WO2019073455A1

WO2019073455A1 - A distillation column and a process for preparing a composition therefrom

Info

Publication number: WO2019073455A1
Application number: PCT/IB2018/057958
Authority: WO
Inventors: Kaushal Chandulal PUJARA; Ashvin Jivrajbhai SONANI
Original assignee: Reliance Industries Limited
Priority date: 2017-10-13
Filing date: 2018-10-15
Publication date: 2019-04-18

Abstract

The present disclosure relates to a distillation column and a process for preparing a composition therefrom. The composition obtained from the distillation column has reduced gum content and colour and can be used as wash oil for compressors of refinery cracker plants. The process involves drawing vapor from the column bottom sump followed by condensing the vapor to obtain composition having reduced gum content and colour. The present disclosure also relates to taking a side draw from reboiler outlet line. This avoids installation of new distillation column.

Description

A DISTILLATION COLUMN AND A PROCESS FOR PREPARING A COMPOSITION THEREFROM

FIELD

The present disclosure relates to a distillation column and a process for preparing a composition therefrom.

DEFINITIONS

As used in the present disclosure, the following terms are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicates otherwise.

Gum: The term "gum" refers to undesirable oxidation products formed in the heavy aromatics stream.

Bottom Sump: The term "bottom sump" refers to a low space in the distillation column where unwanted chemicals are collected during the operation/running of a process.

Vapor Product: Vapor obtained from a feed/product, such as hydrocarbon, organic, inorganic, paraffin, olefin, naphthene, aromatic, and non aromatic compounds.

Heavies: The term "heavies" refer to compounds having higher molecular weight and/or the higher boiling point as compared to the corresponding lighter fraction.

Improved purity: The term "improved purity" implies that the product produced by the process of the present disclosure is comparatively more pure/has less impurity with respect to when using the conventional processes and apparatus.

Reduced gum content: The term "reduced gum content" implies that the product produced by the process of the present disclosure has a lower amount of gum content as compared to a product obtained using the conventional processes and apparatus. Also, the product of the present disclosure has lower amount of gum content as compared to the gum content in the feed.

Reduced color: The term "reduced color" implies that the product produced by the process of the present disclosure has less color as compared to a product using the conventional processes and apparatus. Also, the product of the present disclosure has less color as compared to the gum content in the feed.

BACKGROUND

The background information herein below relates to the present disclosure but is not necessarily prior art.

Refinery cracker plants require wash oil for the compressors to avoid polymerization in the compressors. Heavy aromatics stream, a bottom product from the heavy aromatics distillation column, is conventionally used as wash oil in the refinery cracker plants. However, the heavy aromatics stream contains gum content, and colour, which needs to be removed, before being used as the wash oil. Typically, the heavy aromatics stream is subjected to fractional distillation in a separate distillation column to fractionate the heavy aromatics stream so as to reduce the gum and colour contributing components of the heavy aromatics stream. However, installation of the separate distillation column results in a significant increase in the capital expenditure. Therefore, there is felt a need to provide a distillation column and a process for preparing a composition therefrom that mitigates the drawbacks mentioned hereinabove.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows: An object of the present disclosure is to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

Another object of the present disclosure is to provide a distillation column to provide desired quality product.

Another object of the present disclosure is to provide a simple and cost effective process for making a composition having reduced gum content and colour for use as wash oil for compressors of refinery cracker plants.

Still another object of the present disclosure is to provide a composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants.

Yet another object of the present disclosure is to use Heavy Aromatics column bottom stream as wash oil for cracker compressors.

Another object of the present disclosure is to take side draw of vapor from Heavy Aromatics column bottom sump for removal of color and gum content. This avoids installation of new distillation column.

Still another object of the present disclosure is to take side draw from reboiler outlet line. This avoids installation of new distillation column.

Yet another object of the present disclosure is to take vapor side draw from distillation column bottom sump vapor space for purity improvement, color removal, gum content reduction, heavies removal from distillation column bottom product stream.

Still another object of the present disclosure is to reduce distillation column height by taking side draw from distillation column bottom sump vapor space. Yet another object of the present disclosure is to take side draw from distillation column bottom sump for desired purity product withdrawal.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure relates to a distillation column, which has a vapor side draw from distillation column bottom sump, for getting a vapor product having a predetermined quality which in turn is capable of being condensed and cooled. The present disclosure relates to a process for making a composition having reduced gum content and colour. The composition is used as a wash oil for compressors of refinery cracker plants. The process comprises the steps of drawing vapor from the distillation column bottom sump, and condensing the drawn vapor to obtain the composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants. In one embodiment, the vapor is drawn from the Reboiler outlet stream of the distillation column. The composition having reduced gum content and colour can be used as a wash oil for compressors of refinery cracker plants to prevent polymerization. Typically, the composition comprises C₁₀ aromatics and above. The present disclosure also relates to the innovation of having a sidecut draw from distillation column bottom sump for taking desired quality product from distillation column. This avoids installation of new distillation column for producing desired quality product from distillation column bottom stream.

The present disclosure further relates to the innovation of having a side draw from reboiler outlet line and separating vapor/liquid from it by using a separator, to get desired quality product as a vapor phase, which in turn can be condensed and cooled. BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING

The present disclosure will now be described with the help of the accompanying drawing, in which:

Figure 1 illustrates a illustrates a schematic representation of a distillation column, having a vapor side cut draw from distillation column bottom sump and a process for preparing a composition having reduced gum content and colour for use as wash oil for compressors of refinery cracker plants, by taking a side draw from distillation column bottom sump; and

Figure 2 illustrates a schematic representation of a distillation column and a process for preparing a composition having reduced gum content and colour for use as wash oil for compressors of refinery cracker plants, by taking a side draw from reboiler outlet line.

DETAILED DESCRIPTION

Embodiments, of the present disclosure, will now be described with reference to the accompanying drawing.

Embodiments are provided so as to thoroughly and fully convey the scope of the present disclosure to the person skilled in the art. Numerous details, are set forth, relating to specific components, and methods, to provide a complete understanding of embodiments of the present disclosure. It will be apparent to the person skilled in the art that the details provided in the embodiments should not be construed to limit the scope of the present disclosure. In some embodiments, well-known processes, well- known apparatus structures, and well-known techniques are not described in detail.

The terminology used, in the present disclosure, is only for the purpose of explaining a particular embodiment and such terminology shall not be considered to limit the scope of the present disclosure. As used in the present disclosure, the forms "a," "an," and "the" may be intended to include the plural forms as well, unless the context clearly suggests otherwise. The terms "comprises," "comprising," "including," and "having," are open ended transitional phrases and therefore specify the presence of stated features, integers, steps, operations, elements, modules, units and/or components, but do not forbid the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The particular order of steps disclosed in the method and process of the present disclosure is not to be construed as necessarily requiring their performance as described or illustrated. It is also to be understood that additional or alternative steps may be employed.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed elements.

The terms first, second, third, etc., should not be construed to limit the scope of the present disclosure as the aforementioned terms may be only used to distinguish one element, component, region, layer or section from another component, region, layer or section. Terms such as first, second, third etc., when used herein do not imply a specific sequence or order unless clearly suggested by the present disclosure.

Refinery cracker plants require wash oil for the compressors to avoid polymerization in the compressors. Heavy aromatics stream, a bottom product from the heavy aromatics distillation column, is conventionally used as wash oil in the refinery cracker plants. However, the heavy aromatics stream contains gum content, and colour, which needs to be removed before being used as the wash oil. The conventional method includes subjecting the heavy aromatics stream to fractional distillation in a separate distillation column to fractionate the heavy aromatics stream so as to reduce the gum and colour contributing components of the heavy aromatics stream. However, installation of the separate distillation column results in a significant increase in the capital expenditure. The present disclosure envisages a simple and cost effective process for making a composition having reduced gum content, and colour. The composition can be used as a wash oil for compressors of refinery cracker plants.

In an aspect the present disclosure relates to a distillation column, which has a vapor side draw from distillation column bottom sump, for getting a vapor product having a pre-determined quality, which in turn is capable of being condensed and cooled.

In another aspect of the present disclosure, there is provided a simple and cost effective process for making a composition having reduced gum content and colour for use as a wash oil for compressors of refinery crackers plants, as illustrated in Figure- 1. Figure- 1 illustrates a process for making a composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants, by drawing vapor from the Heavy Aromatics distillation column bottom sump. The simple and cost effective process comprises drawing vapor from the distillation column bottom sump. The vapor drawn is then condensed to obtain the composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants. This avoids installation of new distillation column for removal of color and gum content for Heavy aromatics distillation column bottom stream.

In one embodiment, the vapor is drawn from the Reboiler outlet stream of the distillation column.

The wash oil comprises 0 % to 2 % of C9 aromatics, 20 % to 40 % of C₁₀ aromatics, and 60 % to 85 % of Cn aromatics, an initial boiling point in the range of 170 °C to 220 °C, and a final boiling point in the range of 295 °C to 365 °C.

In an embodiment of the present disclosure, the Heavy Aromatics column bottom stream is used as wash oil for cracker compressors. A side cut draw of vapor from Heavy Aromatics column bottom sump is taken for removal of color and gum content. This avoids the installation of new distillation column.

In another embodiment, Heavy aromatics column bottom stream is used as wash oil for cracker compressors. As illustrated in Figure-2, side draw is taken from Reboiler outlet line and it is separated in separator and wash oil having a pre-determined quality is obtained as a vapor phase from separator. This avoids installation of new distillation column for producing desired quality wash oil from heavy aromatics column bottom stream.

For purity improvement, color removal, gum content reduction, and heavies removal from distillation column bottom product stream, vapor sidedraw can be taken from distillation column bottom sump vapor space. The present disclosure makes it possible to reduce distillation column height by taking side draw from distillation column bottom sump vapor space. It is possible to take the side draw from the distillation column bottom sump for desired purity product withdrawal. Typically, the composition comprises C₁₀ aromatics and above.

Though the gum content and the colour of the composition is reduced, there is no significant impact on stream quality, boiling range or chemical structure, and hence retains its compatibility for use as wash oil. The process of the present disclosure avoids additional fractionation or purification equipment to remove the gum content and colour, as the vapor is drawn from the existing fraction process itself and thereby reduces the additional expenditure of treating the heavy aromatics stream downstream in a separate fractional distillation column. Taking the product cut from the distillation column by the condensing vapor of bottom sump (i.e. vapour below the column bottom tray), avoids modification to trays for taking new product and thus saves on cost and shutdown time. It avoids removal of trays in case of existing column and reduces column height in new design. The process of the present disclosure is capable of taking vapor from Reboiler outlet stream. The present disclosure also provides a distillation column apparatus for distilling feed, having a bottom sump, trays lined within the distillation column, characterized in that a vapor side draw is taken from the bottom sump or bottom sump vapor space for drawing vapor for obtaining a product having a pre-determined quality which in turn is capable of being condensed and cooled.

In an embodiment, the wash oil produced by the process of the present disclosure comprises 0 % to 2 % of C9 aromatics, 20 % to 40 % of C₁₀ aromatics, and 60 % to 85 % of C11 aromatics. In another embodiment, the wash oil has an initial boiling point in the range of 170 °C to 220 °C, and a final boiling point in the range of 295 °C to 365 °C.

The wash oil having reduced gum content and colour can be used as wash oil for compressors of refinery cracker plants to prevent polymerization.

The foregoing description of the embodiments has been provided for purposes of illustration and not intended to limit the scope of the present disclosure. Individual components of a particular embodiment are generally not limited to that particular embodiment, but, are interchangeable. Such variations are not to be regarded as a departure from the present disclosure, and all such modifications are considered to be within the scope of the present disclosure.

The present disclosure is further described in light of the following experiments which are set forth for illustration purpose only and not to be construed for limiting the scope of the disclosure. The following experiments can be scaled up to industrial/commercial scale and the results obtained can be extrapolated to industrial scale.

Experimental details Experiment- 1: Production of wash oil having reduced gum content and colour in accordance with the present disclosure The wash oil was produced using a distillation system as illustrated in Figure- 1. The Heavy aromatics column has a total of 94 trays. Wash oil was produced from Heavy Aromatics column (1) as illustrated in Figure- 1. The feed (3) comprising Non aromatics (0.11 %), OX (1.02 %),C₉A (73.31 %) , Ci₀A (18.84 %) and CnA (6.72 % ) was introduced to Heavy Aromatics column. The partial vapor/liquid mixture produced in the reboiler (4) was re-introduced into the bottom sump of the distillation column via a conduit (x) and the vapor from distillation column bottom sump (2) was drawn via conduit (5) and it was condensed and cooled. The vapor was passed through the heat exchangers (6a, 6b) for cooling. Operating parameters and laboratory analysis of products is shown in Table- 1 and Table-2.

The gum content and the color of the wash oil obtained by the process of the present disclosure were determinedand it was observed that the gum content was reduced from 854 gm/lOOml to 0.120 gm/ 100ml, and the color was reduced from 7.5 rating to 2 and even lesser. The color analysis of the wash oil was determined using the ASTM D 1500 method.

Experiment-2: Production of wash oil having reduced gum content and colour in accordance with the present disclosure

Similar to experiment- 1 , the wash oil was produced using a distillation system as illustrated in Figure-2. The Heavy aromatics column has a total of 94 trays. Wash oil was produced from Heavy Aromatics column (1) as illustrated in Figure-2.The feed (3) comprising Non aromatics, OX, C₉A, C₁₀A and CnA was introduced to Heavy Aromatics column. The partial vapor/liquid mixture produced in the reboiler (4) was re-introduced into the bottom sump of the distillation column via a conduit (x). The vapor from the reboiler outlet stream was drawn as a sidedraw via a conduit (7) and separated in a separator (8) to obtain wash oil (8a) having reduced gum content and colour and the heavies (8b). Table-1

Table-2

It is seen from the above tables that the wash oil of the present disclosure has less than 1 % of C9 aromatics, whereas the wash oil contains 32.7 % of C₁₀ aromatics and 67 % C₁₁ aromatics, demostrating the suitability of the wash oil for use in compresors of refinery cracker plants. Further, the wash oil has an initial boiling point of to 198 °C, and a final boiling point of 308.8 °C.

TECHNICAL ADVANCEMENTS

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of: a simple and cost effective process to make a composition having reduced gum content and colour for use as a wash oil for compressors of cracker plants; a composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants to avoid polymerization; reducing additional expenditure of treating the heavy aromatics stream downstream in a separate fractional distillation column; avoiding modification to trays for taking new product by taking side draw from distillation column bottom sump and thus saving on cost and shutdown time; to take sidedraw from distillation column bottom sump for getting desired quality product; and to take sidedraw from a reboiler outlet line and sending it to a separator for getting desired quality product as vapor, which in turn can be condensed and cooled. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. The use of the expression "at least" or "at least one" suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the invention to achieve one or more of the desired objects or results. While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Variations or modifications to the formulation of this invention, within the scope of the invention, may occur to those skilled in the art upon reviewing the disclosure herein. Such variations or modifications are well within the spirit of this invention.

The numerical values given for various physical parameters, dimensions and quantities are only approximate values and it is envisaged that values higher or lower than the numerical value assigned to the physical parameters, dimensions and quantities fall within the scope of the invention unless there is a statement in the specification to the contrary.

While considerable emphasis has been placed herein on the specific features of the preferred embodiment, it will be appreciated that many additional features can be added and that many changes can be made in the preferred embodiment without departing from the principles of the disclosure. These and other changes in the preferred embodiment of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

A distillation column, which has a vapor side draw from distillation column bottom sump, for getting a vapor product having a pre-determined quality which in turn is capable of being condensed and cooled.

The distillation column as claimed in claim 1, wherein said vapor product is wash oil comprising 0 % to 2 % of C9 aromatics, 20 % to 40 % of C₁₀ aromatics, and 60 % to 85 % of Cn aromatics, having an initial boiling point in the range of 170 °C to 220 °C, and a final boiling point in the range of 295 °C to 365 °C.

Use of said vapor product as claimed in claim 1 as wash oil for cracker compressors.

A process of taking sidedraw from any distillation column bottom sump and/or bottom sump vapor space, for producing desired quality product, for purity improvement, colour removal, gum content reduction, and heavies removal.

A method for height reduction, of any distillation column, by taking sidedraw from distillation column bottom sump, instead of taking sidedraw from in between the trays (in between tray spacing).

A distillation column apparatus for distilling a feed, having a bottom sump, trays lined within said distillation column, characterized in that a vapor side draw is taken from said bottom sump or bottom sump vapor space for drawing vapor for obtaining a product having a pre-determined quality which in turn is capable of being condensed and cooled.

A process for making a composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants, said process comprising the following steps: drawing vapor from the heavy aromatics distillation column bottom sump; and condensing said vapor to obtain said composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants.

A process for making a composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants, said process comprising the following steps: drawing sidedraw from the heavy aromatics distillation column reboiler outlet stream; and separating said sidedraw, in a separator, to get desired quality product as vapor from separator overhead, which obtains said composition having reduced gum content and colour for use as a wash oil for compressors of refinery cracker plants.

9. The process as claimed in claim 7 and claim 8, wherein said composition having reduced gum content and colour is used as wash oil for compressors of refinery cracker plants to prevent polymerization.

10. The process as claimed in claim 7 and claim 8, wherein said composition comprises C₁₀ aromatics and above.