JP2009543894A - Method and apparatus for liquefying a hydrocarbon stream - Google Patents

Abstract

  A method of liquefying a hydrocarbon stream, such as natural gas, from a feed stream (10), wherein (a) the feed stream (10) is passed through a mixed refrigerant circulating in a heat exchanger (12), Obtaining an at least partially liquefied hydrocarbon stream (20) having a temperature of less than −100 ° C .; (b) from the heat exchanger (12) with the mixed refrigerant as a liquid and vapor refrigerant effluent stream (80). (C) passing the liquid and vapor refrigerant outflow (80) through the first separator (18) to obtain a vapor refrigerant stream (90) and a liquid refrigerant stream (110); ) Circulating the liquid refrigerant stream (110) of step (c) to the heat exchanger (12) of step (a) without substantial heat exchange; (e) compressing the vapor refrigerant stream (90) And obtaining a compressed refrigerant stream (95); (f) the compressed refrigerant stream 95) cooling to obtain a cooled compressed stream (100) having a temperature below 0 ° C .; and (g) the cooled compressed stream (100) being converted into the heat exchanger (12) of step (a). Circulating to the method.

Description

  The present invention relates to a method and apparatus for liquefying a hydrocarbon stream, such as natural gas, particularly in a liquefied natural gas production process.

  Several methods are known for liquefying a natural gas stream to obtain liquefied natural gas (LNG). It is desirable for the natural gas stream to liquefy for several reasons. As an example, when natural gas is stored or transported over a long distance, it is easier to use liquid than gas. This is because the liquid occupies a smaller volume and does not need to be stored at high pressure.

  EP1008823B1 relates to a method for liquefying a pressurized feed gas, wherein a feed stream and various refrigerant streams are sent to a heat exchanger. The exit stream of the mixed refrigerant is collected as steam from the heat exchanger, compressed, cooled, and discharged to obtain the vapor refrigerant and liquid refrigerant, which are mixed or separately reintroduced into the heat exchanger. The problem with all configurations shown in EP 1008823B1 is that when the refrigerant outlet stream is completely steam, the heat exchanger cools the feed stream along its length with a high heat transfer coefficient characteristic of evaporative cooling. That is not. Therefore, there is a problem that the cooling capacity of the heat exchanger is not maximized.

  DE 199 76 623 A1 relates to a process for liquefying a hydrocarbon-rich stream. In this method, indirect heat exchange with the coolant is performed, and each coolant mixture that exits exists as a two-phase flow before compression. In each stage of the heat exchange, after the two phases of the evaporating coolant flowing out are separated, the liquid phase is mixed with the recompressed gas phase before recirculation. In the second heat exchanger E2 and the third heat exchanger E3 in FIG. 1, the remixed coolant is cooled by the preceding heat exchangers E1 and E1 + E2, respectively.

  In DE 19937623 A1, the system is not inefficient if the two phases are at the same temperature, for example + 40 ° C., when these two phases are mixed for the first stage coolant streams 13 and 14 of FIG. The remixed first coolant stream 10 is sufficiently cooled by the heat exchanger E1 before being used as a coolant stream through the heat exchanger E1.

  The problem with the configuration shown in DE 199 762 623 A1 is that remixing of the streams 24 and 25 after the separator D3 and the third stage coolant streams 35 and 36 after the separator D4 occurs. The liquid coolant streams 24 and 35 separated from the two phase streams 23 and 34 will be at the same temperature as the two phase streams 23 and 34, respectively, for example about -40 ° C and about -100 ° C. However, the separated gas streams 25 and 36 become relatively hot after being recompressed by the compressors C3 and C4, and even with the water cooling devices E6 and E7, the temperature of the stream after C3 and C4. Is usually higher than + 40 ° C., for example. Remixing stream 24 (−40 ° C.) and stream 25 (about + 40 ° C.) produces an intermediate temperature stream 20. Such mixing for significantly different (offset) temperature streams 24 and 25 is inefficient.

  Also, the mixed coolant stream 20 needs to be cooled close to the desired −40 ° C. for stream 21 before entering heat exchanger E2. This cooling is performed by the heat exchanger E1, and therefore further work (ie removal of excess heat) must be performed not only on the streams 10 and 1, but also on the stream 20.

  This inefficient situation is further magnified with remixing of streams 35 and 36. These temperature shifts during mixing are greater than in streams 24 and 25, stream 30 requires pre-cooling by both heat exchangers E1 and E2, and both these heat exchangers do extra work. There must be.

  It is an object of the present invention to maximize heat transfer in a heat transfer region in a liquefaction heat exchanger, particularly a liquefaction plant that includes, but is not limited to, a liquefaction device.

  Another object of the present invention is to reduce energy inefficiencies caused by temperature shifts when using and / or remixing separated coolant streams.

  Another object is to provide another more efficient method and apparatus for liquefying natural gas.

One or more of the above or other purposes,
A method for liquefying a hydrocarbon stream, such as natural gas, from a feed stream,
(A) passing the feed stream through a mixed refrigerant circulating in a heat exchanger to obtain an at least partially liquefied hydrocarbon stream having a temperature of less than -100 ° C;
(B) causing the mixed refrigerant to flow out of the heat exchanger as a liquid and vapor refrigerant outflow;
(C) passing the liquid and vapor refrigerant outflow through a first separator to obtain a vapor refrigerant stream and a liquid refrigerant stream;
(D) circulating the liquid refrigerant stream of step (c) to the heat exchanger of step (a) without substantial heat exchange;
(E) compressing the vapor refrigerant stream of step (c) to obtain a compressed refrigerant stream;
(F) cooling the compressed refrigerant stream to obtain a cooled compressed stream having a temperature below 0 ° C .; and (g) circulating the cooled compressed stream to the heat exchanger of step (a). ;
Can be achieved by the present invention which provides said method comprising at least:

  The mixed refrigerant flowing out is a combination of liquid and vapor. That is, the mixed refrigerant is not completely vaporized when it flows out of the liquefied heat exchanger. Therefore, the cooling is still affected by the vaporization of the mixed refrigerant in the entire length or the entire range of the mixed refrigerant cooling passage until it flows out through the heat exchanger. This increases the heat transfer coefficient in the final range of heat transfer area or volume for cooling, i.e. the heat transfer surface available to the mixed refrigerant in the heat exchanger.

  The cooling carried out by the heat exchanger at least partially, preferably entirely, brings the liquefied hydrocarbon stream below -100 ° C., for example to obtain liquefied natural gas. Such cooling is well known in the main cryogenic cooling techniques for hydrocarbon streams such as natural gas.

  In the present invention, the liquid refrigerant stream separated from the liquid and vapor refrigerant effluent is directly returned to the heat exchanger and recirculated without the need for heat exchange by passing through another heat exchanger or cooling device. However, usually some minimal heat exchange may occur to help reduce or maintain the temperature of the liquid refrigerant stream slightly. Such heat exchange is negligible and does not significantly change the temperature of the liquid refrigerant stream. That is, the liquid refrigerant flow between the separation of the liquid refrigerant stream from the liquid and vapor refrigerant effluent and its recirculation directly or indirectly (eg, in combination with another flow) to the heat exchanger. The temperature change should be less than 40 ° C, preferably less than 30 ° C or less than 20 ° C or even less than 10 ° C. Due to the location or arrangement of the liquid refrigerant stream (e.g. the length or position of the piping that feeds the liquid refrigerant stream into the heat exchanger) and / or proximity to other flows or combinations with other refrigerant streams Some minimal heat exchange may still occur in the refrigerant stream. Such minimal heat exchange should also be below 40 ° C., preferably below 30 ° C. or below 20 ° C. or even below 10 ° C. (if there is no heat exchange at all).

  By avoiding any substantial heat exchange or having only minimal heat exchange, the advantages of the present invention are that the mismatched “cold” and “hot” refrigerant streams are mixed or combined together or It is to make the hydrocarbon stream liquefaction process more efficient without recombination. Such recombination of mismatched streams with significantly different temperatures requires extra cooling to be used for liquefaction of the hydrocarbon stream as shown in DE 1993762A1.

  WO 2006/007278 A2 shows a general refrigerant flow configuration in a plate fin heat exchanger configuration. FIG. 4 of this document shows the use of two heat exchangers, where the liquid stream from separators 510A and 520B is collected and pumped and mixed with the compressed vapor stream from the same separator (recirculation). To form a liquid stream 404 that is completely condensed in the first heat exchanger 200). However, this is due to the temperature mismatch by mixing the cold liquid stream (from the separator) with the sufficiently hot vapor stream (after its compression), ie a set of By compromising the total energy that can be converted into work with respect to the reference ambient conditions, there is the problem that the efficiency is reduced despite the provision of a steam cooler. Nevertheless, the recirculating mixed stream 402 is a mixed liquid and vapor stream.

  US 4,112,700 shows a configuration with natural gas four heat exchanger precooling, where the first multi-component mixture exits the fourth precooling heat exchanger in a liquid and vapor mixed phase, There is no direct recirculation of that liquid phase to the same precooling heat exchanger. Also, no consideration is given to the exergy benefits of minimizing the temperature mismatch of the liquid refrigerant flow below 0 ° C. into the low temperature main heat exchanger.

  US 4,180,123 shows a configuration in which a mixed two-phase stream leaves the heat exchanger, but only the liquid phase is recycled to this heat exchanger after the involvement of two coolers. Again, no consideration is given to the exergy benefits of minimizing the temperature mismatch of the liquid refrigerant flow below 0 ° C. into the low temperature main heat exchanger. Another advantage of the present invention is that the first liquid refrigerant stream separated from the mixed refrigerant effluent is recirculated to the heat exchanger as at least a portion of the total mixed refrigerant for cooling the heat exchanger. The liquefaction process can be made more efficient since the required power input is reduced.

  The process of the present invention can be applied to various hydrocarbon feed streams, but is particularly suitable for natural gas streams to be liquefied.

  One skilled in the art will also readily appreciate that the liquefied natural gas may be further processed if necessary after liquefaction. As an example, the resulting LNG may be depressurized by a Joule-Thomson valve or a cold turboexpander. Further, further intermediate processing steps may be performed between gas / liquid separation and cooling in the gas / liquid separation container.

  The hydrocarbon stream can be any suitable gas stream to be treated, but is usually a natural gas stream obtained from a natural gas or oil reservoir. Alternatively, the natural gas stream can be obtained from other sources, including synthetic sources such as the Fischer-Tropsch process.

  Usually the natural gas stream consists essentially of methane. Preferably the feed stream comprises at least 60 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. Natural gas streams may also contain non-hydrocarbons such as H ₂ O, N ₂ , CO ₂ , H ₂ S, other sulfur compounds, and the like.

If necessary, the feed stream containing natural gas may be pre-treated before being fed to the (cold) main heat exchanger. This pretreatment may include reduction and / or removal of unwanted components such as CO ₂ and H ₂ S, or other steps such as pre-cooling, pre-pressurization. These steps are well known to those skilled in the art and will not be further described here.

The term “natural gas” as used herein relates to any hydrocarbon-containing composition that is at least substantially methane. This includes not only includes the composition of the pretreatment including cleaning and scrubbing, but are not limited to sulfur, carbon dioxide, water, and C ₂ ⁺ 1 or more, including hydrocarbon compounds or Compositions that have been partially, substantially, or fully processed to reduce and / or remove substances are included.

  The separator can be any vessel, apparatus, tower or configuration that can separate the mixed refrigerant into a vapor refrigerant stream and a liquid refrigerant stream. Such separators are well known in the art and will not be further described here.

  A heat exchanger is any tower that can pass multiple streams and can affect direct or indirect heat exchange between one or more refrigerant lines and one or more feed streams. , Tower, device or configuration. Examples include a tube-in-shell type heat exchanger and a spool type heat exchanger. Preferably, the heat exchanger is a cold spool wound heat exchanger.

The present invention also provides
(A) passing the feed stream through the mixed refrigerant circulating in the heat exchanger to obtain a cooled hydrocarbon stream;
(B) allowing the mixed refrigerant to flow out of the heat exchanger as a liquid and vapor refrigerant outflow;
(C) passing the refrigerant and liquid refrigerant outflow streams through a first separator to obtain a vapor refrigerant stream and a liquid refrigerant stream; and (d) directing the liquid refrigerant stream of step (c) directly to the heat exchanger. Recirculating;
A process for treating a hydrocarbon stream, such as natural gas, from a feed stream comprising at least
The present invention includes any combination or all combinations of the methods described above.

The present invention is further an apparatus for liquefying a hydrocarbon stream such as natural gas from a feed stream,
A heat exchanger for liquefying the hydrocarbon stream relative to a mixed refrigerant stream, the feed inlet for the feed stream and a supply for a stream at least partially liquefied the feed stream Said heat exchanger having a raw material outlet, one or more mixed refrigerant inlets, and a mixed refrigerant outlet for vapor and liquid refrigerant outflow;
A first outlet for obtaining a vapor refrigerant flow and a second outlet for obtaining a liquid refrigerant flow are for separating the liquid and vapor refrigerant outflow into vapor and liquid. Separators;
A refrigerant inlet of the heat exchanger for flowing the liquid refrigerant stream into the heat exchanger;
A compressor for compressing the vapor refrigerant stream to obtain a compressed refrigerant stream;
One or more cooling devices for cooling the compressed refrigerant stream to obtain a cooled compressed stream having a temperature below 0 ° C .; and a passage for circulating the cooled compressed stream to the heat exchanger;
A device comprising at least the above is provided.
In the following, aspects of the present invention will be described, by way of example and not limitation, with reference to the accompanying drawings, 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.

1 is a schematic diagram of a processing method according to an embodiment of the present invention.

  Referring to the drawings, FIG. 1 illustrates a method for liquefying a hydrocarbon feed stream 10. The feed stream 10 may be a pretreated natural gas stream in which one or more substances or compounds (such as sulfur, sulfur compounds, carbon dioxide, and moisture or water) are known, as is known in the art. Are preferably removed, preferably completely or substantially.

  Optionally, feed stream 10 may go through one or more precooling stages known in the art. One or more of such precooling stages may include one or more cooling circuits. As an example, a natural gas feed stream is generally processed from an initial temperature of 30-50 ° C (eg, 40 ° C). Following one or more precooling stages, the temperature of the natural gas feed stream can be lowered to -30 to -70 ° C (eg, -40 ° C to -50 ° C).

  In FIG. 1, the heat exchanger 12 is preferably a spool-wound cryogenic heat exchanger with three lines passing completely or partially through the heat exchanger. Low temperature heat exchangers are known in the art and can have various configurations consisting of a feed stream and a refrigerant stream. In addition, such a heat exchanger may also include one or more extending into the heat exchanger to route other fluids (eg, other cooling stages or portions of the process, preferably a refrigerant stream for a liquefaction plant). It is also possible to have For simplicity, FIG. 1 does not show such other lines or flows.

  Feedstock stream 10 enters heat exchanger 12 from feedstock inlet 52, passes through heat exchanger 12 through line 150, and exits from feedstock outlet 54 to provide at least partially liquefied hydrocarbon stream 20. . This liquefied stream 20 is preferably fully liquefied and may be further processed as described below. If the liquefied stream 20 is liquefied natural gas, the temperature can be, for example, about −150 ° C.

  The liquefaction of the feed stream 10 is defined by the refrigerant circuit 160. The refrigerant circuit 160 circulates a mixed refrigerant, which is preferably a gas mixture, more preferably selected from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane, pentane, and the like. As is known in the art, the composition of this mixed refrigerant can vary according to the conditions and parameters desired for the heat exchanger 12.

  Many configurations are known for refrigerant flow through the refrigerant inlet, outlet, and heat exchanger that affect the cooling of the feed stream. One or more lines of refrigerant through the heat exchanger can also be cooled by the heat exchanger rather than affecting cooling in another line or stream.

  In the configuration shown in FIG. 1, the vapor refrigerant inflow 30 passes from the first inlet 66 along the conduit 130 through the heat exchanger 12 and flows out from the first refrigerant outlet 68. When passing through the conduit 130, the vapor refrigerant inflow 30 is cooled and / or liquefied so that the first refrigerant outflow 45 is a liquid stream. In order to obtain a first reduced pressure refrigerant stream 50 that is both vapor and liquid, the first refrigerant outlet stream 45 passes through one or more pressure reducing devices (such as the throttle valve 14). This first reduced pressure refrigerant stream 50 can reenter the heat exchanger 12 through the inlet 72 and pass through the heat exchanger 12 downwardly from the first distribution manifold 34 in a manner known in the art. When the refrigerant flow passes through the heat exchanger 12 downwardly from the first distribution manifold 34, the liquid refrigerant partially changes from liquid to vapor, so that the feed flow line 150 and the vapor refrigerant flow line 130 Is cooled with a high heat transfer coefficient.

  The heat exchanger 12 also has a liquid refrigerant inflow 40 that enters the heat exchanger from the inlet 64 and travels along the conduit 140 through the heat exchanger 12. This exits the heat exchanger 12 at an outlet 74 at an intermediate level between the top and bottom to provide a second refrigerant effluent 60 that reduces its pressure through the expander 16 to a second. , Which are both liquid and vapor, return from the inlet 76 to the heat exchanger 12 and pass through the heat exchanger 12 downwardly from the second distribution manifold 36.

  Preferably, the pressures of the first and second reduced pressure refrigerant streams 50 and 70 are essentially the same. That is, even if there is a difference in pressure, it is not large and does not affect the operation of the heat exchanger 12.

  So far, the liquid phase change refrigerant stream for recycling in prior art heat exchangers can be completely phase changed to steam and can be collected as a steam outlet stream. This created two main areas or zones within the prior art heat exchanger. In the first zone, the liquid in the refrigerant stream of liquid and vapor changes phase to vapor so that the feedstock stream can be cooled and the refrigerant stream is also cooled. In this zone, the heat exchanger can be defined as operating in “wet mode”.

  At the end of the phase change, there is a second zone, which is an area or region within the heat exchanger (generally below the first zone) in which the refrigerant is completely vapor. Since no phase change occurs anymore in the second zone, i.e. a single gas phase, there is a heat transfer region in the heat exchanger that is only cooled with a rather low heat transfer rate. Although some cooling can still occur during the temperature change of the steam, the heat transfer coefficient from the steam is much smaller than the heat transfer coefficient of the liquid changing to steam. Thus, the second zone of the prior art heat exchanger is significantly less efficient in cooling feed streams and the like.

  In FIG. 1 of the present invention, the refrigerant flow flowing downward in the heat exchanger 12 flows out of the heat exchanger 12 as a liquid and vapor refrigerant outflow 80 at the outlet 62. Since the outflow 80 still contains liquid refrigerant, a liquid phase change occurs between the first and second distribution manifolds 24 and 26 and the outlet 62 in the heat exchanger 12. Thus, there is an area or region in the heat exchanger 12 where there is no heat transfer or minimal heat transfer such that the refrigerant is only steam. That is, there is no or minimal area or region where the downward flowing refrigerant stream does not provide the most efficient heat transfer (at a high heat transfer rate), so the most efficient cooling is the feed stream. To line 150 (and other lines). In this way, the heat transfer area or region in the heat exchanger 12 for heat exchange with the feed stream 10 is maximized. This increases the effective heat transfer area in some cases by more than 10% for the same physical heat exchanger size and shape.

  In general, the heat exchanger 12 operates at a low pressure of 1 to 10 bar. Since the temperature at the bottom of the heat exchanger 12 can be in the range of −30 to −50 ° C., the refrigerant outflow 80 is also at the same temperature.

  Vapor and liquid refrigerant effluent stream 80 is routed from inlet 78 to first liquid / vapor separator 18 which also operates at a low pressure such as 1-10 bar. The first separator 18 separates the refrigerant effluent stream 80 in a manner known in the art to provide a vapor refrigerant stream 90 from the first outlet 82 and a liquid refrigerant stream 110 (generally −30 from the second outlet 84. Having the same range of temperature between 0 ° C. and −50 ° C.).

  The vapor refrigerant stream 90 can be compressed by any method known in the art that requires one or more compressors and one or more coolers. FIG. 1 shows a compressor 22 by way of example, which provides a compressed stream 95 having a temperature of about 75 ° C. by way of example only. This compressed stream 95 is then cooled by a water and / or air cooling device 24 and another cooling device 25, preferably with a cooled compressed refrigerant stream 100 having a temperature in the range of −30 ° C. to −50 ° C. give.

  Optionally, the separate cooling device 25 also cools at least some of the feed stream 10 as it is pre-cooled before the heat exchanger 12, as described above.

  The cooled compressed refrigerant stream 100 can be returned directly to the heat exchanger 12. Preferably, the stream 100 is sent from the inlet 86 to the second separator 26 to obtain the vapor refrigerant inflow 30 from the first outlet 88 and the liquid refrigerant inflow 40 from the second outlet 92. The second separator operates at a relatively high pressure, such as in the range of 30-60 bar, preferably 40-55 bar.

  For the path back to the heat exchanger 12, the liquid refrigerant stream 110 can be mixed with the cooled compressed refrigerant stream 100 before the second separator 26, or the liquid refrigerant stream 110 can be second separated. The liquid refrigerant stream 110 can be re-entered into the heat exchanger 12 separately from the other refrigerant streams. The liquid refrigerant stream 110 is recirculated to the heat exchanger 12 without substantial heat exchange of the liquid refrigerant stream 110 between the outlet 84 of the first liquid / vapor separator 18 and the inlet of the heat exchanger 12. . Preferably, no heat exchange of the liquid refrigerant stream 110 occurs between the outlet 84 of the first liquid / vapor separator 18 and the inlet of the heat exchanger 12.

  Preferably, the liquid refrigerant inlet stream 40 and the liquid refrigerant stream 110 (via pump 94) are routed through a mixer 28, such as a junction or union, to provide a mixed liquid refrigerant stream 120 as an inlet 64. To re-enter heat exchanger 12.

  Preferably, the temperature difference between the liquid refrigerant stream 110 and the cooled compressed refrigerant stream 100 (and the liquid refrigerant inflow 40 that is at or substantially the same temperature as the cooled compressed refrigerant stream 100) is 10 ° C. It is less than, Preferably it is less than 5 degreeC or less than 3 degreeC. Because these temperatures are so close together, the exergy loss required to balance these temperatures before reentering the heat exchanger 12 is minimized.

  By way of example, the temperature of the liquid and vapor refrigerant effluent stream 80 can be in the range of −40 ° C. to −50 ° C., so that the liquid refrigerant stream 110 from the first separator 18 is at or near that temperature. Slightly lower temperature. When the temperature range of the liquid refrigerant inflow 40 from the second separator 26 is also in the range of −40 ° C. to −50 ° C., the mixed liquid refrigerant stream 120 obtained by mixing them by the mixer 28 is close thereto. (For example, a range of −45 ° C. to −50 ° C.).

  This close and uniform temperature also applies to the introduction of the liquid refrigerant flow 110 as described above.

  The liquefied natural gas 20 from the liquefaction system can be sent for further cooling, for example to a subcooling stage, and / or to a final separator, where it can be used as plant fuel ( Steam can be withdrawn (eg, for gas turbines operating various compressors) and the liquefied natural gas product can be transferred to a storage vessel or other storage or transport device.

The final separator can be an end flash system, which can be used at the downstream end of the supercooling stage to optimize liquefied natural gas (LNG) production. This typically includes an end compressor driven by another electric drive motor. The power required to drive the end compressor is usually less than the compressor power required for the subcooling stage.
Examples of the advantages of the present invention are shown in the data in Table 1 below.

  The first column of Table 1 shows data on the operation of the main heat exchanger (MCHE) in the prior art standard liquefaction method with a throughput of about 17.5 kmol / s. The heat exchanger is composed of a warm tube bundle and a cold tube bundle, each having an effective surface area (UA) of about 60,000 and 13,000 kW / K. The liquid content of the low-pressure refrigerant exiting from the shell side of the heat exchanger is 0%, ie the heat exchanger operates in “dry mode”.

  By changing the refrigerant composition flowing out in accordance with the present invention so that the liquid content of the refrigerant leaving the heat exchanger is 0.5 mol%, the MCHE heat exchanger now operates completely in “wet mode” is doing. As a result of the wet mode operation, the heat transfer coefficient U at the bottom of the heat exchanger is the same over the entire height of the heat exchanger. As shown in the second “wet” column of Table 1, this results in an effective surface area (UA) of the heat exchanger warm tube bundle of about the same refrigerant compression power and physical heat exchanger area. It has increased by 10% and production has increased by about 1.6%. This is a significant increase on an industrial scale.

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

EP1008823B1 DE199393723A1 WO2006 / 007278A2 US 4,112,700 US 4,180,123

10 Hydrocarbon Feed Stream 12 Heat Exchanger 14 Throttle Valve 16 Expander 18 First Separator 20 Liquefied Hydrocarbon Stream 22 Compressor 24 Water Cooling and / or Air Cooling Device 25 Another Cooling Device 26 Second Separation Mixer 28 Mixer 30 Steam refrigerant inflow 34 First distribution manifold 36 Second distribution manifold 40 Liquid refrigerant inflow 45 First refrigerant outflow 50 First reduced pressure refrigerant flow 52 Feedstock inlet 54 Supply Raw material outlet 60 Second refrigerant outlet stream 66 First inlet 68 First refrigerant outlet 70 Second decompressed refrigerant stream 72 Inlet 80 Liquid and vapor refrigerant outlet stream 90 Steam refrigerant stream 94 Pump 95 Compressed refrigerant stream 100 Cooled Compressed Refrigerant Flow 110 Liquid Refrigerant Flow 130 Pipeline 140 Pipeline 150 Pipeline 160 Refrigerant Circuit

Claims (15)

A method for liquefying a hydrocarbon stream, such as natural gas, from a feed stream (10) comprising:
(A) Passing the feed stream (10) through the mixed refrigerant circulating in the heat exchanger (12) to obtain an at least partially liquefied hydrocarbon stream (20) having a temperature below −100 ° C. Process;
(B) allowing the mixed refrigerant to flow out of the heat exchanger (12) as a liquid and vapor refrigerant outflow (80);
(C) passing the liquid and vapor refrigerant effluent stream (80) through a first separator (18) to obtain a vapor refrigerant stream (90) and a liquid refrigerant stream (110);
(D) circulating the liquid refrigerant stream (110) of step (c) to the heat exchanger (12) of step (a) without substantial heat exchange;
(E) compressing the vapor refrigerant stream (90) to obtain a compressed refrigerant stream (95);
(F) cooling the compressed refrigerant stream (95) to obtain a cooled compressed stream (100) having a temperature of less than 0 ° C .; and (g) converting the cooled compressed stream (100) to step (a). Circulating to the heat exchanger (12) of
The method comprising at least   2. The method according to claim 1, wherein the heat exchanger (12) is a tube-in-shell heat exchanger or a spool wound heat exchanger, preferably a low temperature heat exchanger.   The process according to claim 1 or 2, wherein the heat exchanger (12) completely liquefies the feed stream (10).   The method of claim 3, wherein the feed stream (10) is natural gas and the liquefied hydrocarbon stream (20) is liquefied natural gas.   The method according to any one of the preceding claims, wherein the liquid refrigerant stream (110) is circulated to the heat exchanger (12) by a pump (94).   The method according to any one of the preceding claims, wherein the temperature of the liquid refrigerant stream (110) is in the range of -30 ° C to -50 ° C.   The temperature difference between the liquid refrigerant stream (110) and the cooled compressed stream (100) is less than 10 ° C, preferably less than 5 ° C or less than 3 ° C. Method.   The cooled compressed stream (100) is separated prior to circulation to the heat exchanger (12) to obtain a vapor refrigerant inflow (30) and a liquid refrigerant inflow (40). The method according to any one of the above.   The method of claim 8, wherein the liquid refrigerant inflow (40) is mixed with the liquid refrigerant stream (110) of step (c).   The method according to claim 9, wherein the temperature difference between the liquid refrigerant stream (110) and the liquid refrigerant inlet stream (40) is less than 10 ° C, preferably less than 5 ° C or less than 3 ° C. An apparatus for liquefying a hydrocarbon stream, such as natural gas, from a feed stream (10),
A heat exchanger (12) for liquefying said hydrocarbon stream relative to a mixed refrigerant stream, wherein said feed stream (10) for said feed stream (10) and at least a portion of said feed stream Feed outlet (54) for a partially liquefied stream (20), one or more mixed refrigerant inlets (64, 66), and a mixed refrigerant outlet (62) for vapor and liquid refrigerant outflow (80) The heat exchanger (12) having
For separating the liquid and vapor refrigerant outflow (80) into vapor and liquid, the first outlet (82) and the liquid refrigerant flow (110) for obtaining the vapor refrigerant flow (90) A first separator (18) having a second outlet (84) for obtaining;
A refrigerant inlet (64) of the heat exchanger (12) for flowing the liquid refrigerant stream (110) into the heat exchanger (12);
A compressor (22) for compressing said vapor refrigerant stream (90) to obtain a compressed refrigerant stream (95);
One or more cooling devices (24, 25) for cooling the compressed refrigerant stream (95) to obtain a cooled compressed stream (100) having a temperature below 0 ° C; and the cooled compressed stream (100) For circulating the heat to the heat exchanger (12);
At least said device.   The apparatus of claim 11, wherein a pump (94) assists the liquid refrigerant stream (110) to flow toward the heat exchanger (12).   The method of claim 11 or claim 12, further comprising a second separator (26) for separating the cooled compressed stream (100) into a vapor refrigerant inflow (30) and a liquid refrigerant inflow (40). The device described.   The mixer (28) of claim 13, further comprising a mixer (28) for mixing the liquid refrigerant inflow (40) and the liquid refrigerant stream (110) before they return to the heat exchanger (12). apparatus. The heat exchanger (12) includes a first refrigerant line (130) for the vapor refrigerant stream (30), and a second refrigerant liquid inlet stream (40) and a second refrigerant liquid stream (110). 15. A device according to claim 13 or claim 14, comprising a refrigerant line (140).