Methods for separating hydrocarbons

Abstract

A method for separating a mixed feed stream, which 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 the 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 recirculating stream; reducing the pressure of the recirculating stream to form a second coolant stream; passing the first coolant stream through a first heat exchanger to form a first heated stream; passing the second coolant stream through a first heat exchanger to form a second heated stream; combining the first heated stream and the second heated stream to form a third coolant stream; and passing the third coolant stream through a second heat exchanger.

Description

TECHNICAL FIELD

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Patent Application No. 63 / 583,428 filed on September 18, 2023, the entire content of which is incorporated herein by reference.

[0002] (FIELD OF THE INVENTION) Embodiments described herein relate generally to methods and systems for separating hydrocarbons.

BACKGROUND ART

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

SUMMARY OF THE INVENTION

[0004] In a cryogenic separation process, a 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, a liquid stream containing various fractions of the mixed feed stream can be collected as a high-pressure liquid stream. A portion of these streams can be subjected to reduced pressure and used as a refrigerant stream in the heat exchangers of the separation process. However, using these streams as refrigerants in multiple heat exchangers arranged in series in the separation process can result in temperature pinches in one or more of the heat exchangers. As described in further detail herein, a "temperature pinch" can occur when the temperature difference between the hot stream and the cold stream in a heat exchanger approaches zero. Accordingly, there is a need for an improved process for separating a mixed feed stream in which process streams are used for cooling. These needs can be met by the embodiments of the present disclosure.

[0005] According to one or more embodiments of the present disclosure, a method for separating a mixed feed stream includes: cooling a mixed feed stream containing one or more C2, C3, and C4 hydrocarbons 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; reducing the pressure of the 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; and forming at least a light fraction, a recirculating stream, and a heavy fraction. This may include separating a second portion of a second liquid flow, reducing the pressure of the recirculating flow so that the recirculating flow vaporizes at least partially in order to form a second coolant flow, passing the first coolant flow through the first heat exchanger to provide cooling in the first heat exchanger and form a first heated flow, passing the second coolant flow through the first heat exchanger to provide cooling in the first heat exchanger and form a second heated flow, combining the first heated flow and the second heated flow to form a third coolant flow, and passing the third coolant flow through the second heat exchanger to provide cooling in the second heat exchanger.

[0006] Additional features and advantages of the technology disclosed herein will be described in the subsequent detailed description and will be readily apparent to those skilled in the art from that description, or will be recognized by practicing the technology as described herein, including the subsequent detailed description, the claims, and the accompanying drawings. [Brief explanation of the drawing]

[0007] The following "Modes for Carrying Out the Invention" of specific embodiments of this disclosure can be best understood in conjunction with the following drawings, where similar structures are shown with similar reference numerals. [Figure 1] This is a schematic diagram of a system for separating hydrocarbons according to one or more embodiments disclosed herein.

[0008] It should be understood that the drawings are essentially schematic and do not, without limitation, include some components of isolation systems commonly used in the art, such as temperature transmitters, pressure transmitters, flow meters, pumps, and valves. These components will be known to be within the spirit and scope of the disclosed embodiments. However, operating components, such as those described herein, may be added to the embodiments described herein.

[0009] Herein, various embodiments are referred to in more detail, some of which are illustrated in the accompanying drawings. Wherever possible, the same reference numerals will be used throughout the drawings to refer to the same or similar parts. [Modes for carrying out the invention]

[0010] One or more non-limiting embodiments of a method for separating mixed feed streams are described herein. As described herein, a method for separating hydrocarbons may include using multiple process streams as coolants in a heat exchanger. After using process streams as coolants in a first heat exchanger, the process streams may be combined before being used as coolants in a second heat exchanger. Although not bound by theory, combining process streams before using them as coolants in a second heat exchanger can prevent a temperature pinch in the second heat exchanger. These advantages, as well as other advantages, are described in detail below.

[0011] Referring here to 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, the cooling of the mixed feed stream 100 can be carried out in a second heat exchanger 202. In one or more embodiments, at least a portion of the mixed feed stream 100 can be condensed by cooling the compressed mixed feed stream 100. In some embodiments, the mixed feed stream 100 may be cooled in a heat exchanger located in a cold box 220.

[0012] As used in this disclosure, “cold box” refers to an insulated enclosure capable of housing 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 located within the cold box. In some embodiments, multiple heat exchangers may be located in series within the cold box. The heat exchangers may include brazed heat exchangers, shell-and-tube heat exchangers, double-tube heat exchangers, plate heat exchangers, tubular heat exchangers, finned heat exchangers, condensers, evaporators, boilers, or combinations thereof.

[0013] In one or more embodiments, the mixed feed stream 100 may contain at least 70% by weight of C2-C4 hydrocarbons. For example, the mixed feed stream 100 may contain at least 70% by weight, 75% by weight, 80% by weight, 85% by weight, 90% by weight, or 95% by weight of C2-C4 hydrocarbons. In one or more embodiments, the C2-C4 hydrocarbons may include, but are not limited to, olefins and paraffins, including ethane, ethylene, propane, propylene, butane, and butene. In one or more embodiments, the mixed feed stream 100 may further 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 the C2, C3, or C4 components.

[0014] In one or more embodiments, the mixed feed stream 100 may have a temperature of 10°C to 75°C. For example, the mixed 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 ranges formed from these endpoints. In one or more embodiments, the mixed feed stream may have a pressure of 250 psig to 500 psig. For example, the mixed feed flow 100 may have pressures in the ranges 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 ranges formed from these endpoints.

[0015] 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 can be separated into the first vapor stream 104 and the first liquid stream 106 within a separator 300. The separator 300 may be any suitable separator.

[0016] As used in this disclosure, “separator” means any separation device or system of separation devices that separates one or more chemical substances mixed in a process stream at least partially from one another. For example, a separator may selectively separate different chemical species or phases from one another to form one or more chemical fractions. Examples of separators include, but are not limited to, distillation columns, flash drums, knockout drums, knockout pots, traps, scrubbers, expansion devices, membranes, and solvent extractors. It should be understood that the separation processes described in this disclosure do not necessarily have to completely separate all of one chemical component from all of another. It should be understood that the separation processes described in this disclosure separate different chemical components “at least partially” from one another, and that separation may include only partial separation, even if not expressly stated. As used in this disclosure, one or more chemical components 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 a desired composition.

[0017] The first vapor flow 104 can be cooled to form a cooled flow 108. In some embodiments, the cooled flow 108 may be partially condensed, and in some embodiments, the cooled flow 108 may be completely condensed. In one or more embodiments, the first vapor flow 104 may be cooled within a first heat exchanger 200. In some embodiments, the first vapor flow 104 may be cooled within a heat exchanger located within a cold box 220.

[0018] In one or more embodiments, the cooled flow 108 may have a temperature of -150°C to 0°C. For example, the cooled 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 ranges formed from these endpoints.

[0019] Still referring to Figure 1, the cooled flow 108 may be separated into a second vapor flow 110 and a second liquid flow 112. The cooled flow 108 can be separated into a second vapor flow 110 and a second liquid flow 112 within a separator 302. The separator 302 may be any suitable separator. In one or more embodiments, the second liquid flow 112 may contain C2, C3, or C4 hydrocarbons or combinations thereof.

[0020] In one or more embodiments, the second vapor flow 110 may contain one or more of hydrogen, nitrogen, methane, carbon monoxide, and carbon dioxide. The second vapor flow may pass through one or more heat exchangers to provide cooling within one or more heat exchangers. Referring to Figure 1, in one or more embodiments, the second vapor flow 110 may be sent from the separator 302 to the first heat exchanger 200 to provide cooling to the first heat exchanger 200 and generate a heated second vapor flow 120. In one or more embodiments, the heated second vapor flow 120 may be expanded in the expander 402 to form an expanded vapor flow 122. The expanded vapor flow 122 can be sent to the first heat exchanger 200 to provide cooling to the first heat exchanger 200. In one or more embodiments, the expanded vapor flow 122 can be sent to the second heat exchanger 202 to provide cooling to the second heat exchanger 202. In the embodiment shown in Figure 1, the expanding vapor flow 122 can be sent to the first heat exchanger 200 to form a flow 123, which can then be sent to the second heat exchanger 202 to provide cooling to both the first heat exchanger 200 and the second heat exchanger 202. After being used for cooling in the second heat exchanger 202, the flow 125 can exit the system from the second heat exchanger 202 as an off-gas.

[0021] In one or more embodiments, the pressure of the first portion 114 of the second liquid flow may be reduced to at least partially vaporize the first portion 114 of the second liquid flow and form the first coolant flow 116. In one or more embodiments, the pressure of the first portion 114 of the second liquid flow can be reduced by passing the first portion 114 of the second liquid flow through the valve 500.

[0022] In one or more embodiments, the first portion 114 of the second liquid flow may have a pressure of 200 psig to 480 psig. For example, the first portion 114 of the second liquid flow may have pressures 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, 450 psig to 480 psig, and 20 The pressure may be in the range of 0 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 ranges formed from these endpoints. In one or more embodiments, the first portion 114 of the second fluid flow may have a temperature of -150°C to 0°C. For example, the first portion 114 of the second fluid flow may have temperatures in the following ranges: -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 ranges formed from these endpoints.

[0023] 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 a temperature 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 ranges formed from these endpoints. In one or more embodiments, the temperature difference between the first portion 114 of the second liquid stream and the first coolant stream 116 may be 15°C, 10°C, 5°C, or even 1°C or less. In some embodiments, the first portion 114 of the second liquid stream 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 of 0 psig to 100 psig. For example, the first coolant stream 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 ranges formed from these endpoints.

[0024] The first coolant stream 116 can pass through the first heat exchanger 200 to provide cooling within 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 pass 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% by weight 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 completely vaporized.

[0025] In one or more embodiments, the second portion 118 of the second liquid stream may be sent to the fractionation system 304. The second portion 118 of the second liquid stream may pass through one or more heat exchangers before being sent to the fractionation system 304. By passing the second portion 118 of the second liquid stream through the one or more heat exchangers, the second portion of the second liquid stream 118 can be heated, and cooling can be provided to the one or more heat exchangers. In some embodiments, the second portion 118 of the second liquid stream can pass through the first heat exchanger 200 to provide cooling to the first heat exchanger 200. In some embodiments, the second liquid stream 118 can pass through the second heat exchanger 202 to provide cooling to the second heat exchanger 202. In some embodiments, as shown in Figure 1, the second portion 118 of the second liquid stream can pass through the first heat exchanger 200 and then through the second heat exchanger 202 to provide cooling to both the first heat exchanger 200 and the second heat exchanger 202 before being sent to the fractionation system 304.

[0026] As used in the present disclosure, "fractionation system" refers to any fractionation device or system of fractionation devices that at least partially divides a quantity of a mixture (gas, solid, liquid, or a combination thereof) into several smaller fractions whose composition varies according to a gradient during a phase transition. In one or more embodiments, the fractionation system 304 can be a multi-stage fractionation system. In such embodiments, the fractionation system 304 may comprise a plurality of fractionation devices in series. For example, the fractionation system 304 may comprise a plurality of separators, and may include reflux or recycle streams between the separators.

[0027] In one or more embodiments, the second portion 118 of the second liquid flow may be separated into a light fraction 126, a recirculated flow 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% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, or even at least 90% by weight of C2 hydrocarbons. In one or more embodiments, the recirculated flow 128 may contain one or more C2 and C3 hydrocarbons. For example, the recirculated flow 128 may contain at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, or even at least 90% by weight of one or more C2 and C3 hydrocarbons. In one or more embodiments, the heavy fraction 131 is C 3+ It may contain hydrocarbons. For example, heavy fraction 131 may contain at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or even at least 95% by weight of C 3+ It may contain hydrocarbons. In one or more embodiments, the heavy fraction 131 may be sent from the system to a C3 separation system.

[0028] In one or more embodiments, the light fraction 126 may be sent to a 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 can exit the system. In some embodiments, as shown in Figure 1, the pressure of the light fraction 126 can be reduced to cool the light fraction 126 and form cooled light fraction 127. The pressure of the light fraction 126 can be reduced by passing the light fraction 126 through a valve 504. In such embodiments, the cooled light fraction 127 can be sent to a second heat exchanger 202 to provide cooling to the second heat exchanger 202. The cooled light fraction 127 may be heated within the second heat exchanger 202 and exit the system through flow 129.

[0029] In one or more embodiments, the first liquid stream 106 may also be sent to the fractional distillation system 304. In some embodiments, the first liquid stream 106 may be sent from the separator 300 to the fractional distillation system 304. In some embodiments, as shown in Figure 1, the first liquid stream 106 may be combined with a second portion 118 of the second liquid stream upstream of the fractional distillation system 304 to form a fractionator feed stream 119. In embodiments in which the first liquid stream 106 is sent to the fractional distillation system 304, the first liquid stream 106 and the second portion 118 of the second liquid stream may be separated into a light fraction 126, a recirculation stream 128, and a heavy fraction 131.

[0030] Still referring to Figure 1, the pressure of the recirculating flow 128 can be reduced to form a second coolant flow 130, thereby at least partially vaporizing the recirculating flow 128. In one or more embodiments, the pressure of the recirculating flow 128 can be reduced by passing the recirculating flow 128 through the valve 502.

[0031] In one or more embodiments, the recirculating flow 128 may have a pressure of 200 psig to 450 psig. For example, the recirculating 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, 425 psig to 450 psig, and 200 psi. The pressures may be in the range of g~425 psig, 200 psig~400 psig, 200 psig~375 psig, 200 psig~350 psig, 200 psig~325 psig, 200 psig~300 psig, 200 psig~275 psig, 200 psig~250 psig, 200 psig~225 psig, or any range or combination of ranges formed from these endpoints. In one or more embodiments, the recirculating flow 128 may have a temperature of -120°C to 100°C. For example, the recirculation flow 128 is as follows: -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. The temperature range may be -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 ranges formed from these endpoints.

[0032] 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 a pressure 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 ranges formed from 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 flow 130 may have a temperature of -130°C to 0°C. For example, the second coolant flow 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 ranges formed from these endpoints.

[0033] Still referring to Figure 1, the second coolant flow 130 can pass through the first heat exchanger 200 to provide cooling within the first heat exchanger 200 and form a second heated flow 132. Note that in some embodiments, the second coolant flow 130 may pass through one or more heat exchangers to form a second heated flow 132. In one or more embodiments, at least a portion of the second coolant flow 130 may be vaporized within the first heat exchanger 200. In one or more embodiments, at least 80% by weight of the second heated flow 132 may be steam. For example, at least 80%, 85%, 90%, 95%, or even 99% by weight of the second heated flow 132 may be steam. In some embodiments, the second heated flow 132 may be completely vaporized.

[0034] In one or more embodiments, a first heated flow 124 and a second heated flow 132 may be combined to form a third coolant flow 134. In one or more embodiments, the first heated flow 124 and the second heated flow 132 may have substantially the same temperature and pressure when they are combined to form the third coolant flow 134.

[0035] While not bound by theory, combining the first heated flow 124 and the second heated flow 132 can prevent a temperature pinch in the second heat exchanger 202. As used in this application, “temperature pinch” refers to a point in the heat exchanger where the temperature difference between the hot and cold fluids is zero or close to zero. When a temperature pinch occurs, cooling in the heat exchanger may be insufficient. While not bound by theory, the first coolant flow 116 provides cooling capacity to the cold box 220 and results in the first heated flow 124. Mixing the first heated flow 124 and the second heated flow 132 can result in a third coolant flow 134 having a different composition and a lower boiling point compared to the first heated flow 124. This improves the performance of the third coolant flow 134 as a coolant in the second heat exchanger 202 compared to the performance of the first heated flow 124 and the second heated flow 132 used individually as coolants in the second heat exchanger 202. As a result, the third coolant flow 134 can provide sufficient cooling to the second heat exchanger 202 by avoiding a temperature pinch in the second heat exchanger 202.

[0036] The third coolant flow 134 can pass through the second heat exchanger 202 to provide cooling to the second heat exchanger 202. In some embodiments, the third coolant flow 134 may be heated within the second heat exchanger 202 to produce a heated flow 136. In one or more embodiments, the heated flow may exit the cold box 220. In some embodiments, the heated flow may pass through one or more heat exchangers to provide cooling within the heat exchangers.

[0037] In some embodiments described herein, the first heat exchanger 200 and the second heat exchanger 202 may be located within a cold box 220, as shown in Figure 1. In one or more embodiments not shown, the first and second heat exchangers may be located within separate cold boxes, based on the cooling requirements of the system. [Examples]

[0038] Various embodiments of processes and systems for separating mixed feedstreams are further illustrated in the following examples. These embodiments should be understood as being illustrative in nature and not limiting the subject matter of this application.

[0039] Example 1 Example 1 was carried out using the integrated separation train process model in Aspen Plus for the recovery system shown in Figure 1. Table 1 shows the temperature, pressure, and mass fraction ratio of the flow shown in Figure 1. The flow numbering in Table 1 corresponds to the flow numbering in Figure 1 and the numbering used throughout the detailed description.

[0040] [Table 1]

[0041] [Table 2]

[0042] [Table 3]

[0043] As shown in Example 1, the mixed feed stream 100 may be separated into several hydrocarbon-containing streams, which may be used for cooling in one or more heat exchangers. Note that not all of the streams shown in Figure 1 and described above are listed in Table 1.

[0044] Note that one or more of the following claims utilize the term “wherein” as a transitional clause. Note that, for the purpose of defining the art, this term is introduced into the claims as an unrestricted transitional clause used to introduce an enumeration of a set of structural features, and should be interpreted similarly to the more commonly used unrestricted preamble term “comprising.”

[0045] Where a first component is described as "comprising" a second component, it should be understood that in some embodiments, the first component is intended to "consist" or "consist essentially of" its second component. Additionally, the term "consist essentially of" is used in this disclosure to refer to a quantitative value that does not substantially affect the basic and novel features of this disclosure. For example, a chemical composition "consisting essentially 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.

[0046] Any two quantitative values ​​assigned to a characteristic may constitute a range for that characteristic, and it should be understood that all combinations of ranges formed from all described quantitative values ​​of a given characteristic are contemplated in this disclosure.

[0047] The subject matter of this disclosure is described in detail with reference to specific embodiments. Any detailed description of the components or features of the embodiments should be understood not to mean that such components or features are essential to the specific 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 mixed feed streams, In order to form a cooled mixed feed stream, the mixed feed stream is C ２ , C ３ , and C ４ Cooling the mixed feed stream containing one or more hydrocarbons, The cooled mixed feed stream is separated into a first vapor stream and a first liquid stream, To form a cooled flow, the first vapor flow is cooled, The cooled flow is separated into a second vapor flow and a second liquid flow, To at least partially vaporize the first portion of the second liquid flow and form a first coolant flow, the pressure of the first portion of the second liquid flow is reduced, To separate the second portion of the second liquid flow in order to form at least a light fraction, a recirculating flow, and a heavy fraction, In order to form a second coolant flow, the pressure of the recirculating flow is reduced so that the recirculating flow is at least partially vaporized, To provide cooling within the first heat exchanger and to form a first heated flow, the first coolant flow is passed through the first heat exchanger, The second coolant flow is passed through the first heat exchanger to provide cooling within the first heat exchanger and to form a second heated flow, In order to form a third coolant flow, the first heated flow and the second heated flow are combined, A method comprising passing the third coolant flow through the second heat exchanger in order to provide cooling within the second heat exchanger.

2. The method according to claim 1, wherein the first heat exchanger is located inside a cold box.

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

4. To form a cooled light fraction, the pressure of the light fraction is reduced, The method according to any one of claims 1 to 3, further comprising passing the cooled light fraction through the second heat exchanger in order 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 steam flow through one or more heat exchangers in order to provide cooling in the one or more heat exchangers.

6. The method according to any one of claims 1 to 5, wherein the cooling of the mixed feed flow is performed in the second heat exchanger.

7. The method according to any one of claims 1 to 6, wherein the cooling of the first steam flow is performed in the first heat exchanger.

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

9. The aforementioned mixed feed stream contains at least 70% by weight of C ２ , C ３ , and C ４ The method according to any one of claims 1 to 8, comprising one or more 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 flow 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 recirculating 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 flow 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 heated flow is steam, and at least 80% by weight of the second heated flow is steam.

15. The aforementioned recirculating flow contains at least 50% by weight of C ２ and C ３ The method according to any one of claims 1 to 14, comprising one or more hydrocarbons.

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