Methods for separating hydrocarbons

Abstract

Methods for separating a mixed feed stream may include compressing and cooling the mixed feed stream; separating the 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; passing the second vapor stream through one or more heat exchangers to produce a warmed second vapor stream; reducing a pressure of the warmed second vapor stream in a turbo-expander, wherein work is extracted from the warmed second vapor stream to form a second coolant stream; and using the work from the turbo-expander to drive a generator, drive a turbo-compressor, or both.

Description

METHODS FOR SEPARATING HYDROCARBONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 583,442 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 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. Some of these streams may undergo a pressure reduction and be used as coolant streams in heat exchangers of the separation process. During pressure reduction of some of these streams, work may be extracted from the streams using a turbo-expander. The work extracted from a stream using the turbo-expander may be used to compress a recycle stream that may be passed to a downstream stage of a compressor system, which may reduce the size of the compressors needed to compress the mixed feed stream, and which may reduce the energy required to compress the mixed feed stream and the recycle stream. Furthermore, the work from the turbo-expander may be used to generate electricity, which may reduce the need for external electricity.

[0005] 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 feed stream, wherein the mixed feed stream comprises one or more of C2, C3, or C4 hydrocarbons; cooling the compressed mixed feed stream to form a cooled mixed feed stream; 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; passing the second vapor stream through one or more heat exchangers to produce a warmed second vapor stream; separating the second liquid stream to form at least a light fraction, a recycle stream, an a heavy fraction; reducing a pressure of the recycle stream to at least partially vaporize the recycle stream to form a first coolant stream; passing the first coolant stream through the one or more heat exchangers to form a warmed recycle stream; reducing a pressure of the warmed second vapor stream in a turbo-expander, wherein work is extracted from the warmed second vapor stream to form a second coolant stream; passing the second coolant stream through the one or more heat exchangers to provide cooling in the one or more heat exchangers; and using the work from the turbo-expander to drive a generator, drive a turbo-compressor, or both.

[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; and

[0009] FIG. 2 schematically depicts a system for separating hydrocarbons, according to one or more embodiments disclosed herein.

[0010] 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.

[0011] 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

[0012] One or more non-limiting embodiments of methods for separating a mixed feed stream are described herein. 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 103. The mixed feed stream 100 may be compressed in one or more compressors. In one or more embodiments, the mixed feed stream 100 may be compressed in an initial compressor 406 and a downstream compressor 408, where the initial compressor 406 and the downstream compressor 408 are arranged in series. For example, in the embodiment depicted in FIG. 1, the mixed feed stream 100 may be compressed in an initial compressor 406 to form stream 101, and stream 101 may be further compressed in downstream compressor 408 to form compressed mixed feed stream 103. It should be understood that the number of compressors arranged in series is not necessarily limited. In one or more embodiments, the mixed feed stream 100 may be compressed in an initial compressor 406 and one or more downstream compressors arranged in series. For example, the mixed feed stream 100 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 one or more of C2, C3, or C4 hydrocarbons. In some embodiments, the mixed feed stream 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 moreembodiments, 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.

[0014] In one or more embodiments, the compressed mixed feed stream 103 may have a temperature from 10 °C to 75 °C. For example, the compressed mixed feed stream 103 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 compressed mixed feed stream 103 may have a pressure from 250 psig to 500 psig. For example, the compressed mixed feed stream 103 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.

[0015] In one or more embodiments, the method for separating the mixed feed stream 100 may comprise cooling the compressed mixed feed stream 103 to form a cooled mixed feed stream 102. The compressed mixed feed stream 103 may be cooled in any suitable heat exchanger. The compressed mixed feed stream 103 may occur in one or more heat exchangers. In some embodiments, the compressed mixed feed stream 103 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 103 may occur in the second heat exchanger 202. In one or more embodiments, cooling the compressed mixed feed stream 103 may condense at least a portion of the compressed mixed feed stream 103.

[0016] 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 abrazed 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.

[0017] 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.

[0018] 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, 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.

[0019] 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. The first vapor stream 104 may be cooled in one or more heat exchangers. In some embodiments, the first vapor stream 104 may be cooled in a heat exchanger positioned within cold box 220. In one or more embodiments, the first vapor stream 104 may be cooled in the first heat exchanger 200.

[0020] 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.

[0021] 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. In one or more embodiments, the second vapor stream 110 may comprise at least 50 wt.% of one or more of hydrogen, nitrogen, methane, carbon monoxide, and carbon dioxide. For example, the second vapor stream 110 may comprise at least 50 wt.%, 55 wt.%, 60 wt.%, 65 wt.%, 70 wt.%, 75 wt.%, 80 wt.%, or 85 wt.%, of one or more of hydrogen, nitrogen, methane, carbon monoxide, and carbon dioxide.

[0022] In one or more embodiments, the second liquid stream 112 may be passed to a fractionation system 304. The second liquid stream 112 may be passed through one or more heat exchangers before being passed to the fractionation system 304. Passing the second liquid stream 112 through one or more heat exchangers may warm the second liquid stream 112 and may provide cooling to the one or more heat exchangers. In some embodiments, the second liquid stream 112 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 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 fractionation system 304.

[0023] 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, thefractionation 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 or cooling steps between the separators.

[0024] In one or more embodiments, the second liquid stream 112 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.

[0025] 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 fraction126 and form a cooled light fraction 127. The pressure of the light fraction 126 may be reduced by 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.

[0026] 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 liquid stream 112 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 thesecond liquid stream 112 may be separated into the light fraction 126, the recycle stream 128, and the heavy fraction 131.

[0027] 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 first coolant stream 130. In one or more embodiments, the pressure of the recycle stream 128 may be reduced by passing the recycle stream 128 through valve 500.

[0028] 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.

[0029] In one or more embodiments, the first coolant stream 130 may have a pressure from 5 psig to 200 psig. For example, the first 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 one or more embodiments, the first coolant stream 130 may have a temperature from -130 °C to 0 °C. For example, the firstcoolant 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.

[0030] Still referring to FIG. 1, the first coolant stream 130 may be passed through one or more heat exchangers to form a warmed recycle stream 136. In one or more embodiments, one or more of the heat exchangers may be positioned within the cold box 220. In one or more embodiments, at least a portion of the first coolant stream 130 may be vaporized in the one or more heat exchangers. In one or more embodiments, at least 80 wt.% of the warmed recycle stream 136 may be vapor. 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 136 may be fully vaporized.

[0031] In some embodiments, as depicted in FIG. 1, the first coolant stream 130 may be passed through the first heat exchanger 200 to provide cooling in the first heat exchanger 200 and to form stream 134. Stream 134 may be passed through the second heat exchanger 202 to provide cooling to the second heat exchanger and produce warmed recycle stream 136.

[0032] Still referring to FIG. 1, in one or more embodiments, methods for separating a mixed feed stream 100 may include passing the second vapor stream 110 through one or more heat exchangers to provide cooling in the one or more heat exchanger and to produce a warmed second vapor 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 second vapor 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 second vapor stream 120.

[0033] In one or more embodiments, a pressure of the warmed second vapor stream 120 may be reduced in a turbo-expander 402 to form a second coolant stream 122. The turbo-expander may extract work from the warmed second vapor stream 120 when the pressure of the warmed second vapor stream 120 is reduced. Reducing the pressure of the warmed second vapor stream 120 and extracting work from the warmed second vapor stream 120 in the turbo-expander may reduce the temperature of the warmed second vapor stream 120.

[0034] As described herein, a “turbo-expander” may be a system component or multiple system components suitable for reducing the pressure of a process stream and extracting work from that process stream. In some embodiments, a turbo-expander may be mechanically linked to a turbo-compressor such that work extracted by the turbo-expander may at least partially drive the turbo-compressor. In some embodiments, a turbo-expander may be mechanically linked to a generator such that work extracted by the turbo-expander may be used to generate electricity.

[0035] As described herein, “work” refers to energy transferred to or from an object by the application of force along a displacement. For example, work may be extracted from the warmed second vapor stream 120 when the warmed second vapor stream 120 causes a component of the turbo-expander 402 to move, such as causing a turbine in the turbo-expander 402 to spin. Power refers to the amount of work performed over a period of time. For example, the rate at which work is extracted from the warmed second vapor stream 120 may be expressed in terms of power.

[0036] In one or more embodiments, the second 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 second coolant stream 122 through one or more heat exchangers may produce an off-gas stream 125, which may exit the system. Referring still to FIG. 1, in one or more embodiments, second 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 be passed through the second heat exchanger 202 to provide cooling to the second heat exchanger 202 and form off-gas stream 125.

[0037] Still referring to FIG. 1, the work extracted from the warmed second vapor stream 120 by the turbo-expander 402 may be used to drive a turbo-compressor 404. In one or more embodiments, the warmed recycle stream 136 may be compressed in turbo-compressor 404 to form a compressed recycle stream 138. In one or more embodiments, the compressed recycle stream 138 may be passed from the turbo-compressor 404 to the downstream compressor 408. In such embodiments, stream 101 and the compressed recycle stream 138 may be compressed in the downstream compressor 408 to form the compressed mixed feed stream 103. In embodiments comprising multiple downstream compressors, the compressed recycle stream 138 may be passed to any one of the downstream compressors or even more than one of the downstream compressors.

[0038] As described herein, a “turbo-compressor” may be a system component or multiple system components suitable for increasing the pressure of a process stream. A turbo-compressor may be mechanically linked to a turbo-expander. Work extracted by the turbo-expander may be used to compress one or more process streams in the turbo-compressor. In some embodiments, the turbo-compressor may make use of other sources of energy or work, such as energy or work from an electric motor, in addition to work extracted by the turbo-expander.

[0039] Without intending to be bound by theory, using the work extracted from the warmed second vapor stream 120 in the turbo-expander 402 to compress the warmed recycle stream 136 may reduce the size of the compressors used to compress the mixed feed stream 100 relative to a system where the warmed recycle stream 136 is not compressed. Compressing the warmed recycle stream 136 in the turbo-compressor 404 may increase the pressure of the compressed recycle stream 138 such that the compressed recycle stream 138 may be passed to one or more downstream compressors, such as downstream compressor 408. This may allow the initial compressor 406 to be smaller, which may reduce the capital requirements for the compressor. Additionally, compressing the warmed recycle stream 136 before passing the stream to the compressors may reduce the work required to compress the mixed feed stream 100 and the recycle stream in the compressors, relative to a system where the warmed recycle stream 136 is not compressed in a turbo-compressor 404 driven by work extracted from the warmed second vapor stream 120. Accordingly, without intending to be bound by theory, using work extracted from the warmed second vapor stream 120 to compress the warmed recycle stream 136 before the stream is passed to the compressors may reduce the capital cost of the compressors and reduce the work and energy required to compress the mixed feed stream and the recycle stream in the compressors.

[0040] Referring now to FIG. 2, in one or more embodiments, the work extracted from the warmed second vapor stream 120 by the turbo-expander 402 may be used to drive a generator 410. In one or more embodiments, the generator 410 may produce electricity from the work extracted from the warmed second vapor stream 120 by the turbo-expander. The electricity 140 may be passed from the generator 410 to an electric grid. The electricity 140 passed to the electric grid may be used in any piece of process equipment that requires electricity and is connected to the electric grid. For example, without limitation, at least a portion of the electricity 140 passed to the electric grid may be used to power the initial compressor 406 and / or the downstream compressor 408, along with any other piece of process equipment connected to the electric grid.

[0041] Without intending to be bound by theory, using the work extracted from the warmed second vapor stream 120 in the turbo-expander 402 to generate electricity 140 may reduce the need for external sources of electricity to power any system components connected to the electric grid. This may reduce the cost of providing electricity to the system from external sources.

[0042] Still referring to FIG. 2, the warmed recycle stream 136 may be passed from a heat exchanger to the initial compressor 406. In one or more embodiments, the warmed recycle stream 136 may be passed from the second heat exchanger 202 to the initial compressor 406. The warmed recycle stream 136 and the mixed feed stream 100 may be compressed in the initial compressor 406 to form stream 101 and stream 101 may be compressed in the downstream compressor 408 to form the compressed mixed feed stream 103.

[0043] In some embodiments described herein, and as depicted in FIGs. 1 and 2, 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

[0044] 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.

[0045] Example 1

[0046] 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.

[0047] As shown in Example 1, the turbo-expander may be used to extract work from the warmed second vapor stream 120, reduce the pressure of the warmed second vapor stream 120 and cool the warmed second vapor stream 120. The work extracted from the warmed second vapor stream 120 may be used to drive a turbo-compressor 404 to compress the warmed recycle stream 136, so a compressed recycle stream 138 may be passed to the downstream compressor 408. It should be noted that not every stream labeled in FIG. 1 and described hereinabove is listed in Table 1.

[0048] Example 2

[0049] Example 2 was conducted using an integrated separation train process model in Aspen plus for the recovery system depicted in FIG. 2. Table 2 shows temperatures, pressures, and mass fractions ratios of streams depicted in FIG. 2. The numbering of the streams included in Table 2 is consistent with the numbering of the streams in FIG. 2 and the numbering used throughout the detailed description.Table 2.Table 2 Cont.

[0050] As shown in Example 2, the turbo-expander may be used to extract work from the warmed second vapor stream 120, reduce the pressure of the warmed second vapor stream 120 and cool the warmed second vapor stream 120. The work extracted from the warmed second vapor stream 120 may be used to drive a generator 410. According to the model, work was generated by the generator 410 at a rate of 920 hp. It should be noted that not every stream labeled in FIG. 2 and described hereinabove is listed in Table 2.

[0051] 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.”

[0052] 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.

[0053] 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.

[0054] 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: compressing the mixed feed stream to form a compressed feed stream, wherein the mixed feed stream comprises 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 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; passing the second vapor stream through one or more heat exchangers to produce a warmed second vapor stream; separating 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 first coolant stream; passing the first coolant stream through the one or more heat exchangers to form a warmed recycle stream; reducing a pressure of the warmed second vapor stream in a turbo-expander, wherein work is extracted from the warmed second vapor stream to form a second coolant stream; passing the second coolant stream through the one or more heat exchangers to provide cooling in the one or more heat exchangers; and using the work from the turbo-expander to drive a generator, drive a turbo-compressor, or both.

2. The method of claim 1, wherein the method comprises using the work from the turboexpander to drive the turbo-compressor.

3. The method of claim 2, further comprising compressing the warmed recycle stream in the turbo-compressor to form a compressed recycle stream.

4. The method of claim 3, wherein compressing the mixed feed stream occurs in at least an initial compressor and one or more downstream compressors arranged in series, and wherein the compressed recycle stream is passed from the turbo-compressor to one or more of the downstream compressors.

5. The method of claim 1, wherein the method comprises using the work from the turbo expander to drive the generator.

6. The method of claim 5, wherein using the work from the turbo expander to drive the generator produces electricity and wherein the electricity is passed to an electric grid.

7. The method of claim 6, wherein compressing the mixed feed stream occurs in a first compressor and a second compressor arranged in series, and wherein the warmed recycle stream is passed from the one or more heat exchangers to the first compressor.

8. The method of any one of claims 1 to 7, wherein the mixed feed stream comprises at least 70 wt.% C2 to C4 hydrocarbons.

9. The method of any one of claims 1 to 8, wherein the second vapor stream comprises at least 50 wt.% of one or more of hydrogen, nitrogen, methane, carbon monoxide, and carbon dioxide.

10. The method of any one of claims 1 to 9, further comprising passing the second liquid stream through the one or more heat exchangers before separating the second liquid stream to form at least the light fraction, the recycle stream, and the heavy fraction.

11. The method of any one of claims 1 to 10, wherein one or more of the heat exchangers are positioned within a cold box.

12. The method of any one of claims 1 to 10, wherein the first coolant stream is passed through a first heat exchanger and a second heat exchanger to provide cooling to the first heat exchanger and the second heat exchanger.

13. The method of claim 12, wherein the second coolant stream is passed through the first heat exchanger and the second heat exchanger to provide cooling to the first heat exchanger and the second heat exchanger.

14. The method of claim 12 or claim 13, wherein cooling the first vapor stream occurs in one or more heat exchangers.

15. The method of any one of claims 11 to 14, wherein the second vapor stream is passed through the first heat exchanger to provide cooling to the first heat exchanger.

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