CN209840520U - Natural gas liquefaction system - Google Patents

Abstract

The application relates to a natural gas liquefaction system belongs to natural gas processing and processing technology field. The natural gas liquefaction system comprises a raw material compression device, a cold box, an LNG throttle valve, a gas-liquid separation device, a precooling heat exchanger and a refrigerant circulation loop; the outlet of the raw material compression device is connected with the first inlet of the cold box through a first pipe section, the first inlet of the cold box is connected with the first outlet of the cold box through a second pipe section, the first outlet of the cold box is connected with the inlet of the gas-liquid separation device through a third pipe section, the LNG throttling valve is arranged on the third pipe section, and the first pipe section or the second pipe section exchanges heat with the refrigerant circulation loop through the precooling heat exchanger. The natural gas liquefaction system adds an external cold source, so that the temperature of the natural gas before throttling is lower, more products can be obtained under the same energy consumption, and the energy consumption can be greatly reduced.

Description

Natural gas liquefaction system

Technical Field

The application relates to the technical field of natural gas processing and treatment, in particular to a natural gas liquefaction system.

Background

In the natural gas liquefaction process flow, the refrigeration mode is divided into two modes, one mode is that an external refrigerant provides cold energy, and a mixed refrigerant, nitrogen expansion and nitrogen methane expansion refrigeration are generally adopted; the other is methane self-expansion or throttling refrigeration, and the process does not need an external refrigerant, has simple flow and higher energy consumption.

Although the refrigeration process using the self-expansion (throttling) is simple in flow, the power consumption is high, and in a natural gas liquefaction plant, the power cost is the maximum operation cost of the plant, and accounts for about 80% of the whole operation cost.

SUMMERY OF THE UTILITY MODEL

The application provides a natural gas liquefaction system has increased external cold source for the natural gas is lower at the temperature before the throttle, under the same energy consumption, can obtain more products, can greatly reduced energy consumption promptly, makes above-mentioned problem obtain improving.

According to one aspect of the application, the natural gas liquefaction system comprises a raw material compression device, a cold box, an LNG throttle valve, a gas-liquid separation device, a precooling heat exchanger and a refrigerant circulation loop; the outlet of the raw material compression device is connected with the first inlet of the cold box through a first pipe section, the first inlet of the cold box is connected with the first outlet of the cold box through a second pipe section, the first outlet of the cold box is connected with the inlet of the gas-liquid separation device through a third pipe section, the LNG throttling valve is arranged on the third pipe section, and the first pipe section or the second pipe section exchanges heat with the refrigerant circulation loop through the precooling heat exchanger.

According to the natural gas liquefaction system of the embodiment of the application, the natural gas is conveyed from the raw material compression device to the gas-liquid separation device through the first pipe section, the second pipe section and the third pipe section. The first pipe section is provided with the precooling heat exchanger, heat exchange between the first pipe section and the refrigerant circulation loop is realized through the precooling heat exchanger, and the natural gas can enter the second pipe section after precooling, so that the heat exchange efficiency (obtaining lower temperature) of the natural gas in the second pipe section is improved; or the second pipe section is provided with the precooling heat exchanger, the heat exchange between the second pipe section and the refrigerant circulation loop is realized through the precooling heat exchanger, and when the natural gas flows in the second pipe section, more cold energy of the heat exchange can be obtained, so that the natural gas has lower temperature when flowing out of the second pipe section (before entering separation throttling). Equivalently, the temperature of the natural gas is reduced under the action of the precooling heat exchanger, the reduced-temperature natural gas can obtain lower temperature after passing through the second pipe section, the heat exchange efficiency of the natural gas in the second pipe section is higher, the natural gas flowing out of the first outlet of the cold box is converted from gaseous state into liquid state, the low-temperature liquid natural gas enters the LNG throttle valve (after pressure reduction, part of the liquid natural gas is converted into gaseous natural gas), under the same energy consumption, the amount of the obtained liquid natural gas after throttling is more, and more products (liquefied natural gas) can be obtained through the gas-liquid separation device; in addition, the amount of gas separated by the gas-liquid separator and required to be returned to the raw material compression device is small. Through the structure, the energy consumption of the system can be greatly reduced by reducing the temperature of the natural gas before separation and throttling.

In addition, the natural gas liquefaction system according to the embodiment of the application has the following additional technical characteristics:

according to some embodiments of the application, the second tube section exchanges heat with the refrigerant circulation loop through a pre-cooling heat exchanger, and the pre-cooling heat exchanger is disposed outside the cold box.

In the above embodiment, the pre-cooling heat exchanger is located outside the cold box, the second pipe section is divided into two parts by the pre-cooling heat exchanger, one part is located inside the cold box, and the other part is located outside the cold box, which is equivalent to the fact that the pre-cooling heat exchanger and the refrigerant circulation loop are externally connected to the cold box, and therefore installation, maintenance and replacement of the pre-cooling heat exchanger and the refrigerant circulation loop are facilitated. When natural gas flows through the second pipe section, the arrangement of the precooling heat exchanger provides cold energy brought by the refrigerant circulation loop for the second pipe section, so that the heat exchange efficiency of the natural gas in the second pipe section is improved, and the natural gas can obtain lower temperature when flowing out of the second pipe section.

According to some embodiments of the present application, a refrigerant compressor, a refrigerant cooler and a refrigerant throttle valve are disposed on the refrigerant circulation loop, a refrigerant inlet of the refrigerant compressor is connected to a refrigerant outlet of the precooling heat exchanger, a refrigerant inlet of the refrigerant cooler is connected to a refrigerant outlet of the refrigerant compressor, a refrigerant outlet of the refrigerant cooler is connected to a refrigerant inlet of the precooling heat exchanger through the refrigerant throttle valve, the refrigerant cooler includes a cooling medium inlet and a cooling medium outlet, and the cooling medium inlet and the cooling medium outlet are respectively used for being connected to an external cooling medium.

In the above embodiment, the refrigerant circulating loop is composed of the refrigerant compressor, the refrigerant cooler, the refrigerant throttle valve and the precooling heat exchanger, and the refrigerant circulates in the circulating loop and can provide heat exchange for the natural gas in the first pipe section or the second pipe section, so that the natural gas is precooled, and the effect of cooling the natural gas is achieved.

According to some embodiments of the application, the liquid outlet of the gas-liquid separation device is connected with the product collection device through a fourth pipe section, the gas outlet of the gas-liquid separation device is connected with the second inlet of the cold box through a fifth pipe section, the second inlet of the cold box is connected with the second outlet of the cold box through a sixth pipe section, and the second outlet of the cold box is connected with the return air port of the raw material compression device through a seventh pipe section.

In the above embodiment, the liquefied natural gas flowing out of the liquid outlet of the gas-liquid separation device enters the product collection device through the fourth pipe section, so that the liquefied natural gas can be collected conveniently. And the gaseous natural gas flowing out of the gas outlet of the gas-liquid separation device returns to the raw material compression device through the fifth pipe section, the sixth pipe section and the seventh pipe section, so that the gaseous natural gas is convenient to recycle, and after the gaseous natural gas returns to the raw material compression device, the mixed raw material natural gas is liquefied again, so that more liquid natural gas is further obtained.

According to some embodiments of the present application, the gas-liquid separation device includes a plurality of stages of gas-liquid separators arranged in series, a liquid outlet of each stage of gas-liquid separator is connected to a lower stage of gas-liquid separator through a transition pipe section, and a transition throttle valve is provided on the transition pipe section.

In the above embodiment, the multistage separation is realized by the multistage gas-liquid separator, and the separation efficiency and the separation accuracy are improved.

According to some embodiments of the application, the cold box is provided with a plurality of second inlets and a plurality of second outlets, the gas outlet of each stage of gas-liquid separator corresponds to one second inlet, the raw material compression device comprises a plurality of compression cylinders arranged in series, one second outlet corresponds to one compression cylinder, the second outlet is connected with the return air port of the corresponding compression cylinder through a seventh pipe section, and the outlet pipe section of each compression cylinder is provided with a raw material cooler.

In the above embodiment, the gas outlet of each stage of gas-liquid separator corresponds to one second inlet, each second outlet corresponds to one compression cylinder, and the gaseous natural gas with different pressures returns to different compression cylinders, so that the circulating natural gas with different pressures is matched with the corresponding compression cylinders, and the efficacy of the compression cylinders is reasonably utilized. In addition, the outlet of the compression cylinder is provided with the raw material cooler, so that the temperature of the gas output by the compression cylinder can be reduced, and the energy consumption of the cold box is prevented from being improved due to the overhigh temperature of the gas output by the raw material compression device.

According to some embodiments of the present application, the feedstock compression device comprises a multi-stage booster compressor comprising a plurality of compression cylinders arranged in series, the plurality of compression cylinders forming a multi-stage compression cylinder.

In the embodiment, the natural gas is pressurized in multiple stages through one multi-stage booster compressor, so that the structural compactness of the system is improved, and the installation space is saved.

According to some embodiments of the present application, the feedstock compression device comprises a plurality of compressors arranged in series, each compressor comprising a compression cylinder.

In the above embodiment, the arrangement of the plurality of compressors can increase the matching effect between the raw material compression device and the gas-liquid separation device, thereby facilitating the replacement and maintenance of the compressors and improving the maintenance efficiency.

Additional aspects and advantages of the present application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the present application.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

FIG. 1 is a schematic diagram of a natural gas liquefaction train configuration provided by an embodiment of the present application;

FIG. 2 is another schematic diagram of a natural gas liquefaction train configuration provided by embodiments of the present application.

Icon: 100-natural gas liquefaction systems; 1-a raw material compression device; 11-a compression cylinder; 12-a feedstock cooler; 2-a cold box; 21-a first inlet; 22-a first outlet; 23-a second inlet; 24-a second outlet; 31-an LNG throttling valve; 4-a gas-liquid separation device; 41-gas-liquid separator; 42-a transition pipe section; 43-transition throttle valve; 5-precooling a heat exchanger; 6-refrigerant circulation loop; 61-refrigerant compressor; 62-refrigerant cooler; 621-cooling medium inlet; 622 — cooling medium outlet; 63-refrigerant throttle valve; 64-an eighth pipe section; 65-a ninth tube section; 66-tenth tube section; 71-a first tube section; 72-a second tube section; 73-a third tube section; 74-a fourth tube segment; 75-a fifth tube segment; 76-a sixth tube segment; 77-seventh pipe section.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, generally described and illustrated in the figures herein, can be arranged and designed in a wide variety of different configurations.

Thus, the following detailed description of the embodiments of the present application, presented in the accompanying drawings, is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present application, it should be noted that the terms "inside", "outside", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the application usually place when using, and are only used for convenience in describing the present application and simplifying the description, but do not indicate or imply that the devices or elements that are referred to must have a specific orientation, be constructed in a specific orientation, and operate, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and the like are used merely to distinguish one description from another, and are not to be construed as indicating or implying relative importance.

In the description of the present application, it is also to be noted that, unless otherwise explicitly specified or limited, the terms "disposed" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.

A natural gas liquefaction system 100 in accordance with an embodiment of an aspect of the present application is described below with reference to the figures.

As shown in fig. 1, a natural gas liquefaction system 100 according to an embodiment of the present application includes: raw material compression device 1, cold box 2, LNG choke valve 31, gas-liquid separation device 4, precooling heat exchanger 5 and refrigerant circulation circuit 6.

Specifically, the raw material compression device 1 functions to pressurize the natural gas, thereby obtaining high-pressure natural gas. The cold box 2 comprises a first inlet 21 and a first outlet 22, the first inlet 21 (inlet of raw material natural gas or high-pressure normal-temperature natural gas) is connected with the outlet of the raw material compression device 1 through a first pipe section 71, and the first outlet 22 (outlet of natural gas after precooling) of the cold box 2 is connected with the first inlet 21 of the cold box 2 through a second pipe section 72; the first outlet 22 of the cold box 2 is connected with the inlet of the gas-liquid separation device 4 through a third pipe section 73, and the LNG throttling valve 31 is arranged on the third pipe section 73. The raw material natural gas is compressed by the raw material compression device 1 and then enters the cold box 2 through the first pipe section 71 and the first inlet 21; the natural gas is pre-cooled in the second pipe section 72, so that the natural gas flowing out of the first outlet 22 has a lower temperature, and when the low-temperature natural gas (fully liquefied) flowing out of the cold box 2 flows through the LNG throttling valve 31 in the third pipe section 73, the high-pressure natural gas is converted into low-pressure natural gas, and part of the liquefied natural gas is converted into gaseous natural gas. The pre-cooling heat exchanger 5 is arranged on the first pipe section 71 or the second pipe section 72, heat exchange between the first pipe section 71 or the second pipe section 72 and the refrigerant circulation loop 6 is realized through the pre-cooling heat exchanger 5, and natural gas can obtain lower temperature after two-stage pre-cooling of the pre-cooling heat exchanger 5 and the cold box 2, so that the natural gas has lower temperature when flowing out of the second pipe section 72 (before entering the LNG throttling valve 31).

According to the natural gas liquefaction system 100 of the embodiment of the present application, the natural gas is transferred from the raw material compression device 1 to the gas-liquid separation device 4 through the first pipe section 71, the second pipe section 72, and the third pipe section 73. By arranging the precooling heat exchanger 5, the precooling heat exchanger 5 is communicated with the refrigerant circulation loop 6, the natural gas in the second pipe section 72 is changed into low-temperature natural gas after primary precooling by the precooling heat exchanger 5, and the low-temperature natural gas is subjected to secondary precooling under the action of the cold box 2, so that the refrigerating capacity is increased (or the power consumption required for liquefying the same natural gas is reduced) compared with the method of simply depending on the gaseous reflux low-temperature natural gas (mainly methane gas) to provide cold energy for liquefying the raw material natural gas in the cold box 2, and the natural gas is changed into liquid natural gas. The LNG has a low temperature before separation throttling, and after passing through the LNG throttling valve 31, since the pressure of the natural gas is changed from a high pressure to a low pressure, part of the LNG is converted into gaseous natural gas (the lower the temperature of the natural gas before throttling, the more the amount of the obtained LNG is), and at this time, the less the LNG is mixed into the LNG flowing into the gas-liquid separation device 4. The structure of the whole system is arranged, so that the amount of the gaseous natural gas which is separated by the gas-liquid separation device 4 and needs to return to the raw material compression device 1 is reduced, and the energy consumption of the whole system is reduced. And a refrigerant circulating loop 6 is added, so that the temperature of the natural gas before throttling is further reduced.

According to some embodiments of the present application, the liquid outlet of the gas-liquid separation device 4 is connected to the product collection device through the fourth pipe section 74, the gas outlet of the gas-liquid separation device 4 is connected to the second inlet 23 of the cold box 2 through the fifth pipe section 75, after the natural gas is separated by the gas-liquid separation device 4, the separated liquefied natural gas flows into the product collection device through the fourth pipe section 74 to be stored in and out, and the separated gaseous natural gas enters the cold box 2 through the fifth pipe section 75. The second inlet 23 of the cold box 2 is connected with the second outlet 24 of the cold box 2 through a sixth pipe section 76, and one second inlet 23 and one second outlet 24 correspond to one sixth pipe section 76 inside the cold box 2, and since the gaseous natural gas separated by the gas-liquid separation device 4 has a low temperature, heat exchange can be performed in the cold box 2 to provide cold energy for the cold box 2. The second outlet 24 of the cold box 2 is connected with the return air inlet of the raw material compression device 1 through the seventh pipe section 77, the gaseous natural gas flowing out of the gas outlet of the gas-liquid separation device 4 returns to the raw material compression device 1 through the fifth pipe section 75, the sixth pipe section 76 and the seventh pipe section 77, so that the gaseous natural gas can be recovered conveniently, and after the gaseous natural gas returns to the raw material compression device 1, the mixed raw material natural gas is liquefied again, so that more liquid natural gas can be further obtained.

According to some embodiments of the present application, the pre-cooling heat exchanger 5 is disposed outside the cold box 2, and a part of the second pipe segment 72 is located outside the cold box 2, as shown in fig. 1, the second pipe segment 72 exchanges heat with the refrigerant circulation loop 6 through the pre-cooling heat exchanger 5. The pre-cooling heat exchanger 5 and the refrigerant circulation loop 6 are externally connected with the cold box 2, so that the installation, maintenance and replacement of the pre-cooling heat exchanger 5 and the refrigerant circulation loop 6 are facilitated. When natural gas flows through the second pipe section 72, the natural gas is firstly precooled for the first time under the action of the cold box 2 (the temperature is changed to 0 ℃ to minus 10 ℃), the temperature of the natural gas is reduced, the low-temperature natural gas continuously flows into the precooling heat exchanger 5 for the second precooling (the temperature is changed to minus 40 ℃ to minus 50 ℃), the further-cooled natural gas continuously flows into the cold box 2 and is precooled for the third time under the action of the cold box 2 (the temperature is changed to minus 80 ℃ to minus 100 ℃), and therefore the natural gas flowing out of the first outlet 22 has lower temperature after being precooled for the third time. The arrangement of the pre-cooling heat exchanger 5 is equivalent to increase of a heat exchange process (cold exchange and temperature reduction) of natural gas, the pre-cooling heat exchanger 5 exchanges heat with the second pipe section 72, the pre-cooling effect of the cold box 2 can be reasonably utilized, and the service efficiency of the cold box 2 is improved.

According to some embodiments of the present application, as shown in fig. 2, the first pipe section 71 exchanges heat with the refrigerant circulation loop 6 through the pre-cooling heat exchanger 5, the natural gas output by the raw material compression device 1 enters the cold box 2 after being pre-cooled by the pre-cooling heat exchanger 5, and heat exchange is performed in the cold box 2 to obtain a lower temperature, so that the LNG throttle valve 31 obtains a larger amount of liquefied natural gas after being separately throttled. According to the practical situation, different positions of the precooling heat exchanger 5 are selected, so that the energy consumption of the whole system is reduced.

As shown in fig. 1, the refrigerant circulation circuit 6 is provided with a refrigerant compressor 61, a refrigerant cooler 62 and a refrigerant throttle 63, a refrigerant inlet of the refrigerant compressor 61 is connected to a refrigerant outlet of the pre-cooling heat exchanger 5 through an eighth pipe segment 64, a refrigerant inlet of the refrigerant cooler 62 is connected to a refrigerant outlet of the refrigerant compressor 61 through a ninth pipe segment 65, a refrigerant outlet of the refrigerant cooler 62 is connected to a refrigerant inlet of the pre-cooling heat exchanger 5 through a tenth pipe segment 66, and the refrigerant throttle 63 is installed on the tenth pipe segment 66 between the refrigerant cooler 62 and the pre-cooling heat exchanger 5. The cooling medium cooler 62 further includes a cooling medium inlet 621 and a cooling medium outlet 622, the cooling medium inlet 621 is connected to the cooling medium outlet 622, the cooling medium can flow from the cooling medium inlet 621 to the cooling medium outlet 622 to cool the cooling medium cooler 62, and the cooling medium inlet 621 and the cooling medium outlet 622 are respectively used for being connected to an external cooling medium. The cooling medium may be circulating water, that is, the cooling medium inlet 621 and the cooling medium outlet 622 are respectively connected to a cooling water tank (not shown) to form a water circulation loop, and a water pump is disposed in the cooling water tank, so that the cooling water circulates in the water circulation loop, thereby reducing the temperature of the refrigerant cooler 62. The cooling medium may also be air, and a fan (not shown) is disposed at the cooling medium inlet 621, and the fan is powered to blow air to the cooling medium cooler 62, so that heat of the cooling medium cooler 62 is driven by the air flowing between the cooling medium inlet 621 and the cooling medium outlet 622 to cool the cooling medium cooler 62.

The refrigerant is compressed by the refrigerant compressor 61, and then returns to the refrigerant compressor 61 through the ninth pipe segment 65, the refrigerant cooler 62, the tenth pipe segment 66 (refrigerant throttle 63), the precooling heat exchanger 5 and the eighth pipe segment 64 to form the refrigerant circulation loop 6, and the refrigerant circularly flows at the precooling heat exchanger 5 to exchange heat, so that the first pipe segment 71 or the second pipe segment 72 connected with the precooling heat exchanger 5 can obtain cold energy to precool the natural gas in the first pipe segment 71 or the second pipe segment 72. The refrigerant can be freon, propane, propylene, ammonia or other conventional refrigerants, or can be a mixed refrigerant (a mixture of propane, methane, ethylene and nitrogen), and a user can select the refrigerant according to actual conditions.

As shown in fig. 1, the gas-liquid separation device 4 includes multistage gas-liquid separators 41 arranged in series, and a liquid outlet of each stage of gas-liquid separator 41 is connected with a next stage of gas-liquid separator 41 through a transition pipe section 42 to form a multistage separation structure, so that natural gas entering the gas-liquid separation device 4 is subjected to multistage separation, and the separation efficiency and the separation precision of the system are improved; the transition pipe section 42 is provided with a transition throttle valve 43, which is matched with the LNG throttle valve 31, so that the natural gas entering each stage of the gas-liquid separator 41 is subjected to throttling treatment.

According to some embodiments of the present application, the cold box 2 is provided with a plurality of second inlets 23 and a plurality of second outlets 24, each second inlet 23 being connected to one second outlet 24 by a sixth pipe section 76; the raw material compression device 1 includes a plurality of compression cylinders 11 arranged in series, one second outlet 24 is arranged corresponding to one compression cylinder 11, and the second outlet 24 is connected to the return air port of the corresponding compression cylinder 11 through a seventh pipe segment 77. The gaseous natural gas separated by the gas-liquid separation device 4 flows into the raw material compression device 1 through the seventh pipe section 77 after passing through the cold box 2, different compression cylinders 11 are selected according to the pressure of the gaseous natural gas to be matched, and the efficacy of the compression cylinders 11 is reasonably utilized. The raw material cooler 12 is arranged on the outlet pipe section of the compression cylinder 11, so that the natural gas flowing out of the compression cylinder 11 is cooled, and the phenomenon that the energy consumption of the cold box 2 is improved due to overhigh temperature of the gas output by the raw material compression device 1 is avoided.

Note that the material cooler 12 and the refrigerant cooler 62 may be configured by water cooling or air cooling in the same principle.

Alternatively, the number of the plurality of compression cylinders 11 is one more than the number of the multistage gas-liquid separators 41 in order to better match the multistage gas-liquid separators 41. As shown in fig. 1, the gas-liquid separation device 4 includes a four-stage gas-liquid separator 41, the raw material compression device 1 includes five compression cylinders 11, the pressure of the gaseous natural gas separated by the fourth-stage gas-liquid separator 41 is the lowest along with the flow of the natural gas in the gas-liquid separation device 4, so that the gaseous natural gas separated by the fourth-stage gas-liquid separator 41 is delivered into the second-stage compression cylinders 11 (which are divided into first-stage to fifth-stage compression cylinders 11 one by one according to the flow direction of the raw material gas), the third-stage gas-liquid separator 41 is matched with the third-stage compression cylinder 11, the second-stage gas-liquid separator 41 is matched with the fourth-stage compression cylinder 11, and the first-stage gas-liquid separator 41 is. In other embodiments of the present application, the fourth stage gas-liquid separator 41 may also be matched with the first stage compression cylinder 11 according to the pressure of the gaseous natural gas separated by the fourth stage gas-liquid separator 41.

According to some embodiments of the present application, the raw material compression device 1 comprises a multistage booster compressor, which comprises a plurality of compression cylinders 11 arranged in series, the plurality of compression cylinders 11 constituting the multistage compression cylinder 11. The natural gas is pressurized in multiple stages through one multi-stage booster compressor, so that the structural compactness of the system is improved, and the installation space is saved. As shown in fig. 1, the raw material compression apparatus 1 includes a five-stage booster compressor, and the four-stage gas-liquid separator 41 of the gas-liquid separation apparatus 4 is matched with four booster compression cylinders 11 thereof.

According to some embodiments of the application, raw materials compression device 1 includes many compressors of series connection setting, and every compressor includes a compression cylinder 11, and the setting of many compressors can increase raw materials compression device 1 and gas-liquid separation device 4's matching effect, is convenient for realize the change and the maintenance to the compressor, has improved maintenance efficiency.

Alternatively, as shown in fig. 2, the raw material compression device 1 comprises a two-stage booster compressor, the two-stage booster compressor comprises a first stage booster compressor and a second stage booster compressor which are arranged in series, and an inlet of the first stage booster compressor is communicated with a gas source of the raw material natural gas. The gas-liquid separation device 4 includes a first-stage gas-liquid separator 41, and the gaseous natural gas separated by the first-stage gas-liquid separator 41 flows into the return gas inlet of the second-stage booster compressor through a seventh pipe section 77, and joins with the natural gas flowing out of the first-stage booster compressor and enters the second-stage booster compressor. According to different actual working conditions, a user can select different forms of the raw material compression device 1 and the gas-liquid separation device 4 so as to meet different use requirements of the user.

The liquefied natural gas flow of the natural gas liquefaction train 100 according to the present application is described below with reference to the accompanying drawings.

As shown in fig. 1, the raw material gas sent from the raw material gas tank enters the raw material compression device 1, and is pressurized by the raw material compression device 1 (the raw material cooler 12 cools the raw material gas to normal temperature), the natural gas becomes high-pressure normal-temperature gas, the high-pressure normal-temperature natural gas enters the cold box 2, and is pre-cooled by the cold box 2 and the pre-cooling heat exchanger 5 (the refrigerant circulation loop 6), the natural gas becomes high-pressure low-temperature natural gas (gas-liquid mixture), along with the flowing of the natural gas, the high-pressure low-temperature natural gas passes through the LNG throttle valve 31, the natural gas becomes low-pressure low-temperature liquid natural gas (doped with a small amount of gaseous natural gas), after entering the gas-liquid separation device 4, the liquid natural gas flows into the product collection device for storage, and the separated gaseous natural gas returns to the raw material, thereby further obtaining more liquefied natural gas.

The arrangement of the precooling heat exchanger 5 and the refrigerant circulation loop 6 increases the heat exchange efficiency of the natural gas in the cold box 2, so that the natural gas flowing out of the cold box 2 has lower temperature, the amount of the liquid natural gas obtained after throttling is more under the same energy consumption, and more products (liquefied natural gas) can be obtained through the gas-liquid separation device 4; in addition, the amount of the gas separated by the gas-liquid separator 4 and required to be returned to the raw material compression device 1 is small. Through the structure, the energy consumption of the system can be greatly reduced by reducing the temperature of the natural gas before separation and throttling.

It should be noted that the features of the embodiments in the present application may be combined with each other without conflict.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims (8)

1. A natural gas liquefaction system is characterized by comprising a raw material compression device, a cold box, an LNG throttle valve, a gas-liquid separation device, a precooling heat exchanger and a refrigerant circulation loop;

the outlet of the raw material compression device is connected with the first inlet of the cold box through a first pipe section, the first inlet of the cold box is connected with the first outlet of the cold box through a second pipe section, the first outlet of the cold box is connected with the inlet of the gas-liquid separation device through a third pipe section, the LNG throttling valve is arranged on the third pipe section, and the first pipe section or the second pipe section exchanges heat with the refrigerant circulation loop through the precooling heat exchanger.

2. The natural gas liquefaction system of claim 1, wherein the second tube segment exchanges heat with the refrigerant circulation loop through the pre-cooling heat exchanger, the pre-cooling heat exchanger being disposed outside the cold box.

3. The natural gas liquefaction system according to claim 1, wherein a refrigerant compressor, a refrigerant cooler, and a refrigerant throttle valve are disposed on the refrigerant circulation loop, a refrigerant inlet of the refrigerant compressor is connected to a refrigerant outlet of the precooling heat exchanger, a refrigerant inlet of the refrigerant cooler is connected to a refrigerant outlet of the refrigerant compressor, a refrigerant outlet of the refrigerant cooler is connected to a refrigerant inlet of the precooling heat exchanger through the refrigerant throttle valve, the refrigerant cooler includes a cooling medium inlet and a cooling medium outlet, and the cooling medium inlet and the cooling medium outlet are respectively used for being connected to an external cooling medium.

4. The natural gas liquefaction system of claim 1, wherein the liquid outlet of the gas-liquid separation device is connected to the product collection device by a fourth pipe segment, the gas outlet of the gas-liquid separation device is connected to the second inlet of the cold box by a fifth pipe segment, the second inlet of the cold box is connected to the second outlet of the cold box by a sixth pipe segment, and the second outlet of the cold box is connected to the return gas port of the raw material compression device by a seventh pipe segment.

5. The natural gas liquefaction system of claim 4, wherein the gas-liquid separation device comprises a plurality of stages of gas-liquid separators arranged in series, a liquid outlet of each stage of gas-liquid separator is connected with a lower stage of gas-liquid separator through a transition pipe section, and a transition throttle valve is arranged on the transition pipe section.

6. The natural gas liquefaction system according to claim 5, wherein the cold box is provided with a plurality of the second inlets and a plurality of the second outlets, the gas outlet of each stage of the gas-liquid separator is provided corresponding to one of the second inlets, the raw material compression device comprises a plurality of compression cylinders arranged in series, one of the second outlets is provided corresponding to one of the compression cylinders, the second outlet is connected to the return port of the corresponding compression cylinder through the seventh pipe section, and a raw material cooler is provided on the outlet pipe section of each compression cylinder.

7. The natural gas liquefaction system of claim 6, wherein the feed compression device comprises a multi-stage booster compressor comprising a plurality of compression cylinders arranged in series, the plurality of compression cylinders constituting a multi-stage compression cylinder.

8. The natural gas liquefaction system of claim 6, wherein the feed compression device comprises a plurality of compressors arranged in series, each compressor comprising a compression cylinder.