RU2503900C2 - Method and device for cooling and liquefaction of hydrocarbon flow - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method for bringing into action of two or more compressors for cooling agent during hydrocarbon cooling process. In such a hydrocarbon cooling process the initial hydrocarbon flow can be passed in a counterflow with partially evaporated cooling agent flows. At least partially evaporated above cooling agent flows are compressed in cooling agent compressors. In order to obtain electric energy and hot gas, one ore more gas turbines are brought into action. Hot gas is passed through one or more steam generating heat exchangers so that water vapour energy is obtained, which is used to bring into action one or more steam turbines bringing into action at least one of the cooling agent compressors. Electric energy is used for bringing at least the other one cooling agent compressor into action.

EFFECT: higher safety.

16 cl, 4 dwg, 1 tbl

Description

FIELD OF THE INVENTION

The present invention relates to a floating base or offshore platform comprising a device for cooling and liquefying a hydrocarbon stream, and to a method for cooling and liquefying a hydrocarbon stream carried out on said floating base or offshore platform.

State of the art

A typical hydrocarbon stream to be cooled and / or liquefied includes, or mainly contains natural gas.

Various methods are known for producing liquefied natural gas (LNG). Liquefaction of a natural gas stream is desirable for a number of reasons. For example, natural gas is easier to store and transport over long distances in the form of a liquid than in a gaseous state, since it occupies a smaller volume and there is no need to store it at high pressure.

US Pat. No. 4,041,721 describes a vessel equipped with means for liquefying natural gas, which are formed by a large number of autonomous modular units for liquefaction, each of which is located in a separate compartment for liquefaction. Said liquefaction modules include units containing a compressor and a turbine drive, in which the gas turbine is in close proximity to the compressor. Therefore, a gas turbine forms an ignition source located close to hydrocarbon reserves, for example, refrigerant reserves.

Disclosure of invention

The present invention is an attempt to avoid the presence of gas turbines in the vicinity of significant hydrocarbon reserves or to at least reduce the number of gas turbines in the vicinity of hydrocarbon reserves.

The present invention provides a method for cooling and liquefying a natural gas stream on a floating base or on an offshore platform, comprising at least the following steps:

(a) passing an initial hydrocarbon stream in countercurrent with two or more refrigerant streams to produce a cooled and liquefied hydrocarbon stream and two or more at least partially vaporized refrigerant streams;

(b) compressing at least one of the at least partially vaporized hydrocarbon streams as they pass through at least one or more of the first refrigerant compressors;

(c) compressing at least one of the at least partially vaporized hydrocarbon streams while passing through at least one or more of the number of second refrigerant compressors;

(d) driving one or more gas turbines to produce:

(i) electrical energy; and (ii) hot gas;

(e) passing the hot gas of step (d) (ii) through one or more steam (steam generating) heat exchangers to produce water vapor energy;

(f) using electrical energy to drive at least one of the second refrigerant compressors; and

(g) using steam energy to drive one or more steam turbines driving at least one of the first refrigerant compressors;

the method is carried out on a floating base or offshore platform containing one or more tanks for storing liquefied petroleum hydrocarbons and / or liquefied components for refrigerants, moreover, one or more gas turbines are driven in the zone of placement of the turbine units located on or inside the floating a base or offshore platform and located away from the first and second refrigerant compressors and from one or more storage tanks.

The present invention further provides a floating base or an offshore platform comprising a device for cooling and liquefying a hydrocarbon stream located on or inside said floating base, said device comprising:

two or more cooling stages through which the initial (raw) hydrocarbon stream passes in countercurrent with two or more refrigerant streams to produce a cooled and liquefied hydrocarbon stream and two or more at least partially vaporized hydrocarbon streams;

one or more first refrigerant compressors for compressing at least one of the at least partially vaporized refrigerant streams;

one or more second refrigerant compressors for compressing at least another one of the at least partially vaporized refrigerant streams;

one or more gas turbines to produce:

(i) electrical energy for driving at least one of the second refrigerant compressors; and

(ii) hot gas;

one or more steam heat exchangers designed to produce water vapor due to the heat of the hot gas;

one or more steam turbines driven by steam energy used to drive at least one of the first refrigerant compressors;

one or more reservoirs for storing liquefied petroleum hydrocarbons and / or a component for refrigerants, wherein one or more gas turbines are driven in a turbine unit placement area located at a distance from the first and second refrigerant compressors and from one or more reservoirs for storage.

Brief Description of the Drawings

Embodiments of the present invention will now be disclosed by way of example only and with reference to the accompanying non-limiting drawings.

Figure 1 is a first diagram of the implementation of the cooling of hydrocarbons in accordance with one embodiment of the present invention.

Figure 2 is an expanded diagram of the implementation of the cooling of hydrocarbons.

Figure 3 is a more detailed diagram illustrating various embodiments of the present invention and is consistent with figure 1 and figure 2.

Figure 4 is a schematic illustration of a floating base illustrating another embodiment of the present invention.

The implementation of the invention

Figure 1 presents the General scheme 1 of the process of cooling hydrocarbons, usually including cooling the flow of hydrocarbons, for example, natural gas.

The methods and devices disclosed herein include a method and / or device for driving two or more compressors for a refrigerant in a hydrocarbon cooling process. In particular, the method comprises at least the steps of:

drive one or more gas turbines to produce:

(i) electrical energy;

(ii) hot gas;

passing heated gas through one or more steam heat exchangers to produce water vapor energy;

the use of electrical energy to drive at least one of the refrigerant compressors; and

the use of water vapor energy to drive one or more steam turbines to operate at least one other refrigerant compressor from among the available refrigerant compressors.

These steps can be carried out as part of a process for cooling and liquefying a stream of hydrocarbons in either an onshore installation or in an offshore zone on a floating base or offshore platform. However, when carrying out these stages on an offshore platform or floating base equipped with one or more tanks for storing liquefied petroleum hydrocarbons and / or a component for refrigerants, this method advantageously allows you to operate one or more gas turbines located on or inside the offshore platform or a floating base in the area where the turbine units are located, remote from the first and second refrigerant compressors and from one or more storage tanks .

This makes the process in question significantly more economical since gas turbines can now be placed outside the immediate vicinity of hydrocarbon reserves in compressors and storage tanks, for example, LNG and refrigerants.

An additional advantage of the present invention is that the amount necessary for carrying out the process can be saved.

In addition, the embodiments disclosed herein illustrate an improved method and apparatus for cooling a stream of hydrocarbons, for example, natural gas, which are characterized by greater flexibility with respect to energy requirements.

It should be noted that in patent document US 6691531 describes a system for liquefying natural gas, which uses a single first and second gas turbine (indicated in figure 1 by 700 and 702) to drive the first and second propane and ethylene compressors. Hot exhaust gases leaving gas turbines are directed to an indirect heat exchanger (802), and a steam-water stream flowing through a pipe (804) is directed to the first and second steam turbines (704, 706), which drive methane compressors. In addition to using hot exhaust gases from gas turbines, the known system also has two gas turbines located directly adjacent to propane and ethylene compressors, which poses an internal safety risk that the present invention seeks to avoid.

Gas turbines are known in the art and include aircraft engine turbines. Such gas turbines typically include a system for compressing air and operate by burning light gaseous hydrocarbons, typically one or more gases from the group consisting of methane, ethane, propane, and the like.

Steam (steam generating) heat exchangers designed to produce water vapor energy by utilizing the heat of the hot gas obtained from gas turbines are also well known in the art. They can extract the thermal energy contained in the hot gas and include any types or forms of steam generators, such as a waste heat recovery unit.

Two or more flows of step (a) of the method of the present invention may occur in separate refrigerant circuits, or they may be separate fractions or parts of a single refrigerant circuit, for example, as shown in patent document WO 96/33379 A1.

The first and second refrigerant compressors may be in separate refrigerant circuits, or they may be included in the same circuit, for example, in the aforementioned single refrigerant circuit. In the case where the first and second refrigerant compressors are included in the same circuit, it is possible that two or more of the at least partially vaporized streams pass through one or more of the same refrigerant compressors.

The present invention may include two or more cooling steps, each step having one or more steps, elements, and the like. For example, each cooling stage may include from one to five heat exchangers, for example, two or three heat exchangers. Each heat exchanger can be connected to a corresponding refrigerant compressor. Moreover, each stage at its discretion includes one or more refrigerant flows and one or more compressors for the refrigerant, at its discretion, as elements of the same or separate refrigerant circuit.

In one embodiment of the present invention, a hydrocarbon cooling process comprises the use of two or three cooling stages. The first cooling stage is preferably designed to reduce the temperature of the initial hydrocarbon stream to a temperature below 0 ° C, usually in the range from -20 ° C to -70 ° C. This cooling stage is also sometimes called the “pre-cooling” stage.

The second cooling stage is preferably separated from the first cooling stage. That is, the second cooling stage includes one or more heat exchangers using a second refrigerant circulating in the second cooling circuit, although the second refrigerant stream can also pass through one or more heat exchangers of the first cooling stage, preferably through all heat exchangers of the first cooling stage. This second cooling stage is sometimes also called the “main cooling” stage.

Preferably, at least one of the refrigerant compressors of said second stage is a cryogenic refrigerant compressor, which is more preferably driven by electric energy generated by a gas turbine (s).

Preferably, at least one of the compressors for the first stage refrigerant is a compressor for pre-cooling refrigerant, which is preferably driven by a steam turbine (s) (to which the energy is supplied with water vapor obtained from the heat of the hot gas removed from gas turbine (s)). If two or more of the first refrigerant compressors are used, preferably all of the first refrigerant compressors are pre-refrigerant compressors. Preferably, all the compressors for the first stage refrigerant are compressors for the pre-cooling refrigerant.

Thus, passing the initial hydrocarbon stream in countercurrent with two or more refrigerant streams in step (a) to produce a cooled and liquefied hydrocarbon stream and two or more at least partially vaporized refrigerant streams, preferably involves the use of the first stage cooling, where the initial hydrocarbon stream is preferably countercurrently cooled with one or more first refrigerant streams to produce a cooled hydrocarbon stream and one sludge and more at least partially vaporized streams of the first refrigerant, which are compressed by the first compressor (s) for refrigerant driven by a steam turbine (s), and the use of a second cooling stage, separated from the first cooling stage, in wherein the temperature of the cooled hydrocarbon stream is reduced by one or more second refrigerant streams, which are compressed by second electric refrigerant compressors th energy.

Even in the case of use not offshore, i.e. not on a floating base or on a floating platform, but, for example, on a coastal installation, the proposed use of compressors with an electric drive for the second cooling stage contributes to an easier and more efficient start of the process, compared to the process in which the second compressors are driven by water vapor, and the first compressors - with the help of electric energy, since it is usually necessary that the first cooling stage be activated before the second stage starts functioning cooling and receiving the steam is more easily provided using additional steam generating means (e.g., a number of steam boilers) before the completion of startup gas turbines to generate electric power.

In one embodiment of the present invention, one or more other sources of steam or electric energy, or both of these types of energy, can be provided to provide additional drive power for one or more compressors for the refrigerant, in particular for special or peak loads, or in those cases when a decrease in power occurs or the operation of one or more gas turbines or steam turbines stops for maintenance, repair, or for other purposes her. Such additional other sources provide, as far as possible, a continuous process for the cooling of hydrocarbons.

The present invention is particularly suitable when there is a limitation of the available volume (s) for carrying out the process of cooling hydrocarbons, as an independent process or as part of a larger process or installation, for example, a process comprising one or more pre-treatment processes, processes carried out after liquefaction, and / or accumulation of a stream of liquefied hydrocarbon, which requires the presence of one or more tanks for I am storing.

Thus, the present invention is, in particular, suitable for placement on a floating base, offshore platform or on a pontoon. The floating base may be any movable or permanently fixed at anchor base, usually having at least a hull, and usually representing a ship, for example, a tanker.

Such floating bases can be of any size, but usually they are elongated. Although the sea does not limit the size of the floating base, its size can be set by buildings and operational equipment located on the floating base. Thus, in one embodiment of the present invention, the floating base or offshore platform has a length of less than 600 m, preferably less than 550 m, for example, about 500 m, and has a beam (transverse beam connecting the sides of the vessel) of less than 100 m, usually 85 m, s so that it is adapted to existing ship structures and operational equipment.

The offshore platform may also be mobile, but it usually has a more permanent location than a floating base. The offshore platform may also float and may also have any suitable dimensions.

In another embodiment of the present invention, the cooling method and / or the hydrocarbon cooling process is a liquefaction process or is part of it, providing a liquefied stream of hydrocarbons, for example, liquefied natural gas. Preferably, the liquefied hydrocarbon stream is stored in one or more storage tanks, which storage tanks can also be placed on or inside any floating base or offshore platforms.

Preferably, a particular or each gas turbine is placed at a distance of at least 50 m, preferably at least 100 m, from the first and second refrigerant compressors. By locating the gas turbine (s) used in the present invention at least at a distance from the refrigerant compressors, any undesirable effects or incidents associated with this gas turbine (s) occur at least at some distance from compressors for the refrigerant, and any other relevant parts of the total composition of available funds, which usually include any apparatus, equipment, as well as a device containing hydrocarbons, for example, storage tank tank, storage tank, etc.

It is particularly desirable to maintain the distance between the gas turbine (s) and refrigerant compressors where there is a compelling need for them to be located closer to each other (for example, on a floating base or offshore platform) compared to other circumstances when not there are restrictions in terms of free space. Safe drives in the layout of floating natural gas liquefaction plants are described in an article of the same name published in the 2003 AICHe Spring National Meeting: LNC & Gas Transportation Sessions.

The present invention preferably provides a nominal productivity of a liquefied hydrocarbon stream in the range of 1 to 10 million metric tons per year (MTPA). "Nominal productivity" is determined by the daily productivity of the installation, multiplied by the number of days in a year during which the operation of the installation is provided. For example, it is envisaged that some LNG plants operate on average 345 days a year. Preferably, the nominal capacity of the hydrocarbon cooling process of the present invention is in the range of 3.5 to 7 MTPA.

The source (feed) hydrocarbon stream may be any suitable cooled, preferably liquefied, gas stream, but it is usually a natural gas stream extracted from natural gas and / or oil fields. Alternatively, the natural gas stream can also be obtained from another source, including, in addition, an artificial source, such as the Fischer-Tropsch process.

Typically, the natural gas stream contains mainly methane. Preferably, the feed stream of hydrocarbons comprises at least 50 mol% of methane, more preferably at least 80 mol% of methane.

Depending on the source used, natural gas may contain different amounts of heavier hydrocarbons than methane, for example, ethane, propane, butanes and pentanes, as well as some aromatic hydrocarbons. The composition varies depending on the type and location of natural gas production. It is necessary that hydrocarbons heavier than methane should be removed from natural gas for various reasons, for example, because they have different freezing and liquefaction temperatures, as a result of which they can block the elements of the methane liquefaction plant. As a source of liquefied natural gas, C _2-4 hydrocarbons may be used.

The natural gas stream may also contain non-hydrocarbons, such as H ₂ O, N ₂ , CO ₂ , Hg, H ₂ S and other sulfur compounds.

If desired, the hydrocarbon feed stream containing natural gas may be pre-treated before use, either as part of a cooling process or separately. This pretreatment may include reducing or removing non-hydrocarbons, such as CO ₂ , H ₂ S, or other steps, for example, initial cooling, pre-pressure boosting. Since these steps are well known to those skilled in the art, their mechanisms of action will not be further considered here.

Thus, the term "feed stream" also includes a composition prior to any treatment, for example, treatment including purification, dehydration and / or washing, as well as a composition that is partially, mainly or completely processed to reduce the content and / or removal of one or more compounds or substances, including, but not limited to, sulfur, sulfur compounds, carbon dioxide, water and C ₂₊ hydrocarbons.

Preferably, the initial hydrocarbon stream to be used in the present invention is subjected to at least the minimum pre-treatment necessary to subsequently liquefy the hydrocarbon stream. Such a necessary condition for liquefying natural gas is known in the art.

Any pre-treatment can be carried out near or near the place of implementation of the method according to the present invention, or at a distance from this place. Said removal includes shore / sea separation, or two different locations at sea.

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

The various stages, sections or stages of any part of the hydrocarbon cooling process may include the use in some way known to a person skilled in the art of the same or different types of refrigerant, and the present invention, therefore, is not limited to this.

In one embodiment of the present invention, at least one of the refrigerants, the first refrigerant or the second refrigerant, is a mixed refrigerant. Preferably, both the first refrigerant and the second refrigerant are mixed refrigerants, including, if desired, various ratios of components in the mixture and / or various compositions.

The term “refrigerant compressor” includes any unit, device or apparatus capable of increasing the pressure of a refrigerant stream. It includes refrigerant compressors in which a single process or a single compression step is carried out, or refrigerant compressors with multi-stage compressions or compression stages, in particular, multi-stage refrigerant compressors housed in a single housing or casing. The compressed refrigerant vaporized flows can be directed to the compressor at various pressures. Some stages or stages of the refrigerant compression process may include the use of two or more refrigerant compressors in series or in parallel or in series-parallel. The present invention is not limited to the type or design or arrangement of the compressor or compressors for the refrigerant, in particular in any refrigerant circuit.

It may also be desirable to compress the initial hydrocarbon stream prior to any pretreatment or before any major cooling step, or both simultaneously. Compressors other than refrigerant compressors are typically used in one or more of the pretreatment processes or steps described above.

Thus, the present invention extends to the use of electric energy or steam energy, or to the use of both types of energy obtained through the operation of one or more gas turbines, in order to operate one or more other compressors, in particular, in the case when other such compressors are part of the hydrocarbon cooling process. The hydrocarbon cooling process can extend to any treatment of the gas stream in order to cool it before passing the hydrocarbon stream in countercurrent flow with at least one of the refrigerant streams. This process includes the reduction and / or removal of non-hydrocarbons from the above, in particular, involving the use of an acid gas recovery apparatus. In addition, this process includes reducing the content or removal of hydrocarbons heavier than methane, before any main stage or stage of cooling.

In addition, one or more compressors other than refrigerant compressors can also be used in one or more stages using a chilled hydrocarbon stream, for example, to compress gas evaporating from a storage tank to compress gas discharged from containers for flash evaporation, or any other compression process produced after cooling, or secondary compression of gases such as methane, nitrogen, etc.

Thus, one or more additional compressors can compress any gas or mixture of gases not limited to methane rich gases. Such gases include nitrogen, carbon dioxide and the like.

In one embodiment of the present invention, water vapor energy is used to drive one or more, preferably> 50%, optionally of all such additional compressors. During cooling and / or liquefaction or in an appropriate installation, such additional compressors typically have different sizes and therefore consume different amounts of energy, and the water vapor energy has the advantage that it is effective regardless of the size of the compressor or consumed by the compressor energy.

1 shows a hydrocarbon feed stream 10 passing through a first cooling stage 12 using a first refrigerant stream 35 circulating in a first refrigerant circuit 35 to produce a cooled hydrocarbon stream 20.

In the scheme of FIG. 1, the first refrigerant stream 35 may be any suitable component or mixture of components, preferably comprising two or more components from the group consisting of nitrogen, methane, ethane, ethylene, propane, propylene, butane, pentane, and etc.

The first cooling stage 12 may comprise one or more heat exchangers connected in parallel, in series, or in series-in parallel through which the hydrocarbon feed stream 10 passes.

Preferably, the first cooling stage 12 cools the feed stream 10, preferably to a temperature below 0 ° C, for example, in the range of -20 ° C to -70 ° C, more preferably in the range of -20 ° C to -45 ° C or the range from -40 ° C to -70 ° C, and usually the indicated temperature depends on the type of process carried out in the first cooling stage.

At least partially, usually completely, the vaporized first refrigerant stream 35a passes from the first cooling stage 12 through one or more first refrigerant compressors 34, through one or more first environmental coolers 42a, such as water and / or air coolers, and before reuse passes through one or more expansion valves 44a.

The cooled hydrocarbon stream 20 from the first cooling stage 12 is then directed to a second cooling stage 14 using a second refrigerant stream 37, preferably the mixed refrigerant described above, circulating in the second refrigerant circuit 37.

Various schemes are possible for a cooled stream of 20 hydrocarbons and a second circuit 37 with refrigerant entering and passing through the second cooling stage 14. Such schemes are well known in the art. These may include conducting one or more stages, optionally at different pressure levels, and optionally within the same tank, for example, a primary cryogenic heat exchanger.

The second cooling stage 14 may lower the temperature of the cooled hydrocarbon stream 20 to produce a liquefied hydrocarbon stream 30, for example LNG, at a temperature of approximately equal to or less than -130 ° C.

In the simplified diagram of FIG. 1, the second refrigerant circuit 37 allows the effluent (from the second stage) of the second refrigerant vapor stream 37a to pass through one or more second refrigerant compressors 36 through one or more second environmental coolers 42b , for example, water and / or air coolers, and before its reuse (in the second stage) through one or more expansion valves 44b. Optionally, the second refrigerant stream 37 is at least partially cooled by passing it through the first cooling stage 12, as shown in FIG.

Figure 1 illustrates a method of driving the first and second refrigerant compressors 34 and 36.

In accordance with FIG. 1, there is one or more gas turbines 54 located separately from the hydrocarbon cooling process. One or more gas turbines 54 generate electrical energy using the first electric generator 56 in a manner known in the art. In addition, hot gas from one or more gas turbines 54 passes through an exhaust gas pipe 57 for subsequent passage therethrough through one or more heat exchangers 58 in order to extract heat therein in a manner known in the art. Water is supplied to the steam-generating heat exchanger 58 through a water pipe 59 to produce cold exhaust gases 61 and a steam stream 72, which has steam energy used to drive one or more steam turbines in a manner known in the art.

The energy of the steam from the steam pipe 72 enters the first steam turbine 82, which is used to directly drive the first compressor 34 for the refrigerant. For this, the steam turbine 82 is mechanically connected to the compressor 34 for the refrigerant, for example, using the shaft 85.

An advantage of the present invention is that by driving the first compressor (s) for the refrigerant using electrical energy and the second compressor (s) for the refrigerant using steam turbines using steam energy generated by the hot gas leaving gas turbines (turbines), increases the flexibility in supplying the required amount of energy to the refrigerant compressors.

Another advantage of the present invention is some saving in available volume, achieved by the fact that they no longer rely on the use of all equipment that would be powered by electric energy, and thereby provides a process or installation using the present invention, which is placed and designed more efficiently with point of view of used space.

Another advantage of the present invention is that it increases safety and reduces risk factors when carrying out the process or in an installation using the present invention in a limited space or in a limited area, for example, when located at a distance from the coast.

Steam turbine 82 may be of any suitable type. This can be, for example, a backpressure steam turbine, which usually produces (at the outlet) a low-pressure steam stream that can be used to meet thermal energy requirements anywhere else in or near the process location, in or near the installation .

However, as an alternative, a condensing steam turbine may be used. The installation’s thermal energy needs can be met, at least in part, for example, by using a low oil pressure instead of steam. The advantage of using a condensing steam turbine is that the generation of specific power in the condensing steam turbine is relatively high. Usually it can be up to two times higher than in a backpressure steam turbine. Thus, to ensure the same yield of mechanical and / or electrical energy, less water vapor is needed. This is particularly advantageous in the event of a lack of demineralized water, for example, in an offshore and / or floating process plant in which steam is generated from seawater treated with desalination equipment. Thus, a condensing steam turbine allows the use of less equipment for desalination, thereby saving volume and investment.

The need for water to produce water vapor can also be reduced by recirculating at least a portion of the water obtained from water vapor and / or water removed from the steam turbine 82 after driving said steam turbine 82.

Figure 2 presents an extended diagram 2 of the implementation of the process of cooling hydrocarbons, usually including cooling the flow of hydrocarbons, for example, natural gas.

As part of the hydrocarbon cooling process and before any major cooling of the treated stream, the initial hydrocarbon stream, including natural gas, can be pre-purified to separate at least some heavier hydrocarbons and non-hydrocarbon impurities such as carbon dioxide, water, mercury, sulfur and sulfur compounds, including, but not limited to, acid gases.

Figure 2 shows, for example, an initial hydrocarbon feed stream 5, for example, coming through a main pipeline from a well or from a wellhead in a manner known in the art. The specified feed stream is subjected to separation at the inlet in the apparatus 6, after which, at the discretion, compression in the supply compressor 13 follows. Then carry out a reduction in the content and / or removal of impurities during the passage of the initial stream through the apparatus 11 for the extraction of acid gases (AIKG) to obtain a stream 90 with a reduced content of impurities. Other streams from AIKG 11, for example, CO ₂ , can pass through line 115 for subsequent compression by means of a secondary compressor 32 to obtain, for example, a compressed stream of CO ₂ 120.

The reduced impurity stream 90 is then subjected to a natural gas condensate recovery process using one or more separation devices, typically using one or more natural gas condensate fractionation columns 26, in which a methane rich feed stream 100 is obtained. Said methane-rich feed stream 100 may be compressed by another compressor 28, if desired or necessary to increase the pressure of the hydrocarbon feed stream 10 in a subsequent cooling process. Any residual amount of methane that is recovered from the natural gas condensate stream (s) may pass through conduit 110 and may be compressed by another secondary compression compressor 33 to re-enter the main cooling process as part of the feed stream 10.

The hydrocarbon feed stream 10 thus obtained flows through a first cooling stage 12 using a first refrigerant stream 35 circulating in the first refrigerant circuit 35 described above. FIG. 2 illustrates an example of the use of two first refrigerant compressors 34a and 34b in a first refrigerant circuit 35. Other components of the primary refrigerant circuit 35 of FIG. 2 are not shown to simplify the circuit.

In one embodiment of the present invention, each heat exchanger of the multi-stage first cooling stage 12 has a different pressure of the first refrigerant. Expanded refrigerant from each pressure stage can be compressed in one or more of the first refrigerant compressors, for example, using different compressors for different refrigerant inlet pressures.

The cooled hydrocarbon stream 20 from the first cooling stage 12 is then directed to a second cooling stage 14 using a second refrigerant stream 37, preferably the mixed refrigerant described above, circulating in the second refrigerant circuit 37 described above. The second refrigerant circuit 37 allows the vaporized second refrigerant stream 37a to exit (from the heat exchanger), for example, through two second refrigerant compressors 36a and 36b, while the second refrigerant stream 37 is at least partially cooled by the first cooling stage 12.

Additional cooling of the initial hydrocarbon stream, the cooled and / or liquefied hydrocarbon stream and / or the refrigerant streams can be provided by one or more other refrigerants or refrigerant circuits in addition to cooling in the first and second cooling stages, optionally connected to another element used in the method and / or device for liquefying a hydrocarbon stream described above.

For example, the liquefied stream 30 can then be subjected to passage through the third cooling stage 16 (shown by a dashed line in the diagram), preferably subcooling, to optionally obtain the supercooled stream 40. The supercooled stream can be obtained by passing through the liquefied stream 30 one or more stages, which use one or more heat exchangers for subcooling. In this case, cooling in a particular or each subcooling heat exchanger is preferably provided by a third refrigerant compressed in another refrigerant compressor 38.

It should also be noted that one skilled in the art will understand that after liquefaction, the liquefied natural gas stream can be further processed, if necessary. As an example, the pressure of the obtained LNG can be lowered using a Joule-Thompson valve or through a cryogenic turbo expander.

For example, in Scheme 2 in FIG. 2, an additionally supercooled stream 40 is shown entering the final gas-liquid separator, for example, the final quick evaporation tank 18, to produce a methane-rich liquid stream 50 which is removed from the bottom and can be sent to the storage tank 22, and a gas stream 60 discharged from the top of the tank. Any evaporated gas 70 from the storage tank 22 may also be added to the indicated final flash tank 18. The gas stream 60 discharged from the top of the tank can be compressed using an additional compressor 24 to produce a stream 80 intended for use in a manner known in the art as a fuel stream, product stream, or elsewhere.

Scheme 2 in FIG. 2 illustrates the inclusion of not only the first refrigerant compressors 34a and 34b, and the second refrigerant compressors 36a and 36b, but also other refrigerant compressors, for example, supercooling compressor 38, and, at the discretion , other compressors are not for refrigerant, for example, those indicated above and indicated by 13, 24, 28, 32, 33.

The present invention extends to the use of any other compressors that may be included in, related to, or interconnected with a method for cooling a hydrocarbon stream, a process for cooling hydrocarbons, or any associated process involving pre-treatment and post-liquefaction processing not described herein.

Figure 3 illustrates in more detail the method of driving compressors 34, 36 for the refrigerant shown in circuits 1, 2, shown in figures 1 and 2, as well as other embodiments of the present invention.

In accordance with FIG. 3, one or more gas turbines 54 are located within the area 52 of the turbine unit, which is preferably separated from the hydrocarbon cooling process, such as that illustrated in FIG. 1 and FIG. 2. In the area 52 of the placement of the turbine unit, one or more gas turbines 54 can be installed, which are supplied with air through the air inlet 53. The air is first compressed, mixed with fuel, for example methane or other gases, including light hydrocarbons, and then burned.

One or more gas turbines 54 provide electric power using an electric generator 56 in a manner known in the art. In addition, hot gas leaving one or more gas turbines 54 passes through a flue gas line 57 (which may optionally be enriched with additional fuel (flue) gas supplied through a pipe 57a) and then passes through a steam-generating heat exchanger 58 in a manner known in the art. The water, usually at high pressure, is fed through a water line 59 to a steam-generating heat exchanger 58 to produce a cold exhaust gas 61 and a steam stream 72, usually at a high pressure, which has the energy of steam used to drive one or more steam turbines known in the art technique way.

In the circuit shown in FIG. 3, electric energy from an electric generator 56 is transmitted through an electrical power line 74 to provide electric power to one or more electric motors driving at least one or more refrigerant compressors. For example, FIG. 3 shows a power line 74 connected to a first electric motor 76 driving a second refrigerant compressor 36, for example, one or both of the second refrigerant compressors 36a, 36b shown in FIG. The electrical energy on the power line 74 can also be used to drive one or more other electric motors 78, or other electrical equipment, to drive, for example, pumps, fans and. other consumers of electric energy, especially those located at a distance or in a place designated for them or operating conditions with self-sufficiency, for example, on a floating base or offshore platform.

The energy of water vapor through the steam line 72 is supplied to at least a first steam turbine 82, which is used to drive at least one first refrigerant compressor 34, for example, the first two refrigerant compressors 34a, 34b shown in FIG. 2. Some of the energy of the water vapor through the steam line 72 can also be connected to one or more other steam turbines, shown in FIG. 3 as the second steam turbine 84, for driving one or more other compressors, for example, one or more of the indicated in FIG. 2 at 13, 24, 28, 32, 33, 38. Some of the energy of the water vapor through the steam line 72 may also be directed to one or more additional steam turbines shown in FIG. 3 as the third steam turbine 86,to drive, for example, a second electric generator 88 so as to provide additional electrical energy that can be supplied via line 89 to power line 74.

The second electric generator 88 in the claimed invention is an example of an additional source of electrical energy.

FIG. 3 also shows a steam boiler 62, in which fuel gas from the fuel pipe 64 can be used to produce an additional amount of water vapor combined with the energy of the water vapor flowing through the pipe 72.

Thus, the present invention provides the use of one or more sources of energy of water vapor and sources of electrical energy or sources of both types of energy in order to assist the existing one or more gas turbines 54.

The use of additional steam energy directed from one or more steam boilers, such as the steam boiler 62 shown in FIG. 3, also helps to start the hydrocarbon cooling process, in which, first of all, it is necessary to facilitate pre-cooling, in particular, the operation of the first refrigerant compressors 34a, 34b.

The present invention provides flexibility in the use of both electrical energy and water vapor energy in the process of cooling hydrocarbons and optionally in other inseparable or separate parts of the technological processing of the initial hydrocarbon stream and / or liquefied product stream. In this way, the dimensions, design and joint functioning of various gas turbines, steam turbines and electric generators can be used in the most efficient manner in accordance with the requirements of the hydrocarbon cooling process and additional processes, stages or steps. The present invention is not limited to power drives such as a compressor or refrigerant compressors.

Other compressors, such as those shown in FIG. 2, can be easily provided with energy by matching the requirements of typically more powerful refrigerant compressors with the output power of one or more gas turbines 54. It is generally preferable to use as much or as much of the water vapor energy as possible obtained due to the heat of the exhaust gases of one or more gas turbines 54 in order to get the maximum energy from them, which otherwise could be lost.

As a result, the present invention, in particular, is suitable when such flexibility is required in installations or when carrying out the process in a confined space, for example, on a floating base or offshore platform. For example, the floating base on which LNG is produced has a limited volume (area) for carrying out the process of cooling hydrocarbons, and an even more limited volume when additional processing is carried out, for example, the stage of production and recovery of impurities and / or heavier hydrocarbons. It is known in the art that in situations of limited volume, careful design is necessary taking into account safety precautions, and the present invention also provides increased safety due to the remote location of one or more gas turbines, with increased flexibility in the use of available energy generated one or more gas turbines.

FIG. 4 illustrates an example of a floating base 7 on which a liquefaction plant 2a is located, comprising at least a first cooling stage 12 and a second cooling stage 14, such as those discussed above. One or more gas turbines are located in the area 52 of the location of the turbine units, which is located at a distance from the place of the liquefaction process, preferably at least 50 meters or preferably at least 100 meters. The hydrocarbon feed stream 10 is cooled using the first and second cooling stages 12, 14 to obtain (directly or after further processing) a liquefied hydrocarbon stream 50, which is sent to a storage tank 22. On the floating base 7, in addition, there may be other tanks 23 for storing other components, such as propane, as a stored product, such as LNG, or for storing the components necessary for the liquefaction process, for example, the components used in the process liquefaction as a refrigerant. In addition, it is desirable to provide a distance between the area 52 of the placement of turbine units and such one or more storage tanks 22, 23.

The diagram shown in FIG. 4 illustrates another advantage of the present invention. The present invention makes it possible to increase safety requirements and reduce risk factors by separating, preferably as far as possible, within the limits of design constraints, an energy production process for carrying out a hydrocarbon cooling process, typically with one or more gas turbines, and major energy users. The indicated energy users are usually refrigerant compressors, which are usually placed close to or following their users, in particular devices or hydrocarbons (e.g. propane), which are known to have a higher risk factor than other devices or hydrocarbons. This, in particular, takes place in case of limited or insufficient volume, for example, on a floating base or on an offshore platform.

US 7114351 I1 discloses a system for liquefying natural gas in which all available equipment is powered by electric energy. In the specified document, it is noted that the system and method are effective for obtaining a sufficient amount of electrical energy used to carry out the liquefaction process.

However, the use of electric energy for all operations of the liquefaction process requires a significant number of appropriate transformers, a switching device and other electrical units and devices, all requiring a significant free volume. Thus, the system and methods known from US 7114351 are not suitable for carrying out processes and operations in a limited space. In addition, the known system is limited to the use of only such equipment, which is driven by electric energy, and does not provide the flexibility achieved through the use of equipment driven by another type of energy.

Table 1 shows comparative data on three parameters for three different energy supply systems for the hydrocarbon cooling process, for example, illustrated in FIG. The data presented in Table 1 are based on the operation of compressors for refrigerant, the same amount, type and device, used to cool the original hydrocarbon-containing gas having the same calorific value, and to produce the same amount of LNG with each system. The values shown in the table are assigned to the value “100%” for the combined system.

The “electrical” system is based on the use of raw gas cooling equipment that is fully powered by electrical energy, such as shown in patent document US 7114351 B2. The “full steam” system is based on the use of equipment that uses only the energy of water vapor. The “combined” system is based on the present invention, which uses both electrical energy and water vapor energy to drive various refrigerant compressors.

Table 1 Volume occupied by electrical equipment,% Fuel gas% Carbon dioxide% Combined one hundred one hundred one hundred Electric 130 91 91 All steam 60 133 133

Column 1 of Table 1 shows for comparison the relative volumes of volumes needed to accommodate all the electrical equipment required for the three systems being compared. As expected, the “electrical” system requires the largest volume, while the “fully steam” system requires the smallest, since generators, transformers, etc. no hardware required.

Column 2 shows for comparison the relative amounts of fuel gas required to drive the gas turbine (s) used in the three systems. If it can be seen that the fuel gas required for the electrical system is the smallest, while the fuel gas required to provide the same amount of LNG using the “fully steam” system is one third more than the “combined” system corresponding to the present invention.

The third column in Table 1 shows the amount of carbon dioxide produced by each of the systems with respect to the same amount of LNG produced. Thus, an “electrical” system produces the smallest amount of carbon dioxide, while a “fully steam” system produces the largest amount of carbon dioxide.

The data presented in Table 1 show that the present invention provides a suitable ratio between the required volume, the requirement for fuel gas and the carbon dioxide produced. These factors can be used to determine the balance between capital investments and / or production costs for the process of cooling hydrocarbons, in particular, in a plant for liquefying natural gas, and the effectiveness of such a process and / or plant, especially in places or areas with limited available volume.

One skilled in the art will understand that the present invention can be practiced in many different ways without going beyond the scope of the attached claims.

Claims (16)

1. A method of cooling and liquefying a hydrocarbon stream on a floating base or offshore platform, comprising at least the steps of:
(a) passing an initial hydrocarbon stream in countercurrent with two or more refrigerant streams to produce a cooled and liquefied hydrocarbon stream and two or more at least partially vaporized refrigerant streams;
(b) compressing at least one of the at least partially vaporized hydrocarbon streams while passing through at least one or more of the first refrigerant compressors;
(c) compressing at least one of the at least partially vaporized hydrocarbon streams while passing through at least one or more second refrigerant compressors;
(d) driving one or more gas turbines to produce:
(i) electrical energy and
(ii) hot gas;
(e) passing the hot gas of step (d) (ii) through one or more steam generating heat exchangers to produce water vapor energy;
(f) using electrical energy to drive at least one of the second refrigerant compressors; and
(g) using steam energy to drive one or more steam turbines that drive at least one of the first refrigerant compressors;
the method is carried out on a floating base or offshore platform containing one or more reservoirs for storing liquefied petroleum hydrocarbons and / or liquefied components for refrigerants, moreover, one or more gas turbines are driven in the zone of placement of turbine assemblies located on or inside the floating a base or offshore platform and away from the first and second refrigerant compressors and from one or more storage tanks. 2. The method according to claim 1, in which at least one of the second compressors for the refrigerant is a cryogenic compressor for the refrigerant. 3. The method according to claim 1, in which at least one of the first compressors for the refrigerant is a compressor for pre-cooling refrigerant. 4. The method according to claim 1, further comprising one or more additional processing steps for the initial hydrocarbon stream prior to stage (a) or the cooled hydrocarbon stream of stage (a) or both of these streams, wherein such additional processing steps include using one or more additional compressors, and electrical energy or water vapor energy or both of these types of energy drive at least one of the additional compressors. 5. The method according to claim 4, in which at least one of the additional compressors is used to compress one or more streams other than at least partially vaporized refrigerant streams of stage (b) and stage (c). 6. The method according to claim 1, further comprising one or more additional energy sources of water vapor or electrical energy. 7. The method according to claim 1, in which located at a distance means a distance of at least 50 m or preferably at least 100 m 8. The method according to claim 1, in which the nominal productivity of the liquefied hydrocarbon stream is in the range from 1 to 10 million metric tons per year, preferably in the range from 3.5 to 7 million metric tons per year. 9. The method according to claim 1, comprising the use of a first cooling stage and a second cooling stage, the flow of refrigerants for the first and second cooling stages are mixed refrigerants. 10. The method according to claim 1, in which one of the one or more steam turbines is a condensing steam turbine. 11. The method according to claim 1, in which the floating base or offshore platform has a length of less than 600 m and a width of less than 100 m 12. The method according to claim 1, in which stage (a) includes a first cooling stage, in which the initial hydrocarbon stream is pre-cooled in countercurrent with one or more flows of the first refrigerant to obtain a cooled stream of hydrocarbons and one or more partially evaporated flows of the first refrigerant, which is compressed in step (b), and the second cooling stage is separated from the first cooling stage, wherein the temperature of said cooled hydrocarbon stream is lowered with one or more the number of streams of the second refrigerant to obtain a liquefied stream of hydrocarbons and one or more at least partially evaporated streams of the second refrigerant, which are compressed in stage (c). 13. The method according to any one of claims 1 to 12, in which the hydrocarbon stream comprises or mainly contains natural gas. 14. A floating base or offshore platform comprising a device for cooling or liquefying a hydrocarbon stream on or within said floating base, said device comprising:
two or more cooling stages through which the initial hydrocarbon stream passes in countercurrent flow with two or more refrigerant streams to produce a cooled and liquefied hydrocarbon stream and two or more at least partially vaporized hydrocarbon streams;
one or more first refrigerant compressors for compressing at least one of the at least partially vaporized refrigerant streams;
one or more second refrigerant compressors for compressing at least another one of the at least partially vaporized refrigerant streams;
one or more gas turbines to produce:
(i) electrical energy for driving at least one of the second refrigerant compressors; and
(ii) hot gas;
one or more steam generating heat exchangers for generating steam energy from the hot gas;
one or more steam turbines driven by steam energy, designed to drive at least one of the first refrigerant compressors;
one or more liquefied hydrocarbon storage tanks and / or a refrigerant component;
wherein one or more gas turbines are located in the zone of the turbine units at a distance from the first and second refrigerant compressors and from one or more storage tanks. 15. The floating base or offshore platform according to 14, in which "at a distance" means a distance of at least 50 m, preferably at least 100 m 16. The floating base of claim 14 or 15, wherein one or more additional compressors are used, providing one or more additional processing steps for the hydrocarbon stream used to compress one or more streams other than at least partially evaporated refrigerant streams, where at least one of the additional compressors is driven using electrical energy or flow energy.

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