Patent Application
20170010041
Liquefied natural gas (“LNG”) has allowed the supply of natural gas from locations with an abundant supply of natural gas to distant locations with a strong demand for natural gas. The conventional LNG cycle includes: (a) initial treatment of the natural gas resource to remove contaminants such as water, sulfur compounds, and carbon dioxide; (b) separation of some heavier hydrocarbon gases, such as propane, butane, and pentane, from the natural gas, where the separation can occur by a variety of possible methods including self-refrigeration, external refrigeration, or lean oil, etc.; (c) refrigeration of the natural gas to form liquefied natural gas at near atmospheric pressure and about −160° C.; (d) transport of the LNG product in ships or tankers to a market location; and (e) re-pressurization and re-gasification of the LNG at a regasification plant to a pressure at which natural gas may be distributed to natural gas customers. Step (c) of the conventional LNG cycle typically uses external refrigeration which requires the use of large refrigeration compressors often powered by large gas turbine drivers that can produce greenhouse gas emissions. Thus, a large capital investment is typically needed to put in place the extensive infrastructure needed for the liquefaction plant. Step (e) of the LNG cycle generally includes re-pressurizing the LNG to the required pressure using cryogenic pumps and then re-gasifying the LNG to pressurized natural gas by exchanging heat through an intermediate fluid, such as seawater, or by combusting a portion of the natural gas to vaporize the LNG.
A cold refrigerant produced at a different location, such as liquefied nitrogen gas (“LIN”), can be used to liquefy natural gas. For example, U.S. Pat. No. 3,400,547 describes shipping liquid nitrogen or liquid air from a market place to a field site where it is used to liquefy natural gas. The LNG is shipped back to the market site in the tanks of the same cryogenic carrier used to transport the liquefied nitrogen or air to the field site. Regasification of the LNG is carried out at the market site, where the excess cold from the re-gasification process is used to liquefy nitrogen or air for shipping to the field site.
However, since the natural gas from the regasification of LNG must be at a higher pressures (e.g., greater than 800 psi) for introduction into the gas sales pipeline, the total energy needed for both the production of LIN and the re-pressurization of natural gas can be significantly greater than the energy needed to produce LNG using conventional processes. Therefore, there is a need to develop more energy efficient methods to produce LIN and high pressure natural gas from the regasification of LNG.
Furthermore, the process of U.S. Pat. No. 3,400,547 requires the integration of the complete LNG value chain. That is, there must be integration of the production of LNG using LIN as the cold refrigerant, the shipping of LIN to the natural gas resource location, the shipping of LNG to regasification locations, and the production of LIN using the available exergy from the regasification of LNG. This value chain is further described in U.S. Patent Application Publication Nos. 2010/0319361 and 2010/0251763.
The production of LNG at the gas resource site using LIN as the sole refrigerant may require a LIN to LNG ratio of greater than 1:1. For this reason, the production of LIN at the regasification site favors a greater than 1:1 LIN to LNG ratio in order to ensure that only the LNG produced using the LIN is then required to liquefy the needed amount of nitrogen. The matching of the LIN to LNG ratio at both the LNG plant and the regasification plant allows for an easier integration of the LNG value chain since LNG from additional production sources is not needed.
GB Patent Application Publication No. 2,333,148 describes a process where the vaporization of LNG is used to produce LIN, where the LIN to LNG ratio that is used is greater than 1.2:1. In GB Publication No. 2,333,148 the LNG is vaporized close to atmospheric pressure. Therefore, since the standardized pressure at which LNG must be when entering the gas sales pipeline is greater than 800 psi, a significant amount of energy is required to compress the natural gas to pipeline pressure. As such, there is a need for a method which allows pumping the LNG to higher pressures prior to vaporization in order to minimize the required amount of natural gas compression.
GB Patent 1,376,678 and U.S. Pat. Nos. 5,139,547 and 5,141,543 describe methods where LNG is first pressurized to the pipeline transport pressure prior to vaporization of the LNG. In these disclosures, the vaporizing LNG is used to condense the nitrogen gas and is used as the interstage coolant for the multistage compression of the nitrogen gas to a pressure of at least 350 psi. The interstage cooling of the nitrogen gas using the vaporizing and warming of the natural gas allows for cold compression of the nitrogen gas which significantly reduces its energy of compression. However, in these disclosures a LIN to LNG ratio of less than 0.5:1 is used to produce the LIN and high pressure natural gas. This low LIN to LNG ratio does not allow for point-to-point integration of the regasification plant with the LNG plant, since a LIN to LNG ratio of at least 1:1 is typically required to produce LNG using LIN as the sole refrigerant.
U.S. Patent Application Publication No. 2010/0319361 describes a method where LNG from multiple production sources are used to produce the LIN needed for LNG production at one production site. However, this multi-source LNG value chain arrangement significantly complicates the LNG value chain.
Therefore, there remains a need to develop an energy efficient method for producing LIN and high pressure natural gas from the regasification of LNG. There is further a need for an integrated method that is able to utilize a LIN to LNG ratio that is greater than 1:1, or more preferably greater than 1.2:1.
Other background references include GB Patent No. 1596330, GB Patent No. 2172388, U.S. Pat. No. 3,878,689, U.S. Pat. No. 5,950,453, U.S. Pat. No. 7,143,606, and PCT Publication No. WO 2014/078092.
Provided herein are methods for producing a liquefied gas stream, such as a liquefied nitrogen stream. For example, the method may comprise a method for producing a liquefied nitrogen gas (LIN) stream at a liquid natural gas (LNG) regasification facility comprising. In some embodiments, the method may comprise (a) providing a nitrogen gas stream; (b) providing at least two LNG streams where the pressures of each LNG stream are independent and different from each other; (c) liquefying the nitrogen gas stream by indirect heat exchange of the nitrogen gas stream with the LNG streams in at least one heat exchanger; (d) vaporizing at least a portion of the two LNG streams to produce at least two natural gas streams; and (e) compressing at least one of the two natural gas streams to form compressed natural gas.
Various specific embodiments and versions of the present invention will now be described, including preferred embodiments and definitions that are adopted herein. While the following detailed description gives specific preferred embodiments, those skilled in the art will appreciate that these embodiments are exemplary only, and that the present invention can be practiced in other ways. Any reference to the “invention” may refer to one or more, but not necessarily all, of the embodiments defined by the claims. The use of headings is for purposes of convenience only and does not limit the scope of the present invention.
All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
As used herein, “auto-refrigeration” refers to a process whereby a fluid is cooled via a reduction in pressure. In the case of liquids, auto-refrigeration refers to the cooling of the liquid by evaporation, which corresponds to a reduction in pressure. More specifically, a portion of the liquid is flashed into vapor as it undergoes a reduction in pressure while passing through a throttling device. As a result, both the vapor and the residual liquid are cooled to the saturation temperature of the liquid at the reduced pressure. For example, auto-refrigeration of a natural gas may be performed by maintaining the natural gas at its boiling point so that the natural gas is cooled as heat is lost during boil off. This process may also be referred to as a “flash evaporation.”
As used herein, the term “compressor” means a machine that increases the pressure of a gas by the application of work. A “compressor” or “refrigerant compressor” includes any unit, device, or apparatus able to increase the pressure of a gas stream. This includes compressors having a single compression process or step, or compressors having multi-stage compressions or steps, or more particularly multi-stage compressors within a single casing or shell. Evaporated streams to be compressed can be provided to a compressor at different pressures. Some stages or steps of a cooling process may involve two or more compressors in parallel, series, or both. The present invention is not limited by the type or arrangement or layout of the compressor or compressors, particularly in any refrigerant circuit.
As used herein, “cooling” broadly refers to lowering and/or dropping a temperature and/or internal energy of a substance, such as by any suitable amount. Cooling may include a temperature drop of at least about 1° C., at least about 5° C., at least about 10° C., at least about 15° C., at least about 25° C., at least about 35° C., or least about 50° C., or at least about 75° C., or at least about 85° C., or at least about 95° C., or at least about 100° C. The cooling may use any suitable heat sink, such as steam generation, hot water heating, cooling water, air, refrigerant, other process streams (integration), and combinations thereof. One or more sources of cooling may be combined and/or cascaded to reach a desired outlet temperature. The cooling step may use a cooling unit with any suitable device and/or equipment. According to some embodiments, cooling may include indirect heat exchange, such as with one or more heat exchangers. In the alternative, the cooling may use evaporative (heat of vaporization) cooling and/or direct heat exchange, such as a liquid sprayed directly into a process stream.
As used herein, the term “expansion device” refers to one or more devices suitable for reducing the pressure of a fluid in a line (for example, a liquid stream, a vapor stream, or a multiphase stream containing both liquid and vapor). Unless a particular type of expansion device is specifically stated, the expansion device may be (1) at least partially by isenthalpic means, or (2) may be at least partially by isentropic means, or (3) may be a combination of both isentropic means and isenthalpic means. Suitable devices for isenthalpic expansion of natural gas are known in the art and generally include, but are not limited to, manually or automatically, actuated throttling devices such as, for example, valves, control valves, Joule-Thomson (J-T) valves, or venturi devices. Suitable devices for isentropic expansion of natural gas are known in the art and generally include equipment such as expanders or turbo expanders that extract or derive work from such expansion. Suitable devices for isentropic expansion of liquid streams are known in the art and generally include equipment such as expanders, hydraulic expanders, liquid turbines, or turbo expanders that extract or derive work from such expansion. An example of a combination of both isentropic means and isenthalpic means may be a Joule-Thomson valve and a turbo expander in parallel, which provides the capability of using either alone or using both the J-T valve and the turbo expander simultaneously. Isenthalpic or isentropic expansion can be conducted in the all-liquid phase, all-vapor phase, or mixed phases, and can be conducted to facilitate a phase change from a vapor stream or liquid stream to a multiphase stream (a stream having both vapor and liquid phases) or to a single-phase stream different from its initial phase. In the description of the drawings herein, the reference to more than one expansion device in any drawing does not necessarily mean that each expansion device is the same type or size.
The term “gas” is used interchangeably with “vapor,” and is defined as a substance or mixture of substances in the gaseous state as distinguished from the liquid or solid state. Likewise, the term “liquid” means a substance or mixture of substances in the liquid state as distinguished from the gas or solid state.
A “heat exchanger” broadly means any device capable of transferring heat energy or cold energy from one media to another media, such as between at least two distinct fluids . Heat exchangers include “direct heat exchangers” and “indirect heat exchangers.” Thus, a heat exchanger may be of any suitable design, such as a co-current or counter-current heat exchanger, an indirect heat exchanger (e.g. a spiral wound heat exchanger or a plate-fin heat exchanger such as a brazed aluminum plate fin type), direct contact heat exchanger, shell-and-tube heat exchanger, spiral, hairpin, core, core-and-kettle, double-pipe or any other type of known heat exchanger. “Heat exchanger” may also refer to any column, tower, unit or other arrangement adapted to allow the passage of one or more streams there through, and to affect direct or indirect heat exchange between one or more lines of refrigerant, and one or more feed streams.
As used herein, the term “indirect heat exchange” means the bringing of two fluids into heat exchange relation without any physical contact or intermixing of the fluids with each other. Core-in-kettle heat exchangers and brazed aluminum plate-fin heat exchangers are examples of equipment that facilitate indirect heat exchange.
As used herein, the term “natural gas” refers to a multi-component gas obtained from a crude oil well (associated gas) or from a subterranean gas-bearing formation (non-associated gas). The composition and pressure of natural gas can vary significantly. A typical natural gas stream contains methane (C1) as a significant component. The natural gas stream may also contain ethane (C2), higher molecular weight hydrocarbons, and one or more acid gases. The natural gas may also contain minor amounts of contaminants such as water, nitrogen, iron sulfide, wax, and crude oil.
Described herein are systems and processes where LIN and natural gas that is at sufficiently high pressure such that it is suitable for pipeline transport (e.g., 800 psia or greater) are produced by indirect heat exchange of at least one nitrogen gas stream with at least two LNG streams within at least one heat exchanger where the LNG streams are at different pressures. In some embodiments, the LIN and high pressure natural gas are produced by the indirect heat exchange of at least one nitrogen gas stream with at least three, or at least four, LNG streams in a multi-stream heat exchanger where each of the LNG streams are at a different pressure from the other LNG streams.
For example, a single LNG stream may be pressurized, for example by using one or more pumps, to an intermediate pressure. The intermediate pressure LNG stream is then split into at least two LNG streams. At least one of the LNG streams is let down in pressure, for example using one or more expansion devices, such as valves, hydraulic turbines, or other devices as known in the art. The reduced pressure LNG stream(s) are then conveyed to at least one heat exchanger. At least one of the LNG streams that is at the intermediate pressure is additionally pressurized using one or more pumps to a pressure higher than the intermediate pressure, such as a pressure equal to or higher than the natural gas sales pipeline pressure. The additionally pressurized LNG stream(s) are then piped to the at least one heat exchanger. The at least two LNG streams undergo indirect heat exchange with at least one nitrogen gas stream within the at least one heat exchanger, whereby the nitrogen gas stream is liquefied forming LIN.
In a preferred embodiment, a single LNG stream is introduced to the system. In some embodiments, the LNG stream that enters the system is at a pressure of greater than 14 psia, or greater than 15 psia. The LNG stream that enters the system may be at a pressure of less than 65 psia, or less than 55 psia, or less than 45 psia, or less than 35 psia, or less than 25 psia, or less than 20 psia. For example, in some embodiments, the LNG stream that enters the system may be at a pressure of from about 14 to about 25 psia, or from about 15 to 25 psia, or at a pressure typical for the transport of LNG, such as about 17 psia.
The LNG stream is then pressurized using one or more pumps to an intermediate pressure. The intermediate pressure may be a pressure greater than 50 psia, or greater than 60 psia, or greater than 70 psia, or greater than 75 psia. The intermediate pressure may be less than 250 psia, or less than 200 psia, or less than 175 psia, or less than 150 psia. In some embodiments, the intermediate pressurized LNG stream may be a pressure from 50 to 200 psia, or from 70 to 150 psia, or from 75 to 100 psia.
The pressurized LNG stream is then split into two or more streams. For example, the pressurized LNG stream may be split into three or four LNG streams. All but one of the pressurized LNG streams are then reduced in pressure using one or more expansion devices, such as valves, hydraulic turbines, or a combination of devices, where each of the reduced pressures is different from the other reduced pressures. Thus, in an embodiment where the pressurized LNG stream was split into three LNG streams, two of the LNG streams are reduced to different pressures using one or more valves and one LNG stream is not reduced in pressure or is kept at the intermediate pressure. Likewise, in an embodiment where the pressurized LNG stream was split into four LNG streams, three of the LNG streams would be reduced in pressure to different pressures using one or more valves and one LNG stream is not reduced in pressure or is kept at the intermediate pressure. The LNG stream that is not reduced in pressure may remain at the intermediate pressure, or may be pressurized using one or more pumps to a pressure equal to or higher than the natural gas sales pipeline pressure, such as greater than 800 psia, or greater than 1200 psia.
In an embodiment, where the pressurized LNG stream was split into at least four streams, the pressures of each stream are different from one another. For example, the pressure of the first LNG stream may be reduced to a value from 10 psia to 35 pisa, or from 15 psia to 30 psia, or from 20 pisa to 25 psia. The pressure of the second LNG stream may be between 30 to 60 psia, or from 35 to 55 psia, or from 40 to 50 psia. The pressure of the third LNG stream may be between 50 psia and the intermediate pressure, or from 50 to 100 psia, or from 60 to 90 psia, or from 65 to 80 psia. The fourth LNG stream may remain at the intermediate pressure or may be pressurized using one or more pumps to a pressure equal to or higher than the natural gas sales pipeline pressure, such as greater than 800 psia, or greater than 900 psia, or greater than 1000 psia, or greater than 1100 psia, or greater than 1200 psia.
The reduced pressure LNG streams and the additionally pressurized LNG stream are all piped to at least one heat exchanger, and in preferred embodiments, are piped to a single multi-stream cryogenic heat exchanger. The LNG streams undergo indirect heat exchange with a nitrogen gas stream that is also piped to the heat exchanger. Suitable heat exchangers include, but are not limited to, cryogenic heat exchangers, which may include brazed aluminum type heat exchangers, spiral wound type heat exchanger, and printed circuit type heat exchangers.
As it is known in the art, a suitable heat exchanger will allow for indirect heat exchange between the LNG streams and the nitrogen gas stream while preventing or minimizing indirect heat exchange between the LNG streams. The nitrogen gas stream is at least partially liquefied within the heat exchange such that less than 20 mol %, or less than 15 mol %, or less than 10 mol %, or less than 7 mol %, or less than 5 mol %, or less than 3 mol %, or less than 2 mol %, or less than 1 mol % of the stream remains in the vapor phase.
The pressure of the nitrogen gas stream that is piped to the heat exchanger may be greater than 200 psia, or greater than the critical point pressure of the nitrogen gas stream, or greater than 700 psia, or greater than 800 psia, or greater than 900 psia, or greater than 1000 psia, or greater than 1100 psia, or greater than 1200 psia.
The composition of the nitrogen gas stream may be at least 70% nitrogen, or at least 75% nitrogen, or at least 80% nitrogen, or at least 85% nitrogen, or at least 90% nitrogen, or at least 95% nitrogen. The nitrogen gas stream may comprise other gaseous impurities, such as other components found in air, such as oxygen, argon and carbon dioxide.
The pressures, flow rates and heat exchanger outlet temperatures of the LNG streams entering the multi-stream heat exchanger may be chosen to allow for close matching of the nitrogen gas stream's cooling curve with the warming curves or the composite warming curve of the LNG streams. In some embodiments, it is preferred that the heat exchanger outlet temperatures of the additionally pressurized LNG stream be greater than −150° C., or greater than −140° C., or greater than −130° C., or greater than −120° C., or greater than −115° C., or greater than −110° C., or greater than −105° C., or greater than −100° C., or greater than −75° C., or greater than −50° C., or greater than 0° C., or greater than 20° C. In some embodiments, the heat exchanger outlet temperature of the additionally pressurized LNG stream may be from −150° C. to 20° C., or from −140° C. to 0° C., or from −130° C. to −50° C., or from −120° C. to −75° C. The additionally pressurized LNG streams once vaporized may be at a sufficient pressure to enter the gas sale pipeline or be utilized within the regasification plant without requiring additional compression. It is preferred that heat exchanger outlet temperatures of the reduced pressure LNG streams be less than −50° C., or less than −75° C., or less than −100° C., or less than −105° C., or less than −110° C., or less than −115° C. In some embodiments, the heat exchanger outlet temperature of the reduced pressure LNG streams is from −50° C. to −150° C., or from −75° C. to −125° C., or from −80° C. to −100° C. The reduced pressure LNG streams may be fully or partially vaporized within the at least one heat exchanger.
After exiting the at least one heat exchanger, the reduced pressure LNG streams may be separated into their liquid and gas components. The liquid component of the reduced pressure LNG streams may be pumped to pressure greater than or equal to the pressure of the additionally pressurized LNG streams and then recycled back to the at least one heat exchanger. The gas component of the reduced pressure LNG streams may be pressurized in compressors to pressures suitable to introduce the compressed gases to the sale gas pipeline or to pressures suitable for use of the compressed gases within the regasification plant. It is often preferred that compressed gases be mixed with some or all the of the vaporized additionally pressurized LNG streams prior to distributing the gases. In a preferred embodiment, the heat exchanger outlet temperature of the reduced pressure LNG streams are sufficiently low to allow for cold compression of the gases to pressures suitable for use without requiring any intercooling of the gases during compression.
In some embodiments, all or a portion of the additionally pressurized LNG streams, after flowing through the at least one heat exchanger, may be piped to at least one second heat exchanger. Alternatively, all or a portion of the additionally pressurized LNG streams may bypass the at least one heat exchanger and may be piped directly to the at least one second heat exchanger. The at least one second heat exchanger can be used for indirect heat exchange of the additionally pressurized LNG streams with the at least one nitrogen gas stream prior to compression of the nitrogen gas stream. The cooling of the at least one nitrogen gas stream with the additionally pressurized LNG streams may occur before one or more of the compression stages of the at least one nitrogen gas stream. The cooling of the at least one nitrogen gas stream with the additionally pressurized LNG streams may occur after intercooling and/or aftercooling of the nitrogen gas stream. As it is known in the art, intercooling and aftercooling of gases may involve the removal of heat from gases after compression by indirect heat exchange with the environment. It is common for the heat to be removed using air or water from the environment. The cooling of the at least one nitrogen gas stream with all or a portion of the additionally pressurized LNG streams prior to compression of the at least one nitrogen gas stream may allow for compression of the at least one nitrogen gas at suction temperatures less than 0° C., or less than −10° C., or less than −20° C., or less than −30° C., or less than −40° C., or less than −50° C. The cold compression of the at least one nitrogen gas stream significantly reduces the energy of compression of said gas.
The process described herein has the advantage of liquefying an at least one nitrogen gas stream into an at least one LIN stream by utilizing at least two LNG streams where the required compression of the vaporized LNG streams may be significantly less than prior art. For example, GB Patent Application 2,333,148 discloses a process where the vaporization of LNG is used to produce LIN. The method of GB Patent Application 2,333,148 has the advantage that a LIN to LNG ratio of greater than 1.2:1 is used to produce the LIN. However, GB Patent Application 2,333,148 has the disadvantage that the single LNG stream is vaporized close to atmospheric pressure. Since natural gas must be admitted to the gas sales pipeline at a high pressure (greater than 800 psi), a significant amount of compression is required to pressurize the natural gas to the pipeline pressure. The compression of the close to atmospheric pressure natural gas stream would mostly likely involve the use of multiple compression stages with a significant amount of intercooling and aftercooling of the natural gas stream occurring after each compression stage. The compression of this natural gas stream would require a significant amount of capital investment in compressors and coolers within the regasification plant. It would also be an energy intensive process that would most likely eliminate any thermodynamic advantage in utilizing the available exergy in regasifying the LNG to produce the LIN. In contrast to GB Patent Application Publication No. 2,333,148, the system and method described herein only requires compression of a fraction of the total LNG flow. In some embodiments of this invention, the reduced pressure LNG streams account for no more than 20% of the total LNG flow, or less than 15% of the total LNG flow, or less than 10% of the total LNG flow. Another advantage of the present system and method is that the compression of the reduced pressure LNG stream gases may occur at temperatures less than −50° C. The cold compression of the reduced pressure LNG stream gases significantly reduces the amount of energy needed for compressing the gases.
For example, in embodiments where the LNG stream is split into four streams, the three reduced pressure streams may account for less than 20%, or less than 17%, or less than 15%, or less than 12%, or less than 10%, of the total LNG flow. In some embodiments, the lowest pressure LNG stream may account for less than 5%, or less than 4%, or less than 3%, or less than 2%, or less than 1% of the total LNG flow. In some embodiments, the second lowest pressure LNG stream may account for less than 7%, or less than 6%, or less than 5%, or less than 4%, or less than 3%, or less than 2%, of the total LNG flow. In some embodiments, the third lowest pressure LNG stream may account for less than 10%, or less than 9%, or less than 8%, or less than 7%, or less than 6%, of the total LNG flow. In some embodiments, the highest pressure LNG stream may account for greater than 80%, or greater than 82%, or greater than 84%, or greater than 86%, or greater than 88%, or greater than 90%, of the total LNG flow.
This present system and method also has the additional advantage of liquefying an at least one nitrogen gas stream to form at least one LIN stream by utilizing an at least two LNG streams where the total LIN to LNG ratio is greater than 1:1. For example, GB Patent 1,376,678 and U.S. Pat. Nos. 5,139,547 and 5,141,543 disclose methods where the LNG is first pressurized to the pipeline transport pressure prior to vaporization of the LNG. In these references, the vaporizing LNG is used to condense the nitrogen gas and used as the coolant within the intercoolers between the multistage compression of the of the nitrogen gas to a pressure at least greater than 350 psi. The intercooling of the nitrogen gas using the vaporizing and warming natural gas allows for cold compression of the nitrogen gas which significantly reduces its energy of compression. The methods and processes described in all three of these references have the disadvantage that a LIN to LNG ratio of less 0.5:1 is used to produce the LIN and high pressure natural gas. This low LIN to LNG ratio does not allow for point-to-point integration of the regasification plant with a LNG plant since a LIN to LNG ratio of 1:1 or greater is typically required to produce LNG using LIN as the sole refrigerant. In the regasification plants described in GB Patent 1,376,678 and U.S. Pat. Nos. 5,139,547 and 5,141,543, LNG sourced from conventional LNG plants would need to be used in addition to the LNG produced from the LIN. In contrast, the system and method described herein, has the advantage that it allows for the energy efficient production of LIN using a LIN to LNG ratio of greater than 1:1. The matching of the LIN to LNG ratio at both the LNG plant and the regasification plant allows for an easier integration of the LNG value chain since LNG from conventional production sources is not needed. Additionally, certain embodiments of this system and method allow for one or more of the vaporizing LNG streams to be used to cool the nitrogen gas stream prior to compression of the nitrogen gas stream in order to improve process efficiency.
Having described various aspects of the systems and methods herein, further specific embodiments of the invention include those set forth in the following paragraphs as described with reference to the Figures. While some features are described with particular reference to only one Figure (such as
The nitrogen gas stream 111 may be conveyed or transported, for example be piped, to a compressor 120. The compressor 120 increases the pressure of the nitrogen gas streams to a pressures greater than 200 psia, or greater than 300 psia, or greater than 400 psia, or greater than 500 psia, or greater than 600 psia, or greater than 700 psia, or greater than 800 psia, or greater than 900 psia, or greater than 1000 psi. In some embodiments, the compressor 120 increases the pressure of the nitrogen gas stream to a pressure greater than the critical point pressure of the nitrogen gas stream. The compression of the nitrogen gas stream may occur in a single stage or in multiple stages of compression. In some embodiments, more than one compressor may be used, where the compressors are parallel, in series, or both. The high pressure nitrogen gas stream 112 may then be split into two streams 112a and 112b which are then piped to heat exchangers 121 and 122 where they are liquefied by heat exchange with vaporizing LNG streams to form high pressure LIN stream 113.
With reference to
The high pressure LIN streams 113a and 113b exiting the heat exchangers 121 and 122 may be combined into one stream 113 and may then be further cooled in a heat exchanger 127. In some embodiments, the high pressure LIN streams 113a and 113b are each introduced individually into the heat exchanger 127, while in other embodiments, the high pressure LIN streams are combined as shown in
Like in
The additionally pressurized LNG stream 310 exits the multi-stream cryogenic heat exchanger 333 as stream 335 which may then be piped to at least one or two more heat exchangers 336 and 337 to further cool the nitrogen gas stream at the warmer end of the nitrogen gas stream cooling curve. The pressures, flow rates and heat exchanger outlet temperatures of the additionally pressurized LNG stream may be chosen to allow for close matching of the temperature versus heat transfer curves within the heat exchangers. It is preferred that the temperature of the vaporized, additionally pressurized LNG stream 315 be greater than 0° C., or greater than 10° C., or greater than 15° C., or greater than 20° C.
The LIN stream 321 shown in
A simulation was conducted to model the cooling curves exhibited by the nitrogen gas stream and LNG streams of a system configured as in
Certain embodiments and features have been described using a set of numerical upper limits and a set of numerical lower limits. It should be appreciated that ranges from any lower limit to any upper limit are contemplated unless otherwise indicated. All numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
All patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
This application claims the priority benefit of U.S. Patent Application 62/191,130 filed Jul. 10, 2015 entitled SYSTEM AND METHODS FOR THE PRODUCTION OF LIQUEFIED NITROGEN GAS USING LIQUEFIED NATURAL GAS, the entirety of which is incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 62191130 | Jul 2015 | US |
