JP5259727B2 - Methods and apparatus for cooling and / or liquefying hydrocarbon streams - Google Patents

Description

  The present invention relates to a method and apparatus for cooling a hydrocarbon stream. In another aspect, the invention relates to a method for liquefying a hydrocarbon stream.

  A common example of a hydrocarbon stream that is cooled and / or liquefied is natural gas.

  Several methods are known for obtaining liquefied natural gas (LNG) by liquefying a natural gas stream. It is desirable to liquefy the natural gas stream for several reasons. As an example, the liquid occupies a smaller volume than the gas state and does not need to be stored at high pressure, so that natural gas can be stored and transported over a long distance as a liquid more easily than the gas state.

  Natural gas can be liquefied using a compressed refrigerant. US Pat. No. 6,962,060 combines first and second refrigerant compressors (each having a first and second stage) and effluent from the second stage of the first and second compressors. And a compressor system for multistage cooling of LNG, which is provided with piping means for obtaining compressed gas. However, because of the need to combine the maximum pressure effluents from the two second stages of the first and second compressors, these two effluents are made exactly the same pressure, flow rate, etc. to prevent back pressure and surge. There must be. The disadvantage of this is that the variability allowed between the two effluents is limited to prevent coupling problems. As is known in the art, refrigerant compressors typically operate at different discharge pressures, eg, to temporarily prevent surges within one compressor, but the two effluents are high pressure, so that upstream and It becomes very difficult to absorb the different discharge pressures and maintain the downstream flow rate without causing turbulence that causes further complications downstream.

  Also, US Pat. No. 6,962,060 shows only one configuration consisting of first and second compressors having first and second stages. There is no flexibility to provide a compression system for other cooling configurations.

The present invention includes (a) supplying a refrigerant flow at a cooling pressure;
(B) passing the refrigerant stream through three or more heat exchange processes operating at different pressure levels;
(C) obtaining a cooled hydrocarbon stream by gradually reducing the temperature of the hydrocarbon stream by passing the hydrocarbon stream through at least two of the heat exchange steps of step (b);
(D) In each heat exchange step, a part of the refrigerant flow is expanded and evaporated to different pressures, and the first evaporative refrigerant flow having the first evaporating pressure and two or more other evaporating refrigerant flows having an evaporating pressure lower than the first evaporating pressure are used. And a process of obtaining
(E) compressing the first evaporative refrigerant stream to a cooling pressure by a maximum pressure compression stage of a single compressor casing to obtain at least a portion of the refrigerant stream at the cooling pressure of step (a);
(F) compressing the other evaporative refrigerant stream by two or more parallel low pressure compression stages to obtain two or more partially compressed refrigerant streams; and (g) replacing all of the partially compressed refrigerant streams with the maximum of step (e). A method for cooling a hydrocarbon stream, such as natural gas, comprising at least a step of passing through a pressure compression stage.

  The present invention further provides a method of liquefying a hydrocarbon stream to obtain a liquefied hydrocarbon stream, the method comprising cooling the hydrocarbon stream in accordance with the method described above or using the apparatus described below.

The present invention provides a cooling pressure refrigerant flow,
Three or more heat exchangers with decompression means for operating the heat exchange process at different pressure levels;
Refrigerant passage means for passing the refrigerant stream through three or more heat exchangers;
Hydrocarbon passage means for passing the hydrocarbon stream through at least two of the heat exchange steps to obtain a cooled hydrocarbon stream;
A first evaporative refrigerant stream at a first evaporating pressure;
Two or more other evaporation streams having an evaporation pressure lower than the first evaporation pressure;
A maximum pressure compression stage in a single compressor casing to compress the first evaporative refrigerant stream to obtain at least a portion of the refrigerant stream at cooling pressure;
Two or more parallel low pressure compression stages for compressing the other evaporative refrigerant streams to obtain one or more partially compressed refrigerant streams; and all of the partial compressed refrigerant streams to a maximum pressure compression stage in the single compressor casing An apparatus is provided for cooling a hydrocarbon stream, such as natural gas, including at least a passage for passage therethrough.

The embodiments of the present invention will now be described with reference to the accompanying drawings by way of example only and not limitation.
It is the 1st composition of the hydrocarbon cooling method by one mode of the present invention. It is a 2nd structure of the hydrocarbon cooling method by another aspect of this invention.

  For purposes of explanation, one reference number is assigned to one conduit and the flow carried in that conduit. The same reference numbers indicate similar components.

  In an aspect of the present invention, an improved method of cooling a hydrocarbon stream such as natural gas is provided and has excellent flexibility in its refrigerant compressor configuration.

  A method is proposed for cooling a hydrocarbon stream using one compressor effluent of refrigerant at cooling pressure from the maximum pressure compression stage of the refrigerant compressor. In other words, the maximum pressure compression stage is arranged in one compressor casing (possibly with one or more low pressure compression stages of the same compressor row).

  One advantage of this is that it is not necessary to balance the discharge pressure flow from compressors with different cooling pressures. This has the further advantage of increasing the allowable variability for the effluent from the low pressure compression stage or process. Therefore, it is necessary to prevent a surge at such a low pressure of the effluent, but a wide variability of the compressor can be obtained.

  Another advantage of the present invention is that it is required by the present invention (eg, the embodiment shown in FIG. 1 to be described later) from a prior art flow arrangement as illustrated in US Pat. No. 6,962,060. There is little or no additional CAPEX or OPEX needed to create a new flow configuration.

  Easy reconfiguration of the interconnection between the vaporized and partially compressed flow and the compression stage provides excellent flexibility in matching the entire cooling load curve provided by the refrigerant flow in the heat exchange process to the compressor load requirements Sex can be achieved.

  FIG. 1 is a first overall view 1 of a hydrocarbon cooling method, which generally includes cooling a hydrocarbon stream 20 such as natural gas.

  The hydrocarbon stream may be any suitable gas stream to be cooled, but is usually a natural gas stream obtained from a natural gas or petroleum store. Alternatively, the natural gas stream can be obtained from another source, including a synthetic source such as a Fischer-Tropsch process.

  Usually, the natural gas stream consists essentially of methane. Preferably, the hydrocarbon feed stream contains at least 50 mol% methane, more preferably at least 80 mol% methane.

Depending on the source, natural gas may contain not only aromatic hydrocarbons but also hydrocarbons heavier than methane such as ethane, propane, butane and pentane. Depending on the type and location of natural gas, its composition varies. Hydrocarbons that are generally heavier than methane also need to be removed from natural gas for several reasons, such as having different freezing or liquefaction temperatures that can block parts of the methane liquefaction plant. The removed C _2-4 hydrocarbon can be used as a source of natural gas liquid.

The natural gas stream may also contain non-hydrocarbons such as H ₂ O, N ₂ , CO ₂ , Hg, H ₂ S, other sulfur compounds, and the like.

If necessary, the hydrocarbon stream containing the natural gas may be pretreated before use either as part of the hydrocarbon cooling process or separately. This pretreatment may include other steps such as reduction and / or removal of non-hydrocarbons such as CO ₂ and H ₂ S, or pre-cooling, pre-pressurization. Since these steps are well known to those skilled in the art, the mechanism is not further described here.

  Preferably, the hydrocarbon stream used in the present invention is subsequently subjected to at least the minimum pretreatment required to liquefy the hydrocarbon stream. Such requirements for liquefying natural gas are well known in the art.

  The refrigerant stream used in the present invention may be composed of a single component such as propane or nitrogen, or two or more components selected from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane, pentane and the like. It is good also as a mixed refrigerant | coolant formed from the mixture of these.

  The present invention may comprise or be part of a multi-stage cooling method comprising two or more cooling stages, each stage having one or more steps, parts, etc. For example, each cooling stage may include 1 to 5 heat exchange processes. The first cooling stage can reduce the temperature of the hydrocarbon stream to below 0 ° C, usually in the range of -20 ° C to -160 ° C, more usually to -20 ° C to -70 ° C. Such a first cooling stage is often referred to as a “pre-cooling” stage.

  In general, the second cooling stage is separate from the first cooling stage. That is, the refrigerant in the second refrigerant stream may pass through one or more heat exchange steps of the first cooling stage, but the second cooling stage uses one or more of the second refrigerant circulating in the second refrigerant circuit. Includes separate heat exchange steps. Such a second cooling stage is often referred to as a “main cooling” stage.

  Referring to the drawings, FIG. 1 shows hydrocarbons passing in series through four heat exchange steps consisting of a first heat exchange step 12, a second heat exchange step 14, a third heat exchange step 16 and a fourth heat exchange step 18. Stream 20 is shown. Each heat exchange step 12, 14, 16, 18 may include one or more heat exchangers with multiple heat exchangers operating in series, in parallel or a combination thereof.

  In general, each heat exchange step 12, 14, 16, 18 includes a single heat exchanger, such as a kettle-type or plate-and-fin heat exchanger known in the art. A series of kettle-type or plate-and-fin heat exchanger configurations are known in the art.

  In general, each heat exchange step 12, 14, 16, 18 gradually reduces the temperature of the hydrocarbon stream 20 to obtain a cooled hydrocarbon stream 30 therefrom. For example, in the heat exchange steps 12, 14, 16, and 18 shown in FIG. 1, the temperature of a hydrocarbon stream such as natural gas is less than 0 ° C., usually −20 ° C. to − The temperature can be lowered to 70 ° C.

  An example of the above configuration is the first or precooling stage in the hydrocarbon cooling method, which may be a stage in a hydrocarbon liquefaction plant such as an LNG plant.

  FIG. 1 also shows a first refrigerant circuit 3 that supplies a refrigerant stream 10 such as propane at a cooling pressure to cool the heat exchange steps 12, 14, 16, 18 by passing it along with a hydrocarbon stream 20.

  The four heat exchange steps 12, 14, 16, 18 operate at different pressure levels, and in each of the heat exchange steps 12, 14, 16, 18, a portion of the refrigerant stream 10 is expanded and evaporated. Usually, this expansion is performed by passing a refrigerant flow through decompression means (not shown) in the form of an expander, a valve or the like. Usually, the remaining portion of the refrigerant stream is sent to the next heat exchange step until the last remaining portion that passes through the fourth heat exchange step 18 is fully expanded and evaporated. Since each heat exchange process 12, 14, 16, 18 operates at a different pressure, an evaporative refrigerant flow is obtained from each heat exchange process 12, 14, 16, 18 at a different evaporation pressure.

  In general, in the first heat exchange step 12, the first evaporative refrigerant stream 40 is obtained at a first evaporating pressure, generally at a “maximum” pressure closest to the cooling pressure of the refrigerant stream 10. This maximum evaporation pressure is also referred to as “high pressure”, and the first evaporative refrigerant stream 40 is also referred to as “high pressure evaporative refrigerant stream” 40.

  The second heat exchange step 14 receives the first remaining portion 10a of the first refrigerant stream 10 and expands and evaporates a portion of the first remaining portion 10a to a pressure lower than the first evaporation pressure of the first evaporated refrigerant stream 40. To obtain a second or other refrigerant stream 50. The second evaporative flow 50 is also referred to as a “high pressure evaporative refrigerant flow”.

  Of the first remaining portion 10a that has not expanded or evaporated in the second heat exchange step 14, the second remaining portion 10b is sent to the third heat exchange step 16, and another part of the refrigerant flow 10 is expanded and evaporated to perform the first evaporation. A third or other evaporative refrigerant stream 60 is obtained at an evaporation pressure lower than the pressure. This third or other evaporative refrigerant stream 60 is also referred to as a “medium pressure evaporative refrigerant stream”.

  The third remaining portion 10c of the refrigerant flow 10 is sent to the fourth heat exchange step 18, where it is expanded and evaporated to obtain a fourth or other evaporative refrigerant flow 70 at an evaporation pressure lower than the first evaporation pressure. . The fourth evaporative stream 70 is also referred to as a “low pressure evaporative refrigerant stream” 70.

  Methods, settings and configurations of heat exchange steps 12, 14, 16 and 18 and multi-stage expansion and evaporation of refrigerant stream 10 are known in the art, examples of which are described in US Pat. No. 6,962,060 and No. 6,637,238.

  By expanding and evaporating some or all of the remainders 10a, 10b and 10c of the refrigerant stream 10 in each of the second, third and fourth heat exchange steps 14, 16, 18 the hydrocarbon stream 20 performs the above steps. The hydrocarbon stream 20 can be cooled further or cooler as it passes. However, each of the evaporative refrigerant streams 40, 50, 60 and 70 must then be recompressed back to the cooling pressure of the original refrigerant stream 10.

  As shown in FIG. 1, the first evaporative refrigerant stream 40 is compressed by a maximum pressure compression stage 22 to obtain at least a portion of the refrigerant stream 10 at the cooling pressure. The term “maximum pressure compression stage” refers to the compression stage having the maximum inlet pressure. When the first evaporative refrigerant stream is the at most pressure evaporative refrigerant stream 40, the maximum pressure compression stage can also be referred to as the at most pressure compression stage.

  As shown in FIG. 1, the maximum pressure compression stage 22 is part of a compressor row A that also includes a third compression stage 26. As used herein, a “compressor row” may include one compression stage or two or more combined compression stages. In general, in the compressor row, all of the compressed refrigerant from the lower pressure stage is subsequently sent to the next higher compression stage, so there is one effluent from the highest level compression stage in the compressor row.

  The configuration of two or more compressors, compression stages or combinations thereof that form a compressor row is well known in the art. In general, a compression train includes one compression stage in one casing or two, three or four combined compression stages in one casing. In the latter case, the compressed refrigerant from the lowest compression stage is typically combined with one or more higher pressure feeds from one or more intermediate inlets and passed through each higher compression stage.

  The compressor row A shown in FIG. 1 includes a third compression stage 26 for compressing the third evaporative refrigerant stream 60. The third compression stage 26 does not compress the third evaporative refrigerant stream 60 sufficiently to return to the cooling pressure of the initial refrigerant stream 10, resulting in a “partially compressed refrigerant stream” 60 a.

  Next, the partially compressed refrigerant stream 60 a is fed directly from the third compression stage 26 to the maximum pressure compression stage 22. The maximum pressure compression stage 22 is contained in one casing alone or together with other low pressure stages of the compressor row A, for example.

  A second or high evaporative refrigerant stream 50 is sent to the second or high pressure compression stage 24. The fourth or low evaporative refrigerant stream 70 is sent to a fourth or low pressure compression stage 28 from which the partially compressed refrigerant stream 70a is coupled with the second evaporative refrigerant stream 60 in the second or high pressure compression stage 24. Send directly to.

  The second and fourth compression stages 24, 28 consist of a second compression string B that is separate from the first compression string A. Thus, at least two of the low pressure compression stages 24, 26, 28 are in two or more compressor rows A and B.

  Since the second and fourth compression stages 24 and 28 are also in parallel with the third compression stage 26, there are two or more parallel low-pressure compression stages in the overall configuration 1 of FIG. The low-pressure compression stages are parallel because the low-pressure compression stages 24, 26, 28 are not in series or arranged in one casing and / or other evaporative refrigerant streams (second, The third and fourth evaporative refrigerant streams 50, 60, 70) are not compressed in series and / or the lowest pressure evaporative stream (fourth evaporative refrigerant stream 70 in FIG. 1) passes through all compression stages. It means no.

  The effluent from the second compression stage 24 is still a partially compressed refrigerant stream 50a that passes through the outlet 24a of the second compressor row B. As shown in FIG. 1, a partially compressed refrigerant stream 50a is combined with a first evaporative refrigerant stream 40 by a coupler 34 to provide a first or at most pressure compression stage 22 of the first compressor row A. Pass through the inlet 32.

  In this manner, generally all of the partially compressed refrigerant streams 50a, 60a and 70a are passed through a single casing maximum pressure compression stage 22.

  FIG. 1 also shows the effluent (of FIG. 1) of this or each low pressure compression stage (second and fourth compression stages 24, 28 of FIG. 1) in parallel with the maximum pressure compression stage (first compression stage 22 of FIG. 1). An example of how line 50a) passes through the maximum pressure compression stage.

  FIG. 2 shows a second overall configuration 2 of the hydrocarbon cooling method, which generally involves cooling a hydrocarbon stream 20 such as natural gas. Similar to the method described above for the first overall configuration 1 of FIG. 1, the hydrocarbon stream 20 may be passed through four heat exchange steps 12, 14, 16, 18.

  As a first option, the hydrocarbon stream may not be passed through all of the same heat exchange steps 12, 14, 16, 18 as the refrigerant stream 10. Flow 20a in FIG. 2 shows a hydrocarbon stream that is cooled only in the second, third, and fourth heat exchange steps 14, 16, 18. The first heat exchange step 12 can be used to cool one or more other flows, such as another refrigerant stream or another refrigerant circuit.

  FIG. 2 shows a second refrigerant circuit 4 similar to the first refrigerant circuit 3 shown in FIG. 1, in which the refrigerant stream 10 is passed through a first heat exchange step 12 and the subsequent portions 10a, 10b, 10c of the refrigerant stream 10 are shown. Is passed through the subsequent second, third and fourth heat exchange steps 14, 16, 18 and in each heat exchange step 12, 14, 16, 18 a part of the refrigerant stream 10 is expanded and evaporated to produce the first evaporation. A refrigerant stream 40 is obtained, and the second, third and fourth low-pressure evaporating streams 50, 60 and 70 described above are similarly obtained.

  The first evaporative stream 40 is compressed through the maximum pressure compression stage 22 to obtain a portion of the initial refrigerant stream 10 at the cooling pressure.

  In the second overall configuration 2 shown in FIG. 2, the maximum pressure compression stage 22 is part of the third compressor row C, which together with the second and fourth low pressure compression stages 24. , 28 are also included. The second and fourth compression stages 24 and 28 are in parallel with the third compression stage 26. Thus, there are at least two of the low pressure compression stages 24, 26, 28 in at least two compressor rows C and D.

  The fourth evaporative stream 70 is sent to the fourth compression stage 28, from which the partially compressed refrigerant stream 70a is sent directly to the second compression stage 24 along with the second evaporative stream 50. The partially compressed refrigerant stream 50 a is then sent directly from the second compression stage 24 to the maximum pressure stage 22.

  On the other hand, the third evaporative refrigerant stream 60 is fed into the parallel third compression stage 26 constituting the fourth compressor row D. Thus, the fourth compressor row D includes only one compression stage 26 separated from the compression stages 22, 24, 28 of the third compressor row C.

  The effluent of the partially compressed refrigerant stream 60 a from the third compression stage 26 is sent out from the outlet 26 a of the second compressor row D, combined with the first evaporative stream 40 by the coupler 36, and passed through the maximum pressure stage 22.

  FIGS. 1 and 2 show two examples of the flexibility of the present invention configured to receive at least three evaporative refrigerant streams at different evaporating pressures, these streams being 3 in at least two separate compressor rows. Recompress in various configurations or systems with two low pressure compression stages 24, 26 and 28.

  Table 1 lists some example configurations for the four compression stages for recompressing the evaporative refrigerant stream from four different heat exchange processes according to the present invention, but for ease of reference, FIG. The code of the compression stage used in 2 is used.

  From Table 1, how the effluent of each row that does not contain refrigerant flow up to the maximum compressor is transferred directly to the maximum pressure stage 22 or how the previous compression in the same column as the maximum pressure stage 22 It is possible to check whether all these refrigerants are passed through the maximum pressure stage 22 by sending to the stage.

  Examples 1 and 2 in Table 1 are shown in the accompanying FIGS.

  Examples 4 and 5 in Table 1 show that the partially compressed refrigerant stream discharged from the compression stage 26 as the compressor row H or from the compression stage 28 as the compressor row J is sent directly to the maximum pressure compression stage 22. First, it can be sent to the second compression stage 24. Since the second compression stage 24 is part of the same compressor row G, I as the maximum pressure compression stage 22, generally the partially compressed refrigerant stream is further passed through the maximum pressure compression stage 22.

  Also, Example 8 shown in Table 1 includes three compressor rows O, P, and Q, of which compressor rows P and Q include only one compression stage 24 and 26, respectively. However, the partially compressed effluent from each of the low pressure compression stages 24 and 26 can generally pass through the maximum compression stage 22.

  Table 1 relates to an example including four compression stages. The present invention is not limited to this, and configurations including three or five compression stages are also within the scope of the present invention. One skilled in the art can find various combinations of compression stages for different compressor rows, and the effluent from one or more low pressure compression stages as long as all partially compressed streams commonly pass through the maximum pressure compression stage. Can be fed into the inlet of one or more high pressure compression stages.

In summary, a method and compressor configuration for compressing three or more evaporative refrigerant streams by three or more refrigerant compression stages is disclosed.
(I) compressing the first evaporative refrigerant stream (40) in a common maximum pressure compression stage (22) to obtain at least a portion of the fully compressed refrigerant stream (10) at the refrigerant cooling pressure;
(Ii) compressing the other evaporative refrigerant streams (50, 60, 70) in at least two parallel low pressure compression stages (24, 26, 28) to obtain one or more partially compressed refrigerant streams (50a, 60a, 70a); ;
(Iii) Generally, all of the partially compressed refrigerant streams (50a, 60a, 70a) are passed through a common maximum pressure compression stage (22).

  Different arrangements or configurations of the compression stages provide different characteristics for recompression of the refrigerant stream. In this way, the present invention makes the arrangement or configuration more efficient by better matching the compression required for the evaporative refrigerant flow with respect to the accompanying compressor power requirements, or cooling load requirements, or combinations thereof. It gives you the flexibility to do it.

  Those skilled in the art will readily appreciate that the present invention can be modified in many ways without departing from the scope of the claims.

US Pat. No. 6,962,060 US Pat. No. 6,637,238

DESCRIPTION OF SYMBOLS 1 ... Whole structure 3 ... 1st refrigerant circuit 10 ... Refrigerant flow 12 ... 1st heat exchange process 14 ... 2nd heat exchange process 16 ... 3rd heat exchange process 18 ... 4th heat exchange process 20 ... Hydrocarbon flow 22 ... Maximum Pressure compression stage 24 ... second (high pressure) compression stage 26 ... third compression stage 28 ... fourth (low pressure) compression stage 30 ... cooled hydrocarbon stream A ... first compressor row B ... second compressor row

Claims (12)

(A) supplying a refrigerant flow at a cooling pressure;
(B) passing the refrigerant stream through three or more heat exchange processes operating at different pressure levels;
(C) obtaining a cooled hydrocarbon stream by gradually reducing the temperature of the hydrocarbon stream by passing the hydrocarbon stream through at least two of the heat exchange steps of step (b);
(D) expanding a portion of the refrigerant stream at different pressures in each heat exchange step, the step of Ru evaporation, wherein the first heat exchange step of the three or more heat exchange steps, first evaporator refrigerant in the first evaporator pressure flow supplied to at least two other evaporated refrigerant streams at a lower evaporation pressure than the first evaporation pressure is supplied, wherein the second heat exchange step of said at least three heat exchange step the second evaporator refrigerant stream A third heat exchange step of the three or more heat exchange steps supplies at least a third evaporative refrigerant stream ;
(E) compressing the first evaporative refrigerant stream to a cooling pressure by a maximum pressure compression stage of a single compressor casing to obtain at least a portion of the refrigerant stream at the cooling pressure of step (a);
(F) compressing the other evaporative refrigerant stream by two or more parallel low pressure compression stages to obtain two or more partially compressed refrigerant streams; and (g) replacing all of the partially compressed refrigerant streams with the maximum of step (e). A method for cooling a hydrocarbon stream comprising at least a step of passing through a pressure compression stage.   The process of claim 1, wherein the step of passing the hydrocarbon stream through at least two of the heat exchange steps of step (b) comprises passing the hydrocarbon stream through at least three of the heat exchange steps of step (b). Method. The three or more heat exchanging steps of the step (b) include 4 or 5 heat exchanging steps, and by expanding and evaporating the refrigerant flow, 4 or 5 evaporative refrigerant flows at 4 or 5 different pressures, respectively. The method according to claim 1 or 2, wherein: 4. The method of claim 3, wherein the refrigerant stream and the hydrocarbon stream are passed through the same heat exchange step, wherein each heat exchange step gradually reduces the temperature of the hydrocarbon stream .   5. The process according to any one of claims 1 to 4, wherein the step of evaporating a portion of the refrigerant stream in at least two of the heat exchange steps of step (d) comprises heat exchange with a hydrocarbon stream passing through the heat exchange step. The method described.   6. A method according to any one of the preceding claims, wherein the refrigerant stream is propane. A method according to any one of claims 1 to 6, wherein a portion of the refrigerant stream of step (d) expands and evaporates.
In the first heat exchange step, the first portion of the refrigerant flow is expanded and evaporated to obtain a high pressure evaporative refrigerant flow that is a first evaporating pressure, and the high pressure evaporative refrigerant flow is the first evaporative refrigerant flow. Yes,
In the second heat exchange step, the second portion of the refrigerant flow is expanded and evaporated to obtain a high-pressure evaporative refrigerant flow that is the second evaporative refrigerant flow, and a high-pressure evaporative refrigerant having a high pressure lower than the high pressure Get the flow
Expanding the third portion of the refrigerant flow in said third heat exchange step, evaporated, the third to give the intermediate pressure onset refrigerant stream in a vaporized refrigerant stream, and medium pressure with pressure inside is lower than the high-pressure Evaporative refrigerant flow,
Fourth expansion the fourth portion of the refrigerant stream in a heat exchange step, evaporated, the fourth to give the low-pressure evaporated refrigerant stream is evaporated refrigerant stream, and the low-pressure evaporated refrigerant stream having a lower pressure in the lower pressure the And
Wherein said compression of the first evaporative refrigerant stream in step (e) is
Compressing the most intermediate pressure onset refrigerant stream by most pressure compression stage wherein a maximum pressure compression stage of step (e), comprises Rukoto give the refrigerant flow in a cooling pressure of step (a), the
Said compression of the other evaporative refrigerant stream of step (f),
Compressing the low pressure evaporative refrigerant stream by a low pressure compression stage, one of the parallel low pressure compression stages ;
Compressing an intermediate pressure evaporative refrigerant stream by an intermediate pressure compression stage, one of the parallel low pressure compression stages ;
Comprises compressing the high-pressure evaporated refrigerant stream by high pressure compression stage,
An intermediate pressure compression stage and an at most pressure compression stage are included in the first compressor row;
Here, the low pressure compression stage and the high pressure compression stage are included in a second compressor row that is at least partially separated from the first compressor row , and the low pressure compression step and the high pressure compression step are the intermediate pressure compression step. In parallel with,
Said method.   8. The second compressor row has an outlet for supplying a partially compressed refrigerant stream, and sends the partially compressed refrigerant stream to an inlet of a high pressure compression stage in the first compressor row. the method of. Wherein at parallel at least two of the low-pressure compression stage, the method according to any one of claims 1 to 6, in 2 or more compressors column. The process according to any one of claims 1 to 9, wherein the hydrocarbon stream comprises natural gas . 11. A process according to any one of the preceding claims, wherein the hydrocarbon stream consists of natural gas. A method of obtaining a liquefied hydrocarbon stream and liquefying a hydrocarbon stream, said method comprising cooling a hydrocarbon stream according to the method of any one of claims 1 to 11.