Process for separating hydrocarbons

Abstract

A method 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 the pressure of the recirculation stream to form a second coolant stream; passing the first coolant stream through a first heat exchanger to form a first warm stream; passing a second coolant flow through the first heat exchanger to form a second warm flow; combining the first warmed stream and the second warmed stream to form a third coolant stream; and passing the third coolant flow through the second heat exchanger.

Description

Cross-references to related applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 583,428, filed on September 18, 2023, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] The implementation schemes described in this article generally relate to methods and systems for separating hydrocarbons. Background Technology

[0003] Various hydrocarbons, such as ethylene, ethane, propylene, propane, and heavier hydrocarbons, can be recovered from multiple product streams obtained from chemical reactors. Cryogenic separation methods can be used to recover more condensable hydrocarbons from less condensable gases or products. Summary of the Invention

[0004] In cryogenic separation methods, the mixed feed stream can be cooled by heat exchange with other process streams and / or an external refrigeration source. When the mixed feed stream is cooled, the liquid streams comprising various fractions of the mixed feed stream can be collected as high-pressure liquid streams. Some of these streams can undergo pressure reduction and be used as coolant streams in the heat exchangers of the separation process. However, using these streams as coolants in multiple heat exchangers arranged in series during the separation process can lead to temperature pinches within one or more of the heat exchangers. As described further in detail herein, a "temperature pinch" can occur when the temperature difference between the hot and cold streams in the heat exchanger approaches zero. Therefore, there is a need for improved methods for separating mixed feed streams, where the process streams are used for cooling. Embodiments of this disclosure meet these needs.

[0005] According to one or more embodiments of this disclosure, a method for separating a mixed feed stream may include: cooling the mixed feed stream to form a cooled mixed feed stream, wherein the mixed feed stream comprises one or more of C2 hydrocarbons, C3 hydrocarbons, 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 the pressure of a first portion of the second liquid stream to at least partially evaporate the first portion of the second liquid stream and form a first coolant stream; separating the second liquid stream into a second vapor stream and a third liquid stream. The two parts form at least a light fraction, a recirculated stream, and a heavy fraction; the pressure of the recirculated stream is reduced to at least partially evaporate the recirculated stream to form a second coolant stream; the first coolant stream is passed through a first heat exchanger to provide cooling in the first heat exchanger and form a first warm stream; the second coolant stream is passed through the first heat exchanger to provide cooling in the first heat exchanger and form a second warm stream; the first warm stream and the second warm stream are combined to form a third coolant stream; and the third coolant stream is passed through the second heat exchanger to provide cooling in the second heat exchanger.

[0006] Additional features and advantages of the techniques disclosed herein will be set forth in the detailed description below, and will be partly apparent from the description or recognized by those skilled in the art through practice of the techniques as described herein (including the detailed description below, the claims and the drawings). Attached Figure Description

[0007] The following detailed description of specific embodiments of this disclosure is best understood in conjunction with the following drawings, in which similar reference numerals indicate similar structures and in the drawings:

[0008] Figure 1 A system for separating hydrocarbons according to one or more embodiments disclosed herein is schematically depicted.

[0009] It should be understood that the accompanying drawings are schematic in nature and do not include some components commonly used in separation systems in the art, such as, but not limited to, temperature transmitters, pressure transmitters, flow meters, pumps, valves, etc. These components are well known to be within the spirit and scope of the disclosed embodiments. However, operating components (such as those described in this disclosure) may be added to the embodiments described in this disclosure.

[0010] Reference will now be made in more detail to various embodiments, some of which are illustrated in the accompanying drawings. Where possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. Detailed Implementation

[0011] This document describes one or more non-limiting embodiments of a method for separating mixed feed streams. As described herein, a method for separating hydrocarbons may include using multiple process streams as coolants in a heat exchanger. After using a process stream as a coolant in a first heat exchanger, the process streams may be combined before being used as a coolant in a second heat exchanger. Although not intended to be theoretically constrained, combining process streams before using them as coolants in a second heat exchanger can prevent temperature pinch-ups in the second heat exchanger. These, and other advantages, are described in detail below.

[0012] Now for reference Figure 1 A method for separating the mixed feed stream 100 may include 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 of the mixed feed stream 100 may occur in a second heat exchanger 202. In one or more embodiments, cooling of 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 a cold box 220.

[0013] As used in this disclosure, a "cold box" refers to an insulated enclosure that can 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 the cold box. In some embodiments, multiple heat exchangers may be positioned in series within the cold box. Heat exchangers may include brazed heat exchangers, shell-and-tube heat exchangers, twin-tube heat exchangers, plate heat exchangers, tubular heat exchangers, finned heat exchangers, condensers, evaporators, boilers, or combinations thereof.

[0014] In one or more embodiments, the mixed feed stream 100 may contain at least 70% by weight of C2 to C4 hydrocarbons. For example, the mixed feed stream 100 may contain at least 70%, 75%, 80%, 85%, 90%, or 95% by weight of C2 to C4 hydrocarbons. In one or more embodiments, the C2 to C4 hydrocarbons may contain olefins and alkanes, including but not limited to ethane, ethylene, propane, propylene, butane, and butene. In one or more embodiments, the mixed feed stream 100 may also contain one or more of nitrogen, hydrogen, methane, carbon monoxide, and carbon dioxide. In some embodiments, the mixed feed stream may contain 0.1% to 15% by weight of N2, 0.01% to 10% by weight of H2, 0.01% to 10% by weight of methane, and 70% to 99% by weight of one or more of a C2 component, a C3 component, or a C4 component.

[0015] In one or more embodiments, the mixing feed stream 100 may have a temperature from 10°C to 75°C. For example, the mixing feed stream 100 may have temperatures of 10°C to 75°C, 20°C to 75°C, 30°C to 75°C, 40°C to 75°C, 50°C to 75°C, 60°C to 75°C, 70°C to 75°C, 10°C to 65°C, 10°C to 55°C, 10°C to 45°C, 10°C to 35°C, 10°C to 25°C, 10°C to 20°C, 10°C to 15°C, or any range or combination of these endpoints. In one or more embodiments, the mixing feed stream may have a pressure from 250 psig to 500 psig. For example, the mixed feed stream 100 may have pressures of 250 psig to 500 psig, 300 psig to 500 psig, 350 psig to 500 psig, 400 psig to 500 psig, 450 psig to 500 psig, 250 psig to 450 psig, 250 psig to 400 psig, 250 psig to 350 psig, 250 psig to 300 psig, or any range or combination of 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 the first liquid stream 106 in a separator 300. The separator 300 may be any suitable separator.

[0017] As used in this disclosure, a "separator" means any separation device or system of separation devices that at least partially separates one or more chemicals mixed in a process stream from each other. For example, a separator may selectively separate different chemical substances or phases from each other to form one or more chemical fractions. Examples of separators include, but are not limited to, distillation columns, flash evaporators, separation cylinders, separation tanks, traps, scrubbers, expansion devices, membranes, solvent extraction devices, etc. It should be understood that the separation methods described in this disclosure may not completely separate all of one chemical component from all of another chemical component. It should be understood that the separation methods described in this disclosure "at least partially" separate different chemical components from each other, and 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 components may be "separated" from a process stream to form a new process stream. Typically, a process stream may enter a separator and be split or separated into two or more process streams having the desired composition.

[0018] The first vapor stream 104 can be cooled to form a cooled stream 108. In some embodiments, the cooled stream 108 can be partially condensed, and in some embodiments, the cooled stream 108 can be completely condensed. In one or more embodiments, the first vapor stream 104 can be cooled in a first heat exchanger 200. In some embodiments, the first vapor stream 104 can be cooled in a heat exchanger located within a cold box 220.

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

[0020] Still referencing Figure 1 The cooled stream 108 can be separated into a second vapor stream 110 and a second liquid stream 112. The cooled stream 108 can be separated into the second vapor stream 110 and the second liquid stream 112 in a separator 302. The separator 302 can be any suitable separator. In one or more embodiments, the second liquid stream 112 may contain C2 hydrocarbons, C3 hydrocarbons, or C4 hydrocarbons, or combinations 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 the one or more heat exchangers. (Reference) Figure 1 In one or more embodiments, a second steam stream 110 may be passed from separator 302 to first heat exchanger 200 to provide cooling to first heat exchanger 200 and generate a warm second steam stream 120. In one or more embodiments, the warm second steam stream 120 may be expanded in expander 402 to generate expanded steam stream 122. Expanded steam stream 122 may be passed to first heat exchanger 200 to provide cooling to first heat exchanger 200. In one or more embodiments, expanded steam stream 122 may be passed to second heat exchanger 202 to provide cooling to second heat exchanger 202. Figure 1In the depicted embodiment, 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 both the first and second heat exchangers 200. Stream 125 may exit the system as exhaust gas from the second heat exchanger 202 after being cooled in the second heat exchanger 202.

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

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

[0024] In one or more embodiments, the first coolant stream 116 may have a temperature of -150°C to -30°C. For example, the first coolant stream 116 may have temperatures of -150°C to -30°C, -130°C to -30°C, -110°C to -30°C, -90°C to -30°C, -70°C to -30°C, -50°C to -30°C, -150°C to -50°C, -150°C to -70°C, -150°C to -90°C, -150°C to -110°C, -150°C to -130°C, or any range or combination of these endpoints. In one or more embodiments, the 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 flow 116 may have a pressure of 0 psig to 100 psig. For example, the first coolant flow 116 may have a pressure of 0 psig to 100 psig, 20 psig to 100 psig, 40 psig to 100 psig, 60 psig to 100 psig, 80 psig to 100 psig, 0 psig to 90 psig, 0 psig to 70 psig, 0 psig to 50 psig, 0 psig to 30 psig, 0 psig to 10 psig, or any range or combination of these endpoints.

[0025] A first coolant stream 116 may be passed through a first heat exchanger 200 to provide cooling to the first heat exchanger 200 and form a first warm 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 warm stream 124. In one or more embodiments, at least a portion of the first coolant stream 116 may evaporate in the first heat exchanger. In one or more embodiments, at least 80% by weight of the first warm stream 124 may be vapor. For example, at least 80%, 85%, 90%, 95%, or even 99% by weight of the first warm stream 124 may be vapor. In some embodiments, the first warm stream 124 may be completely evaporated.

[0026] In one or more embodiments, a second portion of the second liquid flow 118 may be passed to the fractionation system 304. The second portion of the second liquid flow 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 flow 118 through one or more heat exchangers can warm the second portion of the second liquid flow 118 and can provide cooling to the one or more heat exchangers. In some embodiments, the second portion of the second liquid flow 118 may be passed through a first heat exchanger 200 to provide cooling to the first heat exchanger 200. In some embodiments, the second liquid flow 118 may be passed through a second heat exchanger 202 to provide cooling to the second heat exchanger 202. In some embodiments, such as Figure 1 As depicted, a second portion of the second liquid flow 118 may be passed through the first heat exchanger 200 and subsequently 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 herein, a "fractionation system" refers to any fractionating device or system that, during a phase transition, at least partially divides a mixture (gas, solid, liquid, or a combination thereof) into a number of smaller fractions whose composition varies according to a gradient. In one or more embodiments, fractionation system 304 may be a multi-stage fractionation system. In such embodiments, fractionation system 304 may include multiple fractionating devices connected in series. For example, fractionation system 304 may include multiple separators and may include reflux or recirculation flows between the separators.

[0028] In one or more embodiments, a second portion of the second liquid stream 118 may be separated into a light fraction 126, a recirculation stream 128, and a heavy fraction 131. In one or more embodiments, the light fraction 126 may contain C2 hydrocarbons. For example, the light fraction 126 may contain at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or even at least 90 wt% of C2 hydrocarbons. In one or more embodiments, the recirculation stream 128 may contain one or more of C2 and C3 hydrocarbons. For example, the recirculation stream 128 may contain at least 50 wt%, at least 60 wt%, at least 70 wt%, at least 80 wt%, or even at least 90 wt% of C2 and C3 hydrocarbons. In one or more embodiments, the heavy fraction 131 may contain C2 hydrocarbons. 3+ Hydrocarbons. For example, heavy fraction 131 may contain 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% C. 3+ Hydrocarbons. In one or more embodiments, heavy fraction 131 can be transferred from the system to the C3 separation system.

[0029] In one or more embodiments, the light component 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 component 126 may leave the system. In some embodiments, such as Figure 1 As depicted, the pressure of light fraction 126 can be reduced to cool light fraction 126 and form cooled light fraction 127. The pressure of light fraction 126 can be reduced by passing light fraction 126 through valve 504. In such embodiments, cooled light fraction 127 can be passed to second heat exchanger 202 to provide cooling to second heat exchanger 202. Cooled light fraction 127 can be warmed in second heat exchanger 202 and can leave the system through flow 129.

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

[0031] Still referencing Figure 1 The pressure of the recirculation flow 128 can be reduced to at least partially evaporate the recirculation flow 128 to form the second coolant flow 130. In one or more embodiments, the pressure of the recirculation flow 128 can be reduced by passing the recirculation flow 128 through valve 502.

[0032] In one or more embodiments, the recirculation flow 128 may have a pressure of 200 psig to 450 psig. For example, the recirculation flow 128 may have pressures of 200 psig to 450 psig, 225 psig to 450 psig, 250 psig to 450 psig, 275 psig to 450 psig, 300 psig to 450 psig, 325 psig to 450 psig, 350 psig to 450 psig, 375 psig to 450 psig, 400 psig to 450 psig, or 425 psig to 450 psig. Pressures ranging from 1.1 psig to 425 psig, 200 psig to 400 psig, 200 psig to 375 psig, 200 psig to 350 psig, 200 psig to 325 psig, 200 psig to 300 psig, 200 psig to 275 psig, 200 psig to 250 psig, 200 psig to 225 psig, or any range or combination of these endpoints. In one or more embodiments, the circulating flow 128 may have a temperature ranging from -120°C to 100°C. For example, the recirculation flow 128 may have temperatures ranging from -120°C to 100°C, -100°C to 100°C, -80°C to 100°C, -60°C to 100°C, -40°C to 100°C, -20°C to 100°C, 0°C to 100°C, 20°C to 100°C, 40°C to 100°C, 60°C to 100°C, 80°C to 100°C, -120°C to 90°C, -120°C to 70°C, -120°C to 50°C, -120°C to 30°C, -120°C to 10°C, -120°C to -10°C, -120°C to -30°C, -120°C to -50°C, -120°C to -70°C, -120°C to -90°C, -120°C to -110°C, or any range or combination of these endpoints.

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

[0034] Still referencing Figure 1 The second coolant stream 130 may be passed through the first heat exchanger 200 to provide cooling to the first heat exchanger 200 and form a second warm 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 warm stream 132. In one or more embodiments, at least a portion of the second coolant stream 130 may evaporate in the first heat exchanger 200. In one or more embodiments, at least 80% by weight of the second warm stream 132 may be vapor. For example, at least 80%, 85%, 90%, 95%, or even 99% by weight of the second warm stream 132 may be vapor. In some embodiments, the second warm stream 132 may be completely evaporated.

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

[0036] Although not intended to be bound by theory, combining the first warm flow 124 and the second warm flow 132 can prevent temperature pinch-ups in the second heat exchanger 202. As used herein, a “temperature pinch-up” refers to a point in the heat exchanger where the temperature difference between the hot and cold fluids is zero or near zero. If a temperature pinch-up occurs, cooling in the heat exchanger may be insufficient. Although not intended to be bound by theory, the first coolant flow 116 supplies a cooling load to the cold box 220, thereby generating the first warm flow 124. Mixing the first warm flow 124 and the second warm flow 132 produces a third coolant flow 134 with a different composition and a lower boiling point relative to the first warm flow 124. This can improve the performance of the third coolant flow 134 as a coolant in the second heat exchanger 202 compared to the performance of the first warm flow 124 and the second warm flow 132 used alone as coolants. By avoiding temperature pinch points in the second heat exchanger 202, this allows the third coolant flow 134 to provide sufficient cooling to the second heat exchanger 202.

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

[0038] In some of the implementation schemes described herein, and as such Figure 1 As depicted, the first heat exchanger 200 and the second heat exchanger 202 may each be positioned within the cold box 220. In one or more embodiments not depicted, the first heat exchanger and the second heat exchanger may be positioned within separate cold boxes based on the system's cooling requirements.

[0039] Example

[0040] Various embodiments of the methods and systems for separating mixed feed streams will be further illustrated in the following examples. These examples are illustrative in nature and should not be construed as limiting the subject matter of this disclosure.

[0041] Example 1

[0042] for Figure 1 The recycling system described herein is illustrated in Example 1, using the integrated separation series process model in Aspen Plus. Table 1 shows... Figure 1The temperature, pressure, and mass fraction ratio of the described flow are shown in Table 1. The flow numbers included in Table 1 are... Figure 1 The numbering of the midstream is consistent with the numbering used throughout the detailed description.

[0043] Table 1 .

[0044]

[0045] Table 1, continued

[0046]

[0047] Table 1, continued

[0048]

[0049] As shown in Example 1, the mixed feed stream 100 can be separated into several hydrocarbon-containing streams, and those streams can be used for cooling in one or more heat exchangers. It should be noted that this is not... Figure 1 Each stream marked in the table and described above is listed in Table 1.

[0050] It should be noted that one or more of the appended claims use the term "wherein" as a transitional expression. For the purpose of defining this technology, it should be noted that this term is introduced in the claims as an open transitional phrase used to introduce a description of a series of features of the structure, and should be interpreted in a similar manner to the more commonly used open prepositional term "comprising".

[0051] It should be understood that when the first component is described as "comprising" the second component, it is contemplated in some embodiments that the first component is "composed of" or "substantially composed of" the second component. Furthermore, the term "substantially composed of" is used in this disclosure to refer to a quantitative value that does not materially affect the essential and novel characteristics of this disclosure. For example, a chemical composition "substantially" composed of a particular chemical component or group of chemical components should be understood to mean that the composition contains at least about 99.5% of that particular chemical component or group of chemical components.

[0052] It should be understood that any two quantitative values ​​assigned to a characteristic can constitute a range of that characteristic, and all combinations of ranges formed by all said quantitative values ​​of a given characteristic are considered in this disclosure.

[0053] The subject matter of this disclosure has been described in detail and with 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 such component or feature is necessary for a particular embodiment or any other embodiment. Furthermore, it will be apparent to those skilled in the art that various modifications and changes can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter.

Claims

1. A method for separating a mixed feed stream, the method comprising: The mixed feed stream is cooled to form a cooled mixed feed stream, wherein the mixed feed stream contains one or more of C2 hydrocarbons, C3 hydrocarbons and C4 hydrocarbons; The cooled mixed feed stream is separated into a first vapor stream and a first liquid stream; The first vapor stream is cooled to form a cooled stream; The cooled flow is separated into a second vapor flow and a second liquid flow; The pressure of the first portion of the second liquid flow is reduced to at least partially evaporate the first portion of the second liquid flow and form a first coolant flow; Separate a second portion of the second liquid flow to form at least a light fraction, a recirculated flow, and a heavy fraction; The pressure of the recirculation flow is reduced to at least partially evaporate the recirculation flow to form a second coolant flow; The first coolant flow is passed through the first heat exchanger to provide cooling in the first heat exchanger and form a first warm flow; The second coolant flow is passed through the first heat exchanger to provide cooling in the first heat exchanger and form a second warm flow; The first warm flow and the second warm flow are combined to form a third coolant flow; as well as The third coolant flow is passed through the second heat exchanger to provide cooling in the second heat exchanger.

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

3. The method according to claim 1 or claim 2, wherein the second heat exchanger is positioned inside the cold box.

4. The method according to any one of claims 1 to 3, further comprising: Reduce the pressure of the light fraction to form a cooled light fraction; as well as The cooled light fraction is passed through the second heat exchanger to provide cooling in the second heat exchanger.

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

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

8. The method according to any one of claims 1 to 7, the method 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 recirculated stream and the heavy fraction.

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

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

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

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

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

14. The method according to any one of claims 1 to 13, wherein at least 80% by weight of the first warm stream is steam, and at least 80% by weight of the second warm stream is steam.

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

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