BR112015002328B1 - Method of removing heavy hydrocarbons from a natural gas feed stream, and equipment for removing heavy hydrocarbons from a natural gas feed stream - Google Patents

Abstract

method of removing heavy hydrocarbons from a natural gas feed stream, and equipment for removing heavy hydrocarbons from a natural gas feed stream. a method and equipment for removing heavy hydrocarbons from a natural gas feed stream, the method comprising using first and second hydrocarbon removal systems in series such that the first system processes the natural gas feed stream to produce a heavy hydrocarbon-depleted natural gas stream and the second system processes at least a portion of the heavy hydrocarbon-depleted natural gas stream of the first system to produce the heavy hydrocarbon-depleted natural gas stream, wherein one of said systems is an adsorption system comprising one or more adsorbent beds for adsorbing and thereby removing heavy hydrocarbons from a natural gas containing heavy hydrocarbons, and the other of said systems is a gas-liquid separation system for separating a natural gas containing hydrocarbons heavy hydrocarbons-depleted natural gas vapor and a liquid rich in heavy hydrocarbons.

Description

BASICS OF THE INVENTION

[0001] The present invention relates to a method and equipment for removing heavy hydrocarbons (i.e., aliphatic hydrocarbons with six or more carbon atoms in total and aromatic hydrocarbons - also referred to herein as C6+ and aromatic hydrocarbons, respectively) from from a stream of natural gas. In certain preferred embodiments, it relates to a method and equipment for removing heavy hydrocarbons from a natural gas stream and liquefying a natural gas stream. The natural gas stream may be a stream that is already lean in aliphatic hydrocarbons with 3 to 5 carbon atoms in total (also referred to herein as C3-C5 hydrocarbons), and/or a stream that is already lean in aliphatic hydrocarbons having 2 to 5 carbon atoms in total (also referred to herein as C2-C5 hydrocarbons).

[0002] It is important to remove heavy hydrocarbons from a natural gas stream before liquefying the natural gas stream, as otherwise heavy hydrocarbons may freeze in the liquefied natural gas (LNG) stream. It is also known that heavy hydrocarbon components contained in natural gas feed streams can be removed using temperature swing adsorption (AOT) or using a scrubbing column.

[0003] As is well known in the art, a scrubbing column is a type of separation device for removing less volatile components from a feed stream, to produce a gaseous stream depleted of said less volatile components. The feed stream is introduced (as a gaseous stream or as a two-stage gas-liquid type stream) into the wash column, where it is brought into contact with a liquid reflux stream. The reflux current is introduced into the column at a location that is above the position at which the supply current is introduced, such that the descending stream of liquid comes into contact in countercurrent with the ascending vapor current originating from the supply stream, "purifying " thereby creating said vapor stream (i.e., removing at least part of the less volatile components of the vapor stream). Typically, the wash column contains one or more separation stages positioned below the location at which the reflux stream is introduced and above the position at which the feed stream is introduced, the column consisting of trays, packing, or some other another form of insertion that acts to increase the amount and/or duration of contact between the ascending vapor and the descending reflux currents, thus increasing the mass transfer between the currents.

[0004] In the case of treating a natural gas stream, a scrubbing column may be effective in removing all heavy hydrocarbon components from the stream, but it must be operated at pressures lower than the critical pressure of the mixture in order to to achieve the separation of gas-liquid phases. The operating pressure of the column is lower than the ideal natural gas liquefaction pressure, which leads to lower energy efficiency in the liquefaction process. Furthermore, stable operation of the washing column requires sufficient flow ratio between liquid (i.e. reflux) and vapor in order to avoid drying out of the column. Reflux to the column is typically provided by condensation of a portion of the gas stream from the top of the column, and if the natural gas feed is particularly very low in C3-C5 hydrocarbons and/or C2-C5 hydrocarbons (i.e. concentration of these components is very low), it becomes very energetically inefficient to maintain the necessary relationship between liquid and vapor inside the column. Therefore, if the natural gas feed is low in C3-C5 hydrocarbons and/or in C2-C5 hydrocarbons, and contains relatively high concentrations of heavy hydrocarbons, conventional scrubbing column technology is energy inefficient.

[0005] As is well known in the art, temperature swing adsorption (AOT) involves at least two stages. During a first stage (commonly referred to as the "adsorption stage") a gaseous feed stream is passed through one or more beds of adsorbents at a first temperature and for a first period of time, during which the adsorbent selectively adsorbs one or more more components of the feed stream, thus providing a gaseous vapor depleted in the adsorbed components. At the end of said adsorption stage (which typically occurs when the adsorbent approaches saturation), the introduction of the feed current into the beds in question is interrupted. Then, in a subsequent stage (typically referred to as a "desorption stage" or "regeneration stage") the beds are regenerated by desorbing the adsorbed components from the bed(s) at a second higher temperature, and over a period of sufficient time to sufficiently desorb the adsorbed components to allow the bed or beds in question to be used for another adsorption step. Typically, during the regeneration step another gas stream (referred to as "regeneration gas") is passed through the bed to aid in desorption and removal of desorbed components. In some AOT processes (often referred to as temperature and pressure swing adsorption or TPSA processes), the regeneration step is also carried out at a lower pressure than the pressure during the adsorption step. In most AOT processes it is also the case that two or more adsorbent beds are used in parallel, with the times of the adsorption stages being staggered between the beds such that at any point there is always at least one bed experiencing a desorption step. adsorption, thus allowing continuous processing of a feed stream. Each adsorbent bed may contain a single type of adsorbent material, or may contain more than one type of adsorbent material, and where there is more than one bed, different beds may contain different materials (in particular, where there are two or more beds arranged in series) . Suitable types of adsorbent material for selectively adsorbing heavy hydrocarbons are well known.

[0006] AOT can be used to effectively remove heavy hydrocarbons from a natural gas stream at the ideal pressure for subsequent liquefaction of the stream, contributing to high energy efficiency in the liquefaction process. However, if heavy hydrocarbon concentrations are too high then the size of the AOT reactors and the gas and regeneration requirements become economically unfeasible. Therefore, AOT is effective in removing heavy hydrocarbons in natural gas liquefaction processes only when heavy hydrocarbon concentrations are relatively low. Furthermore, an additional complication is that AOT adsorbent beds used for hydrocarbon removal must be regenerated at elevated temperatures (i.e., 232-315°C -450-600°F). At these temperatures there is a risk of cracking of the adsorbed heavy hydrocarbons and the production of coke, which will deactivate the adsorbent and is detrimental to productivity.

[0007] The existing technique in this field includes international documents WO 2009/074737, WO 2007/018677, North American US 3841058 and US 5486227 (which describe processes in which adsorption systems are used); and North American US 7600395, US 5325673, international WO 2006/061400, North American US 2006/0042312, and US 2005/0072186 (which describe processes in which washing columns are employed).

[0008] Therefore, there is a need in the art for improved methods and equipment for removing heavy hydrocarbons from natural gas streams, in particular where the natural gas stream has a relatively high concentration of heavy hydrocarbons or where the exact composition of the natural gas stream is likely to vary and/or may be otherwise unknown such that there is a risk of said stream having (at least at times) a relatively high concentration of heavy hydrocarbons.

BRIEF SUMMARY OF THE INVENTION

[0009] In accordance with a first aspect of the present invention, there is provided a method of removing heavy hydrocarbons from a natural gas feed stream, the method comprising the steps of using a first heavy hydrocarbon removal system and a second heavy hydrocarbon removal system for processing the natural gas feed stream to produce a heavy hydrocarbon-poor natural gas stream, wherein said first and second systems are used in series such that the first system processes the stream of natural gas feed to produce a heavy hydrocarbon depleted natural gas stream and the second system processes at least a portion of the heavy hydrocarbon depleted natural gas stream of the first system to produce the heavy hydrocarbon depleted natural gas stream, and wherein one of said systems is an adsorption system comprising one or more adsorbent beds for adsorbing and thereby removing heavy hydrocarbons from a natural gas containing heavy hydrocarbon systems, and the gas-liquid separation system other than said for a is a system separation of a natural gas containing heavy hydrocarbons into a natural gas vapor depleted of heavy hydrocarbons and a liquid rich in heavy hydrocarbons.

[00010] The gas-liquid separation system can be any type of system that is suitable for separating a natural gas containing heavy hydrocarbons (typically a partially condensed natural gas containing heavy hydrocarbons) in the form of a natural gas vapor exhausted from heavy hydrocarbons and a liquid rich in heavy hydrocarbons. For example, the gas-liquid separation system may comprise a separation column, a washing column, or a phase separator. Preferably, however, the gas-liquid separation system comprises a separation column or a phase separator.

[00011] The adsorption system can be any type of system comprising one or more beds of adsorbents suitable for adsorbing, and therefore removing, heavy hydrocarbons from a natural gas containing heavy hydrocarbons. Preferably, however, the adsorption system comprises a temperature swing adsorption (AOT) system.

[00012] The term "portion", as used herein in reference to a stream, and unless otherwise indicated, refers to a portion of a stream which preferably is a divided portion of a stream obtained by dividing said current into two or more portions that preserve the same molecular composition (that is, that have the same components, in the same mole fractions) as the said current from which they were divided. Thus, for example, in the first aspect of the invention it is preferably the case that the second heavy hydrocarbon removal system either processes the entire heavy hydrocarbon depleted natural gas stream from the first heavy hydrocarbon removal system, or processes a portion split from the natural gas stream depleted of heavy hydrocarbons from the first heavy hydrocarbon removal system.

[00013] The heavy hydrocarbon components present in the natural gas feed stream that must be removed comprise one or more hydrocarbons selected from the group consisting of: aliphatic hydrocarbons with six or more total carbon atoms; and aromatic hydrocarbons. The heavy hydrocarbon-depleted natural gas stream obtained from the second heavy hydrocarbon removal system is depleted of each of these heavy hydrocarbon components compared to the natural gas feed stream, such that the mole fraction of each of these components in the stream of natural gas poor in heavy hydrocarbons than is less than in the natural gas supply stream. The heavy hydrocarbon depleted natural gas stream obtained from the first heavy hydrocarbon removal system is depleted of at least some of these heavy hydrocarbon components compared to the natural gas feed stream such that the total concentration of these components ( that is, the combined mole fraction of these components) in the heavy hydrocarbon-depleted natural gas stream is lower than in the natural gas feed stream, although, of course, not as low as in the heavy hydrocarbon-depleted natural gas stream obtained from the second heavy hydrocarbon removal system (by removing heavy hydrocarbons from the natural gas stream depleted of heavy hydrocarbons). Preferably, the heavy hydrocarbon depleted natural gas stream obtained from the first heavy hydrocarbon removal system is depleted of each of these heavy hydrocarbon components compared to the natural gas feed stream.

[00014] In certain embodiments, the method can be used to remove heavy hydrocarbons from a natural gas feed stream that has a composition that could become problematic for treatment using an AOT-type system itself or by scrubbing column itself. For example: the natural gas feed stream may be low in aliphatic hydrocarbons with 3 to 5 total carbon atoms, such as, for example, where the total concentration of any and all C3-C5 hydrocarbons in the feed stream (i.e., the concentration of any and all C3-C5 hydrocarbons in the feed stream, when taken together) is 5 mol% or less, or 3 mol% or less, or 2 mol% or less, or of 1 mol% or less; and/or the natural gas feed stream may be low in aliphatic hydrocarbons having between 2 and 5 carbon atoms in total, such as, for example, where the total concentration of any and all C2-C5 hydrocarbons in the feed stream feed (i.e., the concentration of any and all C2-C5 hydrocarbons in the feed stream, when taken together) is 10 mol% or less, or 5 mol% or less, or 4 mol% or less. Likewise, the natural gas feed stream may alternatively or additionally have a relatively high concentration of heavy hydrocarbons, such as where the natural gas feed stream has a total concentration of the heavy hydrocarbon components of 100 ppm or more, or 250 ppm or more (i.e., the concentration of all aromatic compounds and C6+ aliphatic hydrocarbons in the feed stream together total 100 ppm or more, or 250 ppm or more).

[00015] In certain preferred embodiments, the method further comprises liquefying at least a portion of the heavy hydrocarbon-poor natural gas stream to produce a liquefied natural gas stream.

[00016] In preferred embodiments, the composition of the heavy hydrocarbon-poor natural gas stream is such that any and all heavy hydrocarbons that are still present in said stream are present in said stream at lower (and preferably well below) concentrations. ) of their respective limits of solid solubility at the temperature of the liquefied natural gas stream.

[00017] In one embodiment, the gas-liquid separation system is the first heavy hydrocarbon removal system, and the method comprises the steps of: introducing the natural gas feed stream to the gas-liquid separation system and separating the natural gas feed stream in the form of a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons; and passing at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream through the one or more beds of the adsorption system to adsorb heavy hydrocarbons therefrom, thereby producing the heavy hydrocarbon-depleted natural gas stream. The method may further comprise cooling the natural gas feed stream before said stream is introduced into the gas-liquid separation system, and heating the natural gas vapor stream depleted of heavy hydrocarbons before said stream or portion of the same to be passed through the one or more beds of the adsorption system, in which the natural gas feed stream is cooled and the natural gas vapor stream depleted of heavy hydrocarbons is heated in a heat-saving exchanger by means of exchange indirect heat exchange between the natural gas feed stream and the natural gas vapor stream depleted of heavy hydrocarbons. Alternatively, the method may further comprise heating the heavy hydrocarbon depleted natural gas vapor stream before said vapor or a portion thereof is passed through the one or more beds of the adsorption system, and cooling at least a portion of the stream. of heavy hydrocarbon-depleted natural gas to produce a heavy hydrocarbon-depleted chilled natural gas stream, wherein the heavy hydrocarbon-depleted natural gas vapor stream is heated and at least a portion of the heavy hydrocarbon-depleted natural gas stream is cooled in a heat-saving exchanger through indirect thermal exchange between the natural gas vapor stream depleted of heavy hydrocarbons and at least a portion of the natural gas stream poor in heavy hydrocarbons.

[00018] In an alternative embodiment, the adsorption system is the first heavy hydrocarbon removal system, and the method comprises the steps of: passing the natural gas feed stream through the one or more beds of the adsorption system to adsorb hydrocarbons heavy of them, thus producing a stream of natural gas poor in heavy hydrocarbons; and introducing at least a portion of the natural gas stream depleted in heavy hydrocarbons to the gas-liquid separation system and separating said stream or portion thereof in the form of a natural gas vapor stream that is further depleted of heavy hydrocarbons, thus providing the natural gas stream poor in heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons.

[00019] In accordance with a second aspect of the present invention, there is provided equipment for removing heavy hydrocarbons from a natural gas feed stream, the equipment comprising a first heavy hydrocarbon removal system and a second heavy hydrocarbon removal system. removing heavy hydrocarbons for processing the natural gas feed stream to produce a heavy hydrocarbon-poor natural gas stream, wherein said first and second systems are in mutual connection by continuous flow communication, arranged in series; such that during use the first system processes the natural gas feed stream to produce a heavy hydrocarbon-poor natural gas stream and the second system processes at least a portion of the heavy hydrocarbon-poor natural gas stream from the first system to produce the natural gas stream poor in heavy hydrocarbons, and wherein one of said systems is an adsorption system comprising one or more beds of adsorbent for adsorbing and thereby removing heavy hydrocarbons from a natural gas stream containing heavy hydrocarbons, and the other of said systems is a system for separating natural gas containing heavy hydrocarbons, in the form of a natural gas vapor depleted of heavy hydrocarbons and a liquid rich in heavy hydrocarbons.

[00020] The equipment according to the second aspect of the invention is suitable for carrying out the method according to the first aspect of the invention. Preferred embodiments of the equipment according to the second aspect will therefore be apparent from the above discussion of preferred embodiments of the method according to the first aspect. In particular: Preferably, the gas-liquid separation system comprises a separation column or a phase separator. Preferably the adsorption system comprises a temperature swing adsorption system. Preferably, the equipment further comprises a liquefaction device in continuous flow communication connection with the second heavy hydrocarbon removal system for receiving and liquefying at least a portion of the heavy hydrocarbon-poor natural gas stream to produce a natural gas stream. liquefied.

[00021] In one embodiment, the gas-liquid separation system is the first heavy hydrocarbon removal system, and the equipment comprises: a gas-liquid separation system, for receiving and separating the natural gas feed stream in the form of a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons; and an adsorption system, in continuous flow communication with the gas-liquid separation system, for receiving at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, and comprising one or more adsorbent beds for adsorbing heavy hydrocarbons. from said at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, thus producing the heavy hydrocarbon-poor natural gas stream. The equipment may additionally comprise a heat-saving exchanger for cooling the natural gas feed stream, before said stream is introduced into the gas-liquid separation system, and heating the hydrocarbon-depleted natural gas vapor stream. heavy hydrocarbons, before said stream or portion thereof is passed through the one or more beds of the adsorption system, through indirect thermal exchange between the natural gas supply stream and the natural gas vapor stream depleted of heavy hydrocarbons. Alternatively, the equipment may additionally comprise a heat-saving exchanger for heating the depleted natural gas vapor stream of heavy hydrocarbons, before said stream or part thereof is passed through the one or more adsorption system beds. and cooling at least a portion of the heavy hydrocarbon-poor natural gas stream through indirect thermal exchange between the heavy hydrocarbon-depleted natural gas vapor stream and at least a portion of the heavy hydrocarbon-poor natural gas stream.

[00022] In an alternative embodiment, the adsorption system is the first heavy hydrocarbon removal system, and the equipment comprises: an adsorption system for receiving the natural gas feed stream, and comprises one or more adsorbent beds for adsorbing heavy hydrocarbons from the natural gas feed stream, to thus produce a natural gas stream poor in heavy hydrocarbons; and a gas-liquid separation system, in continuous flow communication with the adsorption system, for receiving at least a portion of the heavy hydrocarbon-poor natural gas stream and separating said stream or portion thereof as a hydrocarbon-rich liquid stream. heavy hydrocarbons and a natural gas vapor stream that is more depleted of heavy hydrocarbons, the latter providing the heavy hydrocarbon-poor natural gas stream.

[00023] According to a third aspect of the present invention, there is provided a method for removing heavy hydrocarbons from and by liquefaction of a natural gas stream, the method comprising: passing the natural gas stream through an adsorption system comprising one or more adsorbent beds for adsorbing and thereby removing heavy hydrocarbons from the natural gas stream, thereby producing a natural gas stream depleted in heavy hydrocarbons; liquefying the natural gas stream depleted of heavy hydrocarbons to produce a liquefied natural gas stream; and regenerating the one or more beds of the adsorption system by temperature oscillation by passing a flash gas or obtained as a vaporized liquefied natural gas through the one or more beds. Preferably, the adsorption system is a temperature swing adsorption system, the temperature of the one or more beds during regeneration being higher than the temperature of the one or more beds during adsorption of the heavy hydrocarbons from the gas stream. Natural.

[00024] Preferred aspects of the present invention include the following aspects, enumerated from 1 to 33: 1. A method of removing heavy hydrocarbons from a natural gas feed stream, the method comprising the steps of using a first system heavy hydrocarbon removal system and a second heavy hydrocarbon removal system for processing the natural gas feed stream to produce a heavy hydrocarbon-poor natural gas stream, wherein said first and second systems are used in series such that the The first system processes the natural gas feed stream to produce a heavy hydrocarbon depleted natural gas stream and the second system processes at least a portion of the heavy hydrocarbon depleted natural gas stream from the first system to produce the lean natural gas stream. in heavy hydrocarbons, and wherein one of said systems is an adsorption system comprising one or more beds of adsorbent for adsorbing and thereby removing heavy hydrocarbons from a natural gas containing heavy hydrocarbons, and the other of said systems is a gas separation system -liquid for separating a natural gas containing heavy hydrocarbons such as a natural gas vapor depleted of heavy hydrocarbons and a liquid rich in heavy hydrocarbons. 2. Method according to Aspect 1, wherein the gas-liquid separation system comprises a separation column or a phase separator. 3. Method according to Aspect 1 or 2, wherein the method is also a method for producing a liquefied natural gas stream, and which further comprises liquefying at least a portion of the heavy hydrocarbon-poor natural gas stream to produce the liquefied natural gas stream. 4. Method according to any of Aspects 1 to 3, wherein the gas-liquid separation system is the first heavy hydrocarbon removal system, the method comprising the steps of: introducing the natural gas feed stream to the system gas-liquid separation and separation of the natural gas feed stream into a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons; and passing at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream through the one or more beds of the adsorption system to adsorb heavy hydrocarbons therefrom, thereby producing the heavy hydrocarbon-depleted natural gas stream. 5. Method according to Aspect 4, wherein the method further comprises cooling the natural gas feed stream before said stream is introduced into the gas-liquid separation system, and heating the natural gas vapor stream. natural gas depleted of heavy hydrocarbons, before said stream or portion thereof is passed through the one or more beds of the adsorption system. 6. Method according to Aspect 5, wherein the natural gas feed stream is cooled and the heavy hydrocarbon depleted natural gas vapor stream is heated in a heat-saving exchanger by means of indirect heat exchange between the stream natural gas feed and the natural gas vapor stream depleted of heavy hydrocarbons. 7. Method according to Aspect 6, wherein the natural gas feed stream is additionally cooled before being introduced into the gas-liquid separation system through expansion of the natural gas feed stream and/or through exchange direct or indirect thermal with one or more other currents. 8. Method according to Aspect 6 or 7, wherein the method further comprises liquefaction of at least a portion of the heavy hydrocarbon-poor natural gas stream. 9. Method according to Aspect 5, wherein the method further comprises cooling at least a portion of the heavy hydrocarbon-poor natural gas stream to produce a chilled heavy hydrocarbon-poor natural gas stream, and wherein the vapor stream of natural gas depleted of heavy hydrocarbons is heated and at least a portion of the natural gas stream depleted of heavy hydrocarbons is cooled in a heat-saving exchanger through indirect thermal exchange between the natural gas vapor stream depleted of heavy hydrocarbons and the at least a portion of the natural gas stream poor in heavy hydrocarbons. 10. Method according to Aspect 9, wherein the method further comprises liquefaction of the heavy hydrocarbon-poor cooled natural gas stream. 11. Method according to Aspect 10, wherein the natural gas feed stream is cooled and the cooled natural gas stream poor in heavy hydrocarbons is liquefied in a liquefaction device, the natural gas feed stream being introduced into a hot end of the liquefaction device and drawn from an intermediate position of the liquefaction device, and the cooled natural gas stream poor in heavy hydrocarbons being introduced at an intermediate position of the liquefaction device and drawn from a cold end of the liquefaction device. 12. Method according to any of Aspects 4 to 11, wherein the gas-liquid separation system is a separation column, the method further comprising introducing an extraction gas into the separation column at a location below the location at which that the natural gas feed stream is introduced into the separation column. 13. Method according to any of Aspects 6 to 8, wherein the gas-liquid separation system is a separation column, the method further comprising introducing an extraction gas into the separation column at a location below the location at which wherein the natural gas feed stream is introduced into the separation column, and where the extraction gas comprises one or more gases selected from the group comprising: natural gas taken from the natural gas feed stream before said stream is cooled and introduced into the separation column; a portion of the heavy hydrocarbon-poor natural gas stream that was heated in the heat-saving exchanger; a portion of the natural gas stream depleted of heavy hydrocarbons; a gas obtained from boiling all or part of a liquid stream rich in heavy hydrocarbons; and a flash gas or obtained as a vaporizate of a liquefied natural gas. 14. Method according to any of Aspects 9 to 11, wherein the gas-liquid separation system is a separation column, the method further comprising introducing an extraction gas into the separation column at a location below the location at wherein the natural gas feed stream is introduced into the separation column, and wherein the extraction gas comprises one or more gases selected from the group comprising: natural gas taken from the natural gas feed stream prior to said stream be cooled and introduced into the separation column; a portion of the natural gas stream poor in heavy hydrocarbons that is not cooled in the heat-saving exchanger; a portion of the natural gas stream depleted in heavy hydrocarbons that was heated in the heat-saving exchanger; a gas obtained from the boiling of all or part of a liquid stream rich in heavy hydrocarbons; and a flash gas or obtained as a vaporizate of a liquefied natural gas. 15. Method according to any of Aspects 4 to 14, wherein the adsorption system is a temperature swing adsorption system, and the method further comprising regenerating the one or more beds of the temperature swing adsorption system by the passage of a gas, selected from a portion of the natural gas stream poor in heavy hydrocarbons or from a flash gas or obtained as a vaporized from a liquefied natural gas, through the one or more beds, the temperature of the one or more beds during regeneration being higher than the temperature of the one or more beds during adsorption of heavy hydrocarbons from the heavy hydrocarbon-depleted natural gas vapor stream or a portion thereof. 16. Method according to Aspect 15, wherein the method further comprises cooling and separating into liquid and vapor phases the gas obtained from the one or more beds of the adsorption system by temperature oscillation during the regeneration of said one or more beds, and the recycling of the vapor phase in the natural gas supply stream before its introduction to the gas-liquid separation system. 17. Method according to Aspect 15, wherein the gas-liquid separation system is a separation column, and the method further comprises cooling and separating into liquid and vapor phases the gas obtained from the one or more beds of the adsorption system by temperature swing during the regeneration of said one or more beds, and the introduction of the vapor phase as an extraction gas into the separation column at a location below the location at which the natural gas feed stream is introduced in the separation column. 18. Method according to any of Aspects 1 to 3, wherein the adsorption system is the first heavy hydrocarbon removal system, the method comprising the steps of: passing the natural gas feed stream through the one or more beds of the adsorption system for adsorbing heavy hydrocarbons therefrom thereby producing a heavy hydrocarbon-depleted natural gas stream; and introducing at least a portion of the heavy hydrocarbon-depleted natural gas stream into the gas-liquid separation system and separating said stream or portion thereof into a natural gas vapor stream that is further depleted of heavy hydrocarbons, providing thus the natural gas stream poor in heavy hydrocarbons, and a liquid stream rich in heavy hydrocarbons. 19. Method according to Aspect 18, wherein the method further comprises cooling the heavy hydrocarbon-poor natural gas stream or part thereof to be introduced into the gas-liquid separation system before said stream or part thereof is introduced. be introduced into the gas-liquid separation system. 20. Method according to Aspect 19, wherein the method further comprises liquefaction of the heavy hydrocarbon-poor natural gas stream. 21. Method according to Aspect 20, wherein the heavy hydrocarbon-poor natural gas stream or a portion thereof is cooled and the heavy hydrocarbon-poor natural gas stream is liquefied in a liquefaction device, the natural gas stream depleted of heavy hydrocarbons or a portion thereof being introduced at a heated end of the liquefaction device and extracted from an intermediate location of the liquefaction device, and the heavy hydrocarbon-depleted natural gas stream being introduced at an intermediate location of the liquefaction device and extracted at from a cold end of the liquefaction device. 22. Method according to any of Aspects 18 to 21, wherein the gas-liquid separation system is a separation column, the method further comprising introducing an extraction gas into the separation column at a location below the location at that the natural gas stream depleted in heavy hydrocarbons or a portion thereof is introduced into the separation column. 23. Method according to Aspect 22, wherein the extraction gas comprises one or more gases selected from the group comprising: natural gas taken from the natural gas supply stream before said stream is passed through a or more beds of the adsorption system; a portion of the natural gas stream depleted of heavy hydrocarbons; a gas obtained from the boiling of all or part of a liquid stream rich in heavy hydrocarbons; and a flash gas or obtained as a vaporizate of a liquefied natural gas. 24. Method according to any of Aspects 18 to 23, wherein the adsorption system is a temperature swing adsorption system, and the method further comprises regenerating the one or more beds of the temperature swing adsorption system by the passage of a gas selected from a portion of the natural gas stream depleted in heavy hydrocarbons or a flash gas or obtained as a vaporizate of a liquefied natural gas, through the one or more beds, the temperature of the one or more beds during regeneration being higher than the temperature of the one or more beds during adsorption of heavy hydrocarbons from the natural gas feed stream. 25. Method according to Aspect 24, wherein the method further comprises cooling and separating into liquid and vapor phases the gas obtained from the one or more beds of the adsorption system by temperature oscillation during the regeneration of said one or more beds, and recycling the vapor phase in the natural gas feed stream, before said stream is passed through the one or more beds of the temperature swing adsorption system. 26. The method of Aspect 24, wherein the gas-liquid separation system is a separation column, and the method further comprises introducing an extraction gas into the separation column at a location below the location at which the natural gas stream depleted in heavy hydrocarbons or a portion thereof is introduced into the separation column, wherein said extraction gas comprises: the gas obtained from the one or more beds of the adsorption system by temperature swing during the regeneration of the referred to one or more beds; or the vapor phase obtained from the cooling and separation into liquid and vapor phases of the gas obtained from the one or more beds of the adsorption system by temperature fluctuation during the regeneration of said one or more beds. 27. Method according to any of Aspects 1 to 26, wherein the natural gas feed stream is lean in aliphatic hydrocarbons having 3 to 5 total carbon atoms, and/or is lean in aliphatic hydrocarbons having between 2 and 5 carbon atoms in total. 28. An apparatus for removing heavy hydrocarbons from a natural gas feed stream, the equipment comprising a first heavy hydrocarbon removal system and a second heavy hydrocarbon removal system for processing the natural gas feed stream to produce a natural gas stream poor in heavy hydrocarbons, wherein said first and second systems are mutually connected in continuous flow communication and arranged in series such that in use the first system processes the natural gas feed stream to produce a stream of heavy hydrocarbon-depleted natural gas stream and the second system processes at least a portion of the heavy hydrocarbon-depleted natural gas stream of the first system to produce the heavy hydrocarbon-depleted natural gas stream, and wherein one of said systems is a adsorption comprising one or more adsorbent beds for adsorbing and removing heavy hydrocarbons and thereby removing heavy hydrocarbons from a natural gas stream containing heavy hydrocarbons, and the other of said systems is a gas-liquid separation system for separating a natural gas containing heavy hydrocarbons in the form of a natural gas vapor depleted of heavy hydrocarbons and a liquid rich in heavy hydrocarbons. 29. An equipment according to Aspect 28, wherein the gas-liquid separation system comprises a separation column or a phase separator. 30. An equipment according to Aspect 28 or 29, wherein the equipment is further for producing a stream of liquefied natural gas, and further comprises a liquefaction device in continuous flow communication connection with the second heavy hydrocarbon removal system to receive and liquefy at least a portion of the heavy hydrocarbon-poor natural gas stream to produce the liquefied natural gas stream. 31. Equipment according to any one of aspects 28 to 30, wherein the gas-liquid separation system is the first heavy hydrocarbon removal system, the equipment comprising: a gas-liquid separation system for receiving and separating the stream natural gas feed in the form of a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons; an adsorption system, in continuous flow communication with the gas-liquid separation system for receiving at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, and comprising one or more adsorbent beds for adsorbing heavy hydrocarbons from of said at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, thus producing the heavy hydrocarbon-poor natural gas stream; and a heat-saving exchanger for cooling the natural gas feed stream, before said stream is introduced into the gas-liquid separation system, and heating the natural gas vapor stream depleted of heavy hydrocarbons, before the said stream or part thereof being passed through the one or more beds of the adsorption system, by means of indirect thermal exchange between the natural gas feed stream and the natural gas vapor stream depleted of heavy hydrocarbons. 32. An apparatus according to any one of aspects 28 to 30, wherein the gas-liquid separation system is the first heavy hydrocarbon removal system, the apparatus comprising: a gas-liquid separation system for receiving and separating the natural gas feed stream in the form of a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons; an adsorption system in continuous flow communication with the gas-liquid separation system, for receiving at least a portion of the natural gas vapor stream depleted of heavy hydrocarbons, and comprising one or more adsorbent beds for adsorbing heavy hydrocarbons from of said at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, thus producing the heavy hydrocarbon-poor natural gas stream; and a heat-saving exchanger for heating the heavy hydrocarbon-poor natural gas stream before said stream or a portion thereof is passed through the one or more beds of the adsorption system, and cooling at least a portion of the gas stream. natural gas poor in heavy hydrocarbons through indirect thermal exchange between the natural gas vapor stream depleted of heavy hydrocarbons and at least a portion of the natural gas stream poor in heavy hydrocarbons. 33. An equipment according to any one of aspects 28 to 30, wherein the adsorption system is the first heavy hydrocarbon removal system, the equipment comprising: an adsorption system for receiving the natural gas feed stream, and comprising one or more adsorbent beds for adsorbing heavy hydrocarbons from the natural gas feed stream, thereby producing a heavy hydrocarbon-poor natural gas stream; and a gas-liquid separation system, in continuous flow communication with the adsorption system, for receiving at least a portion of the natural gas stream poor in heavy hydrocarbons and separating said stream or a portion thereof into a liquid stream rich in hydrocarbons heavy hydrocarbons and a natural gas vapor stream that is more depleted of heavy hydrocarbons, the latter providing the heavy hydrocarbon-poor natural gas stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[00025] Figures 1(a) to (f) show a first set of embodiments of the present invention, in which a gas-liquid separation system is used and placed upstream of and in series with an adsorption system in order to removing heavy hydrocarbons from a natural gas feed stream;

[00026] Figures 2(a) to (d) illustrate a second set of embodiments of the present invention, in which a gas-liquid separation system is used and placed upstream of and in series with an adsorption system in order to removing heavy hydrocarbons from a natural gas feed stream;

[00027] Figures 3(a) to (d) show a third set of embodiments of the present invention, in which an adsorption system is used and arranged upstream of and in series with a gas-liquid separation system, in order of removing heavy hydrocarbons from a natural gas feed stream; It is

[00028] Figure 4 is a graph that translates the results of using a series adsorption system and a gas-liquid separation system to remove heavy hydrocarbons from a natural gas feed stream, compared to using of a scrubbing column properly for removing heavy hydrocarbons from a natural gas feed stream.

DETAILED DESCRIPTION OF THE INVENTION

[00029] In certain aspects, the present invention relates to a method and equipment in which an adsorption system is used in combination with a gas-liquid separation system so as to effectively remove heavy hydrocarbons (i.e., one or more 6+ and/or aromatic hydrocarbons) from a natural gas stream.

[00030] When the natural gas stream has a composition that is poor in C3-C5 components and/or poor in C2C5 components, and contains relatively high levels of heavy hydrocarbons, any heavy hydrocarbon removal regime that employs a system of the type AOT or washing column itself is ineffective or energy inefficient. The inventors have found that this problem can be solved by using an adsorption system (preferably an AOT-type system) in combination with a gas-liquid separation system (preferably comprising a phase separator or a separation column).

[00031] In particular, the method and equipment according to the present invention can improve the energy efficiency of the liquefaction process by allowing a phase separator or separation column (or other gas-liquid separation system) to be operated at a higher pressure than a conventional washing column.

[00032] Furthermore, when a liquefied natural gas (LNG) production plant has natural gas supplies that come from multiple gas fields or are contaminated with heavy components, the LNG plant faces the challenge of uncertain levels of heavy hydrocarbons. . The method and equipment according to the present invention can prevent the LNG plant from having freezing problems within a wide range of heavy hydrocarbon concentrations, thereby providing operational flexibility when dealing with uncertain or changing gas compositions.

[00033] Furthermore, in the method and equipment according to the present invention, the load on the absorption beds of the AOT-type (or other type) system is reduced due to the fact that part of the heavy hydrocarbons is removed in the system gas-liquid separation system, which reduces the risk of cracking of heavy hydrocarbons in the bed or beds of the AOT-type system during high-temperature regeneration (e.g., 232-315°C, 450-600°F) of the said bed or beds, the cracking of which may otherwise result in deactivation of the bed.

[00034] In the present method and equipment, the adsorption system and the gas-liquid separation system are used in series to process the natural gas stream to remove heavy hydrocarbons from it.

[00035] The adsorption system can be placed downstream of the gas-liquid separation system, such that the gas-liquid separation system removes most of the heavy hydrocarbons and controls the amount of heavy hydrocarbons at the inlet of the adsorption system, the adsorption system then removes the remainder of the heavy hydrocarbons to levels necessary or acceptable to prevent subsequent freezing during liquefaction of the natural gas.

[00036] Alternatively, the adsorption system can be placed upstream of the gas-liquid separation system, such that the adsorption system removes most of the heavy hydrocarbons, and the gas-liquid separation system removes the remainder of the heavy hydrocarbons. to levels necessary or acceptable to prevent subsequent freezing during natural gas liquefaction. The composition of the natural gas stream for the gas-liquid separation system is, in this case, controlled by the system design and adsorption capacity.

[00037] The adsorption system and the gas-liquid separation system can be installed as a front-situated heavy hydrocarbon removal unit that processes the natural gas, before the natural gas stream enters a separate liquefaction unit. Alternatively, the adsorption system and the gas-liquid separation system can be integrated into a liquefaction unit.

[00038] Typically (and depending in part on factors such as the initial temperature of the natural gas stream and whether the gas-liquid separation system is upstream or downstream of the adsorption system) the gas-liquid separation system will require refrigeration to partially condense the stream to be fed to the gas-liquid separation system. As will be discussed in more detail below, this refrigeration can be provided in a variety of ways including, but not limited to: refrigeration provided via the Joule-Thompson effect (i.e., isenthalpic, or largely isenthalpic, the expansion of chain); cooling the stream through indirect heat exchange in a part of the natural gas liquefaction device; cooling the stream by means of indirect heat exchange in another heat exchanger (against another process stream and/or against a separate refrigerant, such as, for example, a mixed refrigerant); or adding LNG to cool the stream through direct heat exchange.

[00039] By way of example only, several preferred embodiments of the invention will now be described with reference to the accompanying drawings, a first group being represented in Figures 1(a)-(f), a second group being represented in Figures 2(a) -(d), and a third group being represented in Figures 3(a)-(d). In drawings, where a feature is common to more than one drawing, that feature is assigned the same reference numeral in each drawing for clarity and conciseness.

Figures 1(a)-(f)

[00040] In a first group of embodiments, represented in figure 1(a)-(f), the gas-liquid separation system is upstream of the adsorption system, such that the gas-liquid separation system processes the feed stream of natural gas (from which heavy hydrocarbons must be removed) to produce a heavy hydrocarbon-depleted natural gas stream, and the adsorption system processes at least a portion of the heavy hydrocarbon-depleted natural gas stream from the separation system gas-liquid to produce the desired heavy hydrocarbon-poor natural gas stream.

[00041] More specifically, in the first group of embodiments the natural gas feed stream is heat-saving exchanger, and then introduced into the gas-liquid separation system being separated as a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons. The natural gas vapor stream depleted of heavy hydrocarbons is then heated in the heat-saving exchanger through indirect heat exchange with the natural gas feed stream. The resulting heated stream of natural gas vapor depleted of heavy hydrocarbons or a portion thereof is then passed through the one or more beds of the adsorption system to adsorb heavy hydrocarbons therefrom and then further reduce the concentration of heavy hydrocarbons in said stream or portion. (thus providing the desired natural gas stream poor in heavy hydrocarbons).

[00042] Referring now to Figure 1(a), a specific embodiment is shown in which an extraction column and a temperature swing adsorption system are used in series to remove heavy hydrocarbons from a natural gas feed stream. A methane-rich natural gas feed stream (100) is first passed through a heat-saving exchanger (10), where it is cooled through indirect heat exchange with a heavy hydrocarbon-depleted natural gas vapor stream (104). ), whose description will be given later. The cooled natural gas feed stream (101) is then cooled further by reducing pressure through a Joule-Thompson (JT) type valve (20). The further cooled and now partially condensed natural gas feed stream (102) is then introduced into a separation column (30).

[00043] The separation column (30) can be of any suitable design. As is well known in the art, in a separation column, a condensed or partially condensed feed stream (in this case a partially condensed natural gas feed stream) is introduced into the separation column, where it is brought into contact with an extraction gas. . The feed stream is introduced into the separation column at a location above the location where the extraction gas is introduced, such that the descending liquid stream from the feed stream comes into countercurrent contact with the ascending stream of extraction gas. , thus "extracting" said liquid from less volatile components. Typically, the separation column contains one or more separation stages, positioned between the location at which the feed stream is introduced and the position at which the stripping gas is introduced, and is composed of trays, packing, or some other form of separation. insertion that acts to increase the amount and/or duration of contact between the supply liquid and the extraction gas stream, thus increasing the mass transfer between the streams. Typically, there is no phase separation above the position at which the feed stream is introduced into the separation column.

[00044] In the embodiment depicted in Figure 1(a), the further cooled and partially condensed natural gas feed stream (102) is introduced at the top of the separation column (30), and an extraction gas (109) is introduced the lower part of the separation column, the separation column comprising one or more separation stages in positioning between the feed locations of the natural gas supply stream and the extraction gas. The extraction gas for the separation column may come from any of a variety of different sources, as will be described in more detail with reference to Figure 1(c), but in the particular embodiment depicted in Figure 1(a) it comprises a stream natural gas supply (109) socket of the natural gas supply chain (100) upstream of the heat saving exchanger (10).

[00045] The separation column (30) separates the partially condensed natural gas feed stream (102) as a vapor stream of heavy hydrocarbon-depleted natural gas (104), which is extracted from the top of the separation column, and a liquid stream rich in heavy hydrocarbons (103), which is removed from the bottom of the separation column. Optionally, the temperature of the extraction gas (109) entering the separation column (30) can be adjusted using a heater (not shown), if it is desirable to increase the temperature of the liquid stream rich in heavy hydrocarbons (103) or reduce the methane content in said stream.

[00046] The natural gas vapor stream depleted of heavy hydrocarbons (104) extracted from the top of the separation column (30) is then passed, as described above, through the heat-saving exchanger (10) to there recover the refrigeration for cool natural gas supply stream (100). The now heated natural gas vapor stream depleted of heavy hydrocarbons (105) from the heat-saving exchanger (10) is then sent to the temperature swing adsorption system (40), comprising one or more beds of selective adsorbent for the heavy hydrocarbon components of the natural gas stream (i.e., it preferentially adsorbs the heavy hydrocarbon components of the stream). Where there are multiple beds, they can be arranged in parallel and/or in series. The heavy hydrocarbon depleted natural gas vapor stream (105) is passed through one or more of said beds to further reduce (to acceptable levels) the concentration of heavy hydrocarbons in said stream and provide the desired natural gas stream. poor in heavy hydrocarbons (107).

[00047] The heavy hydrocarbon-poor natural gas stream (107) can then be supplied as natural gas feed (107) to a natural gas liquefaction system (90) and liquefied to provide an LNG stream (110). The heavy hydrocarbons adsorbed by the adsorbent(s) can then be removed in an adsorbent regeneration step (not shown in Figure 1(a)).

[00048] Referring now to Figure 1(b), in an alternative embodiment of a phase separator (31) can be used in place of the separation column used in the embodiment represented in Figure 1(a), to separate the supply stream from partially condensed natural gas (102) into a natural gas vapor depleted of heavy hydrocarbons (104), which is extracted from the top of the separation reactor, and an enriched heavy hydrocarbon (103), which is removed from the bottom of the vessel.

[00049] As is known in the art, a phase separator differs from a separation column in that in a phase separator a partially condensed feed is simply allowed to separate (e.g., by gravity) into the form of its liquid phase and bulky gas phases, without contact with any additional extraction gases or reflux streams. Thus, compared to the separation column (30) in Figure 1(a), the phase separator (31) in Figure 1(b) does not contain separation stages (i.e., trays or packing to improve mass transfer between countercurrent flows), and no extraction gas is generated and supplied to the phase separator. Compared to the modality represented in Figure 1 (a), the modality in Figure 1(b) has the advantage of reducing investment costs, but the disadvantage that it loses more of the methane in the liquid stream rich in heavy hydrocarbons (103 ).

[00050] As described above, the embodiment represented in Figure 1(a) (and Figure 1(b)) uses a J-T valve (20) to provide additional cooling (i.e., additional cooling to that provided by the heat-saving exchanger (10)) to partially condense the natural gas feed stream (102) to the separation column (30) (or phase separator (31)). However, other options are additionally or alternatively available. Furthermore, and as noted above, it is also the case that instead of, or in addition to, use as extraction gas for the separation column (30) natural gas (109) taken from the natural gas feed stream (100 ) upstream of the economizer heat exchanger (10), other sources of extraction gas can also be used. These variations are further illustrated in Figure 1(c).

[00051] Therefore, referring now to Figure 1(c), in other embodiments additional refrigeration to partially condense the natural gas feed stream (102) to the separation column (30) may be provided by another stream that is colder than the chilled natural gas supply stream (101) leaving the heat-saving exchanger (10). For example, the natural gas feed stream may be cooled by indirect heat exchange with a refrigerant stream (130, 131), such as, for example, a mixed refrigerant stream, in a heat exchanger (21). This heat exchanger may be arranged as a separate unit from the heat-saving exchanger unit (10) and the natural gas liquefaction unit (90), as shown in Figure 1(c), or may be combined with one or more both of the heat-saving exchanger (10) and natural gas liquefaction device (90) as a single unit. Alternatively or additionally, the natural gas feed stream may be cooled by direct thermal exchange, such as by direct injection of a cold stream (133) into the natural gas stream (101, 102). In the case of direct injection, it is possible for the cold stream (133) to be obtained from a stream (132) which is further cooled by lowering the pressure through a J-T valve (82). A suitable source of a cold stream (132, 133) for direct injection into the natural gas feed stream may be, for example, a portion of the LNG obtained from the liquefaction device (90), the pressure of which has been increased by a liquid pump (not shown).

[00052] Likewise, with reference to Figure 1(c), in other embodiments the extraction gas (129) supplied to the separation column (30) may comprise one or more of the following: a stream of natural gas (109) taken from the natural gas supply stream (100) upstream of the heat-saving exchanger (10) (as already described in relation to Figure 1(a)); a portion (119) of the heated natural gas stream exhausted in heavy hydrocarbons (105) from the heat-saving exchanger (10); or a portion (108) of the heavy hydrocarbon-poor natural gas stream (106) coming from the temperature swing adsorption system (40) (in which case only a portion (107) of said heavy hydrocarbon-poor natural gas stream (106) is then sent to the liquefaction device (90) for liquefaction). Where a portion (119) of the natural gas stream depleted in heavy hydrocarbons (105) and/or a portion (108) of the natural gas stream depleted in heavy hydrocarbons (106) are used as extraction gas (129), these may first require compression in a compressor (75) before being used as an extraction gas (129). It is preferred that the extraction gas (or at least particulate extraction gas) is natural gas (109) taken from the natural gas supply stream (100), because the natural gas supply stream is typically at a pressure greater than the pressure at the bottom of the separation column, and thus the natural gas taken from this stream will typically not require any compression in order to be used as the extraction gas.

[00053] With reference to Figures 1(d) and (e), in embodiments in which a separation column (30) is used, it is also possible to recover through the separation column part of the gas generated during the regeneration of the bed or beds of the adsorption system (40). As shown in Figures 1(d) and 1(e), the adsorption system may comprise, for example, two or more parallel beds (40A and 40B), wherein while one of the beds (40A) is experiencing the adsorption process, i.e., adsorbing heavy hydrocarbons from the heavy hydrocarbon-depleted natural gas vapor stream (105), the other bed (40B) is being regenerated, regeneration gas being passed through the bed during this regeneration step in order to assist with the desorption and removal from the bed of heavy hydrocarbons adsorbed in a previous adsorption step (the bed temperature during the regeneration step being higher than the bed temperature during the adsorption step).

[00054] The regeneration gas passed through the bed (40B) undergoing the regeneration step may, for example, comprise a portion (120) of the heavy hydrocarbon-poor natural gas (106) obtained from the bed exit (40 A) that experiences the adsorption stage. Alternatively, or additionally, the regeneration gas may, for example, comprise a flash gas stream (111) or obtained as a vaporizer obtained from the processing or storage of the LNG stream (110) in, for example, the LNG storage facility (91), and which has first been compressed in a compressor (92). It should be noted that, as illustrated in Figure 1 (d), said flash gas or obtained as a vaporizer can additionally or alternatively be used as all or part of the extraction gas (112) for the separation column (30), which flash gas or obtained as a vaporizer can be used in addition to, or as an alternative to, any and all of the extraction gas sources discussed above.

[00055] The desorbed gas stream (121) that exits the bed (40B) or beds of the adsorption system during its regeneration, which will typically be at a lower pressure than the pressure of the natural gas supply stream (102) to The separation column (30) can then be cooled and partially condensed in a cooler (60), and separated into phases in a phase separator (70) in the form of a liquid condensate stream (124) which contains most of the hydrocarbons. heavy loads and a natural gas vapor stream (125).

[00056] As shown in Figure 1(d), this recovered natural gas vapor stream (125) can be compressed again in a compressor (50) and cooled in an additional cooler (80), and can then be recycled by being reintroduced into the separation column (30) at a location downstream of the natural gas supply stream (102), thereby providing yet another additional or alternative source of extraction gas. The cooler (80) after the compressor (50) is optional and can be used to control the temperature of the recovered natural gas stream (125) entering the separation column. Alternatively, as shown in Figure 1(e), the recovered natural gas vapor stream (125) can be recovered by being recycled to the natural gas feed stream (100), for example, upstream of a gas compressor. reinforcement of the supply gas (51) . Between the feed gas boost compressor (51) and the heat-saving exchanger (10) there may be various equipment (generally indicated as unit 55), such as, for example, a dryer, cooler, etc.

[00057] Although Figures 1(d) and 1(e) depict only two adsorption beds in parallel (40A and 40B), this is only for the sake of simplicity, and in practice, the methods described in these figures can be carried out using multiple or single adsorption beds, in parallel or in series.

[00058] It should also be noted that the method and equipment described above, in which the bed or beds of the AOT-type system are regenerated using a gas comprising a flash gas or boil gas obtained from the LNG stream, can also be applied to other forms of regenerative adsorption system (such as pressure swing adsorption (AOP) systems), and indeed to methods and equipment for removing heavy hydrocarbons from a natural gas stream where an adsorption system is used properly (i.e. not in combination with a gas-liquid separation system) or in conjunction with any other system.

[00059] Finally, with reference to Figure 1(f), another embodiment is shown which varies from that described in Figure 1(d) in that the separation column (30) comprises at least two separation stages such that there are of separation both above and below the entry point of the recovered natural gas stream (125) into the separation column (both stages therefore being below the entry point of the natural gas feed stream (101)).

[00060] As also illustrated in this Figure, an additional source of extraction gas for the separation column (30) can be provided through the use of a reboiler (90) at the bottom of the column to reboil a portion of the liquid stream rich in heavy hydrocarbons (103) obtained from the bottom of the separation column, this reheated portion being then reintroduced to the bottom as extraction gas. The thermal source for the reboiler can be steam, hot oil, electrical energy, or any current that is hotter than the desired temperature of the steam returning to the column. This use of such a reboiler can equally be applied to any of the preceding embodiments in which an extraction column is used.

Figures 2(a)-(d)

[00061] In the second group of embodiments, represented in Figures 2(a)-(d), the gas-liquid separation system is again upstream of the adsorption system, such that the gas-liquid separation system processes the gas stream. natural gas feed (from which heavy hydrocarbons must be removed) to produce a heavy hydrocarbon-depleted natural gas stream, and the adsorption system processes at least a portion of the heavy hydrocarbon-depleted natural gas stream coming from the gas-liquid separation system to produce the desired heavy hydrocarbon-poor natural gas stream. However, compared to the first group of embodiments (depicted in Figures 1(a)-(f)), the second group of embodiments (depicted in Figures 2(a)-(d)) is different in the way that the Natural gas feed stream to the gas-liquid separation system is cooled and the heavy hydrocarbon-depleted natural gas vapor stream from the gas-liquid separation system is heated.

[00062] More specifically, in the second group of embodiments the natural gas feed stream is again introduced into the gas-liquid separation system and separated as a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream rich in heavy hydrocarbons. , and the natural gas vapor stream depleted of heavy hydrocarbons or a portion thereof is passed through the one or more beds of the adsorption system to adsorb the heavy hydrocarbons therefrom and thereby further reduce the concentration of heavy hydrocarbons in said stream ( thus providing the desired natural gas stream poor in heavy hydrocarbons). However, in the second group of embodiments, the natural gas vapor depleted of heavy hydrocarbons is heated in the heat-saving exchanger before said stream or a portion thereof is passed through the one or more adsorption system beds, through thermal exchange. indirect with at least a portion of the heavy hydrocarbon-poor natural gas stream obtained from the adsorption system (at least a portion of the heavy hydrocarbon-poor natural gas stream being therefore also cooled in said heat-saving exchanger to provide a stream of cooled natural gas poor in heavy hydrocarbons).

[00063] Due to the fact that, in the second group of embodiments, the refrigeration recovered from the natural gas vapor stream depleted of heavy hydrocarbons is transferred in the heat-saving exchanger to at least a portion of the lean natural gas stream. heavy hydrocarbons preferably (as in the first group of embodiments) to the natural gas feed stream, in the second group of embodiments a natural gas stream poor in heavy hydrocarbons at a cooler temperature is obtained (compared to the natural gas stream low in hydrocarbons that is obtained in the first group of embodiments), but an additional source of refrigeration for the natural gas supply stream is necessary (to "replace" the refrigeration that, in the first group of embodiments, was being supplied to the natural gas supply stream). natural gas supply by heat from the exchanger economizer).

[00064] Thus, in contrast to the first group of embodiments (which is preferably the case in which the heavy hydrocarbon-poor natural gas stream is liquefied by being introduced into the hot end of, and extracted through the cold end of, a liquefaction device of natural gas), in the second group of embodiments it is preferably the case that the natural gas feed stream is cooled before being introduced into the gas-liquid separation system by being introduced at the hot end of, and extracted from, an intermediate location of a natural gas liquefaction device, and where the cooled stream of heavy hydrocarbon-poor natural gas obtained from the heat-saving exchanger is liquefied by being introduced into an intermediate location of, and extracted by, the cold end of the liquefaction device.

[00065] Referring now to Figure 2(a), an embodiment is shown in which a methane-rich natural gas feed stream (100, 201) is introduced into the hot end of a natural gas liquefaction device (90 ), is cooled in the hot stage of the liquefaction device, and drawn from an intermediate location (i.e., a location between two cooling stages of the liquefaction device, and thus neither at the hot end nor the cold end of the liquefaction device) as a cooled stream of natural gas (202). This cooled stream of natural gas (202) exiting the intermediate position of the liquefaction device (90) may be a partially condensed stream (i.e., it may have been cooled and partially condensed in the hot stage of the liquefaction device). Alternatively, the natural gas stream (202) exiting the intermediate position of the liquefaction device (90) may also be reduced in pressure (e.g., using a J-T type valve, not shown) in order to further cool and partially condense the natural gas stream (202).

[00066] In Figures 2 (a)-(d) the liquefaction device is described as a single two-stage cooling unit. For example, where the liquefaction device is a coil-type heat exchanger, it may comprise two beams, each beam representing a cooling stage. However, it is also the case that the liquefaction device may comprise more cooling stages, and instead of the stages being all contained in a single unit, the liquefaction device may comprise more than one unit, arranged in series with the cooling stages. cooling being distributed among the units.

[00067] The cooled and partially condensed natural gas stream (202) is then introduced at the top of a separation column (30) where, as in the embodiment described above with reference to Figure 1 (a), it is separated as a vapor of natural gas depleted of heavy hydrocarbons (204) which is removed from the top of the separation column and a liquid rich in heavy hydrocarbons (203) which is removed from the bottom of the separation column. An extraction gas (209) is also introduced back into the separation column at its bottom, and the separation column may again comprise one or more separation stages separating the feed locations of the natural gas feed stream and the gas feed stream. extraction.

[00068] The natural gas vapor stream depleted of heavy hydrocarbons (204) removed from the top of the separation column (30) is then passed through a heat-saving exchanger (10) to recover refrigeration therefrom. Typically, the heat-saving exchanger (10) heats the heavy hydrocarbon-poor natural gas vapor stream (204) to a temperature of (0-40°C).

[00069] The heavy hydrocarbon-poor natural gas vapor stream (205) from the heat-saving exchanger (20) is then sent to the temperature swing adsorption system (40), which again comprises one or more beds of selective adsorbent for the heavy hydrocarbon components of the natural gas stream, the heavy hydrocarbon-depleted natural gas vapor stream (205) being passed through the one or more of said beds to further reduce (to acceptable levels) the hydrocarbon concentration heavy hydrocarbons in said stream and provide the desired heavy hydrocarbon-poor natural gas stream (206). Again, where the absorption system (40) comprises a plurality of beds these may be arranged in series and/or in parallel, and again the heavy hydrocarbons adsorbed by the adsorbent(s) may then be removed in the water regeneration step. adsorbent (not shown in Figure).

[00070] The natural gas stream poor in heavy hydrocarbons (206) obtained from the exit of the absorption system (40) is then passed through the heat-saving exchanger (10) where it is cooled through indirect thermal exchange with the natural gas vapor stream depleted in heavy hydrocarbons (204) recovering from refrigeration as already described. The cooled natural gas stream (208) poor in heavy hydrocarbons leaving the heat-saving exchanger (30) is then returned to an intermediate position of the natural gas liquefaction device (90), preferably at the same intermediate position from which The cooled and partially condensed natural gas stream (202) is extracted, and cooled and liquefied in the cold stage (or chiller stages) of the liquefaction device to provide an LNG stream (110) drawn from the cold end of the liquefaction device.

[00071] Referring now to Figure 2(b), in an alternative embodiment a phase separator (31) can be used (instead of the separation column used in the embodiment represented in Figure 2(a)), to separate the supply current of partially condensed natural gas (202) as a heavy hydrocarbon-depleted natural gas vapor (204) extracted from the top of the separation column, and a liquid stream rich in heavy hydrocarbons (203) extracted from the bottom of the column. As described above in relation to the operation of the phase separator depicted in Figure 1(b), the phase separator (31) does not contain any separation stages or make use of an extraction gas, and thus in this embodiment is not used or generated extraction gas. Compared to the modality represented in Figure 2(a), the modality in Figure 2(b) has the advantage of reducing investment costs, but the disadvantage that it loses more methane in the liquid stream rich in heavy hydrocarbons (203) .

[00072] In a similar way to the various modalities of the first group of modalities represented in Figures 1(d)-(f), in the modalities of the second group of modalities where a separation column (30) is used, it is possible to obtain the gas from extraction to the separation column from a variety of sources, making it again possible to recover through the separation column a portion of the gas generated during the regeneration of the bed or beds of the adsorption system (40). These variations are further illustrated in Figures 2(c) and (d).

[00073] Thus, with reference to Figure 2(c), although it is preferable that the extraction gas (or at least a portion thereof) supplied to the separation column (30) is a stream of natural gas (209) taken from the natural gas feed stream (100) upstream of the liquefaction device (90) (as also illustrated in Figure 2(a)), various additional and/or alternative sources are available. For example, the extraction gas may additionally or alternatively comprise one or more of: a portion (219) of the heated natural gas stream depleted of heavy hydrocarbons (205) coming from the heat-saving exchanger (10); a portion (208) of the natural gas stream poor in heavy hydrocarbons (206) originating from the temperature swing adsorption system (40) (in which case only a portion (107) of said natural gas stream poor in heavy hydrocarbons ( 106) is then cooled in the heat-saving exchanger (10) and sent to the liquefaction device (90) for liquefaction); or a flash or boil gas (111, 112) obtained from the processing or storage of the LNG stream (110), for example in the LNG storage unit (91). Such supplemental/alternative sources of extraction gas will typically require compression before being used as the extraction gas (e.g., in compressors 75 or 92, as depicted in Figure 2(c)).

[00074] With reference to Figures 2(c) and (d), the adsorption system may, for example, comprise one, two, or more, beds (40A and 40B), arranged and operated in any of the modes as described above with reference to Figure 1(d)-(f), with a regeneration gas being passed through said bed during regeneration thereof and part of the gas generated during regeneration of the bed or beds being recovered through the separation column . In particular, the regeneration gas may comprise a portion (120) of natural gas poor in heavy hydrocarbons (106), obtained from the exit of the bed (40A) undergoing the adsorption step, or a stream (111) of flash gas. or boiling. The desorbed gas stream (121) leaving the bed or beds being regenerated (40B) can then be cooled and partially condensed in a cooler (60), and separated into its phases, in a phase separator (70) in the form of a liquid condensate stream (124) containing most of the heavy hydrocarbons, and a natural gas vapor stream (125).

[00075] As shown in Figure 2(c), the recovered natural gas vapor stream (125) can then be compressed again in a compressor (50) and cooled in an additional cooler (80), and then recycled by being reintroduced into the separation column (30) at a location downstream of the natural gas supply stream (102), thus providing yet another additional or alternative form of extraction gas. The cooler after the compressor (50) is optional and can be used to control the temperature of the recovered natural gas stream (125) entering the separation column. Alternatively, as shown in Figure 2(d), the recovered natural gas vapor stream (125) can be recovered by being recycled to the natural gas feed stream (100), for example, upstream of a gas compressor. reinforcement of the supply gas (51) . Between the feed gas boost compressor (51) and the heat-saving exchanger (10), there may be various equipment (generally indicated as unit 55) such as, for example, a dryer, cooler, etc.

Figures 3(a)-(d)

[00076] In the third group of embodiments, represented in Figures 3(a)-(d), the adsorption system is upstream of the gas-liquid separation system, such that the adsorption system processes the natural gas feed stream (from which heavy hydrocarbons must be removed) to produce a stream of heavy hydrocarbon-depleted natural gas, and the gas-liquid separation system processes at least a portion of a stream of heavy hydrocarbon-depleted natural gas coming from the system of adsorption to produce the desired natural gas stream poor in heavy hydrocarbons.

[00077] More specifically, in the third group of embodiments the natural gas feed stream passes through the one or more beds of the adsorption system to adsorb heavy hydrocarbons from it, thus producing a natural gas stream poor in heavy hydrocarbons. At least a portion of the natural gas stream depleted of heavy hydrocarbons is cooled and then introduced into the gas-liquid separation system and separated as a natural gas vapor stream, which is further depleted of heavy hydrocarbons (thus providing the desired stream of natural gas poor in heavy hydrocarbons), and a liquid stream rich in heavy hydrocarbons. Preferably, the heavy hydrocarbon-depleted natural gas stream or portion thereof is cooled and the heavy hydrocarbon-depleted natural gas stream is liquefied in a natural gas liquefaction device, the heavy hydrocarbon-depleted natural gas stream or portion thereof being introduced at a hot end of the liquefaction device and extracted from an intermediate location of the liquefaction device, and the heavy hydrocarbon-poor natural gas stream is introduced at an intermediate location of the liquefaction device and extracted from a cold end of the liquefaction device. liquefaction.

[00078] The beds of the adsorption system in the third group of modalities must be larger than the beds of the adsorption system in the first and second groups of modalities (described in Figures 1(a)-(f) and Figures 2(a) -(d)), because, in the first and second groups of embodiments, the column of the gas-liquid separation system removes most of the heavy hydrocarbons in the natural gas feed stream. In other words, for the same size of the adsorber bed, the methods and equipment according to the first and second groups of embodiments (described in Figures 1(a)-(f) and Figures 2(a)-(d) ) can tolerate higher concentrations of heavy hydrocarbons in the natural gas feed, and offer better operational flexibility if the natural gas source changes or the concentration of heavy hydrocarbons fluctuates over a wide range. The smaller adsorption beds used in the first and second groups of embodiments also mean that these embodiments have lower requirements with respect to the use of regeneration gas and lower energy costs with respect to the compression of the feed gas. However, embodiments of the third group of embodiments (as depicted in Figures 3(a)-(d)) do not require a heat-saving exchanger to recover refrigeration from the vapor stream obtained from the gas-liquid separation column. thus providing savings in terms of investment costs.

[00079] Referring to Figure 3(a), in one embodiment a methane-rich natural gas feed stream (100) is introduced into an adsorption system (40), which again comprises one or more adsorbent beds selective to hydrocarbon components. of the natural gas stream, the natural gas feed stream (100) being passed through one or more of said beds to adsorb heavy hydrocarbons therefrom, thereby producing a natural gas stream depleted of heavy hydrocarbons (301). As described above in connection with the embodiments described in Figures 1 and 2, where the absorption system (40) comprises a plurality of beds, these may be arranged in series and/or in parallel, and again the heavy hydrocarbons adsorbed by the ) adsorbent(s) can then be removed in an adsorbent regeneration step (not shown in Figure 3(a)).

[00080] At least a portion (302) of the heavy hydrocarbon-poor natural gas stream (301) is then introduced into the hot end of a natural gas liquefaction device (90), is cooled in the hot stage of the liquefaction device , being extracted from an intermediate location of the liquefaction device as a cooled stream of natural gas depleted of heavy hydrocarbons (303). This cooled stream (303) exiting the intermediate position of the liquefaction device (90) may be a partially condensed stream (that is, it may have been cooled and partially condensed in the hot stage of the liquefaction device). Alternatively, the cooled stream (303) exiting the intermediate position of the liquefaction device (90) may also be reduced in pressure (e.g., using a J-T type valve, not shown) in order to further cool and condense. partially the current. Again, although the liquefaction device is described in Figures 3(a)-(d) as a single unit with two cooling stages, it is equally the case that the liquefaction device may comprise more cooling stages, and that the device liquefaction process may comprise more than one unit, arranged in series, with the cooling stages being distributed between the units.

[00081] The natural gas stream depleted in heavy hydrocarbons, cooled and partially condensed (303), is introduced at the top of the separation column (30) where it is separated in the form of a natural gas vapor stream (305) extracted from the top of the column which is further depleted of heavy hydrocarbons (this stream being the desired heavy hydrocarbon-poor natural gas stream), and a liquid rich in heavy hydrocarbons (304) removed from the bottom of the column. An extraction gas is again introduced into the separation column in its lower part, the separation column comprising one or more separation stages separating the feed locations of the natural gas feed stream and the extraction gas. Extraction gas can come from any of a variety of different sources; but, the embodiment represented in Figure 3(a), comprises: a portion (306) of heavy hydrocarbon-depleted natural gas taken from the heavy hydrocarbon-depleted natural gas stream (301) before the remainder (302) of said stream being cooled and partially condensed in the natural gas liquefaction device (90); and/or a natural gas stream (307) taken from the natural gas supply stream (100) before processing the latter in the adsorption system (40).

[00082] The heavy hydrocarbon-poor natural gas stream (305) obtained from the top of the separation column is then returned to an intermediate location of the natural gas liquefaction device (preferably at the same intermediate location as the intermediate location from which the cooled and partially condensed heavy hydrocarbon-depleted natural gas stream (303) is extracted) and cooled and liquefied in a cold stage (or colder stages) of the liquefaction device to provide a stream of LNG (110 ) removed from the cold end of the liquefaction device.

[00083] As with the first and second groups of embodiments, in the third group of embodiments a phase separator can be used in place of the separation column, which saves costs, but increases the loss of methane in the hydrocarbon-rich liquid stream. heavy (304) .

[00084] Thus, referring now to Figure 3(b), in an alternative embodiment a phase separator (31) is used (instead of the separation column used in the embodiment represented in Figure 3 (a)), to separate the current from natural gas depleted of heavy hydrocarbons and partially condensed (303), in the form of natural gas vapor stream (305) further depleted of heavy hydrocarbons (the desired natural gas stream poor in heavy hydrocarbons), extracted from the top of the phase separation column, and a liquid rich in heavy hydrocarbons (304), extracted from the bottom of the column. As described above regarding the operation of the phase separator depicted in Figure 1(b), the phase separator (31) does not contain any separation stages or make use of an extraction gas, and thus, in this embodiment, no extraction gas is generated or used.

[00085] Similar to the various embodiments of the first group of embodiments represented in Figures 1(d)-(f), in the embodiments of the third group of embodiments where a separation column (30) is used it is again also possible to recover through the separation column part of the gas generated during the regeneration of the bed or beds of the adsorption system (40).

[00086] The desorbed gas stream (121) leaving the bed or beds that is regenerated (40B) can then be cooled and partially condensed in a cooler (60), and separated into phases in a phase separator (70) in the form of a liquid condensate stream (124), containing most of the heavy hydrocarbons, and a natural gas vapor stream (125).

[00087] Thus, with reference to Figures 3(c) and (d), the adsorption system may, for example, comprise one, two, or more beds (40A and 40B), arranged and operated in any of the modes as above. described with reference to Figures 1(d)-(f), with a regeneration gas being passed through said bed during its regeneration and part of the gas generated during the regeneration of the bed or beds being recovered through the separation column. In particular, the regeneration gas may comprise a portion (320) of the heavy hydrocarbon-poor natural gas stream (301), obtained from the exit of the bed (40A) undergoing the adsorption step, or a stream (111) flash or boil gas. The desorbed gas stream (321) leaving the bed or beds that is regenerated (40B) may then be cooled and partially condensed in a cooler (60), and separated into phases in a phase separator (70) in the form of a stream. of liquid condensate (323), containing most of the heavy hydrocarbons, and a natural gas vapor stream (324).

[00088] As shown in Figure 3(c), the recovered natural gas vapor stream (324) can then be compressed again in a compressor (50) and cooled in an additional cooler (80), and then recycled by being introduced into the separation column (30) at a location downstream of the heavy hydrocarbon-poor natural gas stream (303), thus providing yet another additional or alternative source of extraction gas (326). The cooler after the compressor (50) is optional and can be used to control the temperature of the recovered natural gas stream (324) that enters the separation column. The compressor (50) is also optional and may not be necessary if the adsorption system is regenerated at a pressure that is higher than the pressure at the bottom of the column. In another variation, the phase separator (70) can also be omitted, such that the entire cooled stream of desorbed gas (321) leaving the cooler (60) is sent to the separation column. As also illustrated in Figure 3(c), the separation column (30) may comprise at least two separation stages such that there are separation stages both above and below the point of entry of the recovered natural gas stream (324) into the of the separation column, and extraction gas to the separation column (30) may also be supplied by use of a reboiler (95) at the bottom of the column to reboil a portion of the heavy hydrocarbon-rich liquid stream (304) obtained from the bottom of the separation column.

[00089] Alternatively, as shown in Figure 3(d), the recovered natural gas vapor stream (324) can be recycled to the natural gas supply stream (100), for example, upstream of a gas compressor. reinforcement of the supply gas (51) . Between the feed gas boost compressor (51) and the heat-saving exchanger (10), there may be various equipment (generally indicated as unit 55), such as, for example, a dryer, cooler, etc. As also illustrated in Figure 3(d), flash gas or boil gas can again, additionally or alternatively, also be used as extraction gas (112) for the separation column (30).

EXAMPLES

[00090] In order to demonstrate the effects of using, in accordance with the present invention, an AOT-type system and a gas-liquid separation system in combination to remove heavy hydrocarbons from a natural gas stream, the performance of the modalities represented in Figures 1(a), 1(e), 2(a), 2(b), 2(c), 3(a), 3(b) and 3(c) in the removal of heavy hydrocarbons from a natural gas stream was compared with the performance of an existing art process (not according to the present invention) that uses only a washing column to remove heavy hydrocarbons from the natural gas stream. In the first run using the traditional process (wash column only), the operating conditions used for the wash column may lead to a risk of drying out of the wash column (and resulting failure of the hydrocarbon removal process). Therefore, a second run using the traditional process (separation column only) was also performed, using different operating conditions (i.e., a cooler column temperature) that prevented any risk of column drying. Data for all runs, i.e., both those that employed the aforementioned embodiments of the present invention and those that employed the existing art process (wash column only), were generated using the ASPEN™ Plus software (© Aspen Technology, Inc.) and an in-house simulation tool, SIMPAC (a detailed adsorption process simulator that considers multicomponent adsorption isotherms, multiple mass transfer modes, numerous adsorbent layers, and general process flowcharts - more details on this simulator are provided in Kumar et al., Chemical Engineering Science, Volume 49, Number 18, pages 3115-3125).

[00091] The starting composition of the natural gas feed stream that was used (which was the same for all cases) is given below, in Table 1, and the composition of the product stream (i.e., the gas stream desired natural stream to be heavy hydrocarbon-poor, marked in Table 2 as "Heavy hydrocarbon-poor hydrocarbon stream") that was obtained from each embodiment (i.e., from each of the embodiments described in Figures 1(a), 1( e), 2(a), 2(b), 2(c), 3(a), 3(b) and 3(c)) and from the traditional process (wash column only) (both runs) is presented in Table 2. In Table 2, the first run employing the existing technique (only washing column) where there was a risk of the column drying out, is indicated by the notation "tray can dry", and the second run employing the process of the existing technique (washing column only), where this risk was removed, is indicated by the note "no tray drying".

[00092] Table 2 also lists: the operating conditions of the gas-liquid separation system (i.e., temperature and pressure of the washing column/separation column/phase separator vessel); the flow rate of the liquid rich in heavy hydrocarbons obtained from the gas-liquid separation system as a percentage of the flow rate of the natural gas stream fed to said system (designated in the table as "LPG as % of feed"); and the total flow of LNG produced by each run using the existing art process (designated in the table as "relative LPG production"). With reference to the data given in Table 2, as is well known in the art the letter E, when used as part of a number means exponent - thus, for example, in Table 2, the number 9.9E-01 refers to 9. .9x1o'1, or 0.99.

[00093] As can be seen from the data in Table 2, embodiments according to the present invention were able to effectively remove heavy hydrocarbons from the natural gas stream and provide increased LNG production compared to those provided by the already existing technique (wash column only), despite the gas-liquid separation system in the embodiments of the present invention being operated at higher temperatures or at higher pressures (thus consuming less energy) than the temperature and pressure of the wash column in the existing art process (even in the existing art process run where the washing column was operated at a temperature at risk of column drying).

[00094] These results are also shown in Figure 4, in which the relative LNG production (i.e., the total flow rate of LNG produced by each run, expressed as a fraction of the best total LNG production flow rate obtained using the existing technique) is plotted against the LPG flow as a % of the feed stream (i.e. the flow rate of the heavy hydrocarbon-rich liquid obtained from the gas-liquid separation system as a percentage of the flow rate of the natural gas stream fed to the mentioned system). As again shown, embodiments according to the present invention provide improved LNG production rates compared to the prior art process, even where the prior art process is carried out under conditions of risk of column drying, and These benefits are even more notable in comparison to those process runs of existing art which were carried out under operating conditions that prevented any risk of column drying (i.e. sufficiently high flow of LPG as a % of the feed flow, as provided by operating the wash column at lower temperatures to increase the amount of liquid produced rich in heavy hydrocarbons).Table 1 - Feed composition

[00095] It will be noted that the invention is not restricted to the details described above with reference to the preferred embodiments, but that numerous modifications and variations can be made without departing from the spirit or scope of the invention as defined in the claims set forth below.

Claims (11)

1. METHOD OF REMOVING HEAVY HYDROCARBONS FROM A NATURAL GAS FEED STREAM, wherein the heavy hydrocarbons are one or more hydrocarbons selected from the group consisting of aliphatic hydrocarbons having six or more carbon atoms in total and aromatic hydrocarbons, the method characterized by comprising the steps of: cooling the natural gas supply stream; introducing the natural gas feed stream into a gas-liquid separation system and separating the cooled natural gas feed stream into a natural gas vapor stream depleted of heavy hydrocarbons and a liquid stream enriched in heavy hydrocarbons; heating the vapor stream of natural gas depleted of heavy hydrocarbons; passing at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream through the one or more adsorbent beds of an adsorption system to adsorb heavy hydrocarbons therefrom, thereby producing the heavy hydrocarbon-depleted natural gas stream; and cooling at least a portion of the heavy hydrocarbon-depleted natural gas stream to produce a chilled heavy hydrocarbon-depleted natural gas stream, and wherein the heavy hydrocarbon-depleted natural gas vapor stream is heated and at least a portion of the heavy hydrocarbon-poor natural gas stream is cooled in a heat-saving exchanger (10) through indirect thermal exchange between the heavy hydrocarbon-depleted natural gas vapor stream and at least a portion of the heavy hydrocarbon-poor natural gas stream . 2. Method according to claim 1, characterized in that the gas-liquid separation system comprises a separation column (30) or a phase separator (31). 3. Method according to claim 1, characterized in that the method is also a method for producing a stream of liquefied natural gas, and which further comprises liquefying at least a portion of the cooled heavy hydrocarbon-poor natural gas stream to produce the liquefied natural gas stream. 4. Method according to claim 3, characterized in that the natural gas feed stream is cooled and at least a portion of the cooled natural gas stream poor in heavy hydrocarbons is liquefied in a liquefaction device (90), the stream of natural gas feed is introduced into a hot end of the liquefaction device (90) and extracted from an intermediate position of the liquefaction device (90), and the cooled natural gas stream poor in heavy hydrocarbons is introduced into an intermediate position of the liquefaction device (90). liquefaction (90) and extracted from a cold end of the liquefaction device (90). 5. Method according to any one of claims 1 to 4, characterized in that the gas-liquid separation system is a separation column (30), the method further comprising introducing an extraction gas into the separation column (30 ) at a location below the location where the cooled natural gas feed stream is introduced into the separation column (30). 6. Method according to claim 5, characterized in that the extraction gas comprises one or more gases selected from the group comprising natural gas taken from the natural gas feed stream before said stream is cooled and introduced into the column separation (30); a portion of the heavy hydrocarbon-poor natural gas stream that was heated in the heat-saving exchanger; a portion of the natural gas stream depleted of heavy hydrocarbons; a gas obtained from boiling all or part of a liquid stream rich in heavy hydrocarbons; and a flash gas or obtained as a vaporizate of a liquefied natural gas. 7. Method according to any one of claims 1 to 6, characterized in that the adsorption system is a temperature swing adsorption system (40), and the method additionally comprises regenerating the one or more beds of the adsorption system by temperature oscillation (40) by the passage of a gas, selected from a portion of the natural gas stream poor in heavy hydrocarbons or from a flash gas or obtained as a vaporized from a liquefied natural gas, through one or more beds, the temperature of the one or more beds during regeneration being higher than the temperature of the one or more beds during adsorption of heavy hydrocarbons from the heavy hydrocarbon-depleted natural gas vapor stream or a portion thereof. 8. Method according to claim 7, characterized in that the method additionally comprises cooling and separating into liquid and vapor phases the gas obtained from the one or more beds of the adsorption system by temperature oscillation (40) during the regeneration of said one or more beds, and recycling the vapor phase in a natural gas supply stream before introducing the same into a gas-liquid separation system. 9. Method according to claim 7, characterized in that the gas-liquid separation system is a separation column (30), and the method additionally comprises cooling and separating into liquid and vapor phases the gas obtained from the one or more beds of the temperature swing adsorption system (40) during the regeneration of said one or more beds, and introducing the vapor phase as an extraction gas into the separation column (30) at a location below the location where the natural gas feed stream is introduced into the separation column (30). 10. Method according to any one of claims 1 to 9, characterized in that the natural gas feed stream is poor in aliphatic hydrocarbons with 3 to 5 carbon atoms in total, and/or is poor in aliphatic hydrocarbons with 2 to 5 carbon atoms in total. 11. EQUIPMENT FOR REMOVING HEAVY HYDROCARBONS FROM A NATURAL GAS SUPPLY STREAM AND PRODUCING A LIQUEFIED NATURAL GAS STREAM, for carrying out the method of claim 1, in which the heavy hydrocarbons are one or more hydrocarbons selected from the group consisting of aliphatic hydrocarbons having six or more carbon atoms in total and aromatic hydrocarbons, the equipment being characterized by comprising: a gas-liquid separation system for receiving and separating the natural gas feed stream into a gas vapor stream natural depleted of heavy hydrocarbons and a liquid stream enriched in heavy hydrocarbons; an adsorption system in connection by continuous flow communication with the gas-liquid separation system, for receiving at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, and comprising one or more adsorbent beds for adsorbing the hydrocarbons weighing at least a portion of the heavy hydrocarbon-depleted natural gas vapor stream, thereby producing a heavy hydrocarbon-depleted natural gas stream; a heat-saving exchanger (10) for heating at least a portion of the heavy hydrocarbon-depleted natural gas stream, before said stream or portion thereof is passed through one or more beds of the adsorption system, and cooling at least one portion of the heavy hydrocarbon-poor natural gas stream through indirect heat exchange between the heavy hydrocarbon-depleted natural gas vapor stream and at least a portion of the heavy hydrocarbon-poor natural gas stream, and a liquefaction device (90 ) in connection by continuous flow communication with the adsorption system and the gas-liquid separation system, to receive and cool the natural gas feed stream before said stream is introduced into the gas-liquid separation system, and to receive and liquefying at least a portion of the heavy hydrocarbon-poor natural gas stream to produce the liquefied natural gas stream, the liquefaction device (90) being configured so that the natural gas feed stream is received at a hot end of the liquefaction device (90) and extracted from an intermediate position of the liquefaction device (90), and at least a portion of the heavy hydrocarbon-poor natural gas stream is received at an intermediate position of the liquefaction device (90) and extracted from a cold end of the liquefaction device (90).