Apparatus and process for removal of heavy hydrocarbons from feed gas

Abstract

To provide an apparatus and a process for removal of heavy hydrocarbons from feed gas.SOLUTION: An apparatus and a process for removal of heavy hydrocarbons (e.g., hydrocarbons that comprise five or more carbon atoms such as pentane and hexane) from a feed (e.g., a feed comprising methane and impurities) can include a scrubber column and a stabilizer column arranged such that a portion of a first stream output from the stabilizer column is fed to the scrubber column to function as a reflux stream. Embodiments are provided in which the scrubber column produces a stream comprising mostly methane (e.g., over 85 mole percent methane) and reduced heavy hydrocarbons so that reduced operational costs and improved operational flexibility can be realized in downstream natural gas liquefaction operation.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to processes and systems for treating gas feeds containing methane (e.g., natural gas) to remove impurities from the feed (e.g., removing heavy hydrocarbons having 5 or more carbons in the gas feed). [Background technology]

[0002] Liquefied natural gas (LNG) includes methane (CH4) that has been cooled and liquefied to a liquid state. Examples of systems and processes involving LNG can be seen in U.S. Patent Application Publication Nos. 2022 / 0178609 and 2016 / 0216030, and U.S. Patent No. 11,499,775. Summary of the Invention

[0003] Cryogenic natural gas liquids (NGL) recovery plants and LNG plants are often configured to remove some of the heavier hydrocarbon components from a natural gas feed that may freeze during the cryogenic process to liquefy the methane in the feed. Such conventional systems often provide a feed containing methane for liquefaction processing that may require significant compression, which may incur significant operating costs for the liquefaction process and may limit how such liquefaction processes may be deployed and configured. Described herein are embodiments of a process for feed gas processing and an apparatus for feed gas processing that may enable more effective removal of heavy hydrocarbons from the feed while reducing operating costs and providing improved operating flexibility for downstream natural gas liquid liquefaction processing of the feed.

[0004] The apparatus and process embodiments described herein can be configured such that the scrub column can be operated at a preselected pressure, which can be selected independently of the cooling requirements of the precooling via the feed precooling heat exchanger. The embodiments can be adapted such that the vapor stream output from the scrub column, which comprises primarily methane, can be fed to a liquefaction device (e.g., a liquefier, etc.) at high pressure, thereby reducing the power requirements for downstream liquefaction of the output vapor stream. The process and apparatus embodiments can be configured such that the feed is at ambient temperature (e.g., 0° C. to 40° C., 20° C. to 40° C., etc.).

[0005] In some embodiments, the feed containing methane and heavy hydrocarbon impurities is fed to a heat exchanger before being fed to the scrub tower. The scrub tower can be configured to output a first vapor stream containing methane and a second vapor stream having heavy hydrocarbons. The second stream can be fed to a stabilizer tower, which can be configured to output the first stream to form a reflux stream that can be fed to the scrub tower and the second feed having heavy hydrocarbons to separate the heavy hydrocarbons from the feed. The first vapor stream containing methane can be passed through a heat exchanger to help cool and / or form the reflux stream provided through the stabilizer tower before the formed reflux stream is fed to the scrub tower.

[0006] In some embodiments, a reflux accumulator vessel (e.g., a reflux accumulator drum) can be provided between the heat exchanger and the scrub column to hold the formed reflux stream and provide an adequate reflux supply to the scrub column pump used to provide reflux to the scrub column. In some embodiments, the reflux accumulator vessel can be positioned and configured to help protect the scrub pump to avoid pump cavitation. In the same or other embodiments, the stabilizer column and the scrub column can be positioned and configured such that the scrub column can operate at a pressure in the range of 45 bara to 65 bara and the stabilizer column can operate at a pressure in the range of 15 bara to 30 bara. In other embodiments, other pressure ranges for the stabilizer column and / or scrub column can also be utilized such that the stabilizer column operates at a different operating pressure range that is lower than the operating pressure range of the scrub column. The vapor stream output from the scrub column may be composed primarily of methane (e.g., 80 mole percent (mol%) methane to 95 mol% methane, at least 85 mol% methane to less than 100 mol% methane, at least 75 mol% methane, at least 90 mol% methane, etc.) and may be at high pressure.

[0007] In a first aspect, an apparatus is provided for removing heavy hydrocarbon impurities from a feed comprising methane gas and heavy hydrocarbons having at least 5 carbon atoms. The apparatus may include a scrub tower positioned and configured to receive the feed and output a first scrub tower stream and a second scrub tower stream. The second scrub tower stream may include heavy hydrocarbons. The apparatus may also include a stabilizer tower positioned downstream of the scrub tower to receive the second scrub tower stream. The stabilizer tower may be configured to output a first stabilizer tower stream and a second stabilizer tower stream. The second tower stabilizer stream may include heavy hydrocarbons. The scrub tower may be configured such that a portion of the first stabilizer tower stream is fed to the scrub tower to provide scrub tower reflux.

[0008] In some embodiments, the scrub column may be operated at high pressure to provide a treated feed gas at high pressure and provide the treated feed to a downstream LNG or NGL plant, resulting in improved operational flexibility and reduced compression duty required at the downstream plant. Some embodiments may be integrated into an LNG or NGL plant or as a separate pre-treatment facility that may provide a treated feed for such a plant.

[0009] Some embodiments may be adapted so that an expander is not utilized to expand the feed to the scrub column. Some embodiments may be configured such that the operating pressure range of the scrub column is higher than the stabilizer column operating pressure range.

[0010] In a second aspect, the apparatus can include a reflux accumulator vessel configured to receive a portion of the first stabilizer stream supplied to the scrub column, store a scrub column reflux, and supply the scrub column reflux to the scrub column.

[0011] In a third aspect, the apparatus can include a heat exchanger positioned to cool at least a portion of the feed before the feed is fed to the scrub tower, receive a first scrub tower stream from the scrub tower, and / or cool a portion of a first stabilizer tower stream that may be fed to the scrub tower to form a scrub tower reflux stream that may be fed to the reflux accumulator vessel. For example, the heat exchanger can be positioned to cool a first portion of the feed before the feed is fed to the scrub tower, receive a first scrub tower stream from the scrub tower, and cool a portion of a first stabilizer tower stream that may be fed to the scrub tower to form a scrub tower reflux stream that is fed to the scrub tower to provide the scrub tower reflux.

[0012] In a fourth aspect, the scrub column of the apparatus can be positioned such that the second portion of the feed or the third portion of the feed can pass through the side reboiler to cool that portion of the feed and heat the liquid from the scrub column received by the side reboiler to form stripping steam. The side reboiler can be positioned to output the stripping steam to the scrub column. The side reboiler can be positioned and arranged such that the second portion of the feed or the third portion of the feed output from the side reboiler can be fed to the scrub column. For example, in some embodiments, the heat exchanger and the scrub column can be positioned such that the second portion of the feed or the third portion of the feed output from the side reboiler is combined with the first portion of the feed and fed to the scrub column.

[0013] In a fifth aspect, the apparatus can include a pump positioned to drive a stream of scrub tower reflux to the scrub tower. For example, an embodiment can include a reflux accumulator vessel positioned to receive a portion of the first stabilizer stream to be fed to the scrub tower, store the scrub tower reflux, and feed the scrub tower reflux to the scrub tower. Such an embodiment can also include a pump positioned to drive a stream of scrub tower reflux from the reflux accumulator vessel to the scrub tower. In such an embodiment, the stabilizer tower can be configured to operate at a preselected stabilizer tower operating pressure range, and the scrub tower can be configured to operate at a preselected scrub tower operating pressure range that is greater than the preselected stabilizer tower operating pressure range.

[0014] In a sixth aspect, the apparatus can include a phase separator positioned to receive the first stabilizer tower stream and to output a vapor stream and a liquid stream. The phase separator can be positioned to feed a portion of the liquid stream and the vapor stream to a scrub tower to form a scrub tower reflux for providing reflux to the scrub tower.

[0015] In some embodiments, the heat exchanger can be positioned to receive the vapor stream from the phase separator and a first portion of the liquid stream from the phase separator. The portion of the first stabilizer tower stream that is fed to the scrub tower as scrub tower reflux can include the vapor stream from the phase separator and the first portion of the liquid stream from the phase separator. The heat exchanger can be configured and positioned to cool the first portion of the feed before the feed is fed to the scrub tower and to cool the first portion of the vapor stream and the liquid stream to form a scrub tower reflux stream to provide scrub tower reflux for feeding to the scrub tower.

[0016] Also, in some embodiments, a reflux accumulator vessel can be positioned to receive the scrub tower reflux stream output from the heat exchanger, store the scrub tower reflux, and provide the scrub tower reflux to the scrub column and / or a pump positioned to drive the scrub tower reflux stream from the reflux accumulator vessel to the scrub column. In such or other embodiments, the stabilizer column can be configured to operate at a preselected stabilizer column operating pressure range, and the scrub column can be configured to operate at a preselected scrub column operating pressure range that is greater than the preselected stabilizer column operating pressure range.

[0017] In the seventh aspect, the device of the first aspect can include one or more features of the second aspect, the third aspect, the fourth aspect, the fifth aspect, and / or the sixth aspect. It should be understood that an embodiment of the device can thus include other elements or features of different exemplary embodiments. For example, an embodiment can include one or more exemplary features of the exemplary embodiments discussed herein.

[0018] In an eighth aspect, a process is provided for treating a feed gas comprising methane and heavy hydrocarbons having at least 5 carbon atoms. An embodiment of the process can include providing a feed to a scrub tower operating at a preselected scrub tower operating pressure range, and outputting a first scrub tower stream and a second scrub tower stream from the scrub tower. The second scrub tower stream can comprise heavy hydrocarbons.

[0019] The process can also include feeding the second scrub tower stream to a stabilizer tower operating at a preselected stabilizer tower operating pressure range to output a first stabilizer tower stream and a second stabilizer tower stream. The second stabilizer tower stream can include heavy hydrocarbons.

[0020] The process may also include feeding a portion of the first stabilizer tower stream to a scrub tower to provide scrub tower reflux to the scrub tower.

[0021] The apparatus embodiments can be configured to perform or utilize the process embodiments. The process embodiments can be configured such that the treated feed can be provided as a first scrub column stream at high pressure to a suitable downstream plant to reduce the compression load required at the downstream plant and provide improved operational flexibility. The downstream plant can be, for example, an LNG plant or an NGL plant.

[0022] In a ninth aspect, the process may include additional steps. For example, the process may also include feeding the first stabilizer tower stream to a phase separator to form a vapor stream and a liquid stream, feeding a portion of the vapor stream and the liquid stream to a heat exchanger to form a scrub tower reflux, feeding the scrub tower reflux output from the heat exchanger to a reflux accumulator vessel, and feeding the scrub tower reflux from the reflux accumulator vessel to an upper section of the scrub tower. The process may also include feeding the first scrub tower stream as a cooling medium to a heat exchanger to cool a portion of the vapor stream and the liquid stream fed to the heat exchanger to form a scrub tower reflux stream.

[0023] In a tenth aspect, the preselected scrub column operating pressure range can be higher than the preselected stabilizer column operating pressure range. For example, the preselected scrub column operating pressure range can be from 45 bara to 65 bara, and the preselected stabilizer column operating pressure range can be from 15 bara to 30 bara.

[0024] In an eleventh aspect, the process can include splitting the feed into different portions. For example, the process can include splitting the feed into a first portion and a second portion, feeding the first portion to a heat exchanger positioned upstream of a scrub tower, and then mixing the first portion with the second portion and feeding the combined feed to the scrub tower.

[0025] As another example, the process may include splitting a feed into a first portion, a second portion, and a third portion, feeding the first portion to a heat exchanger positioned upstream of a scrub tower before mixing the first portion with the second portion, feeding the combined feed to the scrub tower, and feeding the third portion to a lower section of the scrub tower.

[0026] As yet another example, the process may include splitting a feed into a first portion and a second portion, feeding the first portion to a heat exchanger positioned upstream of a scrub tower, feeding the first portion to the scrub tower, and feeding the second portion to a lower section of the scrub tower.

[0027] As yet another example, the process may include splitting a feed into a first portion, a second portion, and a third portion, supplying the first portion to a heat exchanger positioned upstream of a scrub column, mixing the first portion with the second portion and supplying the combined feed to the scrub column, and supplying the third portion to a side reboiler for forming stripping steam to supply to the scrub column before the third portion is supplied to the scrub column.

[0028] Embodiments of the process may also include other steps related to processing different portions of the split feed. For example, the process may also include mixing the third portion with the second portion and / or the first portion before the first, second, and third portions of the feed are fed to the scrub column.

[0029] In a twelfth aspect, the process of the eighth aspect may include one or more features of the ninth aspect, the tenth aspect, and / or the eleventh aspect. It should be understood, therefore, that an embodiment of the process may include other elements or features of different exemplary embodiments. For example, an embodiment may include one or more exemplary features of the exemplary embodiments discussed herein.

[0030] It should be understood that process and apparatus embodiments can utilize a variety of conduit arrangements and process control elements. Embodiments may utilize sensors (e.g., pressure sensors, temperature sensors, flow sensors, concentration sensors, etc.), controllers, valves, piping, and other process control elements. Some embodiments can utilize, for example, automated process control systems and / or distributed control systems (DCS). A variety of conduit arrangements and process control systems can be utilized to meet a particular set of design criteria.

[0031] Other details, objects, and advantages of the invention, including processes for treating a gas feed comprising methane (e.g., natural gas) to remove impurities from the feed, apparatus for treating a gas feed comprising natural gas to remove impurities from the feed gas, systems for treating a gas feed comprising methane to remove impurities from the feed, and methods of making and using the same, will become apparent from the following detailed description of certain exemplary embodiments. [Brief description of the drawings]

[0032] Exemplary embodiments of the invention include processes for treating a gas feed comprising methane (e.g., natural gas) to remove impurities (e.g., heavy hydrocarbons) from the feed, an apparatus for treating a gas feed comprising natural gas to remove impurities from the feed gas, a system for treating a gas feed comprising methane to remove impurities from the feed, and methods of making and using the same. It should be understood that like reference characters used in the drawings may identify like components.

[0033] [Figure 1] Figure 1 is a block diagram of a first exemplary embodiment of an apparatus for treating a gas feed comprising methane to remove impurities from the feed gas. Figure 1 also illustrates a first exemplary embodiment of a process for treating a gas feed comprising methane to remove impurities from the feed gas. The impurities present in the feed gas being treated can include heavy hydrocarbons (e.g., hydrocarbons having 5 or more carbons, e.g., pentane, hexane, heptane, octane, etc.). [Diagram 2] 2 is a flow chart illustrating an exemplary embodiment of a process for treating a feed gas comprising methane to remove impurities from the feed gas. The exemplary embodiment of the apparatus illustrated in FIG. 1 can be adapted to carry out the exemplary embodiment of the process illustrated in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] FIG. 1 illustrates an exemplary embodiment of an apparatus 1 for treating one or more feeds comprising methane to remove impurities therefrom. The impurities removed may include heavy hydrocarbons having 5 or more carbon atoms (e.g., pentane, hexane, heptane, benzene, etc.). These exemplary embodiments of the apparatus 1 may utilize exemplary embodiments of processes for treating one or more gas feeds comprising methane to remove impurities therefrom. Examples of such processes may be seen from FIGS. 1 and 2.

[0035] The feed 100 may be a completely gaseous feed provided at an initial feed temperature. The initial feed temperature of the feed 100 may be ambient temperature (e.g., 0° C. to 40° C., about 25° C., −5° C. to 40° C., etc.). The feed may be provided via a natural gas pipeline or other feed source 100 for embodiments in which the feed is comprised of natural gas (e.g., methane, CH4). The feed 100 may also include impurities, which may include ethane, propane, butane, and heavy hydrocarbons having 5 or more carbon atoms (e.g., C5+ hydrocarbons such as pentane, isopentane, hexane, benzene, heptane, toluene, octane, etc.). The feed 100 may also include trace amounts of other gases, such as nitrogen and carbon dioxide.

[0036] In some embodiments, the feed 100 may consist primarily of methane. For example, the feed may have, in some embodiments, 75 mole percent (mol%) to 100 mol% methane, 1 mol% to 8 mol% ethane, 0.2 mol% to 3 mol% ethane, and 0.01 mol% to 0.5 mol% butane, and may have 1 mol% to 0 mol% heavy hydrocarbons having 5 or more carbon atoms. The feed may also include 0 mol% to 3 mol% nitrogen, and 0 mol% to 0.1 mol% carbon dioxide. In some embodiments, the feed may also include hydrogen gas and / or other components.

[0037] The feed 100 may be split into multiple portions upstream of the heat exchanger 118, with different portions being routed to the scrub tower 106 and / or the heat exchanger 118. For example, the feed 100 may be split into a first portion 128 that passes through the heat exchanger 118 and receives cooling therein, a second portion 130 that may be split from the first portion upstream of the heat exchanger 118 and passed to the scrub tower 106, and a third portion 132 that may be fed to the scrub tower at a bottom or lower section of the scrub tower 106 as a lower section feed portion 132A.

[0038] In an alternative embodiment (as shown by the dashed lines in FIG. 1 ), the third portion 132 can serve as a heating medium to indirectly heat the fluid in the scrub column 106 that passes through the side reboiler 150 and is fed to the side reboiler 150, thereby vaporizing the fluid so that it can be fed as steam from the side reboiler 150 to the scrub column 106 (as shown by the dashed lines in FIG. 1 ). If the third portion passes through the side reboiler 150, the third portion may be output from the side reboiler 150 and mixed with the second portion 130 and / or the first portion 128 for feeding to the scrub column 106, or it may be output from the side reboiler 150 and fed from the side reboiler 150 to the scrub column 106.

[0039] The first, second, and third portions of the feed 100 can be divided to include different flow rates of the feed. For example, the first portion can be the largest of the first, second, and third portions, and the second portion can be smaller or larger than the third portion. For example, the first portion can be 50%-80% of the feed 100. The second portion 130 can be 45%-5% of the feed 100, and the third portion 132 can be 45%-5% of the feed.

[0040] The first portion 128 may pass through the heat exchanger 118 to be cooled to a preselected first portion cooling temperature that is within a preselected first portion scrub tower feed temperature range. An example of the preselected first portion scrub tower feed temperature range may be −20° C. to −50° C. or another suitable temperature range. After the cooled first portion 128 is output from the heat exchanger 118, it may be fed to an upper section or an intermediate section of the scrub tower 106. In some embodiments, the first portion 128 may be mixed with the second portion 130 before the combined first and second portions are fed to the scrub tower 106. In other embodiments, the first portion 128 may be fed to the scrub tower 106 via a separate feed conduit, and the second portion 130 may also be fed to the scrub tower 106 via a separate feed conduit.

[0041] The second portion 130 may be split from the first portion 128 and then fed to an upper or middle section of the scrub tower 106 via a second portion feed conduit connected between the feed conduit and the scrub tower 106. The second portion 130 may optionally be cooled via cooler 102 to a preselected second portion scrub tower feed temperature within a preselected second portion scrub tower feed temperature range before the second portion 130 is fed to the scrub tower 106. An example of the preselected second portion scrub tower feed temperature range may be −15° C. to −45° C. or another suitable temperature range.

[0042] The second portion cooler 102, which may be positioned to cool the second portion (as shown by the dashed line in FIG. 1), may be a chiller, a mechanical chiller, or other type of cooler that may utilize a stream of coolant 134A as a cooling medium to cool the second portion 130. This coolant 134A may be, for example, liquid propane from a downstream LNG plant, a mixed coolant from a downstream LNG plant, a cryogenic gaseous methane or nitrogen stream from a downstream LNG plant, or other type of coolant or cooling medium that may be output from a downstream liquefier or LNG plant, or another process gas from another process element (e.g., a waste stream from an air separation unit, etc.).

[0043] In other arrangements, the second partial cooler 102 may not be utilized. For example, the cooling from the heat exchanger 118 provided to the first portion 128, which is then mixed with the second portion 130, may be sufficient to also sufficiently cool the second portion 130, such that the combined feed of the first portion 128 and the second portion 130 is fed to the scrub tower 106 at a suitable scrub tower feed temperature. For example, a cooling medium stream 134B (shown in dashed lines in FIG. 1) may be fed to the heat exchanger 118 as a cooling medium to help sufficiently cool the first portion 128 through the heat exchanger 118, such that the combined stream of the first portion 128 and the second portion 130 formed downstream of the heat exchanger 118 is at a suitable feed temperature for the scrub tower 106.

[0044] Alternatively, cooling can be provided via cooling medium stream 134B fed to heat exchanger 118 and / or first scrub column stream 104 such that second portion 130 of the feed is not formed, and instead only first portion 128 and third portion 132 are formed. In such an arrangement in which second portion 130 is not formed, third portion 132 can be considered a second portion of feed 100 and can be fed to a lower section of the scrub column as lower section feed portion 132A or can be fed to a side reboiler 150 before being fed to scrub column 106 and / or before being mixed with first portion 128 for feeding to scrub column 106.

[0045] The cooling medium 134B stream (shown in dashed lines in FIG. 1 ) can be, for example, liquid propane from an LNG plant, or other type of refrigerant or cooling medium that may be output from a downstream liquefier or LNG plant, or another process gas from another process element (e.g., a waste stream from an air separation unit, etc.). For example, the cooling medium 134B stream can be liquid propane from a downstream LNG plant, a mixed refrigerant from a downstream LNG plant, a cryogenic gaseous methane or nitrogen stream from a downstream LNG plant, or other type of refrigerant or cooling medium that may be output from a downstream liquefier or LNG plant, or another process gas from another process element (e.g., a waste stream from an air separation unit, etc.). Other embodiments can utilize still other sources of refrigerant as the cooling medium 134B.

[0046] Embodiments that may use cooling media 134B from an external source (e.g., other plant processes, liquefiers, etc.) can be adapted to provide cooling without reducing or lowering the scrub column pressure, which can allow the scrub column 106 to operate at a higher pressure to provide a high pressure treated stream 126, which can also help avoid the use of an expander (e.g., expansion of the feed 100) and the pressure reduction associated with the use of an expander.

[0047] The scrub tower 106 receives the first, second, and third portions 128, 130, and 132 of the feed 100, scrubs the feed to remove heavy hydrocarbons from the feed 100, and outputs a first scrub tower stream 104, which may also be considered a treated feed stream 104 or a scrub tower vapor stream 104. The first scrub tower stream 104 may be output from the top of the scrub tower or adjacent to an upper section of the scrub tower 106 as a vapor stream composed entirely of gas. The scrub tower 106 may also output a second scrub tower stream 108 at the bottom of the scrub tower or adjacent to the bottom (e.g., at a lower section of the scrub tower 106).

[0048] The scrub column 106 may include a reboiler 136 positioned to remove methane and ethane from the second scrub column stream 108 of the scrub column 106 or from the bottom of the scrub column 106, such that the removed methane and ethane may be returned to the scrub column 106 and the second stream 108 may be output as a second scrub column stream 108 comprising primarily heavy hydrocarbons with relatively small amounts of methane and ethane therein. In some embodiments, the second scrub column stream 108 may comprise greater than 0 mol% methane and less than 20 mol% methane, and greater than 0 mol% ethane and less than 20 mol% methane. The remaining portion of the second scrub column stream 108 may comprise heavy hydrocarbons, propane, butane, and other impurities from the feed 100. In some embodiments, the second scrub column stream 108 may comprise between 30 mol% and 50 mol% heavy hydrocarbons, or between 20 mol% and 40 mol% heavy hydrocarbons.

[0049] As mentioned above, scrub column 106 may also include an optional side reboiler 150, which may utilize third portion 132 as a heating medium to vaporize condensate or liquid from the lower section of scrub column 106 before supplying it back to scrub column 106 for use therein as stripping steam.

[0050] Scrub column 106 can be arranged and configured to operate within a preselected scrub column pressure range. This pressure range can be selected to provide first scrub column stream 104 at high pressure. In some embodiments, the preselected scrub column pressure range can be between 45 bara and 65 bara. Other embodiments may utilize another suitable pressure range for the preselected scrub column pressure range to meet a particular set of design criteria.

[0051] The second scrub tower stream 108 may be output from the scrub tower 106 and fed to a stabilizer tower feed cooler 140. The stabilizer tower feed cooler 140 may be positioned between the scrub tower 106 and the stabilizer tower 110 to cool the second scrub tower stream 108 to a preselected stabilizer tower feed temperature. The stabilizer tower feed cooler 140 may be a chiller or heat exchanger that may utilize ambient air or a chilled water cooling medium or other suitable cooling medium to cool the second scrub tower stream 108 to a preselected stabilizer tower feed temperature. In some embodiments, this temperature may be within a temperature range of 0° C. to 30° C. or −5° C. to 40° C.

[0052] The second scrub tower stream 108 can be fed to a stabilizer tower 110 to form a first stabilizer tower stream 111, which can be output adjacent to the top or upper part of the first stabilizer tower 110, and a second stabilizer tower stream 112, which can be output adjacent to the bottom or lower part of the second stabilizer tower 110.

[0053] The stabilizer column 110 can be operated at a preselected stabilizer column pressure range. The preselected stabilizer column pressure range can be selected such that the stabilizer column 110 can output a suitable first stabilizer column stream 111 that is fed to the scrub column 106 as reflux for the scrub column 106. The stabilizer column operating pressure range can be selected to be lower than the operating pressure range of the scrub column 106. In some embodiments, the preselected stabilizer column pressure range can be, for example, 15 bara to 30 bara. Other embodiments may utilize another suitable pressure range for the preselected stabilizer column pressure range to meet a particular set of design criteria.

[0054] In embodiments or implementations where it is desirable to maximize the liquid fraction of the overhead product from stabilizer column 110 (e.g., the flow of stream 114 divided by the flow of stream 116), stabilizer column 110 may be operated at as high a pressure as possible. However, this operating pressure of stabilizer column 110 may be limited by the maximum feasible operating temperature of stabilizer column reboiler 110A to prevent coke formation, since the operating temperature of reboiler 110A may increase with pressure. In some embodiments, this maximum temperature of stabilizer column reboiler 110A may be at or about 200° C. (e.g., 185° C. to 205° C.). However, the maximum operating pressure of the scrub column 110 may depend on the composition of the stabilizer bottoms product (e.g., second stabilizer column stream 112), which may vary based on the composition of the feed 100 and / or the composition of the second scrub column stream 108 fed to the stabilizer column 110. In some embodiments, a stabilizer column 110 operating pressure of 30 bara to 15 bara may often be utilized to help provide a configuration that facilitates maximizing the liquid fraction of the overhead product from the stabilizer column 110. However, other operating pressure ranges may also be utilized in different embodiments based on the expected stabilizer column feed composition and the composition of the second stabilizer column stream 112.

[0055] The stabilizer column 110 may include a reboiler 110A that may be positioned and configured to remove methane and ethane from the stabilizer column 110 or the second stabilizer column stream 112 from the bottom of the stabilizer column 110, such that the removed methane and ethane may be returned to the stabilizer column 110 and the second stabilizer column stream 112 may be output as a stream containing primarily heavy hydrocarbons with relatively small amounts of methane and ethane therein. In some embodiments, the second stabilizer column stream 112 may include 0 mol% methane to 3 mol% methane, and 0 mol% ethane to 3 mol% ethane. The remaining portion of the second stabilizer column stream 112 may include heavy hydrocarbons and may also include trace amounts of other impurities from the feed 100 (e.g., trace amounts of propane, 0 mol% butane to 3 mol% butane, etc.). In some embodiments, the second stabilizer tower stream 112 can include between 100 mol % and 95 mol % heavy hydrocarbons, or between 90 mol % and 100 mol % heavy hydrocarbons.

[0056] The first stabilizer tower stream 111 can include primarily lighter hydrocarbons (e.g., methane, ethane, propane, and butane) or can include only such lighter hydrocarbons. For example, in some embodiments, the first stabilizer tower stream 111 can include 15 mol% to 40 mol% methane, 10 mol% to 40 mol% ethane, 10 mol% to 40 mol% propane, and 5 mol% to 15 mol% butane. Other embodiments can be configured to utilize other component concentration ranges of the lighter hydrocarbons.

[0057] First stabilizer tower stream 111 can be fed to a first stabilizer stream cooling device 142. This cooling device can be an ambient air heat exchanger, a chiller, or other type of suitable cooling device for cooling first stabilizer tower stream 111 to a preselected phase separator feed temperature, which can be within a preselected phase separator feed temperature range. The cooled first stabilizer tower stream 111 can include liquid and gas and can be fed to a phase separator 146, which can output a vapor stream 116 and a liquid stream 113.

[0058] In some embodiments, vapor stream 116 can include 15 mol%-40 mol% methane, 10 mol%-40 mol% ethane, 10 mol%-40 mol% propane, and 5 mol%-15 mol% butane. Liquid stream 113 can include 0 mol%-10 mol% methane, 5 mol%-25 mol% ethane, 15 mol%-40 mol% propane, and 20 mol%-50 mol% butane. Other embodiments can be configured to utilize other component concentration ranges of lighter hydrocarbons for vapor stream 116 and liquid stream 113.

[0059] Liquid stream 113 may be split such that a first portion 114 of the liquid stream is provided to a first heat exchanger 118 and / or a reflux accumulation vessel 120 for use in forming the scrub tower reflux, and a second portion 115 is provided to an upper section of stabilizer tower 110 as a reflux stream for stabilizer tower 110. Pump 144 may be positioned to facilitate providing the first and second portions 114 and 115 of liquid stream 113 to stabilizer tower 110 and reflux accumulator vessel 120.

[0060] The first portion 114 of the liquid stream 113 output from the phase separator 146 may be fed to the heat exchanger 118 along with the vapor stream 116 such that these streams may be distributed together through the heat exchanger 118 and the vapor may be cooled to a liquid form such that the combined vapor stream 116 and the first portion 114 of the liquid stream 113 form the scrub tower reflux output from the heat exchanger 118 as the scrub tower reflux stream 148. The scrub tower reflux stream 148 may include liquid or may be a liquid and may be fed to the reflux accumulator vessel 120 for storage therein and then fed from the reflux accumulator vessel 120 to the top of the scrub column 106 as the scrub tower reflux stream 124. The scrub column reflux feed pump 122 may be configured to facilitate the flow of the scrub column reflux feed stream 124 from the reflux accumulator vessel 120 to the top of the scrub column 106. In some embodiments, the reflux accumulator vessel 120 can be positioned, sized, and configured to help protect the scrub column reflux feed pump 122 to avoid cavitation of the pump.

[0061] The first scrub tower stream 104 may also pass through a first heat exchanger 118 where it acts as a cooling medium. The warmed first scrub tower stream 104 may be output from the first heat exchanger 118 as a treated feed stream 126 for supply to an NGL recovery plant or an LNG plant.

[0062] The treated feedstream 126 may be output at a preselected LNG plant feed temperature or other suitable temperature within a preselected treated feedstream temperature range. In some embodiments, the preselected treated feedstream temperature range may be 0° C. to 40° C., or −10° C. to 25° C., or another suitable range. The treated feedstream 126 may also be at a preselected treated feedstream pressure within a preselected treated feedstream pressure range. The preselected treated feedstream pressure range may be 50 bara to 60 bara, 40 bara to 65 bara, or another suitable pressure range. The preselected treated feedstream pressure may be a high pressure suitable for supplying the treated feedstream to a downstream LNG plant or liquefaction plant process. Such a high pressure may provide improved downstream operational flexibility and may also allow downstream operations to be conducted more efficiently and at lower cost (e.g., by reducing compression loads and compressor arrangements required for such processing, etc.).

[0063] In other embodiments, cooling medium stream 134B may be provided to cool first scrub tower stream 104 so that it can be output from first heat exchanger 118 as treated feed stream 126 at a lower preselected treated feed stream temperature range (e.g., below −10° C., in the range of −20° C. to −100° C., or another suitable range). Such cooling may be provided such that first scrub tower stream 104 can be cooled in addition to cooling first portion 114 of liquid stream 113 for mixing with vapor stream 116 and first portion 128 of feed.

[0064] It should be understood that conduits, including valves and other conduit elements, may be positioned to facilitate flow of the streams and / or portions of the streams from one element of a process or apparatus to another. For example, a heat exchanger output conduit may be positioned between the heat exchanger 118 and the scrub tower 106 to convey a first portion 128 of the feed output from the heat exchanger 118 to the scrub tower 106. As another example, a second portion conduit and a third portion conduit may be positioned between a feed conduit through which the feed 100 passes and the scrub tower 106 to supply the second and third portions of the feed to the scrub tower 106. As another example, a stabilizer tower feed conduit can be positioned between the stabilizer tower feed cooler 140 and the stabilizer tower 110 to convey the cooled second scrub tower stream 108 from the stabilizer tower feed cooler 140 to the stabilizer tower 110, and there can be a stabilizer tower cooler feed conduit positioned between the scrub tower and the stabilizer tower feed cooler 140 to feed the second scrub tower stream 108 to the stabilizer tower feed cooler 140.

[0065] In yet another example, there can be a first stabilizer tower feed conduit positioned between the first stabilizer stream cooling device 142 and the stabilizer stream 110 to convey the first stabilizer tower stream 111 to the first stabilizer stream cooling device 142. There can also be a phase separator feed conduit positioned between the first stabilizer stream cooling device 142 and the phase separator 146 to feed the cooled first stabilizer tower stream to the phase separator 146. A first vapor stream conduit can be positioned between the phase separator 146 and the heat exchanger 118 to feed the first vapor stream 116 from the phase separator 146 to the heat exchanger 118. Also, a first portion of a liquid stream conduit may be positioned between the phase separator 146 and the heat exchanger 118 to supply a first portion 114 of the liquid stream 113 to the heat exchanger 118 for mixing with the vapor stream 116 and supplying it through the heat exchanger 118. A scrub column reflux accumulator supply conduit positioned between the reflux accumulator vessel 120 and the heat exchanger 118 may also be present such that the scrub column reflux stream 148 is supplied from the heat exchanger 118 to the reflux accumulator vessel 120. Additionally, a stabilizer column reflux conduit positioned between the stabilizer column 110 and the phase separator 146 may be present such that a second portion 115 of the liquid stream 113 may be supplied to the stabilizer column 110.

[0066] In yet another example, there may be a scrub tower reflux feed conduit positioned between the reflux accumulator vessel 120 and the scrub tower 106 to provide the scrub tower reflux feed stream 124 from the reflux accumulator vessel 120 to the scrub tower 106. There may also be a stabilizer column reflux conduit positioned between the phase separator 146 and the stabilizer column 110 to provide the second portion 115 of the liquid stream 113 from the phase separator 146 to the stabilizer column 110. As discussed above, one or more pumps may be positioned in communication with one or more of the conduits to help drive the flow of fluids to the different elements (e.g., the stabilizer column reflux driven pump 144 and the scrub column reflux fluid driven pump 122, etc.).

[0067] 2 illustrates an exemplary process for treating a feed gas containing methane. An embodiment of the process can facilitate the removal of heavy hydrocarbons from the feed gas. The apparatus embodiments described herein can utilize this embodiment of the process.

[0068] In the first step S1, the feed 100 can be fed to the scrub tower 106 and a vapor stream can be output from the scrub tower 106 as the first scrub tower stream 104. In some embodiments, the first scrub tower stream 104 can be fed to a heat exchanger 118 to cool at least a portion of the feed 100 to a preselected scrub temperature. The lower second scrub tower stream 108 can also be output from the scrub tower 106 as a liquid or predominantly liquid stream. The lower second scrub tower stream 108 output from the scrub tower 106 can be fed to a stabilizer tower 110. The lower second scrub tower stream 108 can include heavy hydrocarbons having 5 or more carbon atoms (e.g., in some embodiments, the second scrub tower stream 108 can include 30 mol% to 50 mol% heavy hydrocarbons, or 20 mol% to 40 mol% heavy hydrocarbons).

[0069] The scrub column 106 can be operated at a preselected scrub column operating pressure that is higher than a preselected stabilizer column operating pressure. For example, in some embodiments, the scrub column 106 can be operated at a pressure range of 45 bara to 65 bara, and the stabilizer column 110 that receives the second scrub column stream 108 can be operated at a preselected stabilized column pressure in the range of 15 bara to 30 bara.

[0070] In a second step S2, the stabilizer tower 110 may produce a first stabilizer tower stream 111, a portion of which may be fed to and cooled in a heat exchanger 118 and then fed to the scrub tower as reflux stream 124 (e.g., the cooled portion of the first stabilizer tower stream 11 may be split via a phase separator 146, such that a portion of this stream is cooled and fed to an accumulator vessel 120 and then fed to the scrub tower 106 as the scrub tower reflux feed stream 124). A second stream containing heavy hydrocarbons of 5 or more carbon atoms may also be output by the apparatus 1 as a second stabilizer tower stream 112 to facilitate removal of heavy hydrocarbons from the treated feed 126 that is fed to an LNG plant or NGL recovery plant for liquefaction.

[0071] In some embodiments, in the second step S2, a portion of the first stabilizer tower stream 111 can be cooled to a phase separator feed temperature and fed to a phase separator 146 to form a vapor stream 116 and a liquid stream 113. The liquid stream 113 can be split into a first portion 114 that is fed to a heat exchanger 118 for use as reflux for the scrub column 106 and a second portion 115 that is fed to the stabilizer column 110 as a reflux stream for the stabilizer column 110.

[0072] The process embodiment may also include additional steps. For example, the process may include a third step S3 in which a portion of the first stream output from the stabilizer column 110 is cooled to form a scrub column reflux and fed to the scrub column 106 (e.g., the vapor stream 116 and / or the first portion 114 of the liquid stream 113 output from the phase separator 146 may be cooled via a heat exchanger 118 to form a scrub column reflux). The formed scrub column reflux may also be fed to the scrub column 106 via a scrub column reflux feed pump 122 and / or a reflux accumulator vessel 120, as discussed above.

[0073] As another example, at least a portion of the feed 100 may be cooled to a preselected scrubbing temperature via the heat exchanger 118 and fed to the scrub tower 106 to remove heavy hydrocarbons having 5 or more carbons (e.g., pentane, hexane, etc.). As can be understood from the above, this step of the process may include splitting the feed 100 into different portions and cooling the entire feed or a majority of the feed, while the third portion 132 (or the second portion if the second portion 130 is not formed) may not be cooled and may be fed to the lower section of the scrub tower 106 as the lower section feed portion 132A. In some embodiments, the stripping steam fed to the lower section of the scrub tower and then mixed with the second portion 130 and / or the first portion 128 and fed to the scrub tower 106 may be formed by utilizing the third portion 132 as a heating medium, such that all portions of the feed 100 that may be split from the feed 100 are cooled before being fed to the scrub tower 106. It should also be understood that in embodiments in which second portion 130 is not formed, third portion 132 separated from feed 100 can be considered the second portion of the feed instead of the third portion of the feed.

[0074] Embodiments of the methods and apparatus described herein can be configured to provide a treated feedstream 126 that is completely free of heavy hydrocarbons or nearly completely free of such heavy hydrocarbons (e.g., containing only trace amounts of heavy hydrocarbons having 5 or more carbon atoms). The treated feedstream 126 can be provided at a preselected treated feedstream pressure that is within a preselected treated feedstream pressure range. The preselected treated feedstream pressure range can be 50 bara to 60 bara, 40 bara to 65 bara, or another suitable pressure range that can be selected to provide a high pressure to the treated feedstream 126 so that the treated feedstream 126 can be fed to a downstream LNG plant or liquefaction plant process (e.g., a liquefier). Such high pressure can provide improved downstream operational flexibility and also allow downstream operations to be performed more efficiently and at lower cost (e.g., by reducing the compression loads and compressor arrangements required for such processing, etc.).

[0075] It is understood that modifications to the embodiments explicitly shown and discussed herein may be made to meet a particular set of design goals or a particular set of design criteria. For example, the arrangement of valves, piping, and other conduit elements (e.g., conduit connections, tubing, seals, valves, etc.) for interconnecting different units of equipment and providing fluid flow between different elements (e.g., pumps, heat exchangers, cooling devices, chillers, compressors, etc.) may be arranged to meet a particular plant layout design that takes into account the available area of ​​the plant, the sized equipment of the plant, and other design considerations. As another example, the flow rates, pressures, and temperatures of fluids passing through various equipment or system elements may be varied to account for different design configurations and other design criteria.

[0076] Embodiments of the apparatus for treating a gas feed comprising methane to remove impurities therefrom, the process for treating a gas feed comprising methane to remove impurities therefrom, and / or the system for treating a gas feed comprising methane to remove impurities therefrom can each be configured to include process control elements arranged and positioned to monitor and control operation (e.g., an automated process control system having at least one workstation including temperature and pressure sensors, flow sensors, a processor, non-transitory memory, and at least one transceiver for communicating with the sensor elements, valves, and a controller for providing a user interface for the automated process control system, which may be executed on the workstation and / or another computing device of the plant, etc.). It should be appreciated that embodiments may also utilize a distributed control system (DCS) for implementing one or more processes and / or controlling the operation of the equipment as well.

[0077] As another example, it is contemplated that certain features described individually or as part of an embodiment may be combined with other individually described features or parts of other embodiments. Thus, elements and acts of various embodiments described herein can be combined to provide further embodiments. Thus, while certain illustrative embodiments of processes, apparatus, systems, and methods of making and using the same have been shown and described above, it should be clearly understood that the invention is not limited thereto and may be embodied in various other ways and implementations within the scope of the following claims.

Claims

1. 1. An apparatus for removing heavy hydrocarbon impurities from a feed comprising methane gas and hydrocarbons having at least 5 carbon atoms, comprising: The apparatus comprises: a scrub tower positioned and configured to receive the feed and to output a first scrub tower stream and a second scrub tower stream, the second scrub tower stream comprising the hydrocarbons having at least 5 carbon atoms; a stabilizer tower positioned downstream of the scrub tower to receive the second scrub tower stream and configured to output a first stabilizer tower stream and a second stabilizer tower stream, the second tower stabilizer stream comprising the hydrocarbons having at least 5 carbon atoms; Equipped with the scrub tower is positioned such that a portion of the first stabilizer tower stream is provided to the scrub tower as a scrub tower reflux stream.

2. 2. The apparatus of claim 1 comprising a reflux accumulator vessel positioned to receive the scrub tower reflux stream, store the scrub tower reflux stream, and supply the scrub tower reflux stream to the scrub tower.

3. cooling at least a portion of the feed before the feed is fed to the scrub tower; receiving the first scrub tower stream from the scrub tower; Cooling the scrub tower reflux stream before it is delivered to the reflux accumulator vessel.

3. The apparatus of claim 2, further comprising a heat exchanger positioned so as to

4. cooling a first portion of the feed before the feed is fed to the scrub column; receiving the first scrub tower stream from the scrub tower; Cooling the scrub tower reflux stream before it is fed to the scrub tower.

13. The apparatus of claim 1 comprising a heat exchanger positioned so as to

5. 2. The apparatus of claim 1, wherein the scrub column is positioned such that the second portion of the feed or the third portion of the feed passes through a side reboiler of the scrub column to cool that portion of the feed and heat liquid from the scrub column to form stripping steam, and the side reboiler is positioned to output the stripping steam to the scrub column.

6. 6. The apparatus of claim 5, wherein the heat exchanger and the scrub column are positioned such that the second portion of the feed or the third portion of the feed cooled in the side reboiler is combined with the first portion of the feed and fed to the scrub column.

7. 6. The apparatus of claim 5, wherein the side reboiler is positioned and arranged such that the second portion of the feed or the third portion of the feed cooled in the side reboiler is supplied to the scrub column.

8. a reflux accumulator vessel positioned to receive the portion of the first stabilizer stream supplied to the scrub tower, to store the scrub tower reflux stream, and to supply the scrub tower reflux stream to the scrub tower; a pump positioned to drive flow of the scrub tower reflux stream from the reflux accumulator vessel to the scrub tower; Further comprising:

2. The apparatus of claim 1, wherein the stabilizer tower is configured to operate at a preselected stabilizer tower operating pressure range and the scrub tower is configured to operate at a preselected scrub tower operating pressure range that is greater than the preselected stabilizer tower operating pressure range.

9. 10. The apparatus of claim 1, further comprising a phase separator positioned to receive the first stabilizer column stream and to output a vapor stream and a liquid stream.

10. a heat exchanger positioned to receive the vapor stream from the phase separator and a first portion of the liquid stream from the phase separator; the portion of the first stabilizer tower stream supplied to the scrub tower as the scrub tower reflux stream comprises the vapor stream from the phase separator and the first portion of the liquid stream from the phase separator; 10. The apparatus of claim 9, wherein the heat exchanger is configured and positioned to cool a first portion of the feed before the feed is supplied to the scrub column and to cool the scrub column reflux stream before the scrub column reflux stream is supplied to the scrub column.

11. a reflux accumulator vessel positioned to receive the scrub tower reflux stream from the heat exchanger, to store the scrub tower reflux stream, and to supply the scrub tower reflux stream to the scrub tower; a pump positioned to drive the flow of the scrub tower reflux stream from the reflux accumulator vessel to the scrub tower; Further comprising:

11. The apparatus of claim 10, wherein the stabilizer tower is configured to operate at a preselected stabilizer tower operating pressure range and the scrub tower is configured to operate at a preselected scrub tower operating pressure range that is greater than the preselected stabilizer tower operating pressure range.

12. 1. A process for treating a feed gas comprising methane and hydrocarbons having at least 5 carbon atoms, the process comprising: providing the feed gas to a scrub tower operating at a preselected scrub tower operating pressure range to output a first scrub tower stream and a second scrub tower stream from the scrub tower, the second scrub tower stream comprising the hydrocarbons having at least 5 carbon atoms; feeding the second scrub tower stream to a stabilizer tower operating at a preselected stabilizer tower operating pressure range to output a first stabilizer tower stream and a second stabilizer tower stream, the second stabilizer tower stream comprising the hydrocarbons having at least 5 carbon atoms; providing a portion of the first stabilizer tower stream to the scrub tower and providing a scrub tower reflux stream to the scrub tower; The process includes:

13. feeding the first stabilizer tower stream to a phase separator to form a vapor stream and a liquid stream; supplying said vapor stream and a portion of said liquid stream to a heat exchanger to form said scrub column reflux stream; providing the scrub column reflux stream from the heat exchanger to a reflux accumulator vessel; supplying the scrub tower reflux stream from the reflux accumulator vessel to an upper section of the scrub tower; The process of claim 12, comprising:

14. 14. The process of claim 13, comprising supplying the first scrub tower stream as a cooling medium to the heat exchanger to cool the portion of the vapor stream and the liquid stream supplied to the heat exchanger and form the scrub tower reflux stream.

15. 13. The process of claim 12, wherein the preselected scrub column operating pressure range is from 45 bara to 65 bara and the preselected stabilizer column operating pressure range is from 15 bara to 30 bara.

16. 13. The process of claim 12, comprising: splitting the feed into a first portion and a second portion; feeding the first portion to a heat exchanger positioned upstream of the scrub column; and mixing the first portion exiting the heat exchanger with the second portion prior to providing the feed to the scrub column.

17. dividing the feed into a first portion, a second portion, and a third portion; feeding the first portion to a heat exchanger positioned upstream of the scrub tower; and mixing the first portion exiting the heat exchanger with the second portion prior to providing a stream comprising the first portion and the second portion to the scrub tower; feeding the third portion to a section of the scrub column that is lower than a section to which the stream including the first portion and the second portion is fed; The process of claim 12, comprising:

18. splitting the feed into a first portion and a second portion, supplying the first portion to a heat exchanger positioned upstream of the scrub tower, and supplying the first portion exiting the heat exchanger to the scrub tower; feeding the second portion to a section of the scrub column that is lower than the section to which the first portion is fed; The process of claim 12, comprising:

19. dividing the feed into a first portion, a second portion, and a third portion; feeding the first portion to a heat exchanger positioned upstream of the scrub tower; and mixing the first portion exiting the heat exchanger with the second portion prior to providing a stream comprising the first portion and the second portion to the scrub tower; supplying the third portion to a side reboiler to form stripping steam, and supplying the stripping steam to the scrub column; The process of claim 12, comprising:

20. 20. The process of claim 19, comprising mixing the third portion with the second portion and / or the first portion prior to feeding the first portion, the second portion, and the third portion of the feed to the scrub column.

21. 13. The process of claim 12, wherein the preselected stabilizer column operating pressure range is lower than the preselected scrub column operating pressure range.

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