CN-121986244-A - 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 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 recycle stream, reducing the pressure of the recycle stream to form a second coolant stream, passing the first coolant stream through a first heat exchanger to form a first warm stream, passing the second coolant stream through a first heat exchanger to form a second warm stream, combining the first warm stream and the second warm stream to form a third coolant stream, and passing the third coolant stream through a second heat exchanger.

Inventors

• ZHANG YUE
• B. al SAR
• J. Holderness
• J. J. Dylan
• A. M. McNally
• M. T. Pratz
• A. thews
• KEITH JERRY
• M - A - Cogswell

Assignees

• 陶氏环球技术有限责任公司

Dates

Publication Date

20260505

Application Date

20240916

Priority Date

20230918

Claims (15)

1. 1. A method for separating a mixed feed stream, the method comprising: Cooling the mixed feed stream to form a cooled mixed feed stream, wherein the mixed feed stream comprises one or more of C 2 hydrocarbons, C 3 hydrocarbons, and C 4 hydrocarbons; separating the cooled mixed feed stream into a first vapor stream and a first liquid stream; said first vapor stream is cooled to form a cooled stream; said cooled stream is separated 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 vaporize the first portion of the second liquid stream and form a first coolant stream; Separating a second portion of the second liquid stream to form at least a light fraction, a recycle stream, and a heavy fraction; Reducing the pressure of the recycle stream to at least partially vaporize the recycle stream to form a second coolant stream; Passing the first coolant stream through a first heat exchanger to provide cooling in the first heat exchanger and form a first warmed stream; passing the second coolant stream through the first heat exchanger to provide cooling in the first heat exchanger and form a second warmed stream; combining the first warmed stream and the second warmed stream to form a third coolant stream, and The third coolant stream is passed through a second heat exchanger to provide cooling in the second heat exchanger.
2. 2. The method of claim 1, wherein the first heat exchanger is positioned within a cold box.
3. 3. The method of claim 1 or claim 2, wherein the second heat exchanger is positioned within a cold box.
4. 4. A method according to any one of claims 1 to 3, the method further comprising: reducing the pressure of the light fraction to form a cooled light fraction, and Passing the cooled light fraction through the second heat exchanger to provide cooling in the second heat exchanger.
5. 5. The method of any one of claims 1 to 4, further comprising passing the second vapor stream through one or more heat exchangers to provide cooling in the one or more heat exchangers.
6. 6. The method of any one of claims 1 to 5, wherein cooling the mixed feed stream occurs in the second heat exchanger.
7. 7. The method of any of claims 1-6, wherein cooling the first vapor stream occurs in the first heat exchanger.
8. 8. The method of any one of claims 1-7, further comprising passing the second portion of the second liquid stream through one or more heat exchangers prior to separating the second portion of the second liquid stream to form at least the light fraction, the recycle stream, and the heavy fraction.
9. 9. The method of any one of claims 1-8, wherein the mixed feed stream comprises at least 70 wt% of one or more of C 2 hydrocarbons, C 3 hydrocarbons, and C 4 hydrocarbons.
10. 10. The method of any one of claims 1 to 9, wherein the first portion of the second liquid stream has a temperature of-150 ℃ to 0 ℃ and a pressure of 200psig to 480 psig.
11. 11. The method of any one of claims 1 to 10, wherein the first coolant stream has a temperature of-150 ℃ to-30 ℃ and a pressure of 0psig to 100 psig.
12. 12. The process of any one of claims 1 to 11, wherein the recycle stream has a temperature of-120 ℃ to 100 ℃ and a pressure of 200psig to 450 psig.
13. 13. The method of any one of claims 1 to 12, wherein the second coolant stream has a temperature of-130 ℃ to 0 ℃ and a pressure of 5psig to 200 psig.
14. 14. The method of any one of claims 1 to 13, wherein at least 80 wt% of the first warmed stream is vapor and at least 80 wt% of the second warmed stream is vapor.
15. 15. The method of any one of claims 1-14, wherein the recycle stream comprises at least 50 wt% of one or more of C 2 hydrocarbons and C 3 hydrocarbons.

Description

Process for separating hydrocarbons Cross Reference to Related Applications The present application claims the benefit of U.S. provisional application serial No. 63/583,428, filed on 18, 9, 2023, the contents of which are incorporated herein in their entirety. Technical Field Embodiments described herein relate generally to methods and systems for separating hydrocarbons. Background Various hydrocarbons, such as ethylene, ethane, propylene, propane, and heavier hydrocarbons, may be recovered from the various product streams obtained from the chemical reactors. Cryogenic separation processes can be used to recover more condensable hydrocarbons from less condensable gases or products. Disclosure of Invention In cryogenic separation processes, the mixed feed stream may be cooled by heat exchange with other process streams and/or external refrigeration sources. As the mixed feed stream is cooled, the liquid stream comprising the various fractions of the mixed feed stream may be collected as a high pressure liquid stream. Some of these streams may undergo pressure drop and serve as coolant streams in the heat exchanger of the separation process. However, the use of these streams as coolant in multiple heat exchangers arranged in series in a separation process may result in temperature pinch points within one or more of the heat exchangers. As described in further detail herein, a "temperature pinch" may occur when the temperature difference between the hot and cold streams in the heat exchanger approaches zero. Thus, there is a need for an improved process for separating mixed feed streams wherein the process stream is used for cooling. Embodiments of the present disclosure may meet these needs. In accordance with one or more embodiments of the present 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 C 2 hydrocarbons, C 3 hydrocarbons, and C 4 hydrocarbons, separating the cooled mixed feed stream into a first vapor stream and a first liquid stream, cooling the first vapor stream to form a cooled stream, separating the cooled stream into a second vapor stream and a second liquid stream, reducing a pressure of a first portion of the second liquid stream to at least partially vaporize the first portion of the second liquid stream and form a first coolant stream, separating a second portion of the second liquid stream to form at least a light fraction, a recycle stream, and a heavy fraction, reducing a pressure of the recycle stream to at least partially vaporize the second coolant stream, passing the first coolant stream through a first heat exchanger to provide cooling in the first heat exchanger and form a first warm stream, passing the second coolant stream through the first heat exchanger to provide cooling in the first heat exchanger and passing the second coolant stream through the first heat exchanger to form a second heat exchanger, and passing the second portion of the second liquid stream through the second heat exchanger to form a third heat exchanger. 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. Drawings The following detailed description of certain 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: fig. 1 schematically depicts a system for separating hydrocarbons according to one or more embodiments disclosed herein. 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, but not limited to, temperature transmitters, pressure transmitters, flow meters, pumps, valves, etc. Such components are well known to be within the spirit and scope of the disclosed embodiments. However, operational components (such as those described in the present disclosure) may be added to the embodiments described in the present disclosure. Reference will now be made in detail to various embodiments, some of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. Detailed Description One or more non-limiting embodiments of a method for separating a mixed feedstream are described herein. As described herein, a method for separating hydrocarbons may include using multiple process streams as coolant in a heat exchanger. After using the process stream as a coolant in the first heat exchanger, the process stream