US-12623980-B2 - Separation of hydrogen, methane, ethane, and propane in naphtha to ethane and propane fractionation section based on a dividing wall fractionation column integration

US12623980B2US 12623980 B2US12623980 B2US 12623980B2US-12623980-B2

Abstract

In a process of producing ethylene and propylene from naphtha the process a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor is fed to a dividing wall fractionation column.

Inventors

Sudipta K. Ghosh
Xin X. Zhu
Kyle Cuellar

Assignees

UOP LLC

Dates

Publication Date: 20260512
Application Date: 20231114

Claims (12)

1 . A process of producing ethylene and propylene from naphtha, the process comprising: passing a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor to a dividing wall fractionation column, wherein a top product stream is outputted by the dividing wall fractionation column, the top product stream comprising hydrogen, methane, and some slipped ethane (residual), a side product comprises an ethane rich stream, and a bottom product stream comprises propane and other heavy products, and passing a top product stream to a cracked gas compressor system of an ethane steam cracker, bypassing a cracking heater section of the ethane steam cracker.
2 . The process of claim 1 further comprising controlling an overhead temperature of the dividing wall column and refrigeration energy requirements by controlling an amount of the slipped ethane allowed in the top stream product of the dividing wall column.
3 . The process of claim 1 further comprising passing the ethane rich stream from the dividing wall fractionation column to an ethane steam cracker after heat exchange in a plurality of coldbox exchangers with a warm feed stream and thereby reducing a refrigeration requirement for feed cooling.
4 . The process of claim 3 further comprising passing the ethane rich stream to a cracking heater section of the ethane steam cracker, wherein an ethylene stream is output from the ethane steam cracker.
5 . The process of claim 4 wherein the ethane rich stream is a vapor side product of the dividing wall fractionation column, and wherein withdrawing the ethane rich stream as a vapor side product from the dividing wall fractionation column lowers a refrigeration requirement for the dividing wall fractionation column and reduces energy for vaporization in the ethane steam cracker.
6 . The process of claim 5 wherein the energy for vaporization in the ethane rich steam cracker is eliminated by the vapor side product and wherein a further energy reduction takes place by utilizing the ethane rich stream and the top product to cool fluids passing through the plurality of coldbox exchangers.
7 . The process of claim 1 further comprising passing the propane rich stream from the dividing wall fractionation column to a propane dehydrogenation unit after further fractionation in a depropanizer column.
8 . The process of claim 1 further comprising: passing the top product stream outputted by the dividing wall fractionation column to a cracked gas compressor of an ethane steam cracker; passing the ethane rich stream outputted by the dividing wall fractionation column to the ethane stream cracker, wherein an ethylene stream is output from the ethane steam cracker; and passing the propane rich stream outputted by the dividing wall fractionation column and after fractionation in a depropanizer to a propane dehydrogenation unit, wherein a propylene stream is output from the propane dehydrogenation unit, wherein the top product stream bypasses a cracking heater section of the ethane steam cracker, and thereby reducing a feed flow to the cracking heater section of hydrogen and methane which do not contribute to production of ethylene in the cracking heaters, and wherein a chilling section and cold fractionation section of the ethane steam cracker is configured to recover hydrogen and methane as well as ethane in a C2 splitter.
9 . The process of claim 1 further comprising passing the feed stream through at least one coldbox prior to passing the feed stream to the dividing wall fractionation column and thereby reducing a refrigeration requirement for cooling the feed stream to the dividing wall fractionation column.
10 . An apparatus for producing ethylene and propylene from naphtha comprising: an effluent from a naphtha-to-ethane-and-propane processing unit which separates an ethane rich stream and a propane rich stream from a stream comprising ethane, propane, hydrogen, methane, and residual C4+ heavy hydrocarbons, the naphtha-to-ethane-and-propane processing unit comprising: a dividing wall fractionation column which receives the effluent stream from an naphtha-to-ethane-and-propane reactor and outputs a top product stream comprising hydrogen and methane, the ethane rich stream as a side product, and the propane rich stream comprising residual C4+ hydrocarbons as a bottom product, an ethane steam cracker configured to input the ethane rich stream from the dividing wall fractionation column and output a stream of ethylene, wherein the ethane rich stream is a vapor side product of the dividing wall fractionation column, wherein withdrawing the ethane rich stream as a vapor side product from the divided wall fractionation column lowers a refrigeration requirement for the divided wall fractionation column and reduces energy for vaporization in the ethane steam cracker, the apparatus further comprising: a depropanizer column configured to input the propane rich stream from the divided wall fractionation column, and a propane dehydrogenation unit configured to input an output product from the depropanizer column and output a stream of propylene.
11 . The apparatus of claim 10 wherein the top product stream output from the dividing wall fractionation column bypasses a cracking heater section of the ethylene steam cracker.
12 . A process of producing ethylene and propylene from naphtha, the process comprising: passing a feed stream comprising hydrogen, methane, ethane, and propane and residual C4+ from a naphtha-to-ethane-and-propane reactor to a dividing wall fractionation column, wherein the naphtha-to-ethane-and-propane processing unit further comprises a coldbox wherein the effluent passes through the coldbox upstream of the dividing wall fractionation column exchanging heat with incoming feed to dividing wall column.

Description

RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Patent Application No. 63/431,557 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, containing ethane, propane and also hydrogen, methane, and some C4+ material, of a naphtha to ethane and propane reactor section. More particularly, the invention relates to separating ethane and propane from the effluent using a dividing wall fractionation column. 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 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 The disclosure is directed to a process of producing light paraffins from naphtha from a stream comprising hydrogen, methane, ethane, propane and C4+ produced in a reactor section of a naphtha-to-ethane-and-propane (NEP) processing unit. The process includes passing a NEP reactor effluent stream comprising hydrogen, methane, ethane, and propane and residual C4+ to the NEP fractionation section for efficiently separating the effluent stream into components. The NEP fractionation section comprises, among other equipment, coldbox (cryogenic) exchangers, and dividing wall fractionation column. 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 unit and the ethane steam cracker having a common source of refrigeration fluid for the coldbox heat exchangers; FIG. 4 is a schematic of a naphtha-to-ethane-and-propane processing unit's dividing wall column and the associated coldbox exchangers are shown in detail; FIG. 5 is a schematic of a common coldbox and a mixed refrigeration system (MR) provided to integrate a naphtha-to-ethane-and-propane processing unit with an ethane steam cracker. DETAILED DESCRIPTION The term “downstream” means that at least a portion of fluid flowing to the subject in downstream may operatively flow from the object with which it fluidly communicates. The term “upstream” means that at least a portion of the fluid flowing from the subject in upstream may operatively flow to the object with which it fluidly communicates. The term “direct” means that fluid flow from the upstream component enters the downstream component without passing through any other intervening vessel. The term “indirect” means that fluid flow from the upstream component enters the downstream component after passing through an intervening vessel. The term “bypass” means that the object is out of downstream communication with a bypassing subject at least to the extent of bypassing. As used herein, the term “rich” is defined as at least 50 mol %. As mentioned above, a process and method for separating effluent from a naphtha-to-ethane-and-propane (NEP) reactor section, for which the feed is naphtha, into ethane, propane, and hydrogen/methane rich streams is described. With these general principles in mind, one or more embodiments of the present invention will be described with the understanding that the following description is not intended to be limiting. This disclosure is directed to a process of producing light paraffins from naphtha and a stream comprising hydrogen, methane, and ethane produced in a reactor section of a naphtha-to-ethane-and-propane processing unit, including a process of separating hydrogen, methane, ethane, propane and C4 hydrocarbons in a deethanizer column configured as a dividing wall column (DWC), which is part of a fractionation section of a naphtha-to-ethane-and-propane (NEP) processing unit. The ethane and