RU2531099C1 - Complex storage of fluid - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: method of gas liquefaction includes the following stages. The supplied flow is supplied into liquefier, containing, at least, warm expander and cold expander. The supplied flow is compressed in the liquefier up to the pressure above critical one and the compressed supplied flow is cooled down to the temperature below the critical temperature for formation of dense phase high-pressure flow. Dense phase high-pressure flow is taken from liquefier and the pressure of dense phase high-pressure flow is decreased in the expansion device for formation of resulting two-phase flow. Then the resulting two-phase flow is immediately supplied to the storage tank. The selected part of the resulting two-phase flow is merged instantly with boiling out vapour of the liquid in the storage tank for formation of integrated steam flow. And the temperature of dense phase high-pressure flow is lower, than the temperature of output flow of the cold expander. The system of atmospheric gas liquefaction is also described.

EFFECT: development of simple and inexpensive liquefaction method with effective and beneficial extraction of vapours instantly escaped from tanks.

15 cl, 4 dwg, 2 tbl

Description

BACKGROUND OF THE INVENTION

Nitrogen liquefiers are well known in the art, typically coupled, for example, to a nitrogen generator or air separation unit (ASU). Liquefiers can be used to liquefy gaseous nitrogen of low pressure, for example, from ASU. Fluidizers can also take at least a portion of their feed material from the ASU at higher pressures and / or at cryogenic temperatures for liquefaction.

In traditional liquefaction processes, high-pressure nitrogen is cooled to cryogenic temperatures to form a dense-phase fluid (for example, a fluid below a critical temperature and above a critical pressure), and then pressure is reduced, typically by using a valve or a dense fluid expander, it forms mainly a liquid with a certain amount of instantly released steam. This biphasic mixture is then fed to a separator. The cold expander also typically releases steam or a slightly liquefied stream into the separator. The steam from the separator is reheated to ambient temperature, and then recycled to the process, while the liquid is supercooled before being fed, for example, to an insulated liquid storage tank. This subcooling can be accomplished by reducing the pressure in the second separator at a lower pressure or indirectly in the subcooler due to heat exchange with boiling liquid at low pressure. The use of a subcooler allows you to maintain sufficient liquid pressure to transfer it to storage without using, for example, pumps.

Lots of liquid produced in the liquefier can be stored, for example, in an isolated tank for storing liquid with subsequent use or can be transported by tankers, while other batches of liquid can be returned to the ASU, for example, to provide cooling.

If a second separator is used, then to avoid the use of additional pumps, the second separator should be raised above the level of the storage tank.

However, storing fluid in insulated storage tanks is not a simple solution. Ultimately, due to imperfect insulation, for example, heat leaks from the environment into an insulated liquid storage tank. In addition, part of the liquid stored in insulated liquid storage tanks is vaporized and requires the production of additional liquid to compensate for these losses. Typically, the cold vapor that is generated by the evaporation of a liquid in an insulated liquid storage tank is released into the atmosphere to prevent pressure build-up in an isolated liquid storage tank, but then the refrigeration capacity is lost during the implementation of this method.

Accordingly, the previously described nitrogen liquefiers coupled to ASU plants were problematic for several reasons. Firstly, the extraction of instantly released steam or cold boiling steam from an isolated tank with liquid nitrogen requires the use of a cold fan. Cold fans were used to create pressure on instantly released steam or cold boiling off steam from the tank so that it was under sufficient pressure to send it back to the liquefier or ASU to ensure it was cooled to recover. However, when using a fan, only a fraction of the refrigeration can be recovered, since the fan power is ultimately added to the cold boiling steam stream as heat. In addition, fans are inconvenient and expensive to install and maintain, and also add additional complexity to these systems and methods, which makes the use of fans uneconomical

Secondly, the use of liquid-nitrogen cold-end separators complicates the method and makes it more expensive to implement, since all of them must be enclosed in an insulated thermal container. Large and complex thermal containers are difficult to deal with when planning delivery routes, as it may be difficult or even impossible to reach specific destinations with such large, pre-insulated cargoes (for example, thermal container cargoes).

Third, liquefaction methods typically include subcoolers to reduce the instantaneous gas generated in the tank. Such subcoolers also add undesirable cost and complexity to the process.

In addition, when in the early liquefiers (i.e., liquefiers used prior to the liquefiers of the current state of the art), one expander and only one separation device were used, these first liquefiers were relatively ineffective. To increase the effectiveness of liquefiers in later designs of liquefiers, several expanders and several separators were used to extract instantly released vapors at intermediate pressure. For many years to this day, the extraction of instantly emitted vapors at an intermediate pressure has been considered necessary, since the instantly emitted vapor generated when a liquid product enters the liquid storage tank is undesirable and thus must be released into the atmosphere to control the pressure in the tank. Such an outburst, of course, would lead to the loss of valuable refrigeration from instantly released vapors.

Thus, in the industrial gas industry, there is a need for a simple and inexpensive liquefaction process with efficient and useful extraction of instantly released vapors and boiling vapors from the tank without the complexity of cold fans, cold end separators or subcoolers.

SUMMARY OF THE INVENTION

The described embodiments meet the needs of the prior art by providing a simplified and efficient liquefier using a fluid storage tank as a separator for instantly released vapors and to extract instantly released steam and boiling off steam from the storage through the liquefier. Separators and subcoolers can be excluded from the construction of the fluidizer and process. Since the cold portion of the liquefier is essentially only a heat exchanger and pipelines, it can be insulated directly and a separate thermal container design is excluded. In the described embodiments, the implementation used the design and method, the opposite of the conventional to create effective structures of the fluidizer and methods.

The production of liquid in a separate liquefier, rather than in an ASU installation, has operational advantages, such as it is easy to turn it on and off depending on the need, but it also has significant disadvantages of high capital costs and low efficiency associated with a separate production unit. In General, increasing the efficiency of the method will increase capital costs, and capital costs should increase to increase efficiency. The described method and system can reduce these capital costs while increasing efficiency.

In one embodiment, a gas liquefaction method is described comprising supplying a feed stream to a fluidizer, comprising at least a warm expander and a cold expander, compressing the feed stream in the fluidizer to a pressure above its critical pressure, and cooling the compressed feed stream to a temperature below it critical temperature in order to form a high-pressure dense-phase flow, diverting a high-pressure dense-phase flow from a fluidizer and reducing the pressure of a dense-phase high-pressure flow in the expansion device to form the resulting two-phase stream, and then directly supply the resulting two-phase stream to the storage tank, as well as combining the instantly emerging part of the resulting two-phase stream with boiling off steam from the liquid in the tank to form a combined vapor stream, while the temperature of the high-density high-pressure stream lower than the temperature of the outlet stream of the cold expander.

In another embodiment, an atmospheric gas liquefaction system is disclosed comprising a first conduit for receiving a feed stream, a fluidizer fluidly coupled to a first conduit for compressing and cooling the feed stream to form a high-density, high-pressure fluid stream in which the fluidizer contains at least least a warm expander, a cold expander, a compressor for compressing the feed stream to a pressure exceeding its critical pressure, and a heat exchanger for cooling with the compressed feed stream to a temperature below the critical temperature, a second pipe fluidically connected to a fluidizer to receive a high-density high-pressure flow from a fluidizer, a first expansion device fluidly connected to a second pipe to reduce the pressure of the high-pressure high-pressure flow to form a resulting two-phase a stream, a third conduit fluidly coupled to a first expansion device for receiving a two-phase expanded flow, and also a reserve a storage container connected in fluid with a third pipeline for receiving and storing a two-phase expanded flow, the reservoir being designed to operate at a pressure of or below 1.5 bar, and the heat exchanger is designed so that the temperature of the high-density dense-phase flow is lower than cold expander outlet temperature

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

The above summary of the invention, as well as the following detailed description of exemplary embodiments, is best understood in conjunction with the attached drawings. To illustrate embodiments, the drawings show exemplary structures, but the invention is not limited to the described specific methods and tools.

In the drawings:

FIG. 1 is a flowchart of an exemplary method of using a liquid storage tank as an instant vapor separator, as well as extracting instant steam and boiling steam from the tank through a liquefier according to the present invention.

FIG. 2 is a flowchart of an alternative exemplary method including a different configuration of a fluidizer.

FIG. 3 is a flowchart of the previously described method with the same expander configuration as in FIG. 1, while the method includes a cold end separator and a subcooler, however, does not contain the extraction of instantly released steam and boiling off steam from the tank, and

FIG. 4 is a flowchart illustrating various ways of integrating the exemplary method of FIG. 1 with an air separation unit, wherein any other method according to the invention can be integrated with the air separation unit in a similar manner.

DETAILED DESCRIPTION

In FIG. 1 shows an exemplary system and method using a fluid storage tank 170 as an instant steam separator and extracting instant steam and boiling off steam from the fluid storage tank 170 through a liquefier 101. FIG. 1, a low pressure nitrogen feed stream 100 is described, combined with an instantaneous steam and boiling steam heated stream 102 to form a combined stream 104. The low pressure feed stream 100 may be nitrogen, or it may be another gas or a mixture of gases such as air, oxygen, argon, carbon monoxide, neon, ethylene, helium or, for example, hydrogen. Combined stream 104 is then compressed in feed compressor 106 to about 6 bar to form compressed stream 108. Compressed stream 108 is then cooled in cooler 110 to form chilled stream 112. Chilled stream 112 is then combined with recycle stream 114 to form stream 116. Stream 116 then compress in the recirculation compressor 118 to about 32 bar, which results in a compressed stream 120. Stream 120 is then cooled in cooler 122 to form stream 124. Stream 124 is then divided into streams 126 and 128.

Stream 126 (optionally) is cooled in heat exchanger 130 to form stream 132. Stream 132 is then expanded in a warm expander 134 to about 6 bar to form a warm expanded stream 136.

Stream 128 is then compressed in a warm compander compressor 138 to form a stream 140. Stream 140 is then cooled in a warm compander postcooler 142 to form a cooled stream 144. The cooled stream 144 is then again compressed in a cold compander compressor 146 to about 65 bar to form a compressed stream 148 The compressed stream 148 is then again cooled in a post-cooler 150 of a cold compander compressor to form a high pressure stream 152. This high pressure stream 152 is cooled in the heat exchanger 130 to an intermediate temperature of about 182 K, creating streams 154 and 156.

Stream 156 is expanded in the cold expander 158 to form an outlet stream 160. The outlet stream 160 is returned to the cold end of the heat exchanger 130, where it is heated and mixed with the exhaust stream 136 from the warm expander 134 to form a stream 162. Stream 162 is heated in the heat exchanger 130 to form a recirculation stream 114. The recycle stream 114 is then mixed with the compressed feed stream 112 and fed to the suction of the recirculation compressor 118.

Stream 154 is further cooled in heat exchanger 130 to form a high-density high-pressure stream 164. The dense-phase high-pressure stream 164 is diverted from the cold end of the heat exchanger 130 at a temperature of about 96 K, the pressure is reduced on one or more expansion devices 166 to form a stream 168, while stream 168 is fed directly to the liquid storage tank 170. As used herein, the term “deliver directly” means that the designated stream, after exiting one or more expansion devices 166, is supplied to the fluid storage tank 170 without using any additional apparatus that would change the composition, temperature, or pressure of the designated stream. Moreover, the term “directly connected” as used herein means that the first device or part of the apparatus is connected to the second device or part of the apparatus without any intermediate devices cations or parts of the apparatus, leading to a change in the composition, temperature or pressure of the stream passing, for example, through the first device to the second device.

Stream 168 is instantly vaporized in a liquid storage tank 170 to create substantially liquid with a certain amount of vapor. The liquid from stream 168 will be added to the liquid already present in the liquid storage tank 170, and the instantly released steam will be combined with the boiling off steam already present in the liquid storage tank 170. The combined steam stream 172, consisting of instantly released steam and boiling off steam, is diverted from the liquid storage tank 170 and, under normal operating conditions, is supplied to the heat exchanger 130 of the fluidizer 101 as stream 174. The stream 174 is heated in the heat exchanger 130 to form a heated stream 102 of instantly released steam and boiling off steam and mixed with the feed stream 100 of low pressure to form a combined stream 104 entering the make-up compressor 106 of the fluidizer 101.

If the liquefier 101 is not working, boiling vapors from the liquid storage tank 170 can be diverted from the liquid storage tank 170 as a combined vapor stream 172 and 176, the pressure of which is reduced on one or more expansion devices 178 to form a stream 180 discharged into atmosphere for controlling pressure in the liquid storage tank 170.

One of the significant advantages of this system is its simplified design. The heat exchanger 130, expanders 134 and 158 and the pipelines connected to them can be separately insulated, for example, with the use of insulation materials such as mineral wool, polyurethane foam, foam glass, cryogel, or with suitable alternative material or installed in small local thermal containers connected insulated piping. Reducing the size of thermal containers is especially important when it comes to planning delivery routes, because certain destinations can be difficult or impossible to reach with large pre-insulated cargoes (for example, thermal container loads).

In addition, contrary to traditional concepts, the extraction of boiling steam from the reservoir 170 for the accumulation of liquid surprisingly increases the overall efficiency of the liquefier 101 and the storage system by about 0.5-1.0% (depending on the relative sizes of the reservoir 170 for storing the liquid, liquefier 101 and reservoir insulation quality) compared with previous designs in which boiling-off gas was not extracted, since its cold is used to partially cool the product and reduce the required power of the liquefier 101, and not the release they are wasting it directly into the atmosphere. In addition, the required feed nitrogen flow is reduced (since it is previously released into the atmosphere), which can lead to the use of less ASU.

If the low pressure nitrogen feed stream 100 on the liquefier 101 has a sufficiently high pressure to supply the low pressure nitrogen feed stream 100 directly to the suction of the recirculation compressor 118, the feed compressor 106 may also be excluded, in which case the heated vapor stream 102 from the reservoir and the boiling point steam 102 may be vented to the atmosphere through a valve to easily control the pressure in the fluid storage tank 170.

With an amazing and unexpected result, the applicants have found that if the high-density flow of the high-pressure stream 164 is cooled below the temperature of the exhaust stream 160 by indirect heat exchange with the extracted combined steam stream 174 in the heat exchanger 130, a decrease in the pressure of the high-density phase flow 164 of the high pressure to the pressure of the exhaust stream 160 will not lead to the generation of significant quantities of instantly released vapors, thus, with the exception of additional separators and related components, the efficiency will liquefy Spruce 101 does not decrease. In fact, it will be understood by those skilled in the art that this exemplary embodiment eliminates the need for separators and subcoolers (e.g., separator 304 and subcooler 310 of FIG. 3) while maintaining a high level of efficiency. For example, while in traditional systems and methods two or more separators can be used to extract instantly emitting vapors at high and low pressures, the disclosed system and method achieve the same result without significant capital costs and significant transport planning while achieving equal or better efficiency .

In another embodiment, as shown in FIG. 2, a system and method similar to those shown in FIG. 1, however, this embodiment comprises another expander device. In this system and method, the stream 124 from the cooler 122 of the recirculation compressor is divided into two streams 226 and 228, which feed the ends of the compressor of the warm and cold companders 238 and 246 located in parallel. The respective outlet streams 240 and 248 from the warm and cold companders 238 and 246 are combined into stream 249 and cooled in cooler 250 before being fed to heat exchanger 130 as stream 252. Stream 252 is cooled to a first intermediate temperature in heat exchanger 130 before being separated into streams 232 and 253.

Stream 232 is expanded in a warm expander 234 to form a stream 236 and, in combination with a heating outlet stream 160, forms a stream 162 in an intermediate portion of the heat exchanger 130. Stream 253 is further cooled to a second intermediate temperature and again divided into streams 256 and 254. Stream 256 is expanded in cold expander 258 to form the exhaust stream 160. The exhaust stream 160 is then heated in the heat exchanger 130. The stream 254 is further cooled in the heat exchanger 130 to form a high-density high-pressure stream 164, which served in the reservoir 170 for storing liquid through the expansion device 166.

In FIG. 3 is a flow chart of a previously disclosed prior art method with the same expander configuration as shown in FIG. 1, but the method does not contain the extraction of instantly released vapors or boiling vapors from the tank. FIG. 3 is shown for illustrative purposes, as well as for use in comparison with the system and method of FIG. one.

As shown in FIG. 3, a cold end separator 304 and a subcooler 310 are integrated in the fluidizer 301, and there is no immediate recovery of steam or boiling off steam from the liquid storage tank 170. The pressure of the dense-phase high-pressure stream 164 from the cold end of the heat exchanger 130 is reduced on one or more expansion devices 300 and the resulting two-phase stream 302 is then fed to a separator 304 together with a cold expander outlet stream 160, which may contain some liquid. The steam stream 306 from the separator 304 is heated in the heat exchanger 130 to an intermediate temperature, where it is combined with the effluent stream 136 from the warm expander to form a stream 162. The liquid stream 308 from the separator 304 is supercooled in a subcooler 310 to about 78 K to form a stream 312. Part pressure 316, the supercooled liquid stream 312 is lowered on one or more expansion devices 318, and then it is evaporated in the supercooler 310 to form a vapor stream 320 and heated in a heat exchanger 130 to form a stream 102. The remainder 314, the supercooled liquid stream 312 is supplied to the liquid storage tank 170 through one or more expansion devices 166 to form a stream 168, while stream 168 is supplied to the liquid storage tank 170. The instantly released steam and boiling off steam from the liquid storage tank 170 is released into the atmosphere using stream 176 through an expansion device 178 to form a stream 180 (released into the atmosphere) to control the pressure in the tank.

In FIG. 4 is a flowchart illustrating several exemplary options for integrating a fluidizer system and the method of FIG. 1 with ASU or nitrogen generator. For example, the low pressure nitrogen feed stream 100 from the warm end of the ASU can be completely or partially replaced by one or more alternative feed streams 400, 404 or 408.

The high pressure nitrogen stream 400 from the warm end of the ASU or the nitrogen generator can also be mixed with stream 112 from the after-cooler 110 of the feed compressor to form stream 402, which can then be mixed with stream 114 to form stream 116 to be fed to recirculation compressor 118. As alternatively, stream 400 may be mixed downstream from the point where stream 114 is combined with stream 112, or between stages of feed compressor 106 or recirculation compressor 118.

The low pressure nitrogen stream 404 from the low pressure column or supercooler at the cold end of the ASU can be mixed with the low pressure return stream 174 from the liquid storage tank 170 to form a stream 406, which is then heated in the heat exchanger 130.

The high pressure cold nitrogen stream 408 from the ASU high pressure column or nitrogen generator or the single column nitrogen generator with a single column can be mixed with the exhaust stream 160 from the cold expander 158 to form a stream 410, which is then heated in the heat exchanger 130.

In addition, the separated portion of the high-density high-pressure flow stream 164 412 from the cold end of the fluidizer can be fed directly to the switchgear or nitrogen generator to provide cooling, while the remaining portion 414 can be fed to the fluid storage tank 170. As used herein, the term "separated portion" of a stream refers to a part having the same chemical composition as the stream from which it was taken. The separated portion of stream 412 may be fed, for example, to a high pressure (HP) column, low pressure (LP) column, subcooler or heat exchanger of an air separation unit (ASU).

EXAMPLE

Tables 1 and 2 show exemplary flow rates, temperatures, and pressures for the configurations and methods of FIG. 1 and 3. The configuration and method described in FIG. 1, the results are shown in Table 1, with 300 tons of liquid nitrogen produced per day in the liquid storage tank 170. The configuration and method required the consumption of approximately 5950 kW of electricity.

The configuration and method described in FIG. 3, the results are shown in Table 2, with 300 tons of liquid nitrogen produced per day in the liquid storage tank 170. This configuration and method required approximately 6,000 kW of electricity.

table 2 Flow one hundred 102 114 132 152 156 160 164 176 312 314 In the reserve voir Consumption (kmol / h) 460 97 2552 1238 1871 1369 1369 502 13 557 460 446 Temperature (K) 299 299 299 254 303 174 97 99 78 79 79 78 Pressure (bar (abs)) 1,03 1,03 6.00 30.05 64.80 64.60 6.20 64.60 1.10 6.00 6.00 1.10

It is important to note that the exemplary method illustrated in FIG. 1 and in Table 1, gives the same net amount (446 kmol / h) of liquid nitrogen in the liquid storage tank, but uses 0.8% less energy than the previously disclosed method shown in FIG. 3 and in Table 2, it has a 3% lower consumption (stream 100) due to the extraction of instantly released steam and boiling off steam from the liquid storage tank (stream 174), as well as eliminating the loss of boiling off steam into the atmosphere from the tank (stream 176) and it provides significant savings in capital costs by eliminating the first separator, second separator or subcooler and associated valves, controls and an insulating sheath. Since the cold part of the liquefier contains essentially only a heat exchanger and the associated piping, the equipment of the liquefier can be isolated directly, with a separate thermal container design necessary to accommodate and isolate the first separator, second separator or supercooler, as well as valves and bodies associated with them control can be eliminated, which significantly reduces the size of the thermal container. Reducing the size of the thermal container is especially important when it comes to planning transportation routes, because certain destinations can be difficult or even impossible to reach with large pre-insulated cargoes (for example, thermal container loads).

Although the objects of the present invention are described with reference to preferred embodiments of various figures, it should be understood that other similar embodiments may be used, or changes and additions may be made to the described embodiment to perform the same function within the framework of the present invention. Thus, the claimed invention should not be limited to any one embodiment, but should be considered within the essence and scope of the attached claims.

Claims (15)

1. A method of liquefying gas, comprising stages in which:
- introducing the feed stream into a fluidizing agent containing at least a warm expander and a cold expander,
- compress the feed stream in the liquefier to a pressure above the critical pressure and cool the compressed feed stream to a temperature below the critical temperature to form a dense-phase high-pressure stream,
- the dense-phase high-pressure stream is withdrawn from the liquefier and the pressure of the dense-phase high-pressure stream is reduced in the expansion device to form the resulting two-phase stream, and then the resulting two-phase stream is directly fed to the storage tank, and
- combine the instantly isolated part of the resulting two-phase stream with boiling off liquid vapor in the storage tank to form a combined vapor stream, the temperature of the high-density dense-phase stream being lower than the temperature of the outlet stream of the cold expander. 2. The method according to claim 1, in which the dense-phase high-pressure stream is cooled to a temperature lower than the temperature of the outlet stream of the cold expander, through indirect heat exchange with the combined stream. 3. The method according to claim 1, further comprising the step of heating at least a portion of the combined steam stream to ambient temperature. 4. The method according to claim 3, further comprising the step of mixing the heated combined steam stream with the feed stream for recirculation. 5. The method according to claim 3, further comprising the step of releasing the heated combined vapor stream into the atmosphere to control the pressure in the storage tank, the pressure in the storage tank being preferably less than 1.5 bar. 6. The method according to claim 1, additionally containing a stage in which at least part of the combined steam stream is withdrawn from the storage tank, the pressure of the combined steam stream is reduced in one or more expansion devices to form a combined low pressure steam stream, and the combined a low pressure steam stream to atmosphere to control pressure in the storage tank, the pressure in the storage tank being preferably less than 1.5 bar. 7. The method according to claim 1, wherein the feed stream is a low pressure nitrogen feed stream from the warm end of the air separation unit. 8. The method according to claim 1, further comprising the step of mixing the low pressure nitrogen stream from the low pressure column or supercooler of the air separation unit with the combined vapor stream from the storage tank before heating. 9. The method according to claim 1, additionally containing a stage in which the separated part of the high-pressure densely-phase fluid is taken from the liquefier, the separated part of the high-pressure dense-phase fluid is fed directly to the air separation unit or nitrogen generator to provide cooling. 10. The method according to claim 9, in which the pressure of the separated part of the dense phase high-pressure fluid is reduced and fed to the high-pressure column (HP), low-pressure column (LP), subcooler or main heat exchanger of the air separation unit. 11. An atmospheric gas liquefaction system comprising:
- a first pipe for receiving a feed stream,
- a fluidizer connected in fluid to the first conduit for compressing and cooling the feed stream to form a dense phase high-pressure fluid stream, the fluidizer containing at least a warm expander, a cold expander, a compressor for compressing the feed stream to a pressure exceeding it critical pressure, as well as a heat exchanger for cooling the compressed feed stream to a temperature below the critical temperature,
- a second pipeline fluidly coupled to a fluidizer for receiving a dense-phase high-pressure flow from the fluidizer,
- a first expansion device fluidly coupled to a second pipe to reduce the pressure of the high-density dense-phase flow to form the resulting two-phase flow,
a third pipeline fluidly coupled to a first expansion device for receiving a two-phase expanded flow, and
- a storage tank fluidly connected to a third pipe for receiving and storing a two-phase expanded flow, wherein the storage tank is configured to operate at a pressure of or below 1.5 bar, and the heat exchanger is configured so that the temperature of the dense-phase flow high pressure lower than the temperature of the outlet stream of the cold expander. 12. The system of claim 11, wherein the storage tank is directly connected to the third pipeline, the first expansion device being directly connected to the second pipeline. 13. The system of claim 11, further comprising a fourth conduit fluidly coupled to the storage tank for receiving a combined steam stream comprising an instantly released portion of the resulting two-phase stream and a portion of boiling off steam from the liquid in the storage tank. 14. The system of claim 13, wherein the fourth conduit is fluidly coupled to the heat exchanger and the first conduit. 15. The system of claim 13, further comprising a second expansion device fluidly coupled to the fourth conduit to reduce the pressure of the combined steam stream to control pressure in the storage tank.

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