Methods for separating hydrocarbons

Abstract

Methods for separating a mixed feed stream may include separating the mixed feed stream into a first vapor stream and a first liquid stream; cooling the first vapor stream; separating the cooled stream into a second vapor stream and a second liquid stream; reducing a pressure of a first portion of the second liquid stream to form a first coolant stream; separating a second portion of the second liquid stream to form a recycle stream; reducing a pressure of the recycle stream to form a second coolant stream; passing the first coolant stream through a first heat exchanger to form a first warmed stream; passing the second coolant stream through the first heat exchanger to form a second warmed stream; combining the first warmed stream and the second warmed stream to form a third coolant stream; and passing the third coolant stream through a second heat exchanger.

Description

METHODS FOR SEPARATING HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 583,428 filed September 18, 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 a cryogenic separation processes, a mixed feed stream may be cooled by heat exchange with other process streams and / or external sources of refrigeration. As the mixed feed stream is cooled, liquid streams comprising various fractions of the mixed feed stream may be collected as high pressure liquid streams. Some of these streams may undergo a pressure reduction and be used as coolant streams in heat exchangers of the separation process. However, using these streams as coolant in multiple heat exchangers arranged in series in the separation process may result in temperature pinches within one or more of the heat exchangers. As described in further detail herein, a “temperature pinch” may occur when a difference in temperature between a hot stream and a cold stream in a heat exchanger approaches zero. Accordingly, there is a need for improved processes for separating a mixed feed stream where process streams are used for cooling. These needs may be met by embodiments of the present disclosure.

[0005] According to one or more embodiments of the present disclosure, a method for separating a mixed feed stream may comprise cooling the mixed feed stream to form a cooledmixed feed stream, wherein the mixed feed stream comprises one or more of C2, C3, and C4 hydrocarbons; separating the cooled mixed feed stream into a first vapor stream and a first liquid stream; cooling the first vapor stream to form a cooled stream; separating the cooled stream into a second vapor stream and a second liquid stream; reducing a pressure of a first portion of the second liquid stream to at least partially vaporize the first portion of the second liquid stream and form a first coolant stream; separating a second portion of the second liquid stream to form at least a light fraction, a recycle stream, and a heavy fraction; reducing a pressure of the recycle stream to at least partially vaporize the recycle stream to form a second coolant stream; passing the first coolant stream through a first heat exchanger to provide cooling in the first heat exchanger and to form a first warmed stream; passing the second coolant stream through the first heat exchanger to provide cooling in the first heat exchanger and to form a second warmed stream; combining the first warmed stream and the second warmed stream to form a third coolant stream; and passing the third coolant stream through a second heat exchanger to provide cooling in the second heat exchanger.

[0006] Additional features and advantages of the technology disclosed herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the technology as described herein, including the detailed description which follows, the claims, as well as the appended drawings.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.

[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 presentembodiments 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. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts.DETAILED DESCRIPTION

[0011] One or more non-limiting embodiments of methods for separating a mixed feed stream are described herein. As described herein, methods for separating hydrocarbons may include using multiple process streams as coolant in heat exchangers. After using the process streams as coolant in a first heat exchanger, the process streams may be combined before being used as coolant in a second heat exchanger. Without intending to be bound by theory, combining the process streams before using the process streams as coolant in the second heat exchanger may prevent temperature pinches in the second heat exchanger. These advantages, as well as others, are described in detail hereinbelow.

[0012] Referring now to FIG. 1, a method for separating a mixed feed stream 100 may comprise cooling the mixed feed stream 100 to form a cooled mixed feed stream 102. The mixed feed stream 100 may be cooled in any suitable heat exchanger. In one or more embodiments, cooling the mixed feed stream 100 may occur in the second heat exchanger 202. In one or more embodiments, cooling the mixed feed stream 100 may condense at least a portion of the mixed feed stream 100. In some embodiments, the mixed feed stream 100 may be cooled in a heat exchanger positioned within cold box 220.

[0013] 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.

[0014] In one or more embodiments, the mixed feed stream 100 may comprise at least 70 wt.% C2 to 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 C2 to C4 hydrocarbons. In one or more embodiments, the C2 to 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, carbon monoxide, and carbon dioxide. In some embodiments, the mixed feed stream may comprise from 0.1 wt.% to 15 wt.% N2, from 0.01 wt.% to 10 wt.% H2, from 0.01 wt.% to 10 wt.% methane, and from 70 wt.% to 99 wt.% one or more of C2, C3, or C4 components.

[0015] In one or more embodiments, the mixed feed stream 100 may have a temperature from 10 °C to 75 °C. For example, the mixed feed stream 100 may have a temperature from 10 °C to 75 °C, from 20 °C to 75 °C, from 30 °C to 75 °C, from 40 °C to 75 °C, from 50 °C to 75 °C, from 60 °C to 75 °C, from 70 °C to 75 °C, from 10 °C to 65 °C, from 10 °C to 55 °C, from 10 °C to 45 °C, from 10 °C to 35 °C, from 10 °C to 25 °C, from 10 °C to 20 °C, from 10 °C to 15 °C, or any range or combination of ranges formed from these endpoints. In one or more embodiments, the mixed feed stream may have a pressure from 250 psig to 500 psig. For example, the mixed feed stream 100 may have a pressure from 250 psig to 500 psig, from 300 psig to 500 psig, from 350 psig to 500 psig, from 400 psig to 500 psig, from 450 psig to 500 psig, from 250 psig to 450 psig, from 250 psig to 400 psig, from 250 psig to 350 psig, from 250 psig to 300 psig, or any range or combination of ranges formed from these endpoints.

[0016] In one or more embodiments, the cooled mixed feed stream 102 may be separated into a first vapor stream 104 and a first liquid stream 106. The cooled mixed feed stream 102 may be separated into the first vapor stream 104 and a first liquid stream 106 in separator 300. Separator 300 may be any suitable separator.

[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. Examples of separators include, without limitation, distillation columns, flash drums, knock-out drums, knock-out pots, traps, scrubbers, expansion devices, membranes, solvent extraction devices, andthe 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 first vapor stream 104 may be cooled to form a cooled stream 108. In some embodiments, the cooled stream 108 may be partially condensed, and in some embodiments, the cooled stream 108 may be fully condensed. In one or more embodiments, the first vapor stream 104 may be cooled in the first heat exchanger 200. In some embodiments, the first vapor stream may 104 be cooled in a heat exchanger positioned within cold box 220.

[0019] In one or more embodiments, the cooled stream 108 may have a temperature from - 150 °C to 0 °C. For example, the cooled stream 108 may have a temperature from -150 °C to 0 °C, from -130 °C to 0 °C, from -110 °C to 0 °C, from -90 °C to 0 °C, from -70 °C to 0 °C, from - 50 °C to 0 °C, from -30 °C to 0 °C, from -10 °C to 0 °C, from -150 °C to -20 °C, from -150 °C to -40 °C, from -150 °C to -60 °C, from -150 °C to -80 °C, from -150 °C to -100 °C, from -150 °C to -120 °C, from -150 °C to -140 °C, or any range or combination of ranges formed from these endpoints.

[0020] Still referring to FIG. 1, the cooled stream 108 may be separated into a second vapor stream 110 and a second liquid stream 112. The cooled stream 108 may be separated into the second vapor stream 110 and the second liquid stream 112 in separator 302. Separator 302 may be any suitable separator. In one or more embodiments, the second liquid stream 112 may comprise C2, C3, or C4 hydrocarbons or a combination thereof.

[0021] In one or more embodiments, the second vapor stream 110 may comprise one or more of hydrogen, nitrogen, methane, carbon monoxide, and carbon dioxide. The second vapor stream may be passed through one or more heat exchangers to provide cooling to one or more heat exchangers. Referring to FIG. 1, in one or more embodiments, the second vapor stream 110 may be passed from separator 302 to the first heat exchanger 200 to provide cooling to the first heatexchanger 200 and produce a warmed second vapor stream 120. In one or more embodiments, the warmed second vapor stream 120 may be expanded in expander 402 to produce an expanded vapor stream 122. The expanded vapor stream 122 may be passed to the first heat exchanger 200 to provide cooling to the first heat exchanger 200. In one or more embodiments, the expanded vapor stream 122 may be passed to the second heat exchanger 202 to provide cooling to the second heat exchanger 202. In the embodiment depicted in FIG. 1, the expanded vapor stream 122 may be passed to the first heat exchanger 200 to form stream 123, and stream 123 may subsequently be passed to the second heat exchanger 202 to provide cooling to the first heat exchanger 200 and the second heat exchanger 202. Stream 125 may exit the system from the second heat exchanger 202 as off-gas after being used for cooling in the second heat exchanger 202.

[0022] In one or more embodiments, a pressure of a first portion of the second liquid stream114 may be reduced to at least partially vaporize the first portion of the second liquid stream 114 and form a first coolant stream 116. In one or more embodiments, the pressure of the first portion of the second liquid stream 114 may be reduced by passing the first portion of the second liquid stream 114 through a valve 500.

[0023] In one or more embodiments, the first portion of the second liquid stream 114 may have a pressure from 200 psig to 480 psig. For example, the first portion of the second liquid stream 114 may have a pressure from 200 psig to 480 psig, from 225 psig to 480 psig, from 250 psig to 480 psig, from 275 psig to 480 psig, from 300 psig to 480 psig, from 325 psig to 480 psig, from 350 psig to 480 psig, from 375 psig to 480 psig, from 400 psig to 480 psig, from 425 psig to 480 psig, from 450 psig to 480 psig, from 200 psig to 450 psig, from 200 psig to 425 psig, from 200 psig to 400 psig, from 200 psig to 375 psig, from 200 psig to 350 psig, from 200 psig to 325 psig, from 200 psig to 300 psig, from 200 psig to 275 psig, from 200 psig to 250 psig, from 200 psig to 225 psig, or any range or combination of ranges formed from these endpoints. In one or more embodiments, the first portion of the second liquid stream 114 may have a temperature from -150 °C to 0 °C. For example, first portion of the second liquid stream 114 may have a temperature from -150 °C to 0 °C, from -130 °C to 0 °C, from -110 °C to 0 °C, from -90 °C to 0 °C, from -70 °C to 0 °C, from -50 °C to 0 °C, from -30 °C to 0 °C, from -10 °C to 0 °C, from -150 °C to -20 °C, from -150 °C to -40 °C, from -150 °C to -60 °C, from -150 °C to -80 °C, from -150 °C to - 100 °C, from -150 °C to -120 °C, from -150 °C to -140 °C, or any range or combination of ranges formed from these endpoints.

[0024] In one or more embodiments, first coolant stream 116 may have a temperature from -150 °C to -30 °C. For example, the first coolant stream 116 may have a temperature from -150 °C to -30 °C, from -130 °C to -30 °C, from -110 °C to -30 °C, from -90 °C to -30 °C, from -70 °C to -30 °C, from -50 °C to -30 °C, from -150 °C to -50 °C, from -150 °C to -70 °C, from -150 °C to -90 °C, from -150 °C to -110 °C, from -150 °C to -130 °C, or any range or combination of ranges formed from these endpoints. In one or more embodiments, a temperature difference between the first portion of the second liquid stream 114 and the first coolant stream 116 may be less than or equal to 15 °C, 10 °C, 5 °C, or even 1 °C. In some embodiments, the first portion of the second liquid stream 114 and the first coolant stream 116 may have substantially the same temperature. In one or more embodiments, the first coolant stream 116 may have a pressure from 0 psig to 100 psig. For example, the first coolant stream 116 may have a pressure from 0 psig to 100 psig, from 20 psig to 100 psig, from 40 psig to 100 psig, from 60 psig to 100 psig, from 80 psig to 100 psig, from 0 psig to 90 psig, from 0 psig to 70 psig, from 0 psig to 50 psig, from 0 psig to 30 psig, from 0 psig to 10 psig, or any range or combination of ranges formed from these endpoints.

[0025] The first coolant stream 116 may be passed through the first heat exchanger 200 to provide cooling in the first heat exchanger 200 and form a first warmed stream 124. It should be noted that in one or more embodiments, the first coolant stream 116 may be passed through one or more heat exchangers to form the first warmed stream 124. In one or more embodiments, at least a portion of the first coolant stream 116 may be vaporized in the first heat exchanger. In one or more embodiments, at least 80 wt.% of the first warmed stream 124 may be vapor. For example, at least 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.% or even 99 wt.% of the first warmed stream 124 may be vapor. In some embodiments, the first warmed stream 124 may be fully vaporized.

[0026] In one or more embodiments, a second portion of the second liquid stream 118 may be passed to a fractionation system 304. The second portion of the second liquid stream 118 may be passed through one or more heat exchangers before being passed to the fractionation system 304. Passing the second portion of the second liquid stream 118 through one or more heat exchangers may warm the second portion of the second liquid stream 118 and may provide cooling to the one or more heat exchangers. In some embodiments, the second portion of the second liquid stream 118 may be passed through the first heat exchanger 200 to provide cooling to the first heat exchanger 200. In some embodiments, the second liquid stream 118 may be passed through thesecond 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 118 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 fractionation system 304.

[0027] 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 fractionation system 304 may be a multi-stage fractionation system. In such embodiments, the fractionation system 304 may comprise multiple fractionation devices in series. For example, the fractionation system 304 may comprise multiple separators and may include reflux or recycle streams between the separators.

[0028] In one or more embodiments, the second portion of the second liquid stream 118 may be separated into a light fraction 126, a recycle stream 128, and a heavy fraction 131. In one or more embodiments, the light fraction 126 may comprise C2 hydrocarbons. For example, the light fraction 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. In one or more embodiments, the recycle stream 128 may comprise one or more of C2 and C3 hydrocarbons. For example, the recycle 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.% of one or more of C2 and C3 hydrocarbons. In one or more embodiments, the heavy fraction 131 may comprise C3+ hydrocarbons. For example, the heavy fraction 131 may comprise at least 50 wt.%, at least 60 wt.%, at least 70 wt.%, at least 80 wt.%, at least 90 wt.% or even at least 95 wt.% C3+ hydrocarbons. In one or more embodiments, the heavy fraction 131 may be passed from the system to a C3 separation system.

[0029] In one or more embodiments, the light fraction 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 fraction 126 may exit the system. In some embodiments, as depicted in FIG. 1, the pressure of the light fraction 126 may be reduced to cool the light fraction 126 and form a cooled light fraction 127. The pressure of the light fraction 126 may be reducedby passing the light fraction 126 through valve 504. In such embodiments, the cooled light fraction127 may be passed to the second heat exchanger 202 to provide cooling to the second heat exchanger 202. The cooled light fraction 127 may be warmed in the second heat exchanger 202 and may exit the system through stream 129.

[0030] In one or more embodiments, the first liquid stream 106 may also be passed to the fractionation system 304. In some embodiments, the first liquid stream 106 may be passed from separator 300 to the fractionation system 304. In some embodiments, as depicted in FIG. 1, the first liquid stream 106 may be combined with the second portion of the second liquid stream 118 upstream of the fractionation system 304 to form a fractionator feed stream 119. In embodiments where the first liquid stream 106 is passed to the fractionation system 304, the first liquid stream 106 and the second portion of the second liquid stream 118 may be separated into the light fraction 126, the recycle stream 128, and the heavy fraction 131.

[0031] Still referring to FIG. 1, a pressure of the recycle stream 128 may be reduced to at least partially vaporize the recycle stream 128 to form a second coolant stream 130. In one or more embodiments, the pressure of the recycle stream 128 may be reduced by passing the recycle stream128 through valve 502.

[0032] In one or more embodiments, the recycle stream 128 may have a pressure from 200 psig to 450 psig. For example, the recycle stream 128 may have a pressure from 200 psig to 450 psig, from 225 psig to 450 psig, from 250 psig to 450 psig, from 275 psig to 450 psig, from 300 psig to 450 psig, from 325 psig to 450 psig, from 350 psig to 450 psig, from 375 psig to 450 psig, from 400 psig to 450 psig, from 425 psig to 450 psig, from 200 psig to 425 psig, from 200 psig to 400 psig, from 200 psig to 375 psig, from 200 psig to 350 psig, from 200 psig to 325 psig, from 200 psig to 300 psig, from 200 psig to 275 psig, from 200 psig to 250 psig, from 200 psig to 225 psig or any range or combination of ranges formed from these endpoints. In one or more embodiments, the recycle stream 128 may have a temperature from -120 °C to 100 °C. For example, the recycle stream 128 may have a temperature from -120 °C to 100 °C, from -100 °C to 100 °C, from -80 °C to 100 °C, from -60 °C to 100 °C, from -40 °C to 100 °C, from -20 °C to 100 °C, from 0 °C to 100 °C, from 20 °C to 100 °C, from 40 °C to 100 °C, from 60 °C to 100 °C, from 80 °C to 100 °C, from -120 °C to 90 °C, from -120 °C to 70 °C, from -120 °C to 50 °C, from -120 °C to 30 °C, from -120 °C to 10 °C, from -120 °C to -10 °C, from -120 °C to -30 °C, from -120 °C to -50 °C, from -120 °C to -70 °C, from -120 °C to -90 °C, from -120 °C to -110 °C, or any range or combination of ranges formed from these endpoints.

[0033] In one or more embodiments, the second coolant stream 130 may have a pressure from 5 psig to 200 psig. For example, the second coolant stream 130 may have a pressure from 5 psig to 200 psig, from 5 psig to 200 psig, from 25 psig to 200 psig, from 50 psig to 200 psig, from 75 psig to 200 psig, from 100 psig to 200 psig, from 125 psig to 200 psig, from 150 psig to 200 psig, from 175 psig to 200 psig, from 5 psig to 175 psig, from 5 psig to 150 psig, from 5 psig to 125 psig, from 5 psig to 100 psig, from 5 psig to 75 psig, from 5 psig to 50 psig, from 5 psig to 25 psig, or any range or combination of ranges formed from these endpoints. In some embodiments, the first coolant stream 116 and the second coolant stream 130 may have substantially the same pressure. In one or more embodiments, the second coolant stream 130 may have a temperature from -130 °C to 0 °C. For example, the second coolant stream 130 may have a temperature from -130 °C to 0 °C, from -110 °C to 0 °C, from -90 °C to 0 °C, from -70 °C to 0 °C, from -50 °C to 0 °C, from -30 °C to 0 °C, from -10 °C to 0 °C, from -130 °C to -20 °C, from -130 °C to -40 °C, from -130 °C to -60 °C, from -130 °C to -80 °C, from -130 °C to -100 °C, from -130 °C to -120 °C, or any range or combination of ranges formed from these endpoints.

[0034] Still referring to FIG. 1, the second coolant stream 130 may be passed through the first heat exchanger 200 to provide cooling in the first heat exchanger 200 and to form a second warmed stream 132. It should be noted that in some embodiments, the second coolant stream 130 may be passed through one or more heat exchangers to form the second warmed stream 132. In one or more embodiments, at least a portion of the second coolant stream 130 may be vaporized in the first heat exchanger 200. In one or more embodiments, at least 80 wt.% of the second warmed stream 132 may be vapor. For example, at least 80 wt.%, 85 wt.%, 90 wt.%, 95 wt.% or even 99 wt.% of the second warmed stream 132 may be vapor. In some embodiments, the second warmed stream 132 may be fully vaporized.

[0035] In one or more embodiments, the first warmed stream 124 and the second warmed stream 132 may be combined to form a third coolant stream 134. In one or more embodiments, the first warmed stream 124 and the second warmed stream 132 may have substantially the same temperature and pressure when they are combined to form the third coolant stream 134.

[0036] Without intending to be bound by theory, combining the first warmed stream 124 and the second warmed stream 132 may prevent temperature pinches in the second heat exchanger 202. As used in the present application, a “temperature pinch” refers to a point in a heat exchanger where a difference in temperature between the hot fluid and the cold fluid is at or near zero. If a temperature pinch occurs, cooling in the heat exchanger may be insufficient. Without intending to be bound by theory, the first coolant stream 116 supplies cooling duty to cold box 220, resulting in first warmed stream 124. Mixing the first warmed stream 124 and the second warmed stream 132 may result in a third coolant stream 134 with a different composition and a reduced boiling temperature relative to the first warmed stream 124. This may improve the performance of the third coolant stream 134 as a coolant in the second heat exchanger 202, relative to the performance of the first warmed stream 124 and the second warmed stream 132 used as coolants individually in the second heat exchanger 202. This allows the third coolant stream 134 to provide sufficient cooling to the second heat exchanger 202 by avoiding temperature pinches in the second heat exchanger 202.

[0037] The third coolant stream 134 may be passed through the second heat exchanger 202 to provide cooling in the second heat exchanger 202. In some embodiments, the third coolant stream 134 may be warmed in the second heat exchanger 202 to produce a warmed stream 136. In one or more embodiments, the warmed stream may exit the cold box 220. In some embodiments, the warmed stream may be passed to one or more heat exchangers to provide cooling in the heat exchangers.

[0038] In some embodiments described herein, and as depicted in FIG. 1, the first heat exchanger 200 and second heat exchanger 202 may each be positioned within cold box 220. In one or more embodiments, not depicted, the first and second heat exchangers may be positioned within separate cold boxes based on the cooling needs of the system.EXAMPLES

[0039] Various embodiments of the processes and systems for separating a mixed feed stream will be further clarified in the following Example. The Example is illustrative in nature, and should not be understood to limit the subject matter of the present disclosure.

[0040] Example 1

[0041] Example 1 was conducted using an integrated separation train process model in Aspen Plus for the recovery system depicted in FIG. 1. Table 1 shows temperatures, pressures, and mass fractions ratios of streams depicted in FIG. 1. The numbering of the streams included in Table 1 is consistent with the numbering of the streams in FIG. 1 and the numbering used throughout the detailed description.Table 1.Table 1 Cont.Table 1 Cont.

[0042] As shown in Example 1, the mixed feed stream 100 may be separated into several hydrocarbon containing stream and those streams may be used for cooling in one or more heat exchangers. It should be noted that not every stream labeled in FIG. 1 and described hereinabove is listed in Table 1.

[0043] 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 a recitation 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.”

[0044] 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.

[0045] 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.

[0046] 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

CLAIMS1. A method for separating a mixed feed stream, the method comprising: cooling the mixed feed stream to form a cooled mixed feed stream, wherein the mixed feed stream comprises one or more of C2, C3, and C4 hydrocarbons; separating the cooled mixed feed stream into a first vapor stream and a first liquid stream; cooling the first vapor stream to form a cooled stream; separating the cooled stream into a second vapor stream and a second liquid stream; reducing a pressure of a first portion of the second liquid stream to at least partially vaporize the first portion of the second liquid stream and form a first coolant stream; separating a second portion of the second liquid stream to form at least a light fraction, a recycle stream, and a heavy fraction; reducing a pressure of the recycle stream to at least partially vaporize the recycle stream to form a second coolant stream; passing the first coolant stream through a first heat exchanger to provide cooling in the first heat exchanger and to form a first warmed stream; passing the second coolant stream through the first heat exchanger to provide cooling in the first heat exchanger and to form a second warmed stream; combining the first warmed stream and the second warmed stream to form a third coolant stream; and passing the third coolant stream through a second heat exchanger to provide cooling in the second heat exchanger.

2. The method of claim 1, wherein the first heat exchanger is positioned within a cold box.

3. The method of claim 1 or claim 2, wherein the second heat exchanger is positioned within a cold box.

4. The method of any one of claims 1 to 3, further comprising: reducing a pressure of the light fraction to form a cooled light fraction; and passing the cooled light fraction through the second heat exchanger to provide cooling in the second heat exchanger.

5. The method of any one of claims 1 to 4, further comprising passing the second vapor stream through one or more heat exchangers to provide cooling in the one or more heat exchangers.

6. The method of any one of claims 1 to 5, wherein the cooling the mixed feed stream occurs in the second heat exchanger.

7. The method of any one of claims 1 to 6, wherein the cooling the first vapor stream occurs in the first heat exchanger.

8. The method of any one of claims 1 to 7, further comprising passing the second portion of the second liquid stream through one or more heat exchangers before separating the second portion of the second liquid stream to form at least the light fraction, the recycle stream, and the heavy fraction.

9. The method of any one of claims 1 to 8, wherein the mixed feed stream comprises at least 70 wt.% of the one or more of C2, C3, and C4 hydrocarbons.

10. The method of any one of claims 1 to 9, wherein the first portion of the second liquid stream has a temperature from -150 °C to 0 °C and a pressure from 200 psig to 480 psig.

11. The method of any one of claims 1 to 10, wherein the first coolant stream has a temperature from -150 °C to -30 °C and a pressure from 0 psig to 100 psig.

12. The method of any one of claims 1 to 11, wherein the recycle stream has a temperature from -120 °C to 100 °C and a pressure from 200 psig to 450 psig.

13. The method of any one of claims 1 to 12, wherein the second coolant stream has a temperature from -130 °C to 0 °C and a pressure from 5 psig to 200 psig.

14. The method of any one of claims 1 to 13, wherein at least 80 wt.% of the first warmed stream is vapor and at least 80 wt.% of the second warmed stream is vapor.

15. The method of any one of claims 1 to 14, wherein the recycle stream comprises at least 50 wt.% of one or more of C2 and C3 hydrocarbons.

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