Methods for separating hydrocarbons

Abstract

A method for separating a mixed feed stream may include compressing and cooling a mixed feed stream to form a cooled mixed feed stream. The mixed feed stream includes H2S, CO2, and one or more of C2, C3, and C4 hydrocarbons. The method includes separating the cooled mixed feed stream to form a light first separator effluent and a heavy first separator effluent; and separating the light first separator effluent to form a light second separator effluent comprising CO2 and a heavy second separator effluent. The method includes reducing a pressure of the light second separator effluent to form a coolant stream and passing the coolant stream through one or more heat exchangers. The method includes separating the heavy second separator effluent to form at least a light third separator effluent and a heavy third separator effluent including less than or equal to 1000 ppm C2 hydrocarbons.

Description

METHODS FOR SEPARATING HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 609,123 filed December 12, 2023, the contents of which are incorporated in their entirety herein.TECHNICAL FIELD

[0002] Embodiments described herein generally relate to methods and systems for separating hydrocarbons.BACKGROUND

[0003] Various hydrocarbons, such as ethylene, ethane, propylene, propane, and heavier hydrocarbons, may be recovered from a variety of product streams obtained from chemical reactors. Cryogenic separation processes may be used to recover more condensable hydrocarbons from less condensable gasses or products.SUMMARY

[0004] In cryogenic separation processes, a mixed feed stream may be compressed and cooled by heat exchange with other process streams and / or external sources of refrigeration. As the mixed feed stream is cooled, streams comprising various fractions of the mixed feed stream may be collected as high pressure liquid or vapor streams. The mixed feed stream may include one or more acid gasses, such as CO2 and H2S. Some conventional separation systems may include a caustic tower, or comparable piece of process equipment, to at least partially remove CO2 and H2S from the mixed feed stream or fractions of the mixed feed stream formed in the separation process. Removing CO2 and H2S from the separation process may prevent the precipitation of CO2 in the separation process and may reduce the concentration of H2S in one or more of the product streams. However, the caustic tower may be a relatively expensive piece of equipment. Accordingly, there is a need for improved methods for separating mixed feed streams, in which the precipitation of CO2 is prevented and the concentration of H2S in one or more of the product streams is controlled, without the inclusion of a caustic tower in the separation system.

[0005] Embodiments of the methods for separating a mixed feed stream may address one or more of these problems. For example, the temperature and pressure of the less condensable gasses, comprising CO2 may be controlled such that CO2 does not precipitate in the separation system. Additionally, due to the boiling points of H2S and ethane, a fractionation system may be operated at conditions such that the concentration of H2S in a desired heavy product stream is below a predetermined threshold. The separation methods applying these concepts are explained in more detail in the following detailed description.

[0006] According to one or more embodiments of the present disclosure, a method for separating a mixed feed stream may comprise compressing the mixed feed stream to form a compressed mixed feed stream. The mixed feed stream comprises H2S, CO2, and one or more of C2, C3, and C4+ hydrocarbons. The method further comprises cooling the compressed mixed feed stream to form a cooled mixed feed stream; separating the cooled mixed feed stream in a first separation unit to form a light first separator effluent stream and a heavy first separator effluent stream; and cooling the light first separator effluent stream to form a cooled, light first separator effluent stream. The method further comprises, separating the cooled, light first separator effluent stream in a second separation unit to form a light second separator effluent stream and a heavy second separator effluent stream. The light second separator effluent stream comprises CO2. The method further comprises reducing a pressure of the light second separator effluent stream to form a coolant stream and passing the coolant stream through one or more heat exchangers to provide cooling to the one or more heat exchangers. The method further comprises separating the heavy second separator effluent stream in a third separation unit to form at least a light third separator effluent stream and a heavy third separator effluent stream, such that the heavy third separator effluent stream comprises less than or equal to 1000 ppm C2 hydrocarbons.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings, where like structure is indicated with like reference numerals and in which:

[0008] FIG. 1 schematically depicts a system for separating hydrocarbons, according to one or more embodiments disclosed herein; and

[0009] It should be understood that the drawings are schematic in nature, and do not include some components of a separation system commonly employed in the art, such as, without limitation, temperature transmitters, pressure transmitters, flow meters, pumps, valves, and the like. It would be known that these components are within the spirit and scope of the present embodiments disclosed. However, operational components, such as those described in the present disclosure, may be added to the embodiments described in this disclosure.

[0010] Reference will now be made in greater detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings.DETAILED DESCRIPTION

[0011] One or more non-limiting embodiments of methods for separating a mixed feed stream are described herein. FIG. 1 depicts an embodiment of a system for separating a mixed feed stream. Embodiments of the methods for separating a mixed feed stream described herein may be performed using a system as depicted in FIG. 1. However, it should be understood that the methods for processing mixed feed streams described herein are not limited to the use of the system depicted in FIG. 1.

[0012] Referring now to FIG. 1, a method for separating a mixed feed stream 100 may comprise compressing the mixed feed stream 100 to form a compressed mixed feed stream 101. The mixed feed stream 100 may be compressed in one or more compressors. The compressors may be any suitable compressors, including but not limited to, centrifugal compressors. Referring to FIG. 1, the mixed feed stream 100 may be compressed in compressor 404 to form compressed mixed feed stream 101. It should be understood that the number of compressors is not necessarily limited. For example, the mixed feed stream may be compressed in 1, 2, 3, 4, or even 5 or more compressors arranged in series.

[0013] In one or more embodiments, the mixed feed stream 100 may comprise H2S, CO2, and one or more of C2, C3, or C4+ hydrocarbons. In some embodiments, the mixed feed stream may comprise at least 70 wt.% of the combination of H2S, CO2, and the one or more of C2, C3, and C4+ hydrocarbons. For example, the mixed feed stream 100 may comprise at least 70 wt.%, 75 wt.%, 80 wt.%, 85 wt.%, 90 wt.%, or 95 wt.% of the combination of H2S, CO2, and the one or more of C2, C3, and C4+ hydrocarbons. In one or more embodiments, the C2, C3, and C4+hydrocarbons may comprise olefins and paraffins, including but not limited to ethane, ethylene, propane, propylene, butane, and butene. In one or more embodiments, the mixed feed stream 100 may further comprise one or more of nitrogen, hydrogen, methane, and carbon monoxide.

[0014] In one or more embodiments, the method for separating the mixed feed stream 100 may comprise cooling the compressed mixed feed stream 101 to form a cooled mixed feed stream 102. The compressed mixed feed stream 101 may be cooled in any suitable heat exchanger. The compressed mixed feed stream 101 may occur in one or more heat exchangers. In some embodiments, the compressed mixed feed stream 101 may be cooled in a heat exchanger positioned within cold box 220. In one or more embodiments, as depicted in FIG. 1, cooling the compressed mixed feed stream 101 may occur in the second heat exchanger 202. In one or more embodiments, cooling the compressed mixed feed stream 101 may condense at least a portion of the compressed mixed feed stream 101.

[0015] As used in this disclosure, a “cold box” refers to an insulated enclosure that may house one or more system components. The cold box may be insulated to minimize heat transfer between the system components and the environment. In one or more embodiments, one or more heat exchangers may be positioned within a cold box. In some embodiments, multiple heat exchangers may be positioned in series within a cold box. The heat exchangers may include a brazed heat exchanger, a shell and tube heat exchanger, double pipe heat exchanger, plate heat exchanger, tubular heat exchanger, fin type heat exchanger, condensers, evaporators, boilers, or combinations thereof.

[0016] In one or more embodiments, the cooled mixed feed stream 102 may be separated into a light first separator effluent stream 104 and a heavy first separator effluent stream 106. The cooled mixed feed stream 102 may be separated into the light first separator effluent stream 104 and the heavy first separator effluent stream 106 in a first separation unit 300. First separation unit 300 may be any suitable separator. For example, without limitation, first separation unit 300 may be a flash-drum in one or more embodiments.

[0017] As used in this disclosure, a “separator” refers to any separation device or system of separation devices that at least partially separates one or more chemicals that are mixed in a process stream from one another. For example, a separator may selectively separate differing chemical species or phases from one another, forming one or more chemical fractions. Examplesof separators include, without limitation, distillation columns, flash drums, knock-out drums, knock-out pots, traps, scrubbers, expansion devices, membranes, solvent extraction devices, and the like. It should be understood that separation processes described in this disclosure may not completely separate all of one chemical constituent from all of another chemical constituent. It should be understood that the separation processes described in this disclosure “at least partially” separate different chemical components from one another, and that even if not explicitly stated, it should be understood that separation may include only partial separation. As used in this disclosure, one or more chemical constituents may be “separated” from a process stream to form a new process stream. Generally, a process stream may enter a separator and be divided, or separated, into two or more process streams of desired composition.

[0018] The light first separator effluent stream 104 may be cooled to form a cooled, light first separator effluent stream 108. In some embodiments, the cooled, light first separator effluent stream 108 may be partially condensed, and in some embodiments, the cooled, light first separator effluent stream 108 may be fully condensed. The cooled, light first separator effluent stream 108 may be cooled in one or more heat exchangers. In some embodiments, the cooled, light first separator effluent stream 108 may be cooled in a heat exchanger positioned within cold box 220. Still referring to FIG. 1, in one or more embodiments, the cooled, light first separator effluent stream 108 may be cooled in the first heat exchanger 200.

[0019] Still referring to FIG. 1, the cooled, light first separator effluent stream 108 may be separated into a light second separator effluent stream 110 and a heavy second separator effluent stream 112 in second separation unit 302. The second separation unit 302 may be any suitable separator. For example, the second separation unit 302 may be a vapor / liquid separator such as a flash drum. In one or more embodiments, the heavy second separator effluent stream 112 may comprise H2S and one or more of C2, C3, or C4+ hydrocarbons. In one or more embodiments, the light second separator effluent stream 110 may comprise CO2 and one or more of hydrogen, nitrogen, methane, and carbon monoxide. For example, the light second separator effluent stream 110 may comprise at least 50 wt.% 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 85 wt.%, of CO2 and one or more of hydrogen, nitrogen, methane, and carbon monoxide.

[0020] In one or more embodiments, methods for separating a mixed feed stream 100 may include passing the light second separator effluent stream 110 through one or more heatexchangers to provide cooling in the one or more heat exchangers. Passing the light second separator effluent stream 110 through the one or more heat exchangers may provide cooling to the one or more heat exchangers. Furthermore, passing the light second separator effluent stream 110 through on eor more heat exchangers may heat the light second separator effluent stream 110 and produce a warmed light second separator effluent stream 120. In some embodiments, one or more of the heat exchangers may be positioned in the cold box 220. In one or more embodiments, as depicted in FIG. 1, the light second separator effluent stream 110 may be passed from separator 302 to the first heat exchanger 200 to provide cooling to the first heat exchanger 200 and produce the warmed light second separator effluent stream 120.

[0021] In one or more embodiments, a pressure of the warmed light second separator effluent stream 120 may be reduced in an expander 402 to form a coolant stream 122. The expander 402 may be any suitable expander. Reducing the pressure of the warmed light second separator effluent stream 120 in the expander 402 may reduce the temperature of the warmed light second separator effluent stream 120, forming the coolant stream 122.

[0022] In one or more embodiments, a temperature of the coolant stream 122 exiting the expander 402 may be greater than a temperature at which CO2 freezes. Without intending to be bound by theory, the partial pressure of CO2 in the coolant stream 122 and the temperature of the coolant stream 122 may determine whether CO2 freezes in the coolant stream 122. Accordingly, the temperature of coolant stream 122 may be controlled to prevent freezing and precipitation of CO2 in the coolant stream 122. It should be noted that other factors, such as binary interactions, may also affect the conditions at which CO2 may precipitate. However, these other factors may have a relatively minor influence on the freezing and precipitation conditions of CO2 relative to the partial pressure of CO2 in coolant stream 122 and the temperature of coolant stream 122.

[0023] In one or more embodiments, the discharge of coolant stream 122 may be the coldest point for the less condensable gasses exiting the second separator 302 in light second separator effluent stream 110. If the temperature of coolant stream 122 is greater than the temperature at which CO2 freezes at the outlet of the expander 402, then it is unlikely that CO2 will freeze in the coolant stream 122 downstream of expander 402 or within the one or more heat exchangers positioned within cold box 220. Without intending to be bound by theory, CO2 freezing mayrestrict the flow of fluid through the one or more heat exchangers, creating pressure drop and reducing heat transfer.

[0024] In one or more embodiments, the temperature at which CO2 may freeze in the coolant stream 122 may be from -180 °C to -100 °C. For example, without limitation, the temperature at which CO2 may freeze in the coolant stream 122 may be from -180 °C to -100 °C, from -170 °C to -100 °C, from -160 °C to -100 °C, from -150 °C to -100 °C, from -140 °C to -100 °C, from - 130 °C to -100 °C, from -120 °C to -100 °C, from -110 °C to -100 °C, from -180 °C to -110 °C, from -180 °C to -120 °C, from -180 °C to -130 °C, from -lf80 °C to -140 °C, from -180 °C to - 150 °C, from -180 °C to -160 °C, from -180 °C to -170 °C, or any range or combination of ranges formed from these endpoints. In one or more embodiments, the coolant stream 122 may have a temperature greater than -180 °C, greater than -170 °C, greater than -160 °C, greater than -150 °C, greater than -140 °C, greater than -130 °C, greater than -120 °C, greater than -110 °C, or even greater than -100 °C. It should be understood that the temperature at which CO2 may freeze may be outside of these ranges in some embodiments described herein. It should be noted that the temperatures at which CO2 freezes described hereinabove are not limiting on every embodiment disclosed herein.

[0025] Still referring to FIG. 1, in one or more embodiments, the coolant stream 122 may be passed through one or more heat exchangers to provide cooling in the one or more heat exchangers. In some embodiments, one or more of the heat exchangers may be positioned within cold box 220. In some embodiments, passing the coolant stream 122 through one or more heat exchangers may produce an off-gas stream 125, which may exit the system. In one or more embodiments, coolant stream 122 may be passed through the first heat exchanger 200 to provide cooling to the first heat exchanger 200 and produce stream 123. Stream 123 may have a temperature that is greater than a temperature of coolant stream 122. Stream 123 may be passed through the second heat exchanger 202 to provide cooling to the second heat exchanger 202 and form off-gas stream 125. In one or more embodiments, off-gas stream 125 may have a temperature greater than or equal to the temperature of stream 123.

[0026] In one or more embodiments, the heavy second separator effluent stream 112 may be passed to a third separation unit 304. The heavy second separator effluent stream 112 may be passed through one or more heat exchangers before being passed to the third separation unit 304.Passing the heavy second separator effluent stream 112 through one or more heat exchangers may warm the heavy second separator effluent stream 112 and may provide cooling to the one or more heat exchangers. In some embodiments, the heavy second separator effluent stream 112 may be passed through the first heat exchanger 200 to provide cooling to the first heat exchanger 200. In some embodiments, the heavy second separator effluent stream 112 may be passed through the second heat exchanger 202 to provide cooling to the second heat exchanger 202. In some embodiments, as depicted in FIG. 1, the second portion of the second liquid stream 112 may be passed through the first heat exchanger 200 and then passed through the second heat exchanger 202 to provide cooling to both the first heat exchanger 200 and the second heat exchanger 202 before being passed to the third separation unit 304.

[0027] In one or more embodiments, the third separation unit 304 may be a fractionation system. As used in this disclosure, a “fractionation system” refers to any fractionation device or system of fractionation devices that at least partially divide a certain quantity of a mixture (gas, solid, liquid, or combinations thereof), during a phase transition, into a number of smaller fractions in which the composition varies according to a gradient. In one or more embodiments, the third separation unit 304 may be a multi-stage fractionation system. In such embodiments, the third separation unit 304 may comprise multiple fractionation devices in series. For example, the third separation unit 304 may comprise multiple separators and may include reflux or recycle streams or cooling steps between the separators.

[0028] In one or more embodiments, the heavy second separator effluent stream 112 may be separated into at least a light third separator effluent stream 126 and a heavy third separator effluent stream 131. In one or more embodiments, the light third separator effluent stream 126 may comprise C2 hydrocarbons and H2S. For example, the light third separator effluent stream 126 may comprise at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, or even at least 90 wt.% C2 hydrocarbons and H2S. In one or more embodiments, the heavy third separator effluent stream 131 may comprise C3+ hydrocarbons. For example, the heavy third separator effluent stream 131 may comprise at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, or even at least 90 wt.% C3+ hydrocarbons.

[0029] In some embodiments, the heavy second separator effluent stream 112 may be separated into a light third separator effluent stream 126, an intermediate third separator effluentstream 128, and a heavy third separator effluent stream 131. In such embodiments, the intermediate third separator effluent stream 128 may comprise C2 hydrocarbons. For example, the intermediate third separator effluent stream 128 may comprise at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, or even at least 90 wt.% C2 hydrocarbons.

[0030] In one or more embodiments, the heavy third separator effluent stream 131 may comprise less than or equal to 1000 ppm C2 hydrocarbons. For example, the heavy third separator effluent stream may comprise less than or equal to 1000 ppm, less than or equal to 900 ppm, less than or equal to 800 ppm, less than or equal to 700 ppm, less than or equal to 600 ppm, less than or equal to 500 ppm, less than or equal to 400 ppm, less than or equal to 300 ppm, less than or equal to 200 ppm or even less than or equal to 100 ppm C2 hydrocarbons. Unless otherwise specified, “ppm,” as used in the present application, is based on weight.

[0031] In one or more embodiments, the heavy third separator effluent may comprise less than or equal to 1000 ppb H2S. For example, the heavy third separator effluent may comprise less than or equal to 1000 ppb, less than or equal to 900 ppb, less than or equal to 800 ppb, less than or equal to 700 ppb, less than or equal to 600 ppb, less than or equal to 500 ppb, less than or equal to 400 ppb, less than or equal to 300 ppb, or even less than or equal to 200 ppb H2S. Unless otherwise specified, “ppb,” as used in the present application, is based on weight.

[0032] Without intending to be bound by theory, when C2 and C3 hydrocarbons are separated in a fractionation system, such as the third separation unit 304, at least some C2 hydrocarbons may remain with the C3 hydrocarbons in a heavy fraction, such as heavy third separator effluent stream 131. The concentration of C2 hydrocarbons included in a heavy fraction with C3 hydrocarbons may be controlled by adjusting the operating conditions of the fractionation system. In one or more embodiments, adjusting the amount of energy used in a reboiler of the fractionation system may affect the concentration of C2 hydrocarbons in the heavy fraction. For example, if more energy is used in the reboiler, increasing heat in the reboiler, then the concentration of C2 hydrocarbons in the heavy fraction may be reduced. If less energy is used in the reboiler, then the concentration of C2 hydrocarbons in the heavy fraction may be increased. Accordingly, the concentration of C2 hydrocarbons in the heavy fraction may be adjusted to meet a pre-selected target.

[0033] Without intending to be bound by theory, H2S may have a similar boiling point to C2 hydrocarbons. Accordingly, a majority of the H2S fed to the fractionation system may exit the fractionation system in the same fraction as a majority of the C2 hydrocarbons. For example, a majority of the H2S fed to the third separation unit 304 may exit the third separation unit 304 in the light third separator effluent stream 126. However, some H2S may still be present in the heavy fraction with the C3 hydrocarbons. For example, at least a portion of the H2S fed to the third separation unit 304 may exit the third separation unit 304 in the heavy third separator effluent stream 131. Like C2 hydrocarbons, the concentration of H2S in the heavy third separator effluent stream may be controlled by adjusting the operating conditions of the fractionation system. In one or more embodiments, adjusting the amount of energy used in a reboiler of the fractionation system may affect the concentration of H2S in the heavy fraction. For example, if more energy is used in the reboiler, increasing heat in the reboiler, then the concentration of H2S in the heavy fraction may be reduced. If less energy is used in the reboiler, then the concentration of H2S in the heavy fraction may be increased. Accordingly, the concentration of H2S in the heavy fraction may be adjusted to meet a pre-selected target.

[0034] Without intending to be bound by theory, the ability to control the concentration of H2S in the heavy fraction may eliminate the need for a caustic tower in the separation system. In one or more embodiments, the methods for separating mixed feed streams may be free from passing the mixed feed stream or any fraction of the mixed feed stream through a caustic tower. A caustic tower is a unit used to remove acid gasses, such as H2S and CO2, from hydrocarbons. Generally, a caustic tower may accomplish this separation by contacting the hydrocarbon stream comprising the acid gasses with a caustic solution, such that the acid gasses is at least partially removed by an acid-base reaction. Eliminating the need for a caustic tower may reduce the capital cost of the separation system. Further any additional operating expenses from controlling the amount of H2S in the heavy fraction by increasing the amount of energy used in the reboiler of the fractionation system may be offset by the initial capital savings from omitting a caustic tower from the separation system.

[0035] In one or more embodiments, as depicted in FIG. 1, the methods described herein may comprise combining the heavy first separator effluent stream 106 with the heavy second separator effluent stream 112 prior to separating the heavy second separator effluent stream 112 to form at least the light third separator effluent stream 126, the intermediate third separatoreffluent stream 128, and the heavy third separator effluent stream 131. In embodiments, where the heavy first separator effluent stream 106 is combined with the heavy second separator effluent stream 112, the combined stream may be separated into the light third separator effluent stream 126, the intermediate third separator effluent stream 128, and the heavy third separator effluent stream 131.

[0036] In one or more embodiments, the light third separator effluent stream 126 may be passed to the second heat exchanger 202 to provide cooling to the second heat exchanger 202. After providing cooling to the second heat exchanger 202, the light third separator effluent stream 126 may exit the system. In some embodiments, as depicted in FIG. 1, the pressure of light third separator effluent stream 126 may be reduced to cool the light third separator effluent stream 126 and form a cooled light third separator effluent stream 127. The pressure of the light third separator effluent stream 126 may be reduced by passing the light third separator effluent stream 126 through valve 504. In such embodiments, the cooled light third separator effluent stream 127 may be passed to the second heat exchanger 202 to provide cooling to the second heat exchanger 202. The cooled light third separator effluent stream 127 may be warmed in the second heat exchanger 202 and may exit the system through stream 129.

[0037] In one or more embodiments, the methods described herein may comprise cracking at least a portion of the light third separator effluent stream 126. In some embodiments, at least a portion of the light third separator effluent stream 126 may be cracked after it is passed through the second heat exchanger 202, as previously described. The at least a portion of the light third separator effluent stream 126 may be cracked in any suitable reactor. Without intending to be bound by theory, the inclusion of H2S in the light third separator effluent stream 126 may reduce coke formation in the cracking process.

[0038] Still referring to FIG. 1, a pressure of the intermediate third separator effluent stream 128 may be reduced to at least partially vaporize the intermediate third separator effluent stream 128 to form a second coolant stream 130. In one or more embodiments, the pressure of the intermediate third separator effluent stream 128 may be reduced by passing the intermediate third separator effluent stream 128 through valve 500.

[0039] In one or more embodiments, as depicted in FIG. 1, the second coolant stream 130 may be passed through the first heat exchanger 200 to provide cooling in the first heat exchanger200 and to form stream 134. Stream 134 may be passed through the second heat exchanger 202 to provide cooling to the second heat exchanger 202 and produce warmed stream 136. In one or more embodiments, at least a portion of the second coolant stream 130 may be vaporized in the one or more heat exchangers. For example, at least 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.%, or even 99 wt.% of the warmed recycle stream 136 may be vapor. In some embodiments, the warmed recycle stream may be fully vaporized.

[0040] In one or more embodiments, at least a portion of the warmed stream 136 may be recycled to the compressor 404. In such embodiments, the mixed feed stream 100 and the at least a portion of the warmed stream 136 may be compressed to form compressed mixed feed stream 101.

[0041] In one or more embodiments, a stream comprising alkanes 140 may be passed through the one or more heat exchangers to provide cooling in the one or more heat exchangers. The stream comprising alkanes may comprise greater than 25 wt.%, 50 wt.%, 75 wt.% or even 95 wt.% alkanes. In one or more embodiments, the stream comprising alkanes may comprise one or more of C2, C3, and C4 alkanes. Passing the stream comprising alkanes 140 through the one or more heat exchangers may warm the stream comprising alkanes 140 to form a warmed alkane stream 142. In one or more embodiments, the one or more heat exchangers may be positioned within a cold box 220. In one or more embodiments, at least a portion of the warmed alkane stream 142 may be passed to a reactor. For example, at least a portion of the warmed alkane stream 142 may be passed to a dehydrogenation reactor to be used a feedstock for the dehydrogenation reaction.EXAMPLES

[0042] Various embodiments of the processes and systems for separating a mixed feed stream will be further clarified in the following Examples. The Examples are illustrative in nature, and should not be understood to limit the subject matter of the present disclosure.

[0043] Example 1 - Hydrogen Sulfide Separation

[0044] In Example 1, the separation system depicted in FIG. 1 was modeled using an integrated process model in Aspen plus. The numbering of the streams included in Tables 1 and 2 is consistent with the numbering of the streams in FIG. 1 and the numbering used throughoutthe detailed description. Table 1 shows temperatures, pressures, and mass fractions of streams depicted in FIG. 1 according to a first simulation of the separation system. Table 2 shows temperatures, pressures, and mass fractions of the streams depicted in FIG. 1 according to a second simulation of the separation system. The first and second simulations of the separation system differ in the conditions at which fractionation system 304 operated, resulting in differences in the compositions of streams 126, 128, and 131, as shown in Tables 1 and 2 below. Specifically, the fractionation system 304 was operated at tighter specifications for ethane and H2S, such that the content of ethane and H2S in stream 131 in Table 2 is less than the content of H2S in stream 131 of Table 1.Table 1.Stream Number 110 112 120 122 123T (°C) -103 -103 -57 -116 -22P (psig) 401 401 398 95 93Mass Fraction (wt.%)N2 + H2 87% 1% 87% 87% 87%CO2 0.6% 2% 0.6% 0.6% 0.6%H2S 300 ppb 10 ppm 300 ppb 300 ppb 300 ppbEthane 2% 19% 2% 2% 2% c31% 73% 1% 1% 1%Table 1 Cont.Stream Number 125 119 126 128 131T (°C) 21 20 -9 -9 70P (psig) 91 384 380 380 390Mass Fraction (wt.%)N2 + H2 87% 1% 7% 1% 0%CO2 0.6% 1% 6% 3% 0%H2S 300 ppb 6.6 ppm 45 ppm 55 ppm 68 ppbEthane 2% 11% 70% 81% 19 ppmC3 1% 85% 2% 7% 99.5%

[0045] As shown in Table 1, the system was able to produce a heavy third separator effluent stream 131 having a concentration of H2S of 68 ppb and a concentration of Ethane of 19 ppm, without the use of a caustic tower to remove acid gasses from the system. Furthermore, the heavy third separator effluent stream 131 comprised 0 wt.% CO2.Table 2.Stream Number 110 112 120 122 123T (°C) -103 -103 -57 -116 -22P (psig) 401 401 398 95 93Mass Fraction (wt.%)N2 + H2 87% 1% 87% 87% 87%CO2 0.6% 2% 0.6% 0.6% 0.6%H2S 300 ppb 10 ppm 300 ppb 300 ppb 300 ppbEthane 2% 19% 2% 2% 2% c31% 73% 1% 1% 1%Table 2 Cont.Stream Number 125 119 126 128 131T (Deg C) 21 20 -9 -9 70P (PSIG) 91 384 380 380 390Mass Fraction (wt.%)N2 + H2 87% 1% 7% 1% 0%CO2 0.6% 1% 6% 3% 0%H2S 300 ppb 6.6 ppm 46 ppm 56 ppm 13 ppbEthane 2% 11% 70% 81% 2 ppmC3 1% 85% 2% 7% 99.5%

[0046] As shown in Table 2, the system was able to produce a heavy third separator effluent stream 131 having a concentration of H2S of only 13 ppb and a concentration of Ethane of 2 ppm, without the use of a caustic tower to remove acid gasses from the system. Furthermore, the heavy third separator effluent stream 131 comprised 0 wt.% CO2. Accordingly, the separation methods and systems modeled in the present examples show that a product comprising C3 hydrocarbons with reduced concentrations of H2S and CO2 may be achieved without the use of a caustic tower to remove acid gasses.

[0047] Example 2 - Carbon Dioxide Precipitation

[0048] Example 2 examines whether the carbon dioxide present in coolant stream 122 precipitates. As shown in Tables 1 and 2 of Example 1, coolant stream 122 is the coldest stream in the system in both the first simulation and the second simulation of the separation system. Accordingly, if CO2 were to precipitate within the system, the CO2 would precipitate in coolant stream 122. Table 3 provides the temperature and mole fraction of CO2 at which the CO2 in coolant stream 122 would precipitate. According to Table 3, if the temperature of the coolant stream 122 is at -116 °C then the mole fraction of CO2 should be less than 1.1 mol.% to avoid precipitation. In each of Tables 1 and 2, the mole fraction of CO2 in the coolant stream 122 was 0.1 mol.% (0.6 wt.%). Accordingly, the mole fraction of CO2 in the coolant stream 122 was well below the limit at which CO2 would precipitate even without the removal of CO2 from the separation system using a caustic tower.Table 3Temperature (°C) CO2 Mole Fraction (mol.%)-100 4.2%-120 1.1%-140 0.3%

[0049] It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the present technology, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce arecitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”

[0050] It should be understood that where a first component is described as “comprising” a second component, it is contemplated that, in some embodiments, the first component “consists of’ or “consists essentially of’ that second component. Additionally, the term “consisting essentially of’ is used in this disclosure to refer to quantitative values that do not materially affect the basic and novel characteristic(s) of the disclosure. For example, a chemical composition “consisting essentially of’ a particular chemical constituent or group of chemical constituents should be understood to mean that the composition includes at least about 99.5% of a that particular chemical constituent or group of chemical constituents.

[0051] It should be understood that any two quantitative values assigned to a property may constitute a range of that property, and all combinations of ranges formed from all stated quantitative values of a given property are contemplated in this disclosure.

[0052] The subject matter of the present disclosure has been described in detail and by reference to specific embodiments. It should be understood that any detailed description of a component or feature of an embodiment does not necessarily imply that the component or feature is essential to the particular embodiment or to any other embodiment. Further, it should be apparent to those skilled in the art that various modifications and variations can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

Claims

AMENDED CLAIMS received by the International Bureau on 23 May 2025 ( 23.05.2025)1. A method for separating a mixed feed stream, the method comprising: compressing the mixed feed stream to form a compressed mixed feed stream, wherein the mixed feed stream comprises H2S, CO2, and one or more of C2, C3, and C4+ hydrocarbons; cooling the compressed mixed feed stream to form a cooled mixed feed stream; separating the cooled mixed feed stream in a first separation unit to form a light first separator effluent stream and a heavy first separator effluent stream; cooling the light first separator effluent stream to form a cooled, light first separator effluent stream; separating the cooled, light first separator effluent stream in a second separation unit to form a light second separator effluent stream and a heavy second separator effluent stream, wherein the light second separator effluent stream comprises CO2; reducing a pressure of the light second separator effluent stream to form a coolant stream; passing the coolant stream through one or more heat exchangers to provide cooling to the one or more heat exchangers; and separating the heavy second separator effluent stream in a third separation unit to form at least a light third separator effluent stream and a heavy third separator effluent stream, such that the heavy third separator effluent stream comprises less than or equal to 1000 ppm C2 hydrocarbons and at least 50 wt.% C3+ hydrocarbons.

2. The method of claim 1 , wherein a temperature of the coolant stream is greater than a temperature at which the CO2 in the coolant stream freezes.

3. The method of claim 1 or claim 2, the method further comprising combining the heavy first separator effluent stream with the heavy second separator effluent stream prior to separating the heavy second separator effluent stream to form at least the light third separator effluent stream and the heavy third separator effluent stream.

4. The method of any one of claims 1 to 3, wherein the light third separator effluent stream comprises at least 50 wt.% C2 hydrocarbons and H2S.

5. The method of any one of claims 1 to 4, wherein the heavy third separator effluent stream comprises less than or equal to 1000 ppb H2S.

6. The method of any one of claims 1 to 5, the method further comprising cracking at least a portion of the light third separator effluent stream.

7. The method of any one of claims 1 to 6, wherein the mixed feed stream comprises at least 70 wt.% of the combination of H2S, CO2, and one or more of C2, C3, and C4+ hydrocarbons.

8. The method of any one of claims 1 to 7, wherein heating the light second separator effluent stream comprises passing the light second separator effluent stream through one or more heat exchangers to provide cooling to the one or more heat exchangers.

9. The method of claim 8, wherein the one or more heat exchangers are positioned within a cold box.

10. The method of any one of claims 1 to 9, the method further comprising heating the coolant stream in one or more heat exchangers.

11. The method of any one of claims 1 to 10, wherein separating the heavy second separator effluent stream in the third separation unit forms at least the light third separator effluent stream, an intermediate third separator effluent stream, and the heavy third separator effluent stream.

12. The method of claim 11, the method further comprising: reducing a pressure of the intermediate third separator effluent stream to at least partially vaporize the intermediate third separator effluent stream to form a second coolant stream; and passing the second coolant stream through one or more heat exchangers to provide cooling to the one or more heat exchangers.

13. The method of claim 12, wherein the one or more heat exchangers are positioned within a cold box.

14. The method of any one of claims 1 to 13, the method further comprising passing a stream comprising alkanes through the one or more heat exchangers to provide cooling in the one or more heat exchangers.

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