US-12623981-B2 - Integration of naphtha to ethane and propane fractionation section with ethane steam cracker

Abstract

A process of producing ethylene and propylene from naphtha, the process comprising: producing light paraffins—ethane, hydrogen/methane/residual ethane and propane rich streams—in a dividing wall fractionation column from a stream of hydrogen, methane, propane, and residual C4+ produced in the reactor section of a naphtha-to-ethane-and-propane processing unit by reacting naphtha with hydrogen, a naphtha reactor effluent stream produced by a naphtha reactor of the naphtha-to-ethane-and-propane processing unit is cooled to produce a feed stream. The feed stream is passed to a dividing wall fractionation column. An ethane stream from the dividing wall fractionation column is passed to an ethane steam cracker to produce a cracking heater effluent stream. The cracking heater effluent stream is passed to a coldbox of the ethane steam cracker after multiple steps such as quenching, compression, cooling, caustic scrubbing, drying. One or more fluids for cooling the naphtha (NEP) reactor effluent stream and for cooling the coldbox of the ethane steam cracker are provided by a common refrigeration system.

Inventors

• Sudipta K. Ghosh
• Xin X. Zhu
• Kyle Cuellar

Assignees

• UOP LLC

Dates

Publication Date

20260512

Application Date

20231114

Claims (19)

1. 1 . A process of producing ethylene and propylene from naphtha, the process comprising: reacting naphtha with hydrogen in a reactor section of a naphtha-to-ethane-and-propane (NEP) processing unit to produce a naphtha reactor effluent stream comprising hydrogen cooling methane, ethane, propane and C4+ hydrocarbons; cooling the naphtha reactor effluent stream to produce a feed stream; passing the feed stream to a dividing wall fractionation column to produce a top product stream comprising hydrogen, methane, and residual ethane, an ethane stream, and a propane stream; passing the ethane stream from the dividing wall fractionation column to a cracking heater section of an ethane steam cracker to produce a cracking heater effluent stream comprising ethylene; passing the propane stream to a propane de-hydrogenation unit to produce an effluent stream comprising propylene; and passing the cracking heater effluent stream to a coldbox of the ethane steam cracker; wherein one or more fluids for cooling the naphtha reactor effluent stream and for cooling the coldbox of the ethane steam cracker are provided by a common refrigeration system.
2. 2 . The process of claim 1 further comprising providing a separate coldbox in the naphtha-to-ethane-and-propane processing unit through which the naphtha reactor effluent stream passes during the cooling step.
3. 3 . The process of claim 2 wherein the one or more fluids for cooling the naphtha reactor effluent stream comprises two multiple levels of cascade refrigeration or mixed refrigeration.
4. 4 . The process of claim 3 further comprising passing the top product stream from the dividing wall fractionation column to the ethane steam cracker; and passing the top product stream through a condenser and the separate coldbox for exchanging heat prior to routing to the ethane steam cracker.
5. 5 . The process of claim 4 wherein the top product stream bypasses the cracking heater section of the ethane steam cracker and is passed to a cracked gas compressor section of the ethane steam cracker.
6. 6 . The process of claim 5 wherein the feed stream comprises hydrogen, methane, ethane, propane, and residual C4+ hydrocarbons.
7. 7 . The process of claim 6 further comprising passing the cracking heater effluent stream through a series of steps comprising quenching, compressing, cooling, caustic scrubbing, and drying prior to passing the cracking heater effluent stream to the coldbox of the ethane steam cracker.
8. 8 . The process of claim 7 wherein a hydrogen stream is separated due to the cooling in the coldbox and a methane stream is separated in a demethanizer and both streams are passed via the coldbox.
9. 9 . The process of claim 1 further comprising passing the naphtha reactor effluent through the coldbox to cool the naphtha reactor effluent.
10. 10 . The process of claim 9 further comprising passing the top product stream from the dividing wall fractionation column to the ethane steam cracker.
11. 11 . The method of claim 10 further comprising passing the top product stream through the coldbox prior to passing the top product stream to the ethane steam cracker.
12. 12 . The process of claim 11 further comprising passing the top product stream through a condenser prior to passing the top product stream to the coldbox and wherein the top product stream is passed to a cracked gas compressor section of the ethane steam cracker.
13. 13 . The process of claim 12 wherein the feed stream comprises hydrogen, methane, ethane, propane, and residual C4+ hydrocarbons.
14. 14 . A process of producing ethylene and propylene from naphtha, the process comprising: reacting naphtha with hydrogen in a reactor of a naphtha-to-ethane-and-propane (NEP) processing unit to produce a naphtha reactor effluent stream comprising hydrogen, methane, ethane, propane and C4+ hydrocarbons; cooling the naphtha reactor effluent stream to produce a feed stream; passing the feed stream to a dividing wall fractionation column to produce a top product stream comprising hydrogen, methane, and residual ethane, an ethane stream, and a propane stream; passing the top product stream from the dividing wall fractionation column to an ethane steam cracker to produce a cracking heater effluent stream comprising ethylene; and passing the propane stream to a propane de-hydrogenation unit to produce an effluent stream comprising propylene.
15. 15 . The process of claim 14 wherein the top product stream bypasses a cracking heater section of the ethane steam cracker and is passed to a cracked gas compressor section of the ethane steam cracker.
16. 16 . The process of claim 15 further comprising passing the top product stream through a coldbox prior to passing the top product stream to the ethane steam cracker and passing the top product stream through a condenser prior to passing the top product stream to the coldbox.
17. 17 . The process of claim 16 wherein the feed stream comprises hydrogen, methane, ethane, and propane and residual C4+ hydrocarbons.
18. 18 . The process of claim 17 further comprising passing the ethane stream from the dividing wall fractionation column to a cracking heater section of the ethane steam cracker to produce a cracking heater effluent stream; passing the cracking heater effluent stream through a series of steps comprising quenching, compressing, cooling, caustic scrubbing, and drying prior to passing the cracking heater effluent stream to a coldbox of the ethane steam cracker.
19. 19 . The process of claim 18 wherein a hydrogen stream is separated due to the cooling in the coldbox of the ethane steam cracker and a methane stream is separated in a demethanizer and both streams are passed via the coldbox of the ethane steam cracker.

Description

RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/431,558 filed on Dec. 9, 2022, the entirety of which is incorporated herein by reference. TECHNICAL FIELD This invention relates generally to separating ethane and propane from an effluent stream of a naphtha to ethane and propane reactor section; more particularly, the invention relates to separating streams rich in ethane, hydrogen/methane and propane from the effluent using a dividing wall fractionation column (DWC), optimized routing of ethane and hydrogen/methane streams to an ethane steam cracker to a most suitable location within the steam cracker. BACKGROUND Naphtha fed to a naphtha cracker produces olefins, namely ethylene and propylene. There is an industry trend towards shifting refining capacity to make increased petrochemicals due to the high value and market demand of ethylene and propylene compared to fuels. Naphtha steam cracking is the industry standard for making ethylene and propylene from naphtha, but ethylene plus propylene yields are low—less than 60% and typically less than 50% by weight depending on naphtha composition. The naphtha-to-ethane-and-propane (NEP) unit is designed to preferentially produce ethane and propane from naphtha via reacting naphtha with hydrogen. Ethane fed to an ethane steam cracker (ESC) and propane fed to a propane dehydrogenation unit (PDH) produces higher quantities of olefins (ethylene and propylene) than what would be possible if naphtha is directly fed to a naphtha cracker to produce olefins. However the products of NEP contain light ends (hydrogen, methane) along with ethane and require refrigeration utilities for separation. Separation of these components is essential but energy intensive and require refrigeration—so that ethane, the preferred feed component can be fed to the ESC. The present invention is provided to solve the problems discussed above and other problems, and to provide advantages and aspects not provided by prior process and apparatuses of this type. A full discussion of the features and advantages of the present invention is deferred to the following detailed description, which proceeds with reference to the accompanying drawings. SUMMARY A process of producing ethylene and propylene from naphtha, the process comprising: a process of producing light paraffins from naphtha by processing the effluent stream of NEP reactor and comprising of hydrogen, methane, ethane, propane and residual C4+s. This stream is fed to a dividing wall fractionation column (DWC). An ethane stream is separated in the dividing wall fractionation column as a side-cut product. The other streams separated in the DWC is a top product of hydrogen, methane and residual ethane and a bottom product of propane and residual C4+ The ethane stream is passed to an ethane steam cracker to produce cracking heater effluent comprising ethylene, unreacted ethane, hydrogen, methane, and other components. The cracking heater effluent is passed through a series of steps of the ethane steam cracker, compressed in a compression train, caustic scrubbed, dried and cooled in a coldbox. In the coldbox, a hydrogen rich stream is separated and a methane rich stream is separated via demethanizer overhead. The demethanizer bottom stream is deethanized, processed in an acetylene convertor reactor (to convert the acetylenes) and routed to a C2 splitter. This stream comprises of ethylene and unreacted ethane stream. The ethane and ethylene are separated in the C2-splitter column to produce ethylene product and ethane is recycled back to the cracking heaters. The DWC top product comprising of hydrogen, methane and residual ethane is fed directly to the aforementioned compression train of the ESC where the components are separated along with similar components from the ESC cracking heater effluent. One or more fluids for cooling the feed stream comprising hydrogen, methane, ethane, and propane to the dividing wall fractionation column in a coldbox exchanger, for cooling a condenser of the dividing wall column fractionation column, and are provided by a common source of refrigeration fluid—used by the cold box and other cooling exchangers of the ethane steam cracker as well. Other features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings. BRIEF DESCRIPTION OF THE DRAWINGS One or more exemplary embodiments of the present invention will be described below in conjunction with the following drawing figures, in which: FIG. 1 is a schematic of a naphtha-to-ethane-and-propane processing unit with a separation section; FIG. 2 is a schematic of a separation section of a divided wall fractionation column; FIG. 3 is a schematic of a naphtha-to-ethane-and-propane processing unit in combination with an ethane steam cracker featuring separate coldbox heat exchangers in the naphtha-to-ethane-and-propane processing