EP-4739644-A1 - A PROCESS FOR SEPARATING AN OLEFIN STREAM FROM METHANE

Abstract

A process for separating an olefin stream from a methane stream is disclosed. The process comprises providing an olefin stream comprising C2 and/or C3 olefins. The olefin stream is cooled in a heat exchanger with a mixed refrigerant stream to provide a cooled olefin stream. The cooled olefin stream is passed to a demethanizer column operating at an overhead pressure of about 344 kPa gauge (50 psig) to about 2069 kPa gauge (300 psig). The cooled olefin stream is fractionated in the demethanizer column to provide a demethanizer column overhead vapor stream and a demethanizer column bottoms liquid stream. The process provides an improved recovery/yield of olefins and also optimizes the cooling and/or heating of other process streams.

Inventors

• HORN, IAN G.
• CHIN, Andrew B.
• BOEHM, ERNEST J.
• ERICKSON, Allen
• GHOSH, SUDIPTA

Assignees

• UOP LLC

Dates

Publication Date

20260513

Application Date

20240814

Claims (20)

1. 1. A process for separating an olefin stream from a methane stream comprising: providing an olefin stream comprising C2 and/or C3 olefins; cooling said olefin stream in a heat exchanger with a mixed refrigerant stream to provide a cooled olefin stream; passing the cooled olefin stream to a demethanizer column operating at an overhead pressure of about 344 kPa gauge (50 psig) to about 2069 kPa gauge (300 psig); and fractionating said cooled olefin stream in the demethanizer column to provide a demethanizer column overhead vapor stream and a demethanizer column bottoms liquid stream.
2. 2. The process of claim 1 wherein said olefin stream is separated into a vapor olefin stream and a liquid olefin stream which are passed to the demethanizer column separately.
3. 3. The process of claim 2 further comprises: passing said vapor olefin stream to the heat exchanger; cooling said vapor olefin stream in the heat exchanger to provide a cooled vapor olefin stream; separating said cooled vapor olefin stream to provide an overhead vapor olefin stream and a bottom liquid olefin stream; and fractionating said overhead vapor olefin, said bottom liquid olefin stream, and said liquid olefin stream in the demethanizer column.
4. 4. The process of claim 1 further comprising: taking a first side stream from the demethanizer column; passing said first side stream to the heat exchanger to provide a heat exchanged first side stream; and passing said heat exchanged first side stream to the demethanizer column.
5. 5. The process of claim 4 further comprising: passing said first side stream to a reflux compressor to provide a compressed first side stream; passing said compressed first side stream to the heat exchanger to provide a heat exchanged first side stream; passing said heat exchanged first side stream to the demethanizer column.
6. 6. The process of claim 5 further comprising: passing said heat exchanged first side stream to an overhead heat exchanger to provide a cooled reflux stream; expanding said cooled reflux stream to provide an expanded reflux stream; and passing said expanded reflux stream to the demethanizer column.
7. 7. The process of claim 1 further comprising: taking a second side stream from the demethanizer column; passing said second side stream to the heat exchanger to provide a heated second side stream; and passing said heated second side stream to the demethanizer column.
8. 8. The process of claim 1 further comprising: passing said demethanizer column bottoms liquid stream to the heat exchanger to provide a heat exchanged bottoms liquid stream; and passing said heat exchanged bottoms liquid stream to a deethanizer column.
9. 9. The process of claim 1 wherein said olefin stream comprising C2 and/or C3 olefins is produced from reacting oxygenates over a SAPO catalyst.
10. 10. The process of claim 1 further comprising passing said demethanizer column overhead vapor stream to the heat exchanger to heat exchange with said olefin stream and said refrigerant stream to provide a heat exchanged overhead vapor stream.
11. 11. The process of claim 1 further comprising passing said demethanizer column bottoms liquid stream to the heat exchanger to heat exchange with said olefin stream and said refrigerant stream to provide a heat exchanged bottoms liquid stream.
12. 12. The process of claim 1 further comprising: passing said mixed refrigerant stream to a refrigerant compressor to provide a compressed mixed refrigerant stream; passing said compressed mixed refrigerant stream to the heat exchanger to provide said cooled olefin stream and a cooled refrigerant stream; and passing said cooled refrigerant stream to the refrigerant compressor.
13. 13. The process of claim 12 further comprising: expanding said cooled refrigerant stream to provide an expanded refrigerant stream; passing said expanded refrigerant stream to the heat exchanger to provide a heat exchanged refrigerant stream; and passing said heat exchanged refrigerant stream to the refrigerant compressor.
14. 14. A process for separating an olefin stream from a methane stream comprising: providing an olefin stream comprising C2 and/or C3 olefins; cooling said olefin stream in a heat exchanger with a mixed refrigerant stream to provide a cooled olefin stream; passing an overhead vapor olefin stream taken from said cooled olefin stream and a liquid olefin stream taken from said cooled olefin stream to a demethanizer column operating at an overhead pressure of about 344 kPa gauge (50 psig) to about 2069 kPa gauge (300 psig); fractionating said overhead vapor olefin stream and said liquid olefin stream in the demethanizer column to provide a demethanizer column overhead vapor stream, a demethanizer column bottoms liquid stream, and a first side stream; and passing said demethanizer column overhead vapor stream, said demethanizer column bottoms liquid stream, and said first side stream to the heat exchanger to heat exchange with said olefin stream and said refrigerant stream and provide a heat exchanged overhead vapor stream, a heat exchanged bottoms liquid stream, and a heat exchanged first side stream.
15. 15. The process of claim 14 wherein said olefin stream is separated into a vapor olefin stream and a liquid olefin stream which are passed to the demethanizer column separately.
16. 16. The process of claim 15 further comprises: passing said vapor olefin stream to the heat exchanger; cooling said vapor olefin stream in the heat exchanger to provide a cooled vapor olefin stream; separating said cooled vapor olefin stream to provide said overhead vapor olefin stream and said bottom liquid olefin stream; and passing said overhead vapor olefin stream, said bottom liquid olefin stream, and said liquid olefin stream to the demethanizer column.
17. 17. The process of claim 14 further comprising: passing said first side stream to a reflux compressor to provide a compressed first side stream; passing said compressed first side stream to the heat exchanger; passing said heat exchanged first side stream to an overhead heat exchanger to provide a cooled reflux stream; and passing said cooled reflux stream to the demethanizer column.
18. 18. The process of claim 14 wherein the step of passing said demethanizer column bottoms liquid stream to the heat exchanger comprises: taking a second side stream and said demethanizer column bottoms liquid stream from the demethanizer column; passing said second side stream and said demethanizer column bottoms liquid stream to the heat exchanger to provide a heated side stream and a heat exchanged bottoms liquid stream; passing said heated side stream to the demethanizer column; and passing the heat exchanged bottoms liquid stream to a deethanizer column.
19. 19. The process of claim 18 wherein the deethanizer column is in downstream fluid communication with the demethanizer column.
20. 20. The process of claim 14 wherein said olefin stream comprising C2 and/or C3 olefins is produced from reacting oxygenates over a SAPO catalyst.

Description

A PROCESS FOR SEPARATING AN OLEFIN STREAM FROM METHANE FIELD [0001] The field is related to a process for separating an olefin stream from a methane stream. The field may particularly relate to a process for cooling an olefin stream with a mixed refrigerant. BACKGROUND [0002] There is an increasing support and demand across the globe for sustainable aviation fuels (SAF) with government offering subsidies and mandating the production of carbon- neutral jet fuel. In recent years, considerable research has been devoted in finding effective and efficient means of producing SAF. There are several different routes that can be taken to address the demand including the methanol-to-olefin route. [0003] Olefins have been traditionally produced from petroleum feedstock by catalytic or steam cracking processes. These cracking processes, especially steam cracking, produce light olefins such as ethylene and propylene from a variety of hydrocarbon feedstocks. Ethylene and propylene are important commodity petrochemicals useful in a variety of processes for making plastics and other chemical compounds. [0004] The petrochemical industry has known for some time that oxygenates, especially alcohols, are convertible into light olefins. For example, methanol, the preferred alcohol for light olefin production, may be converted to primarily ethylene and propylene in the presence of a molecular sieve catalyst. This process is referred to as a methanol-to-olefin (MTO) process, which occurs in an MTO reaction system. The highly efficient MTO process may convert oxygenates to light olefins which had been typically utilized in plastics production. Light olefins produced from the MTO process are concentrated in ethylene and propylene but includes C4-C6 olefins. [0005] Usually, an ethylene rich stream is separated from light olefins by employing a process which recovers the ethylene component in a desirable, ethylene rich stream by separating it from other components and impurities. For example, depending on the feedstock composition, the reaction conditions, and the extent of side reactions, an MTO effluent can contain other light olefins and diolefins, and light paraffins such as methane and ethane. Some processes for separation involve the use of flash stages and distillation at cryogenic temperatures. While some processes for separation involve separating and recovering ethylene at non-cryogenic temperatures. [0006] Cryogenic separation can be capital intensive due to both the capital cost of the specialized vessel metallurgy and refrigeration equipment, and the operating costs from compression and cooling. The compression and cooling may be provided by, for example, an ethylene refrigerant provided by an ethylene refrigeration compressor. On the other hand, the non-cryogenic temperatures may limit the extent of recovery of ethylene. [0007] The m ethanol -to-jet process produces a large intermediate stream of light olefins at low pressure. A light olefin recovery process (LORP) compresses this stream and removes contaminants before light olefins can be oligomerized into jet fuel. Refrigeration and compression consume substantial energy in the LORP. [0008] The need exists for improving recovery of olefins, reducing the equipment count, reducing the overall consumption of heat in the complex, and reducing overall emissions and operating costs. BRIEF SUMMARY [0009] We have formulated a process and apparatus for separating an olefin stream from a methane stream using a mixed refrigerant system which provides an alternative to cascade refrigeration for light olefin recovery. The process involves the use of a mixed refrigerant which has several components of varying molecular weight that can be tailored to the specific process circumstances and fit a distinct boiling and cooling curve. Also, the mixed refrigerant system includes an integrated heat exchanger for heat exchanging other process streams with the mixed refrigerant stream. BRIEF DESCRIPTION OF THE DRAWINGS [0010] The FIGURE is a schematic drawing of a process for separating an olefin stream from a methane stream in accordance with an exemplary embodiment of the present disclosure. DEFINITIONS [0011] The term “communication” means that fluid flow is operatively permitted between enumerated components, which may be characterized as “fluid communication”. [0012] The term “downstream communication” means that at least a portion of fluid flowing to the subject in downstream communication may operatively flow from the object with which it fluidly communicates. [0013] The term “upstream communication” means that at least a portion of the fluid flowing from the subject in upstream communication may operatively flow to the object with which it fluidly communicates. [0014] The term “direct communication” or “directly” means that fluid flow from the upstream component enters the downstream component without passing through any other intervening vessel. [0015] The term “column” means a