs. Alternatively, the natural gas stream may be obtained from any other source, including including a synthetic source, such as the Fischer-Tropsch process.

Naturally, natural gas is largely composed of methane. Preferably, the feed stream contains at least 60 mol% of methane and, more preferably, at least 80 mol% of methane.

Depending on the source, natural gas may contain varying amounts of heavier hydrocarbons than methane, such as ethane, propane, butanes and pentanes, as well as some aromatic hydrocarbons. The natural gas stream may also contain non-hydrocarbon materials such as H ₂ O, N ₂ , CO ₂ , H ₂ S and other sulfur compounds, and the like.

If necessary, hydrocarbon streams can be pretreated before being used in the present invention. This pretreatment may include the removal of any undesired components such as CO ₂ and H ₂ S present or other operations such as pre-cooling, pre-pressure, and the like. Since these operations are well known to specialists in this field, they will not be discussed further.

Although the method according to the present invention is applicable to various hydrocarbon feed streams, it is particularly suitable for liquefied natural gas streams. Since a person skilled in the art will easily understand how to liquefy a hydrocarbon stream, further this question will not be discussed in detail here.

In addition, the specialist in this field is easy to understand that liquefied natural gas after liquefaction can, if necessary, be processed further. For example, the resulting LNG can be decompressed using a Joule-Thomson valve or using a cryogenic turbo expander.

The present invention may include one or more additional refrigerant circuits, for example included in or passing through a first cooling step. In some cases, for cooling the first and second hydrocarbon streams, any other or additional refrigerant circuits may optionally be connected to the refrigerant circuit and / or they may be parallel to it.

Figure 1 shows the General layout of the installation of liquefied natural gas (LNG). An initial feed stream 10 containing natural gas is shown. Along with methane, natural gas typically includes some heavier hydrocarbons and impurities, such as carbon dioxide, nitrogen, helium, water and non-hydrocarbon acid gases. With the aim of the maximum possible separation of these impurities and the preparation of purified raw materials suitable for liquefaction at cryogenic temperatures, the feed stream 10 is subjected, as a rule, to preliminary processing.

The feed stream 10 is separated by a stream splitter 15, forming the first and second hydrocarbon streams 20 and 20a before the first cooling stage 2. The feed stream 20 may be partitioned into any number of hydrocarbon streams, and the separation of two hydrocarbon streams shown in FIG. 1 is only a preferred example. The separation of the feed stream 10 can be carried out on the basis of any ratio: by weight and / or volume, and / or by flow rate. This ratio may be based on the size or capacity of the subsequent parts of the reduction stages, systems or nodes, or may be based on other considerations. One example of a ratio is the separation of the feed stream into equal parts by weight.

In the first cooling stage 2, the first hydrocarbon stream 20 passes through a first cascade of two first heat exchangers 12, 14, forming a first cooled hydrocarbon stream 30. A second hydrocarbon stream 20a passes through a second cascade of second heat exchangers 12a, 14a, which may be identical or different from the first cascade of the first heat exchangers 12, 14, resulting in the formation of a second cooled hydrocarbon stream 30a.

The first heat exchangers 12, 14 and the second heat exchangers 12a, 14a are cooled by the first refrigerant circuit 100. The first refrigerant circuit 100 has two refrigerant streams, 101 and 101a, which individually cool the first heat exchangers 12, 14 and the second heat exchangers 12a, 14a, respectively. After cooling, the refrigerant streams 101, 101a are fed into one or more separate compressors 32, 32a before the compressed streams 101d, 101e are combined to form a single stream 101f for total heat removal. A single stream 101f passes through one or more common water and / or air coolers, two of which, namely coolers 34, 34a, are shown in FIG. Then, the condensed (typically) refrigerant stream 101g is separated to form separate refrigerant streams 101, 101a for cooling.

The first cooling stage 2 can include any number of heat exchangers for each hydrocarbon stream, and the feed stream 10 can be divided into more than two hydrocarbon streams.

The first cooling stage 2 should, as a rule, cool the first and second hydrocarbon streams 20, 20a to a temperature below 0 ° C and mainly to a temperature of from -20 to -60 ° C.

1, the first and second cooled hydrocarbon streams 30, 30a pass through a second cooling stage 4, in which they are liquefied using two separate liquefaction systems, each of which typically includes at least one heat exchanger, resulting in separate liquefied streams 40, 40a, respectively. Liquefaction systems and process conditions for liquefaction are well known in the art and are not further described. 1, two liquefaction systems are symbolically represented by liquefying heat exchangers 16 and 16a. Moreover, they are also heat exchangers, but are referred to as fluidizing heat exchangers just to emphasize their difference (functional) from the first and second heat exchangers described above.

In each of the fluidizing heat exchangers 16, 16a, a refrigerant circuit is used in the second cooling stage 4 in the example shown in FIG. 1: the first refrigerant circuit 102 is used in the first fluidizing heat exchanger 16, and the second refrigerant circuit 103 is used in the second fluidizing heat exchanger 1ba. The same or different refrigerants may be used in each of these refrigerant circuits 102, 103. It is preferred that the same refrigerant is used in each of the circuits and, more preferably, the mixed refrigerant is used for each of the refrigerant circuits 102, 103. The mixed refrigerant may be based on two or more components, preferably selected from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane and pentane.

Typically, the first and second cooled hydrocarbon streams 30, 30a are cooled in a second cooling stage 4 to a temperature of at least below -100 ° C.

The liquefied streams 40 and 40a are then combined. They can be combined in any known manner and with any known combination of steps. Such a combination of streams may occur before or after any expansion of any of the liquefied streams 40, 40a. When combining liquefied streams for their subsequent passage through a gas-liquid separator, complete integration or mixing may not be required. It is preferable to combine the streams before passing them through a gas-liquid separator.

Layouts for combining flows are known to those skilled in the art. The layout example shown in FIG. 1 is intended to combine liquefied streams 40, 40a using a combiner 18 known in the art to form a combined liquefied hydrocarbon stream 50. The combiner may have any suitable layout, typically including a combination or bundle of pipes, or pipelines, which may include one or more valves.

The combined liquefied hydrocarbon stream 50 formed in the second cooling stage 4 may pass through an air damper safety valve (not shown) to a gas-liquid separator such as an instant separation apparatus 22, which typically produces a liquid stream as a liquefied hydrocarbon product stream 60 product and steam in the form of a gaseous stream 70. The liquefied hydrocarbon stream 60 is then sent via one or more pumps (not shown) to storage and / or transport means ings.

FIG. 2 shows a more detailed diagram of an embodiment of the present invention shown in FIG. 1, in which the feed stream 10 is divided into first and second hydrocarbon streams 20a, 20b that pass through two separate but parallel and identical cascades of the first heat exchangers 12, 14 and second heat exchangers 12a, 14a providing the first cooling stage 2.

Both stages of the first and second heat exchangers 12, 14, 12a, 14a include cooling using one cooling circuit 100. The first cooling circuit 100 has two refrigerant lines 101 and 101a that individually cool the first stage of the first heat exchangers 12, 14 at two different pressure levels in a manner known from the prior art and, accordingly, cool the second stage of the second heat exchangers 12a, 14a at two different pressure levels known in the prior art method.

Upon completion of their cooling, the refrigerant streams 101 and 101a are supplied to two stages of compressors 36 and 36a, respectively. Each compressed refrigerant stream is passed through separate water and / or air coolers 38 and 38a, respectively, and then combined to form a single refrigerant stream 101f. Separate coolers 38, 38a during their recirculation also provide cooling for compressors 36 and 36a.

The single refrigerant stream 101f then passes through a large water and / or air cooler 34, where most of the heat of the refrigerant is exchanged by venting it to the environment during condensation of the refrigerant. After this, the refrigerant enters the collector 42 known from the prior art. From the collector 42, the refrigerant stream passes through the last and usually smaller water and / or air cooler 34a, after which it is separated by two refrigerant lines 101 and 101a.

Preferably, the large cooler 34 provides the same level of cooling as the prior art coolers in separate refrigerant circuits currently used to cool two hydrocarbon streams.

It should be noted that all cooling of the refrigerant in the first refrigerant circuit 100 is or should be done using a common refrigeration unit or units, such as a large cooler 34. The individual coolers 38 and 38a should provide some initial cooling, although their function is to provide compressors 36 and 36a gas recirculation method known in the prior art. We only note as an example that the ratio of the cooling capacity of the large (and general) cooler 34 to the cooling capacity of the compressor-coolers 38 and 38a can be from 5: 1 to 20: 1 or higher, but is preferably 10: 1. In the case of the present invention, at least a large part of the refrigerant refrigeration in the refrigerant circuit 100 is provided with a common cooler or coolers after re-combining all the individual refrigerant streams (after they have cooled the hydrocarbon streams in the respective heat exchangers).

The arrangement of the first cooling circuit 100 in FIGS. 1 and 2 simplifies the cooling supplied to one heat exchanger or to several of the heat exchangers, or to all the heat exchangers of the first cooling stage 2 or any of the cooling stages, configuration or arrangement. In particular, the arrangements shown in FIGS. 1 and 2 reduce the number of water and / or air units and collectors needed for the first refrigerant circuit 100, which, however, can still provide two refrigerant flows for separate heat exchanger stages. In order to further reduce capital and operating costs for the first refrigerant circuit 100 and / or the first cooling stage 2, it is possible to further reduce the number of parts related to the first refrigerant circuit 100 by further combining coolers, valves and / or compressors.

After the second heat exchanger 14 in the course of the process, the cooled hydrocarbon stream 30 exits from the first heat exchangers 12, 14. This stream 30 and its equivalent cooled hydrocarbon stream 30a from the second stage of the second heat exchangers 12a, 14a of the first cooling stage 2 then enter two parallel, mostly identical fluidizing heat exchanger 16, 16a, which form the second cooling stage 4.

The fluidizing heat exchangers 16, 16a of the second cooling stage 4 are predominantly cryogenic heat exchangers with bobbin or spiral winding, the operation of which is known from the prior art and the cooling of which is provided by the second and third refrigerant circuits 102,103, respectively.

Each of the liquefying heat exchangers 16, 16a creates liquefied hydrocarbon streams 40, 40a, which are then combined into a combined liquefied hydrocarbon stream 50. After passing through a third heat exchanger 24, the cooled combined liquefied hydrocarbon stream 50a passes through an expander into a gas-liquid separator, which is known from prior art end apparatus 22 of instant separation. Liquefied hydrocarbon product stream 60 exits from the end separation apparatus 22, which can be used for storage and / or transportation by pump 26 and a gaseous stream 70, which after some heat exchange can be used as fuel gas and / or be used in other parts of the LNG plant.

In the example shown in FIG. 2, mixed refrigerant is used in the first, second and third refrigerant circuits 100, 102, 103. In the second and third refrigerant circuits 102 and 103, the same mixed refrigerant is used.

The mixed refrigerant of each refrigerant circuit may be based on two or more components, which are more preferably selected from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane and pentane. The average molecular weight of the refrigerant in the first refrigerant circuit 100 is preferably higher than the average molecular weight of the refrigerant in the second and third refrigerant circuits 102 and 103.

For purposes of clarity, the second refrigerant circuit 102 is disclosed in more detail below. A vaporous refrigerant stream 102e leaves the fluidizing heat exchanger 16, which is compressed and cooled by two compressors and two water or air coolers to form a cooled refrigerant stream 102a. This chilled refrigerant stream 102a then passes through a cascade of two heat exchangers 12, 14 of one part of the first cooling stage 2, which to some extent cools the second refrigerant. The additionally cooled refrigerant stream 102b is then fed to a gas-liquid separator 46. A light refrigerant fraction 102 and a heavy refrigerant fraction I02d are discharged from the separator 46, both of which enter the fluidizing heat exchanger 16 for cooling and expand to use their cold energy in the fluidizing heat exchanger 16 known in the prior art method.

Table 1 shows a representative working example of temperatures, pressures, and flow directions in different parts of the process example of the present invention shown in FIG. 1.

Table 1 Stream number Temperature (° C) Pressure (bar) Mass speed (kg / s) Phase 10 51.0 92.6 277.7 Steam twenty 51.0 92.6 139.5 Steam thirty -41.5 89.0 140.0 Steam 40 -151.4 83.5 140.0 Liquid 50a -156.8 81.0 280,0 Liquid 60 -162.5 1,1 251.6 Liquid 70 -165.1 1,0 28,4 Steam 102a 46.0 53.3 205.0 Steam 102b -41.5 49.0 205.0 Mixed 102s -41.6 48.9 36.0 Steam 102d -41.6 48.9 169.0 Liquid 102e 62.3 19.9 205.0 Steam 101 41.0 37.8 442.9 Liquid 101f 68.7 38.6 885.9 Steam

The specialist should be clear that the present invention can be implemented in various ways without changing the scope of the attached claims.

Claims (19)

1. A method of liquefying at least two hydrocarbon streams, such as at least two natural gas streams, comprising the steps of: (a) supplying at least a first and a second hydrocarbon stream; (b) passing the first hydrocarbon stream through one or more first heat exchangers to form a first cooled hydrocarbon stream; (c) passing a second hydrocarbon stream through one or more second heat exchangers to form a second cooled hydrocarbon stream; and (d) subsequently liquefying said first and second hydrocarbon streams, in which a refrigerant circuit provides cooling of one or more first heat exchangers and one or more second heat exchangers by passing individual refrigerant streams through one or more first heat exchangers of stage (b) and through one or more second heat exchangers of stage (c) and separate compression s each refrigerant stream after passing through at least one or more first heat exchangers and, accordingly, through at least one or more second heat exchangers and a joint cooling compressed refrigerant streams in one or more common coolers. 2. The method according to claim 1, in which stage (b) includes passing the first hydrocarbon stream through 2, 3, 4 or 5 of the first heat exchangers, mainly through the first two heat exchangers; and in which step (c) comprises passing a second hydrocarbon stream through 2, 3, 4 or 5 second heat exchangers, preferably through two second heat exchangers. 3. The method according to claim 1, further comprising combining separately compressed flows of refrigerant before said co-cooling in said one or more common coolers. 4. The method according to claim 2, further comprising combining separately compressed refrigerant flows before said co-cooling in said one or more common coolers. 5. The method according to claim 4, further comprising passing each stream of compressed refrigerant through separate water and / or air coolers to the specified combination. 6. The method according to claim 5, in which at least cooling most of the refrigerant is provided with one or more common coolers. 7. The method according to one of claims 1 to 6, in which the transmission stages (b) and (c) are part of the first cooling stage and in which the subsequent liquefaction stage (d) includes additional cooling of said first and second hydrocarbon streams to the second cooling stage. 8. The method according to one of claims 1 to 6, in which the first and second hydrocarbon streams in stage (d) are liquefied as separate streams. 9. The method according to claim 7, in which the first and second hydrocarbon streams in stage (d) are liquefied as separate streams. 10. The method according to one of claims 1 to 6, in which the first and second hydrocarbon streams are feed streams, mainly formed from a single stream of raw materials. 11. The method according to claim 7, in which the first and second hydrocarbon streams are feed streams, mainly formed from a single stream of raw materials. 12. The method of claim 8, in which the first and second hydrocarbon streams are feed streams, mainly formed from a single stream of raw materials. 13. The method according to claim 9, in which the first and second hydrocarbon streams are feed streams, mainly formed from a single stream of raw materials. 14. A device for liquefying at least two hydrocarbon streams, such as at least two natural gas streams, including: one or more first heat exchangers for cooling a first hydrocarbon stream and forming a first cooled hydrocarbon stream; one or more second heat exchangers for cooling the second hydrocarbon stream and forming a second cooled hydrocarbon stream; at least one liquefaction system arranged in such a way as to liquefy said first and second cooled hydrocarbon streams; and a refrigerant circuit comprising at least two separate refrigerant streams, one of which provides cooling of one or more first heat exchangers, and the other provides cooling of one or more second heat exchangers, at least one separate compressor in each separate refrigerant stream to compress the refrigerant streams and one or more common chillers for co-cooling compressed refrigerant streams. 15. The device according to 14, further comprising a flow divider for separating the feed stream into at least the first and second hydrocarbon streams. 16. The device according to 14 or 15, further comprising a combiner located after individual compressors and to one or more common coolers for combining individual compressed refrigerant streams. 17. The device according to clause 16, further comprising a compressor-cooler in the form of a water and / or air cooler, respectively located in each compressed refrigerant stream to a combiner, and the cooling level of one or more common coolers is greater than the cooling level of the compressor-coolers. 18. A method of liquefying at least two hydrocarbon streams, such as at least two natural gas streams, comprising the steps of: (a) supplying at least a first and a second hydrocarbon stream; (b) passing the first hydrocarbon stream through one or more first heat exchangers to form a first cooled hydrocarbon stream; (c) passing a second hydrocarbon stream through one or more second heat exchangers to form a second cooled hydrocarbon stream; and (d) subsequently liquefying said first and second hydrocarbon streams, in which a refrigerant circuit cools one or more first heat exchangers and one or more second heat exchangers by passing individual refrigerant streams through one or more first heat exchangers of step (b) and through one or more second heat exchangers of step (c), separate compression each refrigerant stream after passing through at least one or more first heat exchangers and, accordingly, through at least one or more second heat exchangers and combining separate streams of the compressed refrigerant. 19. An apparatus for liquefying at least two hydrocarbon streams, such as at least two natural gas streams, including: one or more first heat exchangers for cooling a first hydrocarbon stream and forming a first cooled hydrocarbon stream; one or more second heat exchangers for cooling the second hydrocarbon stream and forming a second cooled hydrocarbon stream; at least one liquefaction system arranged in such a way as to liquefy said first and second cooled hydrocarbon streams; and a refrigerant circuit comprising at least two separate refrigerant streams, one of which provides cooling of one or more first heat exchangers, and the other provides cooling of one or more second heat exchangers; at least one separate compressor in each of the individual refrigerant streams and a combiner located after the individual compressors to combine the individual compressed refrigerant streams.

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