OPTIMIZED ARRANGEMENT OF A MID SCALE LIQUIFIED NATURAL GAS PRODUCTION UNIT

Abstract

An optimized arrangement of a modularized liquefied natural gas production unit is disclosed. The arrangement comprises a cold box integral with the refrigerant fluid closed thermodynamic refrigeration cycle module.

Claims

1. A modularized liquefied natural gas production unit comprising a natural gas main exchanger module and a refrigerant fluid closed thermodynamic refrigeration cycle module, wherein the natural gas main exchanger module comprises a natural gas main heat exchanger and a main electrical room and the refrigerant fluid closed thermodynamic refrigeration cycle module comprises refrigerant compressor suction vessel, refrigerant compressor discharge vessel, refrigerant compressor intermediate compression stage cooler and refrigerant compressor intermediate compression stage condenser, wherein the main exchanger module is installed in close proximity to a refrigerant compressor skid.

2. The modularized liquefied natural gas production unit of claim 1, wherein the main exchanger module further comprises instrumentation and electrical connections.

3. The modularized liquefied natural gas production unit of claim 1, wherein the refrigerant compressor skid is installed in close proximity to the main electrical room.

4. The modularized liquefied natural gas production unit of claim 1, wherein the refrigerant fluid closed thermodynamic refrigeration cycle module comprises a natural gas feed line and product lines.

5. The modularized liquefied natural gas production unit of claim 4, wherein the product lines comprise a liquefied natural gas line and a liquefied petroleum gas line.

6. The modularized liquefied natural gas production unit of claim 1, wherein the refrigerant fluid closed thermodynamic refrigeration cycle module comprises emergency relief installations.

7. The modularized liquefied natural gas production unit of claim 6, wherein the emergency relief installations comprise a flare drum.

8. The modularized liquefied natural gas production unit of claim 1, wherein the main exchanger module is integral with the refrigerant fluid closed thermodynamic refrigeration cycle module to form an integrated refrigeration module.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] A more complete appreciation of the disclosed embodiments of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein:

[0015] FIG. 1 illustrates a schematic of an arrangement of a liquefied natural gas production unit according to a first embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

[0016] According to one aspect, the present subject matter is directed to a modularized liquefied natural gas production unit comprising a plurality of modules, and in particular: a first module, called main exchanger module or cold box module, containing a natural gas main heat exchanger, also named cold box, a refrigerant make-up system and an electrical room, the electrical room being configured as a collector of all the electrical connections, and a second module, called the refrigerant fluid closed thermodynamic refrigeration cycle module.

[0017] In particular, the main exchanger module comprising the main electrical room, with the motor control center, is installed in close proximity to a refrigerant compressor skid.

[0018] More in particular, the refrigerant fluid closed thermodynamic refrigeration cycle module comprises all refrigerant related equipment despite cold-box and refrigerant compressor, that is refrigerant compressor suction and discharge vessels, refrigerant compressor compression stage cooler and condenser and main emergency relief installations, like a flare drum.

[0019] Furthermore, according to one aspect, the refrigerant fluid closed thermodynamic refrigeration cycle module also contains all the interface connections with the outside installation, like feed and product lines or utilities.

[0020] According to one aspect, the present subject matter is directed to a modularized liquefied natural gas production unit comprising a cold box including at least a main heat exchanger, transferring heat from natural gas and warm refrigerant to the cold refrigerant, and related vessels needed to separate cold refrigerant vapor and liquid required to allow even distribution of the refrigerant within the main heat exchanger. The cold box is arranged on a module, called main exchanger module, also containing the main electrical room. The main exchanger module is arranged next to the refrigerant fluid closed thermodynamic refrigeration cycle module to form an integrated refrigeration module.

[0021] According to a more general aspect, the subject matter disclosed herein is directed to an optimized arrangement of a liquefied natural gas production unit wherein the Cold-Box module also comprises the electrical room and the refrigerant make-up system.

[0022] Reference now will be made in detail to embodiments of the disclosure, one examples of which is illustrated in the drawing. Such example is provided by way of explanation of the disclosure, not limitation of the disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the scope or spirit of the disclosure. Reference throughout the specification to one embodiment or an embodiment or some embodiments means that the particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrase in one embodiment or in an embodiment or in some embodiments in various places throughout the specification is not necessarily referring to the same embodiment(s). Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.

[0023] When introducing elements of various embodiments, the articles a, an, the, and said are intended to mean that there are one or more of the elements. The terms comprising, including, and having are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0024] Referring now to the drawings, FIG. 1 shows a schematic of an exemplary arrangement of a modularized liquefied natural gas production unit comprising a plurality of modules, and in particular: a main exchanger module 10, a refrigerant compressor skid 20 and a refrigerant fluid closed thermodynamic refrigeration cycle module 30.

[0025] According to one embodiment, the main exchanger module 10 and the refrigerant fluid closed thermodynamic refrigeration cycle module 30 are arranged together to form an integrated refrigeration module 40.

[0026] According to the present disclosure, the refrigerant fluid closed thermodynamic refrigeration cycle module 30 contains all the interface connections with the outside installation, namely a natural gas feed line 31 and product lines, i.e. a liquefied natural gas line 32 and a liquefied petroleum gas line 33. Additionally, the refrigerant fluid closed thermodynamic refrigeration cycle module 30 also contains utilities such as a debutanizer 34 and related heat utility 341 and a flare vessel 35 and flare line 351, connecting to an outside flare (not shown).

[0027] According to an embodiment, the refrigerant fluid closed thermodynamic refrigeration cycle module 30 comprises a refrigerant compressor suction vessel 36 and a refrigerant compressor discharge vessel 37, a refrigerant compressor intermediate compression stage cooler 38 and separator 381, a refrigerant compressor final compression stage condenser 39 and main emergency relief installations, like connection lines 352 to the flare vessel 35.

[0028] According to an exemplary embodiment, the main exchanger module 10 comprises a cold box including a main heat exchanger 11, a cold gas separator 12 to separate cold refrigerant vapor 121 and liquid 122, a main electrical room 13 and a refrigerant make-up system 14 including a refrigerant make-up feed line 141 and refrigerant make-up lines 142. 143, 144, connected to cooled refrigerant lines.

[0029] According to an exemplary embodiment, the refrigerant fluid from the compressor suction vessel 36 is directed to the compressor skid 20 through a suction line 361. The refrigerant fluid is then compressed in a first compressor stage of the compressor and subsequently directed, though a line 380 to a refrigerant compressor intermediate compression stage cooler 38, wherein the heaviest fractions of the refrigerant condense. The cooled refrigerant stream is then routed to the separator 381, wherein it is separated into a liquid stream 382 and a vapor 383. The liquid stream 382 is directed to the main heat exchanger 11 of the cold box and subsequently directed via a collector line 360 to the compressor suction vessel 36.

[0030] The vapor stream 383 from the separator 381 is sent to a second compression stage of the compressor skid 20 and subsequently directed through a line 390 to the condenser 39 wherein it is cooled and wherein other fractions of the refrigerant condense. The cooled refrigerant stream is then routed to refrigerant compressor discharge vessel 37, wherein it is separated into a liquid stream and a vapor stream, the vapor stream being composed of the lightest fractions of the refrigerant. The liquid stream is directed via a liquid stream line 371 to the main heat exchanger 11 of the cold box, and subsequently to the refrigerant compressor suction vessel 36.

[0031] The vapor stream from the refrigerant compressor discharge vessel 37 is directed via a vapor stream line 372 to the cold end of the main heat exchanger 11 of the cold box, and subsequently to the refrigerant compressor suction vessel 36.

[0032] The refrigerant cycle allows to exchange heat with the natural gas in a plurality of heat exchangers at different temperatures, taking advantage of the vaporization temperature difference between the different generated refrigerant streams to optimize the natural gas liquefaction by approaching the cooling curve of the natural gas from ambient to cryogenic temperatures, minimizing energy requirements and heat exchangers size.

[0033] On the natural gas side of the liquefied natural gas production unit, the natural gas feed is routed via a natural gas feed line 31 to the main heat exchanger 11 of the cold box, to be pre-cooled in order to condense heavier than methane hydrocarbons. The pre-cooled natural gas stream is then routed via a line 120 to the separator 12, wherein it is separated into a liquid stream and a vapor stream, the liquid stream comprising heavier than methane hydrocarbons, together with a certain amount of methane. From the top of the separator 12, the vapor stream is routed via a vapor stream line 121 to the main heat exchanger 11 of the cold box, to be cooled at a temperature causing the condensation of the vapor.

[0034] The liquid stream comprising heavier than methane hydrocarbons is routed via a liquid stream line 122 to the debutanizer 34, to separate methane still present in the liquid stream, from heavier than methane hydrocarbons, in particular from butane. The debutanizer 34, being composed of a pressurized column with a boiler at its bot-tom, provides heat 341 to the liquid stream, vaporizing the lighter components of the liquid stream, mainly methane with a little amount of propane and some butane, which run through the column wherein a vapor-liquid equilibrium is established between components with different boiling points. A liquid stream from the boiler of the debutanizer 34, comprised mainly of butane, but also comprising propane and heavier than butane components, is obtained and is collected via a liquid stream line 33. A vaporized stream from the top of the debutanizer 34, mainly comprising methane, is sent via a vaporized stream line 342 to the main heat exchanger 11 of the cold box, wherein it is condensed to form, together with the condensed vapor stream routed via the vapor stream line 121, a liquefied natural gas+stream, sent via a condensed vapor stream line 110 to a liquefied natural gas stream collection unit 111, before being collected through the line 32.

[0035] From the above description of an exemplary embodiment it is evident that most of the process, instrumentation and electrical connections are shared between the main exchanger module 10, the refrigerant compressor skid 20 and the refrigerant fluid closed thermodynamic refrigeration cycle module 30 and can consequently be completed in the premises of the producer rather than on the plant installation site, allowing for saving a lot of time on site. Depending on the refrigerant system used the number and type of equipment may vary. Key element of the invention is the location of Cold-Box, main electrical room and compressor skid in relation to the residual installation. Depending on the use of other highly instrumented systems, like turboexpanders, allocation of equipment on either the main exchanger module 10 or the refrigerant fluid closed thermodynamic refrigeration cycle module 30 might be adopted.

[0036] While aspects of the invention have been described in terms of various specific embodiments, it will be apparent to those of ordinary skill in the art that many modifications, changes, and omissions are possible without departing form the spirt and scope of the claims.