OA18582A - Natural gas liquefaction system - Google Patents

Abstract

In a natural gas liquefaction system in which an air-cooled heat exchanger group for cooling refrigerant used for cooling natural gas is disposed on a piping rack, the cost associated with refrigerant-related facilities is reduced while minimizing a decrease in the degree of freedom of installation of the liquefaction system and a reduction in efficiency of space use for the piping rack. The a natural gas liquefaction system (1) includes a piping rack (60) for supporting a raw material gas transporting pipe (Ll, L2, L10) for transporting the raw material gas; a pre-cooling heat exchanger (21) for pre-cooling the raw material gas with a first refrigerant; a first refrigerant compressor (31) for compressing the first refrigerant; a plurality of first air-cooled heat exchangers (32, 33, 35) disposed on a top of the piping; a liquefier (6) for liquefying the raw material gas which has been cooled by the precooling heat exchanger, wherein the piping rack has a widened section along a part of a length of the piping rack in a plan view, wherein the precooling heat exchanger and the first refrigerant compressor are disposed on either side of the widened section of the piping rack, and are connected to each other via a first refrigerant transporting pipe (L21, L22) extending in a direction intersecting a lengthwise direction of the piping rack for transporting the first refrigerant.

Description

NATURAL GAS LIQUEFACTION SYSTEM

TECHNICAL FIELD [0001]

The présent invention relates to a natural gas liquéfaction system for the liquéfaction of natural gas for producing liquefied natural gas by cooling natural gas.

BACKGROUND ART [0002]

Natural gas obtained from gas fields is liquefied in a liquéfaction plant so that the gas may be stored and transported in liquid form; that is, as an LNG. Cooled to around -162 degrees Celsius, the liquid natural gas advantageously has a sïgntficantly reduced volume as compared to gaseous natural gas, and is not requîred to be stored under a high pressure, Generally, a natural gas liquéfaction process involves removing impurities such as moisture, acidic gas components and mercury contained in .raw material gas (natural gas to be liquefied) in advaneeas necessary, and further involves, aller removing heavy components (cyclohexane, benzene, toluene, xylene or the like) having a relatively high freezing point in order to prevent clogging of piping, facility and the like, liquefying the raw material gas comprised primarily of methane. Methods for cooling the raw material gas include what is called Propane pre-cooled Mixed Réfrigérant Method which includes pre-cooling tlie raw material gas with propane réfrigérant, and cooling (liquefying) the gas with mixed réfrigérant (nitrogen, methane, ethane, propane and the like).

[0003]

This type ofliquefatttion-system is usually provided as a plant-witliTomparatively high throughput and requires a relatively large installation area. JP2000-180048A (Patent Document I) discloses a liquéfaction System in which raw material gas is cooled without propane pre-cooling, thereby eliminating facilities related to propane réfrigérant to minimize an installation area of the

-2liquefaction system.

PRIOR ART DOCUMENT (S)

PATENT DOCUMENT(S) [0004]

Patent Document 1: JP2000-180048A

SUMMARY OF THE INVENTION

TASK. TO BE ACCOMPLISHED BY THE INVENTION [0005]

Generally, known liquéfaction Systems as described above include a piping rack linearly arranged for supporting piping for transporting gas such as raw material gas or liquefied LNG, and raw material processing facilities disposed on either side of this piping rack where such facilities include an acid gas removing facility, a dewatering facility, a heavy component removing facility, a liquefying facility and other facilities.

[0006]

When air-cooled heat exchangers are used for cooling a réfrigérant (such as propane réfrigérant, or mixed réfrigérant) for cooling raw material gas, a group of air-cooled heat exchangers (hereinafter ”air-cooled heat exchanger group’') may be disposed on a top portion of the piping rack (at a relatively higher location) in order to prevent the air which has been used for cooling from affecting other facilities. With such a configuration, it is necessary to ensure a space for the installation of the piping rack having an area required at least for disposing an air-cooled heat exchanger group. However, an increase in the length or width of the piping rack can disadvantageously decrease the degree of freedom of installation of the liquéfaction System (that is, it becomes more difiîcult to ensure a space necessary for the installation of the piping rack). In particular, since the width of the piping rack is determined according to the size of the air-cooled heat exchanger group to be disposed, an increase in the width of the piping rack (for example, the

-3width of the piping rack is determined such that the air-cooled heat exchanger group arranged in one row in a lengthwise direction is replaced with the air-cooled heat exchanger group arrange in two rows) can cause a problem that the width of the whole piping rack becomes unnecessarily large (that is, areas on which no piping is supporled is increased), resulting in reduced effîciency of space use for the piping rack. Furthermore, increasing the length and width of the piping rack leads to increasing the length of branch pipes and connecting pipes where the branch pipes branch off from the main piping supporled by the piping rack and extend into respective facilities and the connecting pipes connect facilities arranged on both sides of the piping rack, which uneconomically increases the cost associated with refrigerant-related facilities.

[οοοη

On the other hand, as the known technology shown in the aforementioned Patent Document 1, it may also be possible to change the pre-cooling process such that some of facilities can be omitted to thereby ensure the degree of freedom of installation of the liquéfaction System. However, this approach will not improve effîciency of space use for the piping rack and can cause another problem such as an increase in the cooling-related cost caused by the use of an alternative réfrigérant.

[0008]

The présent invention has been made in view of such problems of the prior art, and a primary object of the présent invention is to provide a naturel gas liquéfaction System in which an air-cooled heat exchanger group for cooling réfrigérant used for cooling naturel gas is disposed on a piping rack, which System allows the cost associated with refrigerant-related facilities to be reduced while minimizing a decrease in the degree of freedom of installation of the liquéfaction System and a réduction in efficiency of space use for the piping rack.

MEANS TO ACCOMPLISH THE TASK [0009]

-4A first aspect of the présent invention provides a naturel gas liquéfaction system for cooling a naturel gas supplied as a raw material gas to produce a liquefied naturel gas, comprising: a piping rack for supporting a raw material gas transporting pipe for transporting the raw material gas; a pre-cooling heat exchanger for pre-cooling the raw material gas with a first réfrigérant; a first réfrigérant compressor for compressing the first réfrigérant; a plurality of first air-cooled heat exchangers disposed on a top of the piping rack for cooling the first réfrigérant compressed by the first réfrigérant compressor; and a liquéfier for liquefying the raw material gas by further cooling the raw material gas which has been cooled by the pre-cooling heat exchanger, wherein the piping rack has a widened section along a part of a length of the piping rack in a plan view, and wherein the pre-cooling heat exchanger and the first réfrigérant compressor are disposed on either side of the widened section of the piping rack, and are connected to each other via a first réfrigérant transporting pipe extending in a direction intersecting a lengthwise direction of the piping rack for transporting the first réfrigérant.

[0010]

In the naturel gas liquéfaction system according to the first aspect of the présent invention, the first air-cooled heat exchangers are disposed on the top ofthe piping rack for cooling the réfrigérant used for cooling the naturel gas, and the pre-cooling heat exchanger and the first réfrigérant compressor are disposed either side of the widened section. As a resuit, the system allows the first air-cooled heat exchangers to be collectedly arranged in a région adjacent to the pre-cooling heat exchanger and the first réfrigérant compressor (the widened section), thereby enabling réduction ofthe length ofthe first réfrigérant transporting pipe for transporting the réfrigérant between the pre-cooling heat exchanger and the first réfrigérant compressor. The system thus allows the cost associated with the first refrigerant-related facilities to be reduced while minimizing a decrease in the degree of freedom of installation of the liquéfaction system and a réduction in efficiency of space use for the piping rack compared to a system which includes a

-5piping rack having a constant width to ensure a space necessary for disposing the aîr-cooled heat exchangcrs (i.e. the piping rack has a rectangular shape having a constant length or width and does not hâve a widened section).

[0011]

According to a second aspect of the présent invention, in the system of the first aspect of the présent invention, the piping rack comprises: a first rack (61) extending in the lengthwisc direction, the first rack having a first width; and a second rack (62) extending adjacent to said first rack with a length shorter than the first rack to form the widened section, the second rack having a second width.

[0012]

In the naturel gas liquéfaction system according to the second aspect of the présent invention, the widened section is formed by the first rack which is a main rack and the second rack extending adjacent to the first rack. As a resuit, the system allows for an effective use of a space between the first and second racks and which increases the degree of freedom of arrangement of equipment and facilities in the system.

[0013]

According to a third aspect of the présent invention, in the system of the first or second aspect of the présent invention, an upstream end portion (L 1 a) of the raw material gas transporting pipe is disposed on a first side in the lengthwise direction of the piping rack, and the liquéfier is disposed on a second side opposite to the first side in the lengthwisc direction of the piping rack. [0014]

In the naturel gas liquéfaction system according to the third aspect of the présent invention, the system allows the raw material gas transporting pipe (main piping) to be disposed along the lengthwise direction of the piping rack (i.e. the system allows the raw material gas to be transported maînly in the lengthwisc direction of the piping rack), thereby minimizing an increase

-6in a space in the piping rack (or a width of the piping rack in a direction orthogonal to the lengthwise direction) required for the raw material gas transporting pipe to be disposed.

[0015]

According to a fourth aspect of the présent invention, in the system of the third aspect of the présent invention, the widened section is located on the second side in the lengthwise direction of the piping rack.

[0016]

In the natural gas liquéfaction system according to the fourth aspect of the présent invention, the system allows the pre-cooling heat exchanger, the réfrigérant compressor, and the air-cooled heat exchanger to be disposed peripherally around the liquéfier, thereby enabling réduction of the cost associated with first refrigerant-related facilities.

[0017]

According to a fifth aspect of the présent invention, in the system of any one of the first to fourth aspects of the présent invention, the system further comprises a first gas-liquid separator (37) for the first réfrigérant, wherein the first gas-liquid separator is disposed in the widened section.

[0018]

In the natural gas liquéfaction system according to the fifth aspect of the présent invention, the system allows for an effective use of a redundant space (where any raw material gas transporting pipe and other equipment are not necessarily placed) in the widened section for disposing the first gas-liquid separator, thereby effectively minimizing a réduction in efficiency of space use for the piping rack and thus enabling réduction of the entire installation area of the liquéfaction system even when the area for placement of the piping rack is increased to ensure a space necessary for the installation of the air-cooled heat exchangers.

[0019]

-7According to a sixth aspect of the présent invention, in the system of any one of the first to fifth aspects of the présent invention, the system further comprises a second réfrigérant compressor (51,53) for compressing a second réfrigérant used for cooling the raw material gas in the liquéfier; a plurality of second air-cooled heat exchangers (52, 54) disposed on the top ofthe piping rack for cooling the second réfrigérant compressed by the second réfrigérant compressor; and a réfrigérant heat exchanger (55,56, 57) for cooling the second réfrigérant with the first réfrigérant; wherein the second réfrigérant compressor and the réfrigérant heat exchanger are disposed on either side of the widened section ofthe piping rack, and are connected to each other via a second réfrigérant transporting pipe (L24, L25) extending in the direction intersecting the lengthwise direction for transporting the second réfrigérant.

[0020]

In the natural gas liquéfaction system according to the sixth aspect of the présent invention, the second réfrigérant compressor and the réfrigérant heat exchanger are disposed on either side ofthe widened section ofthe piping rack. As a resuit, the system allows the second air-cooled heat exchangers to be collectedly arranged in a région adjacent to the second réfrigérant compressor and the réfrigérant heat exchanger (the widened section), thereby enabling réduction of the length of the second réfrigérant transporting pipe for transporting the réfrigérant between the second réfrigérant compressor and the réfrigérant heat exchanger. This enables réduction of the cost associated with second refrigerant-related facilities.

[0021]

According to a seventh aspect ofthe présent invention, in the System ofthe sixth aspect of the présent invention, the second réfrigérant compressor is disposed adjacent to the first réfrigérant compressor along one side of the piping rack, and the réfrigérant heat exchanger is disposed adjacent to the pre-cooling heat exchanger along the other side of the piping rack.

[0022]

-8In the natural gas liquéfaction System according to the seventh aspect of the présent invention, the System enables the efficient connection between the réfrigérant compressors and the heat exchanges via the first and second réfrigérant transporting pipes.

[0023]

An eighth aspect of the présent invention provides a natural gas liquéfaction System for cooling a natural gas supplied as a raw material gas to produce a liquefied natural gas, comprising: a piping rack for supporting a raw material gas transporting pipe for transporting the raw material gas; a second réfrigérant compressor for compressing a second réfrigérant used for liquefying the raw material gas; a plurality of second air-cooled heat exchangers disposed on the top of the piping rack for cooling the second réfrigérant compressed by the second réfrigérant compressor; and a réfrigérant heat exchanger for cooling the second réfrigérant; wherein the second réfrigérant compressor and the réfrigérant heat exchanger are disposed on either side of the piping rack, and are connected to each other via a second réfrigérant transporting pipe extending in the direction intersecting the lengthwise direction of the piping rack for transporting the second réfrigérant. [0024]

In the natural gas liquéfaction System according to the eighth aspect of the présent invention, the réfrigérant heat exchanger is disposed on the top of the piping rack for cooling the first réfrigérant used for cooling the second réfrigérant, and the second réfrigérant compressor and the réfrigérant heat exchanger are disposed either side of the widened section. As a resuit, the system allows the second air-cooled heat exchangers to be collectedly arranged in a région adjacent to the second réfrigérant compressor and the réfrigérant heat exchanger (the widened section), thereby enabling réduction of the length of the second réfrigérant transporting pipe for transporting the réfrigérant between the second réfrigérant compressor and the réfrigérant heat exchanger. The system allows the cost associated with the second refrigerant-related facilities to be reduced while minimizing a decrease in the degrce of freedom of installation of the liquéfaction

-9system and a réduction in efficiency of space use for the piping rack compared to a system which includes a piping rack having a constant width to ensure a space necessary for disposîng the second air-cooled heat exchanger.

[0025]

According to a ninth aspect of the présent invention, in the system of the eighth aspect of the présent invention, the system further comprises a second gas-liquid separator (59) for the second réfrigérant, wherein the first gas-liquid separator is disposed in the widened section. [0026]

In the natural gas liquéfaction system according to the ninth aspect of the présent invention, the system allows for an effective use of a redundant space (where any raw material gas transporting pipe and other equipment are not necessarily placed) in the widened section for disposing the second gas-liquid separator, thereby effectively minimizing a réduction in efficiency of space use for the piping rack and thus enabling réduction of the entire installation area of the liquéfaction system even when the area for placement of the piping rack is increased to ensure a space necessary for the installation of the air-cooled heat exchangers.

EFFECT OF THE INVENTION [002η

As can be apprecîated from the foregoing, in the natural gas liquéfaction system of the présent invention in which an air-cooled heat exchanger group for cooling réfrigérant used for cooling natural gas is disposed on a piping rack, the system allows the cost associated with refrigerant-related facilities to be reduced while minimizing a decrease in the degree of freedom of installation of the liquéfaction system and a réduction in efficiency of space use for the piping rack.

BRIEF DESCRIPTION OF THE DRAWINGS [0028]

-10Figure 1 is a schematic diagram of a natural gas liquéfaction system in accordance with an embodiment of the présent invention;

Figure 2 is a diagram showing how primary facilities are located and how primary pipes are connected in the natural gas liquéfaction System of the présent invention; and

Figure 3 is a diagram schematically illustrating a structure of a piping rack used in the natural gas liquéfaction system of the présent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S) [0029]

Embodiments of the présent invention are described in the following with reference to the appended drawings.

[0030]

Figure 1 is a schematic diagram of a natural gas liquéfaction System in accordance with an embodiment of the présent invention. Figure I schematically illustrâtes respective pipes for transporting the raw material gas or other gases indicated by lines with arrows. The liquéfaction system I is composed primarily of a liquéfaction plant which cools raw material gas (natural gas to be liquefied) to produce lîquefied natural gas (LNG). The liquéfaction system 1 includes an absorption tower 2 for removing acid gases contained in the raw material gas, a régénération tower 3 for regenerating an absorbing liquid (solution) used in the absorption tower 2, a gas-liquid separator 4 for performing gas-liquid séparation to separate moisture contained in the raw material gas, moisture removers 5A to 5C for removing moisture contained in the raw material gas, and a liquéfier 6 for liquefying the raw material gas from which unnecessary components (acidic gas, heavy components, moisture, mercury or the like) hâve been removed.

[0031]

The absorption tower 2 is composed primarily of a shelf plate tower including shelves provided at regular intervals therewithin, and causes components to be removed (acid gases and

- n heavy components, in this case) to be absorbcd into the absorbing liquid by bringing the absorbing liquid into countercurrent contact with the raw material gas supplied via a raw material gas transporting pipe L1. The raw material gas from which the components to be removed hâve been removed in the absorption tower 2 is sent from the top of the tower to the gas-liquid separator 4 via a raw material gas transporting pipe L2. The absorbing liquid which has absorbed the components to be removed is sent to the régénération tower 3.

[0032]

The régénération tower 3 is provided with shelves like the absorption tower 2, and treats the absorbing liquid at certain pressure and température to thereby separate the components to be removed from the absorbing liquid. In the régénération tower 3, the absorbing liquid supplied from the absorption tower 2 drops within the tower from the upper part thereof via an absorbing liquid transporting pipe L3. Provided in a circulation pipe L4 connected to a bottom of the régénération tower 3 is a reboiler 11, which serves as a heat source of the régénération tower 3. The reboiler causes a part of the absorbing liquid discharged from the bottom of the tower 3 to be heated by heat exchange with a heat medium supplied from the outside of the reboiler 11, and then circulate in the régénération tower 3. Acidic gas components such as carbon dioxide are recovered from a discharge pipe L5 connected to the top of the régénération tower 3. Furthermore, heavy components (heavy hydrocarbons such as benzene) are recovered from a discharge pipe L6 branched from the circulation pipe L4 connected to the régénération tower 3.

[0033]

The configurations of the absorption tower 2 and the régénération tower 3 are not limited to those described above, and other known configurations can be adopted.

[0034]

The absorbing liquid from which the components to be removed hâve been séparaied in the régénération tower 3 is supplied to an upper part of the absorption tower 2 again via an

-12absorbing liquid transporting pipe L7. A heat exchanger 12 is provided between the absorbing liquid transporting pipe L3 and the absorbing liquid transporting pipe L7, and causes the absorbing liquid with a lower température flowing through the absorbing liquid transporting pipe L3 to be heated by heat exchange with the absorbing liquid with a higher température flowing through the absorbing liquid transporting pipe L7. After being cooled by the heat exchange, the absorbing liquid flowing through the absorbing liquid transporting pipe L7 is then supplied to the absorption tower 2.

[0035]

The absorbing liquid is a mixed absorbent containing a certain ratio of known chemical absorbent such as carbon dioxide, hydrogen sulfide, mercaptan, or carbonyl sulfide that absorbs acidic gas components through a chemical reaction, and a certain ratio of known physical absorbent that physîcally absorbs heavy hydrocarbons (heavy components) such as benzene, toluene and xylene contained in the raw material gas. The absorbing liquid also contains a certain ratio of water.

[0036]

After the components to be removed hâve been removed from the raw material gas in the absorption tower 2 until the concentration of the components to be removed in the gas reaches a prescribed level or less, the raw material gas is cooled by the pre-cooling heat exchanger 15 provided on the raw material gas transporting pipe L2 and then sent to the gas-lîquid separator 4. In the pre-cooling heat exchanger 15, propane réfrigérant is used to cool the raw material gas whereby moisture in the raw material gas is condensed and discharged to the outsîde from a discharge pipe L8 as a liquid phase component in the gas-liquid separator 4. The raw material gas separated as a gas phase component in the gas-liquid separator 4 is supplied to a plurality of moisture removers 5A to 5C via a raw material gas transporting pipe L9.

[003η

-13The moisture removers 5A to 5C are composed primarily of a dewatering tower filled with a known moisture absorbent which physically adsorbs moisture. In the moisture removers 5A to 5C, in order to prevent troubles caused by freezing or the like in subséquent liquéfaction processes, déhydration processing is performed until water content in the raw material gas is reduced to a prescribed ratio or less. The raw material gas from which moisture has been removed in the moisture removers 5A to 5C is cooled by propane réfrigérant in the pre-cooling heat exchanger 21 provided on a raw material gas transporting pipe L10, and then supplied to the liquéfier 6.

[0038]

In order to remove unnecessary components in the raw material gas before the raw material gas is supplied to the liquéfier 6, the liquéfaction system 1 may include not only the above-mentioned éléments but also other known facilities. For example, the system may include, between the moisture removers 5A to 5C and the liquéfier, a mercury removing facility (such as a fixed bed type adsorption tower filled with activated carbon) for removing mercury in the raw material gas and facilities (such as expander, scrubbing tower, compresser, and rectifier) for removing heavy components (e.g. component with a high freezing point such as benzene or component with a high boiling point such as C5+ hydrocarbons).

[0039]

The liquéfier 6 is a main heat exchanger which liquéfiés the raw material gas from which unnecessary components such as acid gases and heavy components hâve been removed, by heat exchange with a mixed réfrigérant. The liquéfier 6 include, but not limited to, a spool-wound type heat exchanger accommodated in a shell in which a heat transfer tube (tube bundle) for flowing a raw material gas and a mixed réfrigérant is wound like a coil, and may include any other type of heat exchanger (e.g. a plate-fin type heat exchanger) as long as it can be used at least for liquéfaction of the raw material gas. The raw material gas which has been liquefied by cooling in

-14the liquéfier 6 exhibits a low température (approximately -162 °C) and is sent to an LNG tank (not shown) for storage via an LNG transporting pipe L11. In order to facilitate the liquéfaction treatment in the liquéfier 6, the raw material gas supplied to the liquéfier 6 may be pressurized by a known compressor or the like.

[0040]

In the cooling/lïquefyïng process of the raw material gas by the liquéfaction system 1, what is called a Propane Pre-coolcd Mixed Réfrigérant Method is adopted in which a raw material gas is cooled (pre-cooled) with propane réfrigérant and then cooled (liquefîed) with a mixed réfrigérant as described above. Thus, the liquéfaction System I includes facilities fora propane pre-cooling system related to cooling by propane réfrigérant and facilities for a mixed-refrigerant system related to cooling by a mixed réfrigérant.

[0041]

In the propane pre-cooling system, propane réfrigérant (first réfrigérant) which has been compressed in a réfrigérant compressor (first réfrigérant compressor) 31 is supplied to a réfrigérant transporting pipe L21 and cooled and condensed by a plurality of air-cooled heat exchangers (first air-cooled heat exchangers) 32,33 provided on the réfrigérant transporting pipe L21, and then introduced into a réfrigérant tank 34. Thereafter, the propane réfrigérant is introduced into an air-cooled heat exchanger 35 to be further cooled and then supplied to pre-cooling heat exchangers 15 and 21 for pre-cooling the raw material gas and below-mentioned heat exchangers 55,56 and 57 for cooling the mixed réfrigérant (here, collectively referred to as a propane-refrigerant-cooling section 36) where the propane réfrigérant is used for cooling the raw material gas or cooling the mixed réfrigérant. The propane réfrigérant discharged from the cooling-by-propane-refrigerant site 36 is introduced into a gas-liquid separator (here, a knockout drum) 37 where a separated gas phase component is agaïn discharged via a réfrigérant transporting pipe L22 back to the réfrigérant compressor 31. Such circulation of the propane réfrigérant is împlemented by a plurality of pipes

-15including the above-described réfrigérant transporting pipes L21 and L22 connecting the respective éléments and equipment in the propane pre-cooling system (here, collectively referred to as a first réfrigérant circulation pipe L15). In Figure 1, the facilities or equipment ofthe propane pre-cooling system is shown independently of the other facilities or equipment for clarity purposes. [0042]

In the mixed réfrigérant system, after the mixed réfrigérant is pressurized by a first-stage réfrigérant compressor (second réfrigérant compressor) 51, the mixed réfrigérant is cooled by an air-cooled heat exchanger (second air-cooled heat exchanger) 52, and pressurized by a second-stage réfrigérant compressor (second réfrigérant compressor) 53, and then cooled by an air-cooled heat exchanger (second air-cooling type heat exchanger) 54. Thereafter, the mixed réfrigérant is supplied to via a réfrigérant transporting pipe L24 to be introduced into a sériés of cooling éléments, i.e, the réfrigérant heat exchangers 55, 56, 57 where the mixed réfrigérant is further cooled by high pressure propane réfrigérant, intermediate pressure propane réfrigérant, and low pressure propane réfrigérant, and then the mixed réfrigérant is introduced into a réfrigérant separator 58. After the mixed réfrigérant is separated into a gas phase component and a liquid phase component in the réfrigérant separator 58, the respective components are again introduced into the liquéfier 6 where they are used for cooling the raw material gas. The mixed réfrigérant discharged from the liquéfier 6 is introduced into a gas-Iiquid separator (here, a knockout drum) 59, and a gas phase component separated in the gas-Iiquid separator is retumed to the first-stage réfrigérant compressor 51 via a réfrigérant transporting pipe L25. As such, the circulation ofthe mixed réfrigérant is implemented by using a plurality of pipes including the above-described réfrigérant transporting pipes L24, L25 connecting each element and equipment (here, collectively referred to as a second réfrigérant circulation pipe L16) in the mixed réfrigérant system.

[0043]

Note that the configurations ofthe réfrigérant compressor 31, the air-cooled heat

-16exchangers 32, 33, 35 and the propane-refrigerant-cooling section 36 in the propane pre-cooling System (e.g. the type, number, arrangement of each element or equipment) may be changed as appropriate. Similarly, the configurations of the réfrigérant compressors 51 and 53, the air-cooled heat exchangers (second air-cooled heat exchangers) 52 and 54, and the réfrigérant heat exchangers 55,56, 57 and other éléments in the mixed réfrigérant System may be changed as appropriated. In FIG. 1, the pre-cooling heat exchanger 21 and the air-cooled heat exchangers 32, 33, 35,52, and 54 arc indicated as a single element denoted by a single reference numéral, respectively. However, each of the pre-cooling heat exchanger 21 and the air-cooled heat exchangers 32, 33,35,52, and 54 may be constituted by a plurality of heat exchangers. Likewise, each of the réfrigérant compressors 31,51,53 can also be constituted by a plurality of compressors.

[0044]

The mixed réfrigérant includes, but not limited to one obtained by adding nitrogen to a hydrocarbon mixture containing methane, cthane, and propane, and any other known components can be adopted as the mixed réfrigérant as long as the desired cooling effect can be achieved. Furthermore, the cooling system for cooling the raw material gas is not limited to the one described herein, and exemples of adoptable cooling Systems for cooling the raw material gas include a cascade system in which individual réfrigération cycles are formed by multiple types of réfrigérants (such as methane, cthane, and propane) having different boiling points, a DMR (Double Mixed Réfrigérant) system in which a mixed réfrigérant such as a mixture of cthane and propane is used for a pre-cooling process, a Mixed Fluid Cascade (MFC) system in which heat exchange is performed step by step using different sériés of mixed réfrigérants are used for pre-cooling, liquéfaction, and supercooling cycles, respectively, to perform heat exchange by stages, and other known Systems.

[0045]

-17Examples of the raw material gas to be treated in the liquéfaction system 1 include, but not limited to, natural gases obtained in a pressurized state from shale gas, tight sand gas, and coalbed methane. The raw material gas may be supplied to the liquéfaction system 1 not only from a gas field or other natural source via a pipe, but also from a gas storage tank or any other storage for gas. The term ”raw material gas as used herein does not mean a gas in the strict sense of the word, but refers to any substance subject to liquéfaction (including any substance to be treated during the process) in the liquéfaction system 1.

[0046]

Figure 2 is a schematic plan view showing the arrangement of primary facilities and the main pipe connections in liquéfaction System 1, and Figure 3 is a schematic side view schematically illustrating a structure of the piping rack 60 in the liquéfaction system 1. The configuration ofthe liquéfaction system 1 will be described with reference to Figure 2, in which arrows indicate the front-rear direction and the right-left direction used in the description for the sake of convenience.

[004η

As shown in FIG. 2, the liquéfaction system 1 includes the piping rack 60 for supporting piping used for transporting fluids including the raw material gas, various components separated from the raw material gas, réfrigérants (such as propane réfrigérant and mixed réfrigérant) for cooling LNG or the raw material gas. The piping rack 60 includes a main rack (first rack) 61 linearly extending in the front-rear direction (longitudinal direction) with a prescribed width W1 (e.g. about 20 m), and a frame structure (second rack) 62 linearly extending along the main rack 61 with a prescribed width W2 (e.g., about 20 m). The main rack 61 and the frame structure 62 are arranged in parallel (substantially parallel) at a prescribed séparation W3 (e.g., about 6 m).

[0048]

The main rack 61 supports main piping with relatively large diameters such as the raw

- 18material gas transporting pipes L1, L2, L10 for transporting the raw material gas and the LNG transporting pipe L11 for transporting liquefïed natural gas (LNG). As shown in FIG. 3, the main rack 61 includes a steel structure formed of a plurality of pillars 65 arranged at three points at certain intervals in the left-right direction, and a plurality of horizontal members 66 arranged at a plurality of locations in the vertical direction (which form four stages, in this case). Although

Figure 2 schematically illustrâtes the arrangement (path) of the raw material gas transporting pipes L[, L2, L10 or other pipes by lines with arrows, respectively, actual pipes are supportedby those structural members including the pillars 65 and horizontal members 66 and arranged in a more complicated manner than the arrangement shown in Figure 2.

[0049]

Although not shown in Figure 3, other structural members such as lattices, trusses, and braces are provided on the main rack 61 as necessary in the same manner as known piping racks. The number and arrangement of the pillars 65 and the horizontal members 66 are not limited to the example shown in Figure 3, and various modificationscan be made.

[0050]

An air-cooled heat exchanger group 70 for cooling réfrigérants (propane réfrigérant, and mixed réfrigérant in this case) is arranged in the entire area of the top of the main rack 61 (substantially the entire upper surface ofthe main rack 61 in this case). The air-cooled heat exchanger group 70 is composed primarily of a plurality of air-cooled heat exchangers 32,33, 35,

52, 54 arranged adjacent to each other in the front-rear direction. In the air-cooled heat exchanger group 70, headers 71, 72 for the air-cooled heat exchangers 32, 33, 35, 52, 54 are disposed on either side in the left-right direction of each piping rack, and the headers 71,72 extend along the main rack 61 in the front-rear direction. The gap between the main rack 61 and the frame structure 62 is effectively utilized as a space for arranging the headers 72 on one side of each piping rack for the air-cooled heat exchangers 32,33,35, 52, 54.

-19[0051]

The frame structure 62 is shorter than the main rack 61 in the front-rear direction and is disposed at a location along one side (a front side) of the main rack 61. The frame structure 62 has substantially the same structure as the main rack 61 except for the différence in the length in the front-rear direction. Due to the presence of this frame structure 62, the piping rack 60 has a widened section, in which the width or length in the left-right direction is widened, formed in a part of a length in the front-rear direction (in a part where the frame structure 62 is provided) of the piping rack. Like the air-cooled heat exchanger group 70 on the main rack 61, an air-cooled heat exchanger group 80 for cooling the réfrigérant including a plurality of air-cooled heat exchangers 32, 33, 35,52,54 is arranged in the entire area of the top of the frame structure 62 (substantially the entire upper surface of the frame structure 62 in this case). This configuration allows the air-cooled heat exchangers 32, 33, 35, 52, 54 to be more collcctedly arranged in the widened section of the piping rack 60 than in other parts of the length of the piping rack 60 (main rack 61) in the front-rear direction. However, ail the air-cooled heat exchangers 32, 33, 35, 52,54 are not necessarily disposed in the widened section of the piping rack 60, and in some cases, only some of the air-cooled heat exchangers 32, 33, 35,52,54 are selcctively disclosed in the widened section and other are not.

[0052]

In the présent embodiment, the frame structure 62 has substantially the same structure as the main rack 61, but the structure of the frame structure 62 is not necessarily limited thereto. Unlike the main rack 61, the frame structure 62 substantially does not support the main piping extending in the front-rear direction. As a resuit, the frame structure 62 can be made, for example, to hâve the wîdth W2 smaller than the width W1 of the main rack 61 (that is, the frame structure 62 can be made to hâve a smaller space which can support an object than the main rack 61). The séparation in the front-rear direction between two adjacent pillars 65 of the frame structure 62 may

-20be different from that of the main rack 61.

[0053]

In the présent embodiment, the piping rack 60 is constituted by the main rack 61 and the frame structure 62. In some embodiments, these éléments may be integrally formed (for example, the main rack 61 may be integrally connected to the horizontal members 66 of the frame structure 62). In the latter case, a part of the main rack 61 is widened to the left so as to extend out in conformity to the width of the frame structure 62. However, providing the main rack 61 and the frame structure 62 separately as in the présent embodiment is advantageous in that using these separate éléments încreases the degree of freedom of arrangement of equipment and facilities in the liquéfaction System I. In the présent embodiment, the width W1 ofthe main rack 61 is the same as the width W2 of the frame structure 62. However, the respective widths W 1 and W 2 are not necessarily strictly constant along ail the lengths in the front-rear direction of the main rack 61 and the frame structure 62.

[0054]

In the liquéfaction system 1, as shown in Figure 2, facilities for liquefying the raw material gas are disposed on either side of the piping rack 60 such that the piping rack 60 is located between facilities disposed on both left and right sides. More specifically, on the right side ofthe piping rack 60, a first general facility 81, an acidic gas removing facility 82, a dewatering facility 83, a cooling facility 84, and a second general facility 85 are arranged in this order from the rear end side to the front end side of the piping rack 60. On the left side of the piping rack 60, a solution régénération facility 91, an electrical facility 92, a first réfrigérant compressing facility 93, a second réfrigérant compressing facility 94, and a liquefying facility 95 are arranged in this order from the rear end side to the front end side of the piping rack 60.

[0055]

The upstream end portion (inlet portion) Lia ofthe raw material gas transporting pipe Ll

-21supported by the piping rack 60 is disposed at one end side (rear end side) of the piping rack 60, and the raw material gas is supplied to the acidic gas removing facility 82 via the raw material gas transporting pipe L1. The acidic gas removing facility 82 includes the absorption tower 2 shown in Figure 1 and other apparatuses and equipment to be used in an acidic gas removing process. The solution régénération facility 91 adjacent to the acidic gas removing facility 82 includes the régénération tower 3 shown in Figure 1 and other apparatuses and equipment to be used in the régénération tower 3 and a process of regenerating the absorbing liquid (i.e. removing acidic gas components and the like) performed in the régénération tower 3.

[0056]

The raw material gas processed by the acidic gas removing facility 82 is supplied to the dewatering facility 83 via the raw material gas transporting pipe L2. The dewatering facility 83 includes the moisture removers 5A to 5C shown in Figure 1 and other apparatuses and equipment to be used in a dewatering process performed in each moisture remover. The pre-cooling heat exchanger 15 and the gas-liquid separator 4 shown in Figure 1 may be disposed in the dewatering facility 83.

[0057]

The raw material gas processed by the dewatering facility 83 is supplied to the cooling facility 84 via the raw material gas transporting pipe L10. The cooling facility 84 is composed primarily of a pre-cooling facility 97 for cooling the raw material gas and a second réfrigérant cooling facility 98 for cooling the mixed réfrigérant. The pre-cooling facility 97 includes the pre-cooling heat exchanger 21 shown in Figure 1 along with other apparatuses and equipment used for cooling the raw material gas in the pre-cooling heat exchanger 21, the air-cooled heat exchanger 33 and the réfrigérant tank 34. The number and arrangement of the pre-cooling heat exchangers included in the pre-cooling facility 97 are not limited to those shown in the présent embodiment and various modifications can be made thereto. The pre-cooling heat exchanger 15 as

-22well as the pre-coolîng heat exchanger21 may be disposed in the pre-cooling facility 97. The second réfrigérant cooling facility 98 includes the réfrigérant heat exchangers 55, 56,57 along with other apparatuses and equipment used for cooling the mixed réfrigérant therewith. The raw material gas supplied to the cooling facility 84 is cooled to a prescribed température in the pre-cooling facility 97, and then is supplied to the liquefying facility 95 via the raw material gas transporting pipe L10.

[0058]

The cooling facility 84 is disposed on one side of the widened section (a région where the main rack 61 and the frame structure 62 extend along each other to form a portion of the piping rack widened in the left and right direction) of the piping rack 60 so as to face the first réfrigérant compressing facility 93 and the second réfrigérant compressing facility 94. In the présent embodiment, the pre-cooling facility 97 and the first réfrigérant compressing facility 93 are disposed opposite to each other on either side of the widened section of the piping rack 60, and the second réfrigérant cooling facility 98 and the second réfrigérant compressing facility 94 are disposed opposite to each other on either side of the widened section of the piping rack 60.

[0059]

The first réfrigérant compressing facility 93 includes réfrigérant compressor 31 of the propane pre-cooling system shown in Figure 1 and other apparatuses and equipment used for compressing the propane réfrigérant. The first réfrigérant compressing facility 93 is connected to the cooling facility 84 (pre-cooling facility 97) via the réfrigérant transporting pipes L21, L22 for transporting the propane réfrigérant. The réfrigérant transporting pipes L21, L22 constitute part of the first réfrigérant circulation pipe L15 shown in Figure 1 and extend in a direction intersecting a lengthwise direction (in this case, a direction substantially orthogonal to the lengthwise direction) of the piping rack 60. The propane réfrigérant supplied to the cooling facility 84 via the réfrigérant transporting pipe L21 is used for cooling the raw material gas and the mixed réfrigérant and then

-23circulated again to the first réfrigérant compressîng facility 93 via the réfrigérant transporting pipe L22.

[0060]

The gas-lîquid separator 37 shown in Figure 1 may be disposed in the widened section of the piping rack 60 (in this case, in the lower portion of the frame structure 62) as shown in Figure 3. This configuration allows for an effective use of a redundant space (where any raw material gas transporting pipe such as the raw material gas transporting pipe L1, L2 or L3 and other equipment are not necessarily placed) in the widened section for disposing the gas-liquid separator 37, thereby effectively minimizing a réduction in efficiency of space use for the piping rack 60 and thus enabling réduction of the entire installation area of the liquéfaction system 1 even when the area for placement of the piping rack 60 is increased to ensure a space necessary for the installation of the air-cooled heat exchangers.

[0061]

The second réfrigérant compressîng facility 94 includes the réfrigérant compressors 51, 53 of the mixed-refrigerant system shown in Figure 1 and other apparatuses and equipment used for compressîng the mixed réfrigérant. The second réfrigérant compressîng facility 94 is connected to the second réfrigérant cooling facility 98 via the réfrigérant transporting pipes L24, L25 for transporting the mixed réfrigérant. The réfrigérant transporting pipes L24, L25 constitute part of the second réfrigérant circulation pipe L16 shown in Figure 1 and extend in the direction intersecting the lengthwise direction (in this case, a direction substantially orthogonal to the lengthwise direction) of the piping rack 60. The mixed réfrigérant supplied to the cooling facility 84 via the réfrigérant transporting pipe L24 is cooled by the propane réfrigérant and then circulâted again to the second réfrigérant compressîng facility 94 via the réfrigérant transporting pipe L25. The mixed réfrigérant flowing through the réfrigérant transporting pipe L25 finally reaches the second réfrigérant compressîng facility 94 via the réfrigérant separator 58 and the liquéfier 6

-24shown in FIG. 1. Likc the gas-liquid separator37, the gas-liquid separator 39 shown in Figure 1 may be disposed in the widened section of the piping rack 60 as shown in Figure 3.

[0062]

As described above, unlike the main rack 61, the frame structure 62 substantially does not support the main piping extending în the front-rear direction and thus provides a redundant space (including a ground surface under the frame structure 62). In the redundant space, not only the gas-liquid separator 37,59 but also other apparatuses, equipment, containers and the like can be provided. As a resuit, the system allows for an effective use of a space in the piping rack 60. In addition, as the first réfrigérant compressing facility 93 is connected to the cooling facility 84 (pre-cooling facility 97) via the réfrigérant transporting pipes L21,122 extending in the direction intersecting the lengthwise direction of the piping rack 60, piping extending in the front-rear direction between the first réfrigérant compressing facility 93 and the cooling facility 84 becomes unnecessary (or can be reduced), thereby advantageously ensuring a space for maintenance such as maintenance of the air-cooled heat exchangers 32, 33,35, 52, 54 arranged on the upper portion of the frame structure 62 (in this case, the top of the frame structure 62). The same advantagc holds for the connection between the second réfrigérant compressing facility 94 and the second réfrigérant cooling facility 98 via the réfrigérant transporting pipes L24 and L25.

[0063]

The raw material gas which has been cooled in the cooling facility 84 is introduced into the liquefying facility 95 via the raw material gas transporting pipe L10. The liquefying facility 95 is disposed on the front end side of the piping rack 60. The liquefying facility 95 includes the liquéfier 6 shown in FIG. 1 and other apparatuses and equipment used for liquefying the raw material gas by using the liquéfier 6.

[0064]

The raw material gas (LNG) liquefied in the liquefying facility 95 is finally introduced

-25into an LNG tank or any other storage facility (not shown) via the LNG transporting pipe L11. A downstream end portion (outlet portion) 1 la ofthe LNG transporting pipe L11 is arranged on the other end side (front end side) of the piping rack 60.

[0065]

The first general facility 81 includes an acidic gas combustion facility or other facilities disposed therein, and the second general facility 85 includes a rectifying facility or other facilities disposed therein. The electrical facility 92 includes a meter room (not shown) in which a control apparatus, a power supply and instrument displays are arranged.

[0066]

Thus, in the liquéfaction system 1, the air-cooled heat exchangers 32,33,35 are disposed on the top of the piping rack 60 for cooling the propane réfrigérant, and (at least respective parts of) the pre-cooling heat exchanger 21 and the réfrigérant compressor 31 are disposed either side of the widened section. As a resuit, the system allows the air-cooled heat exchangers 32,33, 35 to be collectedly arranged in a région adjacent to the pre-cooling heat exchanger 21 and the réfrigérant compressor 31 (the widened section), thereby enabling réduction of the lengths of the réfrigérant transporting pipes L21, L22 or other pipes for transporting the propane réfrigérant between the pre-cooling heat exchanger 21 and the réfrigérant compressor 31. The system thus allows the cost associated with the propane-refrigerant-related facilities to be reduced.

[0067]

Furthermore, in the liquéfaction system 1, (at least respective parts of) the réfrigérant compressors 51,53 and the réfrigérant heat exchangers 55,56,57 are disposed on either side of the widened section of the piping rack. As a resuit, the system allows the air-cooled heat exchangers 52,54 to be collectedly arranged in a région adjacent to the réfrigérant compressors 51,53 and the réfrigérant heat exchangers 55,56,57 (the widened section), thereby enabling réduction ofthe lengths of the réfrigérant transporting pipes L24, L25 for transporting the mixed réfrigérant

-26between the réfrigérant compressors 51, 53 and the réfrigérant heat exchangers 55,56, 57. The system thus enables réduction of the cost assocîated with mixed-refrigerant-related facilities. [0068]

Morcover, in the liquéfaction system 1, the raw material gas transporting pipes (main piping) Ll, L2, Ll 0 are disposed along the lengthwise direction of the piping rack 60, the system can minimize an increase in a space in the piping rack 60 (or the width of the piping rack 60 in a direction orthogonal to the lengthwise direction) required for the raw material gas transporting pipes to be disposed.

[0069]

In the présent embodiment, the upstream side end portion Lia of the raw material gas transporting pipes Ll, L2, L10 is disposed at one end side in the lengthwise direction of the piping rack 60, while the liquéfier 6 (or the downstream end portion 1 la of the LNG transporting pipe Ll 1) is disposed on the other end side in the lengthwise direction of the piping rack 60. However, in other embodiments, the upstream side end portion Ll a of the raw material gas transporting pipes

Ll, L2, Ll0 and the liquéfier 6 (or the downstream end portion 11 a of the LNG transporting pipe Ll 1) may be disposed on the same end side (e.g. the rear end side in Figure 2) of the piping rack 60.

[0070]

In addition, in the liquéfaction system 1, the widened section is located on the front side in the lengthwise direction of the piping rack 60, and the cooling facility 84, the first and second réfrigérant compressing facilities 93,94, and the air-cooled heat exchangers 32, 33,35,52,54 are disposed peripherally around the liquefying facility95. As a resuit, the system can effectively reduce the cost assocîated with facilities related to réfrigérants (propane réfrigérant, and mixed réfrigérant).

[0071]

-27Although the présent invention has been described based on spécifie embodiments, these embodiments are merely exemplary and are not intended to limit the scope of the présent invention. For example, the main rack may support at least a main part of the raw material gas transporting pipe, and may not necessarily support the entire raw material gas transporting pipe. In some example, the raw material gas transporting pipe and the LNG transporting pipe may be partially supported by the frame structure. In alternative embodiments, the main rack and the frame structure can support neither of the raw material gas transporting pipe and the LNG transporting pipe. Although two types of réfrigérants are used in the above-described embodiments, a single réfrigérant may be used or three or more types of réfrigérants may be used. Usable réfrigérants are not limited to the propane réfrigérant and the mixed réfrigérant used in the above embodiments, and any other known réfrigérant can be used. Processing Systems in respective facilities arranged on either side of the piping rack are not limited to those in the above embodiment, and any other known system (apparatus) can be adopted. Ail the éléments of the liquéfaction System of naturel gas according to the présent invention shown in the above embodiments are not necessarily essential and can be appropriately selected as long as they do not deviate from at least the range of the présent invention.

GLOSSARY [0072] liquéfaction system absorption tower régénération tower gas-liquid sépara tor

5A, 5B, 5C moisture remover liquéfier pre-cooling heat exchanger

-2821 pre-cooling heat exchanger réfrigérant compressor (first réfrigérant compressor)

32,33,35 air-cooled heat exchanger (first air-cooled heat exchanger) gas-liquid separator

51,53 réfrigérant compressor (second réfrigérant compressor)

52,54 air-cooled heat exchanger (second air-cooled heat exchanger) * 55-57 réfrigérant heat exchanger réfrigérant separator gas-liquid separator

60 piping rack main rack (first rack) frame structure (second rack)

70, 80 air-cooled heat exchanger group acid gas removing facility

83 dewatering facility cooling facility solution régénération facility electrical facility first réfrigérant compressing facility

94 second réfrigérant compressing facility liquefying facility pre-cooling facility second réfrigérant cooling facility

L1, L2, L10 raw material gas transporting pipe

Lll LNG transporting pipe

-29L21, L22 réfrigérant transporting pipe (first réfrigérant transporting pipe)

L24, L25 réfrigérant transporting pipe (second réfrigérant transporting pipe)

Claims (6)

1. A natural gas liquéfaction system for cooling a natural gas supplied as a raw material gas to produce a liquefied natural gas, comprising:

a piping rack for supporting a raw material gas transporting pipe for transporting the raw material gas;

a pre-cooling heat exchanger for pre-cooling the raw material gas with a first réfrigérant;

a first réfrigérant compressor for compressing the first réfrigérant;

a plurality of first air-cooled heat exchangers disposed on a top of the piping rack for cooling the first réfrigérant compressed b y the first réfrigérant compressor;

a liquéfier for liquefying the raw material gas by further cooling the raw material gas which has been cooled by the pre-cooling heat exchanger;

a second réfrigérant compressor for compressing a second réfrigérant used for cooling the raw material gas in the liquéfier;

a plurality of second air-cooled heat exchangers disposed on the top of the piping rack for cooling the second réfrigérant compressed by the second réfrigérant compressor; and a réfrigérant heat exchanger for cooling the second réfrigérant with the first réfrigérant;

wherein the piping rack has a widened section along a part of a length of the piping rack in a plan view, wherein the pre-cooling heat exchanger and the first réfrigérant compressor are disposed opposite to each other on either side of the piping rack, and are connected to each other via a first réfrigérant transporting pipe extending in a direction intersecting a lengthwise direction for transporting the first réfrigérant, wherein the second réfrigérant compressor and the réfrigérant heat exchanger are disposed opposite to each other on either sides of the piping rack, and arc connected to each other

-31 via a second réfrigérant transporting pipe extending in the direction intersecting the lengthwise direction for transporting the second réfrigérant, and wherein the second réfrigérant compressor is disposed adjacent to the first réfrigérant compressor along one side of the piping rack, and the réfrigérant heat exchanger is disposed adjacent to the pre-cooling heat exchanger along the other side of the piping rack.

2. The natural gas liquéfaction system according to claim 1, wherein the piping rack comprises:

a first rack extending in the lengthwise direction, the first rack having a first width; and a second rack extending adjacent to said first rack with a length shorter than the first rack to form the widened section, the second rack having a second width.

3. The natural gas liquéfaction system according to claim 1 or 2, wherein an upstream end portion of the raw material gas transporting pipe is disposed on a first side in the lengthwise direction of the piping rack, and wherein the liquéfier is disposed on a second side opposite to the first side in the lengthwise direction of the piping rack.

4. The natural gas liquéfaction system according to claim 3, wherein the widened section is located on the second side in the lengthwise direction of the piping rack.

5. The natural gas liquéfaction system according to any one of claims 1 to 4, further comprising a second gas-liquid separator for the second réfrigérant, wherein the second gas-liquid separator is disposed in the widened section.

6. The natural gas liquéfaction system according to claim 2, wherein the plurality of first air-cooled heat exchangers comprise:

a first-stage air-cooled heat exchanger in a first stage wherein the first-stage air-cooled heat exchanger is disposed in the second rack and connected to the first réfrigérant compressor, and a second-stage air-cooled heat exchanger in a second stage wherein the second-stage air-cooled heat exchanger is disposed on the first rack and connected to the air-cooled heat exchanger of the first stage;

wherein the second réfrigérant compressor comprises a plurality of stage réfrigérant compressors, each being provided in a corresponding one of stages; and wherein the plurality of second air-cooled heat exchangers comprise:

first-stage and intermediate-stage second air-cooled heat exchangers disposed on the second rack in the first stage and intermediate stages for cooling the second réfrigérant compressed by the respective réfrigérant compressors in the first stage and intermediate stages; and a final-stage second air-cooled heat exchanger disposed on the first and second racks in a final stage for cooling the second réfrigérant compressed by the réfrigérant compressor in the final stage.

L15 raw material gas (natural gas) propane réfrigérant heavy component

54 water t propane propane propane L24 réfrigérant réfrigérant réfrigérant

36 ) t

L10 propane réfrigérant vapor

Dd

ΛΓ⁵⁸ y

rear liquefying facility dewatering facility second réfrigérant compressing facility réfrigérant compressing facility ^83

61 62

L2 general facility

gg^cooling facility^g? second réfrigérant cooling facility pre-cooling facility

-J-L21

H_22 ^82

95^

L25 <94 ^VL24

32,33,35 (52,54) acid gas removing facility general facility electrical facility solution régénération facility

32,33,35 (52,54) ^92 right -----------— left

Fig. 3

37(59)