EA030308B1 - Method and apparatus for producing a liquefied hydrocarbon stream - Google Patents

Abstract

A cryogenic hydrocarbon composition, obtained by subjecting a raw liquefied hydrocarbon stream to a pressure reduction step, is first separated into a vaporous reject stream and a liquid stream. The liquid stream is discharged in the form of the liquefied hydrocarbon stream. The vaporous reject stream is recompressed, split into first and second compressed vapour part streams. Each part stream is indirectly heat exchanged whereby the first compressed vapour part stream is indirectly heat exchanged against the first auxiliary refrigerant stream and the second compressed vapour part stream against the second auxiliary refrigerant stream. The second auxiliary refrigerant stream is formed from the condensed fraction, which is thus revaporized and subsequently combusted in a gas turbine. The vapour fraction, which generally has a higher nitrogen content and a lower heating value than the condensed fraction, is combusted in a combustion device other than a gas turbine.

Description

The invention relates to a method and apparatus for producing a stream of liquefied hydrocarbons.

Liquefied natural gas (LNG) is an economically important example of such a cryogenic hydrocarbon stream. Natural gas is a valuable source of fuel, being at the same time a source of various hydrocarbon compounds. It is often desirable for several reasons to liquefy natural gas in a natural gas liquefaction plant located at or near the source of the natural gas stream. For example, natural gas can be easily stored and transported over long distances as a liquid rather than in a gaseous form, since it will take up less volume and will not require storage at high pressure.

AO 2006/120127 describes a method and installation for separating LNG. Liquefied natural gas in liquid form is sent to a separation plant, in which an LNG-free and nitrogen-enriched steam is generated. Two columns are used in the separation plant. The LNG stream, which was liquefied in a liquefaction plant, is first separated in the first column, operating at about 1.25 bar (0.125 MPa), to form a nitrogen-depleted liquid and a head gas stream. The head gas stream is recompressed to about 4 bar (0.40 MPa) and enters the second column, where all the remaining methane is re-condensed. The recondensed methane is discharged as a liquid from the second column and mixed with the nitrogen-depleted liquid from the first column to form an LNG-free nitrogen stream. Nitrogen gas is discharged from the top of the second column, which allows the use of nitrogen contained in natural gas with technical purity.

Cooling or the indicated re-condensation of methane in the second column is carried out using a nitrogen cycle, independent of the liquefaction plant, using a liquid refrigerant, in which the nitrogen content is more than 80 mol.%.

The disadvantage of this method of separating LNG is that an independent cooling cycle is necessary, which entails both capital and operating costs. In addition, since the re-condensed methane is added to the purified LNG stream, it is becoming increasingly necessary to maintain the level of nitrogen in the purified LNG stream below the standards required for commercial LNG.

The present invention provides a method for producing a stream of liquefied hydrocarbons, including

providing a cryogenic hydrocarbon composition containing a nitrogen- and methane-containing liquid phase at an initial pressure of 1 to 2 bar abs. (0.1-0.2 MPa);

phase separation of the cryogenic hydrocarbon composition in the end separator of instant evaporation at the first separation pressure of 1 to 2 bar abs. (0.1-0.2 MPa) for vapor tail flow and liquid flow;

abstraction of the liquid stream from the end separator instantaneous evaporation in the form of a stream of liquefied hydrocarbons;

compression of the vapor tail flow in the terminal compressor of instantaneous evaporation to a pressure in excess of 2 bar abs. (0.20 MPa) resulting in a stream of compressed steam;

dividing the compressed steam into a first partial stream of compressed steam and a second partial stream of compressed steam, with the result that said first partial stream of compressed steam and a second partial stream of compressed steam have the same composition and phase as the compressed steam;

the formation of a partially condensed intermediate stream containing the condensed fraction and the vapor fraction, which includes indirect heat exchange of the first partial stream of compressed steam with the stream of the first auxiliary refrigerant as a result of heat coming from the first partial stream of compressed steam into the stream of the first auxiliary refrigerant and using indirect heat exchange of the second partial stream of compressed steam with the flow of the second auxiliary refrigerant when the heat from the second partial flow is compressed couple to the flow of the second auxiliary refrigerant and recombining the two partial flows;

separation in the gas-liquid separator of the condensed fraction from the vapor fraction of partial streams after recombination at the second separation pressure;

removal of the vapor fraction from the gas-liquid separator, and this vapor fraction has the first calorific value;

burning the vapor fraction in a combustion device other than a gas turbine; removal of the condensed fraction from the gas-liquid separator;

re-evaporation of the condensed fraction, leading to the conversion of the condensed fraction into a fully evaporated stream having a second calorific value, which is higher than the first calorific value;

combustion of the fully evaporated stream in a gas turbine;

while the re-evaporation of the condensed fraction includes the specified indirect heat exchange of the second partial stream of compressed steam by passing the condensed fraction through the reducing valve, thus forming the stream of the second auxiliary refrigerant, and subsequently exposing the specified stream of the second auxiliary refrigerant to the specified

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indirect heat exchange with the second partial flow of compressed steam, which leads to complete evaporation of the condensed fraction, and the flow of the first auxiliary refrigerant does not contain any condensed fraction.

In another aspect, the present invention provides an apparatus for producing a liquefied hydrocarbon stream comprising

supply line of cryogenic raw materials, connected to a source of a cryogenic hydrocarbon composition containing a nitrogen and methane-containing liquid phase;

an instantaneous evaporation end separator configured to receive a cryogenic hydrocarbon composition and to separate the cryogenic hydrocarbon composition into a liquid stream and a vaporous tail stream;

a liquid hydrocarbon product line that is fluidly connected to the bottom of an instantaneous evaporation end separator to discharge said liquid stream as a stream of liquefied hydrocarbons from an instantaneous evaporation end separator;

a line of tail steam, connected in fluid with the head of the end separator instantaneous evaporation for discharge of the specified vaporous tail flow from the end separator instantaneous evaporation;

an instantaneous evaporation end compressor located in the tailpipe line to compress the vapor tailpipe, resulting in a flow of compressed steam;

a flow divider provided in the compressed steam line for dividing the compressed steam line into a first branch and a second branch, the first branch being located between the flow divider and the gas-liquid separator, and the second branch being located between the stream divider and the gas-liquid separator;

the first auxiliary indirect heat exchanger located in the first branch, configured to receive the first partial stream of compressed steam present in the first branch and to establish an indirect heat exchange contact between the first partial stream of compressed steam and the stream of the first auxiliary refrigerant;

a second auxiliary indirect heat exchanger located in the second branch, configured to receive a second partial stream of compressed steam present in the second branch, and to establish an indirect heat exchange contact between the second partial stream of compressed steam and the stream of the second auxiliary refrigerant;

gas-liquid separator located downstream from the first auxiliary heat exchanger and the second auxiliary heat exchanger and configured to receive a partially condensed intermediate stream from the first auxiliary heat exchanger and the second auxiliary heat exchanger, the partially condensed intermediate stream containing a condensed fraction and a vapor fraction;

the discharge line of the vapor fraction, connected in fluid with the head part of the gas-liquid separator, made with the possibility of receiving the vapor fraction from the gas-liquid separator;

a combustion device, other than a gas turbine, which is in fluid communication with a gas-liquid separator using a vapor fraction abstraction line, for receiving and burning the vapor vapor abstracted;

the line of discharge of the condensed fraction, connected in fluid with the bottom part of the gas-liquid separator, made with the possibility of receiving the condensed fraction from the gas-liquid separator;

a gas turbine, in fluid communication with a gas-liquid separator using a condensed fraction withdrawal line, for receiving and burning the diverted condensed fraction;

a re-evaporator located in the discharge line of the condensed fraction between the gas-liquid separator and the gas turbine and configured to convert the condensed fraction into a fully evaporated stream before burning in the gas turbine;

a reducing valve located in the line of discharge of the condensed fraction between the gas-liquid separator and the re-evaporator;

moreover, the second auxiliary heat exchanger is a re-evaporator, and the condensed fraction downstream of the reducing valve is the flow of the second auxiliary refrigerant, and the stream of the first auxiliary refrigerant does not contain any condensed fraction.

Further in this document, the invention will be further illustrated with examples and with reference to the drawings, in which

in fig. 1 is a schematic representation of a process flow diagram representing a method and an installation for producing a stream of liquefied hydrocarbons according to the present invention;

in fig. 2 schematically shows an example of a pressure reduction system for use in the method and installation;

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in fig. 3 is a schematic representation of a process flow diagram representing a liquefaction plant that can be used in the methods and installations described herein;

in fig. 4 is a schematic representation of a process flow diagram representing a method and an installation in accordance with a group of embodiments of the invention;

in fig. 5 is a schematic representation of a process flow diagram representing a method and installation in accordance with another group of embodiments of the invention;

in fig. 6 is a schematic representation of a process flow diagram, where the method and installation of FIG. 1 are used with a different type of terminal evaporator.

In these figures, the same reference numbers will be used to refer to the same or similar parts. In addition, a single reference will be used to refer to the channel or line, as well as the flow transported along that line.

The present description relates to the production of a stream of liquefied hydrocarbons, such as, for example, a stream of liquefied natural gas. The cryogenic hydrocarbon composition is first divided into a vaporous tail stream and a liquid stream. The liquid stream is discharged as a stream of liquefied hydrocarbons. After the specified discharge of the liquid stream from the end separator instantaneous evaporation in the form of a stream of liquefied hydrocarbons, the stream of liquefied hydrocarbons can be transported to the cryogenic storage. Although it is not a requirement of the invention, the cryogenic storage is preferably integrated into the hull of the floating barge.

The vapor tail stream is recompressed and divided into a first partial stream of compressed steam and a second partial stream of compressed steam. The first partial stream of compressed steam and the second partial stream of compressed steam have the same composition and phase as the compressed steam. A partially condensed intermediate stream is then formed, containing the condensed fraction and vapor fraction, as a result of indirect heat exchange of the first partial stream of compressed steam with the stream of the first auxiliary refrigerant and indirect heat exchange of the second partial stream of compressed steam. After such indirect heat exchange, both partial streams undergo recombination and are separated at a second separation pressure in a gas-liquid separator, with the result that the condensed fraction is separated from the vapor fraction of the partial streams after recombination.

The condensed fraction is re-evaporated and burned in a gas turbine. This vapor stream of fuel gas is defined as high quality fuel gas stream. Repeated evaporation of the condensed fraction includes said indirect heat exchange of the second partial stream of compressed steam by passing the condensed fraction through the reducing valve, thus forming the stream of the second auxiliary refrigerant, and subsequently subjecting said stream of the second auxiliary refrigerant to the indirect heat exchange with the second partial stream of compressed steam which leads to complete evaporation of the condensed fraction, and at the same time the flow of the first auxiliary refrigerant The product does not contain any condensed fraction.

The vapor fraction, which usually has a higher nitrogen content and lower calorific value than the condensed fraction, is burned in a combustion device other than a gas turbine. In the context of the present description and in comparison with the condensed fraction, this fuel is called low quality fuel gas. Poor quality in this context means calorific value, which is lower compared to the calorific value of the high quality fuel gas vapor stream that is combusted in a gas turbine.

The advantage of dividing compressed steam into partial streams is that the cold from the condensed fraction, which turns into a fully evaporated stream with a higher calorific value for combustion in a gas turbine, can be used throughout the entire temperature range as a second auxiliary refrigerant to form a partially condensed intermediate flow. Thus, the cooling capacity required from the flow of the first auxiliary refrigerant is reduced.

A high degree of separation of methane and nitrogen in the intermediate condensed stream formed from the vapor tail stream is not required, since both the vapor fraction and the condensed fraction are burned. Thus, the vapor fraction should not be free from methane, while the condensed fraction is limited to less stringent requirements for its nitrogen content than if it were added to the stream of liquefied hydrocarbons.

The proposed method and installation, therefore, do not require a full nitrogen removal unit, since the combustible stream of fuel gas is obtained instead of the discharge stream of nitrogen.

The cryogenic hydrocarbon composition can be obtained by subjecting the crude liquefied hydrocarbon stream to a pressure reduction stage.

The cryogenic hydrocarbon composition can be obtained from the liquefaction plant. Such a liquefaction plant may contain a refrigerant circuit for circulating refrigerant flow. The refrigerant circuit may contain a refrigerant compressor connected to the drive of the refrigerant compressor and configured to compress the refrigerant flow; and cryogenic heat exchanger made with

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the possibility of establishing an indirect heat exchange contact between the hydrocarbon stream and the refrigerant stream from the refrigerant circuit, with the result that the crude liquefied stream is formed from the hydrocarbon stream containing the supercooled hydrocarbon stream. The liquefaction plant may additionally contain a pressure reduction system located downstream of the cryogenic heat exchanger and in fluid communication with it for receiving the crude liquefied stream and reducing the pressure of the crude liquefied stream. A flowline may fluidly couple a pressure reduction system to a cryogenic heat exchanger to establish a fluid communication for the crude liquefied stream to pass from the cryogenic heat exchanger to the pressure reduction system, with the flash end separator located downstream of the pressure reducing system and in communication fluid with it for receiving a cryogenic hydrocarbon composition from a pressure reduction system. Accordingly, the gas turbine, in which the condensed fraction is re-evaporated and burned, drives the refrigerant compressor out of the refrigerant circuit in the liquefaction plant. The gas turbine is preferably selected from the group consisting of gas turbines based on aircraft engines.

Accordingly, the method may suitably include circulating a refrigerant stream in a liquefaction plant, including activating a refrigerant compressor and compressing said refrigerant stream in a refrigerant compressor. The hydrocarbon stream can be condensed and supercooled, including indirect heat exchange of the specified hydrocarbon stream with the refrigerant stream in the liquefaction plant, thus forming an unrefined liquefied stream with a liquefaction pressure in excess of 2 bar abs. (0.20 MPa). The crude liquefied stream may pass through a pressure reduction stage to result in a cryogenic hydrocarbon composition containing a nitrogen- and methane-containing liquid phase. Accordingly, the refrigerant compressor is driven by said gas turbine, in which the fully evaporated condensed fraction is burned.

The flow of the first auxiliary refrigerant may preferably be formed by a small stream from a stream of liquefied hydrocarbons or a small stream of a circulating refrigerant stream from the liquefaction plant, resulting in a cryogenic hydrocarbon composition formed by condensation and supercooling of the hydrocarbon stream, including indirect heat exchange of the hydrocarbon stream with a circulating refrigerant stream in the plant liquefaction.

The proposed method and installation can preferably be used if, for example, the crude liquefied stream contains from 1 to 7 mol.% Of nitrogen. However, the greatest benefit is obtained in cases where the crude liquefied stream contains more than 3 mol.% Of nitrogen, as in cases where a vaporous tail gas is formed with a relatively high flow rate to preserve the liquid stream from which a liquefied hydrocarbon stream is produced that meets the technical requirements the ratio of the maximum content of low-boiling components, such as nitrogen, in commercially marketable liquefied natural gas. High-velocity vapor tail gas usually contains too much nitrogen to use as fuel in gas turbines, and usually goes beyond the fuel requirements for a plant’s own needs if gas turbines are used to drive refrigeration cycles in a liquefaction plant. .

More than 30 mol.% Vaporous tail stream and / or more than 30 mol.% Partially condensed intermediate stream may consist of nitrogen. This nitrogen content will be too high to meet the fuel gas requirements of most gas turbines. The proposed method and installation can be successfully used to re-condense the vapor tail gas fraction to obtain a condensed fraction that is less than 30 mol% of nitrogen, so that after re-evaporation it can be used as fuel in a gas turbine.

If the nitrogen content is still too high for the selected gas turbine, then the condensed fraction (preferably after re-evaporation) can be mixed with another fuel gas to bring the fuel in line with the technical requirements. In such cases, the invention has the advantage that the requirements for mixtures are less stringent than if the fuel gas contained more than 30 mol.% Of nitrogen.

The re-evaporated condensed fraction may be compressed to meet the specified technical requirements for gas turbine fuel gas pressure.

FIG. 1 illustrates embodiments of the invention. A cryogenic hydrocarbon composition containing a nitrogen- and methane-containing liquid phase is sent to the cryogenic feed line 8. The source of the cryogenic hydrocarbon composition is not limited to the invention in the broadest sense, but for completeness, one embodiment is illustrated in which the cryogenic hydrocarbon composition comes from a liquefaction plant 100 that converts the hydrocarbon stream 110 to a crude liquefied stream.

Such a liquefaction plant 100 is typically provided upstream of the cryogenic feed line 8. The liquefaction unit 100 may be in fluid communication with the supply line 8

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cryogenic raw materials through the system 5 pressure reduction, which communicates with the installation 100 liquefaction through branch line 1. System 5 pressure reduction is located downstream of the cryogenic heat exchanger 180 and configured to receive and reduce the pressure of the crude liquefied stream from the main cryogenic heat exchanger 5.

The pressure reduction system 5 may comprise a dynamic device, such as a turbine expander, a static device, such as a Joule-Thomson valve, or a combination thereof. An example of a pressure reduction system 5 with a Joule-Thomson valve 7 connected in series with the expander 6 is shown in FIG. 2. If a turbo-expander is used, it may optionally be driven by a generator. Many configurations are possible and known to those skilled in the art.

The instantaneous evaporation end separator 50 is adapted to receive a cryogenic hydrocarbon composition 8, optionally downstream of the pressure reduction system 5 and in fluid communication with it, if such a system is provided. Depending on the separation requirements, the end separator 50 flash evaporation can be made as a simple drum that separates the vapor from the liquid phases in a single equilibrium stage (as shown in Fig. 1), or as a more complex distillation column. Non-limiting examples of features are described in patents I8 5421165, 5893274, 6014869, 6105391 and in the publication before the grant of the patent I8 2008/0066492. A specific example will be illustrated below, with reference to FIG. 6

Line 90 of a liquid hydrocarbon product is fluidly connected to the bottom of an instantaneous evaporation end separator 50. Line 90 of a liquid hydrocarbon product connects the flash end separator 50 to a cryogenic storage 210. An optional cryogenic pump (not shown) may be present on line 90 of a liquid hydrocarbon product to facilitate the transportation of any liquid hydrocarbon product that leaves the flash end separator 50 to the cryogen storage 210. Cryogenic storage 210 is preferably embedded in the hull of a floating barge.

Line 64 of the tailpipe is fluidly coupled to the head of the instantaneous evaporation end separator 50. End compressor 260 instantaneous evaporation is located in the line 64 of the tail steam to compress the vapor tail flow from the end separator 50 instantaneous evaporation. End compressor 260 instantaneous evaporation takes the line 70 stream of compressed steam.

Flow divider 75 is provided in line 70 of compressed steam flow, by means of which line 70 of compressed steam flow is divided into first branch 71 and second branch 72. First branch 71 is configured to transfer the first partial stream of compressed steam to a gas-liquid separator 33, and second branch 72 configured to transfer the second partial stream of compressed steam to the same gas-liquid separator 33. Flow divider 75 simply divides the incoming stream 70 of compressed steam into two partial streams of the same composition and phase. The flow divider 75 may be the junction of the pipes in the form of a simple T-junction, preferably in combination with the valve 76 for adjusting the ratio of division in one of the first and second branches.

Subcooler 69 may be provided in line 70 of the compressed steam flow between end flash evaporation compressor 260 and flow divider 75. The subcooler is made with the possibility of removal of heat from the compressed steam to the environment (for example, using heat exchange with a stream of ambient air or with a stream of surrounding water). Such a subcooler is recommended in those embodiments where the temperature of the compressed steam flow when the instantaneous evaporation from the terminal compressor exceeds the temperature of the ambient air and / or surrounding water, so that at least part of the heat added to the couple in the terminal evaporator can be reset to environment.

The first auxiliary indirect heat exchanger 35 is located in the first branch 71, downstream of the end evaporation compressor 260 and the flow divider 75. The second auxiliary indirect heat exchanger 285 is located in the second branch 72. The first auxiliary indirect heat exchanger 35 may be a condenser in which the first partial stream of compressed steam is at least partially condensed.

The first auxiliary indirect heat exchanger 35 is configured to receive the first partial stream of compressed steam in the first branch 71 and to form a partially condensed intermediate stream from the first partial stream of compressed steam. The first auxiliary indirect heat exchanger 35 is configured to make an indirect heat exchange contact between at least the first partial stream of compressed steam and the stream 132 of the first auxiliary refrigerant.

The gas-liquid separator 33 is located downstream of the first auxiliary indirect heat exchanger 35 and downstream of the second auxiliary indirect heat exchanger 285. The vapor fraction discharge line 80 is fluidly connected to the head of the gas-liquid separator 33, and the condensation fraction discharge line 40 is fluidly connected with the bottom part of the gas-liquid separator 33.

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A combustion device 220, other than a gas turbine, is in fluid communication with a gas-liquid separator via a vapor fraction discharge line 80. The combustion device 220 may contain several combustion units. It may include, for example, one or more of the following devices: furnace, boiler, incinerator, dual-fuel diesel engine, or combinations thereof. The boiler and the dual-fuel diesel engine can preferably be connected to an electric generator.

The gas turbine 320 is in fluid communication with a gas-liquid separator via a condensed fraction withdrawal line 40. A second auxiliary indirect heat exchanger 285 is located in the condensed fraction withdrawal line 40, between the gas-liquid separator 33 and the gas turbine 320, to act as a re-evaporator for the condensed fraction. The second auxiliary indirect heat exchanger 285 is configured to bring the condensed fraction in the condensed fraction withdrawal line 40 into indirect heat exchange contact with the second partial flow of compressed steam in the second branch 72, with the result that during operation the heat is transferred from the second partial flow of compressed steam to the condensed fraction in line 40 diversion of the condensed fraction. Thus, the second partial stream of compressed steam is used as a coolant for the second auxiliary indirect heat exchanger 285. Reduction valve 245 is located in the condensed fraction discharge line 40 between the gas-liquid separator 33 and the second auxiliary indirect heat exchanger 285. Optionally, the fuel gas compressor 360 is placed in line 40 the discharge of the condensed fraction between the second auxiliary indirect heat exchanger 285 and the gas turbine 320.

A heat recovery heat exchanger 85 may optionally be provided in the vapor fraction discharge line 80 to recover the cold present in the vapor fraction before burning it in the combustion device 220. The heat recovery heat exchanger 85 is adapted to bring the vapor fraction in line 80 indirect heat exchange contact with the first partial stream of compressed steam, which acts as a cold recovery stream. Preferably, the optional cold recovery heat exchanger 85 is located in the first branch 71, between the flow divider 75 and the first auxiliary indirect heat exchanger 35, so that the first partial stream of compressed steam is used as a cold recovery fluid. During operation, heat is transferred from the first partial stream of compressed steam in the first branch 71 to the vapor fraction in line 80 of the vapor fraction discharge. This cold recovery heat exchanger 85 may be referred to as the first cold recovery heat exchanger in the embodiments in which a cold recovery heat exchanger 65 is provided in the line 64 of the tail steam. In such embodiments, the implementation of the heat recovery heat exchanger 65 in the line 64 of the tail steam may be referred to as the second cold recovery heat exchanger.

Such an optional cold recovery heat exchanger 65 may optionally be provided in the tail steam line 64, which causes the tail steam to be supplied to the flash end compressor 260 at the intake temperature of the end flash head evaporator that is higher than the temperature at which the tail steam is discharged from the end separator 50 instantaneous evaporation in line 64 tail pair. In this case, the cold present in the tail pair in the tail steam line 64 is retained in the cold recovery flow 66 due to heat exchange with the cold recovery flow 66 before the tail steam is compressed in the end evaporation compressor 260.

In one embodiment, the cold recovery stream 66 may comprise or consist of a side stream originating from the hydrocarbon stream 110 in the liquefaction plant 100. The resulting cooled side stream may, for example, be combined with a cryogenic hydrocarbon composition in line 8 of a supply of cryogenic feedstock. Thus, the heat exchange for cold recovery in the cold recovery heat exchanger 65 adds the rate of formation of the cryogenic hydrocarbon composition.

In another embodiment, the cold recovery stream 66 may comprise or consist of a refrigerant stream circulating in the liquefaction plant 100, with the result that the refrigerant stream (or its small stream) is condensed or supercooled. For example, a small stream of compressed refrigerant stream may be discharged from line 120 of compressed refrigerant (as shown in Fig. 3, which is described in more detail herein below) and cooled using line 64 of the tail steam.

In yet another embodiment, the cold recovery flow 66 may comprise or consist of supercooled tail steam in a compressed steam flow line 70, preferably in a portion of the compressed steam flow line 70, which continues between the subcooler 69 and the first auxiliary indirect heat exchanger 35, through which the compressed steam enters from terminal compressor 260 instantaneous evaporation to the first auxiliary indirect heat exchanger 35. At the same time, the performance required from the stream 132 of the first auxiliary refrigerant to the first m auxiliary indirect heat exchanger 35 can be reduced.

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the heat exchanger 35 from the auxiliary refrigerant supply line 132 and is discharged from the first auxiliary indirect heat exchanger 35 via the auxiliary refrigerant return line 138. The auxiliary refrigerant control valve may be located in the auxiliary refrigerant supply line 132. The preferred method of operating such an auxiliary refrigerant control valve will be explained in this document below. The auxiliary refrigerant control valve is not explicitly shown in FIG. 1, but included in FIG. 4 and 5 under the reference number 135. Auxiliary refrigerant pump may optionally be provided in the auxiliary refrigerant supply line 132. Such an auxiliary refrigerant pump is not explicitly shown in FIG. 1, but included in FIG. 4 under the reference number 96.

As can be seen in FIG. 1, the instantaneous evaporation terminal compressor 260 and the optional fuel gas compressor 360 can share a single compressor drive 290. These compressors can be implemented as two separate housings on a common drive shaft or they can actually be two compressor steps in one case.

The installation described above can be used in the method described as follows.

A cryogenic hydrocarbon composition 8 containing a nitrogen- and methane-containing liquid phase is provided at an initial pressure of 1 to 2 bar abs. (0.2-1.5 MPa) and the initial temperature. Providing a cryogenic hydrocarbon composition 8 may include passing a hydrocarbon stream 110 through a liquefaction plant 100. Hydrocarbon stream 110 may be condensed and supercooled in liquefaction plant 100. Condensation and subcooling of the hydrocarbon stream 110 preferably includes indirect heat exchange of the hydrocarbon stream 110 with a refrigerant in the liquefaction plant 100. The supercooled liquefied hydrocarbon stream thus formed is called the crude liquefied stream. Thus, the crude liquefied stream is formed from the hydrocarbon stream by condensation and subsequent supercooling of the hydrocarbon stream.

For example, in such a liquefaction unit 100, the hydrocarbon stream 110 containing the vaporous hydrocarbon-containing feedstock may be heat exchanged, for example, in a cryogenic heat exchanger, with the main refrigerant stream, thereby liquefying the vaporized feedstock from the feed stream to form a crude liquefied stream in outlet line The desired cryogenic hydrocarbon composition 8 can then be obtained from the crude liquefied stream 1. The crude liquefied stream can be diverted to flow line 1 from the installation. vki 100 liquefaction. The cryogenic hydrocarbon composition 8 can be obtained from the crude liquefied stream, for example, by passing the crude liquefied stream through a pressure reduction stage in the pressure reduction system 5. At this stage of pressure reduction, the pressure can be reduced from liquefaction pressure to initial pressure.

The cryogenic hydrocarbon composition 8 is subsequently subjected to phase separation into vapor tail 64 and liquid stream 90 at a first separation pressure of 1 to 2 bar abs. (0.1-0.2 MPa). Accordingly, this phase separation is carried out in the terminal separator 50 flash evaporation. The vaporous tail stream 64 contains most, preferably the entire volume of any vaporized vapor that was formed during the pressure reduction stage. Liquid stream 90 is discharged as a stream of liquefied hydrocarbons, which can be a stream of liquefied natural gas, provided that the methane content is at least 81 mol.%. Liquid stream 90 is typically transferred to cryogenic storage 210.

The vaporous tail stream 64 is removed from the end separator 50 instantaneous evaporation and subsequently compressed in the end compressor 260 instantaneous evaporation to a pressure in excess of 2 bar abs. (0.20 MPa) with the resulting stream 70 of compressed steam. Stream 70 of compressed steam is divided into a first partial stream 71 of compressed steam and a second partial stream 72 of compressed steam. The first partial stream of compressed steam is withdrawn from flow divider 75 and transferred to the gas-liquid separator 33 via the first branch 71, while the second partial stream of compressed steam is withdrawn from the flow divider 75 and transferred to the gas-liquid separator 33 via the second branch 72. The first partial flow of compressed vapor and The second partial stream of compressed steam has the same composition and phase as the compressed steam 70.

If sub-cooler 69 is provided in line 70 of a stream of compressed steam, stream 70 of compressed steam passes through sub-cooler 69 on the way to flow divider 75. In subcooler 69, heat is removed from the compressed vapor to the environment (for example, by heat exchange with ambient air flow or ambient water flow). Compressed steam 70 is removed from the optional sub-cooler 69 at a supercooling temperature that is close to the ambient temperature, for example, 2 ° C above the ambient temperature. The ambient temperature is considered to be the ambient temperature (air or water) into which heat is removed.

A portion of the compressed vapor stream 70, from which heat enters the first auxiliary refrigerant stream 132, is formed by the first partial stream of compressed vapor. However, before the heat from the first partial stream of compressed steam enters the stream 132 of the first auxiliary refrigerant, the first partial stream of compressed steam may optionally be subjected to indirect heat exchange with steam

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fraction 80 of the gas-liquid separator 33 in the heat recovery exchanger 85 cold. After this heat exchange, the steam fraction 80 becomes warmer than between gas-liquid separator 33 and cold recovery heat exchanger 85. Thereafter, it can be incinerated in the incinerator 220, as explained herein above.

The portion of the compressed vapor stream that undergoes indirect heat exchange in the second auxiliary indirect heat exchanger 285 with condensed fraction 40 is formed by a second partial stream of compressed steam. Thus, the partially condensed intermediate stream, which is fed into the gas-liquid separator 33, is formed by combining the first and second compressed partial streams. The partially condensed intermediate stream contains a condensed fraction 40 and a vapor fraction 80.

The division of the compressed steam is preferably carried out with an adjustable ratio of division. The division ratio corresponds to the mass flow ratio in the second branch 71 and the line 70 of compressed steam. The ratio of fission can be corrected in accordance with the temperature signal characterizing the temperature of the vapor fraction 80 from gas-liquid separator 33, which is removed from the heat recovery exchanger 85 of cold before burning. This temperature is preferably maintained at a predetermined target value by regulating the division ratio, and thus a certain degree of cold recovery from the vapor fraction 80 can be achieved regardless of changes in the rate of flow of the vapor fraction 80. The arrival rate of the first partial stream of compressed steam that functions as a fluid environment for recovery of cold, effectively adapts to the existing rate of receipt of the vapor fraction 80. For this, the second temperature sensor 77 can be provided in the steam fraction line 80 between the cold recovery heat exchanger 85 and the combustion device 220, which is electronically connected to the division ratio control valve 76, so that the setting of the division ratio control valve 76 is controlled by a signal characterizing the temperature generated in the second temperature sensor 77 The second setpoint of the target temperature for a given control loop can be set a few degrees lower, for example, 2 ° C lower, the temperature of the recovery fluid 86 is x Lod at the inlet of the heat exchanger 85 recovery of cold. If the temperature of the vapor fraction 80 at the exit from the heat recovery heat exchanger 85 is still lower than the second target temperature, the division ratio can be corrected to increase (for example, by reducing the flow opening in the division ratio control valve 76). Additional control strategies known to the person skilled in the art can be implemented to avoid limiting the operation of the heat recovery heat exchanger 85 cold when it is controlled by the outlet temperature.

Preferably, the temperature of the vapor fraction 80 at the exit from the heat recovery heat exchanger 85 is between ambient temperature and a temperature that is no more than 10 ° C below the ambient temperature in order to achieve the greatest cold recovery from the vapor fraction 80.

The partially condensed intermediate stream is formed from the first partial stream 71 of the compressed vapor and the second partial stream 72 of the compressed vapor. This includes the indirect heat exchange of the first partial flow 71 of compressed steam with the flow 132 of the first auxiliary refrigerant and the indirect heat exchange of the second partial flow of compressed steam with the flow of the second auxiliary refrigerant and the subsequent recombination of both partial streams. The flow of the second auxiliary refrigerant is formed from the condensed fraction 40 by passing the condensed fraction 40 through the reducing valve 245. During indirect heat exchange, heat flows from the first partial stream 71 of compressed steam to the stream 132 of the first auxiliary refrigerant and from the second partial stream 72 of compressed steam to the stream of the second auxiliary refrigerant. In particular, the heat exchange of the first partial stream 71 of compressed vapor with the stream 132 of the first auxiliary refrigerant leads to a partial condensation of the first partial stream of compressed vapor.

The condensed fraction 40 is then separated from the vapor fraction 80 in the gas-liquid separator 33 at the second separation pressure. Preferably, the vapor fraction and the condensed fraction coexist in the gas-liquid separator 33 and are separated in the same thermodynamic equilibrium state into said vapor fraction and the condensed fraction inside the gas-liquid separator 33. This can usually be achieved if the gas-liquid separator 33 is designed as a simple drum without any either an internal snap for a gas-liquid contact, such as a plate or nozzle, thereby essentially representing a single theoretical stage.

The vapor fraction 80 is discharged from the gas-liquid separator 33, usually as a vapor phase at its dew point. The vapor fraction 80, when discharged from the gas-liquid separator 33, has a first calorific value. The vapor fraction 80 is burned in the incinerator 220.

The condensed fraction 40 is also withdrawn from the gas-liquid separator 33, but in the form of a liquid phase at its boiling point. The condensed fraction 40 is subsequently re-evaporated in the second auxiliary indirect heat exchanger 285. Re-evaporation includes the 8 030308

The condensed fraction 40 is brought into indirect heat exchange contact with the second partial stream 72 of compressed steam, as a result of which heat is transferred from the second partial stream 72 of compressed steam to the condensed fraction 40. When re-evaporated, the condensed fraction 40 is converted into a fully evaporated stream having a second calorific value. After re-evaporation, the condensed fraction 40 is completely in the vapor phase. The fully evaporated stream obtained from condensed fraction 40 is combusted in gas turbine 320.

The nitrogen content in the liquid stream 90 can be maintained within the technical requirements in the range of temperatures of the discharge, expected during operation, with the help of the correct choice and determining the size of the end separator 50 flash evaporation at the design stage.

The first and second calorific values determine the amount of heat that can be released when one mole of fuel gas is burned. Both the so-called "high" calorific value and the "low" calorific value may be present, provided that the same conditions are used to compare these two calorific values. Preferably, a "low" calorific value is used to compare the two calorific values, since this is closest to the combustion conditions used in the invention. The calorific value can be determined by using ΑδΤΜ Ό3588-98 regardless of the composition of the steam fraction 80 and / or the condensed fraction 40. As a result of separation in a cooled gas-liquid separator 33, the second heat value (related to the condensed fraction 40) turns out to be higher than the first heat value ( related to the steam fraction 80). However, since the partially condensed intermediate stream essentially consists of two components, methane and nitrogen, the first and second calorific values exclusively affect the nitrogen content, respectively, of the vapor fraction 80 and the condensed fraction 40.

The vapor fraction 80 is burned in the combustion device 220, preferably at a first fuel gas pressure that does not exceed the second separation pressure. Thereby, use of the compressor can be avoided until the pressure in the vapor fraction 80 requires an increase. Preferably, the vapor fraction 80 is burned in the combustion device at a pressure of from 2 to 15 bar abs. (0.21.5 MPa), more preferably at a pressure of from 2 to 6 bar abs. (0.2-0.6 MPa).

The condensed fraction 40 may need to be compressed to a second fuel gas pressure that is higher than the second separation pressure. If the fuel gas compressor 360 is located in the condensed fraction discharge line 40 between the second auxiliary indirect heat exchanger 285 and the gas turbine 320, the fully evaporated stream may optionally be compressed in such fuel gas compressor 360 to the second fuel gas pressure before burning the fully evaporated gas turbine 320 The second pressure of the fuel gas is usually higher than the second separation pressure and can preferably meet the requirements for the pressure of the fuel gas determined selected gas turbine 320.

The reducing valve 245 allows instantaneous evaporation of some part of the condensed fraction 40 before passing the condensed fraction 40 through the second auxiliary indirect heat exchanger 285 by first passing the condensed fraction 40 through the reducing valve 245 and then indirectly exchanging the condensed fraction 40 with the second partial flow 72 of compressed vapor. Here, the lower temperature of the second partial stream 72 of compressed steam can be achieved when it is removed from the second auxiliary indirect heat exchanger 285, and / or a greater amount of cold present in the condensed fraction 40 can be recovered into the second partial stream of compressed steam. A reduction valve 245 controls the temperature of the discharge of the evaporated stream withdrawn from the second auxiliary indirect heat exchanger 285. The reduction valve 245, respectively, can be functionally connected to the first temperature sensor 247 located in the discharge line 40 of the condensed fraction downstream of the second auxiliary indirect heat exchanger 285, while the valve setting is adjusted according to the first temperature signal generated in the first temperature sensor 247. If provided an optional fuel gas compressor 390, a first temperature sensor, respectively, is located in the condensed fraction discharge line 40 between the second auxiliary indirect heat exchanger 285 and the optional fuel gas compressor 390. The first setpoint of the target temperature for this control loop can be set a few degrees lower, for example, 2 ° C lower, the temperature of the second partial flow of compressed steam at the inlet of the second auxiliary indirect heat exchanger 285. Preferably the temperature of the condensed fraction 40 at the outlet of the second auxiliary indirect heat exchanger between ambient temperature and temperature that is 10 ° C lower than the ambient temperature in order to effectively get the maximum benefit from the cold Present in the condensed fraction 40.

The second separation pressure is preferably higher than the first separation pressure. The second separation pressure can suitably be from 2 to 22 bar abs. (0.2-2.2 MPa), preferably from 5 to 22 bar abs. (0.5-2.2 MPa), more preferably from 5 to 15 bar abs. (0.5-1.5 MPa). The second

- 9 030308

separation pressure at the upper end of the range 2-22 bar abs. (0.2-2.2 MPa) contributes to the partial condensation of the compressed stream 70 and provides the opportunity for a higher pressure relief in the optional pressure reducing valve 245 and / or to maintain a higher pressure even after the pressure reducing valve 245, which leads to savings in fuel compression power gas in the optional fuel gas compressor 360. The lower end of the range contributes to the separation efficiency in the gas-liquid separator 33 and causes less excessive compression of the vapor fraction 80, which is supposed to be burned in the combustion device 220 at a relatively low pressure, usually less than 15 bar abs. (1.5 MPa). The proposed range is from 5 to 15 bar abs. (0.5-1.5 MPa) for the second separation pressure establishes a proper balance between the favorable and adverse effects, summarized above in this paragraph.

A typical pressure drop from 1.0 to 4.0 bar (0.1-0.4 MPa) through the optional pressure reducing valve 245 is considered adequate in typical cases.

In some embodiments, the implementation of the second separation pressure is in the range from 5 to 8 bar abs. (0.5-0.8 MPa), and this pressure most often meets the requirements for low-pressure fuel gas flow, suitable for transferring steam fraction 80 to combustion device 220 without the need for additional compression. Higher pressure can be selected if the combustion device 220 is located at a relatively large distance from the first gas-liquid phase separator, and / or when the vapor fraction 80 is supposed to pass through one or more heat recovery exchanger 85 cold. Under such circumstances, additional pressure drop can be expected during the transport of the exhaust gas to the combustion device 220. In one embodiment, the second separation pressure is about 6.5 bar abs. (0.65 MPa).

Cryogenic hydrocarbon composition 8 can be obtained from natural gas reservoirs, or oil, or coal seams. Alternatively, the cryogenic hydrocarbon composition 8 can also be obtained from another source, including, for example, an artificial source, such as the Fischer-Tropsch process. Preferably, the cryogenic hydrocarbon composition 8 contains at least 50 mol.% Methane, more preferably at least 80 mol.% Methane. The preferred initial temperature below -130 ° C can be achieved by passing the hydrocarbon stream 110 through the liquefaction plant 100. An embodiment of installing liquefaction installation 100 and passing hydrocarbon stream 110 through liquefaction installation 100 will be described in more detail below.

In the exemplary embodiment shown in FIG. 3, liquefaction unit 100 comprises a refrigerant circuit 101 for circulating refrigerant. The refrigerant circuit 101 includes a refrigerant compressor 160 connected to a refrigerant compressor drive 190 in a mechanical drive. The refrigerant compressor 160 is adapted to compress the flow of the spent refrigerant 150 and discharge the refrigerant in a compressed state to the line 120 of the compressed refrigerant. At least one heat exchanger 124 of the lead is usually provided in the line 120 of the compressed refrigerant circuit 101 of the refrigerant. The heat exchanger 124 of the discharge is configured to discharge heat from the compressed refrigerant stream carried by the compressed refrigerant line 120 to the environment, or to the air, or to a body of water, such as a lake, river or sea.

Installation 100 liquefaction usually contains a refrigerant refrigerant, made with the possibility of cooling the compressed refrigerant from the line 120 of the compressed refrigerant, from which the heat was removed in the heat exchanger 124 lead. When this flow of the cooled refrigerant get in line 131 of the cooled refrigerant.

The liquefaction plant 100 also comprises a cryogenic heat exchanger 180 connected to the outlet of the compressor 160 of the refrigerant via a line 120 of the compressed refrigerant. In the embodiment of FIG. 3, the cryogenic heat exchanger 180 also performs the function of the refrigerant cooler described in the previous paragraph, but this is not a requirement of the invention. A cryogenic heat exchanger is generally configured to establish an indirect heat exchange contact between the hydrocarbon stream 110 and the refrigerant of the refrigerant circuit 101.

A spent refrigerant line 150 connects the cryogenic heat exchanger 180 to the main suction side of the refrigerant compressor 160. The cooled refrigerant line 131 is in fluid communication with the spent refrigerant line 150 through the cold side of the cryogenic heat exchanger 180. The hydrocarbon flow 110 passes through the hot side of the cryogenic heat exchanger 180. The cold side and the hot side are in heat exchange contact with each other.

The main refrigerant return line 133 creates a fluid message between the cooled refrigerant line 131 and the cold side of the cryogenic heat exchanger 180. The main refrigerant return line 133 is in fluid communication with the spent refrigerant line 150 through the specified cold side and in the heat exchange configuration with the hot side. The main refrigerant control valve 134 is provided on the main refrigerant return line 133.

The cryogenic heat exchanger 180 receives the refrigerant flow in a compressed state from the main refrigerant return line 133 through the main refrigerant control valve 134 and leads to the refrigerant compressor 160. Thus, the cryogenic heat exchanger 180 forms part of the refrigerant circuit 101.

- 10 030308

Cryogenic heat exchanger 180 may be provided in any suitable form, including plate type with etched channels, plate-fin type, optionally in a heat-insulated casing, or shell-and-tube type heat exchanger, such as a spiral heat exchanger or coil heat exchanger.

A specific non-limiting example of a liquefaction unit and its refrigerant circuit, based on a shell-and-tube type heat exchanger and including a refrigerant compressor and a cryogenic heat exchanger, is included in FIG. 4 and 5. These figures will be described in detail below.

The refrigerant circulates in the refrigerant circuit 101 of the liquefaction plant 100. Circulation involves the actuation of the refrigerant compressor 160 and the compression of the refrigerant stream in the refrigerant compressor 160. Hydrocarbon stream 110 condenses and supercooled. Condensation and subcooling include indirect heat exchange of hydrocarbon stream 110 with refrigerant in liquefaction unit 100. The supercooled liquefied hydrocarbon stream thus formed is called the crude liquefied stream. Thus, the crude liquefied stream is formed from the hydrocarbon stream by condensation and subsequent supercooling of the hydrocarbon stream.

The hydrocarbon stream 110 in any of the examples described herein may be obtained from natural gas or oil reservoirs or coal seams. Alternatively, the cryogenic hydrocarbon composition 8 can also be obtained from another source, including, for example, an artificial source, such as the Fischer-Tropsch process. Preferably, the cryogenic hydrocarbon stream 110 contains at least 50 mol.% Methane, more preferably at least 80 mol.% Methane. The resulting liquid hydrocarbon product transported to line 90 of a liquid hydrocarbon product and / or stored in a cryogenic storage 210 is preferably liquefied natural gas (LNG).

Depending on the source, hydrocarbon stream 110 may contain different amounts of components other than methane and nitrogen, including one or more non-hydrocarbon components other than water, such as CO ₂ , Nd, H ₂ §, and other sulfur compounds; and one or more hydrocarbons heavier than methane, such as, in particular, ethane, propane and butanes, and possibly smaller amounts of pentanes and aromatic hydrocarbons. Hydrocarbons with a molecular weight corresponding to at least the mass of propane can be referred to here as C ₃ + hydrocarbons, and hydrocarbons with a molecular weight corresponding to at least the mass of ethane can be called here with C ₂ + hydrocarbons.

If necessary, the hydrocarbon stream 110 may be pretreated to reduce and / or remove one or more undesirable components, such as CO ₂ and H ₂ §, or it may be directed to other stages, such as pre-compression or the like. Such stages are well known to those skilled in the art, and their mechanisms are not discussed further here. The composition of hydrocarbon stream 110 thus varies depending on the type and location of the gas source and the pretreatment (s) used.

The crude liquefied stream is diverted to outlet line 1 from the liquefaction plant 100. The crude liquefied stream may contain from 1 to 7 mol.% Of nitrogen and more than 81 mol.% Of methane. The temperature of the crude liquefied stream in branch line 1 can be in the range of -165 to -120 ° C. The cryogenic hydrocarbon composition 8 is obtained from the crude liquefied stream by passing the crude pressure liquefied stream to a pressure reduction stage in the pressure reduction system 5, as a result of which the pressure decreases from the liquefaction pressure to the initial pressure from 1 to 2 bar abs. (0.1-0.2 MPa). During such a pressure reduction stage, an instantaneous vapor is usually generated.

Cryogenic hydrocarbon composition 8 contains a nitrogen-and methane-containing liquid phase and is usually at a temperature below -130 ° C.

In many cases, the temperature of the crude liquefied stream in branch line 1 may be in the range of -160 to -145 ° C. Within this narrower range, a lower cooling capacity is required in the liquefaction system 100 than in the case where lower temperatures are desired, while the magnitude of subcooling at pressures above 15 bar abs. (1.5 MPa) is high enough to avoid excessive formation of vapor of instantaneous evaporation when the pressure drops to the initial pressure in the range of 1-2 bar abs. (0.1-0.2 MPa).

The liquefaction unit 100 in the present specification, which has so far been presented very schematically, can represent any suitable unit and / or process for liquefying hydrocarbons, in particular, any process for liquefying natural gas that produces liquefied natural gas, and the invention is not limited to the specific choice of liquefaction unit. Examples of suitable liquefaction plants use processes with a cycle on one refrigerant (usually a cycle on one mixed refrigerant δΜΚ-processes, such as PK1CO, described in the work of KK LiuBi and R. Sigkoschasch 'ΈΝΟ Processiop op LoaPd pryyigsh8 "presented at the conference Sachesy 1998 (Dubai), but it is also possible to use a one-component refrigerant process, such as, for example, the ΒΗΡ-ΛΝΟ process, also described in the aforementioned paper by KK Törnpiep and R. Cnipkyapkep; processes with a cycle on two refrigerants

- 11 030308

(for example, a frequently used process with a mixed refrigerant and propane with the frequent abbreviation S3MN, described, for example, in patent υδ 4404008, or, for example, processes with two mixed refrigerants - ΌΜΚ, an example of which is described in patent υδ 6658891, or, for example, processes with two cycles, in which each refrigerant cycle contains a single component refrigerant); and processes based on three or more compressor sequences for three or more refrigeration cycles, an example of which is described in patent υδ 7114351.

Other examples of suitable liquefaction plants are described in patents υδ 5832745 (§Бе11 8МК); υδ 6295833 and И8 5657643 (both represent variants В1асск & Уеа1сЬ δΜΚ); υδ 6370910 (δΜ1). Another suitable example of the process is the so-called ΕΙΟυΕΕΙΝ process from Ahepk, described, for example, in the article Р-Υ Маши е! a1, entitled 'ΕΙΟυΕΕΙΝ: ΑΝ ΙΝΝΟνΑΤίνΕ RΚΟCΕδδ TO ΗΕΙΧΤΈ ΕΝΟ ί,' ΟδΤδ ". presented at the 22nd World Gas Conference in Tokyo, Japan (2003). Other suitable processes with three cycles are described, for example, in patents δδ 6962060; AO 2008/020044; υδ 7127914; ΌΕ 3521060Α1; υδ 5669234 (commercially known as the optimized cascade process); υδ 6253574 (commercially known as the cascade process with mixed refrigerants); υδ 6308531; in the publication of the application υδ 2008/0141711; Magk 1. ! a1, “Summer sarasIu kshDe 1tash AR-X (TM) Nypb ΕΝΟ Pgosekk”, October 2002, Doha, Qatar (13-16 October I 2002). These references are provided to demonstrate the wide applicability of the invention, and are not an exclusive and / or exhaustive list of possibilities.Not all of the examples above use gas turbines (based on an aircraft engine) as drives for compressors of the main refrigerant. that any actuators other than gas turbines can be replaced with a gas turbine in order to extract certain preferred benefits from the present invention.

Examples in which the liquefaction plant 100 is based, for example, on C3MH or δΗeII EMR, are briefly illustrated in FIG. 4 and 5. In both cases, the cryogenic heat exchanger 180 in the liquefaction unit 100 is selected as a spiral heat exchanger containing a hot side containing all the bundles, including the lower and upper bundles (respectively 181 and 182) of pipes for the hydrocarbon product, the lower and upper bundles (183 and 184 respectively) of pipes for the light fraction of the refrigerant (LMK) and a bundle of 185 pipes for the heavy fraction of the refrigerant (NMN). The cold side is formed by a annular zone of a cryogenic heat exchanger 180.

The lower and upper bundles 181 and 182 of pipes for the hydrocarbon product fluidly connect line 110 of the hydrocarbon stream to branch line 1. At least one precooling heat exchanger 115 for the cooled hydrocarbon may be provided in line 110 of the hydrocarbon stream upstream of the cryogenic heat exchanger 180 .

The refrigerant provided in refrigerant circuit 101 will be referred to as "primary refrigerant" to distinguish it from other refrigerants that can be used in a liquefaction plant 100, such as pre-refrigerant 127, which can provide cooling capacity for refrigerated hydrocarbon pre-cooling 115. The primary refrigerant in the present embodiment is a mixed refrigerant.

Refrigerant circuit 101 contains a spent refrigerant line 150 connecting a cryogenic heat exchanger 180 (in this case annular zone 186 of a cryogenic heat exchanger 180) to the main suction side of the refrigerant compressor 160, and a compressed refrigerant line 120 connecting the outlet of the refrigerant compressor 160 to the MP separator 128. One or several heat exchangers are provided in the line 120 of the compressed refrigerant, which in this example includes at least one heat exchanger 124 of the lead. The MH separator 128 is in fluid communication with the lower bundle of 183 pipes for LMK through line 121 of the light fraction of the refrigerant and with a bundle of pipes for NMH through line 122 of the heavy fraction of the refrigerant.

At least one pre-cooling heat exchanger 115 for cooled hydrocarbons and at least one pre-cooling heat exchanger 125 for the cooled main refrigerant are cooled by the pre-cooling refrigerant (via lines 127 and 126, respectively). The same pre-cooling refrigerant can be transferred from the same cycle to the pre-cooling refrigerant. In addition, at least one precooling heat exchanger 115 for the cooled hydrocarbon and at least one precooling heat exchanger 125 with the cooled main refrigerant can be combined into one heat exchanging precooling device (not shown). Reference is made to the patent υδ 6370910 as a non-limiting example.

At the transition point between the upper (182, 184) and lower (181, 183) tube bundles, a bundle of 185 tubes for NMH is in fluid connection with the 141 NMH line. Line 141 NMN is in fluid communication with annular zone 186 of the cryogenic heat exchanger 180 through the first return line 143 NMN, in which the valve 144 is used to control NMN. Through the specified annular zone 186 and in the heat exchange configuration with each one of the lower bundle 181 of pipes for the hydrocarbon product, the lower bundle of 183 pipes for LMK and the bundle of 185 pipes for HMN, the first return line 143 of HHM is fluidly connected to the line 150 of the spent refrigerant.

Above the upper bundles of 182 and 184 tubes, near the upper part of the cryogenic heat exchanger 180, pu- 12 030308

A choke of 184 pipes for LML is in fluid connection with the line 131 of the cooled refrigerant. The main refrigerant return line 133 creates a fluid message between the cooled refrigerant line 131 and the annular zone 186 of the cryogenic heat exchanger 180. The main refrigerant control valve 134 is provided in the main refrigerant return line 133. The main refrigerant return line 133 is in fluid communication with the spent refrigerant line 150 through the specified annular zone 186, and in the heat exchange configuration with each one of the upper and lower bundles 182 and 181 for the hydrocarbon product, respectively, each one of the bundles 183 and 184 pipes for LML and a bundle of 185 pipes for NML.

The refrigerant in the liquefaction plant 100 circulates in the refrigerant circuit 101, while the spent refrigerant 150 is compressed in the refrigerant compressor 160 to form the compressed refrigerant 120 from the spent refrigerant 150. Heat is removed from the compressed refrigerant discharged from the refrigerant compressor 160 through one or more heat exchangers provided in line 120 of compressed refrigerant, including at least one heat exchanger 124 of the lead. This leads to the formation of a partially condensed compressed refrigerant, which undergoes phase separation in the ML separator 128 into a light refrigerant fraction 121, consisting of vaporized components of the partially condensed compressed refrigerant, and a heavy refrigerant fraction 122, consisting of liquid components of the partially condensed compressed refrigerant.

The light fraction 121 of the refrigerant passes successively through the lower bundle of 183 LML and the upper bundle of 184 LMU of the cryogenic heat exchanger 180, while the heavy fraction 122 of the refrigerant passes through the bundle 185 NML of the cryogenic heat exchanger 180 to the transition point. When passing through these respective tube bundles, the respective light and heavy fractions of the refrigerant are cooled with the help of the light and heavy fractions of the refrigerant, which evaporate in the annular zone 186, again forming the exhaust refrigerant 150, which completes the cycle. At the same time, hydrocarbon stream 110 passes through a cryogenic heat exchanger 180, successively through the lower hydrocarbon beam 181 and the hydrocarbon upper beam 182, and is liquefied when the heavy fraction of the refrigerant evaporates and supercooling when the light fraction of the refrigerant evaporates.

Regardless of the type of liquefaction plant or the source of the cryogenic hydrocarbon composition 8, the stream of the first auxiliary refrigerant can be formed from a small stream of 90 liquefied hydrocarbons. This is illustrated in FIG. 4, where it can be seen that the auxiliary refrigerant supply line 132 continues between the liquid hydrocarbon product line 90 and the first auxiliary indirect heat exchanger 35. It is assumed that only about 0.2% of the 90 stream of liquefied hydrocarbons is required as the first auxiliary refrigerant stream 132. Typically, from 0.05 to 0.40% of a stream of 90 liquefied hydrocarbons may be needed as stream 132 of the first auxiliary refrigerant.

In the example shown in FIG. 4, the liquefied hydrocarbon product line 90 is divided into auxiliary refrigerant line 132 and main product line 91. Line 138 return auxiliary refrigerant in the appropriate case, continues between the first auxiliary indirect heat exchanger 35 and the end separator 50 flash evaporation and made with the possibility of returning the first auxiliary refrigerant containing heat from the first partial stream of compressed steam to the end separator 50 flash evaporation. This forms a half-open refrigeration cycle.

The advantage of using a small jet of liquid stream from line 90 of a liquefied hydrocarbon product for this purpose is that it can be relatively easily implemented on an existing installation without the need to interrupt or modify any part related to the source of the cryogenic hydrocarbon composition. The amount of optional equipment that needs to be installed is minimal. In addition, it is the coldest stream, easily accessible in an installation without the need for a special refrigeration cycle, and is usually abundant.

Optional pump 96 auxiliary refrigerant may be provided in line 132 of the first auxiliary refrigerant, through which a small jet of liquid stream 90 can be pumped to the first auxiliary indirect heat exchanger 35.

In another group of embodiments, and regardless of the type of liquefaction plant or the source of the cryogenic hydrocarbon composition 8, the first auxiliary refrigerant stream 132 may be formed by a small stream of the refrigerant circulation flow from the liquefaction plant, in countercurrent with which the hydrocarbon stream 110 condenses and supercooled. In such embodiments, the auxiliary refrigerant supply line 132 continues between the refrigerant circuit 101 of the liquefaction unit 100 and the first auxiliary indirect heat exchanger 35. The auxiliary refrigerant return line 138 continues between the first auxiliary indirect heat exchanger 35 and the liquefaction plant 100 refrigerant circuit 101 and is configured to return the auxiliary refrigerant containing heat from the stream of compressed steam, in the installation 100 liquefaction.

There are various ways to do this. In preferred embodiments, the implementation of 13 030308

Auxiliary refrigerant flow is formed by a small stream of the main refrigerant stream, in particular a small stream of the light fraction of the refrigerant. This latter case is illustrated in FIG. 5. Line 131 of the refrigerated refrigerant can be divided into auxiliary refrigerant supply line 132 and main refrigerant return line 133. The auxiliary refrigerant return line 138 at its inlet end may be in fluid communication with the auxiliary refrigerant supply line 132 via the first auxiliary indirect heat exchanger 35. At the outlet end, it is connected to the exhaust refrigerant line 150 via the first return line 143 NMC. In this way, a small stream of flow is conveniently directed back to the main refrigerant circuit through the annular zone 186 of the cryogenic heat exchanger 180, where it can still contribute to heat removal from the flow in the upper and / or lower tube bundles. Ultimately, the auxiliary refrigerant return line 138 is thus connected to the spent refrigerant line 150. Alternatively, the auxiliary refrigerant return line 138 may be directly connected to the spent refrigerant line 150.

The specified composition of the auxiliary refrigerant in this group of embodiments contains from 25 to 40 mol.% Nitrogen; from 30 to 60 mol.% of methane and up to 30 mol.% of C ₂ (ethane and / or ethylene), as a result of which the auxiliary refrigerant contains at least 95% of these components, and / or the total content of nitrogen and methane is at least 65 mol%. The composition within these ranges can be easily accessible from the main refrigerant circuit, if a mixed refrigerant is used to subcool the stream of liquefied hydrocarbons.

Using a small jet from the main refrigerant stream has the advantage that the amount of additional equipment that needs to be installed is minimal. For example, an additional auxiliary refrigerant compressor and an auxiliary refrigerant condenser that would be needed in the case of a separate independent auxiliary refrigerant cycle will not be required.

There may be other flow options for the first auxiliary refrigerant. However, in any case, the flow of the first auxiliary refrigerant does not contain any condensed fraction.

In addition, the auxiliary cooling capacity reported by the flow of the first auxiliary refrigerant in the first auxiliary indirect heat exchanger 35 can be changed by means of the auxiliary refrigerant control valve 135, which, as illustrated in FIG. 4 and 5 may be provided on the auxiliary refrigerant supply line 132. Various management strategies are possible. For example, the auxiliary refrigerant control valve 135 is operatively associated with an optional level controller 37 provided in the gas-liquid separator 33 (illustrated, for example, in FIG. 1) to establish a constant liquid level in the gas-liquid separator 33 by adjusting the amount of partial condensation of compressed steam 70, which occurs in the first auxiliary indirect heat exchanger 35. Another example includes an auxiliary refrigerant control valve 135, functionally connected to an optional temperature sensor (not shown) located between the first auxiliary indirect heat exchanger 35 and the gas-liquid separator 33 to establish a constant temperature of the partially condensed intermediate stream.

A suitable setpoint for the temperature sensor can be obtained based on the desired nitrogen content in the condensed fraction 40, which meets the technical requirements for the composition of the fuel gas of the gas turbine 320. The remaining nitrogen remains in the vapor fraction. The discharge temperature of the crude liquefied flow in the exhaust line 1 can be adjusted to ensure that the total calorific value available in the tail pair 64 and / or the partially condensed intermediate flow meets the general requirements for the combustion gas of the combustion device (s) 220 and the gas turbine (turbines) 320 For example, if the calorific value of tail steam 64 is too high, the temperature of the discharge can be lowered to reduce the amount of methane that is instantaneously and mating at the stage of pressure reduction in the system 5 pressure reduction The distribution of nitrogen between the vapor fraction 80 and the condensed fraction 40 is regulated by the auxiliary cooling capacity.

FIG. 6 illustrates the expanded instantaneous evaporation end separator system described previously in patent I8 6014869, the contents of which are incorporated herein by reference. The instantaneous evaporation end separator 50 in this case contains a gas-liquid contact device (for example, in the form of a nozzle or a set of contact plates), a lower inlet device 52 connected to a reboiler 55, and an upper inlet device 53. The cold recovery stream 66 consists of a side stream of natural gas the same composition as the crude liquefied stream

1. It is assumed that the cryogenic hydrocarbon composition 8 consists of a cold recovery stream 66 and a crude liquefied stream 1 obtained from the pressure reduction system 5. The rest in FIG. 6 corresponds to FIG. one.

Material and heat balance calculations were performed using Pro2 simulation software to demonstrate the feasibility of implementing the proposed methods and set up 14 030 308

wok Calculations are made for the embodiments illustrated in FIG. 6. For the calculations, it is assumed that the stream 64 of the tail steam between the cold recovery heat exchanger 65 and the instantaneous evaporation end compressor 260 contains steam from the end evaporator 50 separator along with the stripping gas stream from the cryogenic storage 210. In addition, it is assumed that the bypass control valve 77 steam, a steam recycle regulating valve 88, a recirculation valve 14, and an external desorbing steam flow control valve 73 are closed and in a state of no flow.

In tab. 1-4 show the results for the embodiments based on FIG. 6, in which the stream 132 of the first auxiliary refrigerant is provided with a small stream of liquid stream in the line 90 of the stream of liquefied hydrocarbon product.

Tab. 1 and 2 correspond to one calculation, in which the second separation pressure is in the range from 4 to 8 bar abs. (0.4-0.8 MPa). This is called a low pressure case. Tab. 3 and 4 correspond to another calculation, which is called the case of high pressure. In another calculation, the second separation pressure is in the range of 10 to 20 bar abs. (1.0-2.0 MPa). This affects the pressure drop that occurs through the reduction valve 245, which, in turn, affects the cooling capacity, which is available in the second auxiliary indirect heat exchanger 285. This, of course, is achieved due to the additional compression capacity. It can be seen that the temperature at which the phases are separated in the gas-liquid separator 33 can be higher in this pressure range. However, a larger amount of liquid hydrocarbon stream must be used as the flow of the first auxiliary refrigerant.

Table 1

(case of low pressure)

No stream Pressure (bar abs.) Temperature GO Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) Sz + (mol%) one 74.8 -155 211 3.93 95.7 0.39 1a 74.2 -163 211 3.93 95.7 0.39 1b 9.88 -164 211 3.93 95.7 0.39 eight 1.05 -167 218 3.93 95.7 0.39 60 1.05 -167 19.4 41.4 58,6 0.00 66 9.88 -157 6.65 3.93 95.7 0.39 90 1.12 -163 198 1.09 98.5 0.42 138 1.50 -134 0.30 1.09 98.5 0.42

table 2

(case of low pressure, continued)

No stream Pressure (bar abs.) Temperature GO Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) Sz + (mol%) eight 1.05 -167 218 3.93 95.7 0.39 40 6.50 -162 19.6 29.0 71.0 0.00 64 0.85 -27 23.7 36.8 63.2 0.00 70 7.50 +31 23.7 36.8 63.2 0.00 71 7.50 +31 3.48 36.8 63.2 0.00 71a 7.00 -131 3.48 36.8 63.2 0.00 71b 6.50 -142 3.48 36.8 63.2 0.00 72 7.00 -169 20.3 36.8 63.2 0.00 80 6.50 -162 4.12 86.4 13.6 0.00 90 1.12 -163 198 1.09 98.5 0.42 132 2.00 -163 0.30 1.09 98.5 0.42 138 1.50 -134 0.30 1.09 98.5 0.42 230 1.00 -159 3.20 17.3 82.7 0.00 240 3.00 -172 19.6 29.0 71.0 0.00

Table 3

(high pressure case)

No stream Pressure (bar abs.) Temperature GO Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) C 2+ (mol%) one 74.8 -155 210 3.93 95.7 0.39 1a 74.2 -163 210 3.93 95.7 0.39 1b 9.88 -164 210 3.93 95.7 0.39 eight 1.05 -167 217 3.93 95.7 0.39

No stream Pressure (bar abs.) HS temperature) Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) C? + (mol%) 60 1.05 -167 19.4 41.6 58.4 0.00 66 9.73 -157 6.58 3.93 95.7 0.39 90 1.12 -163 198 1.11 98.5 0.42 138 1.50 -128 0.49 1.11 98.5 0.42

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Table 4

(case of high pressure, continued)

No stream Pressure (bar abs.) Temperature HS) ' Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) C ₂ + (mol.%) eight 1.05 -167 217 3.93 95.7 0.39 40 16.5 -135 12.5 19.3 80.7 0.00 64 0.85 -27 23.5 36.9 63.1 0.00 70 17.5 +31 23.5 36.9 63.1 0.00 71 17.5 +31 8.18 36.9 63.1 0.00 71a 17.0 -125 8.18 36.9 63.1 0.00 71b 16.5 -127 8.18 36.9 63.1 0.00 72 17.0 -140 15.3 36.9 63-1 0.00 80 16.5 -135 10.9 62.9 37.1 0.00 90 1.12 -163 198 1.09 98.5 0.42 132 2.00 -163 0.49 1.11 98.5 0.42 138 1.50 -128 0.49 1.11 98.5 0.42 230 1.00 -160 4.32 18.9 81.1 0.00 240 9.50 -144 12.5 19.3 80.7 0.00

The low pressure case calculated in the present example produces a low quality fuel gas that is removed from the heat recovery heat exchanger 85 at a pressure of 5 bar abs. (0.50 MPa) and a temperature of 22 ° C; and the re-evaporated condensed fraction, which is discharged from the second auxiliary indirect heat exchanger 285 at a pressure of 3.0 bar abs. (0.30 MPa) and a temperature of 25 ° C. The latter can be used as a high quality fuel gas.

The high-pressure case calculated in this example produces a low-quality fuel gas, which is removed from the cold recovery heat exchanger 85 at a pressure of 5 bar abs. (0.50 MPa) and a temperature of 28 ° C; and the re-evaporated condensed fraction, which is discharged from the second auxiliary indirect heat exchanger 285 at a pressure of 9.00 bar abs. (0.30 MPa) and a temperature of 19 ° C. The latter can be used as a high quality fuel gas.

As in the case of low pressure, and in the case of high pressure, the final composition of the stocks of liquefied hydrocarbons stored in the cryogenic storage 210 is 0.83 mol.% Nitrogen, 98.74 mol.% Methane and 0.43 mol.% C ₂ + where C ₂ + means all hydrocarbons having a mass corresponding to the mass of ethane and above. The stream of liquefied hydrocarbons, passing through line 91 of the main product to cryogenic storage 210, has slightly more nitrogen than the reserves of liquefied hydrocarbons stored in cryogenic storage 210.

In tab. 5 and 6 show the results for the embodiments based on FIG. 6, in which the stream 132 of the first auxiliary refrigerant is provided with a small stream of flow from the line 131 of the cooled refrigerant. In this case, the molecular mass MA of the auxiliary refrigerant 132, which contains 21.6 mol.% Of nitrogen, 58.6 mol.% Of methane and 19.8 mol.% Of C ₂ + components (mainly ethane), is 21.59.

Table 5

(case of low pressure)

No stream Pressure (bar abs.) Temperature HS) Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) Ca + (mol%) one 74.8 -155 211 3.93 95.7 0.39 1a 74.2 -162 211 3.93 95.7 0.39 1b 9.90 -163 211 3.93 95.7 0.39 eight 1.05 -167 218 3.93 95.7 0.39 60 1.05 -167 19.4 41.3 58.7 0.00 66 9.90 -156 6.70 3.93 95.7 0.39 90 1.12 -163 198 1.09 98.5 0.42 138 1.50 -134 0.30 1.09 98.5 0.42

Table 6

(case of low pressure, continued)

No stream Pressure (bar abs.) HS temperature) Speed receipts (kg / s) Nitrogen (mol%) Methane (mol%) with ₂ + (mol.%) eight 1.05 -167 218 3.93 95.7 0.39 40 6.50 -162 19.7 29.0 71.0 0.00 64 0.85 -26 23.7 36.7 63.3 0.00 70 7.50 +31 23.7 36.7 63.3 0.00 71 7.50 +31 3.47 36.7 63.3 0.00 71a 7.00 -130 3.47 36.7 63.3 0.00 71b 6.50 -142 3.47 36.7 63.3 0.00 72 7.00 -169 20.3 36.7 63.3 0.00 80 6.50 -162 4.09 86.4 13.6 0.00 90 1.12 -163 198 1.09 98.5 0.42 132 6.95 -157 1.73 21.6 58.6 19.8 138 6.45 -142 1.73 21.6 58,6 19.8 230 1.00 -160 4.32 18.6 81.4 0.00 240 3.00 -172 19.7 29.0 71.0 0.00

C2 + means all hydrocarbons having a mass corresponding to the mass of ethane and more. In this

- 16 030308

In the case of LMK, the C ₂ + refrigerant consists mainly of ethane. Tab. 5 and 6 correspond to one calculation, in which the second separation pressure is in the range from 4 to 8 bar abs. (0.4-0.8 MPa).

As calculated in the present example, low quality fuel gas is removed from the heat recovery exchanger 85 of cold at a pressure of 5 bar abs. (0.50 MPa) and a temperature of 28 ° C; and the re-evaporated condensed fraction is withdrawn from re-evaporator 285 at a pressure of 3.00 bar abs. (0.30 MPa) and a temperature of 25 ° C. The latter can be used as a high quality fuel gas.

The final composition of the liquefied hydrocarbon reserves stored in the cryogenic storage 210 is 0.82 mol.% Nitrogen, 98.75 mol.% Methane and 0.43 mol.% C ₂ +. The stream of liquefied hydrocarbons, passing through line 91 of the main product to cryogenic storage 210, has slightly more nitrogen than the reserves of liquefied hydrocarbons stored in cryogenic storage 210.

In any of the examples above, the preferred liquefaction pressure range, in which the crude liquefied stream is diverted to flow line 1 from the liquefaction plant 100, is between 15 and 120 bar abs. (1.5-12.0 MPa), more preferably from 15 to 90 bar abs. (1.5-9.0 MPa) or 45 to 120 bar abs. (4.5-12.0 MPa). The most preferred liquefaction pressure range is from 45 to 90 bar abs. (4.5-9.0 MPa). In the case when the crude liquefied stream consists of at least 80 mol.% Of methane and nitrogen, the preferred temperature range for the crude liquefied stream in branch line 1 can be from -165 to -120 ° C.

In any of the above examples, it is assumed that the vapor fraction 80 contains from 30 to 90 mol.% Nitrogen, preferably from 30 to 80 mol.% Nitrogen or from 45 to 90 mol.% Nitrogen, more preferably from 45 to 80 mol.% nitrogen, most preferably from 50 to 80 mol.% nitrogen. To achieve a nitrogen content of 50 to 80 mol.%, Such as about 60 mol.%, A sufficient amount of methane must be re-condensed from the stream 70 of compressed steam. This can be done, for example, by using a pressure of flow 70 of compressed steam of 4 to 8 bar abs. (0.4-0.8 MPa) and the temperature of the partially condensed intermediate stream ranges from -150 to -135 ° C. The temperature range may have higher endpoints if the pressure exceeds 8 bar abs. (0.8 MPa).

In addition, the condensed fraction 40 typically contains up to 30 mol.% Of nitrogen and at least 5 mol.%, Preferably at least 10 mol.%. Striving for lower values will cost more auxiliary cooling capacity, whereas this is not necessary for typical gas turbines, and in particular for gas turbines based on aircraft engines.

Compressors that are part of the process of liquefying hydrocarbons in the liquefaction unit 100, in particular any refrigerant compressor, including refrigerant compressor 160, can be driven by any type of suitable compressor drive 190, including any one selected from the group consisting of a gas turbine, steam turbine and electric motor, as well as their mutual combinations. As a rule, this also applies to the drive 190 of the refrigerant compressor.

The gas turbine can be selected from the group of so-called industrial gas turbines or from the group of so-called gas turbines based on aircraft engines. The group of gas turbines on the basis of aircraft engines includes Kosh-Kosese TgssSh 60, KV211 or 6761, and Seyega Elyes1 LM8100TM, LM6000, LM5000 and LM2500 and variants of any of them (for example, LM2500 +).

Accordingly, the gas turbine 320, in which the condensed fraction 40 is ultimately burned, is driven by a refrigerant compressor 190, which is in engagement with the refrigerant compressor 160. Gas turbine 320 may drive refrigerant compressor 160.

As a rule, choose a second fuel gas pressure in the range from 15 to 75 bar abs. (1.5-7.5 MPa), more preferably in the range from 45 to 75 bar abs. (4.5-7.50 MPa). Typically, the set fuel gas pressure for most common types of industrial gas turbines is from about 15 to about 25 bar abs. (1.5-2.5 MPa) on average. However, the latest generation of industrial gas turbines requires fuel gas with a relatively high pressure, such as in the range of 35 to 45 bar abs. (3.5-4.5 MPa). Range from 45 to 75 bar abs. (4.5-7.5 MPa) is recommended to meet the fuel gas pressure requirements of typical gas turbines based on aircraft engines.

The nitrogen content in the liquid stream 90, as a rule, does not exceed the desired maximum of about 1.1 mol.%. In some embodiments, the implementation of the amount of nitrogen in the stream 90 of liquid hydrocarbons is from 0.5 to 1 mol.%, Preferably as close as possible to 1.0 mol.%, But not exceeding the specified maximum of about 1.1 mol.%.

It is known that the stripping gas is formed as a result of thermal evaporation caused by heat supplied to the liquefied product, for example, in the form of heat leakage into storage tanks, LNG pipelines, and heat input from the LNG installation pumps. In any of the examples and embodiments illustrated here, the stripping gas may not necessarily be introduced into the tail steam line 64, upstream or downstream of the terminal evaporator 260, and is subject to phase separation in the gas-liquid separator 33. 030308

from the cryogenic storage 210, possibly via the stripping gas supply line 230, as illustrated, for example, in FIG. 6. Steam gas is formed as a result of the addition of heat to at least a part of liquefied hydrocarbons, as a result of which a part of the methane-containing liquid phase in liquefied hydrocarbons evaporates to form the said stripping gas.

Although this is not a requirement of the invention, it is assumed that the proposed method can be carried out in the sea on a floating barge. Similarly, the installation can be installed on a floating barge for work at sea. Cryogenic storage can accordingly be built into the hull of the same barge.

The person skilled in the art will appreciate that the present invention can be implemented in various ways without deviating from the scope of the appended claims.

Claims (16)

CLAIM 1. A method of producing a liquefied hydrocarbon stream, in which provide a hydrocarbon composition, cooled to cryogenic temperatures and containing the liquid phase, including nitrogen and methane, at an initial pressure of 1 to 2 bar abs. (0.1-0.2 MPa); phase separation of the hydrocarbon composition, cooled to cryogenic temperatures, is carried out in an instantaneous evaporation end separator at a first separation pressure of 1 to 2 bar abs. (0.1-0.2 MPa) for vapor tail flow and liquid flow; divert the liquid stream from the end separator instantaneous evaporation in the form of a stream of liquefied hydrocarbons; compress the vaporous tail stream in an instantaneous evaporation end compressor to a pressure in excess of 2 bar abs. (0.2 MPa) to obtain a stream of compressed steam; separating the compressed steam into the first part of the compressed steam flow and the second part of the compressed steam flow, so that said first part of the compressed steam flow and said second part of the compressed steam flow have the same composition and phase state as the compressed steam; form a partially condensed intermediate stream containing the condensed fraction and vapor fraction through indirect heat exchange of the first part of the compressed steam flow with the flow of the first auxiliary refrigerant as a result of heat transfer from the first part of the compressed steam flow to the flow of the first auxiliary refrigerant and due to indirect heat exchange of the second part compressed steam with a stream of the second auxiliary refrigerant as a result of heat transfer from the second part of the stream of compressed steam to the stream of the second auxiliary flax refrigerant, and recombine portions of both streams; in the gas-liquid separator, the condensed fraction is separated from the vapor fraction of the streams after recombination at the second separation pressure; withdrawing said vapor fraction having a first calorific value from a gas-liquid separator; burning said vapor fraction in a combustion device other than a gas turbine; withdrawing said condensed fraction from a gas-liquid separator; re-evaporate the specified condensed fraction with the conversion of the condensed fractions into a fully evaporated stream having a second calorific value, which is higher than the first calorific value; burn the specified fully evaporated stream in a gas turbine; however, the re-evaporation of the condensed fraction includes the specified indirect heat exchange of the second part of the compressed steam flow by passing the condensed fraction through the reducing valve to form, thus, the flow of the second auxiliary refrigerant, and subsequent exposure of the specified flow of the second auxiliary refrigerant specified indirect heat exchange with the second part of the stream compressed steam, which leads to complete evaporation of the condensed fraction, while the flow of the first auxiliary nogo refrigerant contains no kakoylibo condensed fraction. 2. The method according to claim 1, in which the specified formation of a partially condensed intermediate stream includes a partial condensation of at least the first part of the stream of compressed steam after the specified separation and before the specified recombination. 3. The method according to claim 1 or 2, wherein said formation of a partially condensed intermediate stream from compressed steam further includes indirect heat exchange of the first part of the compressed steam stream with the vapor fraction from the gas-liquid separator prior to said combustion of the vapor fraction in said combustion device. 4. The method according to claim 3, wherein said separation of compressed steam is carried out with an adjustable separation ratio, the method also comprising adjusting the separation ratio in accordance with the temperature signal characterizing the temperature of the vapor fraction from the gas-liquid separator, after said indirect heat exchange with the first part of the compressed stream steam while maintaining the specified temperature of the vapor fraction at a given target value. - 18 030308 5. The method according to any one of claims 1 to 4, in which, after re-evaporation of the condensed fraction and before burning the fully evaporated stream, the fully evaporated stream is compressed in the fuel gas compressor to a second fuel gas pressure exceeding the second separation pressure of 15 to 75 bar abs (1.5-7.5 MPa), preferably up to a second fuel gas pressure of 45 to 75 bar abs. (4.5-7.5 MPa). 6. The method according to any one of claims 1 to 5, in which the vapor fraction is burned in said combustion device at a first fuel gas pressure not exceeding the second separation pressure, preferably at a pressure of from 2 to 15 bar abs. (0.2-1.5 MPa). 7. The method according to any one of claims 1 to 6, in which the second separation pressure is from 2 to 22 bar abs. (0.2-2.2 MPa), preferably from 5 to 22 bar abs. (0.5-2.2 MPa), more preferably from 5 to 15 bar abs. (0.5-1.5 MPa). 8. The method according to any one of claims 1 to 7, in which the liquid stream and the stream of liquefied hydrocarbons contain less than 1.1 mol.% Nitrogen. 9. The method according to any one of claims 1 to 8, in which more than 30 mol.% Of the partially condensed intermediate stream consists of nitrogen and less than 30 mol.% Of the condensed fraction withdrawn from the gas-liquid separator consists of nitrogen. 10. The method according to any one of claims 1 to 9, in which the vapor fraction and the condensed fraction coexist in the same state of thermodynamic equilibrium and are separated in the indicated state into a vapor fraction and the condensed fraction. 11. The method according to any one of claims 1 to 10, wherein after said discharge of a liquid stream from a terminal separator of instantaneous evaporation as a stream of liquefied hydrocarbons, the specified stream of liquefied hydrocarbons is transported to a cryogenic storage unit built into the hull of a floating barge. 12. Installation for producing a liquefied hydrocarbon stream method according to any one of claims 1 to 11, containing a feed line cooled to cryogenic temperatures, connected to a source of hydrocarbon composition, cooled to cryogenic temperatures and containing a liquid phase comprising nitrogen and methane; an instantaneous evaporation end separator configured to receive the hydrocarbon composition cooled to cryogenic temperatures and to separate the hydrocarbon composition cooled to cryogenic temperatures into a liquid stream and a vaporous tail stream; a liquid hydrocarbon product line that is fluidly connected to the bottom of an instantaneous evaporation end separator to discharge said liquid stream as a stream of liquefied hydrocarbons from an instantaneous evaporation end separator; a tail steam removal line in fluid communication with the head of the end flash separator to discharge said vaporous tail stream from the flash end separator; a terminal instantaneous evaporation compressor located on the tail steam removal line, designed to compress the vapor tail flow, to produce a stream of compressed steam; a flow divider located on the compressed steam exhaust line dividing the compressed steam line into the first branch and the second branch, the first branch being located between the flow divider and the gas-liquid separator and the second branch between the stream divider and the gas-liquid separator; the first indirect indirect auxiliary heat exchanger, located in the first branch, adapted to receive the first part of the compressed vapor stream located in the first branch, and with the possibility of indirect heat exchange contact between the first part of the compressed vapor stream and the first auxiliary refrigerant stream; a second indirect indirect auxiliary heat exchanger located in the second branch, configured to receive the second part of the compressed steam flow located in the second branch and with the possibility of indirect heat exchange contact between the second part of the compressed steam flow and the second auxiliary refrigerant flow; gas-liquid separator located downstream from the first auxiliary heat exchanger and the second auxiliary heat exchanger and configured to receive a partially condensed intermediate stream from the first auxiliary heat exchanger and the second auxiliary heat exchanger, the partially condensed intermediate stream containing a condensed fraction and a vapor fraction; the discharge line of the vapor fraction, connected in fluid with the head part of the gas-liquid separator, made with the possibility of receiving the vapor fraction from the gas-liquid separator; a combustion device, other than a gas turbine, which is in fluid communication with a gas-liquid separator using the vapor fraction abstraction line, for receiving and burning the vapor vapor abstracted; the withdrawal line of the condensed fraction, which is in fluid communication with the bottom part of the gas 19 030308 a liquid separator configured to receive the condensed fraction from the gas-liquid separator; a gas turbine, in fluid communication with a gas-liquid separator using a condensed fraction withdrawal line, for receiving and burning the diverted condensed fraction; a re-evaporation device located on the discharge line of the condensed fraction between the gas-liquid separator and the gas turbine and configured to convert the condensed fraction into a fully evaporated stream before burning in the gas turbine; a reducing valve located on the line for withdrawing the condensed fraction between the gas-liquid separator and the re-evaporation device; the second auxiliary heat exchanger is a re-evaporation device, the condensed fraction downstream of the pressure reducing valve is the flow of the second auxiliary refrigerant, and the flow of the first auxiliary refrigerant does not contain any condensed fraction. 13. Installation according to item 12, in which the first auxiliary heat exchanger is a condenser configured to extract heat from the first part of the stream of compressed steam in the first branch, at least partially condensing the first partial stream of compressed steam. 14. Installation according to item 12 or 13, in which the gas-liquid separator consists of a drum that does not contain any internal elements forming the vapor / liquid contact section. 15. Installation according to any one of paragraphs.12-14, additionally containing a heat recovery exchanger cold, located on the discharge line of the vapor fraction upstream from the device for burning, and the heat recovery exchanger cold located in the first branch in addition to the first auxiliary heat exchanger. 16. Installation according to any one of paragraphs.12-15, in which the specified line of liquid hydrocarbon product fluidly connects the bottom part of the end separator instantaneous evaporation with cryogenic storage, built into the hull of the floating barge. - 20 030308