WO2016133876A1

WO2016133876A1 - Divided wall column configuration for feedstock fractionation in styrene recovery process

Info

Publication number: WO2016133876A1
Application number: PCT/US2016/018023
Authority: WO
Inventors: Manish BHARGAVA; Sachin Joshi; Cole Nelson
Original assignee: Gtc Technology Us Llc
Priority date: 2015-02-16
Filing date: 2016-02-16
Publication date: 2016-08-25

Abstract

A method of fractionating a feedstock with a distillation column that includes an L-shaped dividing wall includes feeding a feedstock into the distillation column. The L-shaped dividing wall includes an upper portion extending vertically within the distillation column and a bottom portion extending away from the upper portion towards a feed side of the distillation column. The method also includes manipulating, with a side reboiler, a vapor split within the distillation column. An inlet of the side reboiler is coupled to the distillation column at a position below the bottom portion of the L-shaped dividing wall and an outlet of the side reboiler is coupled to the distillation column at a position above the bottom portion of the L-shaped dividing wall.

Description

DIVIDED WALL COLUMN CONFIGURATION FOR FEEDSTOCK

FRACTIONATION IN STYRENE RECOVERY PROCESS

CROSS REFERENCES TO RELATED APPLICATIONS

[0001] This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 62/116,828, filed February 16, 2015, which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

[0002] There is a growing demand for polystyrene type products, and hence a growing demand for styrene as a starting material or precursor of such products. Extractive distillation techniques, together with careful selection, arrangement, and combination of pre-processing and post-processing steps in connection with these extractive distillation techniques, separate and recover the styrene, which may be found in the intermediate streams of the refining process. The pre-processing steps include splitting of feedstock prior to the extractive distillation steps to concentrate a Cs fraction. [0003] Prior art divided wall column configuration for feedstock fractionation in a styrene recovery process includes a straight wall in the distillation column. The straight wall may start in the middle of the distillation column with some number of trays above and below the dividing wall (e.g., see FIG. 1) or may start from the top of the distillation column and extend through a certain number of trays (e.g., see FIG. 2). These straight wall configurations result in a fixed vapor split within the distillation column. The vapors are generated by a reboiler at the bottom of the distillation column. The prior art divided wall column configurations also shift a utility requirement to a higher temperature level for the entire fractionation. The prior art divided wall configurations also include a variable liquid split from a top tray to either side of the divided wall column which can be manipulated to get the desired separation level. SUMMARY OF THE INVENTION

[0004] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. However, many modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims. [0005] A system for fractionating a feedstock includes a distillation column comprising an L- shaped dividing wall. The L-shaped dividing wall includes an upper portion extending vertically within the distillation column and a bottom portion extending away from the upper portion towards a feed side of the distillation column. [0006] In some embodiments, the system further includes a fluid tray disposed beneath the bottom portion of the L-shaped dividing wall.

[0007] In some embodiments, the system further includes a side reboiler that includes an inlet and an outlet, wherein the inlet is coupled to the distillation column to draw fluid from the fluid tray and the outlet is coupled to distillation column input vapors into the distillation column above the bottom portion of the L-shaped dividing wall.

[0008] In some embodiments, the system further includes an upper tray disposed above the upper portion of the L-shaped dividing wall.

[0009] In some embodiments, the system further includes at least one opening disposed in the upper tray on the feed side of the distillation column and at least one opening disposed in the upper tray on a product side of the distillation column.

[0010] In some embodiments, the system further includes a feedstock inlet disposed on the feed side of the distillation column and disposed at a height above the bottom portion of the L-shaped dividing wall.

[0011] A method of fractionating a feedstock with a distillation column that includes an L- shaped dividing wall includes feeding the feedstock into the distillation column. The L- shaped dividing wall includes an upper portion extending vertically within the distillation column and a bottom portion extending away from the upper portion towards a feed side of the distillation column. The method also includes manipulating, with a side reboiler, a vapor split within the distillation column. An inlet of the side reboiler is coupled to the distillation at a position below the bottom portion of the L-shaped dividing wall and an outlet of the side reboiler is coupled to the distillation column at a position above the bottom portion of the L- shaped dividing wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

[0013] FIG. 1 is a diagrammatic illustration of a prior art system with a middle dividing wall column configuration;

[0014] FIG. 2 is diagrammatic illustration of a prior art system with a top dividing wall column configuration; and [0015] FIG. 3 is a diagrammatic illustration of a system comprising an L-shaped dividing wall configuration.

DETAILED DESCRIPTION

[0016] It is to be understood that the following disclosure provides different embodiment or examples for implementing different features of various aspects. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various aspects and/or configurations discussed. [0017] In general, embodiments of the present invention are directed towards processes and apparatuses for concentrating a Cs fraction in a feedstock using a divided wall distillation column prior to the extractive distillation in a styrene recovery process. The feedstock may include various hydrocarbons that include styrene content, such as, for example, pyrolysis gasoline, as well as those initially containing little or no styrene, but containing a related material, such as, for example, ethylbenzene. An exemplary feedstock is a Cs reformate fraction.

[0018] Refer now to FIG. 3, which is a diagrammatic illustration of a system 10 comprising a distillation column 11 with an L-shaped dividing wall configuration. The distillation column 11 is configured to receive a feedstock 14 at an inlet 15. In a typical embodiment, the feedstock 14 is fractionated in the distillation column 11 to obtain: a C7- fraction 16 from a top of the distillation column 11; a core C8 fraction 18 from the middle of the distillation column 11; and a C9+ fraction 20 as bottom of the distillation column 11. In other embodiments, the feedstock 14 could be fractionated to recover different components of the feedstock 14.

[0019] The distillation column 11 includes an L-shaped dividing wall 22. In some embodiments, the L-shaped dividing wall 22 extends from a tray 30 in a top portion of the distillation column 11 to below a feed entry tray. A bottom portion 23 of the L-shaped dividing wall 22 extends laterally away from an upper portion 24 of the L-shaped diving wall 22. The orientation of bottom portion 23 relative to the upper portion 24 results in the "L- shape" of the L-shaped dividing wall 22. In some embodiments, the bottom portion 23, when viewed from the side as shown in FIG. 3, is oriented generally perpendicular to the upper portion 24 and extends towards a feed side 12 of the distillation column 11. In a typical embodiment, the bottom portion 23 does not include holes, which restricts vapor flow and results in only a liquid flow to a tray 25 below the bottom portion 23. Similarly, a portion of tray 25 on the feed side 12 of the dividing wall 22 does not include holes so that fluid may collect in the tray 25. A portion of tray 25 on the product side 13 of the dividing wall 22 includes holes that allow vapors to pass from the main reboiler 29 to trays above the tray 25 on the product side 13 of the dividing wall 22. [0020] The distillation column 11 also includes a side reboiler 26. The side reboiler 26 includes an inlet 27 that is coupled to the distillation column 11 to accept liquids from the tray 25 and an outlet 28 that returns vapors to the distillation column 11 to an area above the bottom portion 23 on the feed side 12 of the distillation column 11. The side reboiler 26 may utilize various feeds (e.g., steam, hydrocarbon feed, waste heat, etc.) as sources of heat. For example, a recycled feed from another refining process may be directed to the side reboiler 26 to remove heat from the recycled feed and transferred to the liquids from the tray 25 to vaporize them. In other embodiments, steam may be fed into the side reboiler 26.

[0021] Vapors from a main reboiler 29 at the bottom of the distillation column 11 only pass to a product side 13 of the distillation column 11. The main reboiler 29 may utilize various feeds (e.g., steam, hydrocarbon feed, waste heat, etc.) as sources of heat. The presence of the side reboiler 26 proximal to the bottom portion 23 and the main reboiler 29 at bottom of the distillation column 11 enables manipulation of the vapor split from the tray 25 below the L- shaped dividing wall 22 to either side of the L-shaped dividing wall 22. For example, the vapor split on the feed side 12 may be manipulated by changing the flow of feed through the side reboiler 26 and/or the temperature of the side reboiler 26. Similarly, the vapor split on the product side 13 may be manipulated by changing the flow of feed through the main reboiler 29 and/or the temperature of the main reboiler 29. In some embodiments, the side reboiler 26 uses low level utility as it selectively vaporizes light hydrocarbons present in the feedstock 14. A liquid split from the tray 30 at the top of the L-shaped dividing wall 22 to either side of the L-shaped dividing wall 22 is fixed by a mechanical configuration of the tray 30 on each side of the L-shaped dividing wall 22. Though the flow is fixed, it can be tuned by altering the shape of the tray 30 to obtain the desired flow characteristics. For example, as shown in FIG. 3, the tray 30 includes openings 31.

[0022] The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the aspects introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term "comprising" within the claims is intended to mean "including at least" such that the recited listing of elements in a claim are an open group. The terms "a," "an" and other singular terms are intended to include the plural forms thereof unless specifically excluded.

Claims

CLAIMS What is claimed is:

1. A system for fractionating a feedstock, the system comprising: a distillation column comprising an L-shaped dividing wall, wherein the L-shaped dividing wall comprises: an upper portion extending vertically within the distillation column; and a bottom portion extending away from the upper portion towards a feed side of the distillation column.

2. The system of claim 1, further comprising a fluid tray disposed beneath the bottom portion of the L-shaped dividing wall.

3. The system of claim 2, further comprising a side reboiler comprising an inlet and an outlet, wherein the inlet is coupled to the distillation column to draw fluid from the fluid tray and the outlet is coupled to distillation column input vapors into the distillation column above the bottom portion of the L-shaped dividing wall.

4. The system of claim 1, further comprising an upper tray disposed above the upper portion of the L-shaped dividing wall.

5. The system of claim 4, further comprising at least one opening disposed in the upper tray on the feed side of the distillation column and at least one opening disposed in the upper tray on a product side of the distillation column.

6. The system of claim 1, further comprising a feedstock inlet disposed on the feed side of the distillation column, and disposed at a height above the bottom portion of the L-shaped dividing wall.

7. A method of fractionating a feedstock with a distillation column that includes an reshaped dividing wall, the method comprising: feeding the feedstock into the distillation column, the distillation column comprising: the L-shaped dividing wall comprising: an upper portion extending vertically within the distillation column; and a bottom portion extending away from the upper portion towards a feed side of the distillation column; manipulating, with a side reboiler, a vapor split within the distillation column, wherein an inlet of the side reboiler is coupled to the distillation column at a position below the bottom portion and an outlet of the side reboiler is coupled to the distillation column at a position above the bottom portion.

8. The method of claim 7, wherein the distillation column further comprises a fluid tray disposed beneath the bottom portion of the L-shaped dividing wall.

9. The method of claim 8, wherein the manipulating further comprises drawing, via the inlet of the side reboiler, a fluid from the fluid tray and vaporizing the fluid in the side reboiler.

10. The method of claim 7, wherein the distillation column further comprises an upper tray disposed above the upper portion of the L-shaped dividing wall.

11. The method of claim 10, wherein the upper tray further comprises at least one opening disposed in the upper tray on the feed side of the distillation column and at least one opening disposed in the upper tray on a product side of the distillation column.

12. The method of claim 7, further comprising a feedstock inlet disposed on the feed side of the distillation column and disposed at a height above the bottom portion of the L-shaped dividing wall.

13. The method of claim 7, wherein the manipulating further comprises reboiling, via a main reboiler, a portion of a bottoms feed from the distillation column.