RU2488759C2 - Method and device for cooling and separation of hydrocarbon flow - Google Patents

Abstract

FIELD: oil and gas industry.

SUBSTANCE: method involves provision of hydrocarbon flow (10), cooling of hydrocarbon flow (10) to obtain liquefied hydrocarbon flow (20), supply at least of some part of liquefied hydrocarbon flow (20) to distillating column (12) through the first inlet opening (17), provision of bottom raw material flow (30), provision of cooling agent circuit (4) containing at least one cooling agent flow (40), heating of bottom raw material flow (30) with counterflow (40) of cooling agent to obtain heated bottom raw material flow (50) and flow (60) of cooled cooling agent; supply of heated bottom raw material flow (50) to distilling column (12) through the second inlet opening (18) located below the first inlet opening (17) and separation of partially liquefied hydrocarbon flow (20) in distilling column (12) to obtain the first upper gaseous flow (70) and the first bottom liquid flow (80).

EFFECT: use of the invention will allow reducing power consumption for cooling process of a cooling agent.

17 cl, 5 dwg, 2 tbl

Description

The present invention relates to a method and apparatus for cooling and separating a hydrocarbon stream, in particular, but not exclusively, natural gas and, if required, for subsequent liquefaction of the hydrocarbon stream. In another aspect, the present invention relates to a liquefaction apparatus comprising such a device.

Several methods are known for cooling and liquefying a natural gas stream to produce liquefied natural gas (LNG). It is desirable to liquefy a natural gas stream for a number of reasons. For example, it is easier to store and transport natural gas over long distances in a liquid state than in a gaseous state, since it takes up a smaller volume and does not require high pressure for storage.

The liquefaction of a hydrocarbon stream, for example natural gas, generally includes two or more stages of cooling, and one or more stages of separation. At least one stage of separation of the natural gas stream is required to reduce the content of hydrocarbons heavier than methane, hereinafter referred to as "heavier hydrocarbons". Traditionally, heavier hydrocarbons are separated from the natural gas stream prior to any significant cooling and, in particular, liquefaction, for several reasons, in particular because their solidification temperature or liquefaction temperature is different from the corresponding methane temperature, and they can block parts methane liquefaction plants.

The separation of the heavier hydrocarbons from natural gas can be accomplished by cooling the natural gas to partially condensate it and then using a distillation column.

US Pat. No. 5,960,644 describes a method for removing carbon dioxide, ethane and heavier components from a high pressure natural gas stream, wherein the high pressure natural gas stream partially condenses and passes through the first and second separators before different natural gas streams enter the distillation column . In order to bring heat to the bottom of the distillation column, the liquid stream is removed from the distillation column and heated in a heat exchanger 46 to produce a re-boiling stream, and the re-boiling stream is introduced into the distillation column.

US Pat. No. 5,960,644 uses an external refrigerant to partially condense the high pressure natural gas stream and uses a heating medium to supply heat to the bottom of the distillation column. The external refrigerant used to partially condense the high-pressure natural gas stream is not described, and the heating medium is a compressed gaseous product stream that requires separate compression to create pressure in the pipeline.

The objective of the present invention is to reduce the energy that is necessary to provide a given mode of cooling the refrigerant in the refrigerant circuit.

The present invention provides a method for cooling and separating a hydrocarbon stream, for example natural gas, comprising at least the following steps:

(a) providing a hydrocarbon stream;

(b) cooling the hydrocarbon stream to produce a partially liquefied hydrocarbon stream, wherein at least a portion of the cooling is provided by partially or completely evaporating the cooled refrigerant stream;

(c) the entry of at least part of the partially liquefied hydrocarbon stream into the distillation column through the first inlet;

(d) provision of bottom feed stream;

(e) providing a refrigerant circuit comprising at least a stream of compressed, fully liquefied refrigerant;

(f) heating the lower feed stream with a countercurrent refrigerant stream to produce a heated lower feed stream and a cooled refrigerant stream;

(g) entering the heated lower feed stream into the distillation column through a second inlet located below the first inlet; and

(h) separating the partially liquefied hydrocarbon stream in a distillation column to obtain at least a first upper gaseous stream and a first bottom liquid stream.

The present invention also provides a device for cooling and separating a hydrocarbon stream, for example natural gas, comprising at least:

a first cooling stage for cooling a hydrocarbon stream and obtaining a partially liquefied hydrocarbon stream;

a distillation column for receiving and separating at least a fraction from the partially liquefied hydrocarbon stream entering through the first inlet;

a refrigerant circuit comprising at least one stream of compressed, fully liquefied refrigerant; and

a first heat exchanger for heating the lower feed stream with a countercurrent stream of compressed, fully liquefied refrigerant to produce a cooled refrigerant stream and a heated lower feed stream, which must enter the distillation column through a second inlet located below the first inlet; and

a heat exchange system in the first cooling stage, located in the refrigerant circuit downstream of the first heat exchanger, for cooling a hydrocarbon stream with a countercurrent stream containing at least a fraction of the cooled refrigerant stream, thereby partially or completely evaporating at least a fraction of the cooled refrigerant stream .

The present invention also provides a liquefaction apparatus comprising the apparatus described herein.

Embodiments of the present invention will now be described only as examples with reference to the accompanying non-limiting drawings.

1 is a diagram of a first method for cooling and separating a hydrocarbon stream according to one embodiment of the present invention.

2 is a diagram of a second method for cooling and separating a hydrocarbon stream according to a second embodiment of the present invention as part of a liquefaction plant.

3 is a diagram of a third method for cooling and separating a hydrocarbon stream according to a third embodiment of the present invention.

4 is a diagram of a fourth method for cooling and separating a hydrocarbon stream according to a fourth embodiment of the present invention.

5 is a diagram of a fifth method for cooling and separating a hydrocarbon stream according to a fifth embodiment of the present invention.

In embodiments of the present invention, a refrigerant stream is used to heat the bottom feed stream entering the distillation column. The resulting refrigerant refrigerant stream is then used primarily to cool the hydrocarbon stream in order to partially condense or facilitate partial condensation of the hydrocarbon stream before at least a portion of it is fed to the distillation column.

Figure 1 presents a generalized diagram of the proposed method for cooling and separation of a hydrocarbon stream, for example natural gas, comprising at least the following steps:

(a) providing hydrocarbon stream 10;

(b) cooling the hydrocarbon stream 10 to obtain a partially liquefied hydrocarbon stream 20;

(c) the entry of at least part of the partially liquefied hydrocarbon stream 20 into the distillation column 12 through the first inlet 17;

(d) providing a bottom feed stream 30;

(e) providing a refrigerant circuit 4 comprising at least a refrigerant stream 40;

(f) heating the bottom feed stream 30 with a countercurrent refrigerant stream 40 to produce a heated bottom feed stream and a cooled refrigerant stream 60;

(g) the entry of the heated lower feed stream 50 into the distillation column 12 through a second inlet 18 located gravitationally below the first inlet 17; and

(h) separating the partially liquefied hydrocarbon stream 20 in the distillation column 12 to obtain at least a first upper gaseous stream 70 and a first bottom liquid stream 80.

In a preferred embodiment of the invention, the cooling in step (b) is carried out by partially or completely evaporating the cooled refrigerant stream 60, for example, a supercooled liquefied refrigerant stream. In yet another preferred embodiment, in steps (e) and (f), the refrigerant stream 40 is a compressed, fully liquefied refrigerant stream, for example, the cooled refrigerant stream 60 produced in step (f) is a supercooled liquefied refrigerant stream.

When using a compressed, fully liquefied refrigerant stream to heat the lower feed stream 30, the liquefied refrigerant stream is supercooled. Such a resulting supercooled liquefied refrigerant stream is preferred since less steam is generated when used for cooling, for example, for cooling a hydrocarbon stream.

According to figure 1, there is also provided a device for cooling and separating a hydrocarbon stream, for example, natural gas. The device comprises at least:

a first cooling stage 14 for cooling the hydrocarbon stream 10 and obtaining a partially liquefied hydrocarbon stream 20;

a distillation column 12 for receiving and separating at least one fraction from the partially liquefied hydrocarbon stream 20 entering through the first inlet 17;

a refrigerant circuit 4 comprising at least one refrigerant stream 40; and

a first heat exchanger 16 for heating the lower feed stream 30 with a countercurrent refrigerant stream 40 to produce a heated feed stream 50, which must enter the distillation column 12 through a second inlet 18 located gravitationally below the first inlet 17.

In a preferred embodiment, the device further comprises a heat exchange system 34 in a first cooling stage 14 located downstream of the first heat exchanger 16 to produce at least a fraction of the cooled refrigerant stream 60 and to cool the hydrocarbon stream 10 with a countercurrent stream, at least , the specified fraction of the cooled refrigerant stream 60, wherein the refrigerant stream 60 is partially or completely vaporized. The chilled refrigerant stream 60 is preferably a supercooled liquefied refrigerant stream. In another preferred embodiment, the refrigerant stream 40 in the refrigerant circuit 4 is a compressed, fully liquefied refrigerant stream.

One of the advantages of cooling the refrigerant stream through heat exchange with the lower feed stream is that in this case, the cooling capacity of the refrigerant stream used to cool the hydrocarbon stream and, if necessary, to cool other streams increases.

Another advantage of the present invention is that when cooling the refrigerant stream by heat exchange with the lower feed stream, less energy is required for compression in the refrigerant circuit to provide the same refrigerant capacity in the circuit, for example, to cool the hydrocarbon stream.

Thus, the present invention provides a method in which energy costs are reduced to provide the cooling capacity needed to cool and separate the same amount of hydrocarbons.

Opening in more detail, figure 1 presents a method of cooling and separating a hydrocarbon stream 10 according to one embodiment of the invention,

The hydrocarbon stream 10 may be any suitable hydrocarbon stream, for example, but not limited to, a hydrocarbon-containing gas stream that can be cooled. One example is a natural gas stream obtained from a natural gas or oil reservoir. Alternative to the natural gas stream, a hydrocarbon stream from another source can also be obtained through a synthesis process, for example, the Fischer-Tropsch process.

Typically, such a hydrocarbon stream contains mainly methane. Preferably, such a hydrocarbon stream contains at least 50 mol% of methane, more preferably at least 80 mol% of methane.

Although the method according to the present invention is applicable to various hydrocarbon streams, it is particularly suitable for natural gas streams to be liquefied. Since those skilled in the art know how to liquefy a hydrocarbon stream, this process is not described in detail here.

Depending on the source, the hydrocarbon stream 10 may contain one or more compounds that are not hydrocarbons, for example, H ₂ O, N ₂ , CO ₂ , Hg, H ₂ S and other sulfur compounds.

If necessary, the hydrocarbon stream 10 may be pretreated before use, which may be part of the process for cooling the hydrocarbon stream, or may be carried out separately. This pretreatment may include the reduction and / or removal of non-hydrocarbon compounds, for example, CO ₂ and H ₂ S, or other steps, for example, initial cooling and preliminary pressurization. Since these steps are known to those skilled in the art, their mechanisms are not further described here.

Thus, the term “hydrocarbon stream”, in the sense in which it is used here, also means a composition before any treatment, such processing, which includes cleaning, dehydration and / or washing, as well as any composition partially, substantially or completely processed for reducing and / or removing one or more compounds or substances, including, but not limited to sulfur, sulfur compounds, carbon dioxide and water.

The hydrocarbon stream used in the present invention is preferably subjected to at least the minimum pre-treatment required to provide subsequent liquefaction of the hydrocarbon stream. Said treatment required for liquefying natural gas is known in the art.

In the hydrocarbon stream 10, the hydrocarbon content may also be heavier than methane, for example, ethane, propane, butanes and pentanes, as well as some aromatic hydrocarbons. The composition of the hydrocarbon stream varies depending on the type and location of the hydrocarbon stream such as natural gas. Hydrocarbons heavier than methane should generally be removed from natural gas for several reasons, for example, because their solidification temperature or liquefaction temperature is different from the corresponding methane temperature, and they may block parts of the methane liquefaction plant. C ₂ -C ₄ hydrocarbons can be used as a source of gas condensate liquids and / or refrigerant. The removal of heavier hydrocarbons than methane is often referred to as the "removal of natural gas condensate."

1 shows a hydrocarbon stream 10 containing natural gas, which is cooled in the first cooling stage 14 to produce a cooled and partially liquefied hydrocarbon stream 20. Cooling in the first cooling stage 14 may cause partial condensation of the hydrocarbon stream 10.

The first cooling stage 14 may comprise a heat exchange system 34, for example, in the form of one or more heat exchangers such as boilers connected in parallel, in series, or both by methods known in the art. The cooling in the first cooling stage 14 is provided by the refrigerant stream 15 of the first cooling stage, which is heated and partially or completely evaporated in the first cooling stage 14, forming a heated refrigerant stream 15a of the first cooling stage.

The cooling of the hydrocarbon stream 10 by means of the refrigerant stream 15 of the first cooling stage may be part of a liquefaction process, for example, a pre-cooling step including, if required, a propane refrigerant circuit, as described hereinafter with reference to FIG. 2, or cooling may be a separate process. Therefore, the refrigerant stream 15 of the first cooling stage may be part of the flow of one or more refrigerant circuits described later, or may be provided separately.

When the hydrocarbon stream 10 is cooled, the temperature of the hydrocarbon stream 10 may be below 0 ° C, for example, may be in the range from -10 ° C to -70 ° C.

At least one fraction, if required, all fractions of the partially liquefied hydrocarbon stream 20 from the first cooling stage 14 enters the distillation column 12 through the first inlet 17.

The distillation column 12 may be of any suitable size and design known in the art. A conventional distillation column is a scrubber or scrubber column and, as a rule, operates at a pressure exceeding atmospheric pressure, moreover, its operation is known in the art. One of the tasks of the distillation column 12 is to obtain, as a rule, a gaseous stream enriched in methane, which makes it most suitable for subsequent liquefaction.

The corresponding operating parameters of the distillation column 12 are known in the art and can be changed to change the composition of at least one of the outgoing main product streams. Typically, two main product streams emerge from the distillation column 12, namely, an overhead stream, partially or completely gaseous, and a bottom stream, typically at least partially liquid, or completely liquid. From hydrocarbon stream 10, the bottom stream is enriched in hydrocarbons heavier than methane, in particular, butanes, pentanes and heavier hydrocarbons.

As is known in the art, in order to reduce the amount of methane that can leave the distillation column 12 as part of the bottom stream, a heated stream is supplied to the bottom of the distillation column 12, or in the vicinity of the bottom, to help raise methane from the bottom of the distillation column 12 so that he, passing into a gaseous state, exited the distillation column 12 as part of the gaseous overhead stream. Such a stream, traditionally heated in a separate boiler, is usually called a “re-boiling stream”

In this regard, figure 1 shows the lower feed stream 30, designed to provide heating of the bottom of the distillation column 12, or near the bottom, known in the art using a re-boiling stream. Traditionally, as described above, the heat for the re-boiling stream is provided by a separate boiler, which requires a special heat source, the energy of which cannot be recovered.

According to the method of the present invention, the lower feed stream 30 passes through a first heat exchanger 16 to provide heating of the lower feed stream 30 to a countercurrent stream 40 of compressed, fully liquefied refrigerant, described in more detail below. By exchanging heat in the first heat exchanger 16, a heated lower feed stream 50 is provided, which enters the distillation column 12 through a second inlet 18 located below the first inlet 17, preferably at or near the bottom of the distillation column. As a result, heating is provided, preferably, of the bottom of the distillation column 12, or near the bottom, due to which methane entering the distillation column 20 in a partially liquefied hydrocarbon stream leaves the distillation column 12 as part of the upper gaseous stream 70.

The distillation column 12 preferably provides a first upper gaseous stream 70 containing more than 80 mol% of methane and having a temperature below 0 ° C, more preferably in the range of -20 ° C to -40 ° C. The distillation column 12 shown in FIG. 1 also provides a first bottom liquid stream 80, typically enriched in hydrocarbons heavier than methane

Compressed, fully liquefied refrigerant stream 40 is an integral part of the first refrigerant circuit 4, several schemes of which are shown in FIGS. 2, 3 and 4, and will be described hereinafter by way of example only.

The first refrigerant circuit 4 comprises at least one refrigerant compressor and at least one refrigerant stream. In the refrigerant circuit, one or more refrigerant streams can be separated and / or combined one or more times to provide cooling of one or more other streams, blocks, liquids, etc., in a manner known in the art, typically by passing through one or more heat exchangers. Cooling by means of each refrigerant stream (which is a full stream or fraction, or part of it) is achieved by partially or completely evaporating the refrigerant stream at low pressure by a method known in the art, moreover, low pressure is provided by passing the refrigerant stream through one or more valves and / or other expanders.

Each refrigerant stream used in the present invention may be formed from a single component, for example propane or nitrogen, or may be a mixed refrigerant formed from a mixture of two or more components selected from the group consisting of: nitrogen, methane, ethane, ethylene, propane, propylene, butanes, pentanes, etc.

At various stages, sections or stages of any part of the process for cooling a hydrocarbon stream, similar or different types of refrigerants can be used in a manner known to those skilled in the art, which does not limit the present invention.

The first heat exchanger 16 may include one or more heat exchangers connected in parallel, in series, or both by methods known in the art.

Compressed, fully liquefied refrigerant stream 40 typically has a temperature above 0 ° C, for example, in the range of 10 to 70 ° C. The temperature of the cooled refrigerant stream 60, which will be a supercooled liquefied refrigerant stream, is lower than the temperature of the refrigerant stream 40.

By providing a compressed refrigerant stream 40 that is completely liquefied, the cooling capacity required for the lower feed stream 30 is reduced compared to using the corresponding compressed vapor or only a partially liquefied refrigerant stream. Thus, the heat supply to the lower feed stream 30 provided by the compressed, fully liquefied refrigerant stream 40 can be controlled and, more specifically, reduced compared to the heat supply when using the partially or fully evaporated refrigerant stream, while providing a heated lower feed stream with a temperature suitable for optimizing the separation of the hydrocarbon stream in the distillation column 12. Using a partially or completely evaporated refrigerant stream may require too much xoy refrigerating lower feed stream 30, and therefore, the heated lower feed stream 50 would be too hot, reducing the separation efficiency of the distillation column. Thus, a system is proposed in which the cooling capacity of the lower feed stream 30 corresponds to that required for the stream 40 of compressed, fully liquefied refrigerant.

The cooled, for example supercooled, liquefied refrigerant stream 60 subsequently partially or completely evaporates and provides cooling, being an integral part of the first refrigerant circuit 4. At least one fraction of the chilled hydrocarbon stream 10 is created by partially or completely evaporating the chilled, for example supercooled, liquefied refrigerant stream 60. By cooling the compressed, fully liquefied refrigerant stream 40, a cooled refrigerant stream 60 is provided as a supercooled liquefied refrigerant stream, while in the process of cooling the hydrocarbon stream 10, the production of steam generated during throttling is reduced. The first refrigerant circuit 4 may be connected to or separated from the first hydrocarbon stream processing system 10 and / or with the first upper gaseous stream 70.

Examples of schemes for providing a lower feed stream 30, compressed, fully liquefied refrigerant stream 40, chilled, for example supercooled, liquefied refrigerant stream 60, and a first refrigerant circuit 4 are described hereinafter, but the present invention is not limited to this.

FIG. 2 shows a hydrocarbon stream 10 passing through a first cooling stage 14 to provide a partially liquefied hydrocarbon stream 20, which is completely supplied to the distillation column 12 through a first inlet 17 to obtain a first upper gaseous stream 70 and a first bottom liquid stream 80, as described above.

2 also shows a compressed, fully liquefied refrigerant stream 40 passing through the first heat exchanger 16 to provide a cooled, for example supercooled, liquefied refrigerant stream 60, as described above.

In accordance with one possible embodiment of the present invention, FIG. 2 shows a first refrigerant circuit 4 comprising one or more first refrigerant compressors 42. The refrigerant flowing through the primary refrigerant circuit 4 may be any suitable refrigerant consisting of a single component, for example propane, or may be a mixed refrigerant. The refrigerant compressor includes any unit, device or apparatus capable of increasing the pressure of the refrigerant stream. These include single-stage compression refrigerant compressors or multi-stage compression refrigerant compressors. At some stages or steps of a hydrocarbon cooling process, two or more refrigerant compressors connected in parallel, in series, or both can be used. The present invention is not limited to the type, layout, or arrangement of a refrigerant compressor or refrigerant compressors, in particular in any refrigerant circuit.

As part of the first refrigerant circuit 4, the first refrigerant compressor 42 provides a first compressed refrigerant stream 44 that passes through one or more refrigerators, for example a water and / or air cooler 46, providing a cooled compressed refrigerant stream 48 that enters the accumulator 52 known in method in the art.

The drive 52 provides an accumulated stream 54, which is completely liquefied. Typically, at least a portion of the accumulated stream 54 functions as a first refrigerant refrigerant stream 56 that is throttled and / or vaporized through a corresponding valve 58, providing a throttled refrigerant stream 62 (which can act as a refrigerant stream 15 of the first cooling stage, as shown in 1) extending into the first cooling stage 14 in order to at least partially cool the hydrocarbon stream 10 and provide a heated refrigerant stream 75 (similar to the first refrigerant heated stream 15a of the refrigerant and cooling, as shown in Figure 1), which is returned to the first compressor 42 of the refrigerant.

Figure 2 also shows a variant of dividing the accumulated stream 54 by a stream divider 64 to provide a stream 40 of compressed, fully liquefied refrigerant. To provide the required subsequent heat exchanges, a proportion of the streams 56, 40 separated from the accumulated stream 54 can be calculated.

2, the compressed, fully liquefied refrigerant stream 40 provided by the flow divider 64, after being compressed in the first refrigerant compressor 42, is a relatively warm stream. At least a portion of this heat can be used to heat the lower feed stream 30 before using the liquefied refrigerant stream 60 cooled by the lower feed stream, for example supercooled, which functions as a normal refrigerant stream.

The refrigerant stream 60 cooled by the lower feed stream may function as a normal refrigerant stream at any suitable place or places, and in any suitable heat exchange system including any suitable heat exchangers and / or cooling stages, or used as part of the present method for cooling and separating a hydrocarbon stream , and / or be used elsewhere in liquefaction unit 1, and / or in an independent process or installation. Thus, the refrigerant circuit 4 may include a heat exchange system located downstream of the first heat exchanger 16, wherein at least one fraction of the cooled, for example supercooled, liquefied refrigerant stream 60 can be used to cool another stream.

At least one fraction of the cooled, for example supercooled, liquefied refrigerant stream 60, at least partially cools the hydrocarbon stream 10. This can be achieved by passing the cooled, for example supercooled, liquefied refrigerant stream 60 through valve 19 to provide a throttled stream 60a refrigerant entering the first cooling stage 14. All heated / warm refrigerant from the first refrigeration stage 14 can be returned to the first refrigerant compressor 42 via line 75.

Thus, at least one fraction, if all fractions are required, of a chilled, for example supercooled, liquefied refrigerant stream 60 provides, in the first cooling stage 14, at least partial cooling of at least part or all of the hydrocarbon stream 10.

FIG. 3 shows a number of other and / or alternative embodiments of the present invention using the first refrigerant circuit 4 of FIG. 2.

In the first alternative embodiment of the present invention shown in FIG. 3, at least one fraction, if all fractions are required, of the first bottom liquid stream 80 provides a bottom feed stream 30 that passes through the first heat exchanger 16 to produce a heated bottom feed stream 50 If required, the heated lower feed stream 50 enters the lower feed gas / liquid separator 51, which may be external or internal to the distillation column 12, providing a second upper gas a typical stream 50a used in the distillation column 12, and a second bottom stream 50b used as a natural gas condensate stream.

Figure 3 also shows a cooled, for example supercooled, liquefied refrigerant stream 60, which, passing through valve 19, provides a stream 60a of at least partially cooled hydrocarbon stream 10 in the first cooling stage 14. As a result, a separate heated refrigerant stream 60b exiting the first cooling stage 14 is provided, which can return to the first refrigerant compressor 42 as part of the return stream 75, as described above (along with a throttled refrigerant stream 62 also passing to the first cooling stage 14) , or separately, may return to the first refrigerant compressor 42 in any other suitable place, for example, as a 60 s return flow (shown, for clarity, by the dashed line in FIG. 3), upstream of the first refrigerant compressor 42 enta.

Figure 3 also shows a variant of dividing the accumulated stream 54 by means of a stream divider 64 to ensure, as a rule, the predominance of a second refrigerant stream 66, which can be throttled by valve 68 to provide cooling in the second heat exchanger 72, as described below, and to provide a second return flow 74 to refrigerant compressor 42. The second heat exchanger 72 can be connected, combined or combined with the first cooling stage 14 by a method known in the art.

FIG. 3 also shows non-limiting examples of alternative sources of compressed, fully liquefied refrigerant stream 40 leaving the first refrigerant circuit 4.

By way of example, the compressed stream 44 leaving the refrigerant compressor 42 can be separated by a flow divider to provide a first separated stream 76, as a source of refrigerant stream, to the refrigerator 46.

Alternatively, the source of refrigerant stream 40 may be a separate source, for example, a separate refrigerant circuit.

For example, FIG. 3 also shows a second refrigerant circuit 6 comprising one or more second refrigerant compressors 82 capable of providing a second compressed refrigerant stream 84, which then passes through one or more second refrigerators 86 and then through a second heat exchanger 72 to provide cooled second compressed stream 92. The cooled second compressed stream 92 shown in FIG. 3 passes through a third separator 94, typically to provide a lighter top stream 96 and a heavier bottom stream 98. Lighter top This stream 96 and the heavier lower stream 98 are known in the art through a third heat exchanger 102 for cooling, separately throttled outside the third heat exchanger 102 and then returned back to cool the flows passing through the third heat exchanger 102. As a result, a second refrigerant return flow 104 to a second refrigerant compressor 82.

The third heat exchanger 102 may be fully or partially included in the second cooling stage for the implementation of the process of cooling the hydrocarbon stream. Preferably, the second cooling stage is separated from the first cooling stage. Thus, the second cooling stage contains one or more separate heat exchangers that use a second refrigerant circulating in the second refrigerant circuit, although the refrigerant of the second refrigerant circuit can also pass through one or more heat exchangers of the first cooling stage. This second cooling stage is sometimes also called the “main cooling” stage.

The second refrigerant circuit 6 may provide one or more portions of the stream or separated streams, as a source of compressed, fully liquefied refrigerant stream 40, in a manner similar to that described above for the first refrigerant circuit 4. For example, the second compressed refrigerant stream 84 may be divided to provide a third separated stream 106, and the second refrigerant stream, passing through the refrigerator 86, may provide a fourth separated stream 108.

Similarly, the heated refrigerant stream 60b from the first cooling stage 14 can be returned to the second refrigerant circuit 6 at any suitable place, for example, as a third return stream 60d after the second heat exchanger 72, or as a fourth return stream 60e entering the third separator 94.

3, at least one fraction, preferably all fractions, of the first upper gaseous stream 70 leaving the distillation column 12 is subsequently liquefied in the third heat exchanger 102 to produce a liquefied hydrocarbon stream 120, for example, liquefied natural gas.

4, similarly to FIGS. 1-3, shows a hydrocarbon stream 10 cooled in a heat exchanger system 34a of a first cooling stage 14 to produce a partially liquefied hydrocarbon stream 20.

According to another alternative embodiment of the present invention, FIG. 4 shows that the hydrocarbon stream 10 can be separated by a stream divider 21 into at least one first partial stream 10a and one second partial stream 10b by a method known in the art. When dividing the hydrocarbon stream 10 into the first and second partial streams 10a, 10b, their proportion or ratio can be any. Preferably, any partial stream that must enter the distillation column 12 through the first inlet 17 is the predominant hydrocarbon stream 10, for example, as described in WO 2006/061400 A1, incorporated herein by reference.

The first partial feed stream 10a passes through the heat exchange system 34a in the first cooling stage 14, as described above, to obtain a partially liquefied hydrocarbon stream 20, which enters the distillation column 12.

The second partial stream 10b provides a lower feed stream 30 entering the first heat exchanger 16 to produce a heated lower feed stream 50, which also enters the distillation column 12.

As shown in figures 2 and 3, the flow of refrigerant 40 can be provided from the first refrigerant circuit 4 after the accumulator 52, if necessary, its source may be a fraction of the second refrigerant stream 66 supplied to the second heat exchanger 72 (not shown in figure 4), which is designated as fractional flow 78.

According to another alternative embodiment of the present invention, the hydrocarbon stream 10 is provided with an initial stream 8, which passes through the fourth heat exchanger 112, which may contain one or more heat exchangers connected in series, in parallel or both. The fourth heat exchanger 112 may form part of the first cooling stage 14. Cooling in the fourth heat exchanger 112 can be provided either by means of a chilled, for example supercooled liquefied refrigerant stream 60 after passing through valve 19 to provide a throttled refrigerant stream 60a, and / or by at least one fraction of the throttled refrigerant stream 62 in the first circuit 4 refrigerant before it is used as the refrigerant stream 15 of the first cooling stage in the first cooling stage 14. The dashed line 63 in the drawing shows the flow of a possible refrigerant stream to the fourth heat exchanger 112, and the return line 63a shows the return path of the throttled refrigerant stream 60a and any possible refrigerant stream 63 to the first refrigerant circuit 4 after being used in the fourth heat exchanger 112. Possible second fraction of the throttled stream 60g refrigerant may be supplied to the heat exchange system 34a of the first cooling stage 14. FIG. 4 shows a second fraction of the throttled refrigerant stream 60g flowing into the refrigerant stream 15 of the first cooling stage, which is then supplied to the heat exchange system 34a of the first cooling stage 14.

If desired, the fourth heat exchanger 112 may be part of the first cooling stage 14.

Thus, FIG. 4 shows embodiments of the present invention, wherein one fraction of a hydrocarbon stream 10 provides at least one fraction of a lower feed stream 30, preferably by dividing the hydrocarbon stream 10 into at least first and second partial streams 10a, 10b, wherein the first partial stream 10a is cooled to produce a partially liquefied hydrocarbon stream 20, and the second partial stream 10 provides at least one fraction of the lower feed stream 30.

FIGS. 3 and 4 also show various options for providing cooling in the first cooling stage 14 and various options for using a chilled, for example supercooled, liquefied refrigerant stream 60 to provide cooling, preferably as part of a refrigerant circuit 4, by one or more of the same or different heat exchangers.

Figure 5 shows additional alternative embodiments of the present invention.

Figure 5 shows that the hydrocarbon stream 10 passes through the first cooling stage 14, as described above, to provide a partially liquefied hydrocarbon stream 20, which is fed to the separator 32 of the gas / liquid feed stream to obtain the upper feed gas stream 100a and bottom feed liquid stream 100b.

At least one fraction, preferably all fractions, of the bottom feed stream 100b provides a bottom feed stream 30, which passes through the first heat exchanger 16 to produce a heated bottom feed stream 50, and then enters the distillation column 12, as described above.

In this case, at least one fraction, preferably all fractions, of the upper gaseous feed stream 100a passes through the fifth heat exchanger 116 to obtain a cooled, partially liquefied hydrocarbon stream 20a, which also enters the distillation column 12. Cooling in the fifth heat exchanger 116 can be provided known in the art by a suitable cooling stream and / or refrigerant stream 114 from one or more sources of the refrigerant stream described herein, or from at least one fraction of which is obtained from a refrigerated, for example supercooled, liquefied refrigerant stream 60 to provide another heated refrigerant stream 114a.

By cooling the upper gaseous feed stream 100a, the temperature difference between the subsequently cooled, partially liquefied hydrocarbon stream 20a and the heated lower feed stream 50 increases when they enter the distillation column 12, thereby increasing separation, or increasing the separation efficiency of the contents of the distillation column 12 to the first upper gaseous stream 70 and the first bottom liquid stream 80, while preferably, the amount of methane that leaves the distillation is increased the column 12 in the composition of the first upper gaseous stream 70.

Coming out of the distillation column 12, the first gaseous overhead stream 70 passes through a second cooling stage 22 containing one or more heat exchangers connected in parallel, in series, or both by methods known in the art. If desired, the second cooling stage 22 may comprise a third heat exchanger 102 and a cold second compressed stream 92 shown in FIG.

From the second cooling stage 22, the partially, preferably completely, liquefied hydrocarbon stream 120 passes to a final separator, for example, to an instantaneous evaporation device 24, to provide a resulting overhead stream, for example, throttle gas 24a and a resulting bottom stream, for example, enriched liquefied hydrocarbon stream 90.

According to another embodiment of the present invention, if at least one fraction 90b of the resulting bottom stream 90 is required is separated from the main product stream 90a (e.g., liquefied natural gas). By pump 94, fraction 90b provides a secondary lower feed stream 30a that passes through a secondary heat exchanger 16a to provide a secondary heated lower feed stream 50a that goes directly to the distillation column 12. Heating of the secondary lower feed stream 30a can be provided by a secondary refrigerant stream 40a , which is the same stream 40 of compressed, fully liquefied refrigerant, a fraction thereof, or may be isolated from it. The secondary heat exchanger 16a provides a cooled secondary refrigerant stream 60f, which may be combined with or associated with the cooled refrigerant stream 60f, or may be used separately. Thus, more than one heated lower feed stream may be introduced into the distillation column 12, which are separate or combined into a single stream.

The present invention provides a preferred method of using at least one fraction of a refrigerant stream to heat rather than cool another stream, before using it as part of the refrigerant stream in the refrigerant circuit as a medium for countercurrent cooling of the other stream. Said refrigerant stream may be supplied from different places in the refrigerant circuit, and the heated refrigerant stream may be returned to the refrigerant circuit in different suitable places. Thus, the present invention provides the flexibility of supplying a refrigerant stream from a refrigerant circuit and the flexibility of returning a refrigerant stream to a refrigerant circuit.

The summary table 1 below shows the phases, mass flow rates, pressures, temperatures and compositions of some of the streams used in the illustrative process in accordance with the diagram shown in figure 2.

Table 1 V = steam, L = liquid Flow Phase Total mass flow Temperature Pressure C1 C2 + kg / s ° C bar mol% 10 V / L 209.3 20,0 60.0 0.825 0.17 10a V / L 146.5 20,0 60.0 0.825 0.17 twenty V / L 146.5 -37.0 59.0 0.825 0.17 thirty V / L 62.8 20,0 60.0 0.825 0.17 40 L 66.1 52.0 18.5 0,000 1.00 44 V 142.0 83.7 19.0 0,000 1.00 48 L 142.0 52.0 18.5 0,000 1.00 fifty V / L 62.8 50,0 59.5 0.825 0.17 54 L 142.0 52.0 18.5 0,000 1.00 56 L 75.8 52.0 18.5 0.00 1.00 60 L 66.1 22.4 18.2 0,000 1.00 60a V / L 66.1 -40.0 1,1 0,000 1.00 62 V / L 75.8 -40.0 1,1 0,000 1.00 70 V 165.5 -25.2 58.0 0.884 0.10 75 V 142.0 -39.9 1,1 0,000 1.00 80 L 43.8 -39.9 1,1 0,000 1,0

According to the present invention, moreover, the energy consumption for compression is reduced, and less cooling is required in the first refrigerant circuit, since cooling is provided by the flow of refrigerant cooled by heating the lower feed stream in the heat exchanger.

Table 2 below shows the data on power consumption by the first cooling stage 14, the first heat exchanger 16, the first refrigerant compressor 42 and an additional refrigerator (s) 46 for:

(i) an example according to the present invention shown in FIG. 2; and

(ii) a comparative example with a similar circuit of the primary refrigerant circuit, but with the provision of separate or external heating of the first heat exchanger heating the lower feed stream (supplied as one fraction of the hydrocarbon stream), moreover, the heating stream is subsequently not used in the first refrigerant circuit. The first refrigerant circuit in the comparative example is used only to provide the aforementioned cooling in the first cooling stage.

table 2 Power consumption (kW) Device Comparative Example (ii) Example according to the invention (i) Relative difference (%) fourteen 31530 31530 0,0% 16 6130 6130 0,0% 46 61450 49500 -19.4% 42 29920 24110 -19.4%

The data shown in table 2 confirm that in accordance with the embodiment of the present invention shown in figure 2, the energy required for the first refrigerant compressor 42 is reduced by about 20%, and similarly by about 20%, the cooling capacity of the first refrigerator (s) 46. As a result, a substantial reduction in energy consumption and cooling capacity is achieved when producing a liquefied hydrocarbon stream on an industrial scale.

The data shown in table 2 confirm that, in accordance with the embodiment of the present invention, shown in figure 2, the energy consumption for compression in the refrigerant circuit is reduced to provide the same cooling capacity as in the comparative example, which leads to a decrease in the total the energy required for cooling and separating the hydrocarbon stream is the same as in the comparative example, which is equivalent to the example shown in US patent No. 5960644.

Those skilled in the art will understand that the present invention can be carried out in many different ways without departing from the scope of the following claims.

Claims (17)

1. A method of cooling and separating a hydrocarbon stream, for example natural gas, comprising at least the following steps:
(a) providing a hydrocarbon stream;
(b) cooling the hydrocarbon stream to produce a partially liquefied hydrocarbon stream, wherein at least a portion of the cooling is provided by partially or completely evaporating the cooled refrigerant stream;
(c) the entry of at least part of the partially liquefied hydrocarbon stream into the distillation column through the first inlet;
(d) provision of bottom feed stream;
(e) providing a refrigerant circuit comprising at least one stream of compressed, fully liquefied refrigerant;
(f) heating the lower feed stream with a countercurrent stream of compressed, fully liquefied refrigerant to produce a heated lower feed stream and a cooled refrigerant stream;
(g) supplying the heated lower feed stream to the distillation column through a second inlet located below the first inlet; and
(h) separating the partially liquefied hydrocarbon stream in a distillation column to obtain at least a first upper gaseous stream and a first bottom liquid stream. 2. The method according to claim 1, in which at least one fraction of the first bottom liquid stream provides at least one fraction of the lower feed stream. 3. The method according to claim 1, in which one fraction of the hydrocarbon stream provides at least one fraction of the lower feed stream. 4. The method according to claim 3, in which the hydrocarbon stream is divided into at least first and second partial streams, wherein the first partial stream is cooled to obtain a partially liquefied hydrocarbon stream, and the second partial stream provides at least one fraction of the lower feed stream. 5. The method according to claim 1, in which one fraction of the partially liquefied hydrocarbon stream provides at least one fraction of the lower feed stream. 6. The method according to claim 5, in which the partially liquefied hydrocarbon stream is fed into the first gas / liquid separator to obtain an upper feed gas stream and to obtain a bottom feed liquid stream, wherein at least one fraction of the upper feed gas stream is supplied to the first inlet of the distillation column and at least one fraction of the bottom feed liquid stream provides at least one fraction of the lower feed stream. 7. The method according to claim 1, in which at least one fraction of the first upper gaseous stream is at least partially condensed and fed to the final gas / liquid separator to provide at least a final bottom stream, wherein at least one fraction of the final bottom stream is a lower feed stream. 8. The method of claim 1, wherein the compressed, fully liquefied refrigerant stream is propane. 9. The method according to one of the preceding paragraphs, in which at least a portion of the cooling in step (b) is provided with a refrigerant circuit. 10. The method according to one of claims 1 to 8, in which the refrigerant circuit contains one or more refrigerant compressors, and the stream of compressed, fully liquefied refrigerant is provided from the refrigerant circuit located downstream of the refrigerant compressor (s). 11. The method according to one of claims 1 to 8, in which the refrigerant circuit contains one or more refrigerant storage, and the stream of compressed, fully liquefied refrigerant is provided from the refrigerant storage. 12. The method according to one of claims 1 to 8, in which at least one fraction of the first upper gaseous stream is subsequently liquefied to provide a liquefied hydrocarbon stream, for example liquefied natural gas. 13. The method according to claim 9, in which at least one fraction of the first upper gaseous stream is subsequently liquefied to provide a liquefied hydrocarbon stream, such as liquefied natural gas. 14. The method of claim 10, in which at least one fraction of the first upper gaseous stream is subsequently liquefied to provide a liquefied hydrocarbon stream, such as liquefied natural gas. 15. The method according to claim 11, in which at least one fraction of the first upper gaseous stream is subsequently liquefied to provide a liquefied hydrocarbon stream, such as liquefied natural gas. 16. A device for cooling and separating a hydrocarbon stream, for example natural gas, containing at least:
a first cooling stage for cooling a hydrocarbon stream and obtaining a partially liquefied hydrocarbon stream;
a distillation column for receiving and separating at least one fraction from the partially liquefied hydrocarbon stream entering through the first inlet;
a refrigerant circuit comprising at least one stream of compressed, fully liquefied refrigerant;
a first heat exchanger for heating the lower feed stream with a countercurrent stream of compressed, fully liquefied refrigerant to produce a cooled refrigerant stream and a heated lower feed stream, which must enter the distillation column through a second inlet located below the first inlet; and
a heat exchange system in the first cooling stage, which is located in the refrigerant circuit downstream of the first heat exchanger, for cooling a hydrocarbon stream by a counterflow stream, at least a fraction of a cooled refrigerant stream, thereby partially or completely evaporating at least said stream fraction refrigerated refrigerant. 17. The liquefaction installation containing the device according to clause 16.

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